Polystyrene thermal degradation

Polystyrene - Thermal degradation is the simplest of the current techniques used to recover feedstock chemicals from styrene-based polymers and has therefore been studied extensively. Investigations of the product distributions from thermal degradation of polystyrene have mainly focused on liquid products. It has been observed that the yield and the composition of liquid products vary strongly with temperature and the reactor configuration,... 

This comprehensive article supplies details of a new catalytic process for the degradation of municipal waste plastics in a glass reactor. The degradation of plastics was carried out at atmospheric pressure and 410 degrees C in batch and continuous feed operation. The waste plastics and simulated mixed plastics are composed of polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene, and polyethylene terephthalate. In the study, the degradation rate and yield of fuel oil recovery promoted by the use of silica alumina catalysts are compared with the non-catalytic thermal degradation. 9 refs. lAPAN... 

Similarly, toluene suspensions of the polystyrene housing of TV sets were examined by means of TPPy-FTMS (300-1200 K) [224], Diphenylether (DPE) was evidenced by peaks at m/z 141, 142 and 170 and decabromobiphenyl (DBBP) by m/z 943 and 864. Decabromodiphenyl ether (DBDPE) was recognised by thermal degradation products around m/z 800... 

Uses. Solvent for polymers polymerization catalyst stabilizer against thermal degradation in polystyrene UV stabilizer in polyvinyl and polyolefin resins... 

Richards and Slater (75) used a labelled polystyrene to demonstrate the existence of intermolecular chain transfer in the thermal degradation process. Polystyrene-14C, prepared in the normal way, was mixed with an inactive polystyrene specially prepared with weak links so that it degraded at temperatures where the polystyrene-14C was stable when on its own. Appearance of styrene- C monomer in the volatile degradation products proved the existence of intermolecular chain transfer (Reaction 9). 

The dithiocarbamates have the pentacoordinate binuclear structure (44). The diamyl- and diethyl-dithiocarbamate complexes have been found to inhibit the hardening of asphalt, but the effect appears too weak to be useful.127 The latter complex is an effective antioxidant for polyethylene,128 polypropylene,129 polystyrene,130 poly(methyl methacrylate)130 and an isoprene-styrene copolymer.131 The di-n-butyldithiocarbamate complex is important in the vulcanization and injection moulding of rubber,132 as a stabilizer against photolytic and thermal degradation. 

Sinister, C., F. Caron, and R. Gedye. 2004. Determination of the thermal degradation rate of polystyrene-divinyl benzene ion exchange resins in ultra-pure water at ambient and service temperature. J. Radioanal. Nucl. Chem. 261 523-531. 

Costa, L. Camino, G. Thermal degradation of polymer-fire retardant mixtures Part VII—Products of degradation and mechanism of fire retardance in polystyrene-chloroparaffin mixtures, Polymer Degradation and Stability, 1985, 12(4), 287-296. 

Costa, L. Camino, G. Trossarelli, L. A Study of the thermal degradation of polystyrene-chloroalkane misture by thermogravimetry-high resolution gas chromatography, Journal of Analytical and Applied Pyrolysis, 1985, 8, 15-24. 

Ebdon, J.R., Hunt, B.J., and Joseph, P., Thermal degradation and flammability characteristics of some polystyrenes and poly(methylmethacrylate)s chemically modified with silicon-containing groups, Polym. Degrad. Stab. 2004, 83, 181. 

Although solution blending has only been used at the lab scale at this time, compared with the in situ process, it may be more industrially friendly, particularly for the primary polymer producers who have operations, which can easily recover and recycle the solvent. High dilution is required and this may have an effect on the production of the PNs and the process is quite dependent on the individual polymer. Some polymers have many solvents from which to choose while others do not. A typical example is polystyrene, which can dissolve in a variety of solvents, so it is easy to find a solvent that is compatible with both the clay and the polymer. Polyolefins, on the other hand, require high boiling solvents and the high temperature may exert an effect of thermal degradation on the modifier. 

Guaita, M., Chiantore, O., and Costa, L. Changes in degree of polymerisation in the thermal degradation of polystyrene. Polymer Degradation and Stability 1985 12 315. 

Bourbigot, S., Gilman, J.W., and Wilkie, C.A. 2004. Kinetic analysis of the thermal degradation of polystyrene-montmorillonite nanocomposite. Polym. Deg. Stab., 84(3) 483 -92. 

In cases where no additional oxygen is present, polystyrene can undergo nearly pure thermal degradation. The two prevalent mechanisms are sequential elimination of monomer units, which is called unzipping or depolymerization. In this case, styrene monomer is formed. Random chain scission can also occur. It is sometimes combined with unzipping at the reactive broken chain ends. At temperatures approaching 300 °C, up to 40 % of a polystyrene molecule can be converted to styrene monomer. 

Molecular weight and polydispersity of the acetone extracted fractions from thermally degraded samples were determined by SEC with a Jasco PU-1580 HPLC pump equipped with two Pigel mixed D columns (Polymer Laboratories UK) connected in series, and a Jasco 830RI refractive index detector. Sample elution was with THF at 1 ml/minute flow rate. The instrument was calibrated with standard polystyrene samples. 

A. Karaduman, E. H. Simsek, B. Cicek and A. Y. Bilgesu, Thermal degradation of polystyrene wastes in various solvents. Journal of Analytical and Applied Pyrolysis, 62, 273-280 (2002). 

Polystyrene (PS). The thermal degradation proceeds again by C-C scission, which is then followed by a complex radical chain reaction. In the early stages of reaction and at low temperatures (290°C), the primary products are styrene, diphenylbutene, and triphenyUiexene. At higher temperature or longer residence times, the final stable products are toluene, ethylbenzene, cumene, and triphenylbenzene [47]. Fluidized-bed pyrolysis was applied successfully to pure PS more than 60% of monomer and 25% of other aromatics were obtained at a pyrolysis temperatnre of 515°C [25, 26]. 

T. Bhaskar, T. Matsui, M. A. Uddin, J. Kaneko, A. Muto, and Y. Sakata, Effect of Sb203 in brominated heating impact polystyrene (HIPS-Br) on thermal degradation and debromination by iron oxide carbon composite catalyst (Fe-C), Appl. Catal. B. Env., 43, 229-241 (2003). 

FIGURE 25.25 SEM image of the cross-section of a silica layer with spherical macropores resulting from the thermal degradation of polystyrene latex. 

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