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

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.

An investigation on the structural characteristics and reinforcement of melt processed polyamide 66/multiwalled carbon nanotube composites

“…The formation of rigid and glassy polymeric layer around nanoparticle for attractive polymer nanocomposite systems, where the polymer and reinforcing nanoparticle show strong affinity, was also postulated by Papakonstantopoulos et al ., illustrating the critical role of such layer on the mechanical properties enhancement of polymer nanocomposite. The critical role of crystalline layer around the CNT bundle on the mechanical performance of PVA/CNT was also demonstrated by Colman et al . Consistently with other researchers, the deviation from experimental data observed in this study may be explained by the increase in the degree of crystallinity of PA66 via incorporation of CNT, which was thought to be created as crystalline layer around nanotube.…”

Effective reinforcement in carbon nanotube–polymer composites

“…MWNTs were seen to nucleate polymer crystal growth and this crystal structure was proposed as the dominant reinforcement. Similar results were also shown in other studies of semi-crystalline polymer-carbon nanotube bulk systems (Bhattacharyya et al 2003;Coleman et al 2004;Ciselli 2007). However, no direct visualization of preferential polymer morphology at a nanotube surface has been reported in the literature, unless using highly specific processing conditions using an individual nanotube (Barber et al 2004a,b).…”

Processing of Poly(propylene)/Carbon Nanotube Composites using scCO2‐Assisted Mixing

“…In a previous study, Young's modulus of the composites has been reported to increase with polymer matrix crystallinity 39. Similar results were also shown in many other studies and changes in crystallinity and crystalline morphology of the polymer matrix can have pronounced effects on the mechanical properties of nanocomposites next to mechanical reinforcing effects from nanofillers 10, 40, 41…”