Reactive Compatibilization Of PVDF Blends Based On The Carboxyl-terminated PMMA Oligomer

Polyvinylidene fluoride(PVDF)has excellent physical and chemical properties and excellent piezoelectric and dielectric properties,so it is widely used in petrochemical,electronic and filtration separation and other fields.However,PVDF suffers several drawbacks such as high costs,bad adhesion ability with other materials,and high density.Blending with other polymers is the most useful way to modify PVDF.Unfortunately,PVDF shows poor compatibility with most general plastics and engineering plastics because of the special molecular structure of PVDF,.Therefore,the compatibilization of PVDF with other polymers attracts the most attentions.In this work,we proposed a novel reactive compatibilization strategy for PVDF blends based on the good compatibility of PMMA and PVDF,by using carboxyl-terminated PMMA oligomer(PMMA–COOH).The main contents of the paper are as follows:(1)Synthesis and structure characterization of PMMA-COOH oligomer: First,using methyl methacrylate(PMMA)as monomer,4,4'-Azobis(4-cyanovaleric acid)(ACVA)as initiator,thioglycolic acid(TGA)as a chain transfer agent,through radical telomerization reaction to synthesize PMMA-COOH oligomer,and by adjusting the feed ratio,preparing the controllable molecular weight distribution,molecular weight is 2000-8000 PMMA-COOH oligomer,and the molecular weight and structure of PMMA-COOH oligomer was characterized by GPC,FT-IR,1H,NMR.(2)The graft polymer(ethylene-glycidyl methacrylate copolymer)-g-polymethyl methacrylate(EGMA-g-PMMA)compatilize poly(vinylidene fluoride)/low-density polyethylene(PVDF/LDPE)blends: In this paper,we use the PMMA-COOH oligomer that synthesis of the upper section react with EGMA that a linear polymer with epoxide group and form EGMA-g-PMMA in situ in the PVDF and LDPE interface.EGMA-g-PMMA can effectively improve the compatibility between PVDF and LDPE,reduce the interfacial tension between the blend components,enhance the bond between the interfaces,and greatly improve the mechanical properties of PVDF/LDPE blends.The structure of EGMA-g-PMMA also had a great influence on the compatiblization effect.The compatiblization effect increases first and decreases with the length of side chain of grafted polymer and increases with the grafted density increasing.(3)Double graft polymer poly(l-lactic acid)-g-poly(styrene-co-glycidyl methacrylate)-poly(methyl methacrylate)(PLLA-g-SG-g-PMMA)compatilize poly(vinylidene fluoride)/poly(l-lactic acid)(PVDF/PLLA)blends : when PVDF/PLLA blends in melt,poly(styrene-co-glycidyl methacrylate)(SG)and PMMA-COOH add into the blends.The carboxyl activity on PMMA-COOH was higher than that of the carboxyl group on PLLA.Therefore,the carboxyl group on PMMA-COOH first reacts with the epoxy group on SG to form a single graft polymer SG-g-PMMA.Subsequently,the carboxyl group on PLLA reacts with the epoxy group on SG to form a double graft polymer PLLA-g-SG-g-PMMA.The PMMA side chain of PLLA-g-SG-g-PMMA has a good entangling effect with PVDF,and the PLLA can interact with the unreactive PLLA.Therefore,PLLA-g-SG-g-PMMA can be stable in the interface of blending components and compatiblize high efficiency of PLLA/PVDF blends.By changing the molecular weight of PMMA-COOH and adjusting the mol ratio of SG and PMMA-COOH can effectively control the double graft polymer PMMA side chain number and length.Compatible effect increases with the increase of the number of side chain and the side chain length within a certain range.