Fourier‐transform infrared studies of polypropylene during mechanical deformation

Abstract

Quantitative Fourier‐transform infrared (FTIR) measurements of frequency shifts Δν and absorbance profile asymmetry are reported for various polypropylene samples as a function of uniaxial stress σ. Generally, it was found that the frequency shift coefficient αχ, defined by Δν = αχσ, depended on stress rate \documentclass{article}\pagestyle{empty}\begin{document}$\dot \sigma$\end{document}, draw ratio, λ, molecular orientation f, tensile modulus E, and annealing conditions. With annealing, αχ decreased with increasing shrinkage in the case of highly oriented isotactic PP. The αχ values for the “helix bands” were less affected than those for the “liquid bands.” With increasing \documentclass{article}\pagestyle{empty}\begin{document}$\dot \sigma$\end{document}, generally αχ increased to an apparent asymptotic limit. With increasing λ, f, or E, αχ also increased from αχ ≃ 0 for λ = 1 (spherulitic) to maximum values for highly oriented isotactic PP. The observed variations in αχ can be interpreted in terms of the changes in the peak position and shape of the nonuniform molecular stress distribution. Analogous behavior with x‐ray diffraction peaks obtained for polymers under stress is discussed.

Effect of Annealing Conditions on Molecular Structure and Physical Properties of Polypropylene Slit-Film Yarns

“…The infrared spectra of the variously annealed samples (Figure 8) showed the general features of PP between 650 and 4000 cm -1 with no significant differences between them. Assigned IR bands of PP are easily found in early work and agree with those previously reported for PP [16,17]. The 997 cm -1 band is a helix band [16] resulting from the vibrations of a helical conformation (trans-gauche-transgauche) of the isotactic PP.…”

Toward the accurate modeling of amorphous nonlinear materials—polymer stress relaxation (I)

“…and below. As explained in , this is consistent with and justified by the fact that stresses and strains are indisputably responsible for measurable gap reductions between the characteristic vibrational energy levels characterizing most or all material structures, as experimentally observed by various quantitative infra‐red spectroscopic methods , and therefore similar behavior should also apply to the much lower vibrational and rotational energies involved in polymer deformation and flow near and below the glass transition temperature. As to and , they will be assumed approximately equal in the present idealization.…”

Algae fiber polypropylene composites: Modeling of the degradation by solid state kinetics

“…The 1727 cm −1 band could also be assigned to the grafting reaction/bond of the maleic anhydride and the main polymer chain . Weak intensity bands were observed at 1161 and 1375 cm −1 , which can be assigned to CC stretching and CH bend, as are characteristic of pentane and polypropylene …”