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Hydroplasticization of Styrene-Acrylic Resins by DSC

Timothy D. Klots, Evan P. Kangas


This work describes glass transition temperature (Tg) measurements made on two styrene-acrylic resins and their respective sodium salts under various conditions of water infusion. The work enables quantification of the hydroplasticization behavior for the acidfunctional resins, RESIN #1 of acid value 55, and RESIN #2 of acid value 140. For instance, we find that the Tg for RESIN #1 drops from 64 °C to about 47 °C when fully hydrated, while the higher acid-containing RESIN #2 undergoes a similar drop from 65 °C to 50 °C. We interpret this in terms of the co-monomers used, which are on balance considerably more hydrophilic for RESIN #1. We also find that the amount of water actually contributing free volume, i.e., hydroplasticization, is less than the amount estimated by Barrie’s group contribution method, which has been utilized by other researchers. Our analysis leads to a substantially lower effective Tg for water of about -190 °C.

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