Physical aging origin

Fig. 3.6 Normalized fluorescence intensity as a function of aging time of TCI-labeled PMMA 12 nm thick layers placed within a multilayer film geometry of neat PMMA layers. The multilayer films where aged at Tj = fy bulk 87 K. The substrate layer triangles) exhibited near suppression in physical aging while the free surface layer (circles) and middle layer (squares) exhibited more pronounced physical aging. Original data from Ref. [46]. Reproduced with permission from Ref. [6]...

Fig. 1. Origin of physical aging as explained from a thermodynamic point of view...

One might anticipate that, in favorable circumstances, the physical age determined by this procedure would equal the chronological age of the sample, that is, the time elapsed since the textile originated would equal the time elapsed since the Tg of the sample was exceeded. However, in determining the physical age of fibers and claiming their chronological age to be the same, one must assume that the fibers have been subjected to a fairly constant temperature between Tp and Tg and that no other conditions have erased their physical aging. 

Fig. 17 Schematic of the origin of physical aging in amorphous polymers.

Figure 1. Origin of physical aging as explained from a thermodynamic point of view. is the glass-transition temperature T is the highest secondary transition temnerature belov/ T and is the sub- i ...

Priestley, R. D., Rittigstein, P., Broadbelt, L. J., Fukao, K., and Torkelson, J. M., Evidence for the molecnlar-scale origin of the snppression of physical ageing in confined polymer fluorescence and dielectric spectroscopy studies of polymer-silica nanocomposites, /. Phys. Condens. Matter, 19, 205120-1 to 205120-12 (2007b). 

Struik [3] originally proposed a method to model physical aging through the use of a momentary creep master curve obtained from a series of short term creep tests performed at various aging times. The momentary creep master curve was then used in conjunction with the effective time theory to predict long term creep in a polymer in the presence of physical aging. 

The origin of physical ageing in an amorphous polymer. After quenching to a temperature below Tg (but above T, the temperature of the highest secondary relaxation), the volume stCM4y contracts the movement is towards the equilibrium, which is the extrapolMed V - T line for the liquid (after Struik). 

Chen et al [236] investigated the origin of the so-called annealing endotherm . The authors suggested that this endotherm was related to some relaxation effects of the polymer chain in the HS phase due to the physical aging of the sample. 

After a particular loading time, the degree of crystallization is composed of the original degree of crystallization, crystalline growth due to physical aging processes, and recrystallization due to chain cleavage. 

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