There are many differences between LSR and traditional thermoplastic rubber processing, which increases the difficulty of processing. LSR is quite different from traditional thermoplastic materials in terms of shrinkage, demoulding, mold material, cold runner system, temperature control, etc., making LSR more difficult to process than ordinary thermoplastics.

The waterproof silicone ring of the smart phone is mostly formed on the original metal or plastic parts, and the volume is smaller than the commonly used silicone ring. The compatibility with the casing and accessories is higher, and it needs to be more precise (micro). Injection molding technology.

The key points for LSR to achieve precision injection molding are as follows:

(1) Adequate mixing of liquid silicone

ccurate mixing ratio: LSR is a two-component raw material of A and B. Before injection molding, it must be mixed according to precise 1:1. If it is a colored liquid silicone product, it must also accurately control the proportion of color paste.
Mixer: The static mixer is the key component in injection molding. The A and B glues can only be fully vulcanized and molded into the mold after the injection is fully and evenly mixed.

(2) Sealing and temperature control of injection molding machine parts
Due to the low viscosity of the LSR, it is necessary to consider the backflow and leakage of the material, and the screw must be sealed;

Since the mold is heated during the LSR molding process, in order to prevent the LSR from solidifying, a water-cooled nozzle can be used to ensure that the temperature is sufficiently low.

(3) Finished product control during injection molding
Parting line: Pre-considering the position and accuracy of the parting line helps to avoid entrainment and welding of air and avoid burrs;
Shrinkage: Although LSR does not shrink during injection molding, due to its extremely high coefficient of thermal expansion, it usually shrinks by 2% to 3% after demolding and cooling;
The position of the injection port: the actual product shrinkage rate needs to be considered;
Vacuuming: When designing the parting line, ensure that the mold is sealed, and the vacuum pump vacuums all the cavities through the clamp below the mold switch;

Demolding: Generally, the stripping technology of the fractionation column tray, the push pin and the air pusher is adopted, or the mold release is manual.

Mold temperature: LSR is vulcanized and formed during heating, and the temperature inside the mold must be controlled to be evenly distributed. The temperature difference is controlled at +/-10 °C.