K 2019: 21st International Trade Fair for Plastics and Rubber - WACKER Presents Non Post-Cure Liquid Silicone Rubber for Sensitive Applications and its Portfolio of Low Volatile LSR Grades

Notwithstanding the fact that the ELASTOSIL^® LR 5040 range was announced back at K 2016, WACKER has good reasons for making the innovative liquid silicone rubber the focus of attention again at this year’s plastics trade fair: the company has now completed product development and capacity expansion for the silicone rubber to make all the grades in the series available to a broad customer base.

ELASTOSIL^® LR 5040 cures to translucent elastomers whose volatiles content – without thermal post-treatment – usually ranges from 0.2 to 0.3 weight percent. So, even in the non-post-cured state, they are already far below the limit value of 0.5 weight percent that applies to the volatiles content of silicone articles intended for food contact and baby-care applications. This compares with the figure of more than one percent usually attained by commercial standard products that have not been thermally post-treated.

For many liquid silicone rubbers, the thermal treatment which follows the curing process – known as post-curing – is performed not only to reduce volatiles but also to improve the mechanical properties of the final part. Users of ELASTOSIL^® LR 5040 can now skip this lengthy and costly step in most cases since the elastomers already possess high tear strength without post-curing. The elastomers’ tear strength is on a par with that of post-cured, high-tear-strength standard materials. As a result, parts molded from ELASTOSIL^® LR 5040 withstand the kinds of stress that feeding teats and pacifiers are subjected to in use.

Due to their high purity, ELASTOSIL^® LR 5040 elastomer parts are suitable for food-contact applications and can be used in line with the recommendations of the German Federal Institute for Risk Assessment (BfR) and the US Food and Drug Administration (FDA). They also meet the criteria of selected biocompatibility tests in ISO 10993 and US Pharmacopeia (Class VI). Moreover, the particularly low content of migratables and extractables from ELASTOSIL^® LR 5040 elastomer parts proves hugely advantageous for applications in medical technology.

With its properties, ELASTOSIL^® LR 5040 is the material of choice for fabricators of silicone articles who want to skip post-curing in the manufacture of products for sensitive applications. The portfolio comprises a hardness range from 30 to 70 Shore A, with a narrow width of specification of +/- three points.

ELASTOSIL^® LR 5040 can be readily processed by injection molding. As the resulting parts do not have to be post-cured, production processes can be greatly streamlined and extensively automated. This makes for very rapid, efficient and cost-effective large-scale production – even under cleanroom conditions. Typical applications are baby pacifiers and feeding teats, metering valves, gaskets for kitchen appliances, coffee percolators and food containers as well as rubber-elastic articles for the medical technology sector.

Low Volatile-LSR Portfolio: Setting Standards Around the World

WACKER’s Low volatile-LSR initiative is setting standards around the world. The Munich-based chemical group has been producing liquid silicone rubber grades with a low volatiles content since early 2019. This applies to the product groups ELASTOSIL^® LR 3xxx, ELASTOSIL^® LR 6xxx and SILPURAN^® 6xxx manufactured in Europe.

Thanks to ultra-modern process technologies, WACKER has managed to slash the content of volatile Dx siloxanes in its liquid silicone rubber by at least 90 percent. By upgrading the LSR portfolio in this way, the company is enabling manufacturers of silicone parts to meet regulatory requirements as well as industry and customer needs more readily and reliably than ever before.

In many applications, manufacturers will have the option to shorten the post-curing times and thus to reduce emissions and to free up scope for energy and cost savings. And, in some cases, they can actually dispense with post-curing altogether. In fact, even non-post-cured oil-bleeding LSR products in the ELASTOSIL^® LR 384x series meet the exacting “Toyota Standard” on the volatiles content.

The upgrade has no effect whatsoever on the elastomer’s mechanical, physical or chemical properties. Product releases and certificates thus retain their full validity. According to WACKER’s investigations, injection-molding and demolding behavior are not affected.

The Low volatile-LSR initiative was developed by WACKER in response to stricter purity requirements imposed on silicone articles not only by legislators, but also by countless industry branches and major companies. WACKER’s Low volatile-LSR portfolio therefore represents huge progress for the silicone sector as a whole.

More information available at www.wacker.com/k2019.

Visit WACKER at K 2019 in Hall 6, Booth A10.