Structure And Properties Of Polyvinylchloride And Polyvinylidene Fluoride Composites

Polyvinylidene fluoride (PVDF) presents good stability to rigorous temperatures, mechanical strength, chemistry stability, and ageing resistance, which can be used as the solar cell back. However, PVDF has the relatively high melt strength, and therefore it is difficult to blow molding. The cost, processibility, and peel strength limit the application of PVDF in some fields. Polymethyl methacrylate (PMMA) has the strong interfacial adhesion and mechanical properties, which is used to improve the properties of PVDF. The processing conditions, morphologies, and properties of PVDF/PMMA blends prepared by melting compounding were investigated. TiO2particles were added into PVDF/PMMA blends to improve the mechanical properties. PVDF and acrylonitrile-styrene-acrylate (ASA) were introduced to improve the anti-ultraviolet irradiation of PVC. The mechanical and anti-ultraviolet properties of PVC/PVDF/PMMA and PVC/ASA blends were analyzed.The phase separation behavior appeared in PVDF/PMMA blends after short time melt blending (first processing). Phase morphology was related to the shear rate, processing temperature, and PMMA content. PVDF/PMMA blends were the homogeneous structures after long time melt blending (second processing). The chain entanglements densities of different molecules were greater than the same ones, which were good for the compatibility between PVDF and PMMA. There was only one relaxation peak in the stress relaxation spectrum, and no relaxation platform appeared in the long time region. PVDF/PMMA blends had the synergy effect during the molecular chain relaxation process. The solid PVDF/PMMA blends had three kinds of relaxation behaviors:aa and ac relaxation associated with segmental motions in the amorphous phase and the amorphous portions within the crystalline phase of PVDF, respectively, and am relaxation related to the PVDF/PMMA phase. PMMA facilitated the relaxation process of PVDF. The crystallinity of PVDF reduced gradually with the increasing PMMA content, however, the crystal type of which was not change. PMMA improved the hydrophilicity, processing conditions, and adhesion capability of the blends. The thermal decomposition temperatures of PVDF/PMMA blends reduced gradually with increasing PMMA content, however, the decomposition processes of PVDF and PMMA were independent. The microstructures of PVDF/PMMA blends determine the comprehensive performance. The homogeneous blends had the good tensile properties and anti-ultraviolet aging performance.Core-shell structured TiO2-g-PMMA nanoparticles prepared via seeded emulsion polymerization. TiO2-g-PMMA particles were dispersed evenly in PVDF/PMMA blends, which reduced the reunion phenomenon of TiO2nanoparticles. TiO2-g-PMMA particles did not affect the glass transition temperature of polymer matrix, but reducing the PVDF crystallinity. TiO2-g-PMMA was coated with a layer of PMMA, which reduced the interfacial polarization effect between TiO2particles and polymer matrix. TiO2-g-PMMA composites had a good thermal stability, the structures of which did not change under190℃with the increase of heat treatment time. Due to the good dispersion of TiO2-PMMA, the enhancement effect was greater than unmodified TiO2.PVDF was introduced to improve the anti-ultraviolet aging ability of PVC. However, the compatibility between PVC and PVDF was poor, which decreased the tensile properties of PVC/PVDF blends. PMMA improved the compatibility of PVC/PVDF blends, and enhanced the tensile properties and impact resistance. PVC/PVDF/PMMA blends had the strong anti-ultraviolet ability. The blends contain small amount of PMMA could keep good tensile strength, elastic modulus, and elongation at break after long time UV irradiation. However, the tensile properties and anti-ultraviolet performance of blends with high PMMA content decreased gradually with increasing PMMA.There was a good compatibility between PVC and ASA molecular chains. The synergistic toughening effect appeared in PVC/ASA blends due to the interaction between molecular chains. The elongation at break and toughness of PVC/ASA blends increased with the increasing ASA content. ASA improved the static thermal decomposition time, thermal decomposition temperature, and vicat softening temperature of PVC. ASA had the ultraviolet absorption effect, which hindered the oxidation degradation of PVC. PVC/ASA blends had the strong anti-ultraviolet aging ability with increasing ASA content. After a long time ultraviolet aging, PVC/ASA blends could maintain toughness higher than rigid PVC.