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

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.