Macroscopic CNT fibres inducing non-epitaxial nucleation and orientation of semicrystalline polymers

Abstract

In the presence of macroscopic fibres of carbon nanotubes (CNT), various semicrystalline polymers are shown to present accelerated crystallisation through the formation of a transcrystalline (TC) layer perpendicular to the fibre axis. From differential scanning calorimetry, polarized optical microscopy and X-ray diffraction we establish this to be due to much faster nucleation rates at the fibre surface. The formation of a TC layers is demonstrated for polyvinyldene fluoride, isotactic polypropylene and poly(lactic acid) in spite of the large differences in their chemistry and structure unit cells, suggesting that epitaxy in terms of lattice type or size matching is not a prerequisite. For the three polymers as well as poly(ether ether ketone), the TC layer is identically oriented with the chain axis in the lamella parallel to the CNTs, as observed by wide and small angle X-ray scattering. These results point to polymer chain orientation at the point of adsorption and the formation of a mesomorphic layer as possible steps in the fast nucleation of oriented lamella, with wetting of the CNT fibre surface by the molten semi-crystalline polymer a key condition for heterogeneous nucleation to take place.

Morphology, thermal, and crystallization analysis of polylactic acid in the presence of carbon nanotube fibers with tunable fiber loadings through polymer infiltration

“…Our previous study showed that several polymers in their molten state could easily wet and infiltrate into porous CNT fibers through capillary action as a consequence of their large surface area . When CNT fiber is immersed into polymer solution of PLA in dichloromethane and the solvent is removed subsequently, polymer coverage of the inner structure of the CNT fibers also occurred, as shown in SEM images (Figure ).…”

“…In a previous paper, we reported the observation of nonepitaxial nucleation and orientation of different semicrystalline polymers (PVDF, PLA, PEEK, and PP) induced by the presence of macroscopic CNT fibers. Because these composites were prepared by hot‐pressing, it was speculated that polymer chain orientation could be induced by shear forces arising during the flow of the polymer melt through the elongated pore structure of the CNT fibers.…”

“…Thus, macroscopic fiber is a relative new class of materials with applications in field such as structural reinforcement fibers, sensors, porous electrodes, and current collectors moderate surface area (200~300 m 2 /g), and good affinity to many polymers make CNT fibers very promising macroscopic reinforcing elements for nanocomposite fabrication. More importantly, composites containing high volume fraction of CNT fibers can be obtained through back infiltration of polymer into porous CNT fiber networks, in which load and charge carrying CNT elements could lead to significant improvements in the resulting composite properties.…”

Periodic Functionalization of Graphene‐Layered Alumina Nanofibers with Aromatic Thermosetting Copolyester via Epitaxial Step‐Growth Polymerization

“…Additionally, in the ATSP system, acetoxy and carboxylic acid‐capped reactive functional groups of the oligomers could react with oxygenated functional sites on the ANFCs that would produce a physicochemical attachment mechanism on the site (Figure S8 and Table S1, Supporting Information) . Additionally, as carbonaceous materials could behave as a nucleation agent, the crystal conformation of the polymer systems aligned with low energy adsorption sites on the surface . Besides, the aromatic structure of the graphitic layers could form a base for π–π predominant interactions with corresponding aromatic rings in the ATSP backbone.…”

“…Leibler and co‐workers showed the development of crystallinity in polyamide‐6 on CNT surface . At last, Vilatela and co‐workers analyzed macroscale fibers in polyvinylidene fluoride, isotactic polypropylene, and poly(lactic) acid in which heterogeneous nucleation initiated non‐epitaxial growth of crystalline sites on the fiber surfaces …”