DEVICE AND METHOD FOR MEASURING FRICTION AND ADHESION FORCES BETWEEN TWO SURFACES IN CONTACT FOR POLYMER REPLICATION PROCESSES

Technical field

[0001] The present disclosure is related to an equipment to measure the friction and adhesion forces between two solid surfaces. More specifically, the mentioned equipment measures the adhesion and friction forces in similar conditions to the demoulding phase in the polymer replication processes.

Background

[0002] The tribological study between surfaces in contact is an area that, despite being well studied, there are still several gaps in some of the mechanisms and phenomena related to the tribological behaviour between materials.

[0003] Specifically, with respect to the friction and adhesion forces in similar conditions to the polymer replication processes, there are still questions about the influence of the adhesion between the materials and how it can influence the friction behaviour.

[0004] For that reason, several research areas have been developed and several authors have contributed to the explanation of these phenomena. However, from these studies it is possible to understand that, for example, the friction in the demoulding phase is related with several factors inherent to the injection moulding process, such as the melt temperature, the demoulding temperature, the pressure, demoulding speed, both material of the moulding part and the mould, time of application of the holding pressure, the mould surface roughness and the existence of details and ribs in the mould cavity. These factors are the same addressed to other techniques used on surface replication of polymeric materials.

[0005] However, despite the state of the art being widely discussed regarding the coefficient of friction between two surfaces in contact, there are few studies performing its measurement in similar conditions to those that occur, for example, in the injection moulding process. These studies are divided between the tests carried out on equipment different from the injection moulding machines and in other cases, on instrumented moulds that allow the measurement of ejection forces, since it is not possible to directly measuring the coefficient of friction during the production process, regarding the process conditions that affect the friction in the injection moulding process.

[0006] Regarding to the moulding shrinkage in the mould and the ejection force Delaney has carried out several studies related to the ejection forces prediction applied into moulds with periodic surface profiles [1], as well as studies of friction measurement methods applicable to the ejection forces prediction for micro replicated parts [2] and development of an equipment to measure the friction for application in the prediction of the ejection forces [3], which do not work autonomously, having to be coupled to a universal testing machine and a research project on the polymer-mould steel interface to study the influence of adhesion on the ejection force optimization [4]

[0007] In addition to the contribution to prediction models where mathematical models were defined for the ejection forces prediction [1] and ways to obtain the required values for these theoretical models [2] applied to these type of forces, Delaney's studies also used equipment usually indicated for other type of tests, but adapted to measure the adhesion between the polymer and the production tool. In this case the authors use a steel mould to study the influence of adhesion in the ejection forces optimization [4], the value of the friction forces is not measured using the equipment, that only measure the surface wettability between both surfaces, polymer and mould surface.

[0008] The ejection forces in the injection moulding process were also studied by Pontes et al. [5, 6] The work performed by Pontes focused on the development of a prediction model for ejection forces in tubular parts [6] Pontes also studied the conditions that have influence in the ejection forces during the demoulding phase of the injection moulding process [5] For that, it was developed an instrumented mould [6] that allows the ejection forces measurement, as well as the pressure and temperature measurement at specific points of the mould cavity. Nevertheless, a technician in the subject will understand that, despite this technique allows the ejection forces measurement does not allow directly the measurement of the friction force. This technique only allows the ejection force measurement that has more contributions beyond the friction force between the two surfaces. In addition, this mould does not work autonomously and must be used in an injection moulding machine for the part production, a process during which the values of the ejection force and not the friction forces are measured.

[0009] Several equipment and prototypes have been developed for the evaluation and characterization of tribological properties between materials, namely friction, adhesion and wear. Most of the methods and equipment used for tribological studies are available in the literature, being some of them developed to fill gaps that still exist in the state of the art, such as, measurement of the friction forces in replication conditions, where it is intended to study the contact between surfaces, with variation of some processing conditions, including the test temperatures, sliding speed, type of materials and contact force.

[0010] An example refers to the equipment developed by Kashani [7], which consists of a tribometer that allows the identification of the dynamic and static coefficient of friction in short duration tests as well as the wear rate of parts in long duration tests. This type of test, despite performing the static and dynamic coefficient of friction measurement, is not indicated to measure these values under similar conditions to those used in replication techniques, but to study the behaviour of materials when applied to gears and bearings and its wear over time.

[0011] Regarding adhesion tests, Chen and Hwang [8] developed an instrumented mould that, according to the authors, allows the measurement of the ejection forces with polymers that present high adhesion problems, such as poly methyl methacrylate (PMMA), polycarbonate (PC) and polyurethane (TPU). Those skilled in the technique recognize that in this case, it is not also possible to carry out the tests without the use of an additional equipment, as is the case of use an injection moulding machine.

[0012] The measurement of the friction properties in polymers was performed by Pouzada [9] using the equipment and method described in the patent document PT 102606 B, and testing some of the variables that influence the friction properties between two surfaces. Specifically, a method and equipment for the characterization of the static and dynamic coefficient of friction between polymer samples with surface finish replicated by steel, where allows to simulate the injection moulding process, mainly the demoulding phase of this process,

B working coupled to a universal testing machine. However, the revealed equipment only allows the determination of the static and dynamic coefficient of friction, besides presenting the limitation of not working independently. This equipment is also not sensitive enough to measure the adhesion between two solid surfaces. The lack of sensitivity for the measurement of adhesion is related to the method of actuation of the horizontal movement that is carried out by means of a pneumatic cylinder which, despite complying with the performance of the platform, does not allow to vary precisely the force that is acting during the test or the force that is acting during the test or the force with which the platform recedes.

[0013] The patent document PT 103935 B also describes a machine and test method for determining the coefficient of friction at contact interfaces with newly generated and non- oxidized surfaces. However, despite measuring the coefficient of friction, the equipment and method described are more suitable for determining the coefficient of friction between the cutting tool and the part to be machined, which means, that it can be applied to determine the friction coefficient cutting technological processes by trim removal and not in replication processes.

[0014] As already discussed above, the state of the art is wide when it refers to equipment and methods for the characterization of the tribological contact between two surfaces, as shown in the documents: US 8,074,488, US 7,287,420, US 7,886,571, US 10,113,950, US 9,581,534, EP 3,012,614 and ES 2612028. Most of these documents refer to specific tests and applied in several domains, that is, some are related to the with the adhesion of coatings to surfaces, others related with polymer samples and for last related with friction between a vehicle with a surface. Specifically, the documents, US 8,074,488, US 10,113,950, EP 3,012,614 and ES 2612028, despite allowing the measurement of coefficient of friction between two surfaces, the forces are applied in a specific field that is the friction generated in the movement of a vehicle and a surface, for that reason it does not allow the coefficient of friction measurement in similar conditions to the replication processes. In the case of the patent US 7,287,420 despite having force measurement sensors, only allows the verification of the adhesion force between the polymer and the coating applied to the substrate, developing zones where the coating is pulled out and measuring the required force. Regarding the patent US 9,581,534, is described an equipment that allows the wear determination between two surfaces, where the more rigid surface wear out the one there is in direct contact. Although, despite being a tribological equipment it is used to measure this property where there exists between the surfaces under study a lubricant.

[0015] On the other hand, the technology revealed in the document US 7,886,571 allows the measurement of the adhesion and friction properties between polymers or polymers against other materials and that can be applied in the micro and nano structures replication domain, however, there is a gap in the processing conditions that usually have influence in the adhesion and friction properties between surfaces, that are the contact and test temperature. The advantage of this equipment is related in the optical system embedded that allows the determination of the real contact area between the two surfaces with greater precision.

[0016] The importance given to the study of the tribological conditions, namely the friction and the adhesion, during the demoulding phase in the injection moulding process, is due to the need of decrease the required force to demould the part in the injection moulding process and to reduce the defects in the final part that could appear due to the excessive friction and adhesion between the moulding and the mould cavity. This phenomenon, especially friction, is more evident in deep parts where it is verified an increase of the shrinkage of the moulding into the mould during the cooling phase. Despite, of all the performed studies for the coefficient of friction determination in the described conditions, it is not yet possible determine the impact of the adhesion between the surfaces in the coefficient of friction in the demoulding phase of the surface replication processes, as for example, is the case of the injection moulding and micro-injection moulding processes.

[0017] Therefore, it remains clear that despite the existence of various equipment and methods for coefficient of friction determination, it is possible to understand that none of them is capable of determine the coefficient of friction and adhesion autonomously. Thus, the present invention provides the state of the art with an autonomous equipment that allow the determination of the friction and adhesion forces, and consequently the determination of the coefficient of friction, in similar conditions to the polymer replication processes.

[0018] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.

[0019] References: [1] K. Delaney, G. Bissacco e D. Kennedy, "A Study of Demoulding Force Prediction Applied to Periodic Mould Surface Profiles," em Society of Plastic Engineers' ANTEC 2010 conference., 2010.

[2] K. Delaney, D. Kennedy e G. Bissacco, "A Study of Friction Testing Methods Applicable to Demoulding Force Prediction for Micro Replicated Parts," em Matrib 2010, Croatia, 2010.

[3] K. Delaney, D. Kennedy e G. Bissacco, "Development of a Friction Testing Apparatus for Demoulding Force Prediction," em IMC28, International Manufacturing Conference, 30th August - 1st September, Dublin, Ireland, 2011.

[4] K. Delaney, D. Kennedy e G. Bissacco, "Investigating Polymer-Tool Steel Interfaces to Predict the Work of Adhesion for Demoulding Force Optimisation," em MTSM 2011. Split, 29-30 September, 2011.

[5] A. J. Pontes e A. S. Pouzada, "Ejection force in tubular injection moldings. Part I: Effect of processing conditions," Polymer Engineering and Science, vol. 44, n^ 5, pp. 891-897, 2004.

[6] J. Pontes, A. S. Pouzada, R. Pantani e G. Timtomalio, "Ejection force of tubular injection moldings. Part II: A prediction model," Polymer Engineering and Science, vol. 45, n^ 3, pp. 325-332, 2005.

[7] M. R. Kashani, E. Behazin e A. Fakar, "Construction and evaluation of a new tribometer for polymers," Polym. Test., vol. 30, n^ 3, pp. 271-276, 2011.

[8] J. -Y. Chen e S. -J. Hwang, "Design and fabrication of an adhesion force tester for the injection moulding process," Polym. Test., vol. 32, n^ 1, pp. 22-31, 2013.

[9] A. S. Pouzada, E. C. Ferreira e A. J. Pontes, "Friction properties of moulding thermoplastics," Polymer Testing, vol. 25, n^ 8, pp. 1017-1023, 2006.

General Description

[0020] The present disclosure referred to an autonomous equipment/device that allows the determination of the friction and adhesion forces, and consequently the determination of the coefficient of friction, in similar conditions to the polymer replication processes. Additionally, the equipment/device also allows the measurement of the adhesion between the polymer and the mould material in the same conditions.

[0021] The present disclosure allows the heating of the metallic stamp, or other material, up to the glass transition temperature in the case of amorphous polymers and up to the melt temperature in the case of semi-crystalline polymers. The application of a contact force measured by the equipment, followed by the cooling allowing to perform two type of test, friction force measurement and adhesion force measurement between the two surfaces under study. More specifically, the disclosure ends up solving some problems associated with the existent tests, namely the performance of friction and/or adhesion tests measurements without the need of using a second equipment to proceed with the tests. In addition to allowing to use and define the test parameters of the polymer replication processes that usually have influence in the friction forces and adhesion forces.

[0022] The present disclosure advantages are related with the facility of carrying out tests to evaluate the coefficient of friction between two surfaces also including the required tools to evaluate the adhesion between a polymer surface and other with the construction material of the mould cavities. The use of this disclosure eliminates the need of using instrumented moulds to evaluate these two tribological properties between two surfaces in contact.

[0023] The present disclosure is related with an equipment/device for friction and/or adhesion forces measurement in similar conditions to the demoulding phase in the polymer replication processes. The equipment is indicated to measure the friction and the adhesion forces between two surfaces. The first surface composed by a metal or other material used in moulds for polymer processing is heated to a certain temperature, that depends on the second surface material produced with the polymer under test. After the established temperature is reached the two surfaces are compressed together by means of a contact force applied during the selected time. The cooling is then triggered down to the test temperature, which, when reached allows to perform the friction or adhesion force test. The type of test is selected by the user. The device allows tests to be carried out independently, i.e., without the need of being coupled to another equipment or machine. [0024] The present disclosure relates to a test equipment/device for friction and/or adhesion forces measurement between polymer specimens and a stamp produced with a material used in the polymer replication moulds, with independent functioning, in other words, without the need of using additional equipment.

[0025] An embodiment comprises two parts, one corresponds to the fixed part, which is also divided in two parts with different functions, and a movable part.

[0026] An embodiment, the said fixed part can be composed by two parts with different functions. One of them corresponds to the part that is responsible for the horizontal movement promoted by the motor and by the horizontal movement guide, where the load cell responsible for the friction force measurement is also placed. In the other part, the stamp is attached, held by two screws, and is also responsible for its heating, through electrical resistances, and its cooling, through a compressed air system.

[0027] An embodiment the movable part can be composed forfour guideways that assure the alignment of the fixed part with the plate which supports the motor responsible for the vertical movement. The platform vertical movement is performed through its connection to the vertical motor and the movement facilitate by the vertical guideways. The movable part also comprises the sample holder, where the load cell is attached, which measure the contact force between the two surfaces under test. The load cell is responsible for the adhesion force measurement and it is connected to the platform and to the sample holder, four guideways are responsible for the sample holder movement regarding the platform and the two stroke limiters are responsible for limiting the compression movement of the load cell preventing it to be damage during the contact force application.

[0028] An embodiment the contact force applied at the interface between the surface of the stamp and the polymer specimen placed in the sample holder being measured by the load cell and the coefficient of friction determined dividing the force measured by the load cell by the force measured at the load cell.

[0029] An embodiment, the descendent movement by means of the motor until the correct contact between the horizontal guideway and the rail positioned in the sample holder. The contact force is preferably applied when these elements are in the correct position. [0030] The present disclosure also relates to a test method for coefficient of friction measurement between the metal stamp or other material used in the production of replication injection moulds, and a sample previously produced with a polymer with the equipment required dimension, which allows to perform test simulating the process conditions that have influence in the friction of the polymer replication moulds. The developed equipment allows to vary the processing conditions, such as, the type of tested materials, sliding speed, both vertically and horizontally, temperature at the interface between the two materials, contact time, contact force, stamp surface topography under test, thus allowing the study of friction that exists for example in the replication of polymers in the injection moulding process technique at the demoulding of the polymer sample from the mould. This method may use the equipment accordingly to referred embodiments and comprises:

• Easy of change both test elements or samples, i.e., of the stamp and the polymer sample, with the platform rising to the maximum height that is limited by the motor and aided by the vertical guides;

• Choose the type of test to perform at the interface, that is, choosing between the tests of friction force or adhesion force measurement;

• Control all the movements and test conditions using the controller;

• Establish the test conditions from the interface and controlled by the equipment control unit, thus the test conditions are maintained during the performed test. The test parameters that it is possible to control are as follows: heating temperature, replication and test temperature, horizontal sliding speed or speed to determine the friction force, vertical speed or speed for adhesion force measurement, contact force at the interface between both materials under test and contact time;

• At the beginning of the test, the electrical resistances are activated heating the surface stamp, the vertical movement being promoted by the motor , for the contact of both surfaces, initiated when the defined temperature as the contact temperature is reached. The movement stops when the contact force previously specified is reached and maintained for the time established by the user, being this contact force measured by the load cell; • Decrease of the stamp temperature to the test temperature, i.e., stop of the heating elements inserted in the block, the cooling is triggered by means of compressed air by a system also placed in the block until the set temperature is reached for the start of the test;

• After reaching the test temperature, is performed the selected test, or friction or adhesion. If the selected test was the friction force measurement, the motor responsible for the horizontal movement activates the movement for the friction force measurement, on the contrary if the adhesion for measurement test was selected the ascendent movement, promoted by the motor starts;

• Following the performance of any of the tests the platform recedes to the initial position, which allows the polymer sample exchange.

[0031] An embodiment, the test method can be characterized by obtaining the direct adhesion force measurement by the load cell and the coefficient of friction being calculated by dividing the maximum value measured by the load cell by the contact force measured by the load cell.

[0032] An embodiment, the test method can be characterized for the stamp for sufficiently heating the polymer specimen surface placed in the sample holder, to allow the replication of the stamp surface into the polymer sample surface, this temperature should be above the melting temperature in the semi-crystalline polymers and above the glass transition temperature in the case of amorphous polymers.

[0033] It is also disclosed a device for measuring friction and adhesion between two surfaces, a surface of a polymer sample and a surface of a stamp, in contact for polymer replication processes, comprising: a support frame; a stamp holder attached to the support frame for receiving a stamp and comprising means for heating and cooling the stamp; a horizontally displaceable platform comprising a first load cell for measuring the sample resistance force to sliding of the horizontally displaceable platform; a sample holder for receiving the polymer sample; a vertically displaceable platform coupled to the sample holder for bringing into contact said surfaces of the stamp and the polymer sample; a second load cell attached between the sample holder and the vertically displaceable platform for measuring an adhesion force between said surfaces of the stamp and the polymer sample; a third load cell comprised in the sample holder for measuring a contact force between said surfaces of the stamp and the polymer sample.

[0034] In an embodiment, the vertically displaceable platform comprises at least four guideways for vertically guiding the sample holder and at least two stroke limiters for limiting compression of the second load cell by the vertically displaceable platform.

[0035] In an embodiment, the first load cell is attached toa horizontal displacement motor (9) for horizontally displacing the horizontally displaceable platform.

[0036] In an embodiment, the sample holder comprises a rail arranged to be placed a height to fit with the horizontal guideway for measuring the contact force between surfaces of the stamp and the polymer sample in contact.

[0037] In an embodiment, the horizontally displaceable platform comprises a horizontal guideway for guiding a horizontal movement of the sample holder in relation to the stamp.

[0038] In an embodiment, the sample holder comprises a rail arranged to fit with the horizontal guideway for guiding the horizontal movement of the sample holder in relation to the stamp for obtaining a contact force between surfaces of the stamp and of the sample.

[0039] In an embodiment, the contact force between surfaces of the stamp and the polymer sample is applied when the rail and with the horizontal guideway are completely aligned, that position corresponds to that where guideway is able to put the sample holder at the position zero regarding the stamp, otherwise the friction test can be performed correctly.

[0040] In an embodiment, the contact force between the surfaces of the stamp and of the sample is applied when the rail and the horizontal guideway are aligned, otherwise it is impossible to achieve the correct replication of the stamp into the polymer sample.

[0041] In an embodiment, said device further comprising a control system for controlling and processing friction and adhesion forces between two surfaces in contact.

[0042] In an embodiment, the control system can be arranged to determine a coefficient of friction by dividing the force measured by the first load cell by the contact force measured by said third load cell. [0043] In an embodiment, the stamp holder comprises electric resistances or resistances placed inside the said stamp holder for heating the stamp.

[0044] In an embodiment, the stamp holder further comprises a compressed air duct or ducts placed inside the said stamp holder for cooling the stamp.

[0045] In an embodiment, the stamp holder further comprises a vortex system and a system for stamp temperature measurement for heating and the cooling systems being arranged by individual systems placed inside the stamp holder.

[0046] In an embodiment, the control system is arranged for: processing a friction and adhesion forces signed for controlling the friction and adhesion forces in real time by controlling the motion of the vertically displaceable platform, in particular for stopping the motion of the stamp to prevent causing defects to the polymer sample when a predetermined force is reached in one or more of the load cells.

[0047] In an embodiment, the second load cell and the third load cell may comprise different capacities and sensibilities, preferably the second load cell may have a lower capacity and higher sensibility than the third load cell.

[0048] In an embodiment, the polymer sample is polypropylene (PP), polycarbonate (PC), polystyrene (PS), or combinations thereof.

[0049] In an embodiment, the stamp is embossed, in particular metallic, preferably steel, cooper alloys, epoxy resins, or combinations thereof.

[0050] In an embodiment, the stamp holder comprises dimensions between 45 - 60 x 8 - 60 x 15- 30 mm, preferably 55 x 8 x 19 mm.

[0051] In an embodiment, the sample is a sample of an injection moulded material.

[0052] In an embodiment, it is also disclosed a method for measuring friction or adhesion between two surfaces, a surface of a polymer sample and a surface of a stamp, in contact for polymer replication processes, using a device according to any of the embodiments, comprising the steps of: heating the stamp through means for heating comprised in the stamp holder, in particular at a predetermined heating temperature preferably 70° to 250°C; pressing the stamp heated against the polymer sample using the vertically displaceable platform up to a predetermined force as measured bythe third load cell, in particularduringa predetermined duration of time, preferably 30 to 60 seconds; cooling the stamp, optionally using the compressed air duct or ducts placed inside the said stamp holder, in particular at a predetermined cooling temperature; for measuring friction, moving horizontally the horizontally displaceable platform and measuring the first load cell and the third load cell; for measuring adhesion, moving upwards the vertically displaceable platform and measuring the second load cell.

Brief Description of the Drawings

[0053] The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of invention.

[0054] A person skilled in the art will better understood all the features, characteristics, advantages, technical and functional improvements of the invention, from the schematic figures that complement the present application, which can preferably be interpreted together with the detailed description bellow, made as a title merely exemplary of the preferred embodiments of the invention, without any intention of limiting the scope of protection.

[0055] Figure 1 is a schematic representation a contact force, a sliding force and a friction force between a stamp and a polymers sample, wherein A represents a contact force; B represents a friction force; C represents a sliding force and D represents a stamp and E represents a polymer sample.

[0056] Figure 2 is a schematic representation of a general view of the equipment of the present invention.

[0057] Figure 3 is a schematic representation of a perspective view of the equipment of the present invention.

[0058] Figure 4 is a schematic representation of a front perspective view of one of the parts of the equipment of the present invention. Specifically, the place where the polymer sample is placed.

[0059] Figure 5 is a front perspective view of other part of the equipment. Specifically, the place where the stamp from the mould material is placed.

IB Detailed Description

[0060] The present disclosure is referred to an autonomous test equipment for measuring the friction and the adhesion forces, and consequently the coefficient of friction determination, in similar conditions to the polymer replication processes. Additionally, the equipment/device of the present disclosure also allows the measurement of the adhesion component between the polymer samples and a sample from a material used in the polymer replication moulds, with an independent operation, in other words, without the need of additional equipment.

[0061] In general terms, the equipment/device of the present disclosure comprises two parts: (i) a first part that corresponds to a fix part, which is also divided in two parts with distinct functions; and (ii) a mobile part.

[0062] In an embodiment, the equipment/ device of the present disclosure allows the heating of the stamp produced by steel, or other material, above the glass transition temperature in the case of an amorphous polymer and above the melt temperature in the case of a semi crystalline material. A contact force application measured by the equipment/device, followed by cooling allowing the performance of two tests, measurement of the friction force and adhesion force between the two surfaces in study.

[0063] In an embodiment, the way the equipment/device of the present disclosure was built allows the variation of most of the processing conditions used in the replication processes, as example, in the injection moulding process and that have influence in the ejection forces. Thus, it allows the variation of:

Types of materials under test;

Heating (replication) and demoulding (test) temperature, both dependent on the polymeric material;

Sliding speed between the two surfaces, both horizontally (for friction measurement), as vertically (for adhesion force measurement and contact pressure application);

Contact time and contact force;

Topography of the stamp surface under study, in order to allow the friction study, such as, the existent in the polymer replication in the part demoulding using the injection moulding process. [0064] Besides, it includes three different load cells for contact pressure, sliding force (friction force) and adhesion force measurement at the interface between both materials.

[0065] It also allows perform adaptations related with both samples size, as it allows an easy change of both sample holders.

[0066] In an embodiment, the equipment/device of the present disclosure allows that the test to be carried out under similar conditions as those used, for example, in the polymers injection moulding process, namely the contact temperature, the test temperature, the sliding speed, the contact pressure and time, and the type of materials.

[0067] In an embodiment, the equipment/device of the present disclosure is based on an equipment that heats the specimen (stamp) produced with a material applied to the production of replication moulds, up to a replication temperature, which is previously defined according with the polymer to test. For a preferred embodiment of the present disclosure, the used stamps must be machined in the mould making material and the polymer samples (substrate) must be previously produced in the equipment required dimensions. For a preferred embodiment of the present invention, the stamp dimensions are about 55 x 8 x 19 mm. However, a person skilled in the state of the art recognizes that the values indicated here are not limitative to the present invention and are preferential values that may vary according to the equipment used.

[0068] In an embodiment, after the heating, the said stamp is pressed against the previously polymer moulded part (substrate), for friction or adhesion force measurement between the surfaces in contact, in other words, between the stamp and the polymer part. The polymer can be selected between the group: polypropylene (PP), polycarbonate (PC), polystyrene (PS), among others. More specifically, the said metallic stamp, preferably steel, cooper alloys or an insert of any other material (epoxy resins), generally of the same material used to produce the mould cavities of the tool used in the polymer replication processes.

[0069] In an embodiment, the stamp is heated up to the replication temperature. Generally, this replication temperature is related to the polymeric material under test, so a person skilled in the art recognizes that in general the value of the replication temperature is up to the glass transition temperature in the case of amorphous polymers, while in the case of semi crystalline polymers these values need to be higher than its melt temperature. After the heating process the polymer specimen surface is forced to meet the stamp surface maintaining a certain force using an electric motor for a pre-defined time by the user for this force application.

[0070] In an embodiment, after the pre-defined time for the contact force application is reached, the cooling of the metallic insert is initiated, which when reaching the test temperature, that is, the temperature at which the polymer subjected to the replication processes can be demoulded without suffering any type of defect related with this process phase, and a test is performed: friction test or adhesion test. In the equipment/device disclosed here it is possible to vary different conditions associated to the friction and adhesion, including, the contact, removal and sliding speed, replication and test temperatures, replication time and the contact force between the two surfaces.

[0071] In an embodiment, the schematic representation of the developed equipment/device is shown in Figure 2. It is presented in Figure 1, the contact between the stamp and the polymers sample, along with the force diagram in the contact during the friction force measurement during the movement of the polymer sample. The equipment/device of the present disclosure comprises a base formed by a support frame 1 that supports the entire structure of the equipment/device, including the vertical and horizontal profiles (14 and 16), preferably in aluminium to support and secure the security box (not shown in Figure 2), which consists of acrylic plates attached to the profiles (14 and 16), all around the equipment/device. All other equipment/device components were placed on the base, i.e., support frame 1.

[0072] In an embodiment, the equipment/device of the present disclosure is divided into a movable part and a fixed part, the mentioned base, in addition to have elements to control all the movements, i.e., the motors for the vertical and horizontal (11 and 9) movements and the forces measurements, where the three load cells (18, 19 and 10) are inserted by means of a control unit 27 where all the electric connections and the user interface 26 are located.

[007B] In an embodiment, the fixed part of the equipment/device of the present disclosure is divided in two different zones. The first one is provided with a motor 9 responsible for the substrate movement. The said motor is supported by steel plates 17, that in turn are attached to the equipment base, i.e., support frame 1. In order to measure the resistance force to the sliding for the coefficient of friction measurement, the equipment/device is still provided by a load cell 19, responsible by the friction force (sliding) measurement, that is linked to the motor 9 and to the guideway 25 that supporting the horizontal movement.

[0074] In an embodiment, a second zone of the fixed part is composed by a block 6, that have two functions: (i) give the required heigh to the sample holder 7, where the stamp 8 is hold using horizontal screws 12; and (ii) responsible for the heating using electric resistances placed inside the block 6 and cooling by the use of a compressed air system also placed inside the block 6.

[0075] In an embodiment, more specifically, the heating and the cooling are promoted by individual systems placed inside the block 6, such as a resistance system for heating, a cooling system working with compressed air, by means of a vortex system and a system for stamp temperature measurement.

[0076] In an embodiment, the movable part of the equipment/device of the present disclosure contains further elements that are responsible for the vertical movement, forces measurement and sample holder 21 for the polymer part. Specifically, the motor 11 responsible for the vertical movement is attached using screws to the plate 5, which in turn is supported for at least four guideways 2 responsible for the support of the previous components, motor 11 and the plate 5 two elements without any movement, alignment of the fixed part with the plate 5 and for the guidance of the platform 3 where are attached, by means of at least four guideways 23 and screws the remain elements of the movable part, including the sample holder 21, the load cell 18, the shaft motor 11 and the movement facilitated by the vertical guides 2. In the plate 5 there also present four track bushings 4 that facilitates the movement of the platform without friction between the plate 5 and the vertical guides 2.

[0077] In an embodiment, the movable part of the equipment/ device of the present disclosure is provided with a sample holder 21, where are positioned at least two load cells (18 and 20). A first load cell 18 is positioned between the movable platform 3 and the sample holder 21 and it is responsible for measure the adhesion force between the surfaces. In other words, the stamp 8 and the polymer sample (substrate) and a second load cell 20 responsible for measuring of the contact force between the said surfaces, this being placed in the sample holder 21, immediately above the local where the polymer sample is located. [0078] In an embodiment, as the load cells (18 and 20) have different capacities, for a preferred embodiment of the present disclosure the load cell 18 has a lower capacity, and thus, it is connected to the platform 3 and the sample holder 21 by means of at least four guides or guideways 23 that are responsible for the movement of the sample holder 21 in relation to the platform 3. There are also at least two columns in the movable part of the equipment/device, which act as stroke limiters 24, in order to limit the compression of this load cell 18 preventing it from being damage during the application of the contact force.

[0079] In an embodiment, the applied contact force at the interface between the stamp 8 and the polymer sample located in the sample holder 21 is measured by the said load cell 20 and the coefficient of friction is determined by dividing the force measured by the load cell 19 by the contact force measured by this load cell 20.

[0080] In an embodiment, the touch between the polymer sample and the stamp 8 is promoted by means of a rail 13 in the upper sample holder 21 that fits the guide 25 to help the horizontal movement. The movement towards the touch of the platform 3 preferably only happens if these two elements, sample holder 21 and guide 25 are perfectly fitted, and the contact force is preferably only applied when these elements are in the correct position.

[0081] In an embodiment, additionally, the equipment/device of the present disclosure facilitates the exchange of both test elements, i.e., the stamp 8 and the polymer sample, with the platform 3 rising from 0 to 200 mm, regarding the stamp surface, and is limited by the motor 11 aided by the vertical guides 2.

[0082] In an embodiment, the equipment/device of the present disclosure also allows to choose the type of test to perform and establish the test conditions that will be used in the equipment interface 26, this is, choose between the friction forces measurement test or adhesion force measurement test; control of all the movements and test conditions from the controller 27.

[0083] In an embodiment, in the initialization of the test, the electrical resistances are activated heating the surface stamp 8, being the vertical movement provided by the motor 11, for the contact between both surfaces, stamp and substrate (polymer sample), initiated when the established replication temperature is achieved. The movement stops when the contact force previously specified is reached up to a maximum value of 1500 N and is maintained during the user established time, being that contact force measured by the load cell 20. It should be noted that the parameters here mentioned are not limiting aspects of the present disclosure scope and may vary according to the user's demand.

[0084] cooling of the stamp 8 down to the test temperature (dependent on the used polymer), i.e., stopping the operation of the heating resistances inserted in the block 6 is triggered by the injection of compressed air in a cooling system also placed in the block 6 until the temperature established at the beginning of the test be achieved.

[0085] In an embodiment, after reaching the test temperature, the selected test is initiated, friction or adhesion force measurement. If friction force measurement test was selected, the motor 9 responsible for the horizontal movement trigger the movement for the friction force measurement, on the contrary if the adhesion force measurement test was select the ascending movement promoted by the motor 11 responsible for the vertical movement is initiated.

[0086] In an embodiment, at the end of the test, the platform 3 moves back to the initial position, which allows the exchange of the polymer sample.

[0087] In a preferred embodiment of the present disclosure, the replication of the stamp 8 surface into the surface of the polymer surface occurs when there is sufficient heating of the equipment, this is, when the replication temperature reaches values above the value of the melting temperature in the case of semi-crystalline polymers and above the glass transition temperature in the case of amorphous polymers.

[0088] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0089] The invention described here is not limited to the embodiments and those skilled in the art will realize the any particular feature introduced therein should be understood only as something that has been described to facilitate understanding and have been carried out without departing from the inventive concept described. The limiting characteristics of the object of the present invention are related to the claims that are part of this document. [0090] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above described embodiments are combinable. The following claims further set out particular embodiments of the disclosure.