Recyclability of unidirectional reinforced pultruded thermoplastic profiles into composite laminates

The recyclability of fibre reinforced composites is innovative approach to deal with the end -of -life of these products without sending them to the landfill. This is crucial and controls the applicability of these superior materials. The use of thermoplastic matrix instead of thermoset ones in the fibre reinforced composites makes the matrix thermoformability a viable method of recycling, which overcomes a significant issue that ceases the spread of these materials. This study investigates the changes in properties of pultruded thermoplastic fibre reinforced composites recycled by thermoforming method. Five composite plates reinforced with unidirectional glass fibres were made by compression molding from materials obtained after 1 to 5 thermoforming/recycling rounds. In the first recycling round, the plates were produced out of pultruded glass fiber/polypropylene o6 mm rods. Successive recycling rounds consisted of cutting the previously produced plate into 10 mm wide strips along reinforcing fibers and fabricating of a new unidirectional plate using those strips. The mechanical test results show that plate thermoformed from pultruded rods has a flexural strength 31% higher than the virgin pultruded thermoplastic profile. The increase in the recycling rounds number from 1 to 5 resulted in 30 % and 33 % reduction in flexural strength and modulus, respectively, and 19 % and 16 % reduction in compressive strength and modulus, respectively. This is attributed to the increase in the fibre misalignment and the increase in porosity of material noticed after each recycling round. Although the mechanical properties of the samples deteriorated, there was no evidence of chemical degradation based on the IR spectroscopy data. This study shows that recycling of thermoplastic composites is feasible considering the reforming and the heating conditions.