Over the years there have been numerous improvements in polymer processing and how we produce our plastic products. Many accomplishments have been introduced, control has been made easier and inefficiencies have been fixed and made efficient. Yet still one of the most overlooked problems in polymer processing is that of temperature control. People still forget that different temperatures at different stages in polymer processing can have wide ranging effects on the finished product. Not only this, but temperature is important for the polymerisation reactions to take place in the first instance.
For polymer processing to take place, new bonds between the plastic molecules need to be created. Yet the only way bonds can be made is through the use of energy. So simply enough, the plastic breaks its previous bonds and makes new bonds in the form the manufacturer wants, all through the use of a bit of energy. But where does this energy come from? In a lot of cases the energy comes from heat. By keeping the plastics at the optimum temperature for the right reaction, termed the ‘activation energy’, perfect polymer processing can take place. If the temperature is too low, there is not enough energy and so the reaction is probably not going to happen. If the temperature is too high, the producer runs the risk of losing control of the reaction, or even creating a completely different and unwanted reaction. In either case it is important to maintain the temperature at the right level.
One of the other reasons why temperature is so important is because it can have an effect on the end product. Whether the plastic is made at a relatively warm or cold temperature can have such a profound effect as to change the plastics malleability, or flexibility. A common example is polyethyl terephthalate often used in soft drink bottles. When polyethyl terephthalate is warmer it is made more supple and more malleable. When colder the opposite happens and the plastic becomes more difficult to stretch. One of the unseen problems with this is that the thickness of the plastic after polymer processing can be different in different areas. This can give an unattractive grainy appearance which will ruin the effect of the product. It also gives areas of weakness, damaging the reliability.
Through the realisation of these effects it has come to be known that for a manufacturer to effectively undertake polymer processing, they must understand the effects that temperature has on the process. By understanding these fundamental effects and the measurements that should be taken to manage them, polymer processing can be used in a much more controllable manner. Because of this simple recognition of temperatures importance, massive advancements in temperature control have been made. We now know that we can change or maintain temperature in three different places. These places are in the raw materials temperature, the machine temperature and the process temperature. Likewise we have shown that it is possible to use this process, not through actively changing and controlling temperature, but through removing those processes that change and alter the temperature away from what is wanted. Overall the importance of temperature has been understood and is now freely available for us to use to our advantage.
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