Processing and properties of long recycled-carbon-fibre reinforced polypropylene

Recycled carbon fibres have been employed as a reinforcement material for the synthesis of polypropylene-based thermoplastic matrix composites with different fibre/resin ratios (10, 20 and 30%) by means of injection moulding. A thorough study of their mechanical properties including tensile, impact and bending tests, as well as fibre distribution and orientation and chemical behaviour was conducted. The stiffness and strength of the composites increased linearly with the fibre fraction in a ratio of 180 and 0.9 MPa/% V-f respectively. The distribution and alignment of the fibres in the injection flow contributed to the improvement of the mechanical behaviour of the composite. In addition, changes in the fibre orientation were found along the injected sample, which emphasised the importance of temperature control during injection on the alignment of the fibres. However, even though the addition of a coupling agent improved the fibre/matrix adhesion, the unremarkable impact results reveal that future efforts in long recycled-carbon-fibre reinforced thermoplastic composites should be directed to enhance interface performance.