Silicones, more precisely poly(organo)siloxanes, are elastomeric synthetic materials based on oxygen-linked silicon (Si). This in the world of polymers unique chemical structure of the molecule chain provides equally unique properties of the raw material and the manufactured products. In addition to the possibility of silicone modification for nearly any purpose, the uncomplicated handling also allows us to generate complex geometries and large quantities. As the parent substance for silicone elastomers is derived from quartz sand, we have a sheer unlimited access to resources. The term silicone describes a group of polymers, which are classified after DIN ISO 1629 more precisely as follows: Q = Polysiloxanes MQ = Dimethylsiloxane - polymer with a silicon-oxygen chain and two methyl groups attached to the siloxane backbone (commonly known as PDMS – polydimethylsiloxane) VMQ = Copolymer from vinylmethylsiloxane und dimethylsiloxane – a part of the methyl groups is replaced with vinyl groups. PMQ = Copolymer from phenylmethylsiloxane und dimethylsiloxane – a part of the methyl groups is replaced with phenyl groups. PVMQ = Terpolymer from phenylmethyl-, vinylmethyl- und dimethylsiloxane – VMQ in which a part of the methyl groups is replaced by phenyl groups. FVMQ = Terpolymer from trifluorpropylmethyl-, vinylmethyl- und dimethylsiloxane – VMQ in which a part of the methyl groups is replaced with flour substituents. The chemical modifications of MQ rubber allow specific adjustments, e.g. tuning of the material characteristics.
Liquid silicone rubber is the most frequently processed derivative from the silicone elastomer family. This type of liquid rubber is due to its given viscosity pumpable and can therefore be formed into complex and filigree shapes in a fully-automated injection moulding process. The raw materials are a two-component system (mixing ratio A:B = 1:1) and can thus be replicated with a consistent degree of quality. By adding so called masterbatches, the transparent material can be tinted any colour during the moulding. The principle of cross-linking in LSR (addition curing) reduces the cycle times tremendously compared to traditional silicone rubber types without the formation of low-molecular-weight cleavage products. Moreover, LSR is suitable for a two-component injection moulding procedure and moulding tools with more than 200 cavities can be used. This type of silicone rubber is a VMQ and part of the group of high temperature vulcanisation silicones (HTV).
Solid silicone rubber, also called high temperature vulcanisation (HTV) silicone rubber, is a material in the form of a solid rubber block and has a significantly higher molecular weight than LSR. This type of silicone rubber can be linked additive or preoxidatively, according to the chemical modifications and it can be processed with various techniques, such as injection moulding, extrusion or hot pressing. HTVs offer a cost-effective way to produce silicone elastomers, but often lag behind LSR in terms of mechanical properties and cycle times.
One of the most advantageous characteristics of silicone materials is their ability to be modified for almost any purpose. Next to the already popular colourability, the mechanical properties, hardness, chemical and temperature resistance, electrical properties (conductive or insulating), magnetic properties (magnetisable or non-magnetisable), flammability, friction coefficient of the surface, transparency, linking conditions and much more can be purposefully influenced. The adjustments of the mentioned material properties can be achieved by additives or chemical modifications of the rubber.
The two components of the LSR raw material are pumped via a dosing unit with the ratio 1:1 from the supply barrels into a mixing unit. Here, an additional component (colour/masterbatch or additive) can be added with another pump and blended. The mixed material is transferred to a dosing cylinder (at room temperature) and injected into a cavity that defines the shape of the manufactured device. The injection moulding tool comprising the cavity was heated to the specific vulcanisation temperature of the applied silicone mixture. After the thermal energy hardened the content of the closed tool, the resulting silicone rubber can be extracted.
Do you need further information on silicone materials? br> We provide consultations in our offices or via telephone to inform you about the various properties and applications of this unique material, so that we can find together the suitable material for you.