Styrene physical constants

Experimental System The copolymerisation of styrene with methyl acrylate in toluene using azo-bis-iso- butyronitrile (AIBN) was selected as the model experimental system because the overall rate of reaction is relatively fast, copolymer analysis is relatively simple using a variety of techniques and the appropriate kinetic and physical constants are available in the literature. This monomer combination also has suitable reactivity ratios (i = 0.76 and r4 =0.175 at 80 C),(18) making control action essential for many different values if compositionally homogeneous polymers are to be prepared at higher conversions in a semi-batch reactor. 

The phenomenon of polymer swelling, owing to sorption of small molecules, was known even before Staudinger reported [1] in 1935 that crosslinked poly(styrene) swells enormously in certain liquids to form two-component polymer gels. The physical state of such systems varies with the concentration (C) and molecular structure of the sorbed molecules thus, the system undergoes transition at constant temperature from a rigid state (glassy or partially crystalline) at C < Cg to a rubbery state at Cg (the transition state composition). When C > Cg and the second component is a liquid, its subsequent sorption proceeds quickly to gel-saturation and of course a solution is produced if the polymer lacks covalently bonded crosslinks or equivalent restraints. Each successive physical state exhibits its own characteristic sorption isotherm and sorption kinetics. 

The detailed kinetic studies on the oxidation of saturated hydrocarbons cyclohexane [4,5] and adamantane [26] and epoxidation of unsaturated hydrocarbons [4,5,25] cis-cyclooctene, cyclohexene, styrene and trans-stilbene were done by measuring the rate of reaction with respect to the concentration of each reactant, substrate, catalyst, ascorbic acid, hydrogen ion and molecular oxygen. The dependence of the reaction rate at various initial concentrations of the reactants were determined. While varying the concentration of a particular reactant, the concentrations of other reactants were kept constant under identical physical conditions. 

A CSTR is commonly used for the bulk polymerization of styrene. Assume a mean residence time of 2 h, cold monomer feed (300 K), adiabatic operation (UA i = 0), and a pseudo-first-order reaction with rate constant k = 10 ° exp(—10000/T) h where T is in kelvin. The adiabatic temperature rise for complete conversion is approximately 400 K. Assume constant physical properties and ignore power input form the agitator. 

Acrylonitrile/Butadiene/Styrene (ABS) Acry-lonitrile/butadiene/styrene (ABS) polymers are not true terpolymers. As HIPS they are multipolymer composite materials, also called polyblends. Continuous ABS is made by the copolymerization of styrene and acrylonitrile (SAN) in the presence of dissolved PB rubber. It is common to make further physical blends of ABS with different amounts of SAN copolymers to tailor product properties. Similar to the bulk continuous HIPS process, in the ABS process, high di-PB (>50%, >85% 1,4-addition) is dissolved in styrene monomer, or in the process solvent, and fed continuously to a CSTR where streams of AN monomer, recycled S/AN blends from the evaporator and separation stages, peroxide or azo initiators, antioxidants and additives are continuously metered according to the required mass balance to keep the copolymer composition constant over time at steady state. 

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