Mechanical properties of extruded glass fiber reinforced thermoplastic polyolefin composites

Engineered structural materials are required to feature a combination of deformability (ductility) and strength to be considered damage-tolerant for safety-critical applications. These two mechanical properties, however, tend to be mutually exclusive, encouraging optimization of the trade-off between strength and toughness. In this report, an elastomer and a glass fiber were incorporated into a blend of two grades of polypropylene (PP) to improve matrix toughness through both intrinsic and extrinsic toughening mechanisms. This study investigates the impact resistance (at 23°C and −30°C), and strength, stiffness, deformability, and processability of extruded compatibilized glass fiber reinforced thermoplastic polyolefin (TPO) composites at 23°C. For the hybrid composites contribution of different toughening mechanisms in attainment of the final impact strength is governed by the testing temperature and processing (extruder screw) speed. The intrinsic toughening mechanism induced by the presence of the ethylene α-olefin copolymer is suppressed by the introduction of glass fiber at 23°C, irrespective of screw speed and screw configuration design. The heat distortion temperature (HDT), flexural modulus, and tensile strength exhibit a marked improvement by glass fiber inclusion at 23°C. By evaluating the performance of the composites at −30°C, it was observed that the impact energy of the elastomer modified hybrid composites may be enhanced in the same manner as the glass fibers toughen the brittle unmodified PP matrix. It was noted that contrary to the tensile properties at break, the yield behavior of the composites containing fibers, severely shortened, is independent of the presence of the fibers at 23°C.