Abstract
Although carbon nanotubes (CNTs) have shown great potential for enhancing the performance of polymer matrices, their reinforcement role still needs to be further improved. Here we implement a structural modification of multi-walled CNTs (MWCNTs) to fully utilize their fascinating mechanical and electrical properties via longitudinal splitting of MWCNTs into graphitic nanoribbons (GNRs). This nanofiller design strategy is advantageous for surface functionalization, strong interface adhesion as well as boosting the interfacial contact area without losing the intrinsic graphitic structure. The obtained GNRs have planar geometry, quasi-1D structure and high-quality crystallinity, which outperforms their tubular counterparts, delivering a superior load-bearing efficiency and conductive network for realizing a synchronous improvement of the mechanical and electrical properties of a PVA-based composite. Compared to PVA/CNTs, the tensile strength, Young’s modulus and electrical conductivity of the PVA/GNR composite at a filling concentration of 3.6 vol.% approach 119.1 MPa, 5.3 GPa and 2.4 × 10−4 S m−1, with increases of 17%, 32.5% and 5.9 folds, respectively. The correlated mechanics is further rationalized by finite element analysis, the generalized shear-lag theory and the fracture mechanisms.
Highlights
Carbon nanotubes (CNTs) have long been recognized as ideal reinforcing agents for composites—typically a polymer-based composite—due to the elegant combination of mechanical, electrical and thermal properties coupling with their low density, large aspect ratio and large specific surface area (SSA)[1,2,3]
multi-walled CNTs (MWCNTs) are naturally consisted of nested graphene cylinders, where the outermost cylinder shields the internal tubes from the matrix and only the defective outermost walls can interplay with the polymer matrix and carry the load[16,17,18,19]
The reinforcement role of graphitic nanoribbons (GNRs) are compared with that of R-carbon nanotubes (CNTs) to highlight the effect of structural optimization
Summary
While CNTs are less effective at reinforcing PVA composites, splitting and unpeeling them into GNRs result in a notable improvement, owing to mainly four factors as follows: (i) a substantial retaining of graphitic structure and intrinsic physical properties; (ii) an effective utilization of the inner nanotube layers and a pronounced increase of the surface area (i.e. interfacial contact area); (iii) it is easier for polymer macromolecules to adhere and mechanically interlock to a planar nanofiller than a tubular one[19]; (iv) a stronger cohesion force with PVA matrix owing to increased interfacial contact area For randomly oriented fiber fillers in a polymer matrix, the composite modulus Ec is given by: Ec
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