| Acrylic core-shell tougheners(ACR)are often used to modify polyvinyl chloride(PVC)to fill its deficiencies,and the prepared blends usually have some excellent properties that other materials do not have,such as good weathering resistance,wide processing window,thermal stability,etc.However,with the increasing use of PVC materials,the demand for ACR is also gradually increasing,therefore,enhancing the toughening efficiency of ACR for PVC has become a hot topic of research.The main research work of this thesis is as follows:(1)In the first part of the work,the effects of crosslinker content and type on the kinetics of polyacrylate copolymer emulsions and the double bond residues inside the emulsions were explored to provide a basis for the subsequent efficient preparation of ACR.The results showed that the cross-linking agent content had a large effect on the kinetics of polyacrylate copolymer emulsions.The residual double bond content of acrylate seed emulsions synthesized with non-equally active double bond cross-linking agents was higher than that of acrylate seed emulsions synthesized with equally active double bond cross-linking agents.The isoactive double bond crosslinker was more favorable to the internal crosslinking of the latex.(2)In the second part of the work,polyacrylate polymers synthesized with different crosslinker types were used as core and grafted with methyl methacrylate(PMMA)to prepare ACR modifiers.The effect of the crosslinker type on the performance of the final synthesized ACR was investigated,and then the PVC was toughened and modified to verify the toughening efficiency of the ACR.The mechanical test analysis showed that the PVC/ACR blends reached the brittleness-ductility transition point when the ACR content added in the matrix was 8 phr.The toughening efficiency of ACR synthesized with the participation of bifunctional crosslinkers was better than that of ACR synthesized with the participation of trifunctional crosslinkers,and the toughening efficiency of ACR synthesized with the participation of crosslinkers with unequal active double bonds was higher than that of ACR synthesized with the participation of crosslinkers with equal active double bonds.in which,the acrylate crosslinking latex grafted with BA and EHA co-polymerized with dicyclopentenyl acrylate(DCPA)as the crosslinker The DCPA-ACR prepared by methyl methacrylate(MMA)was well compatible with the substrate,and the highest notch impact strength was achieved when 8 phr DCPA-ACR was added to the substrate to toughen PVC,and the notch impact strength was up to 1682 J/m,which was almost 62 times that of pure PVC,while the PVC/ACR blend prepared by conventional ACR was 45 times that of pure PVC.The experimental results showed that the shear yield of the blend material increased its toughness.(3)In the third part of work,BA,EHA,and DCPA as raw materials,polyacrylate seed latex with uniform particle size and good dispersion was prepared by batch feeding method with different crosslinking layer thicknesses.Acrylate impact modifier(ACR)was prepared using polyacrylate seed latex as the core and MMA as the shell.The effect of ACR properties of different crosslinked layer thicknesses on the mechanical properties of PVC matrix is discussed.The results show that appropriate crosslinked layer thickness directly affects the dispersion of ACR in the matrix.With the increase of ACR content,the toughness of the blend increased gradually.Among all the modifiers,ACR-1 has a brittleness transition point of 7 phr in the PVC blends,while the conventional ACR is 8 phr. |
