Agglomeration of the poly(butadiene-styrene) latex triggered by CO₂bubbling and the preparation of poly(methyl methacrylate-butadiene-styrene) core/shell particles with a wide size distribution

摘要

In order to meet the requirement of impact modifier, the agglomerated butadiene-styrene rubber (a-SBR) latexes were first prepared by bubbling CO₂into original butadiene-styrene rubber latex with the diameter about 100 nm, and then the poly(methyl methacrylate-butadiene-styrene) latexes (a-MBS) with a wide particle size distribution were fabricated via seeded emulsion copolymerisation of styrene and methyl methacrylate onto the a-SBR seeds. It was found that the pH value of the system decreased slowly with the time of CO₂bubbling, while a-SBR particles were not enlarged until the pH value reduced to about 8. In particular, when the pH value decreased to around 7, the size of a-SBR particles enlarged dramatically and the agglomerated system should be adjusted immediately to alkaline condition with NaOH aqueous solution. Transmission electron microscopy observation indicated that the a-MBS particles with a wide size distribution were successfully prepared. Moreover, both the shell thickness and grafting efficiency of the MBS particles decreased gradually with the increasing SBR particle size, while the rubber volume fraction of MBS particles increased. The whole process of agglomeration and grafting copolymerisation is mild, efficient and has great potential in the industrial application.