Interfacial engineered design of upcycled graphene and hemp fiber reinforced polypropylene compounds as an injection grade for overmoulding process with bio-based prepregs

Abstract

The design of lightweight composite structures is a principal keystone in improving part performance by reducing adverse environmental impacts and adopting energy-efficient manufacturing technologies. This study replaced long glass fiber reinforced homoPP compounds as an injection grade with short hemp fiber reinforced homopolymer polypropylene (homoPP) by incorporating graphene nanoplatelets (GNP) produced from the source of recycled carbon black coming from pyrolysis of waste tires by providing 15% lightweighting. With new compound formulation by adjusting the amounts of compatibilizer and GNP, injection moulding process was integrated with overmoulding process by using bio-based UD prepregs to enhance the adhesion of injected part and interfacial interaction by decreasing the stress concentrations in the structure. This novel hybrid composite design having 40% hemp fiber, 1.0wt% GNP and 2.7wt% compatibilizer provided to improve flexural modulus and strength by 169% and 67.9%, respectively, compared to neat homoPP. For overmoulding process, bio-based natural fibers reinforced UD tapes were used as an insert and combined with injected hemp fiber reinforced composites with the enhancement of 211% and 93.6% in tensile modulus and strength compared to neat homoPP. This work achieved to convert conventional composite structures into recyclable and sustainable thermoplastic composites having multi-scale reinforcements with tailorable functionality.