Polyalkene plastics

Table 11.3 shows the yield of gas, oil/wax and char from the fixed bed pyrolysis of the main polyalkene plastics, polyethylene and polypropylene, found in municipal solid waste [7-15], Table 11.4 shows the gas, oil/wax and char from the pyrolysis of other plastics [7-9, 14-17], All of the plastics produced an oil/wax and gas and in some cases a char. The product yield related directly to the type of plastic, the reactor type... 

Table 11.3 Product yield from the pyrolysis of polyalkene plastics...

Table 11.3 shows that, in most cases, the three polyalkene plastics prodnced very similar product yields, with high yields of wax, and hydrocarbon gas and negligible char yields. Higher temperatnres of pyrolysis result in thermal cracking of the oil/wax to prodnce increased concentrations of gas. For example, Kaminsky et al. [9] reported an oil/wax yield of 92.3 wt% and 7.6 wt% gas, at a pyrolysis temperature of 530°C in a flnidized bed. However at the higher temperature of 760°C, the oil/wax was thermally degraded to produce 42.4 wt% oil/wax and 55.8 wt% gas. 

Figure 11.5 shows that the functional group compositional analysis of the pyrolysis oil/waxes derived from the fixed-bed pyrolysis of PVC, PS and PET is very different from the polyalkene plastic pyrolysis oil/waxes. The spectra of the PVC pyrolysis oil/wax shows that the characteristic peaks of alkanes and alkenes are present as described for the polyalkene plastics. Since the PVC plastic polymer is based on a similar backbone structure to the polyalkene plastics, a similar degradation product oil/wax composition may be expected. However, the spectra for PVC in Figure 11.5 show that there are additional peaks in the region of 675-900 cm and 1575-1625 cm The presence of these peaks indicates the presence of mono-aromatic, polycyclic aromatic and substituted aromatic groups. Benzene has been identified as a major constituent in oils derived from the pyrolysis of PVC whilst other aromatic compounds identified included alkylated benzenes and naphthalene and other polycyclic aromatic hydrocarbons [19, 32, 39]... 

The first step in the synthesis of nonvolatile plasticizers - which are of increasing importance - is hydroformylation of a long-chain olefin, for which rhodium phosphite catalysts have very useful properties. The current use of sterically hindered phosphites as antioxidants for polyalkenes together with their much simpler... 

Polymers used for engineering purposes tend to be relatively resistant to chemical attack, but the strength of certain polymers can fall dramatically in the presence of particular environments through the process of environmental stress cracking. The problem is very specific to certain polymer environment combinations such as PMMA with alcohols and polyalkenes in detergents and can lead to premature failure at very low stresses through either plasticization or a reduction in surface energy. 

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