Thermal degradation—See

Control experiment in the absence of irradiation and Ti02, almost no thermal degradation (see Figure 31). 

Wood burns because the cell wall polymers undergo hydrolysis, oxidation, dehydration, and pyrolysis reactions with increasing temperature to give off volatile, flammable gases. The lignin component contributes more to char formation than do the cellulose components, and the charred layer helps insulate the wood from further thermal degradation see Chapter 13). 

Thermal decomposition 30, 50, 604, 1132 Thermal degradation see Degradation, thermal... 

Polymer degradation is highly dependent on chemical and physical factors. The chemical factors vill be examined in relation to thermal degradation (see Section 15.4.2). This section vill be focused exclusively on the influence of physical factors on polymer degradation. 

Cellulose thermo-oxidation proceeds through an analogous pathway to that already described for thermal degradation (see Figure 14.2), apart from the further oxidation of char formed during the first degradation step. 

Liquids and solids do not burn as such, but on exposure to heat vaporize or undergo thermal degradation to liberate flammable gases and vapours which burn. Some chemicals undergo spontaneous combustion (see page 214). 

PA-6,10 is synthesized from 1,6-hexamethylenediamine and sebacic acid, and PA-6,12 from 1,6-hexamethylenediamine and dodecanedioic acid. The melt synthesis from their salts is very similar to PA-6,6 (see Example 1). These diacids are less susceptible to thermal degradation.55 PA-6,10 can also be synthesized by interfacial methods at room temperature starting with the very reactive sebacyl dichloride.4 35 A demonstration experiment for interfacial polycondensation without stirring can be carried out on PA-6,10. In this nice classroom experiment, a polymer rope can be pulled from the polymerization interface.34... 

A number of polymers are capable of fulfilling these demanding requirements. Typically negative photoresists are based on cyclised poly(l,4-isoprene). These polymers are prepared by dissolving poly(l,4-isoprene) in an appropriate solvent and subjecting it to thermal degradation. This is followed by treatment with acid to produce the cyclised material (see Reaction 8.8). 

Similarly, Pd, Ag, and Pd-Ag nanoclusters on alumina have been prepared by the polyol method [230]. Dend-rimer encapsulated metal nanoclusters can be obtained by the thermal degradation of the organic dendrimers [368]. If salts of different metals are reduced one after the other in the presence of a support, core-shell type metallic particles are produced. In this case the presence of the support is vital for the success of the preparation. For example, the stepwise reduction of Cu and Pt salts in the presence of a conductive carbon support (Vulcan XC 72) generates copper nanoparticles (6-8 nm) that are coated with smaller particles of Pt (1-2 nm). This system has been found to be a powerful electrocatalyst which exhibits improved CO tolerance combined with high electrocatalytic efficiency. For details see Section 3.7 [53,369]. 

Thermal degradation of polymers can occur by three mechanisms (see Chapters 11 and 12) ... 

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