Deformation-Induced Crystallization and Associated Morphology Development of Carbon Nanotube-PVDF Nanocomposites

Abstract

Poly(vinylidene fluoride) (PVDF) is a semicrystalline thermoplastic polymer that is of interest for sensor, actuator and biomedical applications because of its piezoelectric and pyroelectric properties, as well as outstanding mechanical and chemical properties. Although it is known that the shear-induced crystallization behavior of nanocomposites can be significantly affected by the presence of nanoparticles, the effects of the incorporation of carbon nanotubes on the deformation-induced crystallization and associated morphology development of PVDF have not been previously investigated. Here the dynamics of the shear-induced crystallization of carbon nanotubes incorporated in PVDF were investigated using simple shear flow. The shear-induced crystallization behavior was affected by the deformation rate, temperature, and the concentration of the carbon nanotubes. Time-dependence of linear viscoelastic properties indicated that the presence of multi-walled carbon nanotubes (MWNTs) in PVDF greatly altered the shear-induced crystallization kinetics of PVDF, while no significant changes in crystallization behavior were observed for pure PVDF samples sheared under similar conditions. Upon increase of the concentration of the MWNTs the crystal size of PVDF decreased while its rate of crystallization increased in conjunction with an increase of the beta phase crystallization. Overall, these findings suggest that the shear-induced crystallization of PVDF nanocomposites (and in general flow-induced crystallization effects associated with the thermo-mechanical history experienced by the nanocomposite during processing) should be integral parts of attempts to generate a comprehensive understanding of the development of the microstructural distributions and the coupled ultimate properties of polymer nanocomposites.

Polymer crystallization and precipitation‐induced wrapping of carbon nanofibers with PBT

“…The increased crystallinity can be attributed to the high surface area and the associated heterogeneous nucleation effect of the CNFs. An increase in crystallinity upon the addition of MWNTs has likewise been observed for other polymers such as PVA 53 and PVDF, 44 whereas a decrease in crystallinity has been observed for poly(ethylene oxide) (PEO) nanocomposites. 54 It appears that the incorporation of the CNTs or nanofibers can either promote or hinder the crystallization process, presumably affected by a number of factors including the molecular weight and short and long chain branch distributions of the macromolecules that can alter crystallinity development within the nanocomposite.…”

“…Such heterogeneous nucleation effects have also been noted to occur on nanofiller surfaces during melt as well as solution crystallization of other semicrystalline polymers including PE, nylon-6,6, poly(propylene) (PP), and poly(ethylene naphthalate) (PEN). 21,[42][43][44][45] A decrease in polymer crystal size and an increase in the rate of crystallization have also been observed during various studies performed under shear as well as under quiescent conditions. 43,44,46 Precipitation of PBT and CNF-PBT nanostructures Representative SEM micrographs of the 4.8% CNF-PBT precipitates obtained upon the solvent-antisolvent precipitation process are shown in Figure 7.…”

“…21,[42][43][44][45] A decrease in polymer crystal size and an increase in the rate of crystallization have also been observed during various studies performed under shear as well as under quiescent conditions. 43,44,46 Precipitation of PBT and CNF-PBT nanostructures Representative SEM micrographs of the 4.8% CNF-PBT precipitates obtained upon the solvent-antisolvent precipitation process are shown in Figure 7. The polymer precipitation takes place due to the interdiffusion of solvent and antisolvent, with the rate of interdiffusion dependent on the solubility parameters of the solvent and antisolvent used.…”

Improving the thermal properties of fluoroelastomer (Viton GF-600S) using acidic surface modified carbon nanotube

“…The materials used were Viton GF-600S fluoroelastomer, FE; organic peroxide, Luperox 101 XL-45; acid surface modified carbon nanotube MCNT (TNMC8, -COOH Content:0.49wt%), carbon nanotube CNT (TNM8) both with an outside diameter > 50 nm, inside diameter:5-15nm, purity > 95%, and length [10][11][12][13][14][15][16][17][18][19][20] Mixing FE with additives was done using a laboratory scale two roll mill with a roll temperature of 48°C. FE in the above mentioned composition was supplied to the open roll.…”

“…CNT can change the mechanical and thermo-mechanical properties of polyvinilydienefluoride (PVDF) [9][10][11] or the mechanical properties of polytetrafluoroethylene (PTFE) [12,13] . CNT can also change the degree of crystallinity of fluoropolymers and, therefore, their properties [14][15][16] .…”