Benzoyl Peroxide Initiated In Situ Functionalization, Processing, and Mechanical Properties of Single-Walled Carbon Nanotube−Polypropylene Composite Fibers

Abstract

Benzoyl peroxide initiated in situ functionalization of single-walled carbon nanotubes (SWNT) represents a simple means of generating reactive sites on the surface of carbon nanotubes by exploiting free radical interactions with the surrounding polymer matrix. The resulting composite, when processed into fiber form, demonstrates improved mechanical properties. Functionalization of carbon nanotubes has in general been used as a means of increasing their solubility and dispersion in polymeric systems, allowing for the manufacture of composites with increased mechanical properties. Beyond the addition of chemical moieties to the surface of single-walled and multiwalled carbon nanotubes, researchers have used in situ reactions to link carbon nanotubes directly to the surrounding polymer matrix in hopes of taking better advantage of their strong reinforcing properties. In this work, we present a method to produce a composite of this nature by using a single processing step. An in situ reaction, initiated by the production of free radicals upon the decomposition of benzoyl peroxide during the high shear and high-temperature phase of processing, allows for the linkage of the single-walled carbon nanotube to the surrounding polypropylene matrix via a covalent bond. The resulting composite was spun into 2.5, 5, 7.5, and 10 wt. % SWNT/polypropylene fibers that demonstrated improved mechanical properties in tensile strength by 82.9, 89.8, 72.3, and 173.1%, and in the elastic modulus by 69.2, 99.7, 137.2, and 133.7%, respectively, over that of the neat polypropylene fibers.

Poly(ethylene-co-butylene) functionalized multi walled carbon nanotubes applied in polypropylene nanocomposites

“…For polymer grafting of CNTs (17) especially radical (18)(19)(20)(21) and nitrene (22,23) approaches have been applied, since the reactive groups required for grafting can be introduced through common polymer endgroups. There are two examples of radical grafting of MWCNT in PP, where benzoyl peroxide has been applied in melt mixing (24,25). In one case the material was used for drawing fibers and here a substantial improvement was observed (24), while in the other only moderate mechanical improvements were observed (25).…”

“…There are two examples of radical grafting of MWCNT in PP, where benzoyl peroxide has been applied in melt mixing (24,25). In one case the material was used for drawing fibers and here a substantial improvement was observed (24), while in the other only moderate mechanical improvements were observed (25). In these investigations the effects upon conductivity was not addressed.…”

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].…”

Functional Covalent Chemistry of Carbon Nanotube Surfaces

“…Upon mixing and reaction with functionalized SWNTs, containing pendant, terminal amino groups, a dramatic improvement in the mechanical properties of the resulting epoxy polymer material in terms of strength and modulus was noted. [191] Second, a series of 2.5, 5, 7.5, and 10 wt% SWNT/polypropylene composite fibers, [192] formed by a benzoyl peroxide initiated in situ functionalization of SWNTs, possesses improved mechanical properties in tensile strength of 82.9, 89.8, 72.3, and 173.1%, and in the elastic modulus of 69.2, 99.7, 137.2, and 133.7%, respectively, over that of neat polypropylene fibers. 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.…”