Development of Long Glass Fiber Reinforced Polypropylene Composites: Mechanical and Morphological Characteristics

Innovative polymers and composites are broadening the range of applications and commercial production of thermoplastics. Long fiber-reinforced thermoplastic (LFRT) composite contains glass fiber, which has an aspect ratio greater than 100. This study describes the development of long fiber-reinforced polypropylene (LFRP) composites and the effect of fiber length, fiber content, and compatibilizer content on mechanical and morphological properties. LFRP pellets of different sizes were prepared by extrusion process using a specially designed impregnation die and these pellets were injection molded to develop LFRP composites. Maleic-anhydride grafted polypropylene (MA-g-PP) was chosen as a compatibilizer and its content was optimized. The addition of MA-g-PP enhanced the mechanical properties of LFRP composites, particularly the impact strength. Interfacial shear strength between glass fiber and polypropylene with and without the addition of compatibilizer was also studied. Tensile, flexural, and impact properties improved with increase in fiber length and fiber content. Morphological studies were also carried out to find the fiber length distribution in the injection molded specimens. Average fiber length in the injection-molded sample from 9 mm long pellets remained comparatively higher than that in case of samples from 3, 6, and 12 mm long pellets. The study shows that in a standard injection-molding machine, 9 mm long pellets provide improved performance properties.