Nucleation of Polypropylene Crystallization by Single-Walled Carbon Nanotubes

Abstract

Nonisothermal and isothermal crystallization experiments were performed on polypropylene mixed with carbon nanotubes produced by disproportionation of CO on Co−Mo catalysts. Functionalization of the nanotubes with octadecylamine made the tubes hydrophobic and allowed the tubes to be solubilized in an organic solvent. Mixing of the nanotubes with the polymer was accomplished by adding the nanotubes to a Decalin solution that contained dissolved polypropylene, followed by evaporation of the solvent. Dynamic mechanical analysis indicated very little difference in the small-strain mechanical properties between filled and unfilled polymers at the very low solid levels that were tested. By contrast, the crystallization behavior of the filled and unfilled polymer was quite different. Nanotubes promoted growth of the less-preferred beta form of crystalline polypropylene at the expense of the alpha form. In nonisothermal crystallization, the total amount of crystalline material in the sample was the same for the filled and unfilled materials. However, for isothermal crystallization experiments, the percent crystallinity in the filled materials was slightly higher. Most importantly, the rate of crystallization was substantially higher in the filled system. The results presented in this paper clearly show that carbon nanotubes nucleate crystallinity in polypropylene.

Effects of carbon nanotubes on polymer physics

“…168 In polylactide, nanotubes can promote the disorder-to-order transition (a 0 to a) in the crystalline material. 202 An early paper by the present author suggested that nanotubes favored the beta phase in isotactic polypropylene based on multiple endotherms in DSC experiments 203 while other papers suggested the alpha form was favored. [204][205][206][207] Nanotubes can induce complicated melting-recrystallization phenomena, indicating that claims about polymorphism in isotactic polypropylene must be substantiated with X-ray diffraction measurements casting significant doubt on the conclusions reached by the present author in the early paper.…”

The fine dispersion of functionalized carbon nanotubes in acrylic latex coatings

“…Seven patents have already been issued for CNT nanocomposites and fibers. 8 Four of the most common processing routes for this class of nanocomposites are (1) in-situ polymerization, 11 (2) melt processing and extrusion, 12 (3) casting from a common solvent, 13 and (4) functionalisation of the CNT by polymers. 14 Recently, nanocomposite films were prepared from CNTs that were functionalized with poly(vinyl alcohol) (PVA) to make them dispersible in water.…”

Improving the mechanical properties of single-walled carbon nanotube sheets by intercalation of polymeric adhesives

“…This is in good agreement with previous studies showing nanotubes acting as nucleation sites for polymer crystal growth. 8,[12][13][14] Static mechanical properties were measured by DMA for all sheets. Shown in Fig.…”

“…Because the polymer strands tend to crystallize on the nanotube, effective interfacial interaction is expected. 8,[12][13][14] This results in very high polymer-mediated internanotube stress transfer compared to the polymer-free case, and correspondingly improved macroscopic mechanical properties. As the minimum inter-rope separation is of order 0.34 nm and the average rope diameter can be approximated as ϳ35 nm, the amount of polymer needed to begin to reinforce the narrowest inter-rope junctions can be estimated as ϳ3%.…”