Silicone parts intended for use in the baby-care sector and the food industry in Europe must contain no more than 0.5 percent volatile substances. To ensure compliance with this limit, thermal post-treatment is often necessary. That entails heating the cured parts to temperatures of 200 degrees Celsius for several hours in a ventilated oven. This process step, which specialists also refer to as “post-curing”, accomplishes two things: it eliminates volatiles from the elastomer and improves its mechanical properties.
This laborious and expensive procedure will soon be obsolete. “We designed ELASTOSIL® LR 5040 in such a way that this silicone rubber already complies with current regulatory requirements governing applications in the baby-care sector and food industry in its non-post cured state”, says Christian Gimber, head of the Engineering Silicones business unit at WACKER. “Thus, in many cases, our customers can eliminate post-curing of silicone parts for sensitive applications.”
Rubber parts made of ELASTOSIL® LR 5040 are translucent with a delicate blue shimmer. Their volatiles content – without thermal post-treatment – is below the required 0.5 weight percent. Even in its non-post cured state, the silicone rubber already exhibits a high level of tear resistance equivalent to that of a post-cured high-tear-strength standard LSR. As a result, it can withstand even high mechanical stresses as may occur during the usage of baby bottle nipples or pacifiers, for example.
These properties make ELASTOSIL® LR 5040 the material of choice when manufacturers of baby-care, food-contact or medical products want to do without thermal post-treatment. Typical applications include feeding teats and pacifiers, teething rings, anti-colic valves, bottle tops and seals for food cans, but also respirator masks.
ELASTOSIL® LR 5040 can be readily processed by injection molding. Since molded parts made of this LSR only have to be post-cured in very few cases, production processes can be greatly streamlined and automated to a high degree. This facilitates very efficient and cost-effective large-scale production.
The product line will initially cover a hardness range from 30 to 70 Shore A including 45 Shore A, a universally used grade in the baby-care sector. In the cured state, the actual hardness of the non-post cured silicone rubber deviates by no more than ±3 points. The LSR is translucent and has a delicate blue shimmer, giving the silicone parts a particularly pure, high-quality appearance.
WACKER Optimizes LSR Product Portfolio
ELASTOSIL® LR 5040 made its debut at the K 2016 International Trade Fair for Plastics and Rubber in Düsseldorf, Germany, last October. At this year’s Fakuma, the product line again takes center stage, sharing the spotlight with the heat-resistant solid silicone rubber ELASTOSIL® R plus 4350/55.
“The raw-materials sector has to meet ever tougher legal as well as industrial requirements. For instance, regulatory limits are tightening increasingly, especially as regards the amount of volatiles. This is a challenge for the entire chemical sector and also affects liquid silicone rubber grades”, manager Christian Gimber notes. “In this respect, the trend is mainly being driven by the baby-care, food and automotive industry.”
Reducing the volatile components will also have a positive impact on the properties of articles made of WACKER’s LSR grades in general. “We decided to optimize our LSR portfolio and reduce the amount of volatile substances significantly”, Gimber adds. “Thanks to cutting-edge production technologies now in use, we are able to go well beyond legal requirements. We are thus meeting tougher requirements, which immediately benefit our customers in a variety of ways.”
Visit WACKER at Fakuma 2017, Hall A6, Booth A6-6310.
Note to editors:
During the tradeshow, the fabrication of bottle nipples made from ELASTOSIL® LR 5040/45 will be demonstrated at the booth of metering and mixing technology expert DOPAG (Hall B5, Booth 5315).