The penetration and accumulation of hydroxyapatite and the hydrothermal stability of collagen matrix material

Abstract

Abstract Hydroxyapatite (HAP) has been extensively used in the clinic, for example, for bone tissue repair, because of its outstanding performance. However, whether HAP can be utilized in other fields, such as leather manufacturing, remains unknown. The process of making leather from hide involves a hydrothermal treatment. Thus, in the present work, HAP was synthesized using a hydrothermal method with diammonium hydrogen phosphate and calcium nitrate as phosphorus and calcium precursors, respectively. The condition optimization test results indicated that high-purity HAP can be obtained when the reaction is carried out at 80 °C and pH 11, with surfactant added. To study the effect of HAP on cowhide and to determine whether it can be used as a tanning agent, tests of in vitro and in vivo HAP addition into cowhide were conducted. The cowhide was first subjected to a wet-end leather making process and then cut into samples. Samples were treated using different HAP addition methods, and experimental results obtained under different conditions were compared. Fourier-transform infrared spectroscopy analysis indicated that HAP added by both methods can react with cowhide. Physicochemical properties of cowhide were improved after reaction with HAP, specifically, the thermal stability was enhanced when HAP was synthesized in the skin. The thermal shrinkage temperature of the treated hide was 78 °C, which was higher than 54 °C for the control group samples. The hide tear strength was greatly enhanced because HAP synthesized on hide collagen caused the formation of a rigid module. Therefore, HAP has the potential to be used as a chrome-free tanning agent. This study demonstrated that the modification of cowhide by HAP was feasible and HAP tanning or HAP combination tanning was of practical significance.