Hardening kinetics of clear and pigmented water epoxy systems studied on the basis of the variations of the viscoelastic moduli

Autori: G. Torriano, S. Pricl
Presentato al: Southern Europe Conference on Rheology
Anno: 1999
Volume: 1
Issue: Unico
Casa Editrice: SIR-Cuen Napoli
Lingua: English


Abstract
The present trend towards the limitation, or the elimination, of VOC (Volatile Organic Compounds) has urged epoxy resin manufacturers to develop solvent free epoxy systems, in which a low-molecular weight epoxy resin is reacted with a water emulsion of special hardeners to give a reacting system, that is still a water emulsion and can be further diluted with water [Wicks et al., 1992].
The subject was already investigated by the Authors, using a rate-controlled rheometer [Torriano et al., 1997]. To get trustful data with this apparatus the minimum applicable deformation under oscillatory flow conditions was 3%. Hence, during the progress of the hardening reaction the rheometer operated mostly outside the of linear viscosity range. Notwithstanding, a series of data useful for practical application techniques were obtained in the study of clear systems.
The current work presents the results of a study performed with a stress-controlled rheometer, that allows operating at very low deformations and, therefore, within the linear field during a consistent part of the hardening reaction. Tests of both time and frequency sweep were carried out. The study was performed on clear systems and on systems pigmented with TiO2, at different levels of pigment content.


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