Study On Crystal Morphology And Structure Of Polyvinylidene Fluoride And Ester-Containing Polymer Blend Film

Ultrathin films were prepared by blending polyvinylidene fluoride(PVDF)with two crystalline polyesters with different melting points,polybutylene adipate(PBA),polybutylene succinate(PBS),and amorphous polyethyl methacrylate(PEMA).PVDF single crystals,single crystal aggregates,dendrites and snowflakes were cultured by melt crystallization.The effects of film thickness,crystallization time,crystallization temperature and blending quality ratio on the crystallization behavior of ultrathin films were systematically investigated by optical microscope,atomic force microscope and transmission electron microscope.The main results are as follows:1.The α phase single crystals or single crystal aggregates of PVDF could be grown in the blends of PVDF and two kinds of crystalline polyesters.The single crystal aggregates have a layer of large single crystal substrate,and the long axis size reaches hundreds of microns.Many smaller rhombic single crystals grow above it,and the growth directions of the smaller rhombic single crystals are consistent with that of the large single crystal layer below.2.In PVDF/PBA blend films,rhombic single crystal aggregates can be formed.There are many small rhombic single crystal aggregates on the large rhomboid single crystal layer with the same growth direction,and the average thickness of single crystal layer is about 11～12 nm.In PVDF/PBS blend films,regular rhombic monolayer lamellae with a thickness of about 9 nm were grown.3.In the thick films(50～60 nm)of the two blends,the single crystal aggregates grew in bending.In PVDF/PBA system,with the extension of crystallization time and the increase of crystallization temperature,the single crystal aggregates show "C" shape and anti "S" shape.The thickness of single crystal layer is about 11～12 nm.In PVDF/PBS system,the low-temperature single crystal aggregates are mainly "X" shape and "C" shape.With the increase of crystallization temperature,the "X" shape develops more branches,and the average thickness of single crystal layer is about 9 nm.4.In PVDF/PEMA blend films,neither single crystals nor single crystal aggregates were cultured.Only two kinds of crystals with different morphology were observed,dendritic crystal and snowflake crystal.The size and nucleation density of the two crystals are greatly affected by crystallization temperature and blending mass ratio.It is preliminarily judged that the two crystals belong to α and γ phase PVDF,but further confirmation requires electron diffraction data.