Preparation Of Crosslinked Polystyrene-Polyisoprene Core-Shell Nano-Particles And Their Reinforcement Of Styrene Butadiene Rubber

The concept of ideal filler for rubber reinforcement which have characteristics of nano-scale, spherical, well dispersed, some surface activity, lower density and low cost was proposed according to the problems of traditional fillers. Rubber filler model that nanoparticles with hard core and soft shell structure was designed based on the concept of the ideal filler and the ideas of polymer synthesis. Subsequently, core-shell structure nanoparticles that crosslinked polystyrene as core and polyisoprene as shell were prepared. Then the particles were filled in SBR and their properties were studied.Crosslinked polystyrene-polyisoprene (PS-PI) nano-particles with a core-shell structure were successfully prepared via two-stage seeded emulsion polymerization. The first stage was synthesis of crosslinked polystyrene latex particles which were served as seeds, then scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to characterize the morphology, size and size distribution of the PS particles, and effect factors such as feeding method and constituents on the latex particles were discussed. In the second stage, the swelling manner was employed to prepared particles with core-shell structure, which polyisoprene was coated on seed latex particles. TEM, DLS, DSC and IR results confirmed the core-shell morphology of the PS-PI particles. Afterwards influences of temperature and pressure on the properties of the core-shell nano-particles were investigated. In addition, core-shell structured latex nano-particles with different shell thickness were prepared by controlling the amount of shell monomer. The average size of crosslinked PS particles was 56.3nm while PS-PI particles ranged from 59.3nm to 70.1nm.Composites that crosslinked PS and PS-PI core-shell nanoparticles with different shell thickness filled in styrene butadiene rubber (SBR) were prepared by means of latex compounding method. Meanwhile, properties of the composites regarding the PS-PI as whole reinforcing filler, the core part of the core-shell particles as reinforcing filler and the shell part of the core-shell particles as the rubber matrix were compared. Results showed that crosslinked PS and PS-PI nano-particles exhibited significant reinforcement to styrene butadiene rubber matrix, while pure crosslinked PS revealed better reinforcing effect than PS-PI particles. Mechanical properties of composites trended to decrease with the increase of the shell thickness of PS-PI filler particles.