Aging kinetics

The expanded set of 34 lumps necessary to define the reforming process is shown in Table VIII. Note that this 34-lump set is sufficient for both start-of-cycle and aging kinetics. 

Figure 23 demonstrates that aging kinetics slow down as the temperature increment (T — Ta) increases, i.e., the recovery process is a thermally stimulated phenomenon which requires segmental mobility of the polymer in its glassy state. 

Aurhek, N., Thiermann, H., Szinicz, L., Eyer, P., Worek, F. (2006). Analysis of inhihition, reactivation and aging kinetics of highly toxic OP compounds with human and pig cholinesterase. Toxicology 224 91-9. 

Worek, F., Diepold, C., Eyer, P. (1999b). Dimethylphosphoryl-inhibited human cholinesterases inhibition, reactivation, and aging kinetics. Arch. Toxicol. 73 7-14. 

Audouin, L. Langlois, V. Verdu De Bruijn, J.C.M. Review role of oxygen in polymer ageing kinetic and mechanical aspects. J. Mater. Sci. 1994, 29, 569-583. 

The interaction of water, temperature and seed quality factors on seed aging kinetics can be examined through a simple model that describes kinetics of... 

Worek, F., Thieimann, H., and Szinicz, L. 2004. Reactivation and aging kinetics of human acetylcholinesterase inhibited by organophosphonylcholines. Archives of Toxicology, 78 212-217. 

Worek F, Eyer P and Szinicz L (1998). Inhibition, reactivation and aging kinetics of cyclohexylmethylphosphonofluoridate-inhibited human cholinesterase. Arch Toxicol, 72, 580-587. 

The methods are at hand to distinguish which mechanism is responsible for the increase in EEW during isothermal aging. The epoxide homopolymerization should have a second order dependence on epoxide concentration and no dependence on secondary alcohol concentration, whereas the epoxide-alcohol reaction should display a first order dependence on both epoxide and secondary alcohol concentration. Therefore, a study of isothermal aging kinetics versus EEW of the epoxy resin will distinguish these mechanisms. 

An homologous series of epoxy resins with various EEWs was synthesized by standard advancement techniques and subsequently esterified with 15 wt% 1300X13. Isothermal aging kinetics were followed at 175C. Aliquots of resin were withdrawn hourly, rapidly cooled to room temperature, and titrated for EEW. No precautions were taken to exclude air during the isothermal aging. Table Xll summarizes the formulations, reactive moiety equivalent weights, and kinetic calculations for the epoxide-alcohol addition reaction and the epoxide homopolymerization reaction. 

Isothermal Aging Kinetics for 15 wt% 1300X13 Modified Epoxy... 

Beckmann, J., McKenna, G. B., Landes, B. G., Bank, D. H., and Bubeck, R. A., Physical aging kinetics of syndiotactic polystyrene as determined from creep behavior, Polym. Eng. ScL, 37,1459-1468 (1997). 

Curro et al. [1981] followed a similar procedure in studies of the aging kinetics of poly(methyl methacrylate) (PMMA). For predicting the shift factors of aging experiments at 23°C, the authors computed from PVT the free-volume function, h = h P, V), and then substituted these into Doolittle s equation (6.63). The resulting prediction agreed with the experimental values, contrasting with the inadequacy of the WLF relation. Next, the polymer aging process was modeled as a diffusion of free volume [Curro et al., 1982]. 

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