共查询到19条相似文献,搜索用时 140 毫秒
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为了了解PET球晶的拉伸性能与球晶结构的关系以及无定形PET的取向和结晶,我们采取了两条不同的路线来制备样品:(1)先用溶液浇铸成膜的办法制备具有正球晶、负球晶或非常球晶的薄膜,然后进行单轴拉伸。电子显微图象及电子衍射证明,球晶的拉伸性能与C轴和球晶半径方向的夹角有关,夹角愈大拉伸愈困难;(2)先制备无定形的薄膜,然后在玻璃化温度附近进行单轴拉伸以获得C轴取向,再在215℃退火,使之结晶。电子衍射图证明,这样制备的样品具有高度的C轴取向。DSC结果表明,结晶的完善程度远比球晶的为高。 相似文献
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拉伸取向是合成纤维生产过程中的重要环节,几乎所有的合成纤维都须要经过拉伸过程。至目前为止,对高聚物本体结晶过程的研究已有了很多的工作,但有关拉伸取向后的纤维结晶过程却研究得很少.聚对苯二甲酸乙二酯的分子链比较刚性,当它从熔融状态骤冷淬火时容易得到完全透明的非晶态聚合物(薄膜或纤维).有许多工作业已证实, 相似文献
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双轴取向PET薄膜结晶、织构与超结构的研究 总被引:1,自引:0,他引:1
二类市售12μPET薄膜,即平衡膜与强力膜,应用作者提出的FRS-XRSA与传统的PF以及SAXS进行了比较全面的结构研究。从而获得了有关这些薄膜的结晶、织构与超结构的重要信息与参数,例如:结晶度、晶粒度、(Akl)晶面取向分布全貌与平均取向因子、长周期、晶区尺度、非晶区尺度及电子密度经向分布函数等。这些结构的信息既记录了加工的工艺过程,又对薄膜的各种重要物性,如力学、光学、热学、化学和表面等性质起着决定性的作用。这二类薄膜均可归属于(MT,100)共面、c-晶轴M、T双轴取向的平衡膜或非平衡膜。最后应指出,X-射线法是研究择优取向聚合物结晶、织构与超结构的极为重要的手段。 相似文献
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G. C. Adams 《Journal of Polymer Science.Polymer Physics》1971,9(7):1235-1241
The literature on polymer morphology contains many studies of structural and orientation changes occurring upon uniaxial stretching of films and fibers, but it has only an occasional reference to such studies on biaxially stretched film. This paper presents data on a structural change due to simultaneous biaxial stretching up to 6 × 6 stretch ratio of quenched linear polyethylene slightly below the melting temperature. At low stretch ratios the b axis of the orthorhombic unit cell orients predominantly in the biaxial plane of stretching or film plane. At higher than 4 × 4 stretch ratio, a second crystal orientation appears which is a (110) orientation in the film plane. Differential scanning calorimetry scans show two melting peaks occurring concurrently with diffraction effects of two crystal orientations. The evidence for two populations of crystals differing in orientation are discussed in the light of current concepts of folded-chain lamellae and their fragmentation with elongation. 相似文献
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Richard J. Pazur Robert E. Prud'homme 《Journal of Polymer Science.Polymer Physics》1994,32(8):1475-1484
The orientational states induced upon two-step biaxially stretching low-density polyethylene at 25°C have been investigated. A pole figure analysis of the (200), (020), and (002) crystalline planes has been employed to elucidate the evolution of the molecular crystalline orientation as a function of biaxial stretching. The initial uniaxial-like orientation induced along the extrusion direction of the films was gradually lost upon transverse stretching and, consequently, replaced by a biaxial orientation as suggested by the orientation functions. In these cases, the a crystallographic axis was observed to be strongly oriented along the film normal, thus confining the c and b axes to the film plane. The pole figures clearly indicate that the c and b axes are preferentially aligned 45° with respect to the stretching directions. This unique orientational state of the orthorhombic unit cell of polyethylene has been termed a biaxial-double orientation. Birefringence measurements on the biaxial samples indicated that the amorphous and crystalline regions are simultaneously biaxially oriented. The evolution of the crystalline orientation as a function of stretching was conveniently followed on a White/Spruiell orientation triangle. Quantification was hindered, however, by the presence of different crystal populations in the biaxially stretched samples. © 1994 John Wiley & Sons, Inc. 相似文献
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Ryo Oono Keizo Miyasaka Kinzo Ishikawa 《Journal of Polymer Science.Polymer Physics》1973,11(8):1477-1488
The isothermal crystallization of natural rubber was investigated under biaxial stretching. A marked planar orientation of crystals occurs in such a way that the (010) plane orients parallel to the film plane. The rate of crystallization increases with the biaxial stretching ratio, and the Avrami exponent n decreases. At the highest extension, n becomes less than unity. The equilibrium degree of crystallinity decreases with the stretching ratio. The crystallinity was less than 10% for the highest extension. The melting behavior is similar to that in uniaxial stretching. 相似文献
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Hiren V. Shah Jerry I. Scheinbeim Georgia A. Arbuckle 《Journal of Polymer Science.Polymer Physics》1999,37(6):605-614
Poly(p‐phenylene vinylene) or PPV is gaining increasing importance because of its superior electroluminescent efficiency and electrical conductivity. The most widely followed synthetic route for PPV involves synthesis of a precursor polymer using a sulfonium monomer salt. Previous studies have proven that the monomer salt which contains cyclic sulfonium groups yields better quality PPV than when the monomer containing dialkyl sulfonium groups is used. The structure of PPV synthesized using cyclic sulfonium precursor has not been as widely reported as that synthesized using dialkyl sulfonium monomer. In the current work, the structure of PPV, synthesized using a cyclic viz. tetrahydrothiophenium monomer salt, has been studied in detail using the wide angle X‐ray diffraction (WAXD) technique. The study reveals that even in the cast (unstretched) form, PPV shows considerable biaxial orientation in the plane of the film. This preferred orientation is found to occur during the casting process and is independent of the solvent used and casting substrate. On stretching these films to a final draw ratio of 7 : 1, this biaxial orientation is transformed into uniaxial orientation with nematic ordering of PPV chains along the stretch direction and PPV chains assuming three preferred orientations in the plane of the film. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 605–614, 1999 相似文献
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Hill MR Lee EY Russell JJ Wang Y Lamb RN 《The journal of physical chemistry. B》2006,110(18):9236-9240
Magnesium oxide thin films have been deposited with use of single source chemical vapor deposition (SSCVD). The resultant films were examined by using transmission electron microscopy, X-ray texture analysis, and pole figure analysis. Due to the nature of the chemical reactions occurring at the surface during SSCVD growth, which result in a high growth rate/low flux environment, films of (111) orientation have been achieved without an amorphous underlayer, an unusual result for films of this orientation. Moreover the films have a strong degree of biaxial texturing in the x-y plane as found with X-ray texture analysis. These findings have important implications for buffer layers in perovskite thin film devices. The mechanism producing these structures has been revealed by using TEM and is discussed here. 相似文献
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Gagik Ghazaryan Karlheinz Hausmann Theo A. Tervoort 《Journal of polymer science. Part A, Polymer chemistry》2020,58(3):446-454
Current state-of-the-art packaging films typically consist of solid-state stretched multilayer polymer systems, in which each of the polymer layers provides a specific property. Often these polymer film layers are incompatible and need to be glued together by so-called “tie layers.” In this article, we apply a novel biaxial orientation technique to examine the effect of solid-state biaxial stretching on the adhesive behavior of a model multilayer system consisting of poly(ethylene terephthalate) and isotactic polypropylene, as an example of two typical incompatible base layers, glued together by a common tie layer. Two main factors affecting the adhesion, the temperature at which the biaxial stretching is performed and the thickness of the tie layer, are discussed in detail. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 446–454 相似文献
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The variations in the molecular orientation of uniaxially drawn rigid‐rod polyimide films were systematically characterized in all three dimensions with polarized attenuated total reflection/Fourier transform infrared spectroscopy. The second‐order orientation coefficients were directly deduced from the anisotropy in IR absorptions of particular bands. With the draw ratio increasing, the state of the molecular orientation changed from being nearly planar to completely uniaxial via biaxial orientation, and the degree of orientation was much larger than that of a semirigid polyimide having an ether linkage at the same draw ratio, which originated from the rigid‐rod structure. In addition, the imide planes were rotationally oriented to the out‐of‐plane direction of the film geometry. Furthermore, the relationship between the molecular chain orientation and the in‐plane birefringence in the biaxial orientation state was examined. The intrinsic birefringence was estimated from biaxial orientation films to be 0.33 at a wavelength of 1307 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 418–428, 2003 相似文献
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《Liquid crystals》2000,27(4):459-465
Polymer dispersed discotic liquid crystals (PDDLCs) were prepared using the hexa-n-octanoate of rufigallol (RHO) and three polymer matrices: polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA). The molecular orientation of RHO in stretched PDDLC films was characterized by means of infrared dichroism. It was found that the stretching of films that contain RHO in both the columnar D1 and crystalline phase can effectively align columns of RHO along the stretching direction, with the short axes of the rigid cores lying in the plane of the film. By contrast with stretched polymer dispersed nematic liquid crystals, no orientation of RHO is induced for films stretched with RHO in the isotropic phase, followed by rapid cooling to room temperature. However, if stretched films are cooled under strain into the columnar D1 phase, orientation of RHO can develop with time. 相似文献
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A biaxial stretching equipment was designed and constructed to enable fundamental studies of the relationship between film processing conditions and structures of oriented film products. With programmable drive motors and scissorlike mechanism, all stretching modes, including uniaxial stretching with constant and free width, simultaneous and sequential biaxial stretching, can be applied to a square-shaped sheet. Parameters related to film stretching manufacturing, such as temperature, draw ratio and stretching speed can be set independently to meet the requirement of different polymers. The force information during stretching is recorded by two miniature tension sensors in two directions independently, which can monitor the mechanical stimulus and stress response. Using this equipment, experiments are conducted to investigate the influence of stretching parameters on the structure of polypropylene films, which provides an effective method to tailor the processing conditions to obtain the films with desired properties. 相似文献