Full definition
Liquid Silicone Rubber (LSR) is a two-component (A+B) platinum-catalyzed addition-cure silicone elastomer system specifically engineered for high-speed injection molding applications. This technology allows for the production of precision rubber parts with exceptionally tight tolerances, excellent repeatability, and minimal flash. The mixing of the components occurs in a static mixer at the injection unit, following a 1:1 ratio, which ensures consistent quality and performance in the final product. The curing process takes place rapidly within a heated mold at temperatures ranging from 150-200°C, with typical cycle times varying from 10 to 60 seconds. This efficiency is a significant advantage over traditional solid silicone rubber (HCR), where longer curing times and post-curing processes are often required.
LSR offers several key benefits, including faster cure cycles, enhanced dimensional precision, and compatibility with automation processes, such as liquid pumping and closed molds. Importantly, LSR does not require post-curing, which can streamline production and reduce costs. Furthermore, LSR is inherently biocompatible, meaning it does not leave behind peroxide residues that could affect the safety of medical devices and other applications. The hardness of LSR can range from 10 to 80 Shore A, with tensile strengths between 5 to 12 MPa and elongation percentages from 200 to 1000%. It can withstand a temperature range of -55 to +200°C, making it suitable for a variety of demanding applications.
Applications for LSR are extensive and include medical devices such as seals, valves, syringe gaskets, and respiratory masks. Additionally, it is used in infant products like pacifiers and bottle nipples, automotive components including connectors and spark plug boots, consumer electronics for keypads and wearable device seals, and even LED optics. Compliance with FDA and USP Class VI standards further validates its suitability for sensitive applications. According to ISO 4633, LSR specifications are well-defined, ensuring that manufacturers maintain high quality and safety standards. Notable manufacturers of LSR products include Wacker (Elastosil LR), Dow (Silastic LSR), Shin-Etsu, and Momentive, and the production requires specialized LSR injection molding machines from companies like Engel, Arburg, and Sumitomo.