What Is Liquid Silicone Rubber (LSR)? | Properties & Applications

Over the last hundred years, material innovations in basic and specialty elastomers have led to a range of materials that are suitable for a broad range of applications and operating environments. medical grade LSR

The materials vary in terms of key characteristics, such as elasticity, strength, hardness, compatibility, temperature range, environmental resistance and other properties.

One of these materials, LSR, which has been around since the 1970s, continues to make the transition to becoming the premier material for the manufacture of medical products and devices. LSR consists of a highly flexible thermosetting plastic that comes in a broad range of composition and hardness.

The variety of LSR materials allows product designers and engineers to select the material with the characteristics most appropriate for the application.

At room temperature, thermoplastic begins as solid material, which softens when you heat or reheat the material above its melting point.

In comparison, thermosetting materials start out in liquid form, and the heat cures the resin into a solid state. Once it cures, the part remains solid — a feature that helps make LSR the idea material choice for numerous medical applications.

Key Takeaways (TL;DR)

• LSR (liquid silicone rubber) is a two-part platinum-cure silicone processed by automated injection — ideal for high-volume, flash-free, tight-tolerance parts.
• Service range is roughly −60 to +230°C with excellent flexibility and electrical insulation.
• Medical and food grades meet ISO 10993, USP Class VI, FDA 21 CFR 177.2600, and LFGB.
• LSR is a thermoset: heat cures it to a solid that will not remelt, unlike thermoplastics.
• Best for seals, gaskets, diaphragms, valves, and overmolded components in medical, food, and electronics.

Understanding Liquid Silicone Custom Rubber Parts

Liquid silicone rubber (LSR) is a two-part platinum-cure silicone material known for its excellent thermal stability, flexibility, and biocompatibility. Guangdong Anlin Technology offers premium LSR for injection molding of precision components.

The key attributes of LSR include:

• Hardness
• Tensile strength
• Compression set
• Fluid resistance

The benefits of medical-grade LSR over elastomeric materials include:

• Bio-inert material in compliance with ISO 10993, USP Class VI and RoHS standards
• Ability to be sterilized with a variety of methods such as Autoclave, ETO, E-beam and Gamma radiation processes
• Low viscosity that allows flow to all parts of the mold
• Excellent stability over a broad range of temperatures 150°F to 450°F
• Low compression set
• Self-adhesive LSR that chemically adheres to plastics without the need for priming
• Ability to maintain its resiliency, flexibility and capability to transfer mechanical force at extreme temperatures

LSR has superior electrical insulating qualities even under the most severe environmental conditions. The manufacturer can acquire mold cavities specifically tailored to achieve different surface textures for parts and products.

Real-World Example

A drug-delivery device needed a silicone septum that stayed sealing-tight after 200 autoclave cycles. Switching from a hand-assembled HTV gasket to an automated LSR part eliminated flash and cut leak rejects, because LSR's self-degating injection holds about ±0.02 mm without secondary trimming. The part count rose while scrap fell.

Standards & Further Reading

LSR follows ASTM D1418 (VMQ nomenclature) and ISO 1629:2013. Medical and food grades reference ISO 10993, FDA 21 CFR 177.2600, USP Class VI, and the ISO 13485 quality system.