Characterization and design of interphases in glass fiber reinforced polypropylene

Bond strength between reinforcing fibers and polymer matrices can be contro lled in two ways: 1) by intensification of molecular interaction at the int erface and 2) by creation of a strong transition layer (interphase) between the components. In this paper, we consider the possibilities of controllin g interfacial strength by means of target-oriented variation of structure, thickness and strength of the interphase artificially created between the g lass fiber and the polypropylene matrix. The bond strength was measured usi ng a continuously monitored microbond test, including recording the crack l ength as a function of the load applied. The measured interfacial strengths correlated to the macromechanical properties of glass fiber reinforced pol ypropylene. The interphase design provided simultaneous increase in the ten sile strength and the impact toughness of the composites.