INFLUENCE OF SOLVENT ABSORPTION ON THE MECHANICAL-BEHAVIOR OF SMC LAMINATES

The effects of aging on sheet molding compounds (SMC) by immersion in water at 100 degrees C, hexane at 70 degrees C, benzene at 80 degrees C, and engine oil at 60 degrees C, have been investigated for two lami nates 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. T he overall weight gain was found to be dependent on the chemical struc ture of the solvent used, and it was clearly higher in both laminates for aging treatment including a solvent able to interact with the poly ester resin. Differences on solvent uptake were subsequently reflected in the mechanical behavior. The amount of solvent absorbed in the lam inates made from endomaged molding compounds was clearly higher, and s ubsequently poorer the mechanical behavior, than that for those contai ning a higher content of styrene. This has been attributed to the lowe r crosslink density and to a higher amount of defects in the materials made from compounds with a low content of styrene. The influence of s olvent desorption on the mechanical behavior has also been analysed.