Styrene in polystyrene

Polymer in solution Any (e.g., a condensation product or another polymer phase) Heterogeneous bulk or solution polymerization Salt precipitating from a condensation reaction. Prepolymerized rubber precipitating from a solution of polystyrene in styrene monomer... 

Although there is dispute about the exact oxidation state of titanium in the active species [Ti(III) or Ti(IV)], it was suggested, from the results of ESR measurements, that Ti(III) species form highly active sites for producing syndiotactic polystyrene in styrene polymerisation systems with the TiBz4—[Al(Me)0]x catalyst [50]. The moderately low catalyst activity is attributable to the stability of the benzyl transition metal derivatives towards reduction. 

Polybutadiene rubbers are soluble in styrene. As the polymerization proceeds phase separation occurs, and the solution turns opaque because of the difference in refractive indices between the two phases. Initially polybutadiene in styrene is the continuous phase, and polystyrene in styrene is the discontinuous phase. When the phase volumes are equal and sufficient shearing agitation exists, phase inversion occurs. After this point polystyrene in styrene is the continuous phase, and polybutadiene in styrene is the discontinuous phase. Phase inversion is represented in Figure 4. A change in viscosity is also observed at phase inversion (. ... 

The separation of polystyrene and polybutadiene into two phases, both containing styrene, was used to measure polymer-solvent interaction parameters. By this technique, the mean interaction parameter, for polystyrene in styrene is 0.49 and that for polybutadiene in styrene, Xis, is 0.29. Phase behavior at higher concentrations was calculated from data obtained at concentrations of less than 35%. As a result, phase behavior during polymerization of high impact polystyrene was interpreted. 

Polystyrene Vinyl addition Bulk Solution of polystyrene in styrene and ethyl benzene 69.9 320 Heat... 

A solution of polystyrene in styrene for use as a low profile additive in polyester moulding compounds, b 33%... 

Figure 19 Variation of glass transition temperature with composition for solutions of polystyrene in styrene monomer. The lines represent calculations from the Gibbs-DiMarzio lattice model upper line calculation allows for holes while the lower...

Styrene—acrylonitrile (SAN) copolymers [9003-54-7] have superior properties to polystyrene in the areas of toughness, rigidity, and chemical and thermal resistance (2), and, consequendy, many commercial appHcations for them have developed. These optically clear materials containing between 15 and 35% AN can be readily processed by extmsion and injection mol ding, but they lack real impact resistance. 

In polymers such as polystyrene that do not readily undergo charring, phosphoms-based flame retardants tend to be less effective, and such polymers are often flame retarded by antimony—halogen combinations (see Styrene). However, even in such noncharring polymers, phosphoms additives exhibit some activity that suggests at least one other mode of action. Phosphoms compounds may produce a barrier layer of polyphosphoric acid on the burning polymer (4,5). Phosphoms-based flame retardants are more effective in styrenic polymers blended with a char-forming polymer such as polyphenylene oxide or polycarbonate. 

Styrene is a colorless Hquid with an aromatic odor. Important physical properties of styrene are shown in Table 1 (1). Styrene is infinitely soluble in acetone, carbon tetrachloride, benzene, ether, / -heptane, and ethanol. Nearly all of the commercial styrene is consumed in polymerization and copolymerization processes. Common methods in plastics technology such as mass, suspension, solution, and emulsion polymerization can be used to manufacture polystyrene and styrene copolymers with different physical characteristics, but processes relating to the first two methods account for most of the styrene polymers currendy (ca 1996) being manufactured (2—8). Polymerization generally takes place by free-radical reactions initiated thermally or catalyticaHy. Polymerization occurs slowly even at ambient temperatures. It can be retarded by inhibitors. 

Figure 3.8. Schematic representation of the polystyrene domain structure in styrene-butadiene-styrene triblock copolymers. (After Holden, Bishop and Legge )...

The valuable characteristics of polyblends, two-phase mixtures of polymers in different states of aggregation, were also discussed in the previous chapter. This technique has been widely used to improve the toughness of rigid amorphous polymers such as PVC, polystyrene, and styrene-acrylonitrile copolymers. 

Replacement, in full or in part, of the styrene by a monomer whose homopolymer has a higher Tg than polystyrene. In the ease of partial replacement it is also important that the copolymers have TgS intermediate to the two homopolymers. Fortunately this is usually the case. 

Since the last edition several new materials have been aimounced. Many of these are based on metallocene catalyst technology. Besides the more obvious materials such as metallocene-catalysed polyethylene and polypropylene these also include syndiotactic polystyrenes, ethylene-styrene copolymers and cycloolefin polymers. Developments also continue with condensation polymers with several new polyester-type materials of interest for bottle-blowing and/or degradable plastics. New phenolic-type resins have also been announced. As with previous editions I have tried to explain the properties of these new materials in terms of their structure and morphology involving the principles laid down in the earlier chapters. 

The properties of styrenic block copolymers are dependent on many factors besides the polymerization process. The styrene end block is typically atactic. Atactic polystyrene has a molecular weight between entanglements (Me) of about 18,000 g/mol. The typical end block molecular weight of styrenic block copolymers is less than Mg. Thus the softening point of these polymers is less than that of pure polystyrene. In fact many of the raw materials in hot melts are in the oligomeric region, where properties still depend on molecular weight (see Fig. 1). 

Addition of poly(styrene-block-butadiene) block copolymer to the polystyrene-polybutadiene-styrene ternary system first showed a characteristic decrease in interfacial tension followed by a leveling off. The leveling off is indicative of saturation of the interface by the solubilizing agent. 

The formation of the polyalloy results in improvement in the performance of the blends. This system is similar to the production of high-impact polystyrene (HIPS) where a rubber is dissolved in styrene monomer and then polymerized in the usual way. Even though the impact strength of the compatibilized PS-PE blend was higher than that of PS, it was much less than that of HIPS. In another study. Van Ballegooie and [55] have confirmed... 

Journal of Applied Polymer Science 73,No.7, 15thAug.l999, p.1139-43 MECHANISM STUDIES ON THE CATALYTIC DEGRADATION OF WASTE POLYSTYRENE INTO STYRENE IN THE PRESENCE OF METAL POWDERS... 

The cost of the raw materials is probably the most important factor in determining the price of polystyrene. In 1968 styrene sold for 7.750/lb30 while general-purpose polystyrene was selling ten for 12.50/lb31 This means around 60% of the selling price was spent for raw materials. It should be nearer 50%. 

A large variety of polymers has been considered. In the beginning, polystyrene and styrene/ divinylbenzene copolymers (Merrifield resins) were by far the most used.73 Then others were tested such as polyvinyls,47-50,61-64 polyacrylates,72 4,75 and cellulose.76,77 Most commonly, diphenylphos-phane groups were grafted on the polymeric support, either directly or via one CH2 group. 

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