Plastics thermal degradation products

Industrial painters may suffer adverse health effects from over exposure to paint by skin contact or accidental ingestion, from excessive inhalation of paint aerosol, solvent vapour, or of dust in the case of electrostatically-applied powder coatings (e.g. polyesters containing triglycidyl isocyanurate), or from exposure to thermal degradation products from heated paint or plastic coatings (Table 5.48). 

Contaminants in recycled plastic packaging waste (HDPE, PP) were identified by MAE followed by GC-MS analysis [290]. Fragrance and flavour constituents from first usage were detected. Recycled material also contained aliphatic hydrocarbons, branched alkanes and alkenes, which are also found in virgin resins at similar concentration levels. Moreover, aromatic hydrocarbons, probably derived from additives, were found. Postconsumer PET was also analysed by Soxhlet extraction and GC-MS most of the extracted compounds (30) were thermally degraded products of additives and polymers, whereas only a few derived from the original contents... 

T. Bhaskar, M. A. Uddin, K. Murai, J. Kaneko, K. Hamano, T. Kusaba, A. Muto and Y. Sakata, Comparison of thermal degradation products from real municipal waste plastic and model mixed plastics. J. Analytical and Applied Pyrolysis, 70, 579-587, (2003). 

V. Pacakova and P. A. Leclercq, Gas chromatography-mass spectroscopy and high performance liquid chromatographic analyses of thermal degradation products of common plastics.. Journal of Chromatography, 555, 229-237, (1991). 

The pyrolysis process for waste recycling is frequently done at larger scale than analytical pyrolysis. However, analytical pyrolysis studies are performed independently for the understanding and the optimization of such processes [10,16-19]. Also, model mixtures can be used in parallel with real samples. For example, the comparison of thermal degradation products from real municipal waste plastic and model mixed plastics can help understand the compounds generated in waste incinerators. In one such study [20], analytical pyrolysis of real municipal plastic waste obtained from Sapporo, Japan and model mixed plastics was carried out at 430 °C in atmospheric pressure by batch operation. The chlorinated hydrocarbons found in degradation liquid products of poly(ethylene)/poly(propylene)/ poly(styrene)/poly(vinyl chloride) and other polymeric mixtures were monitored. It was determined that the presence of poly(ethylene terephthalate), in addition to chlorinated plastics in the waste, facilitates... 

For samples that meet the solubility requirements of the SEC approach, analyses were also reported for additives in polymers such as PVC and PS [28,29]. Direct SEC analysis of PVC additives such as plasticisers and thermal stabilisers in dissolution mode has been described [28,30,31 ]. In the analysis of a dissolved PS sample using a SEC column of narrow pore size, the group of additives was separated on a normal-phase column after elution of the polymer peak [21]. Column-loading capacity of HPSEC for the analysis of additives, their degradation products and any other low-MW compounds present in plastics has been evaluated for PS/HMBT, PVC/TNPP and PVC/TETO (glyceryl tri[l-14C] epoxyoleate) [31]. It was shown that HPSEC can be used to separate low-MW compounds from relatively large amounts of polymers without serious loss of resolution of the additives the technique has also been used for the group analysis of chlorohydrin transformation products of the TETO model compound [32]. 

Copolymers of itaconic esters with butadiene have not yet been used technically. On the other hand, acrylonitrile containing copolymers with other components have been studied from several points of view. Standard Oil Co. has claimed a terpolymer of isobutylene, butadiene, and acrylonitrile, and BASF a similar product of butadiene, acrylonitrile, and styrene. The films from these combinations are said to have high flexibility and cold resistance. However, all butadiene containing copolymers are not light fast. Copolymers of butadiene, acrylonitrile, and unsaturated dicarboxylic esters are suggested for plasticizing PVC, but they must be thermally degraded before they are combined with the polymer. 

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