Differences between Elastomers and Thermoplasts

At room temperature, an uncured elastomer can be a soft, pliable gum or a leathery, flexible solid, whereas an engineering thermoplastic is a rigid solid. Molecular mobility is the fundamental property that accounts for the differences among elastomers and the differences between elastomers and engineering thermoplasts. 

Engineering thermoplastics have glass-transition temperatures that fall in a wide temperature range, extending well above and below room temperature. Elastomers in the uncured state have glass-transition temperature well below room temperature. 

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