Influence of Solvent Absorption on the Mechanical Behavior of SMC Laminates

Abstract

The effects of aging on sheet molding compounds (SMC) by immersion in water at 100°C, hexane at 70°C, benzene at 80°C, and engine oil at 60°C, have been investigated for two laminates with different styrene contents. Tests have been conducted under the above conditions for 9 days in order to follow the liquid uptake, and for 30 days to know the variation on the mechanical properties. The overall weight gain was found to be dependent on the chemical structure of the solvent used, and it was clearly higher in both laminates for aging treatment including a solvent able to interact with the polyester resin. Differences on solvent uptake were subsequently reflected in the mechanical behavior. The amount of solvent absorbed in the laminates made from endomaged molding compounds was clearly higher, and subsequently poorer the mechanical behavior, than that for those containing a higher content of styrene. This has been attributed to the lower crosslink density and to a higher amount of defects in the materials made from compounds with a low content of styrene. The influence of solvent desorption on the mechanical behavior has also been analysed.