INNOVATION | LIQUID SILICONE RUBBER


Right: Wacker develops LSR materials for use in automo- tive and healthcare applications


Electrification is also fundamental in the digitali-


sation megatrend, in which cars are expected to have the functionality of a smartphone. Wachtler said this creates opportunities for low friction LSR materials in sealing applications, cable wiring and two-component moulding.


Self-adhesive LSR is widely used in safety-rele- vant applications, and these are expected to multiply due to the trend towards semi-autono- mous driving. He said: “The whole car is surround- ed by sensors, and all these sensors have to be sealed. If they are outside the car, they need a certain degree of UV resistance and LSR is the perfect material.” The material requirements in high voltage


applications such as cable and plug connectors include long-term high temperature stability, electrical insulation and tight connections. Wachtler referred to one of Wacker’s LSR solutions in these applications, the self-adhesive Elastosil LR 3675 with a low coefficient of friction, which the com- pany is promoting as an alternative to oil-exuding materials. This LSR also has a low compression set of 12% after 22 h/125°C. Wachtler also discussed other key markets for


LSR: healthcare and food-contact applications. He said Wacker is pursuing a twin track approach for LSR to meet increasing requirements regarding volatile organic compounds and productivity. It has upgraded its LSR portfolio to have a reduced volatile content, achieving this by significantly reducing the amount of Dx Siloxanes by improved devolatilisation of raw materials. Productivity is targeted with new low-volatile LSR


materials that eliminate the post-curing stage normally needed for sensitive applications. Elastosil LR 5040 series materials have the lowest content of volatiles, migratables and extractables in the Wacker LSR product range. They are formulated for


high tear resistance so that, even without post- curing, they comply with current regulatory require- ments that say baby items and food contact materials should contain no more than 0.5% volatile substances. Healthcare materials were the main focus of the


presentation from Marco Jesus, European Market- ing Manager for Healthcare at Momentive Peformance Materials. Self-lubricating LSRs have advantages that include: low coefficient of friction that enables automated assembly of medical devices; biocompatibility compliance with USP Class VI and ISO 10993 requirements; and en- hancement for moulded parts to glide into mount- ings. The latter benefits applications such as needle-free access valves, and other applications including O-rings, stoppers and seals. Self-bonding LSRs are also useful in healthcare


applications where two-component moulding is beneficial for combining LSR with a thermoplastic. Momentive has introduced its Silopren 47x9 LSR range for healthcare. Jesus said these were developed for combining with polycarbonate, which is a commonly used plastic in medical devices (the Silopren 47x9 grades also have good adhesion to co-polyesters, PBT and glass). The grades are compliant with USP Class VI and ISO 10993, including in a non-post-cure state. Their productivity benefits include: low temperature curing; no post-curing requirement; and no adhesion to the injection mould. Jesus rounded off his presentation by handing


At K2019, Momentive showed a two-shot LSR and polycarbonate phone holder


18 INJECTION WORLD | April 2020


round the audience a non-medical application featuring Silopren 4749 LSR which was shown at K2019. The demonstration part, a phone holder for a car dashboard, was 2K injection moulded with Covestro APEC 1745 polycarbonate. The butterfly- shaped phone holder was produced on the Momentive stand on a SmartPower Combimould 120/130/210S with a Unilog B8 control unit from


www.injectionworld.com


IMAGE: WACKER


IMAGE: MOMENTIVE


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