Fiber processing technologies

Some of the plants readily release numerous fine, strong, and long fibers that could be spun into fine yams comparable to those observed in the prehistoric fabrics (21, 22). While coarser splits of wood could have been used in making baskets or cordage, the first focus of the CPFC was the fibers used in textiles that would show advanced fiber processing technology. 

In the presentation of the elevated temperature mechanical behavior of ceramic matrix composites, some degree of separation has also been made between fiber-reinforced and whisker- or particulate-reinforced composites. This has been necessary because of the way the field has evolved. The continuous fiber-reinforced composites area in many ways has evolved as a field in its own right, driven by developments in fiber processing technology. 

This functionalization of the fibrous implantable device, which allows to meet specific needs in particular biological environments, needs to correlate the microstmcture and nanostructure scales of fibers to the scale of the desired cells that we desire for the adhesion. As cell adhesion occurs on the fiber length, fibers diameter should be optimized to ensure high adsorption surface ratio while being adjusted to cell dimensions that can vary from nanometers to hundreds of micrometers. Fiber process technologies are nowadays able to cover this range and provide implantable fibers with diameters from millimeters, such as suture filaments, to nanometers, by electrospinning process (Fig. 13.2). 

Staple is produced by cutting a crimped tow into short lengths (usually 4—5 cm) resembling short, natural fibers. Acetate and triacetate staple are shipped in 180—366 kg bales, but production is quite limited. Conventional staple-processing technology appHed to natural fibers is used to process acetate and triacetate staple into spun yam. 

The second ceUulosic fiber process to be commercialized was invented by L. H. Despeissis (4) in 1890 and involved the direct dissolution of cotton fiber in ammoniacal copper oxide Uquor. This solvent had been developed by M. E. Schweizer in 1857 (5). The cuprammonium solution of ceUulose was spun into water, with dilute sulfuric acid being used to neutralize the ammonia and precipitate the ceUulose fibers. H. Pauly and co-workers (6) improved on the Despeissis patent, and a German company, Vereinigte Glanstoff Eabriken, was formed to exploit the technology. In 1901, Dr. Thiele at J. P. Bemberg developed an improved stretch-spinning system, the descendants of which survive today. 

Textile technology is used to mechanically or aerodynamicaHy arrange textile fibers into preferentially oriented webs. Fabrics produced by these systems are referred to as dry-laid nonwovens. Dry-laid nonwovens are manufactured with machinery associated with staple fiber processing, such as cards and gametts, which are designed to manipulate preformed fibers in the dry state. Also included in this category are nonwovens made from filaments in the form of tow, and fabrics composed of staple fibers and stitching filaments or yams, ie, stitchbonded nonwovens. 

The development of fiber optics technology, user-friendly displays, and enhanced data presentation capabihties have made on-line analysis acceptable within the plant manufactuting environment. However, it is apparent that a barrier stiU exists to some extent within many organizations between the process control engineers, the plant operations department, and the analytical function, and proper sampling is stiU the key to successful process analytical chemistry. The ultimate goal is not to handle the sample at ah. 

Hollow-fiber permeators, 26 22 Hollow fibers, 13 389-390 cellulose ester, 26 19 cellulosic, 26 18-20 ion-exchange, 26 15 mechanical considerations and dimensions for, 26 5-7 natural polymer, 26 23 polyacrylonitrile, 26 23 polyamide, 26 21-22 post-treatment of, 26 13-14 preparation of, 26 3 production of, 19 757 with sorbent walls, 26 26 technology of, 26 27 wet spinning of, 25 816, 817-818 Hollow-fiber spinning processes, 26 7-12 Hollow fiber spinning technology,... 

For industrial products, such as films and fibers (woven and un-woven), the concept development stage is shown in Fig. 10.3-2. Under materials development, searches are carried out for chemicals and chemical mixtures having the desired properties and performance, and reaction paths for chemical synthesis. Under product/process technology development, often new methods are needed for example, methods for creating multilayer films. And, finally, under manufacturing process development, an example of something new would be multilayer dies for producing multilayer polymer films. 

The islands-in-the-sea approach uses bico technology to extrude filaments that contain a multiplicity of small fibrils encased in a soluble matrix. After fiber processing and fabric formation, the matrix is dissolved away to leave behind the microfibers. Fibers with sub-micron diameters can be produced. The process is expensive, but luxurious fabrics and nonwoven materials such as Ultrasuede are made in this way. 

In contrast to fiber-forming technologies, the film process requires a comparatively reduced IV due to processing reasons, for example, the pressure along the die and therefore the evenness of thickness as well as the generation of structure, particularly with respect to crystallinity, will need to be considered. As usual, a compromise between intrinsic physical properties and processing has to be found. 

FIBERS. The field of fibers is an evolving one. with new technologies being developed constantly. With ihe increasing use of fibers in non-traditional textile applications, such as geoiexliles (qv). fiber-reinforced composites, specialty absorption media, and as materials of construction, new fiber types and new processing technologies can be anticipated. 

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