Using Nitroxides to Enhance Carbon Fibre Interfacial Adhesion and As An Anchor for "Graft to" Surface Modification Strategies.

Nitroxide groups covalently grafted to carbon fibres were used as anchoring sites for TEMPO-terminated polymers (poly-n-butylacrylate and polystyrene) in a "graft to" surface modification strategy. All surface modified fibres were evaluated for their physical properties, showing that several treatments had enhanced the tensile strength and Young's modulus compared to the control fibres. Up to an 18% increase in tensile strength and 12% in Young's modulus were observed. Similarly, evaluation of interfacial shear strength in an epoxy polymer, showed improvements of up to 144% relative to the control sample. Interestingly, the polymer grafted surfaces showed smaller increases in interfacial shear strength compared to surfaces modified with a small molecule only. This counterintuitive result was attributed to incompatibility, both chemical and physical, of the grafted polymers to the surrounding epoxy matrix. Molecular dynamics simulations of the interface suggest that the diminished increase in mechanical shear strength observed for the polymer grafted surfaces may be due to the lack of exposed chain ends, whereas the small molecule grafted interface exclusively presents chain ends to the resin interface, resulting in good improvements in mechanical properties. This article is protected by copyright. All rights reserved.