Styrene copolymers processing data

A study was made of the thermal degradation behaviour of PS foams used as patterns in the lost foam process for metal casting. The data indicated that the thermal degradation of the pattern had a strong effect on mould filling and casting quality. The use of other types of foam such as PE, PP, PMMA and styrene-methyl methacrylate copolymers to overcome problems encountered with PS foam patterns is discussed. 7 refs. 

Mechanisms of liquid-liquid phase separation were studied in the binary styrene-acrylonitrile copolymer/poly(methyl methacrylate) system. Evidence is presented which suggests that spinodal decomposition occurs in this system. The Cahn theory provides an interpretation of key experimental results. Both a dispersed, two-phase structure and a highly interconnected, two-phase structure can be formed. These two structures coarsen at significantly different rates. The dispersed-phase structure coarsens by Ostwald ripening, an extremely slow process in the polymer-polymer system. The interconnected structure coarsens more rapidly. Data suggest that the mechanism of coarsening is viscous flow driven by interfacial tension. 

A plot of the mole fraction of isoprene in the SFR prepared copolymers as a function of the mole fraction of isoprene in the feed is shown in Figure 2. The data points are the results for the SFRP process initiated with BPO at 125 C in the presence of TEMPO the curve represents data reported by Wiley and Davis (6) for a conventional styrene/isoprene copolymerization initiated with peroxide at 100 C. The... 

To determine the SAN copolymer composition, the same procedure used for styrene/isoprene was followed. A series of reactions was performed varying the feed of acrylonitrile and measuring the incorporation of acrylonitrile in the copolymer at low conversion by NMR spectroscopy. All reactions were done in a closed pressure reactor at 115-120 C. The results of these experiments are shown in Table IV. A plot of the incorporation of acrylonitrile in the polymer (Fa) as a function of the acrylonitrile feed (fA) is shown in Figure 5. The data points are copolymer compositions for the SFR process while the curve represents literature data for a... 

A number of publications indicate that the reactivity of ra-DVB, rz, is rather close to that of styrene, r, both values being nearly equal to unity (Table 1.1). Therefore, a statistical copolymer would have to be obtained as a result of copolymerization. However, according to some other data, during the first stages of the process, the growing polymeric chains are enriched by the meta-divinyl monomer, which should inevitably result in an inhomogeneous distribution of crosslinks in the final network. 

Kinetic data on olefin polymerization by polymer-immobilized zirconocene are scarce. It is generally accepted that homogeneous metallocene catalysts contain uniform active sites however, if they are immobilized on a polymer support, the MWD polymer production becomes broader compared with a homogeneous catalyst [103]. Kinetic analysis of gas-phase ethylene polymerization catalyzed by (CH3)2[Ind]2ZrCl2 bound at a hydroxylated copolymer of styrene with divinylbenzene and previously activated with MAO (0.17 wt.% Zr) has been carried out [104]. The influence of temperature (333 to 353 K), ethylene partial pressure (2 to 6 atm) and MAO level (molar ratio of MAO to zirconium from 2600 to 10,700) were studied. The activity of the catalyst in the gas-phase process changed from 5 to 32 kg PE (g of Zr atm h)It is possible that there are two types of active site. They are stable to temperature and deactivated by the same mechanism. A first-order reaction takes place. The propagation rate constants of two active sites show a similar dependence on temperature. 

In a study of the flame retardance of styrene-methyl methacrylate copolymer with covalently bound pyrocatechol-vinyl phosphate, diethyl p-vinyl benzyl phosphonate, or di(2-phenyl ethyl phosphonate) groups. Ebdon and co-workers [23] obtained data on their decomposition behaviour. This was achieved by reducing the rate of liberation of flammable methyl methacrylate monomer during combustion. Possible mechanisms for these processes are suggested. Other methacrylate copolymers which have been the subject of thermal degradation studies include PMMA-N-methylmaleimide-styrene [24] and PMMA-ethylene vinyl acetate [25-27]. 

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