Glass-fiber reinforcement of in situ compatibilized polypropylene/polyethylene blends

Polypropylene and low-density polyethylene (LDPE) were melt-blended at prop ortions 75/25, 50/50, and 25/75 w/w, respectively. These blends were reinfo rced with two types of glass fibers added at an amount of 20 wt %: the E-ty pe fibers without any surface treatment and the M-type fibers, which were t reated with y-methacryloxy propyltrimethoxy silane coupling agent. Poly(pro pylene-g-maleic anhydride) with 0.8 mol % maleic anhydride content and poly (ethylene-co-vinyl alcohol) with 7.5 mot % vinyl alcohol content were added at a 50/50 w/w proportion as in situ reactive compatibilizers at an amount of 10 wt %. The thermoplastic composite materials have higher tensile stre ngth as well as impact strength compared to the unreinforced blends. The si multaneous process of the in situ blend compatibilization, along with the i ncorporation of glass fibers in the thermoplastic matrix, leads to a signif icant improvement of the mechanical properties as compared to the propertie s of the composite materials with the uncompatibilized matrix. Scanning ele ctron microscopy and micro-Raman spectroscopy have been used to study the a dhesion of the thermoplastic matrix onto the glass fibers. Significantly be tter adhesion characteristics were observed in the composites containing M- type glass fibers, with LDPE adhering the most on the fibers. This better a dhesion was reflected in the improved mechanical properties of the composit es. (C) 1999 Kluwer Academic Publishers.