Molecular weight, effect overall crystallization rate

The rate of crystallisation will vary with molecular weight and nucleation density. Other PAEK will show similar generic behaviour but rates of crystallisation can very widely. In particular any unit in the chain that does not readily crystallise will retard the rate of crystallisation, reduce overall crystallinity and limit crystal size -reducing the melting point. This effect can be used to limit while maintaining Tg (as in PEKK) but excessively reduced crystallinity and crystallisation rate can cause problems with mould cycle times or properties such as fatigue and chemical resistance. 

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