Ageing and crystallisation of polycaprolactone

Partially crystalline polycaprolactone stored at different temperatures well above the glass transition temperature is found to age with the development of further crystallinity and an increase in melting point, yield stress and elastic modulus with time. The changes in mechanical properties are accounted for by the increased crystallinity, and the increase in melting point to an increase in lamellae thickness. Over the temperature range studied, the rate of ageing increase with temperature and the dependence of stem length on the square root of storage time observed are both consistent with diffusion control and inconsistent with nucleation control. It is concluded that partially crystalline polycaprolactone ages by a continuation of the crystallisation at a rate determined by the storage temperature and by the mechanism occurring prior to ageing