Polyesters (PET, PBT) and nylons (PA 6, 66, 46) are produced by melt
condensation processes. During such process the molecular weight (MW) of the
resin increases steadily, as the viscosity of the melt does. In practice, the
polycondensation reaction, and hence the resulting MW, is limited to a certain
viscosity range. Polymers prepared in this way are suitable for many
applications. However, for heavy duty applications higher MW products are
necessary, which can be achieved by post-condensation or chain extension.
The most common post-condensation process so far is solid state
post-condensation (SSP) in batch tumble driers. Other post-condensation
technologies comprise continuous SSP or melt finishers. The most important
applications areas for high MW products are:
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PET and PA industrial yarns/fibres, monofilaments and strapping
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PET and PA recycling
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PET custom containers/carbonated soft drink bottles and films
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PA, PET and PBT engineering plastics for E&E and automotive
