Stress-relaxation models of nano-HA/PVA gel biocomposites

摘要

Nanohydroxyapatite reinforced poly (vinyl alcohol) (nano-HA/PVA) gel composites have been proposed as a promising biomaterial to replace diseased or damaged articular cartilage. In this paper, the logarithmic model and multimode Maxwell model were used to describe the stress-relaxation process of nano-HA/PVA gel bio-composites, respectively. The results showed that both models can precisely describe the stress-relaxation behavior of nano-HA/PVA gel composites and their maximum absolute errors are not in excess of 6 %. However, the logarithmic model is only an empirical model and lacks definite physical meaning. It is very difficult to distinguish each relaxation stage of the composites such as the rapid and slow relaxation stage for the logarithmic model. To the contrary, every element in the multimode Maxwell model possesses definite physical meaning and it is corresponding to a certain stress-relaxation mechanism. It cannot only accurately depict the stress-relaxation properties of nanohydroxyapatite reinforced poly (vinyl alcohol) gel composites but also can reveal the relaxation mechanism of the composites. The investigation on the mechanism showed that the stress-relaxation mechanism of the composites was mainly predominated by the synergistic effect of two mechanisms which were the stress-relaxation characteristics of nature articular cartilage and that of the polymer.