Fourier transform infrared spectroscopy and wide-angle X-ray scattering: Investigations on polypropylene–vapor-grown carbon nanofiber composites

Authors

Mircea Chipara, University of Texas Pan AmericanFollow
John Hamilton, University of Texas Pan American
Alin Cristian Chipara, University of Texas Pan AmericanFollow
Tom George, University of Nebraska-Lincoln
Dorina Magdalena Chipara, University of Texas Pan AmericanFollow
Elamin E. Ibrahim, University of Texas Pan American
Karen Lozano, University of Texas Pan American
David J. Sellmyer, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

7-2012

Citation

Journal of Applied Polymer Science 125:1 (July 5, 2012), pages 353–360; doi: 10.1002/app.35576

Comments

Copyright © 2011 Wiley Periodicals, Inc. Used by permission.

Abstract

Fourier transform infrared (FTIR) spectroscopy and wide-angle X-ray scattering (WAXS) investigations of isotactic polypropylene (iPP)–vapor-grown carbon nanofiber (VGCNF) composites containing various amounts of VGCNFs ranging between 0 and 20 wt %. are reported. The FTIR investigations were focused on the regularity bands of iPP. The FTIR data indicated a drop in the isotac­ticity index as the concentration of nanofibers was increased; this suggested a decrease in the crystallinity. WAXS measurements revealed a dominating α₁ phase, with a small admixture of γ phase or mesophase. The loading of the polymeric matrix with car­bon nanofibers (CNFs) did not induce significant changes in the morphology of the polymeric matrix. A weak decrease in the size of α crystallites upon loading of CNFs was noticed. The experimental data obtained by FTIR spectroscopy supported the WAXS data. Spectroscopic data (a drop in the isotacticity index as estimated by FTIR spectroscopy and the ratio between the crystalline and total areas of WAXS lines assigned to iPP) failed to confirm the enhancement of the degree of crystallinity of polypropylene upon loading by nanofibers. However, whereas both techniques can identify with a high accuracy vibrations in ordered domains (FTIR spectroscopy) and the crystalline structure, including the lattice parameters and the size of crystallites (WAXS), difficulties in the correct assessment of the baseline and of amorphous components may result in important errors (typically >5%) in the esti­mation of the degree of crystallinity of the polymeric component.