FORMULATION | FRICTION AND WEAR
semi-crystalline compound. “Due to the frozen amorphous coating, the tribological properties can be halved compared to a well-formed semi-crystal- line coating,” she says.
Ongoing innovation At Italian compounding company Lati, which includes a number of self-lubricating materials in its portfolio, Technical Assistance & Marketing Director Luca Posca says there has been no let-up in its development of new special compounds, “even during a very difficult period like 2020.” He says the company has expanded its product range with numerous innovative formulations. “In particu- lar, the LatiLub family of self-lubricating com- pounds has been enriched by the addition of new solutions designed to leave a lower environmental footprint compared with traditional ones.” Efforts have focused on the replacement of PTFE, which although it has exceptional tribological properties, is not suitable for halogen-free applica-
tions and presents end-of-life disposal problems, Posca says. The company has developed a full range of alternatives based on ultra-high molecular weight polyethylene, UHMWPE, also well-known for its low friction coefficient and good wear resistance (one high-profile use is skating surfaces). Its thermal characteristics allow it to be used in many semi- crystalline and amorphous thermoplastic matrices, including high-melting polymers such as PPS. “Added to its superior excellent friction, abra- sion and wear resistance compared to PTFE, the nature of the polymer is such that it is completely risk-free in terms of moulding equipment corro- sion, and also presents no risk to human health or the environment,” Posca says. The elimination of PTFE, silicone and carbon- based additives is also the founding principle of a second new Lati development. It aimed not only to cut halogen content but also to limit the risks associated with particulate formation and hazard- ous migration which may threaten the smooth running of electrical machines. According to Posca, the new formulae, identified by the extension LU2, are based on mixtures of metal sulphides, whose ceramic structure reduces friction and wear without compromising either the safety or the reliability of the devices in which they are used over time. Posca also highlights a range of self-lubricating compounds designed for 3D printing using the FDM (Fused Deposition Modelling or Fused Filament Fabrication) technology. Filaments developed within the company’s 3DLab R&D unit include PTFE and aramid fibre-filled products based on PLA, ABS, PA, PC and PETG. The com- pounds are designed for use in the manufacture of functional items.
Figure 1: Chart showing the effect of different lubricant combinations on the tensile and impact properties of a POM compound Source: Mocom
Figure 2: Schematic illustration showing the different modes of action of silicone and PTFE lubricants. Silicone (left images) functions through migration of silicone, which continually renews the lubricating surface layer. PTFE (right images) is embedded in the bulk material, with fresh particles exposed as the surface wear Source: Mocom
44 COMPOUNDING WORLD | February 2021
www.compoundingworld.com
Functional options UK-based Colloids offers a number of masterbatch products that are formulated to increase wear resistance characteristics in polymer compounds. The company uses numerous functional additives
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
