Preparation And Molecular Dynamics Simulation Of Inorganic Whisker/PBS Composites

Biodegradable polymer materials are widely used in packaging materials,agricultural film and biomedical materials because of their degradability,safety and environmental friendliness.Among them,poly(butylene succinate)(PBS)has become the focus of biodegradable research for its good mechanical properties,high thermal deformation temperature and easy processing performance.However,compared with the traditional polymer materials,the mechanical properties and thermal stability of the degradable materials still need to be improved,and the modification of PBS has become one of the research hotspots.Magnesium hydroxide sulfate hydrate whisker(MHSH)is widely used in the reinforcement and toughening of polymer materials for its high strength,high modulus and flame retardancy.However,the dispersion of inorganic whiskers and the compatibility with polymer matrix become the key factors affecting the properties of composites.In this study,MHSH was modified by KH590and vinyl POSS,and a kind of magnesium salt whisker/POSS hybrid material(MHSH-POSS)was prepared to enhance the interfacial interaction between MHSH and polymer matrix.A series of whisker/PBS composites were prepared by melt blending method.The effect of whisker and hybrid materials on the properties of PBS was studied by experiment and molecular dynamics(MD)simulation.And the synergistic mechanism of whisker and hybrid materials on PBS was discussed from the microscopic point of view.MHSH whisker and MHSH-POSS hybrid material were used to enhance PBS.A series of magnesium salt/PBS composites were prepared by melt blending method.The effects of whisker content and whisker modification on the properties of PBS were investigated.The results showed that when the whisker content was 5%,the mechanical properties of PBS composites were the best.The reinforcement effect of MHSH-POSS on PBS was better than that of MHSH.The tensile strength and bending strength of the PBS composites reached 60.9 MPa and 42.0 MPa respectively,which were 113.7%and 131.3%higher than pure PBS.DSC test showed that the addition of whisker reduced the crystallinity of PBS.The crystallinity of PBS/MHSH-POSS was56.4%,which was significantly lower than that of pure PBS(67.0%).The degradation test showed that the addition of whisker significantly improved the degradation rate of PBS,which was mainly due to the decrease of crystallinity and the increase of amorphous region of PBS composite,which was conducive to the entry of degradation enzyme into the loose amorphous region,and promote the degradation of PBS.The non-isothermal kinetics of PBS and its composites was studied by Jeziony equation,Mo Zhishen equation and Kissinger equation.It was found that with the addition of whisker,the crystallization rate constant Z_aincreased and the cooling rate function F(T)decreased,which indicated that the whisker could be used as a nucleating agent to accelerate the crystallization rate of PBS.However,the crystallization activation energy of PBS/MHSH-POSS composite was 8.446 k J/mol,which was 40.6%higher than that of pure PBS,indicating that the whisker could interacted with the molecular chains of PBS to limit the migration of molecular chains,thus reducing the crystallinity of PBS.Through POM observation,it was found that PBS and its composites grew in the form of spherulites.The addition of whisker increased the density of spherulites and reduced the size of PBS spherulites.XRD and TEM tests showed that the surface modification enhanced the interaction between whisker and PBS,resulting in the increase of lattice spacing of PBS composites,thus affecting the crystallization process of PBS.The binding energy(E_binding)of PBS composite was calculated by MD simulation,and the force between whisker and PBS was quantitatively studied.The results showed that the E_bindingbetween MHSH-POSS and PBS was 58173.51 kcal/mol,which was significantly higher than 50289.05 kcal/mol between unmodified MHSH and PBS,which indicated that whisker modification could significantly improve the interfacial interaction between the whisker and PBS.MSD analysis showed that the migration ability of PBS molecular chains on the surface of MHSH-POSS was the smallest,indicating that the surface modified POSS of MHSH-POSS hybrid materials would entangle with PBS molecular chains,which limited the movement of PBS molecular chains.The analysis of g(r)curve showed that hydrogen bond was formed between whisker and PBS to improve the interfacial interaction.By H-bond calculation,it was found that the number of hydrogen bonds between MHSH-POSS and PBS was more than that of MHSH,which was beneficial to improve the interfacial interaction between MHSH-POSS and PBS matrix,thus enhancing the interfacial compatibility.