Structural evolution of uniaxial tensile‐deformed injection molded poly(ɛ‐caprolactone)/hydroxyapatite composites

It is essential to examine the mechanisms of plastic deformation of polymer composites under external loads and large strains, especially if the material is intended to be used in a dynamic environment. This work investigated the variation of structure as well as the properties of poly(ɛ‐caprolactone) (PCL) deformed under different tensile draw ratios and strain rates. The PCL/HA composites were prepared by melt mixing the PCL with up to 10 wt% HA in a twin‐screw extruder. The deformation behavior of the PCL/HA composites revealed a strong correlation between the mechanical response and the accompanying structural transformations. It was found that the strain rate and stretching ratio played important roles in modulating the molecular orientation and crystallization of the PCL/HA composites. The increase in strain rate from 0.2 to 100 mm/min led to the variation of crystallinity from 56.81% to 67.50%. With an increase of the strain rate, the chain extension rate along the stretching direction increased faster than the chain relaxation, which improved the orientation of the polymer chains. The crystallinity and orientation of the deformed PCL/HA composites increased with an increase in draw ratio. The composites also possessed enhanced yield strength resulting from an increased strain rate. POLYM. COMPOS., 38:1771–1782, 2017. © 2015 Society of Plastics Engineers