Mechanically and thermally induced chain conformational transformations between helical form I and trans-planar form III in syndiotactic polypropylene using FT-IR and Raman spectroscopic techniques

Gatos, Konstantinos G.; Kandilioti, Georgia; Galiotis, Costas; Gregoriou, Vasilis G.

doi:10.1016/j.polymer.2004.03.095

Cited by 27 publications

(28 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, the Raman lines located at 1152, 1034, 900, and 841 cm -1 in molten isotactic and sindiotactic polypropylene are coincident or almost coincident. [17][18][19] As expected, some other Raman lines are characteristic either to the sindiotactic or isotactic addition of monomers. 17 Pristine polymers such as iPP show no ESR spectra.…”

Section: Introductionsupporting

confidence: 81%

“…As observed from Figure 2(A), the absence of a very strong Raman line lo- cated at 850 cm -1 rules-out the possibility of sindiotactic-like structures. 18,19 The degree of crystallinity of iPP may be inferred from Raman spectra within a threephase model 19 that implies a crystalline phase responsible for the Raman line located at 808 cm -1 , a defected phase containing mostly helical chains identified by the Raman line located at 840 cm -1 , and a melt-like structure assigned to amorphous polypropylene and assigned to the line noticed at 830 cm -1 . 19 As noticed from Figure 3 (bottom spectrum), the as-recorded Raman lines were observed at slightly higher Raman shifts.…”

Section: Resultsmentioning

confidence: 99%

“…18,19 The analysis of Raman spectra of polypropylene is complicated by the fact that in most cases A and E modes are mixed. 18,19 Certain Raman modes are not significantly affected by the configuration and conformation of macromolecular chains. For example, the Raman lines located at 1152, 1034, 900, and 841 cm -1 in molten isotactic and sindiotactic polypropylene are coincident or almost coincident.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Chipara¹,

Villarreal²,

Chipara³

et al. 2009

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

Isotactic polypropylene‐vapor grown carbon nanofiber composites containing various fractions of carbon nanofibers, ranging from 0 to 20 wt %, have been prepared. Raman spectroscopy was used to analyze the effect of the dispersion of carbon nanofibers within polypropylene and the interactions between carbon nanofibers and macromolecular chains. The as‐recorded Raman spectra have been successfully fitted by a linear convolution of Lorentzian lines. Changes of the Raman lines parameters (position, intensity, width, and area) of polypropylene and carbon nanofibers were analyzed in detail. The Raman spectra of the polymeric matrix—at low concentrations of nanofibers—show important modifications that indicate strong interactions between carbon nanofibers and the polymeric matrix reflecting by vibrational dephasing of macromolecular chains. The Raman spectrum of carbon nanofibers is sensitive to the loading with carbon nanofibers, showing changes of the resonance frequencies, amplitudes, and width for both D‐ and G‐bands. Raman data reveals the increase of the disorder, as the concentration of carbon nanofibers is increased. The presence of the typical ESR line assigned to conducting electrons delocalized over carbon nanofibers is confirmed and the presence of a spurious magnetic line due to catalyst's residues is reported. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1644–1652, 2009

show abstract

Section: Introductionsupporting

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Chipara¹,

Villarreal²,

Chipara³

et al. 2009

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

show abstract

“…Both the opaque and transparent stripes appear to have the same thermal response. Pure sPP shows a small endothermic peak at 100°C, which owes its existences to helical form I crystalline phase [6,9]. In both opaque and transparent zones this peak is being suppressed as seen in Figure 3.…”

Section: Resultsmentioning

confidence: 87%

“…These segments cause a strain-hardening effect during the material necking which leads to stress fluctuation. Gatos et al [9] have successfully shown that the result of the stress oscillation in sPP is a differentiating crystallization scheme in the opaque and the transparent zones of the specimens. According to Bazhenov et al [10,11], pores which are created in the plastic deformation region and polymer heat conductivity are the main factors influencing the mechanism of stress oscillation.…”

Section: Introductionmentioning

confidence: 99%

Study of the stress oscillation phenomenon in syndiotactic polypropylene/montmorillonite nanocomposites

Mouzakis¹

2010

Express Polym. Lett.

View full text Add to dashboard Cite

Abstract. The phenomenon of Stress Oscillation (SO) was studied in syndiotactic polypropylene and syndiotactic polypropylene nanocomposites with montmorillonite. The effect was provoked by varying the crosshead speed during tensile testing of thin stripes. The internal morphology of the stress oscillated specimens was studied by scanning electron microscopy on chemically etched samples revealing that cavitation prevails inside the opaque stripes of the yielded areas. Differential scanning calorimetry proved that there exists virtually no crystallinity differentiation between the characteristic alternating opaque/transparent stripes that mark the stress oscillation during necking. Finally a simple finite element model of the necking area of the specimens revealed non-uniform internal stress distributions of yield-point magnitudes.

show abstract

Morphology and Structure of Constituent Fibres in Thermally Bonded Nonwovens

Wang¹,

Gong²

2006

Macro Materials & Eng

View full text Add to dashboard Cite

Summary: A new process has been developed to produce three‐dimensional nonwovens directly from staple fibres. In order to establish suitable windows of the process parameters to achieve high‐quality nonwoven products, the effects of thermal bonding temperature, dwell time and mould material on the morphology and structure of the fibre have been investigated using PP/PET bi‐component fibres. It was evident from both scanning electron microscope images and Raman spectra that thermal‐induced shrinkage of the PP sheath fibre occurred in the thermal bonding process, leading to deformation and cracking of the PP sheath and exposure of the PET core. X‐ray diffraction results revealed crystal imperfection and/or less ordered polymer chains, more γ‐form and thermal contraction of the crystal lattice for the PP sheath fibre, while birefringence measurements indicated that both the birefringence and the orientation factor for the PP fibre decreased after the thermal bonding process. The degrees of the thermal‐induced shrinkage increased, and the crystallinity, birefringence and orientation factor of the PP sheath fibre decreased with increasing thermal bonding temperature, dwell time and thermal conductivity of the mould material. All these can be attributed to the different levels of modification of chemical composition caused by thermal oxidative degradation and thermal‐induced relaxation of the orientation during the thermal bonding process.Changes of morphology and crystalline features of PP/PET fibre after thermal bonding process.imageChanges of morphology and crystalline features of PP/PET fibre after thermal bonding process.

show abstract

Mechanically and thermally induced chain conformational transformations between helical form I and trans-planar form III in syndiotactic polypropylene using FT-IR and Raman spectroscopic techniques

Cited by 27 publications

References 59 publications

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

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

Study of the stress oscillation phenomenon in syndiotactic polypropylene/montmorillonite nanocomposites

Morphology and Structure of Constituent Fibres in Thermally Bonded Nonwovens

Contact Info

Product

Resources

About