Abstract:

The objective of this work is to demonstrate how the viscoelastic, thermal, rheological, hardness, wear resistance and fracture behavior of bioinert high-density polyethylene (HDPE) can be changed by the addition of hydroxyapatite (HAP) nano particles. Also the effects of accelerated thermal ageing on the composite properties have been investigated. Different weight fractions of HAP nano particles up to 30 wt% have been incorporated in HDPE matrix by using melt blending in co-rotating intermeshing twin screw extruder. The fracture toughness results showed a remarkable decrease in proportion to the HAP content. The differential scanning calorimetry results indicated that the melting temperature and crystallinity were affected by the addition of HAP nano particles into the matrix. The complex viscosity increased as the percentage of HAP increased due to the restriction of the molecular mobility. The dynamic mechanical analysis results revealed that higher storage modulus (8.3 × 10¹¹ Pa) could be obtained in the developed HDPE/HAP in 30 wt% compared to neat HDPE (5.1 × 10¹¹ Pa). Finally, the hardness and wear resistance of HDPE were improved significantly due to the addition of HAP nano particles. The changes in the HDPE and its nano composite properties due to ageing showed that the HDPE and its nano composites crystallinity increased while the fracture toughness, hardness, wear resistance, storage and loss modulus decreased.

Key words: High-density polyethylene (HDPE), Hydroxyapatite (HAP), Hardness, Accelerated ageing, Dynamic mechanical analysis (DMA), Differential scanning calorimetry (DSC), Fracture