MWCNTs/P(St-co-GMA) Composite Nanofibers of Engineered Interface Chemistry for Epoxy Matrix Nanocomposites

Abstract

Strengthened nanofiber-reinforced epoxy matrix composites are demonstrated by engineering composite electrospun fibers of multi-walled carbon nanotubes (MWCNTs) and reactive P(St-co-GMA). MWCNTs are incorporated into surfacemodified, reactive P(St-co-GMA) nanofibers by electrospinning; functionalization of these MWCNT/P(St-co-GMA) composite nanofibers with epoxide moieties facilitates bonding at the interface of the cross-linked fibers and the epoxy matrix, effectively reinforcing and toughening the epoxy resin. Rheological properties are determined and thermodynamic stabilization is demonstrated for MWCNTs in the P(St-co-GMA)-DMF polymer solution. Homogeneity and uniformity of the fiber formation within the electrospun mats are achieved at polymer concentration of 30 wt %. Results show that the MWCNT fraction decreases the polymer solution viscosity, yielding a narrower fiber diameter. The fiber diameter drops from an average of 630 nm to 460 nm, as the MWCNTs wt fraction (1, 1.5, and 2%) is increased. The electrospun nanofibers of the MWCNTs/P(St-co-GMA) composite are also embedded into an epoxy resin to investigate their reinforcing abilities. A significant increase in the mechanical response is observed, up to >20% in flexural modulus, when compared to neat epoxy, despite a very low composite fiber weight fraction (at about 0.2% by a single-layer fibrous mat). The increase is attributed to the combined effect of the two factors the inherent strength of the well-dispersed MWCNTs and the surface chemistry of the electrospun fibers that have been modified with epoxide to enable cross-linking between the polymer matrix and the nanofibers. KEYWORDS: electrospinning, composite nanofibers, surface modification, cross-linked interface, carbon nanotubes ■ INTRODUCTIONSince the discovery of carbon nanotubes (CNTs), 1 they have attracted a lot of attention in materials and applied research because of their unique and fascinating structure and properties. 2−6 One specific application is the use of CNTs in polymer fibers to impart dramatically enhanced strength and toughness in the fibers. 7−11 The incorporation of CNTs into the polymeric media via electrospinning, has been demonstrated to significantly improve the mechanical properties of the electrospun composite fibers. 7,12−14 It is recognized that this technique is an ideal route to translate the unique superior properties of CNTs to mesoand macroscale structures 7 by first embedding the CNTs in the fibers and then incorporating of these composite fibers into a polymer-matrix, successively.Electrospinning is widely used process for forming ultrafine fibers by electrostatically induced self-assembly. 15 One of the challenges of the electrospinning technique is controlling material and process parameters that affect the various properties and characteristics, such as overall strength, fiber diameter, and morphology. 16 Electrospun polymeric nanofibers have recently been explored for their reinforcing ability in composites. 17−22 They were utilized to spec...

Multi-scale modelling of carbon nanotube reinforced crosslinked interfaces

“…However, the effect of CNTs or other nanofillers on crosslinking has been less studied. Our experimental studies 64 and observations have shown that incorporation of CNTs considerably decreases crosslinking density in epoxy. This effect may be seen by monitoring the reduced glass transition temperature of composites (Tg) 64 or by directly determining crosslinking density by the Soxhlet extraction technique.…”

“…Our experimental studies 64 and observations have shown that incorporation of CNTs considerably decreases crosslinking density in epoxy. This effect may be seen by monitoring the reduced glass transition temperature of composites (Tg) 64 or by directly determining crosslinking density by the Soxhlet extraction technique. The lack of attractive interactions 10 at the interface can lead to depression of Tg relative to bulk values 65 .…”

Molecular basis for solvent dependent morphologies observed on electrosprayed surfaces

“…17,[43][44][45] If the solution is at a semi-dilute unentangled concentration regime, this jet disintegrates into micron sized droplets. The formation of super hydrophobic surfaces is possible once these droplets of a hydrophobic polymer dry out on a film.…”

The stability and dispersion of carbon nanotube-polymer solutions: A molecular dynamics study

“…In literature, several polymer matrices are reported for CNTs reinforced with nanofiber/fibers that benefit from CNTs-polymer attractive interactions [35][36][37]. For instance, recent experimental observations indicated that P(St-co-GMA) containing aromatic rings have attractive π-π interaction with the graphitic side walls of CNTs [38],which is called "π -stacking". This interaction leads to CNTs bundles which are major obstacles to their processing [39].…”

“…Polymers containing aromatic rings are able to wrap CNTs via π-π stacking and van der Waals interactions between the polymer chain and nanotube surface [51]. Ozden-Yenigun et al used surface reactive copolymer (P(St-co-GMA)) and successfully produced CNTs reinforced electrospun nanofibers without any modification, they reported the enhancement in flexural strength (15%) and flexural modulus (20%) within the incorporation of CNTs into epoxy resin [38]. Charitidis et al used PVB as matrix in CNTs integrated nanocomposites to enhance electrical and thermal properties [52,53].…”