Cure modelling and monitoring of epoxy/amine resin systems

摘要

Thermoanalytical techniques and dielectric analysis were used in this study to describeand characterise the cure processes occurring during the isothermal and dynamic curesof four epoxy/amine resin systems.The complexity of the cure reactions was illustrated by results from DSC and FTIRexperiments and was attributed to the variety of chemical reactions between the epoxyand the amine groups. Several phenomenological and mechanistic cure kinetics modelswere constructed, based on the cure reaction mechanisms, in order to simulate thedegree of conversion during the cure. A one-to-one relationship was establishedbetween the degree of cure and the glass transition temperature of the curing resin,which was finther used in the construction of chemoviscosity models and in asimulation of the viscosity advancement during the cure.A number of mathematical techniques were utilised to evaluate the parametersinvolved in all the models, varying from simple linear regression methods to complexnon-linear least squared estimation procedures.An in-situ dielectric monitoring technique was used in combination with the abovementioned chemorheological models, to investigate the feasibility of a quantitativecorrelation between the changes in the dielectric signal, the cure advancement and themajor physical transformations, namely gelation and vitrification. The imaginaryimpedance response of the curing resin, as measured by the dielectric technique,showed good agreement with the degree of conversion, depicting all the crucialcharacteristics of the curing mechanism, such as autocatalysis and diflusion. Theendset of the cure reaction was also identified from the endset of the conductivitychanges and correlated to the vitrification time.The analytical chemorheological models developed in this study to describe the cureprocesses for some epoxy/amine resin systems, along with the dielectric monitoringtechnique used, suggest that a real-time link between the above mentioned models andthe cure monitoring technique can be achieved. This would greatly enhance thepredictive capability of the technique and form the basis of a future feedback-loopcontrol system.