Isothermal time-temperature transformation cure

Figure 3. ATS time-temperature-transformation diagram for isothermal cures in N2.

Figure 2.8. A time-temperature-transformation (TTT) isothermal cure diagram for a thermosetting system. Adapted from Figure 1 (GilUiam, 1986).

Fig. 3. Generalized time-temperature-transformation (TTT) cure diagram. A plot of the times to gelation and vitrification during isothermal cure versus temperature delineates the regions of four distinct states of matter liquid, gelled rubber, gelled glass, and ungelled glass. From Ref. 12.

At hi temperatures thermal degradation becomes important, and may prevent full cure from being achieved Two degradation events have been noted in relation to the TTT diagram devitrification followed by elastomer formation and vitrification followed by char formation. The devitrification event corresponds to a decrease in Tg from above to below the isothermal cure temperature the time to this event may be considered to be the lifetime of the material since it marks the limit in time for the material to support a substantial load. The second event is an elastomer-to-glass transformation, accompanied by an increase in Tg and rigidity, and is presumably due to the onset of char formation... 

Fig. 1. Transformation diagram for 1 cured with sulfanilamide showing changes in morphology as a function of the cure time. This particular diagram shows the time at which phase transformations occur when the sample is cured isothermally at a given temperature. I, isotropic LC, liquid crystalline K, crystalline. Reprinted from Ref. 70, Copyright (1994), with permission from Elsevier Science.

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