ADDITIVES | SURFACE MODIFICATION
compared with a compound containing 10% PTFE (Figure 3).
“Based on our tests, UMFI 30N and UMFI 30X show good performance in engineering plastics as a wear and CoF control additive,” says Kim. “While it is not as proficient as Shamrock MicroFlon PTFE additive, UMFI will meet non-halogen requirements.”
Table 1: Effect on mechanical properties of blending PA6 with varying amounts of anhydride-modified ETFE (tests carried out according to JIS) Source: AGC Chemicals
Table 1: Effect on mechanical properties of blending PA6 with varying amounts of anhydride-modified ETFE (tests carried out according to JIS) Source: AGC Chemicals
Metal sulphide options Austrian speciality metal sulphides producer Tribotecc has been carrying out a study into how new synthetic types affect tribological properties in high-performance plastics. “The tribological properties of metal sulphides [in] brake components are well established,” researchers say in a recent paper. “Engineered thermoplastic materials like PEEK, PPS and PPA can also benefit from this class of solid lubricants as their tribological properties are improved.” The researchers compared the lubricating
Figure 2: UMFI 30N and 5% UMFI 30X significantly reduce wear rate of polycarbonate, without lowering the CoF, compared with a compound containing 10% PTFE Source: Shamrock Technologies
Figure 3: 5% UMFI 30N or 5% UMFI 30X reduce the wear rate to around zero in PBT and may even produce a negative value due to thermal expansion in the UHMWPE. CoF is not reduced compared with a compound containing 10% PTFE Source: Shamrock Technologies
G176 type) tribometer.
Kim says 5% UMFI 30N or 5% UMFI 30X additive in a PC compound significantly reduces the wear rate without lowering the CoF when compared with a PC compound containing 10% PTFE (Figure 2). In PBT compounds, 5% UMFI 30N or 5% UMFI 30X reduces the wear rate to around zero and may even produce a negative value due to thermal expansion in the UHMWPE, again without lowering the CoF
20 COMPOUNDING WORLD | February 2019
characteristics of two of the company’s binary sulphides (Tribotecc MOS XF and MOS WS 2) with a newly-developed multiphase synthetic metal sulphide (Tribotecc - SLS 22). They used Pin-on- Disc and Ball-on-Plate test equipment and also assessed basic friction behaviour using a Tabor friction tester. Failure analysis of the surfaces was carried out using visible light and scanning electron microscopy to correlate the friction and wear performance. The tests showed that addition of 10% Tribotecc - SLS 22 in PEEK kept CoF on a constant low level while wear rate was significantly improved compared to the base polymer. Significant improvements in wear rate and a slight reduction of CoF were seen in a PPA compound containing 15% glass fibres with 10% solid lubricants (Figure 4). Friction test results (CoF and weight reduction) from a PPS compound with 30% glass fibres with different solid lubricants showed that by adding 10% of Tribotecc - WS 2 and 10% Tribotecc - WS 31, wear was significantly improved. “There is a big potential for improving compounds for tribological applications by using new synthetic metal sulphides as solid lubricants,” the Tribotecc team concluded.
Anti-wear formulations UK-based masterbatch specialist Colloids, part of Tosaf, is also making progress with metal sulphides for tribological applications – specifically molybdenum disulphide (MoS2
) – as well as with
carbon-based additives. It recently added two low-friction and wear-reducing grades to its Pace
www.compoundingworld.com
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