抄録
The aim of this paper is to investigate the influence of the surface modification ratio on the tensile strength of the hybrid-interface-controlled HAp/PLA composite materials. Here, pectin and chitosan were selected as the surface modification polymers for the HAp particles. In addition, o-nitrobenzyl alcohol was selected as the photodissociable protecting groups to avoid the chemical reaction between the surface modification polymers. First, the critical amount of the surface modification polymers for the whole surface modification of the HAp particles was evaluated. Then, the tensile tests were carried out for the hybrid-interface-controlled HAp/PLA composites with the various surface modification ratio. As a result, the FT-IR measurement revealed that the positively and negatively charged region of the HAp surface can be fully modified by pectin of 11 [wt%] and chitosan of 0.6 [wt%], respectively. Based on this result, the surface modification ratio of the hybrid-interface-controlled HAp particles could be evaluated under the assumption that the 50 [%] of the HAp surface is positively charged whereas the another 50 [%] is negatively charged. As a result of the tensile tests of the HAp/PLA composites, the tensile strength drastically decreased by the hydrolysis in the case that the surface modification ratio was 0 [%]. On the other hand, the decrease in the tensile strength was quite small in the case that the surface modification ratio was 75 [%]. It is notable that the hydrolytic degradation in the tensile strength was suppressed in the early stage and then accelerated after the 2-week hydrolysis, in the case that the surface modification ratio was 50 [%]. This result suggests that the simultaneous optimization of the hydrolytic and fracture properties of the hybrid-interface-controlled HAp/PLA composites would be enabled by the control of the surface modification ratio.
