Thermoplastic processing methods

The polymer melts at 216°C and above this temperature shows better cohesion of the melt than PTFE. It may be processed by conventional thermoplastics processing methods at temperatures in the range 230-290°C. Because of the high melt viscosity high injection moulding pressures are required. 

Figure 2.9. Market shares of the main thermoplastic processing methods 42...

These materials have the functional requirements of elastomers (extensibUity and rapid retraction) but processability similar to that of rigid thermoplastics. The principal advantages of the TPEs compared to vulcanized rubber are (1) reduction in compounding requirements, (2) easier and more efficient processing cycles, (3) scrap recycling, and (4) availability of thermoplastic processing methods. Generic classes of TPEs include... 

Unlike many conventional thermoplastic processing methods that utifize resin as pellets, in compression molding the resin charge is available in several forms. Common are granules, a coarse powder, that when heated and pressurized liquefy and cure to... 

Thermoplastic composites can be classified according to use, cost, performance, or processing methods. In the following discussion of the chemistry of the resin systems utilized in composites, three classes are considered ... 

When the material is allowed to cool it solidifies again. This cycle of softening by heat and solidifying on cooling can be repeated more or less indefinitely and is a major advantage in that it is the basis of most processing methods for these materials. It does have its drawbacks, however, because it means that the properties of thermoplastics are heat sensitive. A useful analogy which is often used to describe these materials is that, like candle wax, they can be repeatedly softened by heat and will solidify when cooled. 

Just to give an idea of the importance of the various processing methods, the shares of the major processes used for the most used thermoplastic (polyethylene) are roughly ... 

Figure 2.9 gives some indications of the distribution of thermoplastic consumption according to processing method ... 

There are many solutions according to the materials, output and processing methods, for example rigid beam, damping foam and skin with various thermoplastic versions such as ... 

Perfluorinated thermoplastics are generally rather permeable, especially PTFE because of the processing methods used. 

Some thermoplastics, polyethylene or EVA for example, can be cured before use to improve some performances. Tlie main processing methods involve ... 

The processing methods will be selected according to the importance of the series, part sizes and targeted properties. Table 6.1 suggests some processes, for thermoplastic and thermoset composites, according to the part sizes and production outputs. 

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