Hard elastic fiber

Nylon-11. Nylon-11 [25035-04-5] made by the polycondensation of 11-aminoundecanoic acid [2432-99-7] was first prepared by Carothers in 1935 but was first produced commercially in 1955 in France under the trade name Kilsan (167) Kilsan is a registered trademark of Elf Atochem Company. The polymer is prepared in a continuous process using phosphoric or hypophosphoric acid as a catalyst under inert atmosphere at ambient pressure. The total extractable content is low (0.5%) compared to nylon-6 (168). The polymer is hydrophobic, with a low melt point (T = 190° C), and has excellent electrical insulating properties. The effect of formic acid on the swelling behavior of nylon-11 has been studied (169), and such a treatment is claimed to produce a hard elastic fiber (170). 

Hard-Elastic Fibers. Hard-clastic fibers arc prepared by annealing a moderately oriented spun yam at tiigli temperature under tension. They are prepared from a variety of olefin polymers, acetal copolymers, and polypivalolactone. 

Accordion" morphology or "hard-elastic" fibers (formed... 

Figure 38-10. Idealized representation of a hard-elastic fiber the lamellae packets are deformed, but cannot separate from each other because of the many tie molecules, and snap back into their original positions when the stress is removed.

But other polymers such as it-poly(propylene) or poly(oxymethylene) can also be converted to what are known as hard-elastic fibers by suitable physical post-treatments (see also Section 38.3.1). At the present time, these energy elastic fibers are in the evaluation stage. 

S. L. Cannon, G. B. McKenna, and W. O. Statton, Hard-elastic fibers (a review of a novel state... 

Sprague, B.S., Relationship of structure and morphology to properties of "hard" elastic fibers and films. Macromol. Sci.-Phys., 1973f 8(l) 157. 

Miles, M., Petermann, J. and Gleiter, H., Structure and deformation of polyethylene hard elastic fibers. J. Macromol. Sci.-Phys., 1976, B12(4), 523. 

Essentially a hinge is composed of three layers caused by a high velocity of the pol)mner melt two highly oriented layers and one isotropic core layer. The mechanical behavior of the oriented layers is similar to that of hard elastic fibers which show a high stiffness and a high strain recovery. The higher the molecular orientation and the layer thickness, the better the hinge properties are. The layer thickness can be increased by low temperatures (melt and/or mold). 

Interlamellar separation is induced by a component of tension or compression perpendicular to the lamellar surface. This type of deformation is difficult since a change in the lamellae separation should be accompanied by a transvei-se contraction and the deformation must involve a change in volmne. Hard elastic fibers are found to deform in such a way. When the lamellae are arranged in the form of stacks embedded in the amorphous matrix, then the stacks are free to rotate under the stress. Any other deformation of the amorphous phase... 

More recentiy, melt-spun biconstituent sheath—core elastic fibers have been commercialized. They normally consist of a hard fiber sheath (polyamide or polyester) along with a segmented polyurethane core polymer (11,12). Kanebo Ltd. in Japan currentiy produces a biconstituent fiber for hosiery end uses called Sideria. 

Hard and soft acid and base (HSAB) principle, 16 780 Hard blacks, 21 775 Hard-burned quicklime, 15 28 Hard coals, 6 703 classification, 6 712 Hard copper alloys, 7 723t relief annealed, 7 723t Hard copy systems, 9 513-514 Hard core repulsion, 23 93 Hard-elastic olefin fibers, 11 242 Hardenability, of steel, 23 283—284 Hardened MF resins, analysis of,... 

Olefin fiber production, economic aspects of, 11 242-243 Olefin fibers, 11 224-246 applications of, 11 243-244 creep, stress relaxation, and elastic recovery in, 11 227-228 extrusion of, 11 231-234 hard-elastic, 11 242 high-strength, 11 241-242 manufacture and processing of,... 

Spandex Elastic fiber consisting of a block copolymer of a PU, hard segment, and a polyester or polyether, soft segment. 

Elastane. The DuPont Company commercialized the first manufactured elastic fiber, Lycra, in 1958. Originally categorized as a span-dex fiber, the name elastane has become more common around the world. This specialty fiber is described as a segmented polyurethane that contains hard and soft segments their ratio determines the amount of stretch built into the fiber. Elastane fibers are formed by dry-spinning or solvent-spinning. The continuous filaments can be coalesced multifilaments or monofilaments, depending on the manufacturer. 

C H Du, B K Zhu, Y Y Xu, Effects of stretching on crystalline phase structure and morphology of hard Elastic PVDF fibers , J of Appl Polymer Sd, 2007104 2254-2259. 

Originally hard-elastic PP was made from crystalline lamellar materials and was processed via melt spinning and crystallization under stress, followed by annealing under tension. The structure of the material consists of stacked crystalline lamellae (5-40 nm thick) with fold planes normal to the fiber direction. Between the lamellae, microfibrils oriented parallel to the draw direction are located. Under load, the lamellae tend to separate and voids bridged by fibrils appear. The void volume is initially about 18% at zero strain which increases to about 65% at 15% strain. No further increase in void volume was observed above 15% deformation. 

Relaxation and cyclic deformation behavior of the hard-elastic polypropylene is of particular interest [2]. If the fiber is allowed to relax, the stress needed to continue the deformation is different from the initial stress. The stress increment can be divided into a permanent and transient part. As the recovery properties of the fibers begin to deteriorate, the permanent increment changes from a negative to a positive value and the transient component decreases to zero. Stress relaxation of... 

Some attempts have been done to use the hard-elastic PP as a component in a blend [3]. Films with improved mechanical properties have been obtained by blending a small portion of extrusion-grade PP with fiber-grade PP. The addition of a small amount of high density polyethylene (HOPE) results in a substantial increase of the hard elasticity of the filaments. 

When a PP is extruded and taken-up at a high draw ratio and crystallized under a high stress and annealed, a lamella-stacked structure is formed. In this structure, the lamellae are oriented perpendicular to the extrusion direction and connected by the tie molecules. When such an extrudate is stretched in the extrusion direction, the lamellae open elastically with the tie molecules working as fixing points. Therefore, after stress removal, the initial shape and structure are restored. Since such a part shows a high elastic recovery after a deformation and the elastic modulus is nearly the same as that of the usually processed article, it is called a Tiard-elastic item. When the hard-elastic film or fiber is drawn beyond the yielding point, plastic deformation occurs, leading to void formation, and a microporous film or fiber can be obtained. 

Fig, 54a-g. Wide-angle (a-c) and small-angle (d- ) X-ray diagrams of hard-elastic, annealed polypropylene a-c polypropylene film annealed for 0.75 h at 140 °C, a undrawn, b 73% extension, c recovered after extension to 73% strain d-g polypropylene fiber annealed for 1 h at 150 °C, d undrawn, e 50 % extension, f 100% extension, g recovered after extension to 100 % strain [reproduced from Noether, H. D., W. Whitney, Kolloid-Z. und Z. Polymere, 251.991-1005 (1973) by permission of the publishers. Dr. Dietrich Steinkopff Verlag, Darmstadt, West Germany)... 

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