The laser-Raman spectrum of polyethylene

Gall, Markus; Hendra, P.J.; Peacock, O.J.; Cudby, M.E.A.; Willis, H.A.

doi:10.1016/0584-8539(72)80118-1

Cited by 138 publications

(55 citation statements)

References 21 publications

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“…2. The Raman bands of the C-C stretching modes in PE are listed in Table 2 [24,25,38,39]. The anti-symmetric (1063 cm −1 ) and symmetric (1130 cm −1 ) stretching modes correspond to the vibrations of carbon atoms along and perpendicular to the molecular chain, respectively.…”

Section: Elsevier_jpol_17488mentioning

confidence: 99%

“…Raman scattering is an optical technique that provides a complementary approach to IR absorption when transparent and very thin (typically <100 µm thickness) films are required. In addition, it is advantageous to use Raman spectroscopy because the vibrations of the skeletal C-C bonds in main chains are directly observed [20,25]. Because the C-C stretching vibration is strongly Raman active, microenvironments of the polymer chains are probed by the spectral shifts [26,27].…”

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confidence: 99%

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

Kida

Oku

Hiejima

et al. 2015

Polymer

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Semi-crystalline polymers such as polyethylene (PE) and polypropylene (PP) show complicated morphologies composed of a mixture of crystalline and amorphous phases. The diversity in the structure with a wide range of length scales is responsible for the durability or high toughness of semi-crystalline polymers [1,2].When a high-density polyethylene (HDPE) specimen is uniaxially drawn, the elastic deformation is followed by double yield points referred to as the first and the second yields. During such dual plastic deformations, large-scale transformation of the semi-crystalline morphology takes place, and collapse of the spherulite structures, necking of the sample specimens, and rearrangement of the lamellar crystals and the polymer chains have been observed [1][2][3][4][5][6]. Although various models, such as the lamellar local-melting and recrystallization model [4,7], and the lamellar cluster model [3,[8][9][10], have been proposed for the deformation mechanism, such complicated changes in the hierarchical structures of semicrystalline polymers are still controversial.Spectroscopic techniques have been applied for the orientational behavior of PE during elongation [11][12][13][14][15][16][17]. The infrared (IR) spectroscopy has been applied intensively, and it has been established that the molecular chains in the crystalline and amorphous phases orientate toward the draw direction [11][12][13][14]. It has also been demonstrated that the orientation proceeds rapidly after the first yield, and gradually in the neck-propagation and the strain-hardening regions.However, the IR spectroscopy gives one orientation parameter 〈P 2 〉 which corresponds to the averaged orientation. For PE, the vibrations of the side chains, such as CH 2 twisting and wagging, are IR-active, and the skeletal vibrations of the C-C bonds are IR-inactive, then the load sharing on the polymer chains could not be directly observed with the IR spectroscopy.Raman spectroscopy has several advantages to investigate the deformation behavior of polymeric materials [18][19][20][21][22][23][24]: it is applicable to opaque and thick samples, and molecular environments can be separately detected for both the crystalline and the amorphous phases. Raman scattering is an optical technique that provides a complementary approach to IR absorption when transparent and very thin (typically <100 µm thickness) films are required. In addition, it is advantageous to use Raman spectroscopy because the vibrations of the skeletal C-C bonds in main chains are directly observed [20,25]. Because the C-C stretching vibration is strongly Raman active, microenvironments of the polymer chains are probed by the spectral shifts [26,27]. Polarized Raman spectroscopy gives not only a measure of the average orientation, which is obtained by the usual spectroscopies such as birefringence and IR dichrom, but also the orientation distribution function (ODF, N(θ)) [28][29][30]. In the yielding region where the neck of the specimen is formed, complicated deformation mechanism is expect...

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Section: Elsevier_jpol_17488mentioning

confidence: 99%

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confidence: 99%

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

Kida

Oku

Hiejima

et al. 2015

Polymer

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“…tic of a Fermi resonance between the CH 2 symmetric stretch and the overtone of the methylene bending mode, [28] is clearly present (see full-line arrows in Fig. 1c).…”

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confidence: 88%

“…1c) and can be assigned to the symmetric and antisymmetric CH 2 stretching modes of the polymer, respectively. [28,29] Also, the shoulder at about 2930 cm -1 , characteris- II polymerization sites, before the impregnation step (Scheme 1a). b) SEM image of an isolated silica microfiber covered by a uniform PE coating, obtained by performing an in situ ethylene polymerization (100°C, P(C 2 H 4 ) = 500 Torr, in static conditions for 5 h) on a CO pre-reduced Cr II /SiO 2 -microfiber system (Scheme 1d).…”

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confidence: 98%

Polyethylene Microtubes from Silica Fiber‐based Polyethylene Composites Synthesized by an In Situ Catalytic Method

et al. 2006

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Most composite materials that consist of a thermoplastic matrix and a particulate filler are prepared by mechanical mixing of the components above the melting temperature of the polymer. Both organic (e.g., poly-p-(phenylene terephthalamide): PpPTA, polyethylene: PE) and inorganic (carbon, glass) fibers are extensively used as fillers for polymer-based composite materials; in particular, silica fibers combine the advantages of high tensile and compressive strengths with low cost, when compared to other competing fibers. [1,2] PE is one of the polymers most often used as a matrix because of its chemical resistance to solvents, low friction coefficient, hydrophobicity, and biocompatibility.[3]However, the mechanical mixing of components does not allow a fine and homogeneous dispersion of the filler, [4,5] and the resulting material is usually characterized by poor mechanical properties. In order to improve the properties of the resulting composite, a direct connection of the polymer with the surface of the filler is highly desirable. The polymerization filling technique (PFT) has proved very efficient in this regard. This method, initially investigated in Ziegler-Natta polymerization [6][7][8] and more recently developed for metallocene catalysis applied to a broad range of microfillers (e.g., kaolin, silica, carbon nanotubes, and graphite), [9][10][11] consists of anchoring a polymerization catalyst directly onto the filler surface, followed by its activation with a cocatalyst. The polymer chains grow directly from the catalytic species upon in situ addition of the monomer, and for this reason the polymer is formed in very close contact with the filler surface. Such a technique leads to a much more uniform filler distribution and a considerably enhanced interfacial adhesion, even at high filler content, compared to conventional mechanical techniques. In this work we present an original method to realize silicamicrofiber-based PE composites, which relies upon the in situ polymerization of ethylene from the gas phase, catalyzed by active Cr species anchored onto the surface of the silica microfibers. As a result, silica microfibers are homogeneously coated and interconnected by the PE chains grown in situ, forming a promising composite material without the need for post-synthesis processing. With respect to the PFT technique mentioned above, this "microprocessing" method is much cleaner because it does not require the use of cocatalysts and solvents. In particular, we demonstrate that by properly tuning the reaction conditions, it is possible to move from wellisolated to exclusively interconnected homogeneously PEcoated silica fibers, which finally constitute a real microcomposite material. The possibility of realizing a well-defined PE coating on silica microfibers can be used in an inverse way, i.e., by considering the silica microfibers as templates for the realization of PE microtubes. Here, we demonstrate that removal of the internal silica core from the composite material indeed results in the formation of PE ...

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“…When the stretching and compression stresses are applied on the molecular chains, the peak shifts have negative and positive values, respectively. The assignments of the Raman bands used in this work is listed in Table 1 [42,43]. The anti-symmetric (1063 cm -1 ) CC stretching and symmetric (1130 cm -1 ) CC stretching vibrational modes correspond to the skeletal chain vibration in the parallel and perpendicular to the molecular chain axis, respectively.…”

Section: Peak Shiftmentioning

confidence: 99%

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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The laser-Raman spectrum of polyethylene

Cited by 138 publications

References 21 publications

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

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

Polyethylene Microtubes from Silica Fiber‐based Polyethylene Composites Synthesized by an In Situ Catalytic Method

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

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