Studies on high‐speed melt spinning of noncircular cross‐ section fibers. I. Structural analysis of as‐spun fibers

Flat fibers and hollow fibers were prepared through the high‐speed melt spinning of poly(ethylene terephthalate) (PET), and the structures of these fibers were compared with those of circular fibers. The cross‐sectional shape of each fiber changed to a dull shape in comparison with that of the respective spinning nozzle. The change in the cross‐sectional shape was slightly suppressed with an increase in the take‐up velocity. There was a significant development of structural variation in the cross section of flat fibers in that the molecular orientation and crystallization were enhanced at the edge. Despite the difference in the cross‐sectional shape, the structural development of flat, hollow, and circular fibers with increasing take‐up velocity showed almost similar behavior. Considering that the tensile stress at the solidification point of the spin line is known to govern the structure development of high‐speed spun PET fibers, it was speculated that the effects of the enhancement of cooling and air friction on the tensile stress at the solidification point cancel each other. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1575–1581, 2001     

Melt spun thermoresponsive shape memory fibers based on polyurethanes: Effect of drawing and heat‐setting on fiber morphology and properties

Thermoresponsive shape memory (SMP) fibers were prepared by melt spinning from a polyester polyol‐based polyurethane shape memory polymer (SMP) and were subjected to different postspinning operations to modify their structure. The effect of drawing and heat‐setting operations on the shape memory behavior, mechanical properties, and structure of the fibers was studied. In contrast to the as‐spun fibers, which were found to show low stress built up on straining to temporary shape and incomplete recovery to the permanent shape, the drawn and heat‐set fibers showed significantly higher stresses and complete recovery. The fibers drawn at a DR of 3.0 and heat‐set at 100°C gave stress values that were about 10 times higher than the as‐spun fibers at the same strain and showed complete recovery on repeated cycling. This improvement was likely due to the transformation brought about in the morphology of the permanent shape of the SMP fibers from randomly oriented weakly linked regions of hard and soft segments to the well‐segregated, oriented and strongly H‐bonded regions of hard‐segments. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2172–2182, 2007     

一次法混炼工艺对胎面磨耗性能的影响

胎面的耐磨性是评价成品轮胎性能优劣的一项重要指标,它取决于很多因素,但其中最关键的因素还是胎面的配方体系和胶料的混炼工艺。胶料的耐磨耗性能有磨损磨耗、疲劳磨耗、巻曲磨耗三种表现形式,本文主要从丰源轮胎推行的“一次法混炼工艺”针对炼胶工艺的提升与传统工艺进行对比,进而验证“一次法混炼工艺”所生产的胎面胶料对于胎面耐磨性的提升。     

光伏背板用PET老化性能研究

利用湿热老化、热氧老化对PET及使用该PET为基材的光伏背板进行处理,测定了老化后PET及背板的力学性能,并利用红外、DSC、粘度测试等分析方法研究了PET在上述老化过程中官能团、结晶度、分子量以及断裂伸长率的变化情况,并探讨了这些物性的变化与PET微观结构变化之间的联系.     

缝纫线型涤纶短纤维生产工艺探讨

结合缝纫线型涤纶短纤维高强低伸低收缩的质量要求,分析了提高短纤维强伸性能措施,提出通过更换喷丝板、提高纺丝速度、延长热定型时间,可提高短纤维强伸性能,生产出符合缝纫线要求的涤纶短纤维。     

Effect of winding speed on the structure and properties of as‐spun poly(trimethylene 2,6‐naphthalenedicarboxylate) fibers as compared to poly(ethylene terephthalate) fibers

We present a comparative study of melt spinning of poly(trimethylene 2,6‐naphthalenedicarboxylate) (PTN) and poly(ethylene terephthalate) (PET) fibers with respect to the effect of winding speed (2000–6000 m/min): Structural changes were followed by X‐ray analysis, calorimetry, and measurements of density, boiling water shrinkage, and birefringence. As‐spun PTN fibers exhibited a low degree of crystallinity at relatively low speeds (< 2000 m/min). An increase in winding speed up to 6000 m/min only resulted in a minor enhancement of crystallinity and orientation. The small change of structural parameters accounted for the fact that tenacity and modulus did not rise significantly with increasing winding speed, contrary to the PET fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2489–2497, 2002     

Melt‐spun polylactic acid fibers: Effect of cellulose nanowhiskers on processing and properties

Bio‐based continuous fibers were processed from polylactic acid (PLA) and cellulose nanowhiskers (CNWs) by melt spinning. Melt compounding of master batches of PLA with 10 wt % CNWs and pure PLA was carried out using a twin‐screw extruder in which compounded pellets containing 1 and 3 wt % of CNWs were generated for subsequent melt spinning. The microscopy studies showed that the fiber diameters were in the range of 90‐95 µm, and an increased surface roughness and aggregations in the fibers containing CNWs could be detected. The addition of the CNWs restricted the drawability of the fibers to a factor of 2 and did not affect the fiber stiffness or strength, but resulted in a significantly lower strain and slightly increased crystallinity. Furthermore, CNWs increased the thermal stability, creep resistance and reduction in thermal shrinkage of PLA fibers, possibly indicating a restriction of the polymer chain mobility due to the nanoscale additives. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure and property studies of poly(trimethylene terephthalate) high-speed melt spun fibers

Poly(trimethylene terephthalate) has been melt spun at various take-up velocities from 0.5 to 8 km/min to prepare fiber samples. The effect of take-up velocity on the structure and properties of as-spun fibers has been characterized through measurements of birefringence, density, wide-angle X-ray scattering, DSC melting behavior, tensile properties and boiling water shrinkage (BWS). The birefringence exhibits a maximum at take-up velocities between 3 and 4 km/min. The fiber samples spun at the lower take-up speeds have essentially amorphous structures, while the filaments prepared at a velocity range higher than 4 km/min all possess an obvious crystalline structure. With increasing take-up speed, a steady improvement in tensile strength, elongation to break, and BWS is found, whereas the initial modulus remains almost constant within the measurement error, over the entire take-up speed range between 0.5 and 8 km/min.     

Structure evolution of melt‐spun poly(vinyl alcohol) fibers during hot‐drawing

The drawability of melt‐spun poly(vinyl alcohol) (PVA) fibers and its structure evolution during hot‐drawing process were studied by differential scanning calorimetry (DSC), two dimensional X‐ray diffraction (2‐D WAXD) and dynamic mechanical analysis (DMA). The results showed that the water content of PVA fibers should be controlled before hot‐drawing and the proper drying condition was drying at 200°C for 3 min. PVA fibers with excellent mechanical properties could be obtained by drawing at 200°C and 100 mm/min. The melt point and crystallinity of PVA fibers increased with the draw ratio increasing. The 2‐D WAXD patterns of PVA fibers changed from circular scattering pattern to sharp diffraction point, confirming the change of PVA fibers from random orientation to high degree orientation. Accordingly, the tensile strength of PVA fibers enhanced by hot‐drawing, reaching 1.85 GPa when the draw ratio was 16. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

高速纺涤纶中空长丝的研制

通过对特殊喷丝板的设计和纺丝工艺的探讨 ,研究了影响高速纺涤纶中空长丝成形的主要因素 ,讨论了喷丝板的设计原则。结果表明 :纺丝速度为 2 .8～ 3.2 km/m in,纺制 POY中空纤维 ,卷绕正常 ,可满足后加工的要求 ;纺丝速度增加 ,中空度降低 ,熔体温度控制在 30 0～ 30 2℃ ;中空喷丝板设计时 ,微孔圆环形狭缝宽度小于 0 .15 mm ,表观拉伸比不能太大 ;POY中空度一般为 15 %～ 2 8% ,F DY的中空度可达 5 0 %。     

PET/EVA共混纤维的制备及其性能研究

将PET/EVA共混物切片在微型柱塞式纺丝机上进行熔融纺丝、拉伸等试验,对其纤维的结构和性能进行了分析。结果表明,随着EVA含量的增加,共混切片的纺丝性能下降;初生共混纤维的密度、机械性能、可拉伸性能下降;共混纤维的取向度、结晶度降低。     

Effect of jet stretch on polyacrylonitrile as‐spun fiber formation

In this article, the effect of jet stretch ratio on the extrudate die‐swell effect of polyacrylonitrile spinning solution and the structure and properties of as‐spun fibers was systematically analyzed by means of X‐ray diffraction (XRD), electron microprobe analysis, and the measurement of die‐swell ratio, boiling‐water shrinkage, porosity, mechanical properties analysis, etc. It revealed the formation mechanism of the die‐swell effect and spin orientation and its influences on the structure and properties of as‐spun fibers. It showed that with the increase of the jet stretch ratio the die‐swell ratio became smaller, both the degree of spin orientation and the crystallinity increased, the microstructure of as‐spun fibers became compact and homogeneous, and the cross section tended to be circular. As a result, the breaking tenacity of as‐spun fibers and resultant precursors all increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3348–3352, 2007     

Supramolecular morphology of two‐step,melt‐spun poly(lactic acid) fibers

Fibers of poly(lactic acid) produced by two‐step melt spinning have been studied. The morphology is elucidated with respect to the thermal and mechanical properties of fibers produced at cold‐draw ratios of 1–8. With atomic force microscopy and small‐angle X‐ray scattering, a fibrillar morphology is found, with microfibril diameters ranging from 30 to 60 nm. Shrinkage properties indicate that, with increasing draw ratio, the fibers undergo a transition from class 2 to class 1 within the classification proposed by Keller. A supramolecular model for the morphology of the fibers is presented that entails a highly oriented skin with a core consisting of microfibrils. The orientation of the crystalline blocks within the microfibrils is similar to what has been reported for nylon fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2828–2838, 2002     

Effects of molecular architecture on two‐step,melt‐spun poly(lactic acid) fibers

Fibers of poly(lactic acid) (PLA) produced by two‐step melt spinning have been studied. The PLA resins used contain a 96:04 ratio of L:D stereochemical centers; however, one of the materials is branched by a peroxide treatment. The thermal, mechanical, and morphological properties of the fibers are compared for the two different molecular architectures. In the branched material, at least some of the branches exceed the entanglement molecular weight. The branched material is accordingly characterized by greater shear and extensional viscosity than the linear material. Fiber properties are highly influenced by the draw ratio; both branched and linear materials reach a plateau of about 35% crystallinity. The branched polymer reaches the plateau at a lower draw ratio, and this is indicative of faster crystallization kinetics. Both materials shrink in boiling water, and the amount of shrinkage decreases with increasing draw ratio. At an intermediate draw ratio of 6, the branched material is characterized by significantly larger shrinkage. With small‐angle X‐ray scattering and atomic force microscopy, the morphology is found to be fibrillar. Microfibril diameters range from approximately 20 to 30 nm and are almost identical for the two molecular architectures studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2839–2846, 2002     

Investigation of gravity‐spun,melt‐spun,and melt‐blown polypropylene fibers using atomic force microscopy

The morphology exhibited in a polymer depends on the particular process and processing conditions used to shape and modify the polymer. This morphology has an important influence on the final polymer product (sheet, molded part, etc.). Ten years ago, atomic force microscopy (AFM) was applied for the first time on polymer materials. Since then, AFM has been used extensively on polypropylene (PP) surfaces, but still very little has been reported on the use of AFM for analyzing PP fibers. The purpose of our work was to show the modifications of (a) the morphology and (b) the microstiffness of PP fiber surfaces processed under different operating conditions. Three fiber production processes were used: gravity spinning, melt spinning, and melt blowing. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1921–1937, 2000     

Melt spinning of metallocene catalyzed polypropylenes. II. As‐spun filament structure and properties

The melt spinning of metallocene catalyzed isotactic polypropylene (miPP) resins was investigated. The as‐spun filament properties from six miPP resins were studied with melt flow rates (MFR) between 10 and 100, and a Ziegler–Natta catalyzed isotactic polypropylene (zniPP) resin with a MFR of 35 was studied for a comparison. Generally, as the molecular weight increased the filament density increased, the birefringence decreased, the tensile strength decreased, and the elongation to break increased. As the spinning speed increased, the density, birefringence, tensile strength, and crystalline and noncrystalline orientation functions generally increased. However, the low MFR miPP and the zniPP resin had decreases in the birefringence and tensile strength with an increase of the spinning speed. The miPP resins were found to have breaking tensile strengths up to 50% higher than the zniPP resin at similar spinning speeds. The observed fiber properties were explained based on the nature and orientation of noncrystalline portions of the fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3237–3247, 2001     

Modeling of degradation of unstabilized and HALS‐stabilized LDPE films under thermo‐oxidation and natural weathering conditions

Mathematical models are proposed to predict degradation of unstabilized low density polyethylene (LDPE) films and those stabilized with hindered amine light stabilizers (HALS) under both thermo‐oxidation at 90°C and natural weathering conditions. The degradation was measured by change in percent elongation at break (?_r) with time. The mathematical approach developed was multiple linear regression analysis (MLRA). The reliability of the selected models was analysed using four statistical criteria, residual variance, coefficient of determination (r²), Student test and Fisher‐Snedecor test. The linear systems that resulted from the MLRA were resolved by the Cholesky method. The results obtained indicated that the polynomial models developed to predict elongation at break were reliable for both unstabilized and HALS‐stabilized samples under thermo‐oxidation at 90°C and natural weathering conditions. This was also confirmed by the comparison of the half‐life time (HLT) values predicted from the models with those observed experimentally. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3284–3292, 2001     

纺丝条件对干纺氨纶性能的影响

通过改变干纺时的纺丝条件并对所得产品的断裂强力、断裂伸长率及均一性进行测试,发现氨纶的断裂强力随着热风的温度升高、风量增大及纺丝速度的提高而增大,断裂伸长率随着风温升高而增大,但随着风量及纺速的增大而减小,双导丝器的使用对于改善氨纶的均一性有利。     

A morphological study of melt‐spun polypropylene filaments by atomic force microscopy

Surface morphology of melt‐spun polypropylene (PP) filaments, spun from an additive‐free PP powder and from a commercial‐grade PP with different draw ratios, were examined with atomic force microscopy (AFM). The surface morphology of as‐spun filaments was spherulitic. The gradual transformation of the surface structure from a spherulitic morphology to a fibrillar morphology during stretching was studied. In the filaments spun from the commercial‐grade PP, the transformation was initiated by deformation of spherulites with a draw ratio of 1.2 and continued with association of lamellar stacks into fibrillar chains with a draw ratio between 1.2 and 2.0. A hierarchical morphological microstructure of fibrils, microfibrils, and nanofibrils was developed with a draw ratio of 4.0. In the filaments spun from the additive‐free PP, the association of lamellar stacks into fibrillar morphology occurred considerably later, between draw ratios of 2.0 and 4.0. An oriented lamellar structure was found in these filaments, still with a draw ratio of 4.0. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1242–1249, 1999