It was in the 1950s when Liquid Silicone Rubbers (LSR) was first used as an optical material. Lighting applications were the first widespread use of optical silicone rubber of its transparency, and medical applications soon followed. Because of the chemical structure of LSRs (Silicon and Oxygen atoms), which is naturally opaque, with a translucent milky color, its clarity must be improved for optical grades. Fortunately, Liquid Silicone Rubber can be altered by incorporating components in its structure . The chemical structure can be modified the during synthesis in various ways, by: 1) including groups to create a short-range arrangement; or 2) employing external materials called additives to create a new phase that increases the transparency. Depending on the application, there are various optical properties that can be improved, such as haze, gloss, clarity or refractive index . When the optical properties are modified, the mechanical and chemical properties may also be affected, therefore it is important to find an acceptable balance between optical specifications and its function in its end-use application.
Injection molding is the most common manufacturing process for the production of Liquid Silicone Rubber parts. The biggest advantage injection molding offers is its quick fabrication of parts, regardless of the size, complexity or application . When using Liquid Silicone Rubber (LSR), the two components of the LSR material are transferred to the injection machine using a pneumatic pump. In the machine’s mixing head, the two components of the material are combined, and this is the location where a color can also be introduced if applicable. There are several static mixer sections in the mixing head to ensure the material components are well combined with the appropriate mix of the LSR material and additives.
Choosing the best materials for new medical devices and disposables along with an experienced technology partner such as SIMTEC Silicone Parts, is critical for the success of your program. From biocompatibility to cost, multiple factors play into the final decision. Innovative companies are selecting more and more Liquid Silicone Rubber (LSR) components for their medical devices.
The silicone family is made up of an enormous variety of compounds, and is perhaps the most widely used family of materials in the world. Liquid Silicone Rubber materials can be found in consumer products in applications such as appliances and electronics, in astronomy, biotechnology, and in the automotive, aviation, beverage, construction, paint, plumbing, textile, and toy industries.
Injection molding is the most common technique for the mass production of simple or complex Liquid Silicone Rubber (LSR) products with high dimensional tolerances. Knowing the behavior of the LSR before processing begins, will increase the productivity and quality of the final product and help to reduce costs. The characterization of the material employed and the simulation when processing the material will provide important information regarding characteristic behavior of the Liquid Silicone Rubber.