Reactive Monomer Grafted Polyvinylidene Fluoride: Preparation, Structure, Properties And Applications

Polyvinylidene fluoride(PVDF)is a typical semi-crystalline fluoropolymers material with good chemical resistance,irradiation resistance,mechanical properties,processability,special dielectric and piezoelectric properties,which is widely used in many fields such as water treatment membrane,electronic appliance,fluorocarbon coating and so on.With the changement of market demand,higher requirements are put forward for the performance of PVDF.The functional modification of PVDF can be achieved by physical blending and chemical grafting.However,PVDF has poor compatibility and adhesion with a lot of other polymers,thus functional graft modification of PVDF by reactive monomer is of great significance.The chemical grafting method can immobilize the reactive monomer on PVDF molecular chains via chemical bonds,leading to new permanent functionalization PVDF materials.Radiation induced grafting polymerization(RIGP)method is one of the effective means of polymer chemical grafting.it exhibits several advantages,such as simple operation,low reaction temperature,wide universality and so on.On the other hand,reactive monomer grafted polymers can also be used as compatibilities and adhesives to improve the compatibility and interfacial adhesion of polymer/polymer or polymer/inorganic fillers blends.In this work,two reactive monomers with different reactivity:maleic anhydride(MAH)and acrylic acid(AA)were selected to functionalize PVDF.The compatibility of two reactive monomers(MAH or AA)with PVDF was investigated systematically;The MAH and AA monomer were further grafted onto PVDF chains(PA6-g-MAH and PVDF-g-PAA)via RIGP method respectively,the effects of graft modification of reactive monomer on the structure and properties of PVDF were studied in detail.Finally,PA6-g-MAH and PVDF-g-PAA were explored as the compatibilizer for PVDF/PA6 and PVDF/PLLA blends respectively.The detailed research contents were listed as follows:(1)Study on the structure and properties of PVDF/MAH blends.PVDF/MAH blends with different MAH content were prepared by melting blending The SEM and DSC results indicated that PVDF has good compatibility with MAH monomer.The FTIR spectra indicated that the existence of hydrogen bond interaction between CH2 of PVDF and C=O of MAH monomer.This interaction exhibits great influence on the crystallization behavior,thermal stability,rheological properties and mechanical properties of PVDF/MAH blends(2)The preparation of PVDF-g-MAH and investigations on its compatibilization for PVDF/PA6 blends.MAH grafted PVDF(PVDF-g-MAH)was successfully prepared by radiation grafting at room temperature.The degree of grafting of MAH increased gradually with the increase of MAH content and absorbed dose.Higher degree of grafting can be achieved in the vacuum conditions than in the air atmosphere at the same radiation dose.The graft modification of PVDF by MAH had no effect on its microstructure and crystal form,but PVDF-g-MAH showed completely different thermal behavior,rheological behavior and mechanical properties from PVDF.In addition,PVDF-g-MAH has a good compatibilization effect on PVDF/PA6 incompatible blends.(3)The preparation of AA grafted PVDF and investigations on its properties.PVDF/AA blends with different AA additives were prepared by melting blending The results indicated that AA has good compatibility with PVDF,and AA can be evenly dispersed in PVDF matrix.PVDF-g-PAA was prapered from PVDF/AA binary blend by gamma-ray irradiation.The degree of grafting of PVDF-g-PAA was precisely regulated by the content of AA monomer,and the effects of different AA degree of grafting on the crystallization,thermal,rheological,hydrophilic and mechanical properties of PVDF were investigated systematically(4)The investigations of PVDF-g-PAA on the compatibilization effect of PVDF/PLLA blends.To investigte the influence of PVDF-g-PAA on the compatibility of PVDF/PLLA blends,the results indicated that both PVDF-g-PAA and PLLA could react with high epoxy content of poly(styrene-co-poly methyl methacrylate)(SG).The reactive compatibilizer with double comb structure is formed in the melting blending process,which can be stable in the two-phase interface of PVDF/PLLA blends.The micromorphology of PVDF/PLLA blends changed from sea/island structure to bicontinent structure.The reactivity of PLLA and SG was significantly higher than that of PVDF-g-PAA,so PVDF-g-PAA/SG premixed samples had the best compatibility effect and the smallest phase domain size.The compatibility effect of the blends increased gradually with the increasing content of SG,and reached the best when SG content was 10 wt%.When the content of SG is 10 wt%,even the degeree of grafting of PVDF-g-PAA is 0.5%can significantly improve the compatibility between PVDF and PLLA.