Solvent effect on thermal degradation of polystyrene

Abstract

SynopsisThe thermal degradation of polystyrene ( P S ) in various kinds of solvents was studied in the temperature range from 300 to 450°C. The conversion of PS to low molecular weight products was dependent on the hydrogen donating ability of the solvents used Solvents with greater donating ability resulted in less conversion of PS. A different degradation behavior was evident when phenols or other kind of solvents were used. These reaction properties are explained with a proposed degradation mechanism that includes hydrogen transfer steps from solvents to intermediate PS radicals and from PS to the solvent radicals.

Selective pyrolysis of polystyrene to that with a desired low polymeric degree

“…In the previous article, 15 we explained the thermal degradation behavior of PS in phenol with a random scission mechanism as follows. During the pyrolysis, phenoxy radicals are formed from phenol molecules and abstract hydrogens from PS at random positions of its chain to form carbon radicals, and then the polymers having carbon radicals rupture through ␤-scission.…”

“…Thus, the decrease in M w is accompanied by a great decrease in the amount of the desired low polymeric polymer. In the present experiments, PS depolymerized considerably above 350°C (from GPC measurement and analysis of the amount of volatile products 15 ). On the other hand, when PS was pyrolyzed in the presence of sulfur or DPS, the polymer degraded below 350°C through the random scission mechanism, as stated above.…”

“…We have reported the properties of the pyrolysis carried out in solvents (pyrolysis-in-solvent) using polystyrene (PS) or its derivatives as feed polymers. [15][16][17] The reports indicate that the pyrolysis-in-solvent was able to inhibit the undesired reactions from occurring and to suppress the depolymerization if solvents used furnish suitable physicochemical properties like relatively low vapor pressures, even at higher temperature, great thermal stability, and hydrogen donating ability. Of the experiments having been made, the pyrolysis-in-solvent using tetralin especially was able to degrade the raw polymer without forming the by-products.…”

Fundamental Kinetics of Supercritical Coal Liquefaction: Effect of Catalysts and Hydrogen-Donor Solvents

“…Degradation of polymers in solution was proposed to counter the problems of low heat transfer rates and high viscosity of the melting polymer commonly encountered in polymer recycling by pyrolysis (Sato et al, 1990). The degradation of polystyrene (Murakata et al, 1993a;, poly(styrene-allyl alcohol) (Wang et al, 1995), poly(methyl methacrylate) (Madras et al, 1996a), poly (p-methyl styrene) (Murakata et al, 1993b) and poly (α-methyl styrene) (Madras et al, 1996b) in solution have been investigated.…”

“…An important parameter in the degradation of the polymers in solution is the influence of the solvent on the reaction. The solvent effect for polystyrene thermal degradation was investigated by Sato et al (1990). The conversion of polystyrene to low molecular weight products decreased with the increase of the hydrogen donating ability of the solvents.…”