According to performance of raw materials and forming methods, plastic mold can be classified into mold for thermosets and mold for thermoplastics.
Mold for thermosets is mainly used for compressing, transferring and plastic injection molding components, including compression mold, transferring mold and injection mold. Injection mold is less used for thermosetting plastics. The common mold for thermosets contains phenolic plastic (also called as Bakelite), amino polyethylene vinegar, epoxy resin, PDAP, silicone plastic, silicon ketone plastic, etc.
Mold for thermoplastic is mainly used for injection mold and extrusion molding of thermoplastic plastic. The mold contains PA, polyformaldehyde, polyethylene, polypropylene, polycarbonate, etc. The mould also includes hollow blow mold and vacuum forming mold.
Working conditions of plastic mold
Mold for thermosets: working temperature generally ranges from 160 to 250℃. During operation, die cavity sustains high unit pressure, commonly 160 - 200MPa. Some even can reach 600MPa. Cavity surface is easily worn and corroded during operation. And the mold will sustain higher impact load during ejection and spotting.
The mould can suppress various Bakelite powder system parts. A certain amount of ground pigment is added in raw materials and formed under hit-pressing. For this, both thermal load and mechanical load are higher. The filler cause more serious abrasion on die cavity.
Mold for thermoplastic: the working temperature is below 150℃. It sustains less pressure and abrasion than compression mold. Parts of plastic can resolve hydrogen chloride or hydrogen fluoride under fusion after being heated, causing corrosion on die cavity of mold.
The plastic mold does not contain solid filler during thermoforming. Nevertheless, jet flow is smooth when entering into die cavity. If fiber glass filler is contained, abrasion on runner and cavity surface will be highly intensified.