Aging physical of glassy polymers

Physical Aging of Glassy Polymers Effects of Subsidiary Relaxation Processes... 

Hodge, I. M. in MRSSymp. Proc. Vol. 215, Structure, Relaxation, and Physical Aging of Glassy Polymers, MRS Pittsburg, 1991,11. 

Another experimental technique that has been useful in studying physical aging of glassy polymers is positron annihilation lifetime spectroscopy... 

Research on the physical aging of glassy polymers began with the discovery by Kovacs [1] that the volume of the polyvinyl acetate (PVAC) system slowly decreased (densified) with time, when rapidly quenched from above its glass transition temperature ). This research area... 

Here J is a constant, and T2 Tg — 50 K. The above equation is not valid for T < Tg and has an apparent singularity in x as T - T2. This basically prevents us from following this line of thought in order to determine the low temperature structural relaxation and physical aging in glassy polymers. 

When the deformed T -SMPUs are cooled from T to T for shape fixing, the free volume in the amorphous region is squeezed out progressively, which is also time-dependent, similar to the physical aging in glassy polymers. Hence the shape fixing time (t ), the time for shape fixing in which the samples are constrained at Tg, can infiuence the shape fixity of the T -SMPUs. 

Hutchinson JM "Relaxation Processes and Physical Ageing", in Haward RN and Young RS (Eds) "The Physics of Glassy Polymers", Chapter 3, Chapmann and Hall, London, 2nd Ed, 1997. 

We have reviewed the recent development of a nonequilibrium statistical mechanical theory of polymeric glasses, and have provided a unified account of the structural relaxation, physical aging, and deformation kinetics of glassy polymers, compatible blends, and particulate composites. The specific conclusions are as follows ... 

Rueda et al. (1995), have followed the physical ageing of another glassy polymer. They investigated the variation in microhardness of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) stored in an ambient atmosphere for different times and after annealing at different temperatures below Tg for different periods of time. This material has stiffer molecules than PET due to the presence of a naphthalene ring instead of the benzene ring in the backbone chain. 

Huang, Y, and Paul, D. R., Effect of temperature on physical aging of thin glassy polymer films. Macromolecules, 38, 10148-10154 (2005). 

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