Different deformation mechanisms of two modified‐polystyrene bimodal systems

Abstract

It is well known that the dominant toughening mechanism of rubber‐modified polystyrene is multiple crazing. Some researchers have investigated polystyrene that can be modified by rubbers with dual particle sizes, leading to better mechanical properties. That is, the way to absorb energy during the deformation process is crazing and cavitation induced by rubber particles. Two types of polybutadiene‐graft‐polystyrene (PB‐g‐PS) rubber modifiers which have core‐shell structures were synthesized via an emulsion graft polymerization using redox and oil‐soluble initiators, respectively. To balance the yield strength, general‐purpose polystyrene was blended with the PB‐g‐PS modifiers, as well as commercial high‐impact polystyrene. Blends were defined as R‐bimodal and O‐bimodal corresponding to dispersed PB‐g‐PS particles formed using the redox and oil‐soluble initiators, respectively. The impact strength of R‐bimodal was improved significantly by altering the ratio of core to shell. However, little change of impact strength was observed for O‐bimodal. Transmission electron microscopy images of fracture surfaces indicated that the deformation mechanism of R‐bimodal is shear‐yielding induced by multi‐crazing. Moreover, PB‐g‐PS particles dispersed in O‐bimodal can form a ‘cluster’ structure, leading to crazing to absorb energy. Scanning electron microscopy images also showed obvious distinctness between the R‐bimodal and O‐bimodal systems due to different deformation mechanisms. Copyright © 2010 Society of Chemical Industry

Incorporation of polybutadiene into waterborne polystyrene nanoparticles via miniemulsion polymerization

“…However, both mechanical properties were improved when employing the oil-soluble initiator 1,2-azobisisobutyronitrile, due to the larger PS occlusions generated in the rubber core. Also, this type of core-shell particles of PB-g-PS were introduced into commercial HIPS to improve the mechanical properties of the resulting composite [7].…”

Synthesis strategies in the preparation of high impact polystyrene with different type of particles as the dispersed phase, towards a balance between impact strength and gloss

“…Meanwhile the parallel polymerization strategy (Runs 5 to 7) has scarcely been reported for the production of this type of materials as it involves two parallel reactions up to a predetermined monomer conversion with an additional step that comprises the mixing of the two crudes in a third reactor to complete the polymerization (Perkins and Wilson 2000). Finally, the melt blending strategy (Runs 8 to 10) is the strategy mostly used at industrial scale when HIPS with bimodal or multimodal PSD is desired (Lavengood 1980;Okamoto et al 1991;Enríquez-Medrano et al 2012;Dai et al 2010;Lanza 1979). However, and unlike those reported in the literature, in this study the preliminary synthesis of two different HIPS with different morphology through the bulk-suspension polymerization is proposed, previous to the mixing of both HIPS.…”

“…As previously mentioned, the synthesis of HIPS with bimodal PSD, with the same or different particle morphology, has been reported to enhance impact resistance (Dai et al 2010); however, none of the referenced publications reported results related to optical properties. Only some patents can be found associated with the production of HIPS with high impact strength and high gloss (Dupre 1979;Perkins and Wilson 2000;Sheu 2002;Demirors et al 1998;Bowen and Hanner 1999).…”

Influence of submicron tiny gel rubber particles on the estimation of grafting and rubber efficiency in high-impact polystyrene

“…Several investigators also studied that bimodal rubber particle size distribution has a key role in enhancing the better impact toughness to HIPS. 19 Okamoto et al 20 suggested that the greater the difference in the sizes of the particles that constitute bimodal HIPS, the higher was the impact strength of Izod. The bigger particles absorb the applied energy and transfer its stress to its neighboring particles; the presence of many smaller particles along with bigger particles acts as craze arresters, thereby leading to higher impact strength.…”