Preparation And Properties Of Polymer/Inorganic Nanoparticle Composites By Solution Casting

Polymeric/inorganic nanoparticle composites,as a kind of materials containing both polymer and inorganic nanoparticles,have attracted much attention and become a hot spot in the field of materials.It overcomes the problems of inorganic materials that are difficult to process and allows the polymer to enhance some aspects of special properties?such as mechanical,electrical and optical properties?.The solution casting method is a common method for the preparation of polymer/inorganic nanoparticle composites.Compared with other methods,the preparation process is simpler and the operation is more convenient.Therefore,poly?vinylidene fluoride??PVDF?/barium titanate?BaTiO3?nanocomposites were prepared by solution casting method,and their crystallization behavior and thermoelectric properties were studied.Meanwhile,in order to verify whether the effect of nanoparticles on the crystal behavior of the polymer in other polymer nanocomposites is like PVDF/BaTiO3 nanocomposites,polylactic acid?PLA?/iron oxide?Fe₃O₄?nanocomposite films were prepared.The investigations in this work are primarily the following:?1?The crystallization behavior of pure PVDF.Pure PVDF treated with the isothermal crystallization process only exhibited ?-phase crystal.The ring-banded spherulites appeared when the isothermal crystallization temperature is above 165 °C and the ring band space of PVDF increased with an increase of the temperature.According to the experimental results,equilibrium melting point of PVDF is around 197 °C.Melting point of PVDF crystallized at 155 and 160 °C are 177.5 and 179 °C,respectively.The effect of melting temperature above equilibrium melting point on the isothermal crystallization behavior of PVDF is very small,the number and size of the spherulites remain the same.When the melting temperature is below the equilibrium melting point,the number of spherulites increased with a decrease of the melting temperature,but its size increased;and with the number of times of the repeated circulating melt-crystallization increased,the number of PVDF spherulites became more,the size became smaller.?2?Properties and crystallization behavior of PVDF/BaTiO3 nanocomposites.When PVDF/BaTiO3 composites were precipitated from the solution,the introduction of BaTiO3 particles can promote the formation of ?-phase,while the samples treated with isothermal crystallization process only exhibited ?-phase crystal.BaTiO3 could promote the crystallization of PVDF in the course of nonisothermal crystallization.While in the course of isothermal crystallization,BaTiO3 can promote the nucleation of PVDF when 1.0 wt% BaTi O3 particles are added into PVDF,beyond this concentration,nucleation ability of PVDF promoted by BaTi O3 vanished.BaTiO3 can improve the electrical conductivity and Seebeck coefficient of PVDF.BaTiO3 can improve the thermal stability of PVDF.?3?Crystallization behavior of PLA/Fe₃O₄ nanocomposites.According to the experimental results,the introduction of Fe₃O₄ particles can hinder the crystallization of PLA when PLA/Fe₃O₄ composites were precipitated from the solution.In the course of nonisothermal crystallization and isothermal crystallization,Fe₃O₄ can promote the heterogeneous nucleation of PLA when 1.5 wt% of Fe₃O₄ particles are added into PLA,beyond this concentration,heterogeneous nucleation ability of PLA promoted by Fe₃O₄ are reducing.Fe₃O₄ can weaken the thermal stability of PLA.