Styrene polymerization heat effects

Since Schultz (7) found that ultimate conversion depended considerably on temperature (in a highly polymerized methyl methacrylate system), similar effects would be expected in the postirradiation-heating of the PVC-styrene system. Such effects have indeed been found. Figure 4 shows the effect of heating temperature on the conversion level at two different radiation doses. No increased conversion is found for a temperature higher than 75 °C. This seems to indicate that a more or less definite melting point of the partially polymerized mixture exists. When this temperature is reached during the postirradiation treatment, the reaction runs to a point of termination and is unaffected by further temperature increases. 

Kim, K.J. Choi, K.Y. Alexander, J.C. Dynamics of a CSTR for styrene polymerization initiated by a binary initiator mixture. II. Effect of viscosity dependent heat transfer coefficient. Polym. Eng. Sci. 1992, 32 (7), 494-505. 

Numerous polymer—polymer contacts are realized in the dry gel-type styrene—2% DVB copolymer (type IV). Only a thermodynamically good solvent, such as toluene, can overcome these strong interactions between the polymeric chains, resulting in the generation of a small quantity of heat, 25J/g. This value is similar to the heat effect of dissolution of linear polystyrene in a good solvent [137]. Increasing the DVB content to 20%... 

RAET polymerization of polar monomers (MMA, MA, and VAc ) was reported to be substantially accelerated by microwave heating. I,ess but still substantial acceleration was observed for styrene polymerization. " It is experted that monomers with a higher dielectric constant will be more effectively heated by miaowave irradiation. However, the effect particularly with MMA and MA was substantially greater than expected for an effect of temperature alone. An explanation for the miaowave effea was not provided. ... 

Yu (13) simulated a periodically operated CSTR for the thermal polymerization of styrene and found the MWD to increase at low frequencies but all effects were damped out at higher frequencies because of the limited heat transfer which occurs relative to the thermal capacity of industrial scale reactors. 

The dehydrohalogenation of 1- or 2-haloalkanes, in particular of l-bromo-2-phenylethane, has been studied in considerable detail [1-9]. Less active haloalkanes react only in the presence of specific quaternary ammonium salts and frequently require stoichiometric amounts of the catalyst, particularly when Triton B is used [ 1, 2]. Elimination follows zero order kinetics [7] and can take place in the absence of base, for example, styrene, equivalent in concentration to that of the added catalyst, is obtained when 1-bromo-2-phenylethane is heated at 100°C with tetra-n-butyl-ammonium bromide [8], The reaction is reversible and 1-bromo-l-phenylethane is detected at 145°C [8]. From this evidence it is postulated that the elimination follows a reverse transfer mechanism (see Chapter 1) [5]. The liquidrliquid two-phase p-elimination from 1-bromo-2-phenylethanes is low yielding and extremely slow, compared with the PEG-catalysed reaction [4]. In contrast, solid potassium hydroxide and tetra-n-butylammonium bromide in f-butanol effects a 73% conversion in 24 hours or, in the absence of a solvent, over 4 hours [3] extended reaction times lead to polymerization of the resulting styrene. 

OSHA PEL TWA 1 mg(Fe)/m3 ACGIH TLV TWA 1 mg(Fe)/m3 DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Poison by ingestion and intravenous routes. Experimental reproductive effects. Corrosive. Probably an eye, skin, and mucous membrane irritant. Mutation data reported. Reacts with water to produce toxic and corrosive fumes. Catalyzes potentially explosive polymerization of ethylene oxide, chlorine + monomers (e.g., styrene). Forms shock-sensitive explosive mixtures with some metals (e.g., potassium, sodium). Violent reaction with allyl chloride. When heated to decomposition it emits highly toxic fumes of HCl. 

Suspension polymerization is frequently employed as the second stage following a preliminary bulk polymerization, such as in the manufacture of some HIPS and ABS polymers. Polybutadiene or another elastomer is dissolved in liquid styrene, and this monomer or a mixture of styrene and acrylonitrile is polymerized in a batch kettle. The syrup produeed at 30-35% conversion is too viscous for effective mixing and heat transfer. It is therefore dispersed in water, and the polymerization is finished as a suspension reaction. 

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