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“Materials” are the foundation of our technology. Every day, people deal with products that possess seals and they generally know very little about the materials with which they are made. For example, plastic is a comparatively new material and has long been considered to be a “wonder substance”. But why is plastic so flexible and how are the various mixtures differentiated from one another? When is a silicone seal better than one made of polyurethane or rubber?
VMQ, PVMQ, FVMQ – Silicone Rubber
Silicone rubbers belong to the category of synthetic polymers in which silicon atoms are linked together with oxygen atoms. They are stable in hot air and ozone, in water, in animal and plant oils, and fats. But they do not stand up to low molecular weight esters¹ and ethers, acids and alkalis, along with aliphatic (such as gasoline, propane and methane) and aromatic hydrocarbons (such as benzene, xylene and tolulene).
Silicone rubber displays high thermal resistance and good cold flexibility from −60 °C to 200 °C, but has little tensile strength, elongation or abrasion resistance. FVMQ withstands even low temperature applications up to -80°C. VMQ silicone elastomers are used in demanding thermal applications, and, due to their purity, are especially suited for hygienic uses in the food and pharmaceutical industries like the VMQ 117055. Due to its very good physiological characteristics, silicone is a proven sealing material, especially for butterflybutterfly valve seals. Their low breakaway torque ensures reliable switching over their entire lifecycle.