Preparation And Properties Of Pvdf/Pmma Films Modified By TiO₂Nano-Particles

Polyvinylidene fluorid (PVDF) has been extensively utilized as coating and films, because of excellent oxidationcorrosion, radiation, and resistance, high temperature, weatherability. outstanding piezoelectric, dielectric properties and thermoelectricity. However, the melt strength of PVDF is relatively high, which lends to difficultly preparing uniform films with smooth surfaces. The cost, processibility and peel strength limit the application of PVDF in some fields. Introduction of inorganic powders or other polymer in the polymer can extremely improve the processibility and other properties of PVDF.PVDF with excellent outdoor weatherability is expected to be applied as a new backsheet for solar cells instead of the conventional backsheetbased on polyvinyl fluoride (PVF). In our work. PVDF is melt blended with methyl methaciy late (PMMA) and TiO2nano-particles to produce uniform PVDF/PMMA and PVDF/PMMA/TiO2composite films. The thickness of composites is controlled between20to30μm. The weatherability, mechanical and adhesive properties of composite film are characterized.The SEM images reveal that PVDF and PMMA show excellent compatibility. The FTIR and XRD spectra indicate that the incorporation of PMMA decreases the crystallinity of PVDF, and induces PVDF to transform from α crystalline to β crystalline. Despite the thermal stability of PVDF displays a subtle decline after blended PMMA, the PVDF/PMMA composite film even containing30%PMMA still exhibits relatively the high thermal decomposition temperature of290℃. The viscosity of PVDF/PMMA composites decrease with the loading of PMMA increase, which enhance the fluidity of composite materials and promote the processability. The tensile strength and elongation at break of PVDF/PMMA decline with the content of PMMA increase. However, the PVDF/PMMA film containing40%PMMA still presents good mechanical properties, and the tensile strength and elongation at break of them can reach to37MPa and63%.On the base of previous experiment results, the PVDF/PMMA composites with content of30%PMMA is as matrix to prepared PVDF/PMMA/TiO2films. TiO2nano-particles were funtionalized by KH-570coupling agent to improve the dispersion of TiO2in PVDF/PMMA composites. After grafting modification, TiO2can be well dispersed in the PVDF/PMMA matrix. The thermal decomposition of PVDF/PMMA/TiO2films decreases with the introduction of TiO2. Maybe, TiO2plays the role of a catalyst to change the decomposition mode of PVDF/PMMA. Loading TiO2can increase the mechanical properties of PVDF/PMMA/TiO2films. and the excessive loading fillers reduce the propertiest due to the aggregation of TiO2nano-particles. Incorporation of TiO2extremely improves the UV resistance and weatherability of composite materials. After continuous aged480hr under simulated sunlight irradiation, the PVDF/PMMA/TiO2films retain good mechanical properties, indicating that TiO2absorb mostly UV to mitigate the matrix aging. PMMA and TiO2obviously strengthen the peel strength of PVDF. In comparison with4165N/m of pure PVDF, the peel strength of PVDF/PMMA/4wt%TiO2is up to4963N/m. Even if aged480hr. the value of the peel strength of PVDF/PMMA/4wt%TiO2is still as high as4720N/m.