Liquid silicone rubber (LSR) injection molding is an industrial process that has been around for years. Its use has significantly expanded recently, especially in the areas of medical devices and wearable technology, as well as automotive, infant care and household goods.
LSR cures faster and offers properties not obtainable with traditional rubber materials, especially heat resistance, extreme low-temperature flexibility, chemical resistance, biological inertness, and an intrinsic capacity for reducing friction. The material’s expanded use has resulted in the development of new LSR process equipment, especially technology that optimizes LSR injection molding machines to provide the greatest value and ease of use. An example is the development of new closed-loop control systems, including those found in the Graco Fluid Automation F4 series.
The basic raw material for silicone rubber is sand, or silicon dioxide. The material is processed into pure silicon metal. It is then reacted with methyl chloride, after which a range of processing steps is used to create a variety of silicon types, including liquid.
LSR is a two-component reactive chemical with a thick, almost paste-like consistency, which has been compared to peanut butter. The two components are usually shipped in separate containers. Some medical-grade silicones are shipped in small disposable plastic cartridges. The two components are mixed in a 1:1 ratio to produce a reaction. Accelerated by heat, the two liquids change to a solid rubber.
LSR injection molding is an inherently clean production process, because the component chemicals are sealed within a closed system. No ambient air contacts the parts until they are removed from the mold, eliminating issues with dust and moisture. This also improves part quality, because contaminants can diminish the cured rubber’s physical properties.