High-impact polystyrene particles

The rubber particles should not be so small that they are completely embedded in a craze. It is interesting to note that in high-impact polystyrene crazes tend to be about 2 p.m thick and the optimum particle sizes observed as a result of experience are quoted in the range 1-10 p.m. For ABS the figures are about 0.5 p.m and 0.1-l.Op.m respectively. 

Transition from liquid behavior to solid behavior has been reported with fine particle suspensions with increased filler content in both Newtonian and non-Newtonian liquids. Industrially important classes are rubber-modified polymer melts (small rubber particles embedded in a polymer melt), e.g. ABS (acrylo-nitrile-butadiene-styrene) or HIPS (high-impact polystyrene) and fiber-reinforced polymers. Another interesting suspension is present in plasticized polyvinylchloride (PVC) at low temperatures, when suspended PVC particles are formed in the melt [96], The transition becomes evident in the following... 

Figure 6. Different particle structures in high impact polystyrene (73) (85).

There are some additional applications of the theory which are presently under investigation. These are the effects of drawing on fibers for which the three-dimensional theory with transverse symmetry is applicable and the toughening mechanism in high impact polystyrene for which the flaw spectrum may be viewed as caused by the size, orientation, and spacing distributions of the rubber particles. 

Bucknall and Smith (17) concluded that crazing is the dominant mechanism to toughen high impact polystyrene and related polymers. One important function of the rubber particles is to serve as craze initiators and stabilizers in the glassy matrix. However Newman and Strella (18) concluded from optical microscope studies that cold drawing is responsible for toughness in ABS. 

High Impact Polystyrene (UPS) obtained by means of copolymerization of styrene with rubber represents heterogeneous system consisting of polystyrene matrix and the particles of rubber phase dispersed in it the particles in their turn keep the graft copolymer and a great number of occluded polystyrene O/,Physical and mechanical properties of HIPS are defined... 

In 1954, Dow finally perfected a can process to make high-impact polystyrene (HIPS). The secret was that the traditional can process could not simply be used since the product would be full of gel particles of rubber ( fish-eyes ) instead, the styrene-rubber mixture was first carried out to 30% conversion with shearing agitation. Then the mixture was transferred to 10 gallon cans where the reaction was completed. This process was documented in the now famous Amos patent [18]. 

Bulk polymerization is the main process for making high-impact polystyrene (HIPS). Polybutadiene is dissolved in styrene at 3-10% (w/w) concentration and the styrene is polymerized with careful agitation. Phase separation occurs with polybutadiene-g-polystyrene separating out. The final product is a dispersion of polybutadiene particles, which themselves contain occluded polystyrene. Polymerization conditions are adjusted to control the size and volume of these particles, which range respectively from 0.1 to 6.0 pm and 0.1 to 0.4 volume fraction of the material. 

Craze formation is a dominant mechanism in the toughening of glassy polymers by elastomers in polyblends. Examples are high-impact polystyrene (HIPS), impact poly(vinyl chloride), and ABS (acrylonitrile-butadiene-styrene) polymers. Polystyrene and styrene-acrylonitrile (SAN) copolymers fracture at strains of 10 , whereas rubber-modified grades of these polymers (e.g., HIPS and ABS) form many crazes before breaking at strains around 0.5. Rubbery particles in... 

Crosslinking Reactions in High Impact Polystyrene Rubber Particles... 

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