Elastomerics Blog

Liquid silicone injection molding (LIM) is a highly precise, automated process for manufacturing large volumes of complex parts. Its applications aren’t limited to medical gaskets, but LIM is well-suited for medical molding because liquid silicone rubber (LSR) combines the benefits of silicones with high purity and low shrinkage. Some LSRs are biocompatible and meet USP Class VI requirements.

Stockwell Elastomerics offers liquid injection molding services and uses platinum-cured LSRs that maintain their mechanical properties over a wide temperature range, resist degradation, and contain little to no byproducts. Among its many advantages, LIM supports the tight tolerances, complex geometries, and thin-wall features that some medical gaskets require.

How Liquid Silicone Injection Molding Works

Liquid silicone injection molding is a high-volume process because it uses a tool that is considerably more expensive than a compression mold. By spreading the cost of the tool across many LSR parts, however, this precision-machined mold becomes cost-effective. Often, molds are made of hardened tool steel, a type of metal that withstands high molding pressures and temperatures. For certain part geometries, LSR molds can be produced with a high cavity count. This further increases their cost and production efficiency.

The liquid silicone system that’s used has two parts, A and B, which are pumped from sealed containers into a static mixer. Pigments and other additives can be introduced at this stage, but LSRs are normally translucent. After the mixed silicone is injected, the mold is closed and sealed to minimize contamination and ensure consistent cavity fill.

Liquid silicone rubber cures rapidly at elevated temperatures, often within seconds to a few minutes depending on part size. This fast cure cycle supports high-volume production and repeatability. After LSR parts are removed from the mold, post-curing may be required for additional stabilization or volatile reduction, especially for medical applications.

Why LIM Is Ideal for Medical Gaskets

Medical gaskets need to seal reliably, withstand sterilization, resist chemicals, and maintain their performance across a wide temperature range.  Applications vary, but medical grade silicone rubber is often used with diagnostic instrument housings, fluid handling systems, optical and imaging equipment, patient contact devices (wearables), and portable medical electronics.

Liquid silicone injection molding supports custom geometries that improve sealing reliability, and LSR parts can withstand autoclave steam cycles, gamma radiation, ethylene oxide (EtO), and chemical disinfectants. Liquid silicone rubber is used extensively in single-use (disposable) medical devices, but its ability to withstand sterilization is an advantage over other polymers.

With their low levels of volatiles and extractables, platinum-cured LSRs are suitable for use with optics, sensors, and fluid pathways. These clean, stable materials won’t contaminate surfaces, fog lenses, or interfere with analytical results. Liquid silicone injection molding also supports medical device miniaturization through the production of micro-gaskets with thin walls and fine details.

Applications for LIM micro-gaskets include wearable medical sensors, point-of-care diagnostic cartridges, microfluidic devices, and portable imaging systems. LSRs can also be overmolded onto metals, plastics, and other substrates to create seamless, bonded gasket assemblies, integrated seals on housings, and multi-material components that reduce part counts and simplify assembly.

Ask Stockwell Elastomerics for Medical Gaskets

Understanding the basics of LIM for medical gaskets is important, but design engineers must also select a specific LSR. Stockwell Elastomerics can help you with material selection and review your gasket design. To talk to our Applications Engineering Team, complete our on-line form, email service@stockwell.com, or call (215) 335-3005.