Polymerization thermal degradation

Acid-base, hydrolysis, hydration, neutralization, oxidation-reduction, polymerization, thermal degradation Adsorption-desorption, precipitation-dissolution, immiscible-phase separation, biodegradation, complexation Acid-base, neutralization, oxidation-reduction (most inorganic and some biologically mediated), adsorption-desorption, precipitation-dissolution, complexation Hydrolysis, oxidation-reduction (biodegradation of anthropogenic inorganics), immiscible-phase separation... 

The presence of stable free radicals in the final polycondensate is supported by the observation that traces of (11) have a strong inhibiting effect on the thermal polymerization of a number of vinyl monomers. Radical polymerization was inhibited to a larger extent by a furfural resin than by typical polymerization inhibitors (34). Thermal degradative methods have been used to study the stmcture of furfural resinifted to an insoluble and infusible state, leading to proposed stmctural features (35). 

Anionic Polymerization of Cyclic Siloxanes. The anionic polymerization of cyclosiloxanes can be performed in the presence of a wide variety of strong bases such as hydroxides, alcoholates, or silanolates of alkaH metals (59,68). Commercially, the most important catalyst is potassium silanolate. The activity of the alkaH metal hydroxides increases in the foUowing sequence LiOH < NaOH < KOH < CsOH, which is also the order in which the degree of ionization of thein hydroxides increases (90). Another important class of catalysts is tetraalkyl ammonium, phosphonium hydroxides, and silanolates (91—93). These catalysts undergo thermal degradation when the polymer is heated above the temperature requited (typically >150°C) to decompose the catalyst, giving volatile products and the neutral, thermally stable polymer. 

Heat Sensitivity. The heat sensitivity or polymerization tendencies of the materials being distilled influence the economics of distillation. Many materials caimot be distilled at their atmospheric boiling points because of high thermal degradation, polymerization, or other unfavorable reaction effects that are functions of temperature. These systems are distilled under vacuum in order to lower operating temperatures. For such systems, the pressure drop per theoretical stage is frequently the controlling factor in contactor selection. An exceUent discussion of equipment requirements and characteristics of vacuum distillation may be found in Reference 90. 

There have been many studies on the thermal and thermo-oxidative degradation of PMMA.23 24 It is well established that the polymer formed by radical polymerization can be substantially less stable than predicted by consideration of the idealized structure and that the kinetics of polymer degradation are dependent on the conditions used for its preparation. There is still some controversy surrounding the details of thermal degradation mechanisms and, in particular, the initiation of degradation.31... 

In contrast to the extensive work of the pure thermal degradation of polymers, less fundamental chemical information is available on the mechanism of oxidative degradation of polymeric materials. As another point of... 

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... 

Acetaldehyde is formed during the degradation of PET. Vinyl ester endgroups formed during thermal degradation of PET liberate vinyl alcohol on transesterification with hydroxyethylterephthalate polymeric endgroups (Fig. 10.6). The vinyl alcohol tautomerizes to form acetaldehyde, which can affect the taste of foods in PET food contact applications.1... 

The mass spectrum of polymeric sulfur S, prepared from either liquid sulfur or by extraction of commercial flowers of sulfur , has been measured and interpreted in terms of Ss, Sy, and Ss molecules leaving the polymer on heating and depolymerization [203]. This result is in agreement with depolymerization studies in solution which also show Ss and Sy as the major thermal degradation products [174]. 

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