Thermoplastic polymers appearances

In calculating the effect of fillers on costs one must remember that polymers are generally used by volume, while both filler and polymer costs are usually quoted by weight. Most mineral fillers are considerably denser than polymers (usually 2-3 times) and hence their effective cost is considerably higher than appears at first sight. Some idea of the equivalent volume cost for fillers in the main thermoplastic polymers is given in Table 1, using estimated 1996 European price levels. 

The addition of fillers to thermoplastic polymers usually affects their appearance. While not absolutely essential, it is generally regarded as beneficial if the filler produces a pleasant white appearance or has no effect on the colour. It is a distinct disadvantage if the filler produces dark colours and makes the composite harder to pigment. 

Mineral fillers can produce both pro-degradant and stabilising effects in thermoplastic polymers. The reasons for this are varied and complex with factors such as adsorption of stabilisers and the presence of detrimental trace impurities such as certain metals playing a part. Until recently this was a little explored area,but several useful reviews have recently appeared [31,32]. 

All materials belong to the class of semi-crystalline thermoplastic polymers. Characteristic appearances of spherulitic microstructures of the polymers are shown in Figures 4 and 5 for the examples of POM and PA66. 

Foamed phenolic polymer appears to be an excellent insulator, stable and cheap. There is much competition for similar outlets between thermosets and thermoplastics—urea and melamine, ABS, acetal, PP and Nylon. The phenolics have the advantage of low price, and a good combination of general performance when appropriately composed. On the other hand, use of thermoplastics is frequently preferable due to improved processing in mass production, in addition to the recyclability of wastes. 

Several reports have appeared in the literature which discuss the lowering of the viscosity of a thermoplastic polymer with the addition of a small amount of an LCP component. These studies have been performed on a variety of polymers... 

It thus appears that, in sharp contrast with (some) molten thermoplastic polymers, there is nearly no experimental evidence of a linear viscoelastic region for mbber materials, whatever low is the shear rate range investigated. 

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