Preparation Of PVDF/PMMA/TiO₂ Composite Materials And Its Anti-Aging Property

As a fluoride-plastic, Polyvinylidene fluoride (PVDF) presents good stability to rigorous temperatures, UV exposition, aggressive chemical environments, mechanical strength, and is widely used as protective materials such as coating and protective films. However, PVDF is expensive and hard to get smooth and homogenous film, and has poor interaction with other materials. So, in this work, it is blended with Poly(methyl methacrylate) (PMMA) and TiO2, PVDF/PMMA/TiO2 are prepared, and the structure and property of the films are investigated.In this paper, structure and property of PVDF/PMMA/TiO2 film from melt-blend were investigated. It was indicated that the addition of PMMA could greatly improve the microstructure of PVDF membrane by SEM. UV-vis results showed that the addition of TiO2 absorbed ultraviolet light effectively and reflected visible light greatly making up the shortage of PMMA. The reflection of visible light can improve the utility rate of luminous energy of solar cell. Through DSC, it was indicated that the addition of PMMA hindered the crystallization process of PVDF and made it to form a partly imperfect crystal. TiO2 played a role of heterogeneous nucleation effect, and obstructed regular accumulation of molecular chain of PVDF. As for mechanical properties, as increasing PMMA content, tensile strength and elongation at break of membranes dropped. With the addition of TiO2, the tensile strength of membranes increased, but the elongation at break reduced at the same time. The increase of TiO2 content reduced tensile strength and elongation at break of membranes. Sum up, the membranes also had very good mechanical properties.Rigorous temperatures of PVDF/PMMA/TiO2 membranes were studied. The results showed that TiO2 and PMMA content had little effect to UV exposition of the aging membranes. With the increase of aging time, the extent of absorption of UV-vis dropped for membranes, but membranes also had good stability to rigorous temperatures and UV exposition. TiO2 and PMMA content had little effect to thermal properties of the aging membranes. After along time aging, the crystal structure of membranes had not been destroyed:whereas, the mechanical properties of membranes reduced, and TiO2 and PMMA slowed down the speed of aging.The kinetics of isothermal and non-isothermal crystallization of PVDF/PMMA/TiO2 membranes was studied. The results showed that, for isothermal crystallization, the crystallization half time of PVDF increased with increasing crystallization temperature, the higher crystallization temperature was, and higher crystallization temperature is conducive to the improvement of crystallization. The values of Avrami exponent were evaluated around 3, indicating the heterogeneous nucleation followed by three-dimensional crystal growth. For non-isothermal crystallization, with the increasing of cooling rate, crystallization peak temperature reduced. crystallization peak get gentle. Ozawa equation and Mo method were successful in describing the non-isothermal crystallization process.