Effect of nanoclays on the mechanical properties and durability of novolac phenolic resin/woven glass fiber composite at various chemical environments

Both natural montmorilonite (CN) and organically modified montmorilonite (CB) improved significantly the mechanical performance of novolac phenolic resin (PF)/woven glass-fiber (GF) composites due to their nanodispersion and good interfacial interaction with the matrix. It was revealed that the incorporation of 2.5 wt% of the clays enhances the elastic modulus up to 38% for CN and 43% for CB. Aging of PF/GF composites at various aqueous solutions, i.e. water, brine and acidic environments, increased stiffness of the composite (∼100-250% increase in elastic modulus) due to possible secondary crosslinking caused by water molecules and hydroxyl groups of PF resin. However, aging led to the reduction of strength caused by the matrix degradation due to hydrolysis and interfacial debonding. It was found that both clays diminished durability of PF/GF composites probably due to their hydrophilic nature enhancing water absorption.