Yielding of Thermoplastics

From a macroscopic point of view, yielding of thermoplastic or thermosetting polymers is similar and depends mainly on Tg — T or T/Tg, as a reduced parameter. 

The latex of the Sapota achras yields a thermoplastic material, chicle, consisting of about 17.4% hydrocarbon, 40% acetone soluble resin and 35% occluded water. The hydrocarbon appears to contain both trans- and c/s-polyisoprene. Although originally introduced as gutta pereha and natural rubber substitutes, deresinated chicle has become important as the base for chewing gum. Like other polyisoprenes, it is meeting competition from synthetic polymers. 

In initial tests to check the approach, sheet samples of thermoplastic ethylene tetra-fluoroethylene (ETFE) were used, with a permeation cup control test yielding a Q value of... 

The discovery in the early 1980s that cationic palladium-phosphine complexes catalyse the copolymerisation of carbon monoxide with ethene or a higher a-olcfin to yield perfectly alternating polyketones has since attracted continuous increasing interest [1,2]. This is because the monomers are produced in large amounts at a low cost and because polyketones represent a new class of thermoplastics of physical-mechanical and chemical properties that have wide applications [3-6]. In addition, easy functionalisation can open the way to a large number of new materials [7]. The copolymerisation has... 

Gel permeation chromatography Is the method of choice for analysis of thermoplastic resin systems. Corrected for imperfect resolution, chromatogram interpretation yields accurate molecular descriptions, including theoretical, kinetic distributions (, ) The current research is designed to extend the utility of this analytical tool to the analysis of thermoset resins. 

In particular, we will try to point out the specificity of thermosets compared with thermoplastics. A very good reference for the yielding and fracture of thermoplastics is the book of Kinloch and Young (1983). 

A commercial synthesis of 2,6-diphenylphenol is reported by Hay at General Electric, USA811. First, cyclohexanone was condensed with 50% sodium hydroxide at 150-190 °C giving the 2-mono- and the 2,6-disubstituted cyclohexanone derivatives. In the second step, after removal of water and sodium hydroxide, these are dehydrogenated at 300-350 °C with a palladium aluminium oxide catalyst for 20 minutes (e.g. 45 % total yield of 2,6-diphenyl-phenol). It is a useful compound in technical production and has been studied by Hay and coworkers 82) (see also 83,84)). Polymeric diphenylphenol ethers ( Tenas ) 85) or copolymers with polystyrene ( Normyl ) have been produced on a large scale by General Electric e.g. as thermoplasts 86). 

Styrenic copolymers are materials capable of thermoplastic processing which, in addition to styrene (S), also contain at least one other monomer in the main polymer chain. Styrene-acrylonitrile (SAN) copolymers are the most important representative and basic building blocks of the entire class of products. By adding rubbers to SAN either ABS (acrylonitrile-butadiene-styrene) or ASA (acrylate-styrene-acrylonitrile) polymers are obtained depending on the type of rubber component employed. These two classes of products yield blends composed of ASA and polycarbonate (ASA -f PC) or ABS and polyamide (ABS -(- PA). 

The pyrolysis of mixed waste thermoplastics in a pilot plant of 360 ton/year at the Korea Institute of Energy Research (KIER), as shown in Figure 5.6, has an oil yield of about 82% for continuous process control over two days. The distribution of oil product is 27% gasoline product and 73% heavy oil product. Also the yield, of gas product is 10-15% and consists of about 18.1% Ci, 15.2% C2, 30.3% C3, 21.9% C4 and 14.3% C5 components. Similar results were obtained by other researchers, as shown in Table 5.1. 

Table 11.4 shows the product yield of gas, oil/wax and char from the pyrolysis of other single plastics, including thermoplastics and thermoset plastics. Pyrolysis of polystyrene under moderate temperatures of between 500 and 600°C produces high levels of oil. Even at higher temperamres above 700°C, there is a high conversion of the polymer to oil. In fact the oil mainly consists mainly of the monomer styrene [8, 9, 23, 24]. 

Research on the pyrolysis of thermoset plastics is less common than thermoplastic pyrolysis research. Thermosets are most often used in composite materials which contain many different components, mainly fibre reinforcement, fillers and the thermoset or polymer, which is the matrix or continuous phase. There has been interest in the application of the technology of pyrolysis to recycle composite plastics [25, 26]. Product yields of gas, oil/wax and char are complicated and misleading because of the wide variety of formulations used in the production of the composite. For example, a high amount of filler and fibre reinforcement results in a high solid residue and inevitably a reduced gas and oiFwax yield. Similarly, in many cases, the polymeric resin is a mixture of different thermosets and thermoplastics and for real-world samples, the formulation is proprietary information. Table 11.4 shows the product yield for the pyrolysis of polyurethane, polyester, polyamide and polycarbonate in a fluidized-bed pyrolysis reactor [9]. 

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