Nanocomposite Fiber Systems Processed from Fluorinated Single-Walled Carbon Nanotubes and a Polypropylene Matrix

Abstract

Processing composites of carbon nanotubes into nanotube continuous fibers (NCFs) is an effective way of manipulating the anisotropic properties of the single-walled carbon nanotubes (SWNTs) as it becomes less difficult to transform the SWNTs into an aligned configuration when they are confined in a small diameter fiber. This helps to take fuller advantage of the high mechanical properties of the SWNT materials in the axial direction. However, in creating nanocomposite fiber systems, the issues of dispersion and nanotube−matrix interaction and adhesion become of utmost importance when improved mechanical properties are anticipated. In addressing these issues in this work it has been found that sidewall chemical functionalization can be an effective tool for improving both the dispersion and interaction between the nanotube and the matrix. This work evaluates the effect of sidewall functional groups on fluorinated single-walled carbon nanotubes (F-SWNTs) as a precursor for improved interfacial adhesion in a thermoplastic matrix (polypropylene, PP) via partial defluorination of the F-SWNTs. The partial removal of functional groups from the F-SWNTs during melt processing with PP by shear mixing provides the opportunity for in situ direct covalent bonding between the nanotubes and the matrix during melt processing which ultimately results in better mechanical reinforcement of the composite. The studies conducted herein demonstrate that in comparison with PP composites filled with purified nanotubes (P-SWNTs), improved dispersion, interfacial adhesion, and mechanical properties are achieved for F-SWNT-loaded matrixes due to chemical functionalization.

Functional Covalent Chemistry of Carbon Nanotube Surfaces

“…Third, fluorinated SWNTs covalently bound to a polypropylene matrix can noticeably improve mechanical properties (e.g., >100% increase in tensile modulus) with respect to pristine tubes. [193] Such an improvement in mechanical behavior is in agreement with theory. [194] Recently, a ''green'' derivatization of SWNTs has been reported [195] in which amino groups on the SWNTs initiated polymerization into Nylon 6 in the presence of e-caprolactam.…”

Multi-walled carbon nanotube filled polypropylene nanocomposites based on masterbatch route: Improvement of dispersion and mechanical properties through PP-g-MA addition

“…However, CNT dispersion in non-polar polymers such as polypropylene during melt processing remains a challenge. Techniques such as end-group functionalization [10][11][12], use of ionic surfactants [13], shear mixing [14,15] and plasma coating [16] have been used to improve dispersion and exfoliation of nanotubes in polypropylene matrix. Polypropylene compatibility with fillers has been improved by matrix modification by grafting it with reactive moieties, such as acrylic acid, acrylic esters, and maleic anhydride [17,18].…”

Current Approaches to Designing Nanomaterials Inspired by Mussel Adhesive Proteins

“…between the inorganic and organic components to achieve elevated mechanical properties and extensibility as well as the ability to recover after large, repeated deformation [106,107]. Mechanical properties of nanocomposites are strongly affected by the interfacial binding strength between the nanoparticles and the polymer matrix as effective stress transfer is necessary between these two components [108][109][110][111]. Strong interfacial adhesion is especially critical for materials that experience cyclic loading to prevent rapid breakdown at the interface [111].…”