Deformation Mechanisms of Polymer Thin Films by Simultaneous Kinetic Measurement of Microscopic Infrared Dichroism and Macroscopic Stress. 2. Molecular Orientation during Necking Process of Isotactic Polypropylene

Abstract

The molecular orientations in the crystalline and the amorphous phases in a quenched isotactic polypropylene (iPP) film with a smectic structure are studied using an instrument constructed for simultaneous kinetic measurement of microscopic infrared (MicIR) dichroism from a predetermined sampling area with a size of 200 × 200 μm2 and macroscopic stress of film uniaxially stretched at a constant elongation rate at 30 °C. Local deformation behavior in the sampling area is determined for one sample using a method of photogrammetry. During the passage of the necking through the sampling area, the local extension ratio λ(t) increases fast from 1.5 to 5, which induces the rapid orientation of iPP chains in both the crystalline and the amorphous phases. The orientation function of the amorphous phase, f am, from the mesoscale deformation of the sampling area is found to be well described by the pseudo-affine deformation mechanism, since the local area shrinks anisotropically during the passage of the neck shoulder. The orientation function f c in the crystalline phase increases linearly with f am up to f am = 0.3 with a slope of 1.85 for all samples tested. In the neck entity, the crystal orientation may lag behind the amorphous chain orientation due to the enhanced plastic deformations. It is shown that the behavior of the amorphous phase is essential for the averaged lamellar orientation on the mesoscale.

Molecular orientation behavior of isotactic polypropylene under uniaxial stretching by rheo-Raman spectroscopy

“…The strain dependence of < P 2 chain > under uniaxial stretching is in good agreement with previous results from in situ IR spectroscopy studies, [7,29] and Raman spectroscopy results of drawn samples [9,13].…”

Oriented structure of PP/LLDPE multilayer and blends films

“…Spectra portions of interest in the case of LLDPE and PP are Table 1 Polymer resins used in this work and some of their characteristics K1 vibration is well referenced and associated with the PP crystalline phase [18,19] and 1153 cm K1 was assigned to the amorphous phase [20]. The 973 cm K1 vibration was observed to be associated with both crystalline and amorphous phases [21].T h e 1256 cm K1 is a mixed vibration (amorphous and crystalline phase), having a transition moment angle with chain axis of 38.58 [22]. The 840, 998 and 1165 cm K1 are among the strong vibrations and are associated with a-PP helical crystal.…”

Preparation and characterization of isotactic polypropylene/high‐density polyethylene/carbon black conductive films with strain‐sensing behavior

“…At the same time, the distances between the neighboring particles increased, and the number of the effective conductive paths decreased with the straightening of the chains and the separation of an oriented lamellar. With the removal of the external force, the lamellae could recover to their initial state because of movement of the noncrystalline chains . The recovery of the oriented lamellae drove the particle network back to the original position.…”