Structural Design Of MBS Core-shell Particles

Core-shell structured particles, which comprise rubbery and glassy layers, had the distinct advantage of allowing independent control of the composition, morphology, size and properties. Many researches have been focused on investigations into their preparation, properties, and deformation behavior. Emulsion polymerization is a well-known technique for preparing latex polymers with defined structures. Depending on the polymerization parameters and conditions, the reaction can selectively yield a variety of particles with different morphologies. The changing of the internal structure of the modifier may affect the property of its host matrix.Methyl methacrylate-butadiene-styrene (MBS) is a typical core-shell rubber modifier, in which styrene and methyl methacrylate are grafted onto polybutadiene (PB) or SBR particles. In this work, all the MBS particles were designed with the same chemical composition, similar grafting degree but different internal structure. And the difference of internal structure was realized by controlling the ratio of’external-grafting’and’internal-grafting’of styrene. The work focused on the influence of the internal structure of MBS core-shell particles on the properties of PVC/MBS blends. From transmissionelectron microscope (TEM) photographs, it was found that three different internal structure:rarely sub-inclusion, a large number of small sub-inclusions and large sub-inclusions were realized. The results of the DMA analysis illustrated that the different internal structure affected Tg of the rubber phase and the storage modulus of the core-shell particles greatly. And the notched Izod impact test results showed that the MBS with large sub-inclusions had a lowest brittle-ductile transition (BDT) temperature. While the transparency test revealed that the present of sub-inclusions in rubbery phase reduced the transparency of the blend.Besides, three layers PSBM core-shell modifier is prepared by emulsion polymerization method. For PSBM particles, PS phase located in the inner core, PB phase located in the medium layer and PMMA is in the outer layer. The results show that the Izod impact strength of the three layers core-shell modifier-toughened PVC is higher than that of PVC blends toughened by MBS.