HDPE/HA composites obtained in solution: Effect of the gamma radiation

Abstract

Radiation is employed to sterilize composite materials used in the biomedical field. Due to the changes induced by radiation onto polymeric materials, it is important to study variations in their melt flow index (MFI), as well as in their mechanical and thermal properties. In this work, those previous parameters were determined in composites obtained via solution of a high-density polyethylene (HDPE) in decalin, with different amounts of hydroxyapatite (HA), varying from 10 to 30 parts per hundred, after being exposed to gamma radiation at absorbed doses between 25 and 100kGy. After the irradiation, the MFI of HDPE dissolved in decalin and precipitated afterwards and without filler increased from 6 to 24g/10min at the highest absorbed doses. This behavior was also observed in composites with 10pph of HA, being the increase less pronounced, specifically in the range between 50 and 100kGy. Composites with 20 and 30pph of HA showed a maximum MFI value at 50kGy, which decreased at higher doses. This implies that the filler begin to exert an influence because it does not melt at the test temperature and consequently, it does not flow. It was observed that Young’s modulus increased with HA addition due to rigidity of the ceramic filler. Radiation did not significantly affect this tensile property. On the other hand, the tensile strength did not show significant variations at the different doses but the filler content did affect this property improving it. Finally, elongation at break showed a drastic decrease with filler addition. When the thermal behavior was studied it was noticed that crystallization and melting temperatures remained unchanged. Instead, crystallinity degree slightly increased in the composites, and a little decrease was obtained when they were irradiated.