PE degradation

Ishihara et a/.14 have also studied the catalytic degradation of PE over amorphous silica-alumina in a continuous flow fixed bed reactor. Careful measurements of the temperature gradients in the reactor showed that some of the PE degradation takes place by thermal cracking in the high temperature zones located prior to the catalytic fixed bed. Therefore, when the molten... 

Figure 5.5 Relationship between the molecular weight reduction and the branching concentration during the PE degradation over amorphous silica-alumina.I3 (Reprinted from J. Appl. Polym. Sci., 38, Y. Ishihara, H. Nambu, T. Ikemura and T. Takesue, page 1491. 1989, with permission from Elsevier Science)...

Figure 5.17 GC-MS analysis of the oils produced by thermal-catalytic PE degradation at 400 °C in a two-zone reactor with assignments of the peaks corresponding to aromatic hydrocarbons.43...

PES degrades much faster in freshwater than in seawater. In contrast, PBS degrades slowly in both freshwater and seawater. 

The study of the chemistry of the PE surface is very important as oxidised groups are more easily degraded by microorganisms and because oxidised groups modulate microbial attachment by increasing the hydrophilicity of the surface, which implies that PE degradation will be boosted if a more oxidised surface is used as a substrate. [8]. 

These data indicate the S-type mechanism of PE degradation. The decomposing species can be oxidative enzymes generated by bacteria and micro-organisms, for which PE acts as a carbon feed medium. 

Combining the data for PP and PE degradation we can conclude that, although these polymers decompose slowly, the rearrangement of their structure during oxidation can lead to undesirable consequences for the living body. 

Filled (with talcum, asbestos, calcium carbonate) and/or reinforced TPO have lower thermo-oxidative stability than the basic resin, which is explained by the content of iron or manganese from the filler or by the reinforcement materials that accelerate PE degradation. 

Scheme 2. Free-radical chain mechanism for PE degradation Reprinted from [a.53] with permission from ACS...

It will be seen in Section 4 that the rate of the abiotic and hence the biodegradation process can be readily controlled by antioxidants whereas no comparable control process has yet been developed for hydro-biodegradable polymers. A second conclusion was that starch plays no part in the biodegradation of a polyethylene matrix until the latter has been extensively peroxidised in the presence of transition metal ions. Similar conclusions have been reached by Wool [56] who showed that in the absence of PE degradation in starch-PE blends, biodegradation is controlled by the rate of migration... 

David and co-workers [57] confirmed the bioerosion of polyethylene films, peroxidised in the presence of cobalt acetylacetonate (Coacac) at 40°-70 °C both in compost and in a liquid medium by respirometry in the presence of an extract of microorganisms obtained from compost. The latter provides a method of measuring bioassimilation complementary to that described above. Table 5 shows PE degradation as... 

High-temperature aetivity of PCA in radical reactions is additionally confirmed by stabilizing effect of anilidophenylphosphate (BT-5) on PE degradation at 300°C. Application of such a model system to this particular case is desirable, because the radical-chain type of PE thermal oxidation at 200 - 250°C is well-known. It is also forecasted well for higher temperatures and, therefore, at some chain branching degree is forecasted well for carbonyl structures. 

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