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Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Partially crystallized poly( -caprolactone) has been stored for up to 6 months at various temperatures from −18 to 50 ∘ C and the change in tensile properties, crystallinity and melting behaviour followed with storage time. The Young modulus, yield and drawing stress were observed to increase with time and at a rate which increased with storage temperature. These changes in tensile properties could be accounted for by the increase in crystallinity and were attributed to a thickening of the lamellae which reinforced the morphology and increased the stiffness of the polymer. The thickening of the lamellae accounted for the shift of the melting endotherms to higher temperatures with time. The stem lengths increased with the square root of the storage time and the rate increased with temperature corresponding to an activation energy of 40 ± 5 kJ mol −1 . It is considered that ageing occurred by a process of secondary crystallization by extension of the 'fold surface' into the adjacent melt and the thickening of the lamellae. The time dependence of growth can only be explained by small segments of the chain being incorporated onto the crystal on the time scale of the local segmental mobility which is independent of chain entanglements. This does not have the characteristics of a nucleation controlled process but is a thermally activated diffusion process the rate of which increases with temperature.

The kinetics of crystallization of poly(ecaprolactone), PCL, have been measured by FTIR spectroscopy using the absorbance of the crystalline and amorphous phase carbonyl bands at 1725 and 1735 cm -1 , respectively, to determine the fractional crystallinity as a function of time and over the temperature range 43-47°C. A comparison was also made with DSC which was found to have limited sensitivity such that it could only measure the primary stage of the crystallization and not the secondary. Both primary and secondary crystallization could be measured by FTIR spectroscopy with sufficient accuracy to measure the kinetics of each and limited only by the length of time over which the measurements were made.