Contrôle des résines polyester insaturées pour SMC

Test de la réactivité des magnésies lors du mûrissement des résines

Control of unsaturated polyester resins for SMC

¹ Ecole Supérieure du Cuir et des Peintures, Encres et Adhésifs.
² Laboratoire des matériaux plastiques et biomatériaux (UA CNRS n° 507), Université Claude Bernard Lyon I

Abstract

A sum-up of a control test by potentiometric titration

It is important to know and control the thickening process of unsaturated polyester resins, in order to realize prepregs with the SMC (Sheet Molding Compounds) process. Magnesium oxide MgO is the mostly used thickening agent, but the reactions mecanisms are still not fully understood. We characterized some magnesium oxides of various macro and micro structures.

The main reactivity parameters of MgO were established : surface (aspect), size and distribution of particles, carbonatation and hydratation, previous impastiny. We found that an acido-basic reaction seems to be a good modelisation of the reaction’s first step, which leads to a gel formation. In consequence, an easy and quick test of acid attack is suggested for the estimation of the thickening power of MgO.