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Shuichi Nojima - One of the best experts on this subject based on the ideXlab platform.
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Crystallization of double crystalline block copolymer/crystalline homopolymer blends: 1. Crystalline Morphology
Polymer, 2013Co-Authors: Satoru Gondo, Takuya Sakurai, Satoshi Osawa, Shuichi NojimaAbstract:Abstract The crystalline Morphology formed in binary blends of poly(e-caprolactone)- block -polyethylene (PCL- b -PE) copolymers and PCL homopolymers has been examined using synchrotron small-angle X-ray scattering (SR-SAXS) and differential scanning calorimetry (DSC) as a function of the homopolymer fraction in the blend. The PE block crystallized first on quenching from a Lamellar microdomain structure to set a hard Lamellar Morphology (PE Lamellar Morphology) in the blend, followed by the crystallization of PCL chains ( i.e ., PCL homopolymers + PCL blocks). Two binary blends were studied by considering the miscible state of PCL homopolymers in the microdomain structure: when the PCL homopolymers were uniformly mixed with PCL blocks, they formed a mixed crystal. When the PCL homopolymers were localized between PCL blocks in the microdomain structure, DSC results suggested the possible formation of separate PCL crystals in the PE Lamellar Morphology. The effect of the advance crystallization of PE blocks on the subsequent crystallization of PCL chains was discussed as compared with the crystalline Morphology formed in PCL- block -polybutadiene copolymer/PCL homopolymer blends, where the crystallization of PCL chains started directly from a microdomain structure without forming the hard Lamellar Morphology.
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crystallization of poly ɛ caprolactone blocks confined in crystallized Lamellar Morphology of poly ɛ caprolactone block polyethylene copolymers effects of polyethylene crystallinity and confinement size
Polymer Journal, 2013Co-Authors: Takuya Sakurai, Hikaru Nagakura, Satoru Gondo, Shuichi NojimaAbstract:We investigated the crystallization behavior and crystal orientation of poly(ɛ-caprolactone) (PCL) blocks confined in the polyethylene (PE) Lamellar Morphology of PCL-block-PE (PCL-b-PE) with different PE crystallinities χPE and PCL layer thicknesses dPCL. We found that the crystallization behavior of PCL blocks in PCL-b-PE with higher χPE and smaller dPCL was different from that in other PCL-b-PE copolymers. In addition, the orientation of PCL crystals significantly changed with changing crystallization temperature in PCL-b-PE with higher χPE and smaller dPCL, whereas it did not change in PCL-b-PE with lower χPE or larger dPCL.
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crystal orientation of poly ɛ caprolactone blocks confined in crystallized polyethylene Lamellar Morphology of poly ɛ caprolactone block polyethylene copolymers
Polymer, 2010Co-Authors: Tomoki Higa, Hikaru Nagakura, Takuya Sakurai, Shuichi NojimaAbstract:Abstract The crystal orientation of poly(ɛ-caprolactone) (PCL) blocks in PCL-block-polyethylene (PE) copolymers has been investigated using two-dimensional small-angle X-ray scattering (2D-SAXS) and 2D wide-angle X-ray diffraction (2D-WAXD) as a function of crystallization temperature Tc and thickness of PCL layers dPCL. The PCL blocks were spatially confined in the solid Lamellar Morphology formed by the crystallization of PE blocks (PE Lamellar Morphology), an alternating structure of crystallized PE lamellae and amorphous PCL layers. This confinement is expected to be intermediate between hard confinement by glassy Lamellar microdomains and soft confinement by rubbery ones, because the crystallized PE lamellae consist of hard PE crystals covered with amorphous (or soft) PE blocks. The 2D-SAXS results showed uniaxial orientation of the PE Lamellar Morphology after applying the rotational shear to the sample. Therefore, it was possible to investigate crystal orientation of PCL blocks within the oriented PE Lamellar Morphology. The 2D-WAXD results revealed that the c axis of PCL crystals (i.e., stem direction of PCL chains) was parallel to the Lamellar surface normal irrespective of Tc when 16.5 nm ≥ dPCL ≥ 10.7 nm. However, it changed significantly with changing Tc when dPCL = 8.8 nm; the c axis was perpendicular to the Lamellar surface normal at 45 °C ≥ Tc ≥ 25 °C while it was almost random at 20 °C ≥ Tc ≥ 0 °C. These results suggest that the PE Lamellar Morphology plays a similar role to glassy Lamellar microdomains regarding spatial confinement against subsequent PCL crystallization.
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Crystal Orientation of Poly(ε-caprolactone) Blocks Confined in Crystallized Lamellar Morphology of Poly(ε-caprolactone)-block-Polyethylene Copolymers. 2. Analysis of Experimental Results
2010Co-Authors: Hikaru Nagakura, Tomoki Higa, Shuichi NojimaAbstract:Introduction We have reported the experimental results for crystal orientation of poly(e-caprolactone) (PCL) blocks spatially confined in the solid Lamellar Morphology formed by the crystallization of polyethylene (PE) blocks (PE Lamellar Morphology) in PCL-b-PE copolymers. In this report, we analyze the experimental results, and crystal orientation of PCL blocks was derived as a function of crystallization temperature Tc and confinement size dPCL.
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composition dependence of crystallized Lamellar Morphology formed in crystalline crystalline diblock copolymers
Polymer, 2007Co-Authors: Shuichi Nojima, Hiroshi IkedaAbstract:Abstract We have investigated the crystallized Morphology formed at each temperature Tc (20 °C ≤ Tc ≤ 45 °C) in double crystalline poly(ɛ-caprolactone)-block-polyethylene (PCL-b-PE) copolymers as a function of composition (or volume fraction of PE blocks ϕPE) by employing small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) techniques. When PCL-b-PE with ϕPE ≤ 0.58 was quenched from a microphase-separated melt into Tc, the crystallization of PE blocks occurred first to yield an alternating structure consisting of thin PE crystals and amorphous PE + PCL layers (PE Lamellar Morphology) followed by the crystallization of PCL blocks, where we can expect a competition between the stability of the PE Lamellar Morphology (depending on ϕPE) and PCL crystallization (on Tc). Two different morphologies were formed in the system judging from a long period. That is, the PCL block crystallized within the existing PE Lamellar Morphology at lower Tc ( 35 °C) to result in a significant increase of the long period. However, the temperature at which the Morphology changed was almost independent of ϕPE. For PCL-b-PE with ϕPE ≥ 0.73, on the other hand, the Morphology after the crystallization of PE blocks was preserved at every Tc investigated.
Garth L Wilkes - One of the best experts on this subject based on the ideXlab platform.
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comparison of Lamellar thickness and its distribution determined from d s c saxs tem and afm for high density polyethylene films having a stacked Lamellar Morphology
Polymer, 1997Co-Authors: Hongyi Zhou, Garth L WilkesAbstract:Lamellar thickness and its distribution in high-density polyethylene (HDPE) films having a well-defined stacked Lamellar Morphology were investigated by using differential scanning calorimetry (d.s.c.), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). It was found that the most probable Lamellar thicknesses from SAXS and TEM agrees very well; however, they do not agree with those values obtained from d.s.c. and AFM. It is pointed out that the use of d.s.c. as a tool to determine Lamellar thickness and its distribution is so sensitive to the rate of heating in the d.s.c. experiments and the parameters in the Gibbs-Thomson equation that it is not believed to be suitable for routine quantitative analysis.
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orientation anisotropy of the mechanical α relaxation of high density polyethylene films having a well defined stacked Lamellar Morphology
Macromolecules, 1997Co-Authors: Hongyi Zhou, Garth L WilkesAbstract:Dynamic mechanical experiments were conducted on melt-extruded uniaxially oriented high- density polyethylene films having a well-defined stacked Lamellar Morphology. Samples were cut at different angles with respect to the original machine direction (MD) and tested by increasing the temperature from 20 to 130 °C at a heating rate of 0.5 °C/min in the frequency range from 0.01 to 10 Hz. Samples before and after the dynamic mechanical tests were also investigated by using WAXS, SAXS, and DSC. Oscillating parallel (0°) and perpendicular (90°) to the MD gave rise to a single tan δ dispersion peak, while oscillating at angles between the above two extremes generated a secondary dispersion peak at lower temperatures, with a maximum relaxation strength occurring at 45° orientation. It was concluded that, for the 0 and 90° orientations, the mechanical dispersion arises essentially from the crystalline phase, and it contains the contributions of earlier recognized intraLamellar (αI) and intracrystalline (αII) rel...
Eric Baer - One of the best experts on this subject based on the ideXlab platform.
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the effect of confined crystallization on high density poly ethylene Lamellar Morphology
Polymer, 2014Co-Authors: Guojun Zhang, Joseph Dooley, Steve Jenkins, Eric BaerAbstract:Abstract High-density polyethylene (HDPE) was co-extruded against high glassy transition temperature (Tg) polycarbonate (PC) to fabricate multilayer films. Melt and recrystallization experiments were conducted on these extruded films to study the effects of isothermal recrystallization temperature and layer thickness on HDPE lamellae orientation. WAXS and AFM were used to demonstrate Lamellar Morphology of HDPE layers. We report that HDPE lamellae show twisted Morphology in 30 nm thin layers after confined crystallization at a high temperature (128 °C). It may be the first time that anyone has created such twisted Lamellar Morphology with HDPE in such a thin layer. Similar twisted Morphology of HDPE was also observed when HDPE was coextruded with another high Tg glassy polymer, polysulfone (PSF). Interestingly, the twisted HDPE Lamellar Morphology associated with an increased crystallinity improves both the oxygen and water vapor barrier properties of the multilayer films.
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The effect of confined crystallization on high-density poly(ethylene) Lamellar Morphology
Polymer, 2014Co-Authors: Guojun Zhang, Joseph Dooley, Patrick C. Lee, Steve Jenkins, Eric BaerAbstract:High-density polyethylene (HDPE) was co-extruded against high glassy transition temperature (Tg) polycarbonate (PC) to fabricate multilayer films. Melt and recrystallization experiments were conducted on these extruded films to study the effects of isothermal recrystallization temperature and layer thickness on HDPE lamellae orientation. WAXS and AFM were used to demonstrate Lamellar Morphology of HDPE layers. We report that HDPE lamellae show twisted Morphology in 30 nm thin layers after confined crystallization at a high temperature (128 C). It may be the first time that anyone has created such twisted Lamellar Morphology with HDPE in such a thin layer. Similar twisted Morphology of HDPE was also observed when HDPE was coextruded with another high Tg glassy polymer, polysulfone (PSF). Interestingly, the twisted HDPE Lamellar Morphology associated with an increased crystallinity improves both the oxygen and water vapor barrier properties of the multilayer films. © 2013 Elsevier Ltd. All rights reserved.
Siyuan Cheng - One of the best experts on this subject based on the ideXlab platform.
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saxs waxs dsc studies on crystallization of a polystyrene b poly ethylene oxide b polystyrene triblock copolymer with Lamellar Morphology and low glass transition temperature
European Polymer Journal, 2003Co-Authors: Junting Xu, Jianjun Yuan, Siyuan ChengAbstract:Abstract Crystallization of a polystyrene-b-poly(ethylene oxide)-b-polystyrene (S–EO–S) triblock copolymer, S40EO136S40, with Lamellar Morphology in the melt and low glass transition temperature (Tg=47 °C) of the S block was studied. The triblock copolymer was cooled from ordered melt and isothermal crystallization was conducted at crystallization temperatures (Tc) near the Tg of the S block. It is found that crystallization behavior of S40EO136S40 strongly depends on Tc. When Tc is far below Tg, an Avrami exponent n=0.5 is observed, which is attributed to diffusion-controlled confined crystallization. As Tc slightly increases, the Avrami exponent is 1.0, indicating that crystallization is confined and crystallization rate is determined by the rate of homogeneous nucleation. When Tc is just below the Tg of the S block, crystallization tends to become breakout and accordingly Avrami exponent changes from 1.0 to 3.2. Crystallinity and melting temperature of the EO block in breakout crystallization are slightly higher than those in confined crystallization. Time-resolved small and wide angle X-ray scattering (SAXS/WAXS) were used to monitor isothermal crystallization of S40EO136S40. It shows that the long period is constant in confined crystallization, but it gradually increases during breakout crystallization. WAXS result reveals that confined or breakout crystallization has no effect on the crystal structure of the EO block.
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SAXS/WAXS/DSC studies on crystallization of a polystyrene-b-poly(ethylene oxide)-b-polystyrene triblock copolymer with Lamellar Morphology and low glass transition temperature
European Polymer Journal, 2003Co-Authors: Junting Xu, Jianjun Yuan, Siyuan ChengAbstract:Abstract Crystallization of a polystyrene-b-poly(ethylene oxide)-b-polystyrene (S–EO–S) triblock copolymer, S40EO136S40, with Lamellar Morphology in the melt and low glass transition temperature (Tg=47 °C) of the S block was studied. The triblock copolymer was cooled from ordered melt and isothermal crystallization was conducted at crystallization temperatures (Tc) near the Tg of the S block. It is found that crystallization behavior of S40EO136S40 strongly depends on Tc. When Tc is far below Tg, an Avrami exponent n=0.5 is observed, which is attributed to diffusion-controlled confined crystallization. As Tc slightly increases, the Avrami exponent is 1.0, indicating that crystallization is confined and crystallization rate is determined by the rate of homogeneous nucleation. When Tc is just below the Tg of the S block, crystallization tends to become breakout and accordingly Avrami exponent changes from 1.0 to 3.2. Crystallinity and melting temperature of the EO block in breakout crystallization are slightly higher than those in confined crystallization. Time-resolved small and wide angle X-ray scattering (SAXS/WAXS) were used to monitor isothermal crystallization of S40EO136S40. It shows that the long period is constant in confined crystallization, but it gradually increases during breakout crystallization. WAXS result reveals that confined or breakout crystallization has no effect on the crystal structure of the EO block.
Rufina G. Alamo - One of the best experts on this subject based on the ideXlab platform.
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Lamellar Morphology of random metallocene propylene copolymers studied by atomic force microscopy
Polymer, 2004Co-Authors: Ian L. Hosier, Rufina G. AlamoAbstract:Four sets of propylene based random copolymers with co-units of ethylene, 1-butene, 1-hexene and 1-octene, and a total defect content up to similar to 9 mol% (including co-unit and other defects), were studied after rapid and isothermal crystallization. Etched film surfaces and ultrarnicrotomed plaques were imaged so as to enhance contrast and minimize catalyst and co-catalyst residues. While increasing concentration of structural irregularities breaks down spherulitic habits, the formation of the gamma polymorph has a profound effect on the Lamellar Morphology. Lamellae grown in the radial axis of the spherulite and branches hereon are replaced in gamma-rich copolymers with a dense array of short lamellae transverse or tilted to the main structural growth axis. This is the expected orientation for gamma iPP branching from a seeds. Spherulites are formed in copolymers with non-crystallizable units ( 1-hexene and 1-octene) up to similar to 3 mol% total defect content and were observed up to similar to 6 mol% in those with partially crystallizable comonorners (ethylene and 1-butene). However, lamellae were observed in all the copolymers analyzed, even in the most defective ones, highlighting the important role of the gamma polymorph in propagating Lamellar crystallites in poly(propylenes) with a high concentration of defects. Long periods measured from AFM and SAXS are comparatively analyzed.
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Lamellar Morphology of random metallocene propylene copolymers studied by atomic force microscopy
Polymer, 2004Co-Authors: Ian L. Hosier, Rufina G. Alamo, J.s. LinAbstract:Four sets of propylene based random copolymers with co-units of ethylene, 1-butene, 1-hexene and 1-octene, and a total defect content up to ∼9mol% (including co-unit and other defects), were studied after rapid and isothermal crystallization. Etched film surfaces and ultramicrotomed plaques were imaged so as to enhance contrast and minimize catalyst and co-catalyst residues. While increasing concentration of structural irregularities breaks down spherulitic habits, the formation of the gamma polymorph has a profound effect on the Lamellar Morphology. Lamellae grown in the radial axis of the spherulite and branches hereon are replaced in γ-rich copolymers with a dense array of short lamellae transverse or tilted to the main structural growth axis. This is the expected orientation for γ iPP branching from α seeds. Spherulites are formed in copolymers with non-crystallizable units (1-hexene and 1-octene) up to ∼3mol% total defect content and were observed up to ∼6mol% in those with partially crystallizable comonomers (ethylene and 1-butene). However, lamellae were observed in all the copolymers analyzed, even in the most defective ones, highlighting the important role of the gamma polymorph in propagating Lamellar crystallites in poly(propylenes) with a high concentration of defects. Long periods measured from AFM and SAXS are comparatively analyzed. © 2004 Elsevier Ltd. All rights reserved.
