As-spun Fibers (as-spun + fiber)

Distribution by Scientific Domains

Selected Abstracts

Investigating the jet stretch in the wet spinning of PAN fiber

Xiaomei Zeng
Abstract The jet stretch of wet-spun PAN fiber and its effects on the cross-section shape and properties of fibers were investigated for the PAN-DMSO-H2O system. Evidently, the spinning parameters, such as dope temperature, bath concentration, and bath temperature, influenced the jet stretch. Also, under uniform conditions, the postdrawing ratio changed as well as that of jet stretch. When coagulation temperature was 35C simultaneously with bath concentration of 70%, jet stretch impacted obviously the cross-section shapes of PAN fiber, but had little effect when the temperature was below 10C or above 70C. As the jet stretch ratio increased, the crystallinity, crystal size, sonic orientation, and mechanical properties of the as-spun fiber changed rapidly to a major value for jet stretch ratio of 0.9 where the cross section of as-spun fiber was circular. With further increasing of jet stretch ratio, the properties changed slightly but the fiber shape was not circular. The results indicated that appropriate jet stretch, under milder formation conditions in wet-spinning, could result in the higher postdrawing ratio and circular profile of PAN fiber, which were helpful to produce round PAN precursor with minor titer and perfect properties for carbon fiber. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

Gel-spun polyacrylonitrile fiber from pregelled spinning solution

Lianjiang Tan
Polyacrylonitrile (PAN) fibers have been gel spun from pregelled PAN spinning solution. The pregelled solution had network structure with elevated spinnability, the as-spun fiber from which had more circular cross-section and reduced skin-core difference. Drawing was more effective in inducing the segmental orientation and crystallization in gel-spun fiber than in dry,wet spun fiber. The mechanical properties of the gel-spun fiber were better than those of the dry,wet spun fiber after multi-stage drawing. POLYM. ENG. SCI., 2010. 2010 Society of Plastics Engineers [source]

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

Jasmeet Kaursoin
Abstract 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 100C 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 [source]

Solid-state polymerization of melt-spun poly(ethylene terephthalate) fibers and their tensile properties

Sachiko Nitta
Abstract The production of high modulus and high strength poly(ethylene terephthalate) fibers was examined by using commercially available melt-spun fibers with normal molecular weight (intrinsic viscosity = 0.6 dL/g). First, molecular weight of as-spun fibers was increased up to 2.20 dL/g by a solid-state polymerization, keeping the original shape of as-spun fibers. Second, the polymerized as-spun fibers were drawn by a conventional tensile drawing. The achieved tensile modulus and strength of as-drawn fibers (without heat setting) were 20.0 and 1.1 GPa, respectively. A heat setting was carried out for the as-drawn fibers. Tensile properties of the treated fibers were greatly affected by the condition of the heat setting. This was related to the increase of sample crystallinity and molecular degradation during the treatments. 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1791,1797, 2007 [source]

Exploration of ionic modification in dual-layer hollow fiber membranes for long-term high-performance protein separation

AICHE JOURNAL, Issue 2 2009
Yi Li
Abstract Two types of ionic modification approaches (i.e., sulfonation and triethylamination) were applied with the aid of dual-layer hollow fiber technology in this work to fine tune the pore size and pore size distribution, introduce the electrostatic interaction, and reduce membrane fouling for long-term high-performance protein separation. A binary protein mixture comprising bovine serum albumin (BSA) and hemoglobin (Hb) was separated in this work. The sulfonated fiber exhibits an improved BSA/Hb separation factor at pH = 6.8 compared with as-spun fibers but at the expense of BSA sieving coefficient. On the other hand, the triethylaminated fiber reveals the best and most durable separation performance at pH = 4.8. Its BSA/Hb separation factor is maintained above 80 for 4 days and maximum BSA sieving coefficient reaches 33%. Therefore, this study documents that an intelligent combination of both size-exclusion and electrostatic interaction can synergistically enhance protein separation performance in both purity and concentration. 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

Novel aromatic polyimide fiber with biphenyl side-groups: Dope synthesis and filament internal morphology control

Xiangyang Liu
A new organic-soluble aromatic polyimide with biphenyl side-groups has been synthesized from 4,4,-oxydiphthalic anhydride and 3,5-diamino-benzonic-4,-biphenyl ester (DABBE) via a one-step polymerization in m -cresol. A higher molecular weight polyimide has been obtained by the addition of chlorotrimethylsilane (TMSCl) in the solution of DABBE to form, in situ, silylated diamine. The optimum mole amount of TMSCl relative to the number of amino groups is 100%. This polyimide is soluble in m -cresol, allowing fibers to be spun from isotropic solution using a dry-jet wet spinning method. Based on a ternary phase diagram of m -cresol, ethanol, and water, controlling of the internal morphology of as-spun fibers has been achieved by varying the rate of polyimide coagulation through adjustment of nonsolvent/solvent miscibility in the coagulation bath. Scanning electron microscopic pictures show that filament internal morphologies ranged from porous-like to fully solid. The solid as-spun fibers can be drawn at high temperatures (>330C) under tension to high drawn ratios (up to 6), which produces a remarkable increase in tensile strength to about 1.0 GPa and an initial modulus higher than 60 GPa. POLYM. ENG. SCI. 46:123,128, 2006. 2005 Society of Plastics Engineers [source]

Preparation and characterization of ultrafine electrospun polyacrylonitrile fibers and their subsequent pyrolysis to carbon fibers

Juthawan Sutasinpromprae
Abstract The present contribution reports the fabrication and characterization of ultrafine polyacrylonitrile (PAN) fibers by electrospinning and further development of the as-spun PAN fibers into ultrafine carbon fibers. The effects of solution conditions (i.e., solution concentration, viscosity, conductivity, and surface tension) and process parameters (i.e., applied electrostatic field strength, emitting electrode polarity, nozzle diameter, and take-up speed of a rotating-drum collector) on morphological appearance and average diameter of the as-spun PAN fibers were investigated by optical scanning (OS) and scanning electron microscopy (SEM). The concentration, and hence the viscosity, of the spinning solutions significantly affected the morphology and diameters of the as-spun PAN fibers. The applied electrostatic field strength and nozzle diameter slightly affected the diameters of the as-spun fibers, while the emitting electrode polarity did not show any influence over the morphology and size of the as-spun fibers. Utilization of the rotating-drum collector enhanced the alignment of the as-spun fibers. Within the investigated concentration range, the average diameter of the fibers ranged between 80 and 725 nm. Finally, heat treatment of the as-spun fibers with their average diameter of about 450 nm was carried out at 230 and 1000 C, respectively. Various characterization techniques revealed successful conversion into carbon fibers with an average diameter of about 250 nm. Copyright 2006 Society of Chemical Industry [source]