Login| Sign Up| Help| Contact|

Patent Searching and Data

Document Type and Number:
WIPO Patent Application WO/1992/005567
Kind Code:
Electroset materials comprise castable compositions that can be influenced as to shape and cure time by application of an electric field. Apparatus and processes for using electroset materials are also disclosed. Electroset compositions are characterized in that under the influence of an electrostatic field, the cure time of the composition is significantly shorter. Electroset materials have electrically programmable electric and mechanical properties. Such properties include density, compressibility, hardness, adhesion and electric resistance. Furthermore, electroset compositions can be used to form composite articles. Electrically conductive substrates are formed that define the shape of products of electroset materials. Electroset materials are placed between the substrates and the substrates are energized by high voltage. Electroset fluid between electrically charged conductive substrates is held in position by the Winslow effect whereas electroset fluid that is not between electrically charged substrates is not so affected. Such fluid that is not held electrically in position is removed. That electroset fluid that is electrically held in position permanently solidifies.

Reitz, Ronald Patterson (7008 Barton Road, Hyattsville, MD, 20784, US)
Application Number:
Publication Date:
April 02, 1992
Filing Date:
August 30, 1991
Export Citation:
Click for automatic bibliography generation   Help
Reitz, Ronald Patterson (7008 Barton Road, Hyattsville, MD, 20784, US)
International Classes:
B29C35/12; C08G85/00; (IPC1-7): B29B13/00; H01B3/24; H05B1/00
Foreign References:
Download PDF:
1. An electroset composition comprising a phase changing ve¬ hicle and electrically polarizable aggregate, said com¬ position characterized by susceptibility of said com position to influence by an electric field and also being characterized by the second Reitz effect.
2. A process for accelerating fluid to solid phase change of an electroset composition, said process comprising: positioning an electroset composition between at least two electrically conductive surfaces, said electroset composition comprising a dielectric phase changing vehi¬ cle and a plurality of electrically polarizable particles wherein the curing of said electroset composition is sus¬ ceptible to influence by an electric field; and, electrically charging said conductive surfaces.
3. An article of manufacture made by the process of accel¬ erating the permanent fluid to solid phase change of el¬ ectroset compositions, said process comprising: position¬ ing an electroset composition between at least two elec trically conductive surfaces, said electroset composition comprising a dielectric phase changing vehicle and a plurality of electrically polarizable particles wherein the cure of said electroset composition is susceptible to influence by an electric field; and, electrically charg ing said conductive surfaces.
4. An article as defined in claim 3 further comprising: at least one substrate; and an electroset composition joined with said substrate by the process of electroset¬ ting said composition while said substrate is embodied in said electroset composition, said process of electro¬ setting being defined as the positioning of an electroset composition between at least two electrically conductive surfaces and electrically charging said surfaces.
5. An electroset composition as defined in claim 1 further comprising: means for controllably varying the physical properties of said composition, said means responsive to an electric field.
6. A process for making an article having voids embedded therein, comprising: providing an electroset composition having inclusions dispersed therein, said inclusions capable of liberating gas or vapor upon exposure of said composition to an electric field; placing said electro set composition in a mold, said mold adapted to be ener¬ gized by an electric field; applying an electric field from an electrical source to said composition, said source adapted to control the energy imparted to said composition at a predetermined value.
7. An article as defined in claim 3 wherein said article comprises a cured electroset material having voids embed¬ ded therein, characterized in that material properties in a' first area of said material differ from the material properties of said material in a second area.
8. A process for making an object, comprising: forming a conductive image, said image defining a first electrode; embodying said image in an uncured electroset material; applying an electric potential between said image and a second electrode wherein said electric potential causes said material to solidify between said electrode by the Winslow effect; removing said uncured material not under the influence of the Winslow effect; and, maintaining said potential until said electroset material permanent¬ ly solidifies.
9. An apparatus for molding an electroset composition into shaped articles, comprising: first and second surfaces, each said surface having substantially symmetrically op¬ posite electrically conductive and nonconductive por¬ tions; means for retaining a portion of uncured electro set composition on one said surface; means for applying an electric field between said conductive portions of said first and second surfaces.
10. An electroset composition as claimed in claim 5 wherein said means for varying is a gas liberating composition, said gas liberating composition susceptible to activa¬ tion by an electric field during curing.
11. An electroset composition as defined in claim 5 wherein said variable physical property is density.
12. An electroset composition as claimed in claim 5 wherein said variable physical property is hardness.
13. An electroset composition as claimed in claim 5 wherein said variable physical property is compressibility.
14. 5 14. An electroset composition as claimed in claim 5 wherein said variable physical property is electric resistance. 15. A process for making articles, comprising: positioning an electroset composition between at least two electric¬ ally conductive surfaces, said electroset composition 10 comprising a dielectric phase changing vehicle and a plurality of electrically polarizable particles wherein the curing of said electroset composition is susceptible to influence by an electric field; and, electrically charging said conductive surfaces. 15 16. A process as claimed in claim 15 wherein said electric field is an electrostatic field.
15. 17 A process as claimed in claim 16 wherein the energy of said electrostatic field is controlled by independently controlling the applied voltage at a predetermined max 20 mum and the applied current at a predetermined maximum.
16. 18 A composite article, comprising: first and second elec¬ trically conductive surfaces; cured electroset material disposed between and adhering to said first and second surfaces, said material cured by exposing an uncured 25 electroset material to an electric field wherein said field is applied between said first and second sur¬ faces.
17. 19 A process for making a composite article, comprising: interposing an uncured electroset composition between 30 first and second conductive surfaces; applying elec¬ trical potential and current between said first and second surfaces causing said material to solidify under the influence of the Winslow effect; and, limiting said potential and current at predetermined maximums until 35 said material permanently solidifies.
18. 20 A process for predetermining a physical property of a cured electroset article, comprising: providing an un¬ cured electroset material having an electrically acti vated blowing agent dispersed therein; curing said material in an electric field sufficient to activate said blowing agent.
19. 21 A process as claimed in claim 20 wherein said physical property is density.
20. 22 A process as claimed in claim 20 wherein said physical property is compressibility.
21. 23 An article as claimed in claim 7 wherein said article further comprises a shoe sole.
22. 24 An article as claimed in claim 4 wherein a plurality of substrates are embodied in said composition.
23. 25 An article as claimed in claim 4 wherein said substrate is electrically conductive.
24. 26 An article as claimed in claim 25 wherein said sub¬ strate is used as an electrode to electrify said elec troset composition.
25. 27 An article as claimed in claim 4 wherein said substrate is a fabric.
26. 28 An article as claimed in claim 27 wherein said fabric is an open weave fabric.
27. An article as claimed in claim 27 wherein said fabric is a closed weave fabric.
28. A process as claimed in claim 8 wherein said second electrode is a second conductive image embodied in said uncured electroset material.
29. A process as claimed in claim 8 wherein a plurality of conductive images are embodied in said uncured electroset material.
30. A process as claimed in claim 31 wherein said electric potential is applied between adjacent images.
31. A process as claimed in claim 8 wherein said conductive image is formed by a computer imaging device.
32. A process as claimed in claim 33 wherein said imaging device is a pen plotter.
33. A process as claimed in claim 33 wherein said imaging device is a laser printer.
34. An apparatus as claimed in claim 9 wherein said surfaces are formed by a computer imaging device.
Electroset Compositions, Articles and Processes BACKGROUND OF THE INVENTION FIELD OF THE INVENTION This invention relates to the field of compositions that change state from a flowable to a less flowable substance after application to an intended use and more particularly to compositions wherein it is desirable for this change of state to take place rapidly. BACKGROUND INFORMATION Electroviscous fluids refer to fluids which exhibit the property of increased viscosity when the fluid is subjected to an electric field. One phenomenon for electrically con¬ trolling fluid viscosity is known as the inslow effect. Herein the term Winslow effect refers to the phenomenon of electrically controlling the viscosity of a fluid comprising a suspension of finely divided electrically polarizable mat¬ ter in dielectric fluid by subjecting the fluid to an elec¬ tric field. Within this disclosure, the finely divided elec¬ trically polarizable matter is referred to as aggregate. Electroviscous fluids sometimes referred to as electrorheo- logical fluids are known in the prior art. Specifically, US Patent 4,687,589 teaches an electrorheological fluid com¬ prising a liquid continuous phase having dispersed therein at least one dispersed phase and which functions as such when at least the dispersed phase is substantially anhydrous preferably having functional capability when the fluid is substantially anhydrous.

Electroviscous fluids immersed in an electric field can support a shear stress because of the imposed field. Align- ent of the aggregate particles is energetically favored and mechanical energy is required to disalign them when a shear stress is applied to the energized fluid. The term energized fluid is used to define a fluid that is placed within an electric field. Energized electroviscous fluids exhibit similar physical properties to those properties found in solids. When an electric field is imposed upon the electroviscous fluid, the aggregate particles align them¬ selves along the electric lines of flux. Such alignment

gives the fluid periodicity in its structure. Electro¬ viscous fluids and aggregates for electroviscous fluids are taught in prior art in US Patents: 4,687,589; 3,427,247; 3,970,573; 3,984,339 4,502,973; 4,737,886, which are hereby incorporated by reference.

It is known that molded articles can be made by pouring a phase changing vehicle into a form, allowing the vehicle to set or cure and then removing the molded article from the mold. As used herein the term phase changing vehicle applies to any composition which changes state from a flow- able to a less flowable or solid state when such composi¬ tions cure or set in the normal course of their use. Num¬ erous commercially available compositions are available which exhibit such phase changing characteristics, examples of which are hereinafter disclosed. These include vehicles made from mixing multipart constituents which chemically react and vehicles having a contituent or a composition of constituents which reacts with its surroundings such as for example air. SUMMARY OF THE INVENTION

Aggregates that are suitable as aggregates in electrovis¬ cous fluids may be advantageously added to a phase changing vehicle. An electroviscous fluid is thus formed and is cap¬ able of being held in place by the Winslow effect during the phase change of the composition. Suprisingly, a composition comprising electroviscous fluid aggregate in a phase chang¬ ing vehicle will, when the composition is subjected to an electric field, set or cure much more rapidly than when it is not under the influence of an electric field. The pheno- monenon of such accelerated curing is referred to as the second Reitz effect.

Within this disclosure and the appended claims, the term electroset composition is used to relate to a composition which is susceptible to being shaped and cured by influence of an applied electric field. An electroset composition com¬ prises a phase changing vehicle and an electrically polariz¬ able aggregate. The term aggregate is used in the collective to include a multiplicity of polarizable particles. The com-

position is responsive to an applied electric field in that the field cooperates to hold the material in place while the material cures and to drastically accelerate the cure of the material, which is known as the second Reitz effect. Conse- quently it is expected that any of the aggregates disclosed in prior art as generally useful for making electroviscous fluids are also generally useful as aggregates for forming electroset compositions. Aggregates suitable for use in an electroset composition include those suitable for use as aggregates for electroviscous fluids.

Preferably the phase changing vehicle has good dielec¬ tric properties so that current flow in the electric field is kept to a minimum. It is not necessary, but is prefer¬ able that the density of the aggregate particles is matched to the density of the phase changing vehicle so that parti¬ cles are maintained uniformly suspended in the composition. It is an object of the invention to provide material com positions having a characteristic of accelerated curing or setting when the composition is under the influence of an electric field.

Another object of the invention is to provide a material which is held into a predetermined shape by an electric field while the material is curing, to provide a composition that is susceptible to accelerated curing by the application of an electric field, to provide a method and material for making molded articles and to provide a method of making molds or forms for making molded articles.

The invention has many advantages. While it is known that many materials may be initially fluid enough to be injected into a mold and permitted to harden into solids, many of these materials have slow cure times, that is, they do not harden rapidly into an identifiable and transportable form. However, an electroset composition can be cast into a mold and held in place and cured by application of an elec- trie field.

Another advantage is that the materials of the invention may have their cure rate electrically determined, acceler¬ ating the cure with a high potential, low energy consump-

tion electric field as opposed to accelerating the cure by conventional means such as heating the material and its surrounding area or adding additional catalyst.

The accelerated cure overcomes objections to conventional curing. For example, some moldable materials give off an offensive odor as they cure. Such a material is RTV silicone rubber which gives off a pungent acetic acid odor as it sets and cures. Accelerating the cure reduces the time that these odors can be offensive. Another advantage is that the electric field cure rate tends to be constant through the thickness of a shape.

Electroset materials, in accordance with the invention comprise, castable fluid compounds such as, for example, fluid polymers and ceramics that can be caused to set and cure electrically or wherein the set and cure rate is elec¬ trically controllable. The invention comprises electroset material that have electrically controllable end-product (i.e. cured) properties. These end-product properties in¬ clude physical, structural properties, electrical properties and the end-product shape. Physical characteristics such as for example density and specific gravity of certain electro¬ set compounds are susceptible to influence by an applied electric field during the cure time of the material. Two part epoxy compounds which cure by exothermic reaction are especially useful as the phase changing vehicle. The density of the cured material may be isotropic or else, anisotropic. Isotropic density means that the incremental density of the cured material remains about the same through out the volume of the cured material. Anisotropic density means that the incremental density of the cured material has readily obser¬ vable different values at different parts of the volume of the cured material. Herein the term electroshaped materials shall refer to the materials comprising any object deriving its shape, at least in part, from application of an elec- trie field to those materials. Thus, while it is cooling and undergoing a phase change from fluid to solid, a thermo¬ plastic material or other phase changing vehicle with elec- trorheological aggregate dispersed therein can derive its

shape by means of its immersion in an electric field.

Materials made in accordance with the present invention have controllably different physical end product properties- In this disclosure, the term "end product properties" re- fers to those properties of the material after the material has fully cured. These properties can be made relatively homogenous throughout the electroset material, or alterna¬ tively, anisotropic. The invention is useful and advantage¬ ous in the fabrication of polymeric articles. One such art- icle that may be advantageously manufactured using the com¬ positions and processes of the invention is shoe soles and portions of shoe soles. In accordance with the invention, shoe soles are fabricated with a great variety of chosen compressibilities. Applying an electric field to properly formulated electroset material shaped in the form of a shoe sole while the electroset material is undergoing phase change from fluid to solid, will accelerate the cure and will alter the compressibility of the resultant sole. Chang¬ ing the applied electric field alters the obtained compres- sibility of the sole. Also by selective application of field strength to various parts of the sole, the compressibility of some portions of the sole are made selectively different from other parts of the sole.

The invention provides an advantageous means of altering the properties of a fabricated shoe sole not found in the prior art. In prior art manufacturing of castable polymer shoe soles required that the formulation of the castable polymer be changed in order to change the shoe sole com¬ pressibility. Such a formulation change requires the time consuming and messy job of recalculating the proportions of polymer constituents to be mixed, measuring out and mixing the new proportions of polymer constituent materials, ing. Often, the newly reformulated polymer is incompatible with the constituents of the prior polymer. This requires that the prior polymer constituents and those of the new polymer to not be accidently mixed together. The materials of the present invention do not need to be reformulated in order to yield changes in the desired properties of the shoe

soles. Merely changing the applied electric field accom plishes this purpose.

It is standard practice in the scientific and engineer¬ ing communities to define materials by their characteristics of behavior or, alternatively by use, or yet alternatively by capabilities. In the same spirit, electroset compositions may be defined by their distinct characteristics. Electroset compositions are electrorheological fluids, are castable compositions and exhibit the second Reitz effect when elec- trically energized. The second Reitz effect is the acceler¬ ation of the set and cure rate of the castable electrorheo¬ logical composition by application of a voltage to said composition. Castable compositions are compositions that are initially fluid but over time become solid. The term "electrorheological fluid" refers to fluid compositions which solidify in the presence of an electric field, wherein said solidification is influenced by said electric field.

It is known to construct molds having a volume and an ex¬ terior form for retaining a liquid molding compound, to place liquid in these volumes, to allow the liquid to cure and then remove the form thereby revealing the article. To mold an article in this manner, it is first necessary to have a pattern for the article or a mold made with an in¬ terior conforming to the shape of the article. An elec- troset article can be formed by making a conductive mold having at least two electrode surfaces and that this mold can be used in conjunction with an electroset fluid to ac¬ celerate the production of articles.

It is known that images of objects to be manufactured are generated in computer systems and various views and sec¬ tions of the object are displayed on a screen or outputed on an output device such as a printer or plotter. It is advan¬ tageous if these views and sections are converted directly into an object by filling in the space between views and sections with a castable material and determining the shape features of the object without first fabricating a pattern in the shape of those features and without fabricating a cavity denoting the object features.

In accordance with the present invention, three dimen¬ sional objects are fabricated by preparing conductive images representing a plurality of views or sections of the object to be manufactured; filling the volume between adjacent images with uncured electroset material; applying electric potential between the images causing the material to solid¬ ify by the Winslow effect; removing that material that is not under the influence of the Winslow effect; and maintain¬ ing the voltage potential applied to the material that is solidified via the Winslow effect until the electroset mat¬ erial permanently solidifies. Such images may be prepared in the planar form by well known means such as cutting or stamping or alternatively by depositing images on a plural¬ ity of insulating substrates. The voltage potential may ei- ther be applied between adjacent images or in any manner that results in sufficient electric field strength to make the Winslow effect operative. In one embodiment of the in¬ vention, the images are generated by a properly programmed digital computer and transferred to a substrate by an output imaging device such as a pen plotter or, alternatively, a laser printer. The image is recorded on the substrate with electrically conductive ink in the case of the pen plotter or alternatively, by electrically conductive powder in the case of a laser printer. The ink or powder is made conduc- tive by a suitable additive such as, for example, graphite, aluminum coated hollow glass microspheres, or semiconductive materials such as silicon or germanium. The substrate may be any good insulating material compatible with the material to be electroset such as for example, epoxy, polyurethane or silicone rubber. It is not necessary that the pattern of conductivity that defines the image be of 100 percent den¬ sity. A density of less than 100 percent is satisfactory as long as the material limits of the part are fully defined and substantially all of the lines are interconnected or, alternatively may be an open or close weave conductive cloth. When used between two conductive images, nonconduc- tive cloth may also be used to form a composite structure. The invention makes it possible to controllably electric-

ally proqram the shape of articles obtained from both room temperature castable materials and even thermoplastic and thermoceramic materials. Electroshaped materials can be used in conjuction with one or more computers. A computer used in the design and fabrication of a spare part or prototype ob¬ ject in the manner that a computer is currently known to de¬ sign and generate engineering documentation for an object. Such documentation such as drawings of an object and the use of computers to generate such drawings are well known art. The manner in which a computer is used to electroshape mat¬ erial into an object will be discussed in this disclosure. The invention has many advantages, over prior art means of manufacture. The invention enables objects of different shapes to be fabricated in remote locations, using universal tools and materials positioned at that location. Programma¬ ble molding of electroshaped materials, can, in many cases, eliminate the need for lathes or other capital machinery used in manufacture. Money and time can be saved by the elimination of the need to buy and ship such equipment. The cost of skilled labor in operating such equipment is re¬ duced. Use of the invention can save money and time by elec¬ tronically transmitting data and fabricating the part at a remote site rather than having to pay for and await the shipping of the part. Part designs can be stored by means such as for example a computer disk and easily referenced for production or reproduction years after the part is de¬ signed. This eliminates the need to store bulky engineering drawings, fixtures and tooling. Designs can be standardized on the disks to reduce variances in a batch of manufactured parts. The invention is useful in the fabrication of com¬ posite articles wherein cross section conductive images are formed with one or more conductive layers such as for exam¬ ple a conductive fabric.

It is therefore an object of the invention to provide materials that can be electrically shaped, to provide means whereby the end product properties of electroset materials can be controllably and electrically altered and to provide a means of electrically providing anisotropy in the end

product properties of an electroset material.

It is another object of the invention to provide elec¬ troset materials with electrically controlled end product properties and to provide electrically controlled means for foaming an electroset material wherein said foaming may be homogeneous, or alternatively anisotropic.

It is still yet further another object of the invention to provide means for the anisotropic foaming of shoe soles. It is another object of the invention to provide a means whereby the properties of soles of shoes derived from poly¬ mers can be quickly altered during their fabrication. BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the invention will become apparent when considered with the following detailed description and accompanying drawings in which:

Fig. 1 is a sectional view of a testing arrangement com¬ prising a high voltage probe, a high voltage power supply circuit and a beaker of electroset fluid. Fig. 2 is a perspective exploded view of a simple elec¬ troset mold.

Fig. 3 is a perspective view of an electroset article showing anisotropic void distributions.

Fig. 4 is a section view of a mold for making an elec- troset article with diverse densities.

Fig. 5 illustrates three conductive images prepared to conform to section views of the flange shown in Fig. 6, taken along the lines indicated as 1-1, 2-2 and 3-3 in Fig. 6. Fig. 6 schematically illustrates three spaced apart con¬ ductive images sparated by an electroset fluid under the influence of the Winslow effect.

Fig. 7 illustrates a computerized process for making articles in accordance with the present invention. Fig. 8 is a perspective view of spacer frames and dielectric substrates used in making an electroset mold.

Fig. 9 is a section view of a completed electroset mold. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In general, a phase changing vehicle that is substantial¬ ly a dielectric material is suitable for use in electroset compositions if they, in conjunction with the aggregate par- ticulate exhibit the second Reitz effect. Such materials in- elude but are not limited to Room Temperature Vulcanizing (RTV) silicone rubber, rubber cement, oil based paints, li¬ quid plastic coating materials, thermoplastics, polymers such as polyester, polyurethane, epoxy compositions or other spreadable or moldable dielectric materials. Conductive flu- ids such as paint thinner or varnish remover are not expec¬ ted to be good vehicles and neither is a fluid wherein the water content is high.

Shapes of various forms are formed using materials of the present invention. The shapes are permitted to change state, that is to harden, cure or solidify normally; or, their change of state is accelerated by applying an electric field to the shape, much in the same manner as an electric field is applied to an electroviscous fluid to cause the fluid to temporarily solidify. Embodiments of the invention are now presented. It is understood that the invention is not limited to just these embodiments which serve to illus¬ trate the uses and advantages of the invention.

Example 1 An aggregate was made by mixing about 200 milliliters (ml) of aluminum powder, about 450 ml of graphite powder, about 2100 milliliters (ml) of glass microspheres, about 800 ml of water and about 425 ml of a ceramic cement with the commercial name of Quickwall (produced by the Quickrete Co.). The composition was mixed and then allowed to stand and harden. After hardening, the aggregate block thus formed was broken up into fine particles and sifted through a tea strainer to obtain aggregate powder. The powder was o o baked in an oven at about 450 F (232 C) for about an hour to ensure that it was anhydrous. One part by volume of the aggregate thus obtained was mixed with one part by volume (RTV 108) silicone rubber as manfactured by the General Electric Company and one part by volume 50 centistoke (cs) dimethyl silicone oil (brand SF

200) as anfactured by the Dow Corning Co. This composition was put into a beaker. An electric probe comprising two electrodes with a spacing gap of about 3 to 4 millimeters (mm) was inserted into the composition. Referring now to Fig. 1, probe 10 is electrically connected to high voltage power supply 18, as shown. High voltage power supply 18 was adjustable from near zero to more than 15000 volts. Power supply 18 was equipped with a voltmeter and a milliammeter. The full scale of the milliammeter was 50 milliamperes (ma) with the lowest scale graduation being 0.5 ma. Power supply 18 may comprise, but is not limited to, a Glassman 30 kilo- volt (kV) , 50 milliamp (ma) high voltage power supply manu¬ factured by Glassman High Voltage Inc. of Whitehouse Sta¬ tion, New Jersey, USA. Such a power supply, Model PS/PH030P050, serial 149470 Master/slave/AHV was used as power supply to energize the electroset fluids in this ex¬ ample. This power supply has the convenient features of both a tunable current limiter dial, which limits the maxi¬ mum allowable output current and a tunable voltage limiter dial, which limits the maximum allowable output voltage. Each dial also has an adjacent corresponding milliamp meter and kilovolt meter, respectively. Hereinafter, unless o- therwise specified, this supply was used in all tests of sample materials in accordance with the various examples. Sampling probe 10 used herein comprised two electrode plates 13 and 14 with dimensions of about 1.0 inch x 1.5 inch (2.5 cm x 3.8 cm) and which are made of aluminum. Plates 13 and 14 were separated by wooden strip 15 which had dimensions of about one inch (2.5 cm) wide and 0.2 inch (0.5 cm) thick. Plates 13 and 14 were secured to wood strip 15 by tape (not shown) leaving a portion of the plates ex¬ tending about one inch (2.5 cm) beyond wood strip 15 in an approximately parallel relationship. Electrical wires 11 and 12 were conductively attached to each of the plates 13 and 14, respectively, as shown in Fig. 1. Wires 11 and 12 were electrically connected to the power supply output positive and negative polarity, respectively. When elec- trosetting the following example materials, the electrodes

were immersed in the electroset material while it was in a fluid state. Afterward, probe 10 was energized electrical¬ ly. In the test results reported herein, probe 10 consisted of two aluminum plates, each having a surface area of about one square inch (about 6.5 cm ) and a spacing of about 3 to 4 mm. Probe 10 was energized with a potential of 6000 volts dc. Electroset fluid 20 in glass beaker 21 behaved generally as an electroviscous fluid, that is, when probe 10 was ener¬ gized, the fluid 20 "solidified" between plates 13 and 14 was withdrawn from the beaker 21. When the potential was re¬ moved, the fluid 20 reverted to a liquid and fell from probe 10. Probe was again inserted into beaker 21 and energized with 6000 volts dc to pick up fluid and withdraw it from the beaker 21. The material remained in its solidified state via the Winslow effect. Occasionally, arcing would occur and the potential was reduced to eliminate it. After 10 minutes, the material between plates 13 and 14 had hardened into a solid material and remained on the probe 10 after the potential was removed. However, a 3 to 4 mm thickness of the same com- position and of about the same surface area required about 12 hours to set and harden to a comparable hardness as the hardened composition between the plates.

In each of examples 2 through 11, the same test proce¬ dure was used as was used for Example 1 above. The test re- suits are reported below. The term electroset time refers to the setting time with electric potential applied, the poten¬ tial being gradually reduced from the value stated to miti¬ gate any arcing as occurred. The term, self cure time refers to the time required for a similar sized sample of the same composition to cure with no potential applied.

Example 2 A phase changing vehicle known as Rustoleum wood saver paint (light gray 7180) , manufactured by Rustoleum Corp. of Vernon Hills, California, US was mixed with aggregate that was made in the same manner as that in Example 1. The mix¬ ture comprised about 3 parts by volume phase changing vehi¬ cle mixed with about 2 parts by volume aggregate. A poten¬ tial of about 6000 volts was applied by the probe to a sam-

pie. The composition electroset time was about 30 minutes and the composition self cure time was more than 24 hours.

Example 3 A phase changing vehicle known as Varathane liquid plas- tic (clear, gloss type) , manufactured by the Flecto Co. of Oakland, California, US was mixed with aggregate that was made in the same manner as that in example 1. The mixture comprised about 3 parts by volume phase changing vehicle and about 2 parts by volume aggregate. A voltage potential of about 6000 volts dc was applied by the probe to the sample. Composition electroset time was 20 minutes and the self cure time was more than 24 hours.

Example 4 A phase changing vehicle known as Polyurethane clear plas- tic coating (sold under the Channel Home Center brand name) was mixed with aggregate that was made in the same manner as that in example 1. The mixture comprised about 3 parts by volume phase changing vehicle and about 2 parts by volume aggregate. A voltage potential of about 6000 volts dc was applied by the probe to the sample. Composition electroset time was 40 minutes and the self cure time was more than 6 hours.

Example 5 A phase changing vehicle known as Fabulon Ultra Gloss Epoxy Bar Top Finish, manufactured by the Fabulon Products Co. of Buffalo, New York, US was mixed with aggregate that was made in the same manner as that in example 1. The mix¬ ture comprised about 3 parts by volume phase changing vehi¬ cle and about 2 parts by volume aggregate. A voltage poten- tial of about 6000 volts dc was applied by the probe to the sample. Composition electroset time was 25 minutes and the self cure time was more than 6 hours.

Example 6 A phase changing vehicle was made comprising about one part by volume RTV silicone rubber of the type used in exam¬ ple 1 mixed with about 1 part by volume dimethyl silicone oil also of the type used in Example 1. One part by volume of an aggregate known as corn starch (sold under the brand

name Cream and distributed by the Dial Corporation of Phoenix, Arizona, US) was mixed with about 1 parts by volume phase changing vehicle. A voltage potential of about 6000 volts dc was applied by the probe to the sample. Composition electroset time was 15 minutes and the self cure time was more than 12 hours.

Example 7 A phase changing vehicle known as Varathane liquid plas¬ tic (clear, gloss type) , manufactured by the Flecto Co. of Oakland, California, US was mixed with a corn strch aggre¬ gate that comprised the type use in example 6. The mixture comprised about 3 parts by volume phase changing vehicle and about 2 parts by volume aggregate. A voltage potential of about 6000 volts dc was applied by the probe to the sample. Composition electroset time was 35 minutes and the self cure time was more than 6 hours.

The principles of this invention have also been found to be effective under conditions of reduced tempera¬ ture where phase changing vehicles are sometimes reluctant to change phase. The extent of this effect is illustrated in the following example.

Example 8 An electroset composition was made by mixing by volume the following constituents: about 20 percent Weatherguard Brand Silicone Rubber; about 30 percent silicone oil of the type described in Example 1 and about 50 percent aggregate as described in Example 1. The phase changing vehicle had proportions of 2 parts Silicone rubber to 3 parts silicone oil. A first sample of composition was placed between two flat conductive plates and the surface temperature of the o o plates was reduced to about 34 F (about 1 C) . An electric potential of about 6000 volts dc was applied between the plates. Surprisingly, the composition rapidly solidified and set in about 2 minutes. Further tests were performed as fol- lows: Equal amounts of the composition of this example were placed in containers. One container was placed in a refrig- o o erator at about 34 F (about 1 C) and the second container o was allowed to remain at room temperature of about 74 F

o (about 23 C) . Each of the samples was tested by placing a probe as described in sample 1 in the material container, applying a potential of about 6000 volts dc, withdrawing the probe with fluid adhering by the Winslow effect and curing the material in the electric field. The setting time of each was found to be about two minutes. Next, samples of the phase changing vehicle (no aggregate) of this example were placed in containers. One container was placed in a refrig- o o erator at about 34 F (about 1 C) and the second container o was allowed to remain at room temperature of about 74 F o (about 23 C) . Each of the samples was tested by placing a probe as described in example 1 in the sample material, ap¬ plying a potential of about 6000 volts dc. The phase chang¬ ing vehicle alone had no accelerated curing properties under the influence of the electric field. Unaided by the electric field, compositions without aggregate had set after four and one-half hours.

The examples presented herein typically had a thickness of about 3-4 mm and were cured at a declining potential be- ginning at a potential of about 6000 volts dc and slowly reducing the potential as the material cured. It is to be expected that variation in the potential required may vary depending on the thickness of the material. It is also ex¬ pected that an optimum potential for each thickness can readily found by simple experiment. The volume ratio of aggregate to phase changing vehicle is another quantity that is expected to be varied in practice. While a volume ratio of aggregate in the composition has been varied in the examples from about 20 percent to about 40 percent by volume, it is expected that this ratio can be beyond those limits. The minimum percent aggregate is determined by the ability to cause the fluid to exhibit the Winslow effect and second Reitz effect when the electric field is applied and the maximum aggregate is determined by the preference to keep the composition initially flowable. If it is not required that the material be flowable, the aggregate can be substantially increased. Although not desiring to be bound by theory, it is believed that the accelerated curing

of the invention is related to the creation of a dipole mo¬ ment within electroset compositions as occurs in electro¬ viscous fluids. It is believed that the principles of the invention are usable to accelerate curing of any otherwise settable or curable composition, where said composition is a reasonably good dielectric.

Example 9 Fifty (50) ml of polyester resin, sold under the Marineyard Resin brand name and produced by Kardol in Miami, Florida, was mixed in a glass beaker with 50 ml edible cornstarch and one ml of an acrylic floor finish marketed under the brand name Giant by Giant, Inc. , Landover, MD. When this mixture appeared fairly homogeneous to the eye, 15 drops of a curing agent. Liquid Hardener Reactor, com- prising methyl ethyl ketone peroxide in dimethyl phthalate (MEKP) were added to the mixture and mixed. The sampling probe was then immersed into the mixture. The power supply voltage and current dials were used to set the maximum al¬ lowable voltage to 3 kv and the maximum allowable current to 5 ma per square inch area of electrode surface area. Af¬ ter several minutes under these conditions, the mixture be¬ tween the electrodes was found to have hardened. The sample was measured for density using a weighing scale and the Archimedes method of density measurement. Other samples of the mixture were also mixed and tested in a similar manner as the first sample. The same experimental conditions were held for these samples as those in the first sample fabric¬ ation except for the maximum allowable current. In each case, the maximum allowable current was varied from all previous samples. Afterward each sample was measured for its density. The results obtained are given in table 1.

The data for samples 1-7 demonstrate the variance in den¬ sity. These variations are a function of electric current at the 3 kV potential. The tests were repeated and equivalent results were ob¬ tained, demonstrating the electrical programmability of the electroset material density. Although the reasons for this effect are not clearly understood, it is known that the

polyester resin and MEKP, when mixed in adequate quantities, hardens by means of exothermic reaction. With no voltage ap¬ plied, this material solidifies in about 30 minutes. How¬ ever, when an electric field is applied to this material the time required for the material to solidify is reduced.

Sample Maximum Allowed Current

2 2

Number ma/in. (ma/cm )

(0.787) (0.629)

(0.524) (0.496) (0.314) (0.209) (0.000)

TABLE 1: PROPERTIES V.S. MAXIMUM ALLOWED CURRENT This reduction in time is proportional to the maximum per¬ missible current such that the first sample solidified much faster than any other. The resulting samples were all rec- tangular blocks. The probe was the electroset mold.

After the density measurements of Table 1 were obtained, the samples were cut open and examined. A number of voids were found within the less dense samples. Numerous voids were observed within the least dense sample while none were found within the most dense sample. The amount of observable voids within the samples varied as a function of sample den¬ sity, so that, for example, the amounts found within samples 3 and 4 were less than those of sample 1 and more those found in sample 6. Sample 7 had no discernable void embedded within.

The second Reitz effect causes the curing to occur over a shorter time period. Since polyester resin is a poor thermal conductor, the heat within the material builds or increases because the exothermic curing takes place over a shorter time period. Although not wishing to be bound by theory, one possible cause of cure acceleration in such exothermic elec¬ troset materials could be heating due to passage of current through the aggregate particles. The particles, when ener-

gized, often form themselves into chains that bridge the gap between the electrodes. Their alignment permit current to pass through each chain. This current can, in turn, cause heating. Such heating can be mathematically described by the well-known Poynting vector in electromagnetism. Poynting's vector and related heating are discussed in Foundations of Electromagnetic Theory, written by Reitz, Milford & Christy, 3rd edition and published by Addison-Wesley Publishing Co. in Reading, Massachusetts, US. An increase in heat could, at least in part, be respon¬ sible for the voids. It is expected that either the latent water found in edible corn starch or alternately a constit¬ uent of the fluid comprising the Giant acrylic floor finish would undergo a phase change from fluid to gaseous state when at a sufficient temperature and suitable pressure. This can be caused by heating such fluids to their phase change temperature for the existing pressure. Then the fluid begins to undergo phase change until all of the fluid becomes gase¬ ous. If, while the phase change is occurring, the bulk poly- mer which in this example is the polyester resin with MEKP, is solidifying, then the gas bubbles within the bulk polymer become trapped, thus forming voids in the cured material.

The void content of material is therefore a function not only of the temperature of the bulk material and the avail- ability of gas forming material within, but also is a func¬ tion of the progression of the solidification the bulk mat¬ erial. As the bulk material progressively permanently solid- ies, its viscosity increases, making it progressively more difficult for the gas bubbles to escape. Another origin of the voids is also possible. It has been observed in association with electroviscous fluids that sometimes, when near to or in contact with the charged elec¬ trodes, aggregate particles proximate an electrode become charged by that electrode. This results in the particle tra- versing the fluid between the electrodes and colliding with the opposite electrode. The particle then becomes charged with the charge of the opposite electrode and traverses the fluid again toward the first electrode.

This back and forth motion is often repeated by the par¬ ticle. This motion of a charged particle through the viscous fluid is expected to cause viscous heating. Such heating may increase the curing rate of electroset materials that cure normally by exothermic reaction. Particle motion may also result in better mixing of the constituent materials and may cause the voids by cavitation or other like means.

It is not yet apparent which, if any, of the above postu¬ lated theories may be correct in explaining the presence of increased heating in the curing material or voids in the cured material. What is known is that the passage of current causes the release of a gas or vapor useful as a blowing a- gent to form the voids. The observed foaming and the voids found in the samples are electrically controlled. This is an example of electroset materials with electrically activated and controlled foaming. Before each sample was examined for voids, its hardness was measured. Hardness measurements were performed with a Rex Duro eter instrument, type 'D 1 model standard dial which is produced by the Rex Gauge Co. in Glenview, Illinois, US. This gauge bears U.S. Patent No. 2,421,449 and was used in compliance with standard hardness measurement practices. The results are shown in Table 1. The hardness number shown is the average of 10 measurements for each sample. The data shows that hardness is an inverse function of applied electric power. Increasing electric power during electrosetting lowers the end product hardness. The data show that the formulation has controllable end product properties of both density and hardness.

It was also found that samples 1 and 7 had electrical re- sistance across the electrodes of greater than 20 megohms. This was done by disconnecting the probe from the power sup¬ ply and connecting it to an ohm-meter. For this measurement, a Fluke 8026B multimeter was used. However, just after mix¬ ing and before voltage was applied, the same multimeter was used to measure the material electrical resistance. The formulation in the initial fluid state, that is to say the state just after mixing, had a resistance of less than 10 megohms across the electrodes. This is important because

sample 1 solidified in less than 4 minutes whereas sample 7 required slightly over 30 minutes. This shows that the elec¬ troset material electrical properties are electrically con¬ trollable. Such controllable properties may be useful in ex- pendable systems where electrical resistance can act as a triggering mechanism.

Example 10 Another material comprising an epoxy with the brand name Two Ton Epoxy (manufactured by the Devcon Corp., Wood Dale, Illinois, US) was purchased at a local hobby shop. This epoxy is comprised of resin and hardener. Normal working time, the so-called pot life, is about 30 minutes for this epoxy after equal parts of resin and hardener are mixed. A 25 ml quantity of the resin was mixed with 30 ml of corn- starch and 3 ml of Giant brand acrylic floor finish. This was then mixed with a 25 ml quantity of the Two Ton Epoxy hardener. After mixing by hand for about 1 minute, probe 10 as described in example 1 was immersed in the mixture. The maximum output voltage of the power supply was set to 3 kV and the maximum current output was set at 5 ma. After a few minutes the material between the probe electrodes hardened. The probe was removed and replaced by another clean probe of the same type and dimensions. Two other samples were taken, under the same conditions the first except that the maximum applied current was changed to 2.5 and 0.0 a, res¬ pectively. The samples were weighed and their densities cal¬ culated from their volume. The results are shown in Table 2. Sample number


2 3

TABLE 2: DENSITY VS CURRENT AT 3 KV. As with the prior example samples, the samples this exam- pie 10 were broken apart after density was determined. These samples had observable voids in them. Sample 1, electroset with 5.0 ma/in maximum current, had significantly higher a- ounts of observable voids than the others. Sample 3 had no

observable voids while sample 2 had a number of the voids. Both the visible inspection and the density data indicate the electrical control of end product properties.

Example 11 In this example, several molds for electrosetting test samples were constructed generally conforming,to mold 70 as shown in Fig. 2. Electroset mold 70 comprises spacer 71 and electrode plates 73 and 75. Spacer 71 is made of an in¬ sulating material, such as for example wood and plates 73 and 75 are made of conductive material, such as for example steel. High voltage power supply 77 is shown adapted to electrically energize plates 73 and 75 through wires 78 and 79, respectively. During molding, electrode plates 73 and 75 are moved into an abutting relationship with the princi- pal faces of spacer 71 and securely retained so that mold¬ ing material does not readily escape from the molding area. In acquiring the data of Table 3, the plates were addition¬ ally sealed to the spacer using plastic postal mailing tape manufactured by 3M Co., St. Paul, Minnesota, US. Addition- ally, spacer 71 had inside dimensions: t about 0.3 inch

(.76 cm); w about 2.75 inch (6.93 cm) and h about 2.15 inch (5.42 cm), where t, w and h are as shown in Fig. 2. Plates 73 and 75 were made of steel and had dimensions of about 3 inch (7.56 cm) by 2.5 inch (6.3 cm) by about 0.125 inch (0.315 cm) thick. During electrosetting, mold 70 is held in a generally upright position with the open area opposite gravitational forces for convenience in pouring the uncured material into the mold.

A two part polyurethane comprising a resin and a hardener and sold under the brand name REN RP 6402 and commercially available from CIBA-GEIGY Corp. in East Lansing Michigan, US, was mixed with powdered carbon in the form of graphite in the proportions of about 100 parts by weight of harden¬ er; about 35 parts by weight of resin; and about 3 parts by weight carbon powder. This mixture was black. The two part polyurethane as commercially sold has a normal pot life or working time of about 30 minutes at room temperature. The carbon powder was manufactured by Gougeon Brothers, Inc.,

name as 423 Graphite by Oceana, a marine supply company in Annapolis, Maryland, US. After mixing, the electroset fluid was poured into mold 70 after mold 70 had been prepared by applying a mold release to the interior of mold 70. The mold release used was product number AC-4368 sold under the Fre- kote brand name by the Aerospace and Industrial Products Division of Hysol Corp. in Seabrook, New Hampshire, US. The electroset fluid was poured into mold 70 through the open gap at the top of the mold. Naturally, in this simple mold, the open side is preferably the side opposite the force of gravity. After pouring the mixture into the mold, the re¬ sistance of the fluid between plates 73 and 75 was made by disconnecting wires 78 and 79 from power supply 77 and con¬ necting these wires to a Fluke multimeter as described above. A resistance of about 7.8 megohms was measured. Then the plates were again electrically connected to the power supply and energized. The supply was set for a 3 kV maximum output voltage and a 5 ma maximum current output. Bubbling and foaming of the material as it electroset was observed, causing some material to be discharged from the mold. As the material hardened with continued applied electric power, the material conformed to the shape of the cavity of mold 70. After about 10 minutes, the material hardened and drew no measurable current. The plates were again electrically disconnected from the power supply. Using the Fluke multi¬ meter, a resistance of greater than 20 megohms was measured. Similarly, a second sample of the composition was fabricated and cured electrically at 3 kV and 2.5 ma. The electrical resistance of the sample was measured directly after the electroset fuid was poured into the mold and measured 7.8 megohms. After it was electrically cured, the resistance measured over 20 megohms. The electroset time for the second sample was about 15 minutes and some foaming was observed. The observed amount of foaming, however, was considerably less than that noted in the fabrication of the first sample. A third sample was fabricated similarly as the first. However, no voltage was applied to the fluid. After 30 minutes, the material had set. Using the Fluke multimeter,

the electrical resistance of the samples measured and found to be over 20 megohms. No foaming was observe during the setting of sample 3. Although all three samples achieved a resistance change for about 7.8 megohms to more than 20 megohms during their cure, the time required for this change was a function of cure rate, that is, the rate of change of resistance is proportional to current flow. The samples were then measured for their specific gravity. The data is listed in Table 3 in association with the current and cure or set time.

TABLE 3: MATERIAL PROPERTIES VS. CURRENT After the sample density was measured, the samples were cut open and examined. All threee samples contained voids. Sample 1 had the most observable voids. Sample 3 had the least and sample 2 had less than that of sample 1 but greater than that of sample 3. Voids in sample 3 were smaller in number and size than those found in samples 1 and 2. The amount of foaming corresponded to the relative maximum allowable current flow. Another effect found in sam¬ ples 1 and 2 was not observed with sample 3. Samples pro¬ cessed in accordance with sample 3 were easily separated from the electrodes after the material had set and cured. This was expected because the mold release agent had been used in the molds immediately prior to pouring the elec¬ troset fluid. The mold release worked and the finished sam¬ ple was easily separated from its electrodes. However, sam¬ ples 1 and 2 were only easily separated from the electrode that had been of positive polarity. The samples 1 and 2 were firmly attached to the electrode that had been of negative polarity. Other samples were made repeating the same pro¬ cedure as those used in accordance with the making of sam¬ ples 1 and 2. The same results as those found for samples 1

and 2 were found. After these samples were electroset, (i.e. caused to set or cure electrically) , they could be separated easily from only the positive polarity electrode. This situation was not expected because it had not been en- countered in the samples of examples 9 and 10. One cause for the difference between example 9 and 10 samples and samples of this example may be the difference of formulations. Exam¬ ple 9 samples were a polyester based electroset materials. Polyesters do not exhibit strong adhesion to metal surfaces. Since the electrodes were metal, the polyester samples did not, adhere to the metal electrodes. Example 10 samples were epoxy based electroset materials. Epoxies are known for their adhesion to many surfaces, including metal. Because mold release was not used on the electrodes when example 10 samples were electroset, it was expected that they would ad¬ here to the metal electrodes, as was observed. In fact, a composite structure was formed each time the samples of ex¬ ample 10 were electroset. The composite structure comprised both of the probe electrodes and the epoxy based electroset material that had been electroset between the electrodes. Effort was required to remove the electrode plates from the sample core material. This usually was performed by prying off a corner of the electrode from the sample and then, while gripping that corner with pliers, pulling, peeling or yanking the electrode off. Contrastingly, no significant electrode polarity preference in adhesion was found in the example 10 samples. Thus, the preference to adhere to only one electrode was surprising. For samples l and 2, a thin layer of reddish purple polymer formed on the negative pol- arity electrode. There was a significant difference in the color of this layer with respect to the rest of the bulk sample. The bulk of the electroset material solid was black except for this reddish purple layer.

Surprisingly, it was found that electroset material sam- pies of this example that had been electroset were aniso¬ tropic in both surface color and adhesion to the steel elec¬ trodes. This anisotropy demonstrated that a different poly¬ mer was formed on one electrode than on the electrode of

opposite polarity. The reddish purple polymer layer was that color because there was little or no carbon powder particu- late in it. The remaining bulk polymer was black because it did have the carbon powder in it. The reddish purple polymer is a different polymer from the black bulk polymer for the simple reason that its properties are different. Different polymers differ because of differences in their characteris¬ tic properties, said properties being mechanical, electrical or even optical. The reasons for the anisotropic adhesion and anisotropic optical characteristics are, at present, unclear except for the fact that they resulted from electro¬ setting the samples. The anisotropic properties of adhesion are useful in making end articles where it is desired that one of the electrodes become a part of the end item and the other electrode release from the end item. Examination re¬ vealed that samples 1, 2 and 3 varied in their relative com¬ pressibility. Compression tests were performed using an Instron 15 Model 1325 Servo Hydraulic Machine. For each of samples 1, 2 and 3, a 100 pound force was applied to one surface of an opposing pair of surfaces while the other sur¬ face rested against a plate. The change in thickesss of the material as a result of applying the 100 pounds force was measured. The relative compressibility of the samples is in¬ dicated by the ratio dt/t where dt is the change in thick- ness and t is the uncompressed thickness. The results of these tests are shown in Table 3. The compressibility of the material was identified as being a function of the in¬ creasing amount of voids. The voids appeared to be uniformly distributed throughout each sample. Example 12

A 500 ml quantity of electroset composition that was made in accordance with the proportions of example 9 was modified by adding 50 ml cornstarch and 150 ml of Polyurethane clear plastic coating that was purchased under the Channel Home Center Brand name from the Channel Home Center Store in

Lanham, Maryland, US. Probe 10 was inserted into the mixture and energized to a maximum of 3.5 kV and maximum of 3.3 ma using the Glassman power supply 18. Probe 10 was removed

and it was noted that the material between the probe elec¬ trodes had solidified via the Winslow effect. After 3 to 5 minutes the mixture began to foam and some of the fluid ex¬ panded outward from between the electrodes and fell back in- to the container. The remaining mixture hardened into a per¬ manent solid within 2 minutes after foaming initiated. The sample was removed and broken into two pieces and examined.

An anisotropic void distribution was found within the sample. The sample fabrication was repeated several times and the same results found each time. Thus, anistropy was observed in all samples. Referring now to Fig. 3, a cross- section of an end product such as fabricated in accordance with this example illustrated generally as 80. Two conduc¬ tive plates 81 and 82 are shown removed from an electroset end product core section identified generally as 90. When an electroset end product composite is fabricated and con¬ ductive plates 81 and 82 are left in place, one end product is formed. When the electrode plates are removed, a second end product is formed. Electroset product 90 comprises a thin sheet of solid polymer material 91, a polymer layer 92 having voids embedded within the bulk solid product 90, and a thicker layer 93 of bulk polymer having no voids. The thickness of thin sheet 91 was noted to be between about one third to one fourth the thickness of void bearing layer 92 and about one fourth to one fifth of the thickness of sub¬ stantially solid layer 93. In the test example that was electroset (i.e. electrically cured), thin sheet of material 91 was found to be about .020 inch (0.5mm) thick. Polymer layer 92 containing the voids was found to be about .070 inch (1.8 mm) thick on average, and polymer layer 93 was found to be about .095 inch (2.4 mm) in thickness. The layer of voids was always found adjacent to the thin layer next to the negative polarity electrode. Causes for the anistropy in the void distribution are not, at present, known. How- ever, because it was always found near the negative elec¬ trode, the void distribution obviously had electrical or¬ igins.

An example of the usefulness of programming end product

properties is in the making of composite articles. The in¬ vention enables different portions of the same article to be made with different material properties. This is done by programming the portions differently. For example, a shoe sole may be made wherein one part of the sole, such as for example the area under the ball of the foot or alterna¬ tively the arch, or yet alternatively, the heel is desired to be of a different compressibility than the remainder of the sole. One method of making such a shoe sole is to first make an insert of one compressibility by electrosetting a material at a relatively high current setting and then cast¬ ing this insert into a material that is either electroset at a different rate or allowed cure to normally.

It is appreciated that many other products can be fab- ricated in accordance with the present invention without de¬ parting from its scope. Electrical programming enables dif¬ ferent areas or zones of an integral piece of material or of an object to be caused to have different densities or com¬ pressibilities while only mixing one basic composition. An example of an apparatus for achieving different areas or zones of physical properties by electrical programming is shown in Fig. 4. Power supply 151 is shown with one terminal electrically connected to ons mold surface 191 via electric¬ al connections 157 and with the other terminal connected to a current distribution device such as for example switch 192. Mold surfaces 191 comprise conductive areas 193a, 193b and 193c and insulating regions 194a and 194b. Switch 192 is actuated to sequentially or alternately apply power to con¬ ductive areas 193a and 193c and then to conductive area 193b. An electroset mixture such as the that in example 11 is placed between plates 191 which consist of conductive a- reas 193a, 193b and 193c which may comprise any good conduc¬ tive material, such as, for example, steel, copper, aluminum or bronze. Power supply 151 is then energized. Current may then be applied through the composition adjacent areas 193a and 193c at a rate and time different from the rate and time current is applied through the composition adjacent areas 193b, thus forming an integral solid having different phys-

ical properties such as density or compressibility in dif¬ ferent areas of the solid.

It is appreciated that electroset materials can be formed into many different size objects and many different shaped objects. Computerized systems comprising a computer con¬ trolled plotter, of alternatively, a computer controlled printer or, still alternatively a commercially available copier machine may all be used to draw or shape the electric field which electrically shapes the objects made from elec- troset materials. The electric field shaping may be accom¬ plished by computer controlled devices drawing electrically conductive ink onto a dielectric substrate or, alternative¬ ly, drawing electrically nonconductive ink onto an electric¬ ally conductive substrate. In the case of the electrically conductive ink being drawn onto a dielectric substrate, the ink is drawn in the shape of the object that is fabricated. In the case of the nonconductive ink being drawn onto the electrically conductive substrate, the nonconductive ink is drawn over the substrate excluding the shape of the object that is to be fabricated. In other words, the exposed or bare surface area of the conductive substrate that is not drawn onto with nonconductive ink is shaped into the shape of the object to be fabricated-. The term 'ink 1 used in this disclosure refers to any fluid or solid composition which is used to make images in devices such as copier machines, printers and plotters, pens and pencils.

One embodiment of a composite article of the invention is illustrated in Figs. 5 and 6. In Fig. 5, three conductive images are identified as 215, 216 and 217, each having a large center hole 211 and a plurality of peripheral holes identified as 212. In Fig. 6, conductive images 215, 216 and 217 are shown spaced in a spaced apart relationship and separated by an electroset composition identified as 219 which is held in place via the Winslow effect due to high voltage potential provided at contact illustrated as 223 and 225 for the positive polarity and 227 for the negative pol¬ arity. Images 215, 216 and 217 are spaced apart by suitable fixturing (not shown) during curing. Suitable fixturing may

comprise, but is not limited to, picture frames and tape as disclosed later in this disclosure. Images 215, 216 and 217 are made from any suitable material such as conductive fabric which may either be loosely or tightly woven. Alter- nativeely conductive images 215, 216 and 217 are formed from sheet metal such as for example steel or aluminum. Images 215, 216 and 217 are made by conventional means such as for example blanking and punching or die cutting.

In an energized electroset material, the particulate typ- ically aligns along the electric lines of flux and form chains of particles. When images 215, 216 and 217 are made from loosely woven fabric, the chain formations constitute a weave. A cross bonded composite material results. It is not necessary that all of the images be made of the same a- terial. For example, layers 215 and 217 may be made of solid metal and layer 216 may be made of conductive fabric, (such as for example carbon reinforced fabric) .

A flange may be fabricated by spacing images 215, 216 and 217 apart by suitable fixturing. Images 215, 216 and 217 are electrically connected to power supply 220 by conductive wires 223, 225 and 227 as shown in Fig. 6. Conductive wires may comprise, but are not limited to, aluminum, copper or bronze wire. Images 215, 216 and 217 are then immersed in an electroset composition. Such a composition may comprise for example, examples l, 2, 3, 4, 5 of 6 of this disclosure, or alternatively, any other suitable electroset composition. High voltage power supply 220 is turned on and electrically energizes images 215, 216 and 217. Images 215, 216 and 217 are withdrawn from immersion in the electroset composition except that electroset composition 219 is electrically held in position as shown in Fig. 6 until electroset composition 219 cures. Images 215, 216 and 217 of Fig. 5 correspond to a view of Fig. 6 taken at lines 1-1, 2-2 and 3-3, respective¬ ly. Another embodiment of a composite article of the inven¬ tion uses the process of forming images 215, 216 and 217 each by despositing electrically conductive ink onto insul¬ ating substrates such as, for example, plastic view graph

sheets, rubber sheets or, alternatively paper sheets. A com¬ posite article is fabricated in the same manner as in the previous embodiment. However, the means of fabricating the may differ in that images 215, 216 and 217 are drawn elec- trodes, said electrodes comprising electrically conductive ink drawn onto an electrically insulative substrate is il¬ lustrated in Fig. 7.

Computer 250 is a general purpose digital computer, such as for example an IBM PC desktop computer or a Zenith Data Systems desktop computer properly programmed with software for generating design images and producing sections of such images. Such computers are readily available commercially. Output imaging device 253 may be a plotter, such as for ex¬ ample one manufactured by Houston Instruments or alterna- tively may comprise a laser printer instead of a plotter. A suitable laser printer may comprise but is not limited to, for example, a Laserjet printer manufactured by the Hewlett Packard Corporation located in Gaithersburg, Maryland, US. When a laser printer is used as output imaging device 253. The standard printing powder may be used or, alternatively may be replaced with an electrically conductive or electric¬ ally semiconductive powder. When replaced with conductive powder, such may comprise, but is not limited to, carbon powder in the form of graphite powder as sold under the brand name West System 423 which is manufactured by

Gougeon Brothers of Bay City, Michigan, US. The standard printer powder is nonconductive and can be used when the blank substrates are conductive. Conductive substrates may comprise, but are not limited to, tin foil, aluminum foil or other suitable material. Alternatively, when nonconductive blank substrates are used, the printer powder must be re¬ placed with a conductive powder. When nonconductive sub¬ strates are used, substrates 255 may comprise electric in¬ sulating material such as plastic, or alternatively, paper. When conductive ink is used in imaging device 253, sub¬ strates 255 must be insulating material. Imaging device 253 draws images onto substrates 255, thereby making the imaged substrates 256. An example of suitable insulating blank sub-

strates 255 are insulating substrates 331, 332 and 333 of Fig. 8. Insulating substrates 331, 332 and 333 comprise any suitable material that is compatible with the material to be electroset. One example of a suitable substrate is plastic 5 viewgraph sheets sold by Konica Business Machines, USA, Inc. which is located in Windsor, Connecticut, US. High voltage power supply 220 of Fig. 6 preferably has the ability to in¬ dependently limit voltage and current to predetermined maxi- mums, such as the Glassman power supply of prior examples.

10 When a plotter is used as the output imaging device 253 of Fig. 7, electrically conductive ink must be used in the plotter pen. Such conductive ink may comprise a suitable commercially available product or may be made by mixing the following constituents together by volume: 10 parts

15 acetone, 3 parts West System 423 graphite powder and 1 part clear adhesive. Cans of acetone are sold by the Hechinger's Store in Annapolis, Maryland, US. The clear adhesive is sold under the brand name UHU and is manufactured by the Linger & Fischer Co. which is located in West Germany. The plotter

20 pen may comprise a rapidograph pen, size 9, produced by the Kohinor Company located in West Germany. Communications link 251 may comprise any suitable electrical wiring interface produced by such manufacturers such as Nevada Western of Sunnyvale, California, US or, alternatively, International

25 Business Machines which has offices in California, US. Referring now to Fig. 6, soild object 229 comprises images 215, 216 and 217 and electroset composition 219. Ob¬ ject 229 is formed by the following procedure. Conductive images 215, 216 and 217 are drawn onto substrates 331, 332

30 and 333, respectively, by computer controlled plotter 253. Substrates 331, 332 and 333 each are then overturned and plotter 253 draws the conductive images on the reverse side of the substrates. The conductive ink forming images 215, 216 and 217 result on both sides of substrates 331, 332 and

35 333, respectively. Conductive ink pathways are also drawn by the plotter 253 onto said substrates such that said path¬ ways (not shown in Fig. 8) extend from said images (not shown in Fig. 8) 215, 216 and 217 to the outer extreme egdes

of substrates 331, 332 and 333, respectively. Said pathways provide conductive paths through which images 215, 216 and 217 are electrically charged by the power supply.

Before energizing images 215, 216 and 217, insulating substrates 331, 332 and 333 are inserted between spacers 341a, 341b, 341c and 341d which are shown in Figs. 8 and 9. Spacers 341a, 341b, 341c and 34Id may comprise any good solid dielectric material. One example of such a spacer ma¬ terial are four wood picture frames that are manufactured by Lambert Inc. and were purchased at the K-Mart Store in Hyattsville, Maryland, US. The cardboard backings, the at¬ tached glass panes of said picture frames and the staples used to secure said glass panes and cardboard to the picture frames were removed. Picture frames 341a, 341b, 341c, and 341d were 1.3 cm wide along the dimension indicated by the letter w in Fig. 8. Each of the picture frames 341a, 341b, 341c and 34Id were sanded with sandpaper by hand along the facing of the frame until the thickness of each frame, which is indicated by the designation t in Fig. 8 was 6 milli- meters (mm) . The resulting frames had a thickness, t, of 6 mm, a width w of 0.6 cm, a height indicated by the designa¬ tion fh of 7.75 inches and a base indicated by the designa¬ tion fb of 6.25 inches, all as shown in Fig 8. Dielectric substrates 331, 332 and 333 as shown in Fig. 8, are rectan- gular, clear plastic sheets, each with a base dimension as indicated by the designation sb of 7 inches and which are 5 inches along the dimension indicated by the designation sh. Dielectric substrates 331, 332 and 333 were fabricated by cutting by hand with scissors plastic viewgraph sheets that are marketed as item PP2500 under the Scotch trade name and are manufactured by the 3M Company in St. Paul, Minn. All frames 341a, 341b, 341c and 34Id were then taped around with double sided tape (not shown) , that is to say, tape that has sticky adhesive on both sides. Such tape may comprise Scotch brand double stick tape, catalogue number 136, manufactured by the 3M Consumer Products Group of St. Paul, Minnesota. Said tape applied to the wooden frame only and was not ap¬ plied in any way that would obstruct the open area inside

each of the frames. After preparing the frames, electroset mold 445 as shown in Fig. 9, was fabricated by inserting substrates 331, 332 and 333 between frames 341a and 341b, frames 341b and 341c, and frames 341 c and 34Id, respective- ly. Frames 341a, 341b, 341c, 34Id are then pressed together by hand to form mold 445. Because the 445 mold is pressed together, the tape of mold 445 serves to hold mold 445 to¬ gether. However, an additional means of holding mold 445 together may comprise, but is not limited to, positioning rubber bands (not shown in Fig. 9) around frames 341a,' 341b, 341c and 341d. Substrates 331, 332 and 333 were so posi¬ tioned with respect to frames 341a, 341b, 341c and 34Id that the 7 inch base dimension of the substrates, said dimension having been indicated by the designation sb of Fig. 8 was parallel to the 6.25 inch base dimension of frames 341a,

341b, 341c and 341d. Such positioning of the substrates re¬ sulted in a gap between the top and bottom edges of said substrates and the top and bottom interior edges of the frames. This gap later permitted unenergized electroset fluid to flow through the volume of space between electrode images 215, 216 and 217 when mold 445 was immersed in a bath of electroset material. Mold 445 was then electrically con¬ nected to power supply 220 of Fig.6. This was accomplished by securing electrode aligator clips (not shown in Figs. 6 and 9)to the electrically conductive paths at the edges of substrates 331, 332 and 333. The paths electrically con¬ nected the aligator clips to images 215, 216 and 217. The aligator clips were in good electrical contact with said conductive paths. Electrical wires electrically connected to the positive polarity output of power supply 220 were con¬ nected to the aligator clips at the edges of substrates 331 and 333. An electrical wire electrically connected to the negative polarity of power supply 220 was electrically con¬ nected to the aligator clip at the edge of substrate 332. The wires comprised copper wires. However, in practice such wires may comprise aluminium, bronze, or other electrically conductive materials. Thus, the wires and aligator clips were so positioned with respect to the power supply 220 and

the conductive images 215, 216 and 217 so as to permit power supply 220 to electrically energize images 215, 216 and 217 when said power supply 220 is turned on. Mold 445 was im¬ mersed in a 5 gallon container of the electroset composition of example 1. Suitable alternative elelctroset compositions include examples 2, 3, 4, 5, 6 or any other suitable elec¬ troset composition. The power supply 220 output voltage and current were set to maximums of 7.5 kilovolts and 25 illi- amps, respectively. The power supply was turned on. Thirty seconds after the electric power was applied to mold 445, mold 445 was removed from the container of electroset com¬ position. The electric power was maintained for 45 minutes. After that period of time, the power supply 220 was turned off. Mold 445 was permitted to stand for 5 days. Afterward, mold 445 was disassembled and the electroset flange removed. The parts of substrates 331, 332 and 333 in excess of the object were subsequently cut off and removed by hand using scissors. The object was a paperweight.

Materials that have been formed from electroset composi- tions using the electroset process have unique properties. As a result of the aggregate particles aligning along the electric lines of flux, it is observed that often the re¬ sulting electroset article has, aligned columns of material embedded in the cured material. In some compositions, the alignment is visible with the unaided eye. Such alignment is useful in identifying materials that have been produced by the electroset process. Other potential means of identifying such articles may be found, such as for example, identifica¬ tion of trace poylmers that are produced only when the a- terial is cured in the presence of a field. Such identifica¬ tion may include the use of infrared spectroscopy and nu¬ clear magnetic resonance (NMR) detection and mapping. Elec¬ troset articles having a (-polymer-particulate-polymer-par- ticulate-polymer...) structural periodicity that can be map- ped using NMR and other detection means can be identified made by the electroset process. Other detection means such as for example, X-ray defraction, Bragg reflection mapping and electron defraction may also prove useful in detecting

the periodicity characteristics. It is appreciated that there are many other electroset compounds and mixtures that can be made to have electrically programmable and electric¬ ally controllable physical properties. Material properties such as electrical resistivity, density, hardness, adhesion and compressibility are all electrically controllable by means of the invention. It is appreciated that many uses of the invention can be employed to render desirable results. Such uses include, but are not limited to, the commercial production of shoes and sanding disks and the fast fabrica¬ tion of replacement parts and also prototype objects. It will be appreciated in the light of this disclosure that many other kinds of electroset materials with electrically programmable and electrically controllable properties may be used without departing from the scope or spirit of the pre¬ sent invention. It is to be understood that the embodiments herein described are only illustrative of the application of the principles of the invention and that numerous modifica¬ tions, alternative embodiments and arrangements may be readily devised by those skilled in the art in ths light of this disclosure without departing from the spirit and scope of the invention. It is to be understood that within the scope of the appended claims, the invention can be practiced otherwise than as specifically described herein. Various omissions, modifications and changes to the principles des¬ cribed herein may be made to one skilled in the art without departing from the true scope and spirit of the invention.