Wacker is offering two new liquid silicone rubber grades: Elastosil LR 3011/50 FR and Elastosil LR 3170/40.
The US testing institute Underwriters Laboratories (UL) has given these highly flame resistant products its very best flammability rating (V-0). The new silicone grades also reduce processing costs. Compared to other highly flame-retardant liquid silicone rubber, the new Elastosil LR 3011/50 exhibits considerably less abrasive behavior during the injection moulding process, thereby reducing abrasion in the mould. The same applies to Elastosil LR 3170/40. This self-adhesive liquid silicone rubber is also ideal for producing flame-retardant, two-component moulded parts on a large scale, and with considerable speed and a high degree of automation. Up to now, the way to render liquid silicone rubber grades flame resistant was to add inert fillers such as quartz. These types of fillers, however, result in increased material abrasion during the injection moulding process. Such abrasion, which is especially evident in the sprue portion of the injection mould, shortens maintenance intervals and leads to costly mould reworking. The new Elastosil LR 3011/50 FR liquid silicone rubber eliminates this problem. It is formulated with special inert fillers that work together to produce outstanding flame-retardant properties without the use of abrasive additives. The result is a clear reduction in mould fouling over traditional flame-resistant liquid silicone rubber grades, and this, in turn, significantly extends equipment life and offers considerable process-cost advantages. The vulcanisates of Elastosil LR 3011/50 FR in various thicknesses have been rated V-0, as per Underwriter Laboratories standard UL 94. Elastosil LR 3170/40 Self-Adhesive Liquid Silicone Rubber Elastosil LR 3170/40 is a new liquid silicone rubber grade that addresses the increasing importance of two-component injection moulded products. The silicone in this case is the soft component of a hard/soft composite. Elastosil LR 3170/40 is self-adhesive and, after curing, also meets the V-0 flammability rating defined in the UL 94 standard. Elastosil LR 3170/40 uses a patented Wacker self-bond- ing technology that has already found application in other silicone grades. This liquid silicone rubber is formulated in such a way that it begins bonding to hard components – but not to the surface of the injection mould – during the vulcanisation process. Surface priming or pretreatment (with plasma, for instance) is no longer necessary. In the production of two-component injection moulded products, this bonding behavior allows manufacturers to increase automation to a level previously unattainable with flame- resistant liquid silicone rubber. Suitable hard components include metals such as aluminum and certain flame-resistant polyamides.
Properties and Areas of Application Elastosil LR 3011/50 FR and Elastosil LR 3170/40 can both be easily integrated into the injection-moulding process. The vulcanisates of both silicone grades yield a balanced material profile and are characterised by favorable mechanical and dielectric properties, as well as excellent heat resistance. Possible applications for both of these new products can be found wherever processes require not only high levels of fire protection, but also properties typically associated with silicone, such as elasticity at low temperatures, electrical non-conductivity and resistance to heat, weathering and aging. Applications in- clude LED fittings for background lighting in flat screen monitors, axial and radial seals in connection sockets, and single-wire seals for the housing of solar collectors. The rapid development of electrically powered vehicles has in- creased flame-resistance requirements for the components used in this field. A high level of safety must also be guaranteed in the event of overheating or a short circuit. Elastosil LR 3170/40 and Elastosil LR 3011/50 FR satisfy these increasing de- mands, with each serving as fire protection materials whenever a product needs to be both highly resistant to electrical discharge and sealed from external media.
