MATERIALS | LIQUID SILICONE RUBBER


Right: Wacker says tests show that its new self-adhesive silicone rubber Elastosil LR 3078 adheres excellently to polycarbonate without pretreatment


advantage of ready-to-use solutions will find Powersil Resin 710 silicone moulding material suitable, as it contains an optimised blend of powdered and fibrous fillers and is based on the two aforementioned binders. Manufacturers can create insulation class R moulded parts via compression moulding, pres- sure gelation or injection moulding with use of the binders and the silicone moulding material. The components made from this material combination are extremely heat-resistant and can withstand tem- peratures of up to 220° C for extended periods of time. The products are not subject to labelling requirements and thus present an advantageous alternative to high-temperature-resistant polymers like polytetrafluoroethylene (PTFE) or polyether ether ketone (PEEK). Wacker developed a new silicone-based additive masterbatch that makes it easier to manufacture ready-to-use PE moulding com- pounds and improves the surface properties of the resulting plastic products. Its new Genioplast PE50S08 additive masterbatch uses silicone as an active ingredient to improve filler distribution in filled formulations and the flow properties of the polymer melt, which increases throughput and reduces the energy needed for compounding. Where mixtures of different polyethylene grades


are compounded, as is the case in the processing of recycled polyethylene, the additive masterbatch ensures uniform mixing without any major torque or temperature fluctuations. Momentive Performance Materials said its


latest developments focus on requirements that advance mobility concepts. At the K show it introduced new LSR materials that offer tempera-


ture resistance with increased flame retardancy. The new NL6830FR and NL6850FR grades are designed for applications such as seals in the intake area of combustion engines, collective seals, and O-rings, or for use in sensor technology and in the drive area of electric vehicles where flame retardance is required. The two materials, both in dark gray, meet the UL94-V0 requirements at 1 mm thickness. Characteristics include a Shore A hardness of 35 and 45 respectively, very good mechanicals with a low compression set. Momentive also presented the third generation


of its low temperature cure liquid silicone rubber (LTC-LSR) material. The updated formulation cures at even lower temperatures than the development grade presented at the Fakuma fair in Germany in 2021. The lower temperature cure allows the mould temperature to be reduced while maintain- ing the same short heating time, saving energy. This characteristic invites combinations with compound formulations containing temperature sensitive components. The lower temperature also makes it possible to trim crosslinking time in half compared with a standard LSR, and subsequent annealing is not necessary.


Above: At K2022, Momentive demonstrated its new LTC-LSR, which crosslinks at a lower temperature, in a thick-walled tea light holder application, while its Hardcoats division showed the fully automated coating of a three-dimensional component using free-form digital printing


40 INJECTION WORLD | July/August 2023


Momentive also developed a self-lubricating LSR for hard-soft composites. Silopren LSR 2725/40 enables cost-efficient production of rigid-soft composites in which engineering plastics including PBT are over moulded. This includes, for example, moulded parts with integrated sealing or damping. The Silopren formulation forms good initial adhesion to the substrate very quickly, making short cycle times possible. Full adhesion is achieved during subsequent storage at room temperature. At the same time, a migration process takes place that gives the LSR surface its self-lubri- cating property that facilitates assembly processes, the company said. Silopren LSR 2725/40 is resistant to high temperatures and is flexible at low tem- peratures. It combines good dielectric and me-


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IMAGE: MOMENTIVE


IMAGE: WACKER


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