Process induced degradation

Thermal degradation is, like pyrolysis, degradation in an inert atmosphere or in the absence of an external reagent. Energy absorption leads to molecular dissociation through three major mechanisms acting alone or jointly  

Mechanical or flow-induced degradation of polymers may occur under extreme shear or extrusion flow conditions giving rise to unfolding of macromolecules in extensional flow with subsequent chain scission. 

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Progresses systematically through topics, from component degradations to contamination-, environment-, operation-, and process-induced degradations... 

Radiation-induced degradation reactions are in direct opposition to cross-linking or curing processes, in that the average molecular weight of the preformed polymer decreases because of chain scission and without any subsequent... 

Flow-induced degradation is intimately related to the nonequilibrium conformation of polymer coils and any attempt to interpret the process beyond the phenomenological stage would be incomplete without a sound understanding of chain dynamics. To make the paper self-contained and to provide a theoretical basis for the discussion, we have included some fundamental models of polymer dynamics in the next section which may also serve as a guideline for future work in the field of polymer degradation in flow. For the first-time reader, however, this section is not absolutely necessary. Further, any reader familiar with molecular rheology or interested only in experimental results can skip this section, only to go back whenever a reference is needed. 

The receptors are continuously subjected to a process of synthesis and destruction, which achieves a steady state. The concentration of receptors in the cell only reflects the situation of the steady state at that moment. As a consequence of hormone action, the number of receptors per cell drastically diminishes in the hours that follow. This observation has led to the postulation that the receptors undergo a process of destruction, or processing , induced by the hormone. Despite all efforts, receptor processing has not been deciphered. The destruction of receptors implies the existence of a proteolysis process. Nevertheless, signs of proteolysis, in the form of small peptides of degradation originating in the receptor, have not been detected in the cell. Therefore, if there is a process of receptor proteolysis, it has to be very fast and complete (Beato 1989 Edwards et al. 2002 Kassis et al. 1983). 

Heat. In the solid state, thermal degradation starts as a slow process at around 150 °C.2 Cyclics and siloxanes (Si-O-Si characteristic IR stretch at 1,100 cm-1) are formed and the polydispersity increases.292 In solution, thermally induced degradation is slower (23 h, 190 °C for complete degradation). The rate of degradation increases with increase in temperature. 

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