Injection Moulding of glasflled thermoplastics
Thermoplastics are used in injection moulding to create huge numbers of plastic products for a variety of uses. There are coupling agents which are used with the thermoplastics so the performance of the materials in the final product would be greatly enhanced. Two examples of glass filled thermoplastics are polyamide filled with glass fiber and the PBT filled with glass beads.
The polyamides are thermoplastic amorphous polymers which are highly recommended for the use of products which have good mechanical, thermal and chemical resistance. This is what makes them more expensive compared to the other thermoplastics.
The polyamide filled with glass fibre can be used as an injection moulding material for the manufacture of such items as moulded or extruded bars, rods and other shapes. These items are usually seen as very strong parts or components which are resistant to heat, have good dielectric properties and can withstand heat for up to 230 degrees Celsius or 446 degrees Fahrenheit. However this use is not just limited to these applications.
Before the polyamide filled glass fiber is used, it has to go through a drying process which should prevent brittleness on the final product, foaming though the injection moulding process or other injection moulding problems. A desiccant hopper dryer is usually recommended to dry the polyamide filled glass fibber material. If the process takes on a long run, then the resin has to be covered and re-dried if need be.
The injection moulding equipment used for this type of thermoplastic is the reciprocating screw injection moulding press which has a microprocessor control that is capable of closed loop control the press has to be fitted with a low compression ration and a constant taper screw. It is also important that the injection moulding machine should have a compression ration set at 1.1 and 1.5 to 1. There should be no check devices used.