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1.
采用冻胶纺丝-超拉伸技术纺制了超高相对分子质量聚乙烯(UHMWPE)纤维。利用小角X光散射(SAXS)、广角X射线衍射(WAXD)及拉曼光谱等测试手段,研究了拉伸过程中UHMWPE纤维的结晶结构变化。结果表明:随拉伸的进行,纤维非晶区中分子链逐渐参与了结晶,纤维SAXS强度减弱,纤维结构变得紧密规整;纤维结晶长周期及结晶度随拉伸倍数的增加而增大,并趋于平衡,拉伸30倍后,纤维结晶长周期约为50 nm,结晶度约为67.5%;纤维横向晶粒平均尺寸随拉伸倍数的增加而变小,拉伸30倍后,趋于平衡,而纤维晶粒c轴方向的轴向晶粒尺寸随拉伸倍数的增加而变大。 相似文献
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超拉伸过程中UHMWPE纤维结构与性能的研究 总被引:1,自引:1,他引:0
利用密度梯度仪、声速取向仪、Instron材料强力仪、WAXD、DSC等手段 ,对超高相对分子质量聚乙烯 (UHMWPE)纤维在超拉伸过程中的结构和性能进行了测试研究。结果表明 ,不同拉伸倍数的UHMWPE纤维的结晶度、取向度、力学性能和熔融温度随着拉伸倍数的增大而增加 ;DSC图谱上的 Tm4 峰和WAXD分析证实了在超拉伸过程中UHMWPE纤维发生了正交晶相向六方晶相的转变 ,超拉伸后期结晶结构的变化对纤维的力学性能影响很大。 相似文献
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Fibers of ultrahigh molecular weight polyethylene (UHMW-PE) were prepared with the gel fiber drawing method, and the solvent and extraction solvent used were a general kerosene and gasoline, respectively. The thermal behaviors and mechanical properties of the fiber were studied using thermal analysis, a wide-angle X-ray diffractiometer, density, the sound orientation factor, as well as mechanical property measurement. The results showed that the morphology of macromolecular chains was changed from the folded state to an extendedcain structure with increasing of the drawing ratio. In addition, the crystal form of the fiber also changed. These changes were more evident while the drawing ratio exceeded 20. The tensile strength, similar to the modulus of the fibers, increases with an increasing draw ratio in the range that we researched, whereas the sonic velocity orientation factor and the degree of crystallinity increase slowly when the draw ratio is over 30. © 1996 John Wiley & Sons, Inc. 相似文献
4.
Fibers (strands) with various draw ratios were spun from the liquid crystalline state of a pure aromatic liquid crystalline copoly(ester amide) and the melts of its blend with polycarbonate. Scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC) were employed to investigate the structure and properties of the resulting fibers. Mechanical properties of the fibers were also evaluated. It was found that both the crystallite size and heat of fusion of the liquid crystalline polymer (LCP) increase steadily with draw ratio. However, the crystal-nematic transition temperature of the LCP is virtually unaffected by drawing. Moreover, heat of fusion of LCP is much smaller than that of isotropic condensation polymers despite the presence of very sharp diffraction peaks in WAXS measurements. These results are ascribed to the (semi)rigid rod nature of the LCP chains and the persistence of an ordered structure in the LCP melt, i.e., entropy effect. It was further observed that tensile modulus and tensile strength along fiber axis rise with draw ratio for the composite fibers. The elastic modulus of the composite fibers were found to be as high as 19 GPa and tensile strength reached 146 MPa with draw ratios below 40 and an LCP content of 30 wt%. Compared with the thermoplastic matrix, the elastic modulus and tensile strength of the in-situ composite have increased by 7.3 times and 1.4 times, respectively, with the addition of only 30 wt% LCP. This improvement in mechanical properties is attributed to fibrillation of the LCP phase in the blend and the increasing orientation of the LCP chains along the fiber axis during drawing. 相似文献
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A tensile drawing process under dielectric heating has been developed for polyoxymethylene. The influence of ambient temperature, electric field strength, and strain rate on the maximum draw ratio and the tensile modulus has been examined. Tubes possessing tensile moduli up to 63GPa were produced by the new drawing technique. It is speculated that the achievement of such ultrahigh moduli is due to the fact that the stress by drawing is used effectively to orient the molecular chains in the noncrystalline regions and at defect regions within the crystal lamellae. This is because these regions are heated to higher temperatures than the crystalline regions during dielectric heating. 相似文献
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The effects of melt spinning and cold drawing on structure development and resulting properties of poly (aryl ether ketone) (PAEK) have been investigated. Melt spun and subsequently cold drawn fibers were characterized by differential scanning calorimetry, wide angle X-ray diffraction, small angle X-ray diffraction, and birefringence techniques. At low take-up speeds, essentially amorphous fibers are produced. High take-up speeds result in development of crystallinity in the as-spun fibers. Cold drawing above the, Tg of PAEK causes further increase of crystallinity. Wide angle X-ray patterns indicate progressive alignment of chains along the fiber axis in as spun as well as in cold-drawn fibers with the draw down ratio and cold draw ratio. However, cold drawing was observed to broaden the WAXS peaks. SAXS patterns of cold drawn and fixed annealed fibers changed from two-point to four-point patterns indicating mosaic pattern formation of crystalline and amorphous regions. Mechanical properties including tensile strength, elongation at break, modulus, and yield strength were measured and correlated with fiber structure. Fracture surfaces of tensile tested fibers were observed using scanning electron microscopy and correlated with developed fiber structure. 相似文献
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以1-丁基-3-甲基咪唑氯盐([BMIM]Cl)为溶剂溶解聚丙烯腈(PAN)制成PAN纺丝原液,采用干喷湿法纺丝,经过凝固、预拉伸、沸水拉伸制得PAN纤维,对所得PAN纤维进行沸水再拉伸处理,研究了沸水再拉伸速率对PAN纤维结构和性能的影响。结果表明:PAN纤维中残留质量分数为4.38%的离子液体,为沸水再拉伸起到了增塑作用;随着沸水再拉伸速率的增大,PAN纤维的力学性能提高,断裂强度由2.69cN/dtex提高到4.33 cN/dtex,而断裂伸长率由26%减小到20%,纤维的玻璃化转变温度、晶区取向度、双折射率、结晶度、晶粒尺寸均增大。 相似文献
9.
Bhuvanesh Gupta Nilesh Revagade Nishat Anjum Bjrn Atthoff Jns Hilborn 《应用聚合物科学杂志》2006,100(2):1239-1246
Poly(lactic acid) fiber was prepared by dry‐jet‐wet spinning of the polymer from chloroform solution and with methanol as the precipitating medium. The as‐spun fiber was subsequently made into high strength fiber by two‐step process of drawing at a temperature of 90°C and subsequent heat setting in the temperature range of 120°C. The draw ratio had significant influence on the crystallinity and the tensile strength of the fiber. The fiber with the tenacity of 0.6 GPa and modulus of 8.2 GPa was achieved at a draw ratio of 8. The differential scanning calorimetry revealed an increase in the glass‐transition temperature with the increase in the draw ratio, which suggests the orientation of chains during the drawing process. The surface morphology of the filament as revealed by scanning electron microscopy shows that fibers are porous in nature, but a significant reduction in the porosity and pore size of the fiber was observed with the increase in the draw ratio. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1239–1246, 2006 相似文献
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David M. Berns Elizabeth Oyebode Benita Dair Peggy Cebe Malcolm Capel 《应用聚合物科学杂志》2001,82(14):3492-3504
The influence of zone drawing on bulk properties and structure of metallocene polyethylene (m‐PE) is reported. Two different m‐PE materials were subjected to tensile stresses above the yield point by zone drawing in the temperature range from 50 to 100°C. Drawn materials were characterized by using small‐ and wide‐angle X‐ray scattering (SAXS, WAXS), molecular retraction, and small‐angle light scattering (SALS). Structural changes were studied as a function of drawing temperature, engineering stress, and draw ratio. WAXS showed strong crystalline orientation in drawn samples, and only the orthorhombic crystal modification was observed. SAXS showed lamellar orientation in drawn samples. At low drawing temperatures of 50 or 60°C, draw ratio increased as a step function of stress. There is a stress barrier, which must be exceeded before high‐draw ratios can be achieved at these temperatures. At drawing temperatures of 70°C or above, the barrier stress is low enough that draw ratio increases nearly linearly as a function of stress. Below the stress barrier, spherulitic structure is observed by small‐angle light scattering (SALS). Elongation occurs via deformation of the interspherulitic amorphous phase. Molecular retraction was low for these samples, indicating mostly plastic deformation of the amorphous material. Above the stress barrier, SALS showed that spherulites are destroyed. Elongation occurs via deformation of the intraspherulitic amorphous phase. Molecular retraction for these samples was high, indicating elastic deformation of the amorphous material. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3492–3504, 2001 相似文献
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KwanHan Yoon Malcolm B Polk Byung G Min David A Schiraldi 《Polymer International》2004,53(12):2072-2078
The crystal structures of nylon‐6 and nylon‐6/clay fibers were investigated on annealing and drawing. Annealing increased the γ‐crystalline form of both fibers, as indicated by the DSC curves, and its effect was dominant in nylon‐6/clay fiber. On drawing, the γ‐crystalline form was easily converted into the α form in nylon‐6, whereas it was still observed at a relatively high spin‐draw ratio in nylon‐6/clay fiber. However, although the α‐crystal form was dominant in nylon‐6, the γ‐crystal form was dominant in nylon‐6/clay with annealing and drawing, on the basis of the XRD data. The fast crystallization rate of nylon‐6/clay compared with pure nylon‐6 was confirmed, on the basis of the Avrami exponent. The initial modulus of nylon‐6/clay fiber was 30 % higher than the neat nylon‐6 fiber. The reinforcing effect of clay on the dynamic storage modulus was observed. Copyright © 2004 Society of Chemical Industry 相似文献
12.
拉伸条件对高强PVA纤维结构和性能的影响 总被引:3,自引:1,他引:2
将聚乙烯醇(PVA)加入到二甲基亚砜(DMSO)和水(质量比94:6)的混合溶剂中,以甲醇为凝固剂,采用干湿法凝胶纺丝,经热拉伸和热定型后,制得高强度PVA纤维。探讨了拉伸工艺对高强PVA纤维结构和性能的影响。结果表明:对于负拉伸为40%,初拉伸2倍,220℃热拉伸9.9倍,热定型2 min的PVA纤维,纤维的结晶结构比较完善,断裂强度为17.8 cN/dtex,初始模量为310.7 cN/dtex;PVA纤维在光学显微镜下观察到的横纹反映出结晶聚集体的光学现象,横纹较多时,纤维的断裂强度和初始模量较高。 相似文献
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Masatsugu Mochizuki Madoka Hirano Yoshihiro Kanmuri Kazushige Kudo Yutaka Tokiwa 《应用聚合物科学杂志》1995,55(2):289-296
Using polycaprolactone (PCL) fibers drawn with various draw ratios, the effects of draw ratio on enzymatic degradation were studied in order to understand the influence of fine structure on biodegradation. Degradability of PCL fibers as monitored by total organic carbon (TOC) formation or weight loss decreased with increase in draw ratio due to higher crystalline content. There were some distinct features of degradation behavior among the fibers, because the fibers underwent significant change in molecular organization of the polymer, such as crystallinity and orientation, during drawing processes. From scanning electron microscopy (SEM) photographs showing that the enzyme preferentially attacked amorphous or less ordered regions rather than crystalline or more ordered regions of the fiber, spherulites were observed in the undrawn fiber, and on the other hand, fibrillar stripes along the fiber axis were observed in the drawn fibers, which suggest that the spherulites in the undrawn fiber were extended to be broken, and fibril structures were formed during the drawing processes. These SEM photographs suggest that there are differences of crystal structures in addition to crystallinity among the fibers with different draw ratio, which significantly affects the enzymatic degradation behavior of the fibers. The diameter of the fibers became gradually slim, macroscopically uniform, as enzymatic degradation proceeded although it was dependent on draw ratio. It is evident that the degradation proceeded in the crystalline regions as well as the amorphous regions. © 1995 John Wiley & Sons, Inc. 相似文献
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Jiacheng Zhang Yonggang Li Gang Ma Jiannan Ren Guibin Wang Shuling Zhang Mei Zhang Jiashuang Luan 《应用聚合物科学杂志》2023,140(4):e53365
The microstructure formation mechanism of melt-spun Poly(ether-ether-ketone) monofilaments during poststretching was investigated using in-situ wide-angle X-ray diffraction in combination with polarizing microscopy, differential scanning calorimetry and universal testing machine. As PEEK monofilaments were stretched at 210°C, the crystallinity and microcrystal size first increased during the insulation state (Is-S), then decreased during the poststretching state (Ps-S), and further increased during the postcooling state (Pc-S), at last were observed to selective orientation. At 210°C, the anisotropically aligned molecular chains reach a meritocratic orientation in the stress direction under 4.0 times drawing conditions, resulting in the highest tensile strength and modulus. As the stretching ratio increases, the crystallinity and microcrystal size first increase during Pc-S and then decrease due to the effect of the stretched molecular chains on crystal growth and the degree of tearing in the crystalline region. The molecular chains of PEEK monofilaments stretched by uniaxial stress are aligned more flatly and uniformly along the fiber axis. We hope that this work will provide advice and guidance for the industrial production of high-performance fibers. 相似文献
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In this work, the structure and drawability of dried formalized gel films prepared from the formalization of high molecular
weight polyvinyl alcohol (PVA) aqueous solutions were studied. Structure changes in PVA crystal were found in the formalized
samples, i.e., the spacing of the (100) plane for PVA crystal became much larger while that of the (020) plane became smaller,
indicating that some disordered crystals were formed from formalized PVA chains. The crystal relaxation temperature, Tαc, and its dependence on the draw ratio in formalized films were lower than those in original the PVA. Irrespective of the
lower crystalline properties and the crystal relaxation temperature, the drawability of formalized PVA films could not be
improved. The crystal orientation function, fc, decreased as the degree of formalization at a given draw ratio was increased, indicating that the acetal groups in the amorphous
region must be a hindrance to the drawing of the formalized PVA. These results implied that the drawability of PVA is not
only related to the properties of the crystalline region but also to those of the amorphous region. 相似文献
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Won Seok Lyoo Hyun Seok Lee Byung Chul Ji Sung Soo Han Kang Koo Sam Soo Kim Joon Ho Kim Joon‐Seok Lee Tae Won Son Won Sik Yoon 《应用聚合物科学杂志》2001,81(14):3471-3480
Melt‐spun poly(trimethylene terephthalate) (PTT) fibers were zone‐drawn and the structures and properties of the fibers were investigated in consideration of the spinning and zone‐drawing conditions. The draw ratio increased up to 4 with increasing drawing temperature to 180°C, at a maximum drawing stress of 220 MPa. Higher take‐up velocity gave lower drawability of the fiber. The PTT fiber taken up at 4000 rpm was hardly drawn, in spite of using maximum drawing stress, because a high degree of orientation had been achieved in the spinning procedure. However, an additional enhancement of birefringence was observed, indicating a further orientation of PTT molecules by zone drawing. The exotherm peak at 60°C disappeared and was shifted to a lower temperature with an increase in the take‐up velocity, which means that the orientation and crystallinity of the fiber increased. The d‐spacing of (002) plane increased with increasing take‐up velocity and draw ratio, whereas those of (010) and (001) planes decreased. In all cases, the crystal size increased with take‐up velocity and draw ratio. The cold‐drawn PTT fiber revealed a kink band structure, which disappeared as the drawing temperature was raised. The physical properties of zone‐drawn PTT fibers were improved as the draw ratio and take‐up velocity increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3471–3480, 2001 相似文献