Mechanical properties of recycled plastic fibres for reinforcing concrete

With the increase in the general awareness of waste management, recycled plastic fibre reinforced concrete has attracted widespread attention. However, the production of recycled plastic with sufficient mechanical properties is still a major challenge. This research focuses on improving the tensile strength and Young's modulus of recycled polypropylene (PP) fibres produced through a hot drawing process. The mechanical properties of the mixture of 50 % recycled PP and 50 % virgin PP were compared with 100 % virgin and 100 % recycled plastic fibres. The 100 % recycled PP fibres achieved tensile strength of 310 MPa and Young's modulus of 620 MPa. The combination of recycled (50 %) and virgin PP (50 %) showed significant improvement in Young's modulus (800 MPa). Tensile strength was found to increase to 360 MPa. The crystalline structure and crystallinity of the PP fibres were studied to explore the ef ects of hot drawing process on the mechanical properties of the PP fibres. The hot drawing process increased the crystallinity from around 50 % to over 80 %. Both α- and β- form crystals were found in all the plastic fibres, but recycled PP fibre contained more β- form crystals than the virgin PP fibre, resulting in lower Young's modulus.