Abstract
BackgroundHigh Density Polyethylene (HDPE) is one of the most often used polymers in biomedical applications. The limitations of HDPE are its visco-elastic behavior, low modulus and poor bioactivity. To improve HDPE properties, HA nanoparticles can be added to form polymer composite that can be used as alternatives to metals for bone substitutes and orthopaedic implant applications.MethodIn our previous work (BioMedical Engineering OnLine 2013), different ratios of HDPE/HA nanocomposites were prepared using melt blending in a co-rotating intermeshing twin screw extruder. The accelerated aging effects on the tensile properties and torsional viscoelastic behavior (storage modulus (G’) and Loss modulus (G”)) at 80°C of irradiated and non-irradiated HDPE/HA was investigated. Also the thermal behavior of HDPE/HA were studied. In this study, the effects of gamma irradiation on the tensile viscoelastic behavior (storage modulus (E’) and Loss modulus (E”)) at 25°C examined for HDPE/HA nanocomposites at different frequencies using Dynamic Mechanical Analysis (DMA). The DMA was also used to analyze creep-recovery and relaxation properties of the nanocomposites. To analyze the thermal behavior of the HDPE/HA nanocomposite, Differential Scanning Calorimetry (DSC) was used.ResultsThe microscopic examination of the cryogenically fractured surface revealed a reasonable distribution of HA nanoparticles in the HDPE matrix. The DMA showed that the tensile storage and loss modulus increases with increasing the HA nanoparticles ratio and the test frequency. The creep-recovery behavior improves with increasing the HA nanoparticle content. Finally, the results indicated that the crystallinity, viscoelastic, creep recovery and relaxation behavior of HDPE nanocomposite improved due to gamma irradiation.ConclusionBased on the experimental results, it is found that prepared HDPE nanocomposite properties improved due to the addition of HA nanoparticles and irradiation. So, the prepared HDPE/HA nanocomposite appears to have fairly good comprehensive properties that make it a good candidate as bone substitute.
Highlights
Bioactive nano-ceramic reinforced polymer has been under study as bone substitutes since early 1980s [1,2,3,4,5,6,7,8]
The results indicated that the crystallinity, viscoelastic, creep recovery and relaxation behavior of High Density Polyethylene (HDPE) nanocomposite improved due to gamma irradiation
The melt flow index (MFI) of HDPE/HA strongly decreases with gamma irradiation and HA nanoparticles content
Summary
Bioactive nano-ceramic reinforced polymer has been under study as bone substitutes since early 1980s [1,2,3,4,5,6,7,8]. High Density Polyethylene (HDPE) is one of the most often used polymers in biomedical applications such as bone substitutes and orthopedic prostheses. To improve HDPE properties, different types of ceramic nano-particles can be added to form polymer matrix composite that can be used as alternatives to metals for bone substitutes and orthopedic implant applications [16,17,18]. The HDPE viscoelastic and creep behavior describe its deformation under load with time and give useful data about the long term integrity of the material in such applications [17,18,19,20,21]. To improve HDPE properties, HA nanoparticles can be added to form polymer composite that can be used as alternatives to metals for bone substitutes and orthopaedic implant applications
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