Crystallization Properties of Polycaprolactone Induced by Different Hydroxyapatite Nano-Particles

Abstract

Polycaprolactone (PCL) composites were synthesized by two grades of hydroxyapatite (HA) nano-particles, namely, HA1 (prepared in our laboratory) and HA2 (purchased from commercial). The molar ratio of Ca/P for HA1 analyzed by ICP was 1.68 and 1.60 for HA2. The number average molecular weight of the polymers was measured by ¹H NMR. The crystallization behaviour of the samples was characterized by DSC, XRD and polarized light micrographs (PLM). The results indicated that polycaprolactone prepared by different HA nano-particles had slightly change in the number average molecular weight for the same content of HA. But the crystallization behaviour of the nano-HA/PCL samples had identical change tendency with the change of HA content in the samples. Both grades of HA nano-particles could increase the crystallization temperatures (T_c) of PCL from 25-28 °C, decrease the melting temperatures (T_m) from 61-55 °C and decrease the crystallinity of PCL from 55 to 39 %. When the content of nano-HA in the composites was 5 wt %, the thermal decomposition temperature could be elevated about 100 °C. The results for measurements suggested that the nano-HA/PCL composites with analogical properties could be obtained by the same content of HA either prepared in our laboratory or purchased from commercial.