Formation and Properties of Hydroxyapatite–Calcium Poly(vinyl phosphonate) Composites

Ceramic–polymer composites composed of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) and calcium poly(vinyl phosphonate) salt were prepared by warm‐pressing powder mixtures of tetracalcium phosphate (Ca 4 (PO 4 ) 2 O, TetCP) and poly(vinyl phosphonic acid) (PVPA) at a weight ratio of 3.5:1. The effects of temperature (to 300°C), pressure (to 690 kpsi), or compaction time (to 1 h) on the extent of conversion were studied using X‐ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy coupled with energy dispersive spectroscopy. The conversion of TetCP to HAp and formation of the calcium poly(vinyl phosphonate) salt was enhanced at higher temperature, pressure, and/or longer compaction time. Mechanical property determinations showed both the tensile strengths and elastic moduli continuously increase with increasing temperature, pressure, and compaction time. However, the glass transition temperature values of the composites were only minimally higher than that of the unreacted polymer.