Sequential aging theory

However, an alternative explanation may be found in the Sequential Aging Theory proposed by Chai and McCmm [1980]. The authors postulated that at a given T and t, the viscoelastic elements with relaxation times equivalent to t will be aging, but that elements with x < t will already have reached equilibrium and those with X > t will not yet have begun to move towards equilibrium. Thus in the PVME/PS case the more flexible PVME, which will also be closer to its own Tg, will possess more elements with shorter X than the PS. Consequently the PVME relaxation spectram will tend to move more rapidly towards equilibrium than the PS and so would age more rapidly. This idea will require further testing. 

McCrum, N. G., The interpretation of physical ageing in creep and DMTA from sequential ageing theory, Plast. Rubber Compounds Proc. Appl., 18, 181-191 (1992). 

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