Liquid Silicone Rubber
Liquid silicone rubber is the liquid form of a synthetic, two-component, elastomeric polymer that is made from silicone elastomers. Supplied in two parts, liquid
silicone rubber must be heat-cured and requires the addition of a catalyst, which is typically platinum. Liquid silicone rubber differs from other polymers in two major ways: first, it does not have a carbon backbone, but a Si-O-Si backbone; and second, although it is a polymer, it acts like rubber. Liquid silicone rubber can come in many different grades and forms that are defined by characteristics such as steam resistant, electrically conductive, flame-retardant, metal detectable and chemically-resistant. Liquid silicone rubber naturally offers properties such as high electrical insulation, extreme temperature resistance, a low compression set and the ability to withstand harsh environments. Liquid silicone rubber moldings have a long list of applications such as medical devices, sealing membranes, lab instruments, automotive heating hoses, shaft sealing rings, door seals,
o-rings, spark plug caps and compression
gaskets. As a result, a wide variety of industries find liquid silicone rubber beneficial including aerospace, medical, automotive, construction, electronics, appliance, architecture, petrochemical and pharmaceutical.
While liquid silicone rubber is the form in which most silicone rubber molding processes occur, it is primarily molded in liquid injection molding (LIM) processes as well as cast molding processes. In fact, the liquid injection molding process was specifically engineered in order to injection mold silicone rubber. The liquid silicon injection molding process involves proportioning, mixing and dispensing the two components of liquid silicone rubber. Due to its low viscosity, liquid silicone rubber can be pumped through pipes and tubing to the vulcanization equipment. One of the components contains the platinum-based catalyst. The two components are mixed in the static mixer and then transferred to the cooled metering section of the liquid injection molding equipment. The static mixer mixes the components into one very homogeneous material. From the cooled metering section of the liquid injection molding equipment, the liquid silicone rubber compound is pushed through cooled sprue and runner systems into the heated cavity in which the vulcanization occurs. The cast molding process involves pouring liquid silicon rubber into an open mold. The open mold contains a hollow cavity of the desired shape. The liquid silicone rubber is then allowed to solidify in the mold.