研究者詳細 - 木田　拓充

論文 - 木田　拓充

分割表示74 件中 61 - 74 件目／全件表示 >>

ラマン分光法を用いた結晶性ポリオレフィン材料の微視的変形挙動の解析査読

木田拓充

高分子論文集 75 ( 6 ) 497 - 506 2018年11月

Microscopic structural changes during photodegradation of low-density polyethylene detected by Raman spectroscopy 査読

Yusuke Hiejima, Takumitsu Kida, Kento Takeda, Toshio Igarashi, Koh-hei Nitta

Polymer Degradation and Stability 150 67 - 72 2018年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier Ltd

Raman spectroscopy has been used to reveal the microscopic structural changes of low-density polyethylene under ultraviolet irradiation. The fraction of non-crystalline consecutive trans chains (the molecular chains in the trans conformation separate from the orthorhombic crystalline phase) drastically decreases at ∼600 h, together with a decrement in the molecular weight and an increment in the crystallinity owing to chemicrystallization. This suggests that short trans chains are prolonged to form consecutive trans chains before chemicrystallization. Moreover, gradual increases of the stretching and compression stresses are observed on the trans and amorphous chains, respectively. These conformational changes are detected by Raman spectroscopy even in the early stage of photodegradation. Chemicrystallization at ∼600 h is accompanied by structural changes, such as shortening of the interchain distance of the lamellar crystals and thinning of the amorphous layer, which induce formation of surface cracks on the macroscopic specimen.

DOI： 10.1016/j.polymdegradstab.2018.02.010

Scopus

researchmap

その他リンク： http://orcid.org/0000-0002-9494-3004

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

Yusuke Hiejima, Takumitsu Kida, Koh-Hei Nitta

Macromolecular Symposia 377 ( 1 ) 2018年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley-VCH Verlag

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.

DOI： 10.1002/masy.201700020

Scopus

researchmap

その他リンク： http://orcid.org/0000-0002-9494-3004

Rheo-Raman Study of Isotactic Polypropylene Under Tensile Deformation 査読

Takumitsu Kida, Yusuke Hiejima, Koh-Hei Nitta

Macromolecular Symposia 377 ( 1 ) 2018年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley-VCH Verlag

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 CH3 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.

DOI： 10.1002/masy.201700019

Scopus

researchmap

その他リンク： http://orcid.org/0000-0002-9494-3004

Rheo-Raman Spectroscopic Study of Microscopic Deformation Behavior for Ultra Low-Density Polyethylene (ULDPE) 査読

Takumitsu Kida, Yusuke Hiejima, Koh-hei Nitta

Polymer International 2018年1月

Non-destructive detection of microscopic structural changes in polyethylene during photodegradation by Raman spectroscopy

Yusuke Hiejima, Takumitsu Kida, Toshio Igarashi, Kohhei Nitta

Annual Technical Conference - ANTEC, Conference Proceedings 2018- 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：Society of Plastics Engineers

Raman spectroscopy is applied to elucidate microscopic structural changes in low-density polyethylene under ultraviolet irradiation. The crystallinity estimated with the 1418 cm-1 band shows a stepwise increase at ~600 h accompanied by sharp decrease of the molecular weight, suggesting chemicrystallization. The increase of crystallinity and the thinning of amorphous layer at ~600 h lead to macroscopic shrinkage of the specimen, inducing the formation of surface cracks. It is also suggested that contraction of interchain distance and conformational changes take place gradually during photodegradation. In this work we demonstrate Raman spectroscopy can be utilized for non-destructive diagnosis of degradation and deterioration of polyolefin solids.

Scopus

researchmap

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

Takumitsu Kida, Yusuke Hiejima, Koh-Hei Nitta

MATEC Web of Conferences 130 2017年10月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：EDP Sciences

The microscopic deformation behaviors such as the load sharing and the molecular orientation of high-density 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.

DOI： 10.1051/matecconf/201713005001

Scopus

researchmap

その他リンク： http://orcid.org/0000-0002-9494-3004

The evaluation of degradation mechanism of polyolefins, and development of non-destructive evaluating method 査読

Igarashi T, Hiejima Y, Kida T, Nitta K.-H, Yonezawa Y

Annual Technical Conference - ANTEC, Conference Proceedings 2017-May 1207 - 1211 2017年

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

T. Kida, Y. Hiejima, K. -H. Nitta

EXPRESS POLYMER LETTERS 10 ( 8 ) 701 - 709 2016年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：BUDAPEST UNIV TECHNOL & ECON

The molecular orientation behavior of isotactic polypropylene (iPP) is investigated by using in situ Raman spectroscopy under tensile tests. A versatile method of the tilt-angle correction for the orientation parameters is newly developed, where the molecular orientation in highly oriented specimens is assumed to be entropically favorable. The real-time changes of orientation parameters and orientation distribution functions are determined for the molecular chain axis of iPP during uniaxial stretching. The molecular orientation remains random in the elastic region, and increases after the first yield point. In the yielding region, a broad distribution of orientation toward an intermediate angle of 30-70 degrees from the stretching direction is observed. This is interpreted as reorientation of the crystalline chains being hindered by rigid, bulky lamellar cluster units. After the yielding region, orientation toward the stretching direction proceeds rapidly, approaching highly oriented states.

DOI： 10.3144/expresspolymlett.2016.63

Web of Science

Scopus

researchmap

その他リンク： http://orcid.org/0000-0002-9494-3004

Raman spectroscopic study of high-density polyethylene during tensile deformation 査読

Takumitsu Kida, Yusuke Hiejima, Koh-hei Nitta

International Journal of Experimental Spectroscopic Techniques 1 ( 1 ) 1 2016年1月

Rheo-optical Raman study of microscopic deformation in high-density polyethylene under hot drawing 査読

Takumitsu Kida, Yusuke Hiejima, Koh-Hei Nitta

POLYMER TESTING 44 30 - 36 2015年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCI LTD

In situ observation of the microscopic structural changes in high-density polyethylene during hot drawing was performed by incorporating a temperature-controlled tensile machine into a Raman spectroscopy apparatus. It was found that the load sharing and molecular orientation during elongation drastically changed at 50 degrees C. The microscopic stress of the crystalline chains decreased with increasing temperature and diminished around 50 degrees C. Moreover, the orientation of the crystalline chains was greatly promoted above 50 degrees C. These microscopic structural changes were caused by the thermal activation of the molecular motion within lamellar crystalline chains owing to the onset of relaxation of the crystalline phase. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymertesting.2015.03.018

Web of Science

Scopus

researchmap

その他リンク： http://orcid.org/0000-0002-9494-3004

Deformation mechanism of high-density polyethylene probed by in situ Raman spectroscopy 査読

Takumitsu Kida, Tatsuya Oku, Yusuke Hiejima, Koh-hei Nitta

POLYMER 58 88 - 95 2015年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCI LTD

The microscopic mechanism of high-density polyethylene under uniaxial drawing is investigated using in situ Raman spectroscopy. From the peak shifts of the symmetric and anti-symmetric C-C stretching modes, it is found that the load sharing on the polymer chain in the yielding region is anisotropic with stretching along the chain and compression perpendicular to the chain. The orientation functions (< P2 > and < P4 >) as well as the orientation distribution function (N(theta)) are determined from the polarized Raman spectra. The molecular orientation with cold drawing is found to proceed more effectively for lower crystallinity specimens. In the yielding region, it is also found that N(theta) has a maximum at the polar angle theta = 30-70 degrees. This peculiar behavior in the microscopic scale is explained by the preferential collapse of spherulites and the existence of lamellar clusters as the bulky mobile units. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2014.12.030

Web of Science

Scopus

researchmap

その他リンク： http://orcid.org/0000-0002-9494-3004

Rheo-Raman Spectroscopic Study of Uniaxial Plastic Deformation Behavior in High-Density Polyethylene Solids 査読

Yusuke Hiejima, Takumitsu Kida, Koh-hei Nitta

Advances in Materials Science Research. Volume 20 2015年

ラマン分光から見た高密度ポリエチレンの構造変化

比江嶋祐介, 木田拓充, 新田晃平

次世代ポリオレフィン総合研究 8 77 2014年11月

　前のページ -次のページ　

<木田 拓充>

論文 - 木田 拓充

<木田　拓充>

論文 - 木田　拓充