Modulation of mechanical and thermal properties of poly(lactic acid)/hydroxyapatite composites by interface crosslinking

Abstract

Poly(lactic acid) (PLA) is a biodegradable and bioactive thermoplastic polymer. It has been widely used for hard tissue applications in orthopedic and dental fields. However, PLA is not able to form a direct bond with bone and this limits its applications. Therefore, PLA and hydroxyapatite (HAp) composites have gained significant attention to improve PLA performance. However, agglomeration of HAp in PLA matrix due to unfavored interfacial interactions between PLA and HAp directly affects the mechanical properties and stability of PLA/HAp composites. In this study, 3‐(glycidyloxypropyl)trimethoxysilane (GLYMO)‐modified HAp particles (G‐HAp) were synthesized and then incorporated into the PLA matrix to prepare PLA/G‐HAp composites. PLA/G‐HAp composites were prepared by mixing G‐HAp at 50 wt% with PLA (10 wt% in chloroform) solution. The resulting mixture was dried, ground, and molded into cylindrical shapes by pressure, and cured under N2 atmosphere. The interface interactions of the obtained composites were elucidated by fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses. It was observed that increased crosslinking density in the interface resulted in rougher surfaces. Thermal analyses demonstrated that Tg of PLA shifted to higher temperatures in parallel with crosslinking density. Additionally, Vicker's hardness tests and compression tests were conducted to determine the effect of interfacial crosslinking, and improved hardness and Young's modulus were observed. In the final part of study, MTT assay was carried out to evaluate cytotoxicity of composites and PLA/G‐HAp displayed higher cytocompatibility compared to conventional PLA/HAp composite.Highlights GLYMO modified HAp led to changes in the surface properties of composites. Increased crosslinking caused rougher surfaces for composites. Tg shifted to higher temperatures in parallel with GLYMO mediated crosslinking. Composites containing GLYMO‐modified HAp particles exhibited significant improvement in mechanical properties.