Chemical anchorage of polypropylene onto glass fibers: Effect on adhesion and mechanical properties of their composites

The objective of this work is to study the influence of the polypropylene (PP) chains, chemically anchored onto glass fibers (GFs), over the adhesion and consequently on mechanical properties of the PP/GF composites. The anchoring of glass fibers to the polymer matrix was achieved by direct metallocenic polymerization of propylene onto the fibers surface, previously treated with methylaluminoxane. With this method, homogeneous fiber coverage is obtained, drastically changing the fiber surface activity, from hydrophilic to hydrophobic.Sandwich PP/GF/PP specimens were prepared including pre-straightened and uniaxially oriented fibers. The yield and break elongation as well as the toughness of composites having polymerized fibers were notably improved indicating clearly a much greater PP/GF adhesion. These results were corroborated by electronic microscopy analysis on the specimens after tensile tests and interpreted in terms of a phenomenological analysis of the interaction between polymerized fibers and polymer.