Morphology, hydrogen-bonding and crystallinity of nano-hydroxyapatite/polyamide 66 biocomposites

Nano-composites for load-bearing bone repair consisting of nano-hydroxyapatite (n-HA) and polyamide 66 were prepared by co-precipitation in ethanol. The relationships between structure and property of the composites were studied. Infrared spectrum results showed that n-HA and PA66 were mainly linked by hydrogen-bonding, which mainly existed between OH of n-HA and amide of PA66. The X-ray diffraction results revealed that the introduction of n-HA to polymeric matrix would weaken the crystallinity of α2 crystals in PA66, and most of the PA66 crystals in the composite were α1 crystals. A differential scanning calorimetry pattern showed that the hydrogen-bonding between organic and inorganic phases in the composite enhanced nucleation spots and played the role of nucleating agent, which resulted in the increase of nucleating speed of PA66 in the composite. However, the relative crystalline degree of PA66 in the composite decreased with the increase of the content of n-HA (the degrees of crystallinity were 27.67% for pure PA66, 23.44% for 30 wt% n-HA/PA66 and 22.98% for 40 wt% n-HA/PA66) because of the high viscosity of the system caused by the addition of n-HA and the hydrogen-bonding between n-HA and PA66.