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

Kida, Takumitsu; Hiejima, Yusuke; Nitta, K.

doi:10.3144/expresspolymlett.2016.63

Cited by 28 publications

(47 citation statements)

References 33 publications

(74 reference statements)

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“…The details of in situ Raman spectroscopy have been described in the previous papers [22][23][24][25]. A DPSS laser (LASOS, Jena, Germany, 639.7 nm in the wavelength, 200 mW in laser power) was used as the incident laser light and a monochromator (PIXIS 100 and Spectra Pro 2300i, Princeton Instruments, Trenton, USA, NJ) was used as the detector.…”

Section: In-situ Raman Spectroscopymentioning

confidence: 99%

“…Then, the ODF is written as [24,38,39] (4) where 2 and 4 are the Lagrange multipliers determined to satisfy the following two constraints.…”

Section: Orientation Parametermentioning

confidence: 99%

“…Although the rheo-Raman spectroscopy was applied, the strain rate effect was not clearly observed [18], presumably due to the low strain rate of ~10 -3 s -1 . Recent development of optical apparatus enable us to measure Raman spectra at sufficiently short exposure time of ~1 s. We have developed custom-made in-situ Raman spectroscopy [22,24] with the minimum exposure time during deformation is about 0.1 s. In this study, we performed rheo-Raman spectroscopy of highdensity polyethylene (HDPE) to evaluate the effects of strain rate on the microscopic deformation behavior. The molecular orientation and the load sharing of molecular chains of HDPE were evaluated during uniaxial stretching process.…”

Section: Introductionmentioning

confidence: 99%

“…Such a technique enables us to detect bulk properties (sress, strain, and strain rate) and coresponding local structural parameters (molecular orientation, microscopic stress, crystallinity, chain conformation) at same time during deformation. Especially, in-situ Raman spectroscopy have been useful to evaluate the molecular orientation distribution [22,24] and the microsocpic stress applied to the skeletal chains for PE and PP under deformation [22,25,29].…”

Section: Introductionmentioning

confidence: 99%

“…For in-situ study of the structural changes during deformation, one of the most powerful tools is the rheooptics, which is the simultaneous measurements of mechanical testing and optical measurements such as birefringence, infrared (IR) spectroscopy, X-ray scattering, or Raman spectroscopy[9, [15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Such a technique enables us to detect bulk properties (sress, strain, and strain rate) and coresponding local structural parameters (molecular orientation, microscopic stress, crystallinity, chain conformation) at same time during deformation.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Strain Rate on Microscopic Deformation Behavior of High-density Polyethylene under Uniaxial Stretching

2017

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Abstract. The microscopic deformation behaviors such as the load sharing and the molecular orientation of highdensity polyethylene under uniaxial stretching at various strain rates were investigated by using in-situ Raman spectroscopy. The chains within crystalline phase began to orient toward the stretching direction beyond the yielding region and the orientation behavior was not affected by the strain rate. While the stretching stress along the crystalline chains was also not affected by the strain rate, the peak shifts of the Raman bands at 1130, 1418, 1440 and 1460 cm -1 , which are sensitive to the interchain interactions obviously, depended on the strain rate; the higher strain rates lead to the stronger stretching stress or negative pressure on the crystalline and amorphous chains. These effects of the strain rate on the microscopic deformation was associated with the cavitation and the void formation leading to the release of the internal pressure.

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Section: In-situ Raman Spectroscopymentioning

confidence: 99%

“…Then, the ODF is written as [24,38,39] (4) where 2 and 4 are the Lagrange multipliers determined to satisfy the following two constraints.…”

Section: Orientation Parametermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of Strain Rate on Microscopic Deformation Behavior of High-density Polyethylene under Uniaxial Stretching

2017

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Rheo‐Raman Study of Isotactic Polypropylene Under Tensile Deformation

Kida

Hiejima

Nitta

2018

Macromolecular Symposia

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The microscopic deformation behaviors such as the load sharing and the molecular orientation of the crystalline chains of isotactic polypropylene under tensile stretching are examined by using rheo-Raman spectroscopy. The Raman bands assigned to the skeletal C─C stretching modes show blue shifts after the yielding, indicating that the stretching stress is applied to the main chain. The CH 3 rocking band shows red shift in the yielding region, suggesting that the compression stress is applied in the interchain direction of the crystalline chains. While the molecular orientation of the crystalline chains begins after the first yield point, the crystalline orientation is hindered due to the existence of the rigid and bulky lamellar cluster units. Beyond the yielding region, the orientation toward the stretching direction proceeds rapidly, and the crystalline chains simply orient in the stretching direction in the highly strained region. Figure 6. Schematic illustration of microsocpic deformation in (a) yielding and (b) strain-hardening regions.

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In Situ Monitoring of Orientation Parameters and Orientation Distribution Functions of Polyethylenes during Tensile Tests

Hiejima

Kida

Nitta

2018

Macromolecular Symposia

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In situ polarized Raman spectroscopy is applied for the tensile deformation of high-and low-density polyethylenes (HDPE and LDPE), and the orientation parameters as well as the orientation distribution function (ODF) are determined. While random orientation is maintained in the elastic region, the orientation of the polymer chains begins after the first yield point. The ODF for LDPE shows a peak at the stretching direction throughout the elongation process, and the maximum value of the ODF monotonously increases with the strain. For HDPE, the ODF in the yielding region has a broad peak at an intermediate angle of 30-70 from the stretching direction, while the orientation at the stretching direction is restored in the strain-hardening region. The tilted orientation is explained with the concept of the lamellar cluster units formed in the yielding region after the collapse of the spherulites. The HDPE with lower molecular weight and that with wider molecular weight distribution show high orientation, which is explained with the smaller size of the lamellar cluster units and the higher network density in the amorphous phase, respectively.

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

Cited by 28 publications

References 33 publications

Effect of Strain Rate on Microscopic Deformation Behavior of High-density Polyethylene under Uniaxial Stretching

Effect of Strain Rate on Microscopic Deformation Behavior of High-density Polyethylene under Uniaxial Stretching

Rheo‐Raman Study of Isotactic Polypropylene Under Tensile Deformation

In Situ Monitoring of Orientation Parameters and Orientation Distribution Functions of Polyethylenes during Tensile Tests

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