Liquid Silicone Rubber (LSR) is a non-toxic, heat-resistant, flexible thermosetting material with high resilience. Its rheological behavior is mainly characterized by low viscosity, rapid curing, shear thinness and high thermal expansion coefficient.

LSR is divided into glue A and glue B. The ratio of the two is 1:1, which is controlled by A quantitative device, and then fully mixed through A Static Mixer. After injection pipe is injected, injection molding is carried out.

LSR is widely used in the healthcare industry, such as the manufacture of sealed infusion systems, coil dialysis filters, hearing aid components, baby pacifiers, maternal nipple covers, household appliances inhalation valves, medical equipment components, etc.

Its products are characterized by good thermal stability, cold resistance, excellent electrical insulation performance, good elasticity, waterproof and moisture-proof, acid, alkali and other chemical erosion, combustion will not produce toxic substances.

Molding process

LSR is A two-component liquid material, divided into A and B components. The operation of the mixer fully mixes A and B components in A precise 1:1 ratio. And because part of the product is colored design, so equipped with color pump set and color metering part. A+B components, additives, colors, etc. are fully mixed into the plasticizing system.

Liquid silicone rubber injection molding machine key components

1) Due to the low viscosity of LSR, material backflow and glue leakage should be considered in the processing process, so it is necessary to seal the screw.

2) Needle valve injectors should be used to prevent LSR curing.

3) Mixing and metering parts of A and B components.

Mold design
In mold design, there are generally the following forms:

1) hot runner
More waste material, simple design, low cost, mostly used for large products.

2) cold runner with needle valve
Can realize automation, short cycle.

3) cold runner without needle valve

Due to the LSR's high coefficient of expansion, which expands when heated and contracts slightly when cooled, the parts cannot maintain precise sidelining in the mold. Therefore, cold runner can be used to process LSR. LSR should be kept at a low temperature and flow rate. The cold runner adopts a closed system. Silicone rubber has significant thermal expansion characteristics, shrinkage rate of 2% ~ 4% (curing temperature of 150℃), and silicone rubber has the characteristics of deformation under pressure.