EFFECT OF PROCESS ON MATERIAL PROPERTIES

Note With formulation changes (via additives, fillers, reinforcements, alloying, etc.) position of plastic can move practically any place in the pie.  

These plastics become soft when exposed to sufficient heat and harden when cooled, no matter how often the process is repeated. 

The plastics materials belonging to this group are set into permanent shape when heat and pressure are applied to them during forming. Reheating will not soften these materials. 

The dividing line between TP and TS is not always distinct. Cross-linked TSs are thermoplastic during the initial heat cycle and prior to the chemical cross-linking action. Other plastics may behave like crossed-link high density polyethylene, which normally is a TP but can be cross-linked, by high energy radiation or chemically while being processed, to become a TS called XHDPE (1-3, 8, 9, 11). 

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Melt Structures. High shear at a temperature not far above the melting point may cause a melt to take on too much molecular order. In turn, distortion could result. This subject is discussed further in this chapter in the section Effect of Process on Material Properties. ... 

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