HCR materials are very popular for electrical insulator and thermal insulators used on overhead power lines and in our lives.

HCR materials for electrical insulator

How did manufacture the insulator made from Silicone rubber materials?
Injection molding is the logical extension of compression molding. A press is also needed, but the molds are engineered to allow the uncured rubber to be pushed into the closed mold cavities through openings. To facilitate this process, the press must have additional moving parts to convey the uncured rubber into the injection area and this is done in two basic ways: one is to use a cylindrical stuffer box with a ram to press the HCR material into a screw which then fills the injection ram in a controlled fashion; the other is to feed the screw with a strip of uncured rubber. In either case, the injection ram is set up to push the same precise amount of rubber into the mold during every ‘shot’. The speed and efficiency of this process is more a function of mold engineering than material parameters since the HCR can be compounded to meet any processing requirements.

Injection and compression molding can also be ‘blended’ allowing manufacturers to mold directly onto an insulator’s structural elements. For example, producers commonly mold directly onto the fiberglass rod or even onto end fittings. In these cases, silicone primer is needed to enhance bonding. HCR silicone can be formulated to bond without primer, but then sticking to the mold may become a concern and formulations for insulators are typically designed rather to release easily from the steel or metal alloy tools to reduce cycle time.

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