Description

Fuser system member

Technical Field

[0001] The invention pertains to a fuser system member having a fluoropolymer outer layer, to a process for its manufacture and to an image forming apparatus comprising said fuser system member.

Background Art

[0002] The present invention relates generally to an imaging apparatus and fuser components thereof for use in electrostatographic, including digital, apparatuses, in particular in xerographic machines, including color machines.

[0003] In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be the photosensitive member itself, or other support sheet such as plain paper.

[0004] The use of thermal energy for fixing toner images onto a support member is well known and methods include providing the application of heat and pressure substantially concurrently by various means, including notably a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by heating one or both of the rolls, plate members, or belt members. With a fixing apparatus using a thin film in pressure contact with a heater, the electric power consumption is small, and the warming-up period is significantly reduced or eliminated.

[0005] It is important in the fusing process that minimal or no offset of the toner particles from the support to the fuser member take place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in

subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The referred to "hot offset" occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser, and accordingly it is desired to provide a fusing surface, which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.

[0006] Another important method for reducing offset is to impart antistatic and/or field assisted toner transfer properties to the fuser. However, to control the electrical conductivity of the release layer, the conformability and low surface energy properties of the release layer are often affected.

[0007] Known fuser coatings include high temperature polymers such as polytetrafluoroethylene, fluorinated ethylene propylene, fluorosilicone rubber, fluoroelastomers, and the like.

[0008] US 6927006 (XEROX CORPORATION) 09.08.2005 discloses a fuser member having a polyimide substrate and thereover an outer layer comprising a fluorocarbon such as polytetrafluoroethylene (PTFE), fluorinated ethylenepropylene copolymer (FEP), polyfluoroalkoxy (PFA), perfluoroalkoxy polytetrafluoroethylene (PFA TEFLON ^® ), ethylene chlorotrifluoro ethylene (ECTFE), ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene perfluoromethylvinylether copolymer (MFA), and the like, and mixtures thereof.

[0009] US 6951667 (XEROX CORPORATION) 04.10.2005 discloses a fuser member comprising an outer surface made from fluorocarbon elastomer latex, an acid acceptor, an emulsifier and a non-amino based crosslinking agent, e.g. a diepoxy- or disilylalkoxy-based crosslinker.

[0010] These coatings have been found to have adequate release properties and control toner offset sufficiently. However, these coatings tend to loose their

flexibility and elastic deformation with use. Further, these coatings do not maintain a uniform surface. More specifically, the coatings often wear during use and/or become scratched during operation. In addition, these known surfaces often react with the toner and/or oil and/or debris from media, which causes the surface to become dirty and/or contaminated. The surface can, in turn, become physically damaged. The result of these problems is that the fuser member has a reduced useful function and short life. Another problem resulting from release coatings with high friction is unacceptable copy or print quality defects. The high friction often associated with conformable coatings may result in the generation of waves in the media being fused and/or the fuser member itself. This, in turn, results in copies or prints with localized areas of poorer fix and/or differential gloss.

[0011] Some of the above problems have been solved by recent improvements of adding polymer fillers to outer layers. However, the use of polymer fillers has caused other problems such as stripper finger marks present on copies, which leads to failure mode. Other failure modes include an offset failure mode problem. Further, wave defects have resulted.

[0012] Finally, selected fuser rolls of the prior art can only be used at temperatures lower than 200°C, due to their lack of ability of withstanding such high continuous operations. This temperature limitation is a dramatic limiting factor on the speed at which the toner can be fused and thus the operating speed (copies per minute) of a machine employing such a fuser. Obviously it is desirable to increase the speed at which quality copies can be made. To do so it is necessary to utilize surface temperatures greater than the maximum operating temperature of conventional rubber covered fuser roll.

[0013] Therefore, a need remains for fuser components for use notably in electrostatographic machines that have superior mechanical properties, e.g. outstanding flex life enabling deformation and recovery of initial shape during passage of paper sheets, and including the ability to remain clean and uniform during use. A further need remains for fuser coatings having reduced susceptibility to contamination, scratching, and other damage. In

addition, a need remains for fuser components having longer life at continuous operation temperatures of more than 200°C. In addition, a need remains for fuser components with low friction while being resistant to scratching and other damage. Further, although some of the above problems have been solved by the use of improved coatings with polymer fillers, there still remains a need to reduce or eliminate stripper finger failure and offset failure modes, and wave defects.

Disclosure of Invention

[0014] The Applicant has now surprisingly found that these and other needs can be achieved by providing a fuser system member comprising an outer layer comprising a tetrafluoroethylene (TFE) polymer [polymer (F)], said polymer (F) comprising:

- recurring units derived from TFE; and

- from 6.5 to 20 % wt of recurring units derived from at least one perfluoromonomer [monomer (CM)] chosen among:

(i) perfluoroalkylvinylethers complying with formula CF ₂ =CFOR _f1 , in which

R _f1 is a C ₁ -C ₆ perfluoroalkyl, e.g. -CF ₃ , -C ₂ F ₅ , -C ₃ F ₇ and/or

(ii) perfluoro-oxyalkylvinylethers complying with formula CF ₂ =CFOX ₀ , in which X ₀ is a C ₁ -C ₁₂ perfluorooxyalkyl having one or more ether groups, like perfluoro-2-propoxy-propyl; and

(iii) mixtures thereof.

[0015] Thanks to the use as outer layer of a fluoropolymer like polymer (F) possessing outstanding thermal resistance and surface smoothness, the fuser system member can withstand high continuous temperature operations over a long period of time, with practically no deterioration in performances and optimum copy or print quality.

[0016] Moreover, due to the mechanical and anti-wear properties of such material (including modulus and deformation at yield as well as flex life and fatigue resistance), an excellent scratch and wear resistance is achieved, with no need of supplemental filler material or of additional release agents.

[0017] The fuser system of the present invention can be of any suitable configuration. Examples of suitable configurations include a sheet, a film, a web, a foil, a strip, a coil, a cylinder, a drum, a roller, an endless strip, a

circular disc, a belt including an endless belt, an endless seamed flexible belt, an endless seamless flexible belt, an endless belt having a puzzle cut seam, and the like. Specific examples of the fuser system member include a fuser member, a pressure member, a release agent donor member, preferably in the form of a cylindrical roll such as, for example, a fuser roll, a donor roll and a pressure roll. It may also take the form of an intermediate transfer belt.

[0018] The invention also pertains to a process for coating a fuser member with the outer layer comprising polymer (F) as above described.

[0019] Another object of the invention is an image firming apparatus for forming images on a recording medium.

[0020] The outer layer of the fuser system member can completely cover said fuser system member or can partially cover the same. While the invention encompasses all these embodiments, it is generally preferred that the outer layer comprising polymer (F) covers at least the section of the fuser system member which will be exposed during operations to heat and/or wear.

[0021] Monomer (CM) is preferably selected among perfluoroalkylvinylethers complying with formula CF ₂ =CFOR _f1 , in which R _f1 is a C ₁ -C ₆ perfluoroalkyl, more preferably a C ₁ -C ₃ perfluoroalkyl.

[0022] Monomer (CM) is more preferably selected among perfluoroalkylvinylethers complying with formula CF ₂ =CFOR _fr , in which R fr is -CF ₃ (MVE), -C ₂ F ₅ (EVE), -C ₃ F ₇ (PVE), or mixtures thereof.

[0023] Monomer (CM) is most preferably CF ₂ =CFOCF ₃ (MVE).

[0024] Preferably polymer (F) of the invention is free from recurring units other from those derived from TFE and comonomers (i) and/or (ii) as above detailed.

[0025] Thus, polymer (F) preferably consists essentially of:

- recurring units derived from TFE; and

- from 6.5 to 20 % wt of recurring units derived from a monomer (CM) chosen among:

(i) perfluoroalkylvinylethers complying with formula CF ₂ =CFOR _f1 , in which R _f1 is a C ₁ -C ₆ perfluoroalkyl, preferably a C ₁ -C ₃ perfluoroalkyl, e.g. -CF ₃ , -C

₂ F ₅ , -C ₃ F ₇ and/or

(ii) perfluoro-oxyalkylvinylethers complying with formula CF ₂ =CFOX ₀ , in which X ₀ is a C ₁ -C ₁₂ perfluorooxyalkyl having one or more ether groups, like perfluoro-2-propoxy-propyl; and

(iii) mixtures thereof.

[0026] The term "consisting essentially of is understood to mean that the polymer chain is essentially made of recurring units as above detailed. Moieties like end-groups, chain defects, entities derived from other polymerization ingredients like initiators, chain transfer agents can be nevertheless present in polymer (F).

[0027] Polymer (F) is advantageously semi-crystalline.

[0028] The term semi-crystalline is intended to denote a polymer (F) which possesses a detectable melting point. It is generally understood that a semi-crystalline polymer (F) possesses a heat of fusion determined according to ASTM D 3418 of advantageously at least 0.4 J/g, preferably of at least 0.5 J/g, more preferably of at least 1 J/g.

[0029] Semi-crystalline polymers (F) have significant advantages over amorphous products, as they exhibit the required properties, and in particular suitable mechanical properties without additional crosslinking treatments.

[0030] Excellent results were obtained when polymer (F) had a heat of fusion (δH f) of 8 to 27 J/g, preferably of 12 to 24 J/g.

Heat of fusion has been determined by differential scanning calorimetry (DSC), according to ASTM D 3418.

Polymers (F) complying with such requirement were found to well behave as outer layer in fuser system member, as they possess at the same time suitable mechanical resistance (in particular outstanding flex life) in a very broad MFI domain, but also outstanding surface properties (smoothness and release capabilities).

[0031] Polymers (F) possess improved flex-life/processability and surface smoothness compromise over the polymer used in the fuser member system of the prior art. It is generally understood that higher flex life capabilities can be obtained increasing molecular weight, that is to say at lower melt flow index (MFI).

[0032] Now, the Applicant has surprisingly found that polymer (F), having at given

MFI (e.g. at a given processability level), higher flex life over the polymers of the fuser system member of the prior art, makes it possible to easily process said polymer (F) with high throughput and substantial energy savings for yielding a fuser system member complying with the outstanding requirements in terms of mechanical properties and still possessing outstanding surface characteristics. [0033] Polymer (F) advantageously possesses a melting point (T _m2 ) from 230°C to 280 ⁰ C, measured according to ASTM D 3418. [0034] Polymer (F) advantageously possesses a melt flow index (MFI) of 1 to 100 g/10 min, when measured according to ASTM D 1238 standard. [0035] Polymers (F) complying with such requirements were found to well behave as outer layer in fuser member, as they possess at the same time suitable thermal resistance and mechanical properties. [0036] It is essential for polymer (F) to have an amount of recurring units derived from monomer (CM) comprised from 6.5 to 20 % wt. [0037] When the polymer (F) comprises less than 6.5 % wt of recurring units derived from monomer (CM), its flex-life value are poor and material lacks of mechanical properties. [0038] When polymer (F) comprises more than 20% wt of recurring units derived from monomer (CM), its melting point is too low and the material is not able to sustain high continuous operating temperature (up to e.g. 200°C). [0039] Polymer (F) comprises at least 6.5 %, preferably at least 7 %, more preferably at least 7.5 % by weight of recurring units derived from monomer (CM). [0040] Polymer (F) comprises at most 20 %, preferably at most 16 %, more preferably at most 12 % by weight of recurring units derived from monomer (CM). [0041] Excellent results have been obtained with a polymer (F) comprising from

7.5 to 12 % wt of recurring units derived from MVE. [0042] The outer surface of the fuser member is from about 5 to about 1000 micrometers thick, preferably about 15 to about 500 micrometers thick. [0043] The fuser system member of the invention advantageously comprises a

supporting substrate such as a heated cylindrical fuser roll, film or belt having a fusing outer surface which is generally backed by a cylindrical pressure roll forming a fusing nip there-between.

[0044] The fuser system member substrate on which the polymer (F) is coated may be a roll, belt, flat surface or other suitable shape used notably in the fixing of thermoplastic toner images to a suitable substrate. It may take the form of a cylindrical sleeve, a drum, a belt or an endless belt. Typically, the fuser system member substrate is made of a hollow cylindrical metal core, such as copper, aluminium, steel, or certain plastic materials chosen to maintain rigidity, structural integrity, as well as being capable of having the polymer (F) coated thereon and adhered firmly thereto.

[0045] Preferred substrate materials include in the case of roller or film-type substrates, metals such as aluminium, stainless steel, steel, nickel and the like.

[0046] In the case of film-type substrates, preferred substrates include high temperature plastics that are suitable for allowing a high operating temperature (i.e., greater than about 80°C, preferably greater than 200° C), and capable of exhibiting high mechanical strength. In embodiments, the plastic has a flexural strength of from about 2,000,000 to about 3,000,000 psi, and a flexural modulus of from about 25,000 to about 55,000 psi. Plastics possessing the above characteristics and which are suitable for use as the substrate for the fuser members include epoxy; polyphenylene sulfide such as that sold under the tradenames FORTRON ® available from Hoechst Celanese, RYTON ^® R-4 available from Phillips Petroleum, and SUPEC ^® available from General Electric; polyimides such as polyamideimide sold under the tradename TORLON ^® 7130 available from Solvay Advanced Polymers; polyketones such as those sold under the tradename KADEL ^® E1230 available from Solvay Advanced Polymers, polyether ether ketone sold under the tradename PEEK 450GL30 from Victrex, polyaryletherketone, and the like; polyamides such as polyphthalamide sold under the tradename AMODEL ^® available from Solvay Advanced Polymers; polyethers such as polyethersulfone, polyetherimide, polyaryletherketone, and the like; polyparabanic acid; and

the like; liquid crystalline resin (XYDAR ^® ) available from Solvay Advanced Polymers; ULTEM ^® available from General Electric; ULTRAPEK ^® available from BASF; and the like, and mixtures thereof. Other suitable substrate materials include fluoroelastomers such as those sold under the tradename VITON ^® from DuPont or TECNOFLON ^® from Solvay Solexis; silicone rubbers, and other elastomeric materials. The substrate may also comprise a mixtures of any of the above materials

[0047] In one embodiment, the core, which may be an aluminium cylinder, is degreased with a solvent and cleaned with an abrasive cleaner prior to being primed with a primer, which may be sprayed, brushed or dipped, followed by air drying under ambient conditions for thirty minutes and then baked at approximately 150° C for about 30 minutes.

[0048] A fuser member according to a preferred embodiment of the invention is shown in FIG. 1 where the numeral 1 designates a fuser member comprising an outer layer 2 comprising polymer (F) upon a suitable base member 3, a hollow cylinder or core fabricated from any suitable metal, such as aluminium, anodized aluminium, steel, nickel, copper, or a plastic material such, e.g. a polyimide, and the like, having a suitable heating element 4 disposed in the hollow portion thereof which is coextensive with the cylinder.

Backup or pressure roll 5 can cooperate with fuser member 1 to form a nip or contact arc 11 through which a copy paper or other substrate 9 passes such that toner images 10 thereon contact outer surface 2 of fuser member 1. As shown in FIG. 1 , the backup roll 5 has a rigid core 7, e.g. a steel core, with an outer surface or layer 6 thereon. The outer surface layer of the backup or pressure roll comprises advantageously polymer (F) as above described.

[0049] The invention also pertains to a process for the manufacture of the fuser system member as above defined.

[0050] The process of the invention comprises advantageously coating a fuser member system substrate with the outer layer comprising polymer (F).

[0051] The outer polymer (F) layer can be coated on the substrate using any suitable known manner. Typical techniques for coating such materials on

include liquid and dry powder spray coating, dip coating, wire wound rod coating, fluidized bed coating, powder coating, electrostatic spraying, sonic spraying, blade coating, casting, co-extruding, extruding and shrinking pre-formed shrinkable tubes, extruding and welding pre-formed films or sheets, and the like. It is understood that for fuser system member under the form of belt, wherein the substrate is typically a plastic substrate, co-extrusion, casting and/or welding pre-formed films are preferred techniques for applying the outer layer of polymer (F). In case of fuser system member under the form of a cylinder, it is advantageous to assembly the outer layer comprising polymer (F) by introduction of said fuser system member in a shrinkable pre-formed tube of polymer (F); subsequently, heat treatment advantageously enables shrinkage of said tube onto the fuser system member.

[0052] Optionally, any known and available suitable adhesive layer may be positioned between the outer layer and the substrate.

[0053] The invention also pertains to an image forming apparatus for forming images on a recording medium including:

- a charge-retentive surface to receive an electrostatic latent image;

- a development component to apply toner to the charge-retentive surface to develop the electrostatic latent image to form a developed image on the charge retentive surface;

- a transfer component to transfer the developed image from said charge retentive surface to a substrate;

- and a fuser system member to fuse the developed image to said substrate in which said fuser member comprises an outer layer comprising polymer (F) as above described.

[0054] The present invention will be described in more detail with reference to the following examples whose purpose is merely illustrative and not limitative of the scope of the invention.

[0055] Example 1 - Manufacture of polymer (F) samples

[0056] POLYMERIZATION RUNS

[0057] Polymer (F-1) (TFE/PMVE 95/5 (molar ratio) (91.95/8.05 by nominal weight))

[0058] In a 22 litres AISI 316 steel vertical autoclave equipped with baffles, and stirrer working at 400 rpm, were introduced 13.9 I of demineralized water, 136 g of a microemulsion prepared according to US 4864006 (AUSIMONT SPA ) 05.09.1989 . Then the temperature was raised to reaction temperature of 75°C; once this set point temperature achieved, 0.22 absolute bars of ethane and 3.8 absolute bars of perfluoro methylvinylether were introduced. A gaseous mixture of TFE/PMVE in a molar nominal ratio of 95/5 was added until reaching a pressure of 21 absolute Bars.

[0059] The composition of the gaseous mixture present in the autoclave head-space was analyzed by gas chromatography (G. C). Before starting polymerization, the gaseous phase was found to consist of (molar percentages): 79% TFE, 20.5% MVE and about 0.5% Ethane. 110 cc of a potassium persulphate (KPS) 0.0296 M solution were fed to start the polymerization.

[0060] The polymerization pressure was maintainned constant by feeding the above mentioned monomeric mixture; when 880Og of the mixture have been fed, feeding was interrupted and, while maintaining set point temperature, the pressure was enabled to decrease down to 9 abs. bars. Then the reactor was cooled to room temperature, the latex was descharged and coagulated with HNO ₃ (65% by weight). The polymer was then washed with demineralized water and dried at 220°C. So obtained powder was then pelletized.

[0061] Polymer (F-2) (TFE/PMVE 93.9/6.1 (molar ratio) (90.35/9.75 by nominal weight))

[0062] Same procedure as for polymer (F-1) was repeated, but using:

- a gas mixture TFE/MVE (93.9/6.1 mol/mol)

- an ethane initial partial pressure of 0.23 absolute Bars.

- an initial MVE partial pressure of 5.2 absolute Bars.

[0063] The gaseous phase before starting polymerization was found by G. C. to consist of (molar percentages): 69% TFE, 30.4% PMVE and about 0.6% Ethane.

[0064] Polymer (F-3) (TFE/PMVE 94.7/5.3 (molar ratio) (91.5/8.5nominal weight

ratio))

[0065] Same procedure as for polymer (F-1) was repeated, but using:

- a gas mixture TFE/MVE (94.7/5.3 mol/mol)

- an ethane initial partial pressure of 0.24 absolute Bars.

- an initial MVE partial pressure of 4 absolute Bars;

- an amount of microemulsion of 160 g;

- an amount of a KPS solution (0.0148 M) of 140 ml.

[0066] The gaseous phase before starting polymerization was found by G. C. to consist of (molar percentages): 74.7% TFE, 24.5% MVE and about 0.8% Ethane.

[0067] Polymer (F-4) (TFE/PMVE 94.8/5.2 (molar ratio) (91.65/8.35 nominal weight ratio))

[0068] Same procedure as for polymer (F-1) was repeated, but using:

- a gas mixture TFE/MVE (94.8/5.2 mol/mol)

- an ethane initial partial pressure of 0.26 absolute Bars.

- an initial MVE partial pressure of 4 absolute Bars;

- an amount of microemulsion of 160 g;

- an amount of a KPS solution (0.0148 M) of 125 ml.

[0069] The gaseous phase before starting polymerization was found by G. C. to consist of (molar percentages): 77.5% TFE, 21.7% MVE and about 0.8% Ethane.

[0070] Polymer (F-5) (TFE/PMVE 94.5/5.5 (molar ratio) (91.2/8.8 nominal weight ratio))

[0071] Same procedure as for polymer (F-1) was repeated, but using:

- a gas mixture TFE/MVE (94.5/5.5 mol/mol)

- an ethane initial partial pressure of 0.26 absolute Bars.

- an initial MVE partial pressure of 4.2 absolute Bars;

- an amount of microemulsion of 160 g;

- an amount of a KPS solution (0.0148 M) of 125 ml.

[0072] The gaseous phase before starting polymerization was found by G. C. to consist of (molar percentages): 74.3% TFE, 25% MVE and about 0.7% Ethane.

[0073] Polymer (F-6) (TFE/PMVE 94.6/5.4 (molar ratio) (91.5/8.5 nominal weight

ratio))

[0074] Same procedure as for polymer (F-1) was repeated, but using:

- a gas mixture TFE/MVE (94.6/5.4 mol/mol)

- an ethane initial partial pressure of 0.37 absolute Bars;

- an initial MVE partial pressure of 4.05 absolute Bars;

- an amount of microemulsion of 160 g;

- an amount of a KPS solution (0.0148 M) of 125 ml.

[0075] The gaseous phase before starting polymerization was found by G. C. to consist of (molar percentages): 73% TFE, 26% MVE and about 1 % Ethane.

[0076] Table 1 here below summarizes compositions and melting properties of polymer (F-1) to (F-6) as above detailed, and, to the sake of comparison, corresponding properties of selected commercially available fluoropolymer materials, which have been used in the past for this application. Hexafluoropropylene (HFP) and EVE content in prior art material has been determined according to the method described in US 5677404 (DU PONT) 14.10.1997 . PVE content was determined according to an internal IR method, measuring optical densities of spectral bands centred at 995 cm ^"1 and 2365 cm ^"1 , according to the following formula: I

PVE (% wt) = 995 cnT ¹ : 0.99

2365 cm

[0077]

Table 1

[0078] Polymers listed in table 1 here above were processed for yielding pellets by extrusion on a twin-screw extruder (Braebender). [0079] The pellets were extruded for obtaining small diameter pipes using an extruder having a 45 mm diameter. The extruder geometrical features, summarized here below, yielded a DDR around 20:

Die diameter: 53,7 mm

Tip diameter: 43.6 mm

Tube external diameter: 12 mm

Polymer thickness = 1 mm [0080] The set-point temperature profiles have been summarized in table 2; all samples were extruded at a rate of 15 rpm. [0081]

Table 2

[0082] Table 3 here below draws a comparison between mechanical properties and surface properties of polymers as above described, as determined on specimens punched out either from plaques obtained by compression moulding or from pipes extruded as above detailed.

[0083] Flex-life was determined on compression moulded film having thickness 0.3 mm according to ASTM D 2176 standard.

[0084] Determination of surface roughness was determined by atomic force microscopy (AFM) technique on specimens from above mentioned extruded pipes, using a microscope Autoprobe CP (Parker Instruments) working in contact mode at room temperature. Parameter R _a (average arithmetic roughness) was calculated by averaging 3 measurements with flattening by order 1 or 2 from square AFM pictures having dimensions in a range 20-40 μm.

[0085]

Table 3

[0086] Data summarized in Table 3 well demonstrate that polymer (F) are more suitable for be used as outer layer in fuser member systems over traditional fluoropolymer materials as they possess improved mechanical properties/surface smoothness compromise. It sorts out that either at a given flex life level (e.g. 60 000-90 000 cycles), polymers (F) show reduced surface roughness and higher MFI (hence improved processability), or that for a given surface roughness level, polymers (F) have enhanced mechanical resistance (in particular longer flex life).

[0087] Example 2 - Assembling fuser system member

Polymer (F-1) as above described is extruded to yield a heat shrinkable tubing that has been expanded mechanically to slide over a cylindrical fuser member. The heat shrinkable tubing diameter is selected so as it easily slips over full fuser length insuring that it will shrink to the fuser diameter.

[0088] A multi-layer fuser member comprising a metal core is introduced in polymer (F-1) tubing and then heated to shrink down to a tight fit that will not fall off. To insure a smooth, uniform covering without wrinkles, hot air guns are used for uniformly heating the assembly while rotating the fuser member at a fairly uniform speed. The outer layer of polymer (F-1) is finally allowed to slowly cool. So obtained assembly comprising an outer layer of polymer (F-1) is then used as a fuser member in an electrophotographic process.

[0089]