Polyacetal processing conditions

The properties of the nylons are considerably affected by the amount of crystallisation. Whereas in some polymers, e.g. the polyacetals and PCTFE, processing conditions have only a minor influence on crystallinity, in the case of the nylons the crystallinity of a given polymer may vary by as much as 40%. Thus a moulding of nylon 6, slowly cooled and subsequently annealed, may be 50-60% crystalline, while rapidly cooled thin-wall mouldings may be only 10% crystalline. 

Bowman [192] conducted a systematic study of the structure-property relations of injection molded polyacetals (polyoxymethylene or POM) and observed correlations between process conditions, structures and mechanical properties. Barrel temperature effects were studied as they are known to influence both microstructure and mechanical properties [193]. Increased barrel temperature was shown to reduce the outer skin layer while increasing the extent of the equiaxed, unoriented core, resulting in a decreased tensile yield strength parallel to the injection direction. 

Bowman [157] conducted a systematic study of the structure-property relations of injection molded polyacetals (polyoxymethylene or POM) and observed correlations between process conditions, structures and mechanical properties. 

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