Multifunctional performance enhancement of polypropylene nanocomposites via dual filler hybridization: Mechanical, viscoelastic, creep, aging, and repairability analysis

The study investigates the collaborative effect of amine-functionalized graphene (GN) and tungsten carbide (WC) nanofillers on the static mechanical and viscoelastic properties of polypropylene (PP). Comprehensive analysis showed that the sample with 1 wt% of GN and 0.5 wt% of WC (P/0.5W/1G) exhibited superior mechanical properties. The elastic modulus of P/0.5W/1G showed an increase of 193% compared with PP, owing to the pinning and bridging effect of the dual nanofillers. Various theoretical models were employed to predict the elastic modulus of the composite system, Hui-Shi model demonstrated close proximity with experimental values, as the model is best suited for 2D nanofillers. The sample exhibited a 176% increase in critical stress intensity factor compared to neat PP. The fractographs of P/0.5W/1G indicated semi-brittle fracture, since the inclusion of WC and GN impeded the crack growth. The hydrothermal aging increased the tensile modulus of the samples due to the annealing effect. After repairing samples by hot plate welding, P/0.5W/1G showed 230% enhancement in Young's modulus compared to PP due to the effective entanglement of nanofillers and polymer chains at the weld interface. The creep analysis revealed that P/0.5W/1G exhibited a lower strain rate, and rheological analysis showed shear thinning behaviour at higher viscosity. The formation of an effective dual network by 0D/2D nanofillers in PP, yielded a confined structure that limits the chain movement, particularly at higher service temperatures.