Design Of Impact Components For Suspension Polymerization Of Vinyl Chloride And Preparation Of Impact Resistant PVC

Polyvinyl chloride(PVC)is widely used in building materials,automobile industry and other fields because of its excellent flame retardance,chemical corrosion resistance and much better mechanical properties.However,its further application in building materials is greatly restricted due to its poor impact strength.For the time being,the best way to improve the impact resistance and processability of rigid PVC is to mix the acrylate copolymer resin(ACR)and PVC physically.Recently,the novel method to prepare high impact PVC in the presense of ACR latex by in-situ suspension graft polymerization has become a hot topic in the field of PVC toughening modification.Compared with toughing modification of PVC by physical blending,the impact modifier has a higher toughening efficiency in later method,which is caused by the better dispersion of the modifier in PVC resin matrix and the better compatibility with PVC resin matrix.In this paper,two kinds of acrylate latices(ACR)of narrow size distribution with homogeneous and crosslinking structure and transition layer structure were prepared through seed emulsion polymerization with butyl acrylate(BA)and methyl methacrylate(MMA)as monomers,1,4-butanediol dimethacrylate(BGDMA)as crosslinker,allyloxmethyl nonylphenol ether sulfates(SE-10N)as reactive emulsifier.Then PVC with high impact strength was prepared by in-situ suspension graft copolymerization with vinyl chloride in presence of ACR latex.The most of research works and conclusions in this paper were shown as follows:Firstly,the homogeneous ACR latices with crosslinking structure(non core shell structure)were prepared successfully by adding seed latex based polystyrene.The effects of the temperature of emulsion polymerization,the proportion of seed latex and the proportion of emulsifier on the properties of ACR latex were investigated in detail.The results showed that:the ACR particle size could be controlled accurately by changing the proportion of seed latex in the system,ACR latex with the particle size of about 200 nm could be obtained and were much stable when the proportion of seed latex was 0.42wt%and the ratio of SE-10N was 1.00wt%.Sencondly,in the system of PVC modified by homogeneous and crosslinking ACR,effect of ACR latex kinds,which were prepared at different temperatures of emulsion polymerization,on the properties of modified PVC composite resin,and effect of the feeding sequence of ACR latex on the suspension polymerization stability,properties of modified PVC composite resin were investigated.The results showed that:when the ACR obtained at 70± 1 ? was used,the modified PVC composite resin had the best impact resistance.When the amount of ACR latex is 6.0 wt%,the notched impact strength of PVC modified by ACR in-situ suspension grafting was 7.4 times that of unmodified SG-5 PVC.The PVC modified by ACR70? had the best plasticizing properties when the ACR obtained at different reaction temperatures were used to prepare in-situ suspension grafting PVC,whose melting time was much shorter than the unmodified general rigid SG-5 PVC.The ACR prepared at different temperatures had no significant effect on the initial degradation temperature of modified PVC composite resin,all of the vicat softening point(VST)of modified PVC decreased slightly,whose thermal deformation temperature was equal to SG-5 PVC.Besides,if ACR latex was added when vinyl chloride monomer had been dispersed well in situ suspension polymerization,the particle shape and impact strength of modified PVC composite resin were better than that of ACR latex added before.The most important thing is that there is no polymers stuck on stirring peddle and wall of reactor.Finally,the ACR latices with transition layer structure and with different hydrophilic or hydrophobic abilities were synthesized by seed emulsion polymerization,and the structure of latex particle was characterized by DLS and TEM.The effect of hydrophilic and hydrophobic properties of ACR on the properties of modified PVC,and effect of the ratio of dispersant on the morphology of PVC particles modified by in-situ suspension grafting were studied.The results showed that:When the transition layer type ACR in which the MMA ratio of outer layer was 10%was used,the modified PVC obtained had the best impact resistance.The ratio of MMA in the outer layer of the transition layer type ACR had little effect on the thermal deformation temperature of in-situ suspension grafting PVC resin.But the composite resin modified by homogeneous crosslinking ACR has better comprehensive performance.The initial degradation temperature of two kinds of modified PVC were almost unchanged,which were consistent with that of SG-5 PVC resin.However,the maximum heat loss rate of the modified PVC were lower.The particle shape of the modified PVC was better when the low molecular weight polyvinyl alcohol dispersant was used in suspension polymerization.