Mechano-chemical reaction chain

Fig. 8.17. Mechano-chemical reaction chain after Zakrevskii and Zhiurkov (17, 20, 551 (a) stress-induced chain scission, (b) formation of chain-end radicals, (c) radical reaction leading to main-chain radicals, (d) scission of radicalized chains, (e) formation of a submicrocrack by repetition of the steps (c) and (d) chain-end radical e.g. -CH2-CH2, x main-chain radical e.g. -CH2-CH-CH2-, stable end groups e.g. -CH2-CH3.

Fig. 8.18. Scheme of energy levels of steps fl-c in the mechano-chemical reaction chain. 

The data from Table 3.111 also reveals that coneomitantly with the decrease of temperature bellow 0 °C, the energetic barrier of mechano-chemical reactions release increases due the decrease of chains mobility and the corresponding increase of mechanical resistance [906]. In addition, a slightly increase of even for temperatures higher then 40 °C was observed. This finding was ascribed to an effect of thermal plasticization which firstly occurs by the splitting of the secondary bonds, phenomenon that imposes higher ap-... 

It has more recently been shown that there are advantages in separating the chemical reaction of antioxidants with solid polymers from the vulcanization process. It has long been recognized (32) that mechano-scission of polymer chains during processing or polymers gives rise to free radicals which can initiate radical chain reactions (32). Block copolymers can be synthesized in this way, reaction 5 ... 

Flow may also cause mechano-chemical degradation that generates reactive components, viz., radicals, peroxides, acids, etc. Trans-esteriflcation, trans-amidation and ester-amide exchange reactions during processing are well documented (their rate depends on the total interphasial area that in turn depends on flow). These reactions may be responsible for the formation of compatibilizers that increase the interphasial area, affect the phase equilibria, and the regularity of the main chain, thus modify the degree of dispersion, blend s crystallinity, hence performance. 

In conclusion, the mechano-chemical act of chemical bonds splitting on the ternary copolymer main chains stays on the basis of the mechanical resistance decay in the case of MELANA fibres supposed to sonic fatigue. The generated mechano-radicals initiate o chain of reactions that in time affects the supramolecular-morpho-logical structure, reflected by the decrease of mechanical properties [830-951]. 

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