Mechanical properties and viscoelastic behavior of basalt fiber-reinforcedpolypropylene

In the present article, a series of commercial-grade polypropylenes (PP) fi lled with different contents of short basalt fibers were studied. This comp osite material presented deterioration of both mechanical characteristics, for example, stress and strain at yield with increasing of the fiber conten t. On the other hand, the impact strength was fourfold higher than that of unfilled PP. A poor adhesion between the PP matrix and the basalt fibers wa s detected. This is why interfacial interactions were promoted by the addin g of poly(propylene-g-maleic anhydride) (PP-g-MA). It was observed that the tensile properties of the obtained materials and their impact strengths in creased significantly with increasing of the amount of PP-g-MA in the blend . The adhesion improvement was confirmed by scanning electron microscopy as well. Fourier transform infrared spectroscopy was applied to assess if any chemical interactions in the system PP/PP-g-MA/basalt fibers exist. Dynami c mechanical thermal analysis data showed an increase of the storage modulu s with increasing fiber content. The conclusion was made that the modificat ion of the PP matrix led to a higher stiffness but its value remained const ant, irrespective of the PP-g-MA content. With increasing fiber content, da mping in the beta-region decreased, but increase of the coupling agent cont ent restored its value back to that of PP. The loss modulus spectra present ed a strong influence of fiber content on the alpha-relaxation process of P P. The position of the peaks of the above-mentioned relaxation processes ar e discussed as well. (C) 1999 John Wiley & Sons, Inc.