Synthesis and properties of hydroxyapatite nanorod‐reinforced polyamide 6 nanocomposites

BACKGROUND: Polyamide 6 (PA6)/hydroxyapatite (HA) nanocomposites, which combine the bioactivity and biocompatibility of HA and the excellent mechanical performance of PA6, have emerged as new biomaterials with potential applications in the clinical setting. It has been shown that these nanocomposites show good similarity to natural bone in terms of chemistry and mechanical properties. RESULTS: In this study, highly crystallized hydroxyapatite nanorods (HANR) were used to fabricate PA6/HA nanocomposites via in situ hydrolytic ring‐opening polymerization of ε‐caprolactam. The effect of the HANR on the thermal stability, crystallization behavior and hydrogen bonding of PA6 was investigated using thermogravimetric analysis, differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy, respectively. It was found that HANR can obviously increase the crystallization temperature and decrease the degree of supercooling. In addition, the thermal degeneration temperature of PA6 is also increased by the incorporation of HANR. FTIR analysis of the hydrogen bonded NH stretching vibration revealed that, with increasing HANR loading, the hydrogen bonded NH stretching band shifts to higher frequency and decreases in intensity. CONCLUSION: The thermal stability and crystallization ability of PA6 are improved considerably by the incorporation of HANR. However, the hydrogen bonding strength is weakened and the degree of ordering of hydrogen bonding is reduced by the incorporation of HANR, which can be explained by the formation of hydrogen bonds at the interface between OH groups of HANR and the NH or CO groups of PA6.