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Stress relaxation as a measure of chemical degradation

Stress relaxation occurs when a molecular chain carrying a load breaks. This occurs, e.g., during the oxidation of rubbers. When a stretched chain segment breaks, it returns to a relaxed state. Only stretched chains carry the load, and a load on a broken chain in a network cannot be shifted to other chains. It may be assumed that the rate at which stretched network chains are broken is proportional to the total number of chains (n) carrying the load  [Pg.785]

From the theory of rubber elasticity one can then derive in a simple way that  [Pg.785]

This expression is of the same shape as that of stress relaxation of viscoelastic materials (Chap. 13). By analogy 1/k is called the relaxation time (t). Since chemical reactions normally satisfy an Arrhenius type of equation in their temperature dependence, the variation of relaxation time with temperature may be expressed as follows  [Pg.785]

Al-Malaika S, Oxidative Degradation and Stabilisation of Polymers , Intern Mater Rev 48 (2003) 165. [Pg.786]

Conley RT (Ed), Thermal Stability of Polymers , Marcel Dekker, New York, 1970. [Pg.786]


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