As the medical device industry has deepened its understanding of the medical materials used in products, the unique and special properties of liquid silicone rubber have expanded its application range. As these properties become more widely known, new applications and expanding markets are also driving the wider use of liquid silicone rubber in medical devices.

Silicon, the basic ingredient in silicon, is the most common and readily available element on Earth. Liquid silicone rubber's ease of fabrication into complex shapes and chemical inertness make its practicality and excellent properties ideal for use in medical devices from the outset.

Unique properties of liquid silicone rubber

For medical use, silicones must be tested for biocompatibility and comply with FDA regulations. Medical silicone is divided into two categories in terms of application: time-limited and time-free. Usually limited for short-term transplantation, unrestricted for long-term transplantation. The liquid silicone rubber described herein is medical grade.

The biocompatibility and hyposensitivity of liquid silicone rubber minimizes the risk of allergic reactions during use. And because of its hygienic nature, bacteria and fungi are almost impossible to grow and spread. These properties make it an ideal material for short- and long-term implantation devices.

Liquid silicone rubber is elastic, durable, transparent, UV-light-resistant and tensile-resistant. Unlike traditional rubber, liquid silicone rubber can withstand extreme temperatures and will not denature from -55°C to 200°C. Due to this property, instruments made of liquid silicone rubber can be autoclaved.

Liquid silicone rubber also has extraordinary permanent compression set properties and can be made with different wall thicknesses in the same part. Combined with the material's durability and malleability, these characteristics make it a critical component of medical devices.

Due to the chemical inertness and temperature resistance properties of liquid silicone rubber, it has a long shelf life and service life. Silicone suppliers recommend that raw materials should be processed within six months, but in practice cast parts containing liquid silicone rubber can be stored indefinitely, although molders recommend a maximum of three years. The durability of this medical material extends the life of the corresponding medical device, benefiting both manufacturers and end users.

Likewise, the medical device industry has shown a preference for liquid silicone rubber medical materials. Unlike rubber, which sensitizes some users, liquid silicone rubber is hypoallergenic. Liquid silicone rubber does not contain phthalates in polyvinyl chloride, plasticizers found in experiments to disrupt the endocrine system and damage the reproductive and nervous systems.

However, cost is a drawback of liquid silicone rubber. Compared with other raw materials, such as thermoplastic elastomer (TPE) and thermoplastic polyurethane (TPU), the cost of silicone resin is 3-5 times that of them; the production cycle is longer and twice as much.

In some cost-sensitive applications, if some properties of liquid silicone rubber such as temperature resistance, compression deformation and chemical inertness are not required, cheaper thermoplastic elastomer TPE and thermoplastic polyurethane TPU can be used.


Application of liquid silicone rubber

Liquid silicone rubber is used in numerous medical devices, including seals, pistons, gaskets, and components of medical electronics for implantable or non-implantable devices. Specific uses of liquid silicone rubber by producers include:

• Cushioning pads for lung catheters. Soft liquid silicone rubber is wrapped around the front end of the catheter to prevent the catheter from tearing the soft lung tissue.

• Double J tube blocking parts.

• The outermost coating of the silicone shock absorber.

• Polycarbonate ablation tube with silicone plug.

• Silicone tube coupler.

• Silicone sealing caps for medical devices.

The wider application of liquid silicone rubber is limited only by the designer's experience, education and creativity, as well as the producer's experience and exploration of innovative applications of this medical material.

Process properties of liquid silicone rubber

In manufacturing, liquid silicone rubber has a bonded and non-bonded mold effect. Parts made from liquid silicone rubber can incorporate metals, plastics, glass, ceramics and plexiglass or just the silicone itself.

The manufacturing advantage of this attribute is the elimination of individual components in a device, such as using insert molds, o-rings and gaskets made of liquid silicone rubber can be cast directly on metal or plastic parts that need protection, reducing inventory and assembly cost.

Manufacturers also need the ability of liquid silicone rubber to be cast directly on a hard plastic sheet to create a monolithic part, rather than glue-like sticking together separate parts made of two different materials. By producing a separate part in this way, the labor steps of assembling the separate parts are reduced, reducing the risk of leaks due to seal failure. This also provides the opportunity for manufacturers to design more attractive and functional products. Liquid silicone rubber can be designed in various colors and processed to different hardnesses.

Considering the variety of liquid silicone rubber as a production material, mold tools can be quickly applied to various projects to control the cost. Standardized off-the-shelf cooling stages and tool assemblies are available from many suppliers.