What Type of Silicone is Used for Molding?
In recent years, the application of liquid silicone rubber is more and more widely, its molding technologies have also got rapid development. Liquid silicone is a kind of non-toxic, heat resistant, high resilience flexible thermosetting material. Its rheological behavior is mainly characterized by low viscosity, fast curing, high shear thinning, and the thermal expansion coefficient.
Composed of liquid silicone vulcanization of products has strong adaptability to temperature, high purity, good transparency, less volatile matter content, oil resistant aging resistance, insulation and resistance to chemicals, etc. Liquid silicone injection molding normally is used to do silicone manufacturing for LSR parts for various industries, including automotive, construction, electronics, and healthcare.
How is Silicone Molding Done?
Among the liquid silicone moldings process, the Liquid Injection molding (Liquid Injection molding/LIM) technology is the first application. Liquid injection molding is A, B glue (composition as shown in table 1) by pumping system to the measurement system, Press 1:1 or another precise metering, conveying to the static mixer, mixing and then to the injection device, the injection device to mix after injected into the hot mold. Inside, the liquid silicone rubber will get a rapid curing reaction to form a silicone product with certain strength and elasticity.
In the composition of liquid silicone, the effect of catalyst and inhibitor is particularly important. Due to the liquid silicone needing a vulcanization reaction, so adding the catalyst is a necessary step to accelerate the curing reaction. When the curing temperature is up to 200 ℃, the curing rate of each mm thickness just needs 3 ~ 5 s.
Liquid silicone cannot long exist at the temperature of 40 ~ 50 ℃. If not reach the required vulcanizing temperature, liquid silicone rubber will also react slowly. Under this condition, inhibitors are needed. Inhibitors will be useless until liquid silicone rubber reaches vulcanizing temperature, and liquid silicone rubber will react quickly.
1) Compared with solid rubber molding, the process of liquid silicone injecti