File(s) under permanent embargo

Reaction kinetics and phase transformations during cure of a thermoplastic-modified epoxy thermoset

journal contribution
posted on 05.01.2007, 00:00 authored by Russell VarleyRussell Varley
A comprehensive thermal and rheological characterisation of a commercially important aerospace resin system modified with a thermoplastic toughener is presented here. The primary focus has been the understanding of how the cure kinetics and mechanism relate to other processes such as phase separation during cure. Differential scanning calorimetry has shown that thermoplastic modification does not affect the cure mechanism significantly and that the process was dominated by an autocatalytic process up to vitrification after which diffusion-controlled processes dominate regardless of thermoplastic concentration. Thermoplastic addition at 10 wt.-% PEI was found to increase the final cure conversion compared with the neat resin and inhibit the onset of diffusion control below a cure temperature of 160°C. At 20 wt.-% PEI concentration the final conversion and the onset of diffusion control were similar until 150°C, after which they displayed lower values than the neat resin. Rheological analysis showed that the phase separation process could be followed conveniently through the changes in viscosity and exhibited effects consistent with expected variations in morphology. The 10 wt.-% PEI system displayed abrupt increases in viscosities which were indicative of a dispersed particulate morphology, while the 20 wt.-% PEI system displayed more complex behaviour consistent with a phase-inverted or co-continuous structure. The gelation process was shown to obey a power law model although the local environment or morphology of the reactive epoxide group at higher PEI concentrations was shown to affect the fit to the model.

History

Journal

Macromolecular materials and engineering

Volume

292

Issue

1

Pagination

46 - 61

Publisher

Wiley

Location

London, Eng.

ISSN

1438-7492

eISSN

1439-2054

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2007, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim