Add time:08/23/2019         Source:sciencedirect.com

Selective reduction of hydrogen bonds of a phenoxy resin gave samples particularly suitable to investigate specific interactions in associative polymers. The glass transition temperature decreased when reducing hydrogen bonds, but dielectric results indicated that α and β relaxations are rather affected by steric hindrances (bulky groups). A model accounting for the combined effect of entanglements and secondary interactions on viscosity, which can be generalised for other associative polymers, is proposed and hydrogen bonds/entanglements rate is determined. Dynamic viscoelastic results at T = 170 °C and T - Tg = 80 °C, showed that hydrogen bonds did not constitute a network and were weakened by temperature. The non-linear viscoelastic parameter Q0 decreased as the amount of hydrogen bonds was reduced. LAOS (Large Amplitude Oscillatory Shear) experiments constitute a new rheological tool to investigate associative polymers. Strain hardening in extensional flow was probed to be a consequence of the long relaxation times associated to hydrogen bonds and obtained from viscoelastic data.

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