Abstract
Group Interaction Modelling has been extended to predict a range of thermo-mechanical properties of diglycidyl ether of bisphenol A cured with two isomers of diaminodiphenyl sulphone. The meta-meta and para-para positions of the substituents on the phenylene rings in the curing agent cause differences in packing efficiency, reaction kinetics and conformational freedom. Experimental data in the form of dynamic mechanical, static mechanical and density measurements are acquired in order to provide validation for the model. The model has proven capable of accurately reproducing the experimental measurements to well within experimental errors in most cases. Both the experimental measurements and model predictions have highlighted a number of subtle differences in behaviour of the resins cured with the two diamine isomers. In particular, variation of the amine/epoxy ratio has revealed how the secondary phase transitions of the resins are influenced. Variation of the glass and beta transitions in amine rich, stoichiometric or epoxy rich mixtures is described in terms of the molecular motions responsible for the transitions and the underlying network structural differences between the meta and para isomers.
Highlights
The chemistry of epoxy resins is distinctive among thermosetting resins
Group Interaction Modelling has been extended to predict a range of thermo-mechanical properties of diglycidyl ether of bisphenol A cured with two isomers of diaminodiphenyl sulphone
It is worth noting that while Group Interaction Modelling (GIM) under-predicts the loss tangent between the two main transitions, it over-predicts the total loss through the glass transition, on the hot side
Summary
The chemistry of epoxy resins is distinctive among thermosetting resins. Manipulations of the chemical structure and polymerisation process allow epoxy resins to span a wide range of mechanical properties, from relatively flexible to very stiff and relatively soft to very hard. When cured with an aromatic diamine, such as diaminodiphenyl sulphone (DDS), the properties of the resultant cured epoxy resins are much sought after, including a glass transition temperature approaching 200 °C and excellent chemical resistance. DDS intended for curing epoxy resins is available as two different isomers where the substituents on the two phenylene rings are either in a meta-meta or a para-para arrangement Epoxy resins cured with these two diamine isomers differ in their properties in a relatively subtle fashion Both DGEBA and triglycidyl aminophenol (TGAP) cured with 33DDS and 44DDS show internal antiplasticisation when using the meta compared to the para amine [12,13,14]. Dynamic mechanical analysis (DMA) will measure the loss tangent profile to characterise the
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