Poly(propylene fumarate)/(calcium sulphate/β-tricalcium phosphate) composites: Preparation, characterization and in vitro degradation

This study aimed to prepare a poly(propylene fumarate)/(calcium sulphate/β-tricalcium phosphate) (PPF/(CaSO4/β-TCP)) composite. We first examined the effects of varying the molecular weight of PPF and the N-vinyl pyrrolidinone (NVP) to PPF ratio on the maximum cross-linking temperature and the composite compressive strength and modulus. Then the in vitro biodegradation behaviour of PPF/(CaSO4/β-TCP) composites was investigated. The effects of varying the molecular weight of PPF, the NVP/PPF ratio and the CaSO4/β-TCP molar ratio on the weight loss and the composite compressive strength and modulus were examined. The cross-linking temperature, which increased with increasing molecular weight of PPF and NVP/PPF ratio, ranged from 41 to 43 °C for all formulations. The mechanical properties were increased by a decrease in the NVP/PPF ratio. For all formulations, the compressive strength values fell between 12 and 62 MPa, while the compressive modulus values fell between 290 and 1149 MPa. The weight loss decreased either with increasing molecular weight of PPF or with decreasing NVP/PPF ratio and CaSO4/β-TCP molar ratio during degradation. The compressive strength and modulus increased with decreasing NVP/PPF ratio or decreasing CaSO4/β-TCP ratio. The greatest weight loss over 6 weeks was 14.72%. For all formulations, the compressive modulus values fell between 57 and 712 MPa and the compressive strength fell between 0.5 and 21 MPa throughout 6 weeks degradation. Scanning electron microscopy and X-ray diffraction analysis of the PPF/(CaSO4/β-TCP) composites demonstrated that hydroxyapatite was deposited on the surface of CaSO4/β-TCP granules during degradation.