Morphological correlations to mechanical performance of hydroxyapatite‐filled HDPE/UHMWPE composites

Abstract

ABSTRACTMelt mixed and injection molded hydroxyapatite (Hap) filled high‐density polyethylene/ultrahigh molecular weight polyethylene composites were assessed for their thermal, structural, morphological, and mechanical attributes. Differential scanning calorimetry was conducted to analyze the effect of Hap loading on various thermal transitions and their associated enthalpies. The microstructural attributes were characterized by conducting wide angle X‐ray diffraction and scanning electron microscopy (SEM) of cryo‐fractured surface. SEM micrographs of tensile fractured surface revealed the systematic reduction in the size of microfibrils indicating the suppression of local deformation. Improvement in low‐strain mechanical response and flexural properties accompanied with a consistent decrease in strain‐at‐break and toughness was witnessed with increasing Hap content. Toughness aspects were critically discussed in the realms of quasi‐static, dynamic mechanical and sudden impact testing approach. Dynamic mechanical analysis demonstrated the presence of prominent α and γ transitions in the crystalline and amorphous phase respectively. Tensile fractured surface morphologies of the investigated composites revealed a switch‐over from matrix dominated plastic deformation to Hap controlled quasi‐brittle fracture. Thus, our study fundamentally deals with the feasibility of designing polyethylene/Hap composites with superior mechanical properties for biomedical applications, especially for orthopedic implants. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41251.