Rubbery-phase morphology, HIPS

Materials. The materials used in the present study include both commercial and experimental grades of HIPS. A large number of materials covering a wide range of.rubbery phase morphologies were Investigated. 

The preferred average particle size 1n HIPS was believed to be 0.8 ijm (J.). However, our current data indicate that a number average particle diameter of 1.05 urn and 0.5 -urn appear to be a preferred size for HIPS and rubber-toughened polypropylene (PP), respectively. The morphology of the rubbery phase in a toughened PP appears to be less complex, as evidenced in Figure 2 where the dark, also osmium-stained, phase is the styrene-butadiene rubber (SBR) particles. No PP occlusions were found in this material since it is a physical blend of SBR and PP. 

The morphology of the rubber-modified polystyrenes system involves some complex aspects, such as particle size, size distribution, occlusions of polystyrene inside the rubber phase, interfacial bonding between the rubbery particles and the brittle matrix, etc. Many authors have observed that some of the most important factors in controlling the mechanical properties of HIPS and ABS are rubber particle size [49], volume fraction of the rubbery phase (rubber + occluded polystyrene) [50,51] and the degree of graft [52]. Grafting occurs during the polymerization of styrene when some of the free radicals react with the rubber... 

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