High Performance Nanotube‐Reinforced Plastics: Understanding the Mechanism of Strength Increase

TLDR

The composites were fabricated by dispersing multiwalled carbon nanotubes in poly(vinyl alcohol) and chlorinated polypropylene, with a crystalline coating forming around the tubes in the PVA system and covalent attachment of PP chains to the tubes in the PP system to maximize interfacial stress transfer. The resulting materials showed substantial mechanical improvements—Young’s modulus, tensile strength, and toughness increased by factors of 3.7, 4.3, and 1.7 for PVA and 3.1, 3.9, and 4.4 for PP at <1 wt % nanotubes—while a derived model linked tensile strength to interface thickness, suggesting that enlarging the crystalline or functionalized interfacial volume can further enhance strength.

Abstract

Abstract Polymer–multiwalled carbon nanotube composite films were fabricated using two types of polymer matrices, namely poly(vinyl alcohol), (PVA) and chlorinated polypropylene. In the first case, the PVA was observed to form a crystalline coating around the nanotubes, maximising interfacial stress transfer. In the second case the interface was engineered by covalently attaching chlorinated polypropylene chains to the nanotubes, again resulting in large stress transfer. Increases in Young's modulus, tensile strength, and toughness of × 3.7, × 4.3, and × 1.7, respectively were observed for the PVA‐based materials at less than 1 wt.‐% nanotubes. Similarily for the polypropylene‐based composites, increases in Young's modulus, tensile strength and toughness of × 3.1, × 3.9, and × 4.4, respectively, were observed at equivalent nanotube loading levels. In addition, a model to describe composite strength was derived. This model shows that the tensile strength increases in proportion to the thickness of the interface region. This suggests that composite strength can be optimized by maximising the thickness of the crystalline coating or the thickness of the interfacial volume partially occupied by functional groups.