Abstract
In this study three chemical agents Amino-propyl-triethoxy-silane (APS), sorbitol ended PLA oligomer (SPLA) and Hexamethylene diisocyanate (HDI) were identified to be used as coupling agents to react with the phosphate glass fibre (PGF) reinforcement and the polylactic acid (PLA) polymer matrix of the composite. Composites were prepared with short chopped strand fibres (l = 20 mm, ϕ = 20 µm) in a random arrangement within PLA matrix. Improved, initial composite flexural strength (~20 MPa) was observed for APS treated fibres, which was suggested to be due to enhanced bonding between the fibres and polymer matrix. Both APS and HDI treated fibres were suggested to be covalently linked with the PLA matrix. The hydrophobicity induced by these coupling agents (HDI, APS) helped to resist hydrolysis of the interface and thus retained their mechanical properties for an extended period of time as compared to non-treated control. Approximately 70% of initial strength and 65% of initial modulus was retained by HDI treated fibre composites in contrast to the control, where only ~50% of strength and modulus was retained after 28 days of immersion in PBS at 37 °C. All coupling agent treated and control composites demonstrated good cytocompatibility which was comparable to the tissue culture polystyrene (TCP) control, supporting the use of these materials as coupling agent’s within medical implant devices.
Highlights
Over the last two decades research has focused on development of materials that may provide solutions for issues such as stress shielding, corrosion, implant-removal surgery and risk of secondary fractures associated with removal of metallic implants
This study investigates the effects of these coupling agents on the composite mechanical properties and in vitro cytocompatibility is assessed using direct contact methods with human osteosarcoma cells
Selected coupling agents (APS, sorbitol ended polylactic acid (PLA) oligomer (SPLA) oligomer) improved initial flexural properties of random short fibre (l = 20 mm, φ = 20 μm) reinforced PLA composites by ~20 MPa
Summary
Over the last two decades research has focused on development of materials that may provide solutions for issues such as stress shielding, corrosion, implant-removal surgery and risk of secondary fractures associated with removal of metallic implants. A number of studies have shown the potential of phosphate glass particulates or PGF reinforced resorbable polymer composites Controlling the degradation of the fibre matrix interface and/or decreasing polymer swelling would be vital in order to manufacture resorbable composites that retained their mechanical properties for the desired period of time before resorption started. Improvement in flexural strength and modulus values by ~25 MPa and ~1 GPa respectively, for PGF reinforced polyorthoester was reported with silane treatment [23]. In this study the above three chemical agents (APS, SPLA and HDI) were identified and investigated as potential coupling agents to react with the PGF reinforcement and the PLA polymer matrix. The composite manufacturing process and testing is discussed along with cytocompatibility studies conducted over a 7 day period
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