Effects of glass fiber surface condition on the dielectric property of short glass fiber reinforced PA-6/PP composites

Dielectric properties of short glass fiber reinforced PA-6/PP composites under both dry and wet conditions were investigated. The composites were prepared with a Haake-90 mixer using different short glass fibers, which were surface-modified respectively with three kinds of silane solution. It was found that the fiber surface condition influences significantly the glass fiber-resin matrix interfacial bond, which in turn determines the dielectric properties of the composites. The short glass fiber/PA-6/PP composite containing fibers pre-treated with an acid aqueous solution of two silane coupling agent exhibits the best stability in dielectric properties under wet conditions. It is considered that the observation is a direct result of the strong interfacial bond due to the proper selection of a silane coupling agent and its acid-water condition used in the fiber pre-treatment. The mechanism of the change of the dielectric properties of the composites under dry and wet conditions is proposed based on the moisture absorption through capillaries of the materials.