Nonisothermal cure modeling

The parameters of the model are the activation energies for viscous flow (AE ) and reaction rate ( Ej ) their respective pre-exponential erms. This equation provides a predictive, analytical expression with which one can model nonisothermal cure using any appropriate time-temperature function [T(t)] one chooses, appropriate to the curing process of interest. For example, the baking of a coated substrate in an oven may be modeled by a relaxation-type heating function, with time constant (t) to take account of the thermal inertia of the substrate. (Eq. 4)... 

Nonisothermal flow of a curing model liquid in a flat slit is discussed in Refs. [88, 89] as applied to the casting of rubber stock under the conditions of airing. 

An improvement in the model predictability is expected by allowing parameters D and E in Eq. 23.130 to change with temperature during nonisothermal cure. Furthermore, both of these parameters also show some variation with the volume fraction (shear rate Ay/At). A modified comprehensive model was thus proposed as follows (Zhou and Sancaktar 2008) ... 

The basis of the method described by Hands and HorsfaU [1] consists of calculating the tanperature distribution as a function of lime first, thoi evaluating the dis-ttibution of the cure. Taking a temperature profile, a technique is described enabling the evaluation of the state of cure. When the form of the relationship between cure and temperature history is known, the basic cure parameters can be obtained from experiments in which temperature varies with time. When the relationship is not known, it is preferable to conduct experiments at various fixed temperatures in order to separate the dependence on time and temperature. An apparatus was built for measuring cure as a function of time at a constant temperature. The data obtained from this isothermal apparatus and a new mathematical model of cure was used to predict the cure distribution obtained in nonisothermal experiments. 

In order to model realistic adhesive processing, usually with a broad temperature range, nonisothermal tests usually need to be undertaken. The comprehensive isothermal chemoviscosity model, based on Eq. 23.130, can then be extended to nonisothermal temperature cure cycle through nonlinear regression analysis of nonisothermal data. 

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