Nonisothermal melt‐crystallization kinetics of hydroxyapatite‐filled poly(3‐hydroxybutyrate) composites

Abstract

The knowledge of biomedical implants ranging from drug delivery devices to tissue engineering and based on bioresorbable polymer composites is increasing, but the study of the crystallization kinetics of these kinds of composites is seldom a concern. The focus of our experimental research was the nonisothermal-crystallization behavior of poly(3-hydroxybutyrate) (PHB)/hydroxyapatite (HA) composites, which was monitored by means of differential scanning calorimetry at different cooling rates. Various macrokinetic models were applied to describe the process of nonisothermal crystallization. The results showed that the modified Avrami model and Mo's approach could describe the nonisothermal crystallization of the composites very well, but the Ozawa analysis alone was thought to be rather inapplicable. The values of the half-time and kinetic crystallizability showed that the crystallization rate increased with increasing cooling rates for both PHB and the composites. The HA particles served as additional nucleation sites, and low levels of HA resulted in dramatic increases in the crystallization rate with respect to pure PHB; however, high HA contents (> 20 wt %) clearly retarded the growth process. The activation energy for nonisothermal crystallization was evaluated with the Kissinger method and was found to vary with the incorporation of HA.

Nucleating and retarding effects of nanohydroxyapatite on the crystallization of poly(butylene terephthalate-co-alkylene dicarboxylate)s with different lengths

“…In Figure 3, the non-isothermal melt-crystallization exotherms of PBXT copolymers and their corresponding composites containing nHAp have been shown for four different crystallization rates (Φ). Based on these curves, the peak temperature (Tc) at which the sample exhibited the fastest crystallization, and the onset temperature (T0) [43] could be easily obtained. Both Tc and T0 increased as expected, when Φ decreased.…”

Water absorption and solubility of PHBHV/HA nanocomposites

“…The combination of bioactivity and biodegradability makes it possible to apply these in the human body without secondary surgery. A lot of effort has been put into the fabrication, crystallization, mechanical properties, bioactivity and biocompatibility of this kind of biomaterial [2][3][4][5][6][7][8][9]. It has been noted that bone implants and tissue repair are heavily dependent for their success on a wet environment [10].…”

Environmentally friendly polymer nanocomposites using polymer matrices from renewable sources

“…In addition, PHB exhibits poor thermal stability at temperatures near its melting point. To enhance some of these properties, nanocomposites based on primarily clays and other nanoparticles, such as CNTs, [125][126][127] HA, [128][129][130] and silver, 132 have been produced. However, only preparation methods for PHA/clay nanocomposites are presented here, due to the relative abundance of literature on them compared to other nanoparticles.…”