Hydroxyapatites Modified By In Situ (Co)polymerization And Correlative Polymer-matrix Composites

With the rapid development of medicinal techniques, the traditional medicine materials, such as metals or alloys, ceramics and organic compostes and so on, can not meet the needs of bone replacement and reconstruction. As the replacement materials for high load structure, polymer-matrix composites have a wide potential application in this field. Based on the assumption that combines the bioactivity of hydroxyapatite (HA) and the excellent mechanical and processing properties of polymer, the polymer/HA composites have attracted more and more attentions in bone replacement and reconstruction.The innovative points in this dissertation are as follows: (1) The polystyrene (PS) or poly (butyl acrylate) (PBA) chains were successfully covered or grafted on the surface of micro-sized HA or nano-sized antimony trioxide (NSb₂O₃) particles via in situ filler/monomer polymerization or filler/vinyl triethyoxyl silane (VTES)/monomer copolymerization, the molecular weight and distribution of polymer covered (grafted) on the surface of HA particles were measued by gel permeation chromatography (GPC); (2) The PS or PBA chains covered or grafted on the surface of micro-sized HA or nano-sized NSb₂O₃ particles via in situ polymerization or copolymerization, enhance the dispersion of HA or NSb₂O₃ particles in polymer matrix, thereby improve the mechanical properties of HIPS/HA, PS/HA, HDPE/HA composites, and HIPS/NSb₂O₃ nanocomposites. The effects of the polymer-coated thickness on the surface of inorganic particles, in-situ polymerization process and the particles size on the mechanical properties of those composites were investigated, and found out the a critical polymer-coated thickness on the surface of inorganic particles; (3) The abrasion mechanism of polymer compostites was explained better by the abrasive wear than the adhesive wear.The main contents and conclusions in the dissertation are divided into the following parts.The kinetics of in situ HA/St, HA/butyl acrylate (BA) and NSb₂O₃/St polymerizations were invesitaged. The results indicated that these inorganic particles do not inhibit the polymerization of monomers, the conversion of monomers reach near 100%, and the weight-average molecular weight of PS on the surface of HA particles via in situ polymerization or copolymerization is higher than 300,000.With the hydrolysis of alkyloxyl groups, reaction with silanol groups on the inorganic particles surface through dehydration and condensation to form Si-O bonds, VTES was grafted on the surface of inorganic particles, and vinyl groups were introduced on the particle surfaces. Thereby, the hydrophobility of the inorganic particles is improved, and can form stable emulsion micells for the followed in-situ copolymerization, the formed grafting copolymer has higher molecular weight and narrower distributuion than the those of the covering polymer via in-situ polymerization. In the other hand, the existence of vinyl groups favors the grafting reaction, the formed polymer chains are most grafted on the particle surfaces with high grafting percentage and efficiency. Due to the small dimensional effect, the grafting percentage and efficiency for in-situ NSb₂O₃/VTES/St copolymerization are higher than those for in-situ HA/VTES/St copolymerization.High impact polystyrene (HIPS)/HA, PS/HA, high density polyethylene (HDPE)/HA composites were prepared with the micro-sized HA particles modified by in situ polymerization or copolymerization. At the same time, HIPS/NSb₂O₃ nanocomposites were also prepared with modified nano-sized NSb₂O₃ particles via in situ polymerization or copolymerization. It will provide with a primary background for develop polymer/HA nanocomposites in next stage. The microstructure, thermal behavior and mechanical properties of those composites were systematically investigated. The results showed that the unmodified HA and NSb₂O₃ particles are easy to aggregate, and the interfacial adhesion is poor between the un-modified particles with composite matrix. After these particles were modified by in situ polymerization, the polymer coated on the HA and NSb₂O₃ surface enhances the dispersion of HA and NSb₂O₃ in matrixes, and improves the interfacial adhesion. Especially, after the HA and NSb₂O₃ particles are modified by in situ copolymerization, there are more polymer chains grafted on the filler surface, thereby the inorganic particles, especially nanosiezd NSb₂O₃ particles are more uniformly dispersed in composite matrix due to strong interaction between the matrix and the grafting polymer on the surface of the modified particles. Either by in situ polymerization or in situ copolymerization, the tensile and impact properties of the above composites are improved remarkably. And there exists a critical coated thickness for the polymer on the inorganic particles. Since in situ copolymerization is favorable to graft PS or PBA chains onto the inorganic particles, the properties of these composites are better than thoses of the composites modified by in situ polymerization, and the reinforcing and toughening of nano-sized particles to polymer matrix are better than those of nano-sized particles to polymer matrix.The wear properties of HIPS/HA, PS/HA, HDPE/HA composites were studies, and the abrasive abrasion mechanism was discussed. The results indicated that the abrasive wear can reasonably the abrasion behavior of polymer-matrix composites, and the toughness of composites is main factor for their wear resistance. Due to the reinforcing and toughening of the modified HA particles to HIPS, PS and HDPE, the wear properties of HIPS/HA, PS/HA, HDPE/HA composites are improved, and the mofication effect of in situ copolymerization is better than that of in situ polymerization.