Appliance Design - May 2008 - (Page 26)

ELASTOMERS LED covers developed by Dow Corning represent one of the growing applications for silicone elastomers. Gaskets produced by Phillips Plastics using Wacker Chemical Corp. silicone elastomer materials. Photo: Phillips Plastics enough that it would leave blemishes that could be visible,” he says. “With silicone, we can make the gate so extremely tiny that it usually cannot be seen with a naked eye.” The liquid silicone rubber is supplied in either a 5-gallon pail kit or 55-gallon drum kit. (The kit refers to having two matched containers, an A component and a B component). “The consistency of material varies based on its durometer from a fairly running toothpaste to pretty stiff (texture).” The difference between liquid silicone rubber and traditional thermoplastics is that liquid silicone rubber requires specialized pumping system to supply to injection barrel. It can be messy if LATCHING RELAYS TO FIT YOUR TOUGHEST APPLICATION American Zettler has the highest quality relays for all your application needs. ·10 Amp Switching · Dielectric strength 4000 Vrms ·Single and dual coil latching versions available ·Epoxy sealed version available AZ880 For product Information log on to www.azettler.com ·2.0 Amp Microminiature Polarized Relay ·2.5 kV lightning surge withstand ·SMT and DIP mounting available · High performance AZ8462 AMERICAN ZETTLER, INC. 75 Columbia, Aliso Viejo California 92656 Phone: 949-831-5000 · Fax: 949-831-8642 www.azettler.com May 2008 not properly handled, Wolgemuth says. “It will stick to everything and because of its great chemical resistance, there are not a lot of things that will clean it or break it down.” he says. “On the whole, it does not significantly complicate the operation; it is just an additional set of variables that have to be taken into account.” Fabrication techniques such as Phillips’ multi-shot capability have expanded silicone elastomers use, but that is not the only reason for its growth. Wolgemuth points to a more standardized product that is on the market today. “The suppliers have really cleaned up the materials over the last 10 years,” he says. The new materials in use at Phillips and other molders cure faster, too. Wolgemuth says that the material undergoes crosslinking during the curing process, creating the elastomer matrix that gives the material its properties. There are four main components of the provided base material, the SiO polymer, a cross linker, temperature sensitive inhibitor, and a catalyst (usually platinum for newer materials). The system is activated the moment the two parts, A and B, are mixed. However, for some fast cures, heat must be applied. “Thermoplastic is just a matter of going back and forth between liquid and crystalline or solid state, whereas the liquid silicon rubber is actually changing or finishing its chemical structure,” Wolgemuth says. “Once the matrix has been formed for liquid silicon rubber, it can not be remelted or reprocessed.” Silicone elastomers such as Elastosil® from Wacker Chemical Corp., Adrian, Mich., is one example of a liquid silicone rubber that has been designed to cure faster than ever before. Ed Laperriere, sales manager for Wacker Chemical Corp., points to a very tiny part such as a singlewire seal that might weigh less than a gram. Every year, billions of them are made. At that volume, and their profit margin, speed of cure is very important. “These products in an 128-cavity mold would cycle in 15 seconds or less, clamp to clamp, he says. Some grades of Elastosil are self-lubricating, or oil-bleeding, types of liquid silicone rubber. The bleeding can aid in assembly operations. In addition, the lubricity of Elastosil and other elastomers also helps with mold release, which can reduce blemishes and speed mold times by filling the gap that might exist between the wire and silicone. The materials can be used in very utilitarian ways as well as in aesthetic and tactile ways. Today’s new materials have a large range of hardness levels. In terms of www.applianceDESIGN.com For more Information Enter 104 26 applianceDESIGN AD05084Amer.indd 1 3/28/08 10:56:04 AM http://www.azettler.com http://www.azettler.com http://www.appliancedesign.com

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Appliance Design - May 2008 Contents Editorial Shipments/Forecasts News Watch New and Notable Displays & Indicators Elastomers Quality & Standards Indoor Air Quality IHHS Highlights New Products Classifieds Design Marts Advertiser’s Index Association Report: PSMA

Appliance Design - May 2008

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