Technology Knowledge

Liquid Silicone Rubber Injection Molding


What is injection molding of LSR?

Injection molding of liquid silicone rubber (LSR) is a process to produce pliable, durable parts in high volume.

Liquid silicone rubber is a high purity platinum cured silicone with low compression set, good stability and ability to resist extreme temperatures of heat and cold ideally suitable for production of parts, where high quality is required. Due to the thermosetting nature of the material, liquid silicone injection molding requires special treatment, such as intensive distributive mixing, while maintaining the material at a low temperature before it is pushed into the heated cavity and vulcanized.

Chemically, silicone rubber is a family of thermoset elastomers that have a backbone of alternating silicon and oxygen atoms and methyl or vinyl side groups. Silicone rubbers constitute about 30% of the silicone family, making them the largest group of that family. Silicone rubbers maintain their mechanical properties over a wide range of temperatures and the presence of methyl-groups in silicone rubbers makes these materials extremely hydrophobic, making them suitable for electrical surface insulations.

Characteristics of LSR

Liquid silicone rubber is high-purity platinum cured silicone. LSR’s physical, chemical and thermal properties make it highly suitable for products where performance, durability and high quality are a necessity.

Additionally, liquid silicone rubber allows for coloring or transparency in the finished product. Depending on their chemical composition, these materials can also serve as insulators or conductors.

LSR liquid injection molding is the preferred method for molding precision, delicate components. The process is clean and offers precision, accuracy, and high output. When combining the properties of LSR with the clean manufacturing process of liquid injection molding, the result is products that offer superior resilience and performance.


Typical applications for liquid silicone rubber

LSR are products that require high precision such as seals, sealing membranes, electric connectors, multi-pin connectors, infant products where smooth surfaces are desired, such as bottle nipples, medical applications as well as kitchen goods such as baking pans, spatulas, etc. Often, silicone rubber is overmolded onto other parts made of different plastics. For example, a silicone button face might be overmolded onto a Nylon 66 housing.


Manufacturing Processof LSR

Liquid silicone rubber (LSR) is a thick liquid polymer that uses a clean liquid injection molding process for producing LSR molded components.

LSRs used in the liquid injection molding process are two-part, platinum-cured polymers, the most stable. Platinum-cured LSR is received in 2 drums – A & B. When the A & B material components are pumped into the injection barrel of the molding machine, the materials combine and the vulcanization or curing process begins. If colored parts are desired, a third liquid with the color pigment is pumped into the barrel as well. The curing process is further accelerated when it is injected into the heated mold cavities where it solidifies and forms to the exact part geometry.