ADDITIVES | SURFACE MODIFICATION
PPS:PTFE blend cuts the dynamic coefficient of friction in half and improves the wear resistance by a factor of three (Figure 1). Keller says that PTFE tends to agglomerate during the injection moulding process, but that adding a small amount of Fluon+ PFA EA 2000 can help reduce this effect. The result is better PTFE dispersion and hence better tribological performance. “This should also allow compounders to maintain the tribological performance at a given level with a reduced amount of PTFE lubricant with the benefit of better mechanical properties of the compound and better processability,” Keller says. A second option is the replacement of the PTFE lubricant with an anhydride-modified fluoropolymer, Keller says. Various polymers have been tested by AGC Chemicals. Table 1 shows the results of a pure PA6 vs PA6 blended with 5, 10 and 20% of an anhydride modified ETFE. “The advan- tage is the improved wear resistance and impact strength with a moderate compromise on mechani- cal properties only,” he says. A top layer made of an anhydride-modified fluoropolymer film can also be used to achieve improved tribological perfor- mance at the surface of coextrusions or laminates, he adds.
The UHMWPE alternative Shamrock Technologies claims leadership in production of PTFE micropowders. It offers a wide range of products made from natural prime as well as recycled PTFE and produces an extensive variety of particle sizes, molecular weights, and thermal stability. With the ongoing trend to find non- halogenated solutions for all sorts of applications – flame retardance and pigmentation being in the vanguard – Shamrock has now developed a halogen-free anti-wear additive for engineering plastics by proprietary processing of ultra-high molecular weight polyethylene (UHMWPE) powder with an average particle size of between around 30 and 50 microns. Dr Hyunseog Kim, the company’s R&D manager, discussed the development at the AMI conference, explaining that the newly developed additives in the Shamrock Technologies’ UMFI series are available in standard and modified versions (UMFI 30N and 30X respectively). In tests on wear and coefficient of friction (CoF) reduction performance in engineering plastics, two different polymers – polycarbonate (PC) and polybutylene terephthalate (PBT) – were compounded with both additives. Samples were tested on a Block on Ring (ASTM
Figure 1: Wear and friction test results according to JIS K-7218 (disc test) show that adding 1phr of anhydride- functionalised Fluon+ PFA EA2000 into an 80:20 PPS:PTFE blend has major effects on CoF and wear resistance Source: AGC Chemicals
18 COMPOUNDING WORLD | February 2019
www.compoundingworld.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70
