Brochure: Carbon Additives for Polymer Compounds - Timcal Graphite

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TYpICAL AppLICATIonS FoR TIMREX® GRApHITE And CokE 20 Filled pTFE Polytetrafluoroethylene (PTFE) exhibits a very low coefficient of friction and retains useful mechanical properties at temperatures from -260 to +260 °C for continuous use. The crystalline melting point is 327 °C, much higher than that of most other semi-crystalline polymers. Furthermore, PTFE is nearly inert chemically and does not adsorb water, leading to excellent dimensional stability. On the one hand, these characteristics of PTFE are very useful in the matrix polymer of polymer-based composites which are used in sliding applications. On the other hand, PTFE is subjected to marked cold flow under stress (deformation and creep) and reveals the highest wear among the semicrystalline polymers. However, these disadvantages are very much improved by incorporating suitable fillers, allowing the use of PTFE in fields otherwise precluded to this polymer. The treated PTFE is generally known as filled- PTFE. There are many kinds of filled- PTFE composite because various fillers are incorporated into PTFE and one or more materials can be used simultaneously. Usually, these fillers are in form of powders or fibers intimately mixed with the PTFE. The addition of fillers to the PTFE improves or modifies its properties depending upon the nature and quantity of filler: • remarkable increase in wear resistance; • decrease of deformation under load and of creep; • reduction of thermal expansion; • some types of filler increase the thermal and electric conductivity. Filled PTFE is often not as strong and resilient as virgin PTFE. Sometimes, the filler limits the resistance to chemical agents and modify the electrical properties. TIMREX® GRApHITE And CokE FILLERS In FILLEd-pTFE TIMREX® pC 40-oC Coke TIMREX PC 40-OC Coke is calcined at high temperatures offering low sulphur concentration, low content of oversize particles, high apparent density and high chemical stability against most chemical substances. TIMREX® PC 40-OC Coke is added to the virgin PTFE in a percentage by weight between 10 and 35% along with small percentage of graphite. Compounds made of PTFE and TIMREX® PC 40-OC Coke have excellent wear resistance and deformation strength and compared to the virgin PTFE, they have practically unchanged chemical resistance and friction behaviour. Typical final materials that can be produced with coke filled PTFE are: engineering design components, slide bearings, valve housing and valve seats for chemical applications, piston sealing and guiding elements for dry-running compressors. TIMREX® kS44 Synthetic Graphite NTIMREX® KS 44 is a Primary Synthetic Graphite obtained by the full graphitisation of amorphous carbon materials through the well known Acheson process. The process parameters in the Acheson furnace such as temperatures and residential times are all optimised in order to achieve the perfect degree of crystallinity and the lowest level of impurities whereas others minor adjustments are made during the material sizing and conditioning. The percentage of TIMREX® KS 44 used in the filled PTFE vary between 5 and 15%. TIMREX® KS 44 can be used alone or in combination with glass or coke. TIMREX® KS 44 lowers the coefficient of friction and is, therefore, often added to other types of filled PTFE for improving this property (and also to improve the lifetime of the cutting tools during for instance the production of gaskets and seals). It improves the deformation under load, strength and, to a minor degree the wear. Like coke, it serves well in corrosive environments. PTFE filled with TIMREX® KS 44 are often used in steering and shock-absorber gasket, bearings as well as in slide films for anti-static applications.
InFLuEnCE oF TIMREX®GRApHITE And CokE FILLERS In FILLEd-pTFE Wear resistance virgin PTFE shows much high wear as a result of the destruction of the banded structure due to easy slippage between the crystalline lamellae in the bands. The presence of well distributed carbon particles in the filled PTFE partially avoid the slippage between the crystalline lamellae in the bands and therefore the wear resistance is improved. deformation strength virgin PTFE deformation behaviour is somehow similar to the mechanism previously described. In someway the deformation phenomena could be explained by the tendency of slippage that occurs between the crystalline lamellae. However, in this case the presence of well distributed carbon particles in the filled PTFE offers only a partial explanation to the phenomena because also hardness of these particles is important in determine an improvement of the deformation behaviour. Friction Coefficient the coefficient of friction for various filled PTFE composites is weakly dependent upon the incorporated filler, because a thin PTFE film generally exists at the interface between the body and counter-body. Consequently the coefficient of friction is both similar in the filled PTFE and virgin PTFE. This evidence is true as long as no oversize particles are present in the filler. In fact the presence of oversize particles could lead to a radically modification of the coefficient of friction. Because of that in carbons as well as in other fillers is very important the control of oversize particles. 21 TYpICAL AppLICATIonS FoR TIMREX® GRApHITE And CokE
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Page 3 and 4: Contents EnSACo® Conductive Carbon
Page 5 and 6: Introduction to TIMREX® Graphite a
Page 7 and 8: EnSACo® Conductive Carbon Black fo
Page 9 and 10: EnSACo® Conductive Carbon Black TI
Page 11 and 12: EnSACo® ConduCTIvE CARBon BLACkS I
Page 13 and 14: EnSACo® ConduCTIvE CARBon BLACkS I
Page 15 and 16: nBR ConduCTIvE HoSE CoMpound A B Co
Page 17 and 18: power cables and accessories Conduc
Page 19: Incorporation of graphite powder in
Page 23 and 24: THERMALLY ConduCTIvE poLYMERS Therm

Brochure: Carbon Additives for Polymer Compounds - Timcal Graphite

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