The reinforcement mechanics of viscose-fiber-reinforced polypropylene (PP) composites were studied. The effect of the coupling agent, maleated polypropylene (MAPP), was of special interest. The fibers, coupling agent, and PP were extruded and injection-molded. The composition, mechanical properties, fracture morphology, and dispersion of the composites were examined. Thermogravimetric analysis showed that the fiber content in the tensile specimens varied slightly with the sample location; however, the differences in the values were within 1.0%. Scanning electron microscopy images of the fracture surfaces of the composites showed that the surfaces of the composites without MAPP were covered with fibers pulled out from the matrix. A lack of adhesion further appeared as a cracked matrix-fiber interface. A new scanning thermal microscopy method, microthermal analysis, was used to study the dispersion of the fibers in the composites. Local thermal analyses gave further information about the location of the fibers. (C) 2003 Wiley Periodicals, Inc.