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One of the core values of Plastribution is its expertise – something that all of its suppliers and customers know they can rely on.
Industry know-how is a series of articles from Plastribution, exclusively available to the readers of Injection World and on its website
www.plastribution.co.uk, that shares this expertise to provide essential background on some of the common terminology and practices used within the plastics industry.
Whether to cover gaps in knowledge where high levels are assumed, or to provide clarity where terms of reference have become confusing, Industry know-how aims to provide clear explanations and, where appropriate, thought leadership to support industry growth.
In this first article, it addresses the wide range of terminology relating to the classification of thermoplastic raw materials that has evolved over time, and Plastribution’s approach towards transparency.
By definition, thermoplastics are a group of materials that can be repeatedly melted by the application of heat (or thermal energy), shaped into the required product, part or component, and ‘frozen’ to retain that shape through sufficient cooling. This process leads to a thermoplastic having a ‘thermal history’.
Because thermoplastics can be reshaped upon reheating a number of times, they are considered to be recylcable. Yet thermoplastics also demonstrate varying degrees of thermal instability.
Particularly at temperatures where they begin to melt or soften, thermal degradation of the polymer can start to affect its properties, with this rate of change increasing further if shear is also applied.
For the moulder this means that great care should be taken in selecting the correct quality of material for a specific application, where, for instance, a prime grade of material may be preferred to ensure the delivery of properties as specified on data sheets.
This particularly applies to plastic components that are exposed to hostile environments including contact with chemicals and at elevated temperatures.
Care should also be taken with materials containing additives such as fillers (see separate Industry know-how fact sheet on ‘Regrind Guidelines’)
For various reasons a wide range of terminology has evolved to describe the quality of the original polymer and materials that have been recovered or recycled. As can be seen from the table, this can lead to confusion.
Moreover, an increase in both consumer pressure and government legislation has promoted the use of recycled plastics, and more specifically recycled post-consumer waste, thereby adding to the list of materials available to choose from.
© Plastribution Limited. All rights reserved. 2011
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