Evolution of lamellar orientation and crystalline texture of various polyethylenes and ethylene-based copolymers in plane-strain compression

Bartczak, Z.; Łężak, E.

doi:10.1016/j.polymer.2005.04.092

Cited by 63 publications

(83 citation statements)

References 30 publications

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“…At the same time, the 4‐point component quickly disappears. Such features of scattering pattern were found to be associated with heavily fragmented lamellae, where all crystalline fragments are progressively oriented with their normals along FD, yet still arranged in a chevron‐like pattern 37, 38. Such an arrangement was found to develop in deformed polyethylene due to heavy fragmentation of already kinked lamellae, related to advancing crystallographic slip within crystals and to an exhaustion and “lock” of deformation of adjacent amorphous layers, in which chains become stretched nearly to the extensibility limit.…”

Section: Resultsmentioning

confidence: 99%

“…Such an arrangement was found to develop in deformed polyethylene due to heavy fragmentation of already kinked lamellae, related to advancing crystallographic slip within crystals and to an exhaustion and “lock” of deformation of adjacent amorphous layers, in which chains become stretched nearly to the extensibility limit. This ultimate stretch results in a rapid increase of the stress, which triggers soon the fragmentation of lamella already thinned by crystallographic slip 37, 38. Fragmentation relieves partially constraints, which in turn allows more rotation of crystallites with the normal n towards FD and finally the formation of a new period along FD 37…”

Section: Resultsmentioning

confidence: 99%

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Plastic deformation behavior of β phase isotactic polypropylene in plane‐strain compression at elevated temperatures

Łężak¹,

Bartczak²

2007

J Polym Sci B Polym Phys

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Isotactic polypropylene (iPP) rich in β crystal modification was deformed by plane‐strain compression at T = 55–100 °C. The evolution of phase structure, morphology, and orientation were studied by DSC, X‐Ray, and SEM. The most important deformation mechanisms found were interlamellar slip operating in the amorphous layers, resulting in numerous fine deformation bands and the crystallographic slip systems, including the (110)[001]β chain slip and (110)[$1{\bar {1}}0$]β transverse slip. Shear within deformation bands leads to β→α solid state phase transformation in contrast to β→smectic transformation observed at room temperature. Newly formed α crystallites deform with an advancing strain by crystallographic slip mechanism, primarily the (010)[001]α chain slip. As a result of deformation and phase transformation within deformation bands β lamellae are locally destroyed and fragmented into smaller crystals. Deformation to high strains, above e = 1, brings further heavy fragmentation of lamellae, followed by fast rotation of crystallites with chain axis towards the direction of flow FD. This process, together with still active crystallographic slip, leads to the final texture with molecular axis of both crystalline β and α phase oriented along FD. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 92–108, 2008

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Plastic deformation behavior of β phase isotactic polypropylene in plane‐strain compression at elevated temperatures

Łężak¹,

Bartczak²

2007

J Polym Sci B Polym Phys

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“…Integrating the area under the DSC melt endotherm from 100 to 150°C yields heat of melt of 236.9, 113.0, 109.5 J/g for HDPE, UHMWPE, and PEX, respectively. Taking the heat of melt for a perfect PE crystal to be 293 J/g from [25,29,33,39,62,63] the percent crystallinity of the HDPE, UHMWPE, and PEX are 80.9, 38.6, and 37.4% respectively (Sobieraj et al [27] used 288.84 J/g). All of these values are summarized in Table 3.…”

Section: Thermomechanical Analysis and Differential Scanning Calorimetrymentioning

confidence: 99%

Influence of Molecular Conformation on the Constitutive Response of Polyethylene: A Comparison of HDPE, UHMWPE, and PEX

et al. 2007

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The current work presents the characterization and comparison of the mechanical response of three different industrial forms of polyethylene. Specifically, high-density polyethylene (HDPE), ultra high molecular weight polyethylene (UHMWPE), and cross-linked polyethylene (PEX) were tested in compression as a function of temperature (−75 to 100°C) and strain-rate (10 −4 to 2,600 s −1 ). The responses of UHMWPE and PEX are very similar, whereas HDPE exhibits some differences. The HDPE samples display a significantly higher yield stress followed by a flat flow behavior. Conversely UHMWPE and PEX both exhibit significant strain hardening after yield. The temperature and strain-rate dependence are captured by simple linear and logarithmic fits over the full range of conditions investigated. The yield behavior is presented in terms of an empirical mapping function that is extended to analytically solve for the mapping constant. The power-law dependence on strain-rate observed in some polymers is explained using this mapping function.

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“…independent of the degree of crystallinity or lamellar structure of the polymer, as well as independent of the conditions under which drawing takes place such as temperature and strain rate (for independence in relation to strain rate and temperature as shown previously by Hobeika et al [17] and Lezak and Bartczak [18]). An immediate corollary is that the crystal orientation does not depend directly on the deformation of the non-crystalline material, so that it is as if the crystals were embedded in a matrix whose deformation can accommodate the crystal slip processes.…”

Section: Discussionmentioning

confidence: 67%

The degree of crystalline orientation as a function of draw ratio in semicrystalline polymers: a new model based on the geometry of the crystalline chain slip mechanism

et al. 2015

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The orientation behaviour of a range of high density polyethylenes (PEs) drawn to different draw ratios has been investigated by measurements of optical birefringence and wide angle Xray diffraction (WAXS). Consistent with previous research, it can be concluded that birefringence relates to the overall degree of orientation of the amorphous and crystalline phases, and is described to a good approximation by the pseudo-affine deformation scheme.The WAXS results show that crystalline orientation is also related uniquely to the applied strain and moreover is independent of the characteristics of the polymer concerned. It is shown that the crystalline orientation follows a new model based on the geometry of the crystalline slip mechanism where the crystalline phase deforms affinely in the longitudinal drawing direction.

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Evolution of lamellar orientation and crystalline texture of various polyethylenes and ethylene-based copolymers in plane-strain compression

Cited by 63 publications

References 30 publications

Plastic deformation behavior of β phase isotactic polypropylene in plane‐strain compression at elevated temperatures

Plastic deformation behavior of β phase isotactic polypropylene in plane‐strain compression at elevated temperatures

Influence of Molecular Conformation on the Constitutive Response of Polyethylene: A Comparison of HDPE, UHMWPE, and PEX

The degree of crystalline orientation as a function of draw ratio in semicrystalline polymers: a new model based on the geometry of the crystalline chain slip mechanism

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