Preparation And Properties Research Of Hydroxyapatite/Polylactic Acid Composite Films

In this research,nano hydroxyapatite was prepared by chemical precipitation method and template method,and its appearance,crystallinity,pore size and specific surface area were studied and characterized.Then the self-made nano hydroxyapatite(sample H2)and PBAT were used as fillers,and the composite films of two element systems and three element systems were prepared by different blending methods with polylactic acid as matrix.And the microstructure,mechanical properties,thermal properties,crystallinity,water vapor permeability and oxygen permeability of the composite films were studied.The results of FTIR and XRD showed that the concentration of reaction solutions had little effect on the crystallinity of nano hydroxyapatite.After adding different ratio of cationic surfactant CTAB,the crystallinity of nano hydroxyapatite has not been affected,and it has a porous nano rod-like structure.And the sample has the largest specific surface area and pore volume when the ratio of n(CTAB):n(HA)is 1:2.With the increasing content of nano hydroxyapatite,the elastic modulus of the HA/PLA composite films first increased and then decreased,the elastic modulus of 1%HA/PLA composite film is the largest,which is about 2794MPa.However,the tensile strength and elongation at break of the composite films did not be improved.The melting point and glass transition temperature of the composite films were affected a little,but the cold crystallization temperature decreased by about 8 degrees Celsius.The water permeability coefficient and oxygen permeability coefficient of composite films increase linearly.Therefore,the water vapor permeability and oxygen permeability of the composite films can be adjusted by adjusting the content of the filler.With the increasing content of nano hydroxyapatite,the change trend of modulus of elasticity,tensile strength and elongation at break of the HA/10%PBAT/PLA composite films is the same as that of the HA/PLA composite films.But the two kinds of composite films with the same nano hydroxyapatite content,the mechanical properties of the HA/10%PBAT/PLA composite films is better than the HA/PLA composite films.For example,the elastic modulus of 1%HA/10%PBAT/PLA composite film is about 3571MPa,which is increased by about 28%compared with 1%HA/PLA composite film.The water vapor permeability coefficient of the HA/10%PBAT/PLA composite films increased linearly,and the water vapor permeability coefficient increased by about 1 times compared with the HA/PLA composite films.The addition of PBAT has great influence on the cold crystallization temperature of the composite films with the cold crystallization temperature decreasing by 15 degrees Celsius,and the crystallization peak was also narrow down.The method of combining melt blending with blending dispersion was adopted to prepare the HA/10%PBAT/PLA composite films.This method made the interface compatibility between PLA and PBAT improved,and the tensile strength of the composite films increased by about 40%.There is no effect on the melting point,the glass transition temperature and the cold crystallization of the composite films.And the oxygen permeability coefficient and the water vapor permeability coefficient of the composite films were all decreased by about 5%-10%.The polylactic acid,nano hydroxyapatite and PBAT are all belong to the biological materials,it is consistent with the development trend of the low carbon,green environmental protection of the packaging materials.Through the study of microstructure,mechanical properties,thermal properties,crystallization,water vapor permeability and oxygen permeability of the composite films,it also provides a theoretical basis for the application of the composite films on the packaging materials.