相分离对聚偏氟乙烯/聚甲基丙烯酸甲酯共混物的力学与耐紫外老化性能的影响

采用熔融共混法制备聚偏氟乙烯/聚甲基丙烯酸甲酯( PVDF/PMMA)共混物,考察其力学性能、耐紫外老化性能、熔体动态流变、结晶与热分解行为.PMMA含量(wPMMA)为10 wt％时,共混物形成均相结构,力学与耐老化性能最好.wPMMA≥20 wt％时,PMMA形成球状聚集体,共混物力学性能与耐候性显著降低.PMMA的存在可提高PVDF的结晶度,降低熔融温度,但不改变PVDF晶体结构.

INFLUENCE OF PHASE SEPARATION ON MECHANICAL AND ANTI-UV AGING PROPERTIES OF POLYVINYLIDENE FLUORIDE/POLYMETHYL METHACRYLATE BLENDS

Tensile and anti-UV aging properties of polyvinylidene fluoride(PVDF)/polymethyl methacrylate(PMMA) blends prepared by melting compounding were investigated.The results indicated that PVDF had a good miscibility with little PMMA(10 wt%) so that the blend was homogeneous and had the best tensile properties and weatherability.On the other hand,significant phase separation occurred in the blends containing more than 20 wt% PMMA,which led to marked reductions in tensile properties and weatherability.PMMA played a role of diluent that accelerated molecular movements and reduced relaxation time of the blend.Because of the habit of PVDF tending to self-entangle in the blends,improving molecular motion at high temperatures could lead to the occurrence of phase separation.The binodal temperature of blends was got by the small amplitude temperature scanning experiment,which decreased with increasing PMMA content.The results did not follow some previous researches on solution casting blends.Crystallinity of PVDF increased and melting point decreased with increasing PMMA content.However,XRD results indicated that PMMA did not change the crystal structure of PVDF.Furthermore,TGA tests revealed that there was no synergistic effect between thermal decompositions of PMMA and PVDF in the blends.