| As one of the most commonly used plastics in nearly all areas of industries and daily lives,polyvinyl chloride(PVC)is known to have low impact resistance,which has imposed large obstacles to its applications.Therefore to improve the impact resistance of PVC has been an important topic since long in the related industries and for research scientists.Facing to this issue,in this paper,acrylic ester copolymer latexes(ACR)with core-shell structure are synthesized by emulsion polymerization,using butyl acrylate(BA)as the main core monomer and methyl methacrylate(MMA)as the main shell monomer,combined with different crosslinking agents and emulsifiers.The effects of monomer ratio,different emulsifier compounding,emulsifier dosage,different crosslinking agent,their amounts and addition time in the polymerization are discussed,and selected ACR powders are used to toughen PVC in order to evaluate the performance of PVC toughened by ACR different types of ACR core-shell latex are synthesized,as summarized here bwlow:(1)Core-shell ACR latexes can be prepared by step-feeding of the monomers or its preemulsion to the seed latex prepared in advance;(2)The Core-shell latexes can be also prepared by semi-continuous process,i.e.the shell monomers or their pre-emulsion are added continuously to the seed latex prepared in advance;(3)A polymer transition layer can be formed between the core shell layers by adding other monomers or their preemulsion,either by step-feeding or continuous feeding.In all these processes,peroxide sulfate salts alone or isobutyl hydrogen peroxide(TBHP)redox initiator can be used as initiator in the polymerization.The particle size and size distribution of the latex particles are measured using a dynamic light scattering particle size analyzer(DLS),and a transmission electron microscope(TEM)for selected samples;the morphology,structure,and glass transition temperature of ACR were characterized by TEM and differential thermal scanning(DSC).The results show that the synthesized ACR particles are a spherical with core shell structure,and two glass transition temperatures are observed,representing that of poly(acrylate butyl)(PBA)and polymethyl methacrylate(PMMA),respectively.The tensile strength and anti-impact resistance of commercial PVC are tested and compared with those toughened after blending PVC with different ACR powcers,which were obtained by spray drying or direct flocculation followed by drying in an oven at 80 oC.The results show that core shell and ACR powder have good dispersibility in PVC matrix,and the performance of the core-shell ACR toughened PVC is comparable to that toughened by market product.The second part of this dissertation is the synthesis and characterization of an associative thickener.To protect the environment,replacement of classical oil-based paints and coatings by water-based has been a focus for the related induatries and scientists.It is well known that thickener is an important component in water-based coatings.Herein an associative thickener was synthesized by emulsion polymerization,based on methacrylic acid(MAA),ethyl acrylate(EA)as the main monomers and docosalkyl polyoxyethylene ether methacrylate(BEM)as the functional monomer in the presence of composite emulsifier.The particle size of the thickener latex was measured by DLS.The results showed that associative thickener with high performance was prepared using 1.8% BEM,35% MAA,and an appropriate amount of crosslinking agent DAP.. |
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