Polystyrenes pyrolysis

Physical or chemical vapor-phase mechanisms may be reasonably hypothesized in cases where a phosphoms flame retardant is found to be effective in a noncharring polymer, and especially where the flame retardant or phosphoms-containing breakdown products are capable of being vaporized at the temperature of the pyrolyzing surface. In the engineering of thermoplastic Noryl (General Electric), which consists of a blend of a charrable poly(phenylene oxide) and a poorly charrable polystyrene, experimental evidence indicates that effective flame retardants such as triphenyl phosphate act in the vapor phase to suppress the flammabiUty of the polystyrene pyrolysis products (36). 

R. Aguado, M. Olazar, B. Gaisan, R. Prieto and J. Bilbao, Kinetics of polystyrene pyrolysis in a conical spouted bed reactor. Chemical Engineering Journal, 92, 91-99 (2003). 

This study showed that polystyrene pyrolysis in a free-fall reactor under vacuum is a promising technique to obtain important liquid chemicals such as benzene, toluene, and naphthalene besides styrene monomer and valuable gaseous output. The liquid yield... 

The results for other conditions for polystyrene pyrolysis were reported. For example, pyrolysis on different catalysts was shown to lead to modifications of the yield of specific components in the pyrolysate. During the pyrolysis of PS on solid acid catalysts, the increase of contact time and surface acidity enhanced the production of ethylbenzene. Pyrolysis in the presence of water increases the yield of volatile products and that of monomer [30]. Studies on the generation of polycyclic aromatic hydrocarbons (PAHs) in polystyrene pyrolysates also were reported [36]. It was demonstrated that the content in PAHs in polystyrene pyrolysates increases as the pyrolysis temperature increases. The analysis of the end groups in polystyrenes with polymerizable end groups (macromonomers) was reported using stepwise pyrolysis and on-line methylation [46]. 

Figure 6.2.2. Result for a Py-GC/MS analysis of polystyrene. Pyrolysis done on 0.4 mg material with M = 280,000 at 60Cf C in He, with the separation on a Carbowax type column.

The list of compounds generated in polystyrene thermal decomposition shown in Table 6.2.2 do not include char and hydrogen. However, both char (mostly carbon) as well as hydrogen result in polystyrene pyrolysis, mainly at higher temperatures and at high heating rates [6]. 

Phenyl radicals are indeed formed during polystyrene pyrolysis, as proven by low traces of biphenyl present in the pyrolysate. 

Polystyrene pyrolysis yielded an oil with a high content of styrene monomer (Fig.4). The reaction conditions were optimized to maximize the yield of styrene. A maximum of l6% (by weight) was obtained. The oil is suitable for reuse in the styrene manufacturing process. 

After brief discussion of the state-of-the-art of modern Py-GC/MS, some most recent applications for stixictural and compositional chai acterization of polymeric materials are described in detail. These include microstixictural studies on sequence distributions of copolymers, stereoregularity and end group chai acterization for various vinyl-type polymers such as polystyrene and polymethyl methacrylate by use of conventional analytical pyrolysis. 

The above strategy was tested [27] with a 3-layer LED consisting of a poly(2,5-thienylene vinylene) (PTV) layer, known to have particularly low oxidation potential [28], followed by a layer of l,4-fcrs-(4 -diphenylaminostyryl)-2,5-di-methoxy-benzene (DASMB) [29] and a layer of 2-(4-biphenyl)-5-(4-tcrt-butyl-pheenyl)-1,3,4-oxadiazol (PBD) dispersed in polystyrene (PS) in a 20 80 ratio. Films of poly-(2,5-thienylene-a-bromoethylcne) were obtained by vapor phase pyrolysis of 2,5-W.v-(bromomethyl)lhiophcne and subsequent vapor deposition of the quinoid monomers onto a cold substrate following a previously published procedure [30]. They were converted to PTV by temperature-induced elimination of HBr. 

Pyrolysis for the Recycling of Polystyrene Plastic (PSP) Wastes in a Swirling Fluidized-Bed Reactor... 

In the present study, the pyrolysis of a waste polystyrene plastic (PSP) has beat investigated in a swirling fluidized-bed reactor to develop an effective reactor. Effects of the reaction time, temperature, ratio of the swirling gas and the gas velocity on the yields of an oil and a styrene monomer have been discussed. 

Figure 6.17 Temperature-resolved in-source pyrolysis FTICR-MS of flame-retarded polystyrene (56 spectra with a sampling interval of 1.1 s) from 300 K to 1200K. After Heeren and Boon [224], Reprinted from International Journal of Mass Spectrometry and Ion Processes, 157/158, R.M.A. Heeren and J.J. Boon, 391-403, Copyright (1996), with permission from Elsevier...

The Curie Point flash evaporation-pyrolysis gas chromatography-mass spectrometric method [32] described in section 2.2.1.2 for the analysis of aliphatic hydrocarbons in soil has also been applied to the determination of polystyrenes in soil via identification and determination of their unzipping pyrolysis products, such as styrene monomer, a-methyl styrene, 3-methyl styrene, 4-methyl styrene, a-3 dimethyl styrene, 3-ethylstyrene, a-4 dimethyl styrene, 3.5 dimethyl-styrene, a-2 or 2,5 or 2.4 dimethyl styrene also various phenyl ethers. 

M. Brebu, E. Jakab, and Y. Sakata, Effect of flame retardants and Sb2C>3 synergist on the thermal decomposition of high-impact polystyrene and on its debromination by ammonia treatment, J. Anal. Appl. Pyrolysis, 79(l-2) 346-352, May 2007. 

W.J. Hall, N.M.M. Mitan, T. Bhaskar, A. Muto, Y. Sakata, and P.T. Williams, The co-pyrolysis of flame retarded high impact polystyrene and polyolefins, /. Anal. Appl. Pyrolysis, 80(2) 406-415, October 2007. 

M.A. Uddin, T. Bhaskar, J. Kaneko, A. Muto, Y. Sakata, and T. Matsui, Dehydrohalogenation during pyrolysis of brominated flame retardant containing high impact polystyrene (HIPS-Br) mixed with polyvinylchloride (PVC), Fuel, 81(14) 1819-1825, September 2002. 

A wide variety of polymers have been analyzed by gel-permeation, or size-exclusion, chromatography (sec) to determine molecular weight distribution of the polymer and additives (86—92). Some work has been completed on expanding this technique to determine branching in certain polymers (93). Combinations of sec with pyrolysis—gc systems have been used to show that the relative composition of polystyrene or acrylonitrile—polystyrene copolymer is independent of molecule size (94). Improvements in gpc include smaller cross-linked polystyrene beads having narrow particle size distributions, which allow higher column efficiency and new families of porous hydrophilic gels to be used for aqueous gpc (95). 

Typical chromatograms were observed when polystyrene was py-rolyzed in air and the pyrolytic products were analyzed by gas chromatography. A characteristic peak which was observed on the chromatograms obtained by the pyrolysis of maleic anhydride and the alternating styrene maleic anhydride copolymer but not with polystyrene was used as a reference peak. As shown in Table II, the ratio of the area under... 

It has been reported that pyrolysis gas chromatographic techniques could be used to differentiate between block and random copolymers (18). However, it was not possible to distinguish between the block copolymers and mixtures of polystyrene and the alternating copolymers of styrene and maleic anhydride by the PGC technique used in this investigation. However, differences were noted in the DTA thermograms of the alternating copolymer, the block copolymer, and the mixture of polystyrene and the alternating copolymer. 

The SIMS spectrum of a 0.5 mm thick film of polystyrene cast on silver is shown in Figure 8. The characteristic ions, phenyl-type (m/z 77, 78, 79), benzyl (m/z 91), and protonated styrene (m/z 105) along with higher m/z ions resembling those from pyrolysis studies, are observed. 

J.R. Ebdon, D. Price, B.J. Hunt, P. Joseph, F. Gao, G.J. Milnes, and K.L. Cunhffe, Flame retardance in some polystyrenes and poly(methyl methacrylate)s with covalently bound phosphorus-containing groups Initial screening experiments and some laser pyrolysis mechanistic studies. Polym. Degrad. Stab., 69, 267-277 (2000). 

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. 

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