Synthesis Of Reactive Titanium Dioxide Nanoparticles And The Compatibilization Effect On PLLA/PBSU Blends

Recently,with people's attention to environmental and resource issues,fully biodegradable polymers with excellent performance have aroused great interest in academia and industry.Polylactic acid(PLLA)is a fully biodegradable polymer that has been used in many fields,but it also has the disadvantages of brittleness,slow crystallization rate and lower heat resistance.Polybutylene succinate(PBSU)is also an important biodegradable polymer with excellent flexibility.The blending of PLLA and PBSU is expected to achieve complementarity of performance.However,PLLA and PBSU are thermodynamically incompatible blends,and compatibilizers are need to improve their compatibility.Nano-titanium dioxide(TiO₂)has antibacterial,photocatalytic,self-cleaning properties,and has made rapid progress in the fields of food packaging and catalytic degradation of plastics.This paper intends to use TiO₂ as the compatibilizer of PLLA/PBSU blends to study the structures and properties of TiO₂compatibilized blends and explore the degradation behaviors of them.Details are as follows:(1)Synthesis and surface modification of titanium dioxide spherical particles and nanorods:The hydrothermal method was used to synthesize titanium dioxide spherical particles and nanorods by adjusting the p H of the solution.In the acidic solution,zero-dimensional titanium dioxide spherical particles were prepared;while the solution was alkaline,titanium dioxide nanorods were prepared.The silane coupling agent KH560was used to modify the surface of the two kinds of nanoparticles to prepare titanium dioxide spherical particles and nanorods with epoxy groups on the surface,which were used in the compatibilization of PLLA/PBSU.(2)The influence of titanium dioxide spherical particles on the compatibilization effect of PLLA/PBSU blend system:The PLLA/PBSU/titanium dioxide spherical particle ternary composites were prepared by melt blending using titanium dioxide spherical particles with epoxy functional groups on the surface.The influence of structure and formula of spherical particles on the morphology and performance of the PLLA/PBSU blend were systematically studied:the unmodified titanium dioxide spherical particles had a wetting coefficient of 0.69 in the PLLA/PBSU blend,so the unmodified titanium dioxide spherical particles were located at the interface of PBSU and PLLA.However,because the unmodified titanium dioxide spherical particles had no molecularly entanglement nor strong interaction with PLLA and PBSU,the titanium dioxide spherical particles at the interface obviously reduced the mechanical properties of the blend.After surface modification,titanium dioxide nanoparticles could be grafted with a large number of PLLA and PBSU macromolecular chains through the ring-opening reaction with the terminal carboxyl groups of PLLA and PBSU under the high temperature and strong shear,thus effectively entangled with the polymers at the two-phase interface.As a consequence,the interfacial adhesion was improved,the size of the dispersed phase was significantly reduced,thereby improving the strength and toughness of the blend.(3)The influence of titanium dioxide nanorods on the compatibilization effect of PLLA/PBSU blend system: the influence of titanium dioxide nanorods with different surface properties on the structure and properties of PLLA/PBSU blends were studied:during the melt blending,the titanium dioxide nanorods prepared under alkaline conditions have a strong interaction with PBSU,and the blend was mainly located at PBSU phase,which caused the size of the dispersed PBSU phase to become larger and the mechanical performance of the blends to deteriorate.On the contrary,the epoxy-modified titanium dioxide nanorods could react with the terminal carboxyl groups of PLLA and PBSU under the high temperature and strong shear,so that the massive PLLA and PBSU macromolecular chains were grafted on the surface of the nanorods and migrated to the two-phase interface,thus the interfacial adhesion was improved and the size of the dispersed phase is reduced.By adjusting the content of epoxy-modified titanium dioxide nanorods in blend,the strength and toughness of the blend were significantly improved.(4)Application exploration of PLLA/PBSU/titanium dioxide spherical particles film:TiO₂ processes excellent hydrophilicity,antibacterial and ultraviolet catalysis properties,which provides the possibility to prepare antibacterial and biodegradable films with controllable degradation.The degradation behavior of titanium dioxide spherical particles compatibilized PLLA/PBSU film was studied preliminarily.It was found that titanium dioxide spherical particles could effectively retain the humidity and suppress the reproduction of microorganisms in the packaging.The photocatalysis of titanium dioxide spherical particles were capable of inducing the degradation of the film,which provided a novel methodology for preparing the controllable degradation polymer packaging materials.