Degradation mechanisms promoters

More recently, polyesters with beneficial degradation products (salicylic acid) have been produced to promote healing through enhanced regeneration of tissue [10]. Degradation mechanisms relevant to medical applications include... 

The oxidation of polymers can be represented by an autocatalytic mechanism involving the intermediate formation of hydroperoxides (Scheme 1) (B-79MIU501). The termination steps involving reactions of peroxy radicals are thought to predominate in most cases. Metal ion impurities accelerate degradation by promoting decomposition of intermediate hydroperoxides (B-79MI11502). 

It is well documented that transition metals such as chromium, copper, iron and vanadium can catalyse the degradation of polymers [132, 139, 144]. These metals promote the decomposition of hydroperoxides, which are important in the degradation mechanism of most polymers. 

Fillers may promote char magnesium hydroxide, zinc borate, antimony oxides require high loadings and can degrade mechanical and other properties. Toxicity of antimony-based retardants is a concern. Can be used with other flame retardants synergistically. 

As is shown in the burning cycle, the burning of a polymer occurs by the combustion of the volatile products emitted during the oxidative thermal degradation of the polymer. If the degradation mechanism could be altered to produce more char and less volatiles the flame retardancy of the formulation should be decreased. Many flame retardants act in this way, promoting low energy, solid-state reactions which lead to the carbonization of the polymer and a carbonaceous char on the surface. 

Within focus on the ambient part of this work the thermal deactivation, and more particular sintering as temperature induced degradation mechanism is studied. Three mechanisms for crystallite growth are known and advanced crystallite migration, atomic migration and vapor transport. These processes can in general be accelerated by promoters (i.e. water vapor, oxygen) and are usually irreversible. 

Wood fibres made the thermal degradation of LLDPE take place earlier 849787, while APP stabilised LLDPE in LLDPE-wood fibres composite these results were explained by free-radical stabilisation. APP decreased the initial temperature of thermal degradation, and promoted char formation of the composite. It was inferred that APP could catalyse esterification, dehydration and char formation of wood fibres. Scheme 33 illustrates the proposed thermal degradation mechanism of wood and LLDPE at high temperatures. 

On the basis of degradation mechanisms of hydrocarbon membranes, blocking of the aromatic ring by suitable substitution, such as fluorine atoms, can limit the HO addition reactions (Mitov et al. 2006a). The SOj groups cannot only promote proton conductivity, but can also reduces the activity of the aromatic ring toward HO addition. 

The Mg compounds as catalysts may accelerate both the / -elimination reactions in the beginning and main stages and/or the ElcB mechanism by carboxyl anions as Lewis acids and counter cations, respectively. Thereby the initial random degradation was promoted as shown by the increases in A values, consequently... 

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