Thermoplastic VS Silicone rubber

plastic product VS silicone product

It is easy to get confused between thermoplastic injection molding and silicone liquid rubber injection molding cause the finished products look quite the same, today we will be introducing you a little bit about silicone rubber injection molding.

Silicone rubber liquid injection molding is a manufacturing process commonly used to make silicone parts (considered a subset of rubber or thermoset) that need to withstand extreme conditions, regardless of the industry. The process is an injection molding process at heart, meaning that materials are injected into a pre-made mold, where heat accelerates part curing. Then, the process repeats itself until the part run is complete.

Typical applications for liquid silicone rubber 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 over-molded onto other parts made of different plastics. For example, a silicone button face might be over-molded onto a Nylon 6,6 housing.

Liquid silicone rubber injection molding machine appears to look just like thermoplastic injection molding machines. Both types of presses use the same basic machine parts, clamp unit, and injection unit.

Silicone machine
Plastic injection machine

Unlike the high pressures used to mold thermoplastic parts, liquid silicone injection pressure is in the range of 800 PSI. The purpose of the clamp is to container the expansion force of the silicone material, by keeping the mold closed as the silicone cures.

The injection unit for liquid silicone runs cool with a water cooled barrel and nozzle to prevent the liquid silicone from curing.

Thermoplastic injection units run the opposite way, they need the barrel and nozzle to be heated to 300F or more to keep the material moving.

Liquid injection molding units also run at lower pressures (under 1,000 PSI), while the thermoplastic counterparts run at tens of thousands of PSI.

Injection molding machine

Cost of liquid silicone rubber tooling

Tooling for injection molding of silicone rubber components generally costs less than tooling for thermoplastic injection molding. Tooling costs will vary depending on size and part detail.

If you want to know more about plastic injection molding, please see the article down below:
What is two color / two shot 2k injection molding
Things you must know about injection molding
2k two-color injection mold maker factory you must know !

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