How Liquid Silicone Is Made
Unlike thermoplastic elastomers (TPRs and TPEs) which lose their elasticity at extremely cold temperatures, liquid silicone rubbers remain flexible down to -40°C. This feature makes LSR a popular choice for medical applications and automotive parts such as seals and gaskets. The material is also very resistant to exposure to sunlight, wind, rain and UV rays.
Like other elastomeric materials, the physical properties of LSR are determined by its chemical structure. However, unlike TPEs and TPRs, LSR has a higher chemical stability due to the strong bonds of siloxane chains. This results in a stronger overall product, as well as high resistance to tearing, abrasion and heat. Additionally, LSR is an effective electrical insulator, making it ideal for protecting wires and data cables.
When combined with its components, the uncured gel-like polymer of liquid silicone can be quickly injection molded. This characteristic brings significant commercial value to the material since it allows for fast-paced manufacturing, ensures repeatability and can be easily adapted to automated processes.
Typically, the two primary liquid materials – the catalyst and the base forming silicone – are pumped through metering units and a static or dynamic mixer, where they are simultaneously released at a specific ratio and fed into an injection mold. The injection mold is then heated to initiate a cross-linking progression, which creates the solidified silicone.
Once the silicone has cured, it can be removed from the injection mold and any remaining liquid is then used as a sealant or coating. Injection molding is a very versatile process and can be used to produce parts that are difficult or impossible to make using other production methods.
Because of its low compression set and rapid cure cycles, liquid silicone is also a very attractive candidate for overmolding with different plastics. This is a common technique to improve the aesthetic and functionality of products, such as a soft rubber button overmolded onto a plastic housing for a phone charger.
Liquid silicone is also an ideal candidate for rapid prototyping. Its shear thinning property means that it can be deformed while maintaining its structural integrity, and this is useful when creating functional prototypes and testing their performance. The material can be molded into complex shapes and intricate details that would be otherwise impossible to recreate.
While working with liquid silicone, it is important to follow all safety precautions. The process of mixing can create vapors that are toxic and corrosive, so it is imperative to use a gas monitor to identify if hazardous chemicals are present and keep all personnel away from the area while the mixture is being prepared. Additionally, it is important to avoid contact with skin or eyes and keep the area clean until all slurry gases have evaporated. To learn more about how liquid silicone can support your design process, contact an H.M. Royal product expert today. We can help you select the ideal grade for your application and provide all the necessary equipment to manufacture your final product.