Oxygen, damage during polymer

Alkyl radicals (c) may either combine or disproportionate, and so cause no further immediate damage, or, during irradiation in air, may combine with dissolved oxygen in the polymer to give peroxy radicals R02 [88, 191,193]. 

In the end of this section the authors should like to add one thing that this photoreaction of the mechano-radical is considered a fundamental research of photo-degradation of a polymeric material in practical uses. A polymer suffers eaaly and very often from mechanical damages, sudi as scratch, during a practiral use. A mechanical scratch may produce mechano-radicals, and the reaction of the mediano-radicals with oxygens forms the peroxy-radkals, from which the chain sessions are induced by l t with high efficiency and in the way of a chain-reaction. 

The development of membrane lungs was prompted by a need for an efficient device that could be used longer and that would damage the blood less than the direct blood-gas contact oxygenators. The evolution of the membrane lung during the last twenty-five years was dependent on advances made in permselective and microporous polymers with the required characteristics for the critical membrane portion of the device. 

Only very few polymers (thermoplastics, duroplastics, elastomers, converted natural products) can be processed and used as synthesized. The effects of heat and oxygen would damage them before they could even be processed. Then there are the environmental conditions applied during storage and use of the semifinished... 

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