Preparation And Application Properties Of Acrylate Impact Modifier

Acrylate impact modifier (AIM) is a commercial impact modifier for poly(vinyl chloride) (PVC) with good performance, which can effectiviely improve the toughness and fusion properties of PVC, and AIM modified PVC exhibited good weather-resistance. The relationships between the structure of AIM and the preoperties of AIM modified PVC are still not well established. In this thesis, AIM with crosslinked poly(butyl acrylate) (PBA) as the core, poly(methyl methacrylate) (PMMA), PMMA/PVC or PVC as the shell, were synthesized by core-shell emulsion polymerization, and the influences of core size, composition of shell and core-shell mass ratio of AIM on the dispersion of AIM in PVC, impact strength and fusion behavior of AIM modified PVC were investigated.PBA latexes were synthesized through batch and semi-continuous emulsion polymerization processes, and the influences of polymerization process, emulsifier concentration and initiator type on the size of PBA latex particles were studied. It was found that the size of PBA latex particles was increased as the concentration of sodium dodecyl benzene sulfonate (CSDBS) emulsifier decreased in the batch emulsion polymerization of BA, but the mass fraction of coagulated PBA was increased as the CSDBS decreased. The size of PBA latex particles could be effectively adjusted by varying the amount of seed emulsion used in the semi-continuous emulsion polymerization, and PBA latex with the weigth average particle size of 90-250 were obtained. PBA/PMMA core-shell structure latex particles were synthesized through the seeded emulsion polymerization using PBA as the seeds, and the factors affecting the thickness of PMMA shell were studied. It was found that the thickness of shell was increased as PMMA/PBA mass ratio increased. The thickness determined from the size change and TEM micrographs was lower than the therotical value, indicating the insert of MMA into PBA phase and the formation of PBA/PMMA composite layer. The PBA/PMMA composite particles exhibited the clear core-shell structure evidenced by TME microgaphs of dyed PBA/PMMA latex particles. AIM was used to toughen PVC by the direct blending. It was found that AIM was well distributed in PVC matrix observed by TEM micrography. The notched izod impact strength of PVC/AIM blends was tested, and it was found that the particle size of PBA and the core-shell ratio of AIM were the main fators affecting the impact strength of modified PVC. The modified PVC had the highest notched izod impact strength when the diameter of PBA particles was about 220nm. AIM with high core-shell ratio was effectively in improving the notched izod impact strength of the modified PVC. When the core-shell ratio was about 75/25-80/20, the modified PVC both had high notched izod impact strength and good fusion properties. The performance of AIM can be improved by adding some grafting agent in the core synthesis. SEM micorgraphs showed that the broken surface of AIM modified PVC exhibited typical ductile fracture morphology. Furthermore, the fusion properties of PVC could be improved by adding a small amount of AIM, showing the shorter fusion time, and the increased minimum and maximum torque of PVC.New kinds of AIM with the structure of PBA/PVC and PBA/PMMA/PVC were synthesized by vinyl chloride emulsion in the presence of PBA latex and PBA/PMMA latex respectively. TEM micrographs clearly showed that AIM latex particles only coated with PVC exhibited two layers core-shell structure, and AIM latex particles coated by PMMA and PVC exhibited three layers core-shell structure.When there is no PMMA in the shell of AIM, the Tg of PBA significantly increased to about -3℃, because of VC monomer diffused into the crosslinked PBA phase to form the grafting transition layer, which improved the compatibility between PBA and PVC.TEM micrographs showed that AIMs with the structure of PBA/PMMA/PVC and PBA/PVC were well distributed in PVC matrix. It was found that when part or all of PMMA in the shell were replaced by PVC, the modified AIM still showed a high toughening efficiency on PVC, especially when 27% and 100% of the shell were replaced by PVC. For AIM with the structure of PBA/PVC, it was found that the notched izod impact strength of PVC/AIM blends was enhanced with an increasing core-shell ratio. When the core-shell ratio of PBA/PVC was 73/27 and the amount of PBA was 8phr, the notched izod impact strength of the blends is 95kJ/m2,37 times higher than that of pure PVC. The fractured surface of the modified PVC showed an typical ductile fracture morphology.The above would instruct the preparation and application of AIM with good toghening efficiency on PVC.