Nanocomposites of isotactic polypropylene with carbon nanoparticles exhibiting enhanced stiffness, thermal stability and gas barrier properties

Abstract

Stavrev, et al.. Nanocomposites of isotactic polypropylene with carbon nanoparticles exhibiting enhanced stiffness, thermal stability and gas barrier properties. Composites Science and Technology, Elsevier, 2009, 68 (3-4) AbstractCarbon nanoparticles (CN), synthesized by a shock wave propagation method from the free carbon of the explosive, were dispersed in isotactic polypropylene (iPP) using a twin screw corotating extruder. These materials were analyzed for their tensile properties, crystallization morphology, thermal stability under N 2 , O 2 and air, as well as their permeability rates for N 2 , O 2 and CO 2 . Young's modulus was significantly enhanced, as was the tensile strength at the yield point, although at a smaller extent. However, the tensile strength and elongation at the break point slightly deteriorated with the increase of the filler's concentration. This behavior was attributed to the increase tendency of CN to form aggregates into iPP matrix by increasing its content. The size of aggregates, as was evaluated by extended micro-Raman mapping, is ranged from 1 up to 5 m. The nanoparticles caused a significant reduction of the iPP chain's mobility leading to smaller and less ordered crystallites, with the appearance of -phase crystallites at CN content 5 wt%. In inert atmosphere (N 2 ) the presence of the nanoparticles caused a shift of the starting decomposition temperature (T d ), from 368 up to 418.6 o C, while, under oxygen, thermal decomposition was more complex, displaying more than two stages. The T d was slightly lowered, up to a filler content of 2.5 wt%, with the nanoparticles exhibiting a catalytic role at the beginning of the polymer's decomposition. Under air, the degradation behavior was between ACCEPTED MANUSCRIPT 2 those exhibited in inert and O 2 atmospheres. Permeability rates for the gases measured were substantially lowered with increasing filler content.

Spectroscopic investigations on polypropylene‐carbon nanofiber composites. I. Raman and electron spin resonance spectroscopy

“…Similar data have been reported in the case of PP loaded with SWCNTs. 10,11,30 The increase of the D-line position as the concentration of VGCNFs/SWCNTs is increased up to 10 % was assigned to the intercalation of macromolecular chains among filler's particles, suggesting an increase of the debundling efficiency of VGCNFs during the processing step. The decrease of the D-line position as the concentration of VGCNFs/SWCNTs is further increased (above 15 wt % VGCNFs) was assigned to the weak aggregation of VGCNFs.…”

“…The decrease of the D-line position as the concentration of VGCNFs/SWCNTs is further increased (above 15 wt % VGCNFs) was assigned to the weak aggregation of VGCNFs. 11,12 The G-line is wide and intense, suggesting in-plane structural disorder. 9-16, 14, 28-32 .…”

“…[10][11][12][13] This section focuses on the analysis of the Raman spectra of both VGCNF and iPP in composites containing various amounts of VGCNFs, aiming to extract new information regarding the interaction of macromolecular chains with the nanofiller from an exhaustive analysis of Raman spectra.…”

“…This analysis is traditionally focused on the Raman lines due to the filler (VGCNFs). [9][10][11][12][13][14][15][16] The original aspect of this study derives from the fact that the analysis of Raman spectra includes both the polymeric matrix and the filler. This required the computer deconvolution of the full Raman spectrum and resulted in a more accurate estimation of Raman lines positions, amplitudes, widths, and areas.…”

“…The study aims to a better understanding of the interactions between VGCNFs and iPP adding precision and rigor to the existing literature. [9][10][11][12][13][14][15][16] The second part of the study will inspect the effect of VGCNF on the crystallinity of the polymeric matrix. Preliminary investigations on the morphology and thermal stability of iPP-VGCNF, performed on the same samples, have been reported elsewhere.…”