Plastics thermal degradation

Nevertheless, the melt flow indexer is a very useful instrument besides measuring MFI. It can be used for studying plastic thermal degradation, by consecutive running of the same material or by running hot melt slow and recording MFI over time. By doing so, various antioxidants and their various amounts can be tested... 

Plastic content, effect on flexural strength of composite materials, 259 Plastic lumber, 2, 15, 238 Plastic thermal degradation, 628 Plasticized, 59... 

Polymeric membranes have shown promise for CO2 capture but suffer from issues such as plasticization, thermal degradation or polymer decomposition, and loss of selectivity or permeability over time or lower selectivity at high temperatures [6]. 

Polyhydroxyalkanoates, Polyhydroxybutyrate, History, Bacterial synthesis. Chemical synthesis. Genetic engineering. Mechanical properties. Thermal transitions. Crystallization, Plasticizers, Thermal degradation. Processing, Applications... 

Mass spectrometry This is often used for analysis of plastics. Thermal degradation can be carried out using an ion source, or in a pyrolyzer connected directly to a mass spectrometer or via a chromatographic column. Two soft ionization techniques, electrospray ionization and matrix-assisted laser desorption ionization (MALDI), are the most common in the analyses of large molecules. MALDI-MS is usually used offline but online connection with a... 

Gels Small round surface defects that resembles distorted plastic Poor mixing of plastic, thermal degradation of plastic at the barrel walls, un-melted plastic... 

One of the limiting factors in the use of plastics at high temperatures is their tendency to not only become softer, but also to thermally degrade. Thermal degradation can present an upper limit to the service temperature of plastics. Thermal degradation can occur at temperatures much lower than those at which mechanical failure is likely to occur. Plastics can be protected from thermal degradation by incorporating stabilizers into them. Stabilizers can work in a variety of ways, but discussion of these mechanisms are beyond the purpose of this book. 

The thermal degradation of mixtures of the common automotive plastics polypropylene, ABS, PVC, and polyurethane can produce low molecular weight chemicals (57). Composition of the blend affected reaction rates. Sequential thermolysis and gasification of commingled plastics found in other waste streams to produce a syngas containing primarily carbon monoxide and hydrogen has been reported (58). 

Plasticizer molecules can undergo thermal degradation at high temperatures. Esters based on the more branched alcohol isomers are more susceptible to such degradation. This can, however, be offset by the incorporation of an antioxidant, and plasticizer esters for cable appHcations frequently contain a small amount of an antioxidant such as bisphenol A. 

Extrusion Resins. Extmsion of VDC—VC copolymers is the main fabrication technique for filaments, films, rods, and tubing or pipe, and involves the same concerns for thermal degradation, streamlined flow, and noncatalytic materials of constmction as described for injection-molding resins (84,122). The plastic leaves the extmsion die in a completely amorphous condition and is maintained in this state by quenching in a water bath to about 10°C, thereby inhibiting recrystallization. In this state, the plastic is soft, weak, and pHable. If it is allowed to remain at room temperature, it hardens gradually and recrystallizes partially at a slow rate with a random crystal arrangement. Heat treatment can be used to recrystallize at controlled rates. 

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). 

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... 

Polymers have inherently high hydrocarbon ratios, making liquefaction of waste plastics into liquid fuel feedstocks a potentially viable commercial process. The objective is to characterise the thermal degradation of polymers during hydrogenation. LDPE is studied due to its simple strueture. Isothermal and non-isothermal TGA were used to obtain degradation kinetics. Systems of homopolymer, polymer mixtures, and solvent-swollen polymer are studied. The significant variables for... 

Polymer Degradation and Stability 53,No.2, 1996,p.l89-97 THERMAL DEGRADATION OF MIXED PLASTIC WASTE TO AROMATICS AND GAS... 

The ZSM-5 deactivation rate is decreased with progress of degradation reaction. And also the catalytic degradation of the plastics occurred at lower reaction temperature than the thermal degradation by about 40-60 °C. 

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... 

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