Stress enhanced polymer reactions

A unique chemiluminescence photon-counting system, designed specifically for measurement of stress-enhanced polymer reactions, was used for the studies described here. This system Includes a miniature tensile stress device, a controlled environment chamber and a luminescence detection system and associated optics Integrated Into a single unit. 

In an overwhelming majority of cases, heated polymers decompose into combustible gaseous products. The latter diffuse into the oxidative environment, mix and react with oxygen. Therefore, the self-enhancing exothermal reaction responsible for the heat generation and initiation of polymer combustion is in most cases a homogeneous gas phase reaction In order to stress this particular feature of the reactions between... 

In semi-cristalline polymers, rate-enhancement under stress has been frequently observed, e.g. in UV-photooxidation of Kapron, natural silk [80], polycaprolactam and polyethylene terephthalate [81]. Quantitative interpretation is, however, difficult in these systems although the overall rate is determined by the level of applied stress, other stress-dependent factors like the rate of oxygen diffusion or change in polymer morphology could occur concurrently and supersede the elementary molecular steps [82, 83], Similar experiments in the fluid state showed unequivocally that flow-induced stresses can accelerate several types of reactions, the best studied being the hydrolysis of DNA [84] and of polyacrylamide [85]. In these examples, hydrolysis involves breaking of the ester O —PO and the amide N —CO bonds. The tensile stress stretches the chain, and therefore, facilitates the... 

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