Liquid Silicone Rubber Injection Molding Manufacturer

Liquid silicone rubber injection molding manufacturer (LSR) is a high-performance two-part thermosetting elastomer with unique organic and inorganic properties (watch this video). This silicone elastomer has a typical viscosity range of 500,000 to 2,000,000 centipoise (cps). Due to its wide process applicability, high temperature stability, low temperature flexibility, excellent weather resistance, long service life, good sealing performance, easy coloring and chemical inertness, LSR is widely used in many fields. LSR is commonly used in aerospace, automotive, consumer products, healthcare and textile industries.

Manufacturing process

Liquid silicone rubber is mainly made of silicon, a non-metallic element commonly found in the earth’s crust. It is naturally found in clay, quartz, rocks and sand. During the manufacturing process, methyl vinyl polymer, silica filler and other additives are first added to the internal planetary mixer. The high shear force generated by the planetary motion makes the polyvinyl siloxane matrix reach a uniform state of mixing. The mixing process takes a long time, and then the mixture is divided into two equal parts, called component A and component B:

Component A: contains platinum catalyst
Component B: contains hydride crosslinker and inhibitor
The mixed materials are then divided into containers of matching capacity, such as 200 liters (55 gallons) or 20 liters (5 gallons).

Advantages of LSR

LSR has many advantages, including efficient automated production processes, fast curing cycles, excellent production efficiency, multi-cavity mold application capabilities, extremely low flash tolerance, high-strength products, and low viscosity resulting in lower injection pressures. In addition, LSR also has the ability to be overmolded and injected twice, making it one of the fastest-growing technologies in recent years.

LSR molding process

LSR molding process is significantly different from traditional thermoplastic molding processes and is often considered to be a “reverse operation.” During the LSR molding process, the mold is actually kept heated while the screw and barrel are cooled. This process design allows the mixed LSR to begin to solidify at room temperature, but the solidification rate will accelerate after the addition of heat. Therefore, after the two components are introduced, a proper chilled water system is required to delay the solidification process. The optimal cooling temperature of the equipment is about 70 degrees Fahrenheit (about 21 degrees Celsius).