Abstract
An examination has been made of the mechanical properties and swelling equilibria of cured resin sheet prepared from a range of mixed Hercosett and Primal prepolymer resin solutions. With the increase in the proportion of Primal in the resin mixture the initial modulus increases slightly to a maximum at 0.3 w/w Primal, thereafter decreasing to a low value. The stress- and strain-at-break show a large increase over the composition range up to 0.9 w/w Primal when the stress-at-break decreases sharply. Calculation of the size of the crosslinked network shows that the average molecular weight between crosslink junctions falls to a minimum at about 40% w/w Primal.
In buffer solutions of constant ionic strength a large degree of swelling is observed at low pH but this decreases rapidly in the region of pH 9. Incorporation of Primal into the resin mixture reduces the overall degree of swelling with an almost linear dependence on the weight fraction of Primal under conditions of constant pH. This arises from the increased separation of the charged cationic groups in Hercosett resin by the incorporation of Primal segments.
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