Preparation And Characterization Of Vinyl Chloride/2-ethyl Hexyl Acrylate Copolymers

Mixing of poly(vinyl chloride)(PVC)with plasticizer with low molecular weight is a commercial method to obtain flexible PVC materials.However,plasticizer is easy to migrate from the product,resulting the hardening of product and the environmental pollution.Adopting of acrylate monomer with long alkyl to copolymerize with vinyl chloride(VC)is an effective way to reduce the usage of plasticizer by the internal plasticization function of acrylate monomers,and to improve the compatibility of plasticizer with modified PVC and the processability of modified PVC.Thus, copolymerization of VC with acrylate has become a useful way to modify PVC.In the present thesis,2-ethyl hexyl acrylate(EHA)was used to copolymerize with VC to synthesis internal plasticized VC-EHA random copolymers and PEHA-g-VC copolymers with high impact strength.The influence of copolymerization method, adding policy and amount of EHA on the particle structure,processing property and mechanical performances were investigated.The results would provide the reference for further industrial production of EHA modified PVC resins.In order to obtain VC/EHA copolymer with uniform chemical composition,the higher activity copolymerization monomer-EHA,was continuously added during the suspension polymerization of VC.The influence of EHA content on copolymerization kinetics was studied.The results showed that the copolymerization rate was slightly reduced and the pressure drop of copolymerization system was delayed as the content of added EHA increased.The particle properties of VC/EHA copolymer resin were also studied.The results showed that the porosity and plasticizer absorption(CPA) were rapidly reduced with the increase of EHA content.SEM micrographs of VC-EHA copolymer particle showed that the internal pore of resin particles were gradually blocked as more EHA added in copolymerization.In order to improve the particle structure of VC/EHA copolymer resins,emulsified EHA was continuously added to reactor when VC conversion reached 38.86%.The results showed that the copolymer resin prepared by adding emulsified EHA had a lower primary particle aggregation degree than that of resin prepared by adding pure EHA.When the EHA content was about 5.74%,CPA of resin prepared by adding emulsified EHA was reached 14g/100g resin,while CPA of resin prepared by adding pure EHA was 8g/100g resin.Plasticized VC-EHA copolymer was prepared by adding dioctyl phthalate(DOP), The processing and mechanical properties of plasticized and unplasticized VC-EHA random copolymers were investigated.The results showed that the processing equilibrium torque and gelation time were reduced with the increase of EHA content. The tensile strength and hardness of unplasticized and plasticized VC-EHA copolymer were decreased as the content of EHA increased.The impact strength of unplasticized VC-EHA was increased.After the preparation of PEHA latex,PEHA-g-VC and PEHA-g-VC/EHA copolymers were prepared by VC suspension grafting copolymerization.The results showed that the stability of VC suspension polymerization was decreased as PEHA latex added in the suspension system.By increasing the usage of suspending agents to be 0.3%,the suspension polymerization stability was improved and modified PVC resin with acceptable particle morphology was obtained.With the increase of PEHA content,the graft ratio and graft efficiency of VC were increased.The processing and mechanical properties of copolymer resins prepared by the different methods were compared.The results showed that PEHA-g-VC/EHA copolymer were actually consisted PEHA-g-VC graft copolymer,VC-EHA random copolymer,PVC and PEHA homopolymers.PEHA-g-VC/EHA copolymer exhibited the highest impact strength at the same EHA content.