What is liquid silicone rubber?

Liquid silicone rubber (LSR) has emerged as an exceptionally versatile elastomer material utilized across industries from automotive to medical devices. Its unmatched mechanical properties coupled with processing flexibility enable innovative applications. This article will explore what sets LSR apart from conventional rubbers and examine its composition, curing process, manufacturing methods, and usefulness in various products.

Composition of Liquid Silicone Rubber

The major components of LSR are siloxane polymers, fillers and additives. The siloxane backbone provides the rubber-like qualities, with vinyl groups along the chain facilitating crosslinking. Commonly used fillers are silica or alumina to reinforce the material. Additives include platinum-based catalysts to control curing kinetics and achieve desired material characteristics.

The silicone polymers remain liquid at room temperature. By carefully selecting the siloxane chemistry and additives, LSR can be optimized for different physical requirements, such as tensile strength, elongation, hardness, tear resistance, compression set, heat stability etc.

Curing Process for LSR

LSR cures via a two-step reaction process. First, the addition of a platinum catalyst leads to hydrosilylation, causing crosslinks between polymer chains. This transforms the liquid LSR into a non-sticky gum.

Second, further heating activates vulcanization to complete the curing, yielding a fully solid elastomer. Temperatures typically range from 100-180°C. The cure kinetics can be controlled by adjusting catalyst types and concentrations.

Manufacturing and Processing Methods

LSR lending itself to various processing methods is a key advantage. Liquid injection molding is most common, forcing LSR into hot molds to form the products. Casting and extrusion are also used. Often, textile or metal inserts are placed in the molds to reinforce products. Furthermore, LSR can be combined with other materials for composite fabrication.

Benefits and Applications of LSR

A unique capability of LSR is re-processability. Crosslinks can be broken to return products back to liquid form, which can then be remolded with additional LSR. This recyclability prolongs service life. Moreover, LSR demonstrates outstanding biocompatibility, making it a popular choice for medical devices. Custom colors can also be incorporated for consumer products.

In summary, LSR offers an exceptional balance of physical, chemical and processing properties. Continued development will open doors for LSR materials and products to enhance many facets of modern life. LSR's future across industries including automotive, electronics, medical and beyond is bright.