Quality fibers

Nontoxic and noncorrosive solvent systems can be used when chitosan is considered instead of chitin for the manufacture of fibers. Improvements of the fiber quality rely mostly on technical shrewdness for instance the use of potassium hydrogen phthalate at pH 4-5 imparted better mechanical properties [255]. 

Table 21.3 presents an overview of wood pulping types by the method of fiber separation, resultant fiber quality, and percent of 1998 U.S. pulp production.1112 Many mills perform multiple pulping processes at the same site, most frequently nondeink secondary fiber pulping and paper-grade kraft... 

Process Category Fiber Separation Method Fiber Quality Examples % of Total 1998 U.S. Wood Pulp Production... 

A major aspect of polymer, in particular polyester, production is the manufacturing of fibers for textile and technical applications. This section deals with the impact of the production conditions on the fiber quality. The following discussion will be mainly based on PET fibers, but by and large the problems, phenomena and their solutions are generally relevant to the production of other polymer filaments. 

Cannabinoids are the psychoactive components of marijuana, which has the species name Cannabis sativa. Concentrations of cannabinoids vary greatly from plant to plant. The original strains of this plant species contain very little of these psychoactive components and have been used for many centuries for their great fiber qualities. Strains of Cannabis that may be smoked for psychoactive effects on average contain about 4 percent cannabinoid derivatives. The most active of these derivatives is the compound A9-tetrahydrocannabinol (THC), shown in Figure 14.33 on page 504. 

Chemical harvest aids are presently used on more than 75% of the cotton acreage in the U.S.. The amount of foliage may be reduced either by the use of defoliants or the use of desiccants. Defoliants induce leaf fall and must be applied one to two weeks before harvest so that the abscission process may be complete. Desiccants cause the foliage to lose water and sometimes the leaves and stems are killed so rapidly by desiccants that an abscission layer has insufficient time to develop and the drying leaves remain attached to the plant. Desiccants usually require one to three days to act before harvest can be started. The obvious advantage of desiccants over defoliants is that they may be applied at a later date, thus gaining additional time during which the leaves continue to function and to contribute to see the fiber quality. Hundreds of chemicals have been evaluated as defoliants and desiccants. Only a few are in commercial use. 

Childers, R. E., and Baker, R. V., Effect of Moisture Conditioning on Ginning Performance and Fiber Quality of High Plains Cotton, Trans. ASAE (1978), 1 (2), 379-384. 

Leonard, C. G., Ross, J. E., and Mullikin, R. A., Moisture Conditioning of Seed Cotton in Ginning as Related to Fiber Quality and Spinning Performance, USDA Market Res. Rpt. 

These chemical tests on papermaking pulps can serve as general indicators of fiber quality. It has been well established that permanence of papers is enhanced if the solubility in alkaline solutions and the content of functional groups are low and the molecular weight or degree of polymerization (DP) is high. The relationships, however, cannot be stated except in general terms it is not possible at the present time to establish specifications for these properties which will ensure permanence... 

Paszner, L. and Cho, H. J., Organosolv pulping - Acidic catalysis options and their effect on fiber quality and delignification. Tappi J 1989, 72 (2), 135-142. 

At the gin, baled cotton is sampled so that grade and other quality parameters can be determined and the cotton is classed at the U.S. Department of Agriculture (USDA) classing offices. Classification is a way of measuring the fiber quality and physical attributes of this natural product that affect the manufacturing efficiency and quality of the finished product (see Chapter 8). Cotton bales are usually stored in warehouses prior to going to the textile mill [42]. 

There are two methods for estimating fiber quality, expert appraisal by a trained classer, and instrumentation. Many different classification systems are used worldwide in the various countries where cotton is grown. For example, the United States [601], China [3,594,602], Uzbekistan [603], and Egypt [594] all have different systems. All systems measure cotton quality using similar parameters, even though the actual classification scheme and classification designations may be different. The determinations, either manually or by instrument, may be different for individual parameters also. The quality parameters are the following ... 

The U.S. HVI system for the classification of fiber quality and instrumentation for measuring other fiber properties are becoming more widely used all over the industrialized world, as well as in some developing countries for determining the proper laydown and mix for processing cotton in textile mills. Therefore, the U.S. system will be described in more detail than the other classing systems. Information also is given on how the various quality parameters can affect cotton fiber chemistry. 

In 1993, a new classification system for cotton fiber quality, RST Uz 604-93, was introduced in Uzbekistan [603]. Since 1995, this standard has also been used in Kazakhstan and Tadjikistan [603]. In Azerbaijan, attempts are made to classify its cotton in accordance with international standards [605]. 

Color Total impurities Degradation of fiber quality 200-300 APHA 2.0%-4.0% 25 APHA 0.8%... 

Depending on the conditions under which it grows, cannabis will either produce more resin or more fiber. When raised in hot, dry climates, resin is produced in great quantities and fiber quality is poor. In countries with mild, humid weather, less resin is produced and the fiber is stronger and more durable. 

Fibers can be cubed or extruded. Cotton motes, flax fiber, dry refined wood or straw fibers can be cubed to 16 Lb to 18 Lb/CP (256-288 Kg/m3). With good moisture distribution and properly designed infeed systems, hydrogen bonding and edge glazing can be employed to cube fibers without losing fiber quality. 

Another limitation that is specific to the parallel plate electrospinning technique is the collection of extremely thin nanofibers, which have been observed to break because they were unable to sustain the forces of their own weight and of the repulsive charges from other fibers [62]. An electrically resistive substrate inserted into the gap between the plates can provide support to fibers suspended between the plates without influencing fiber quality [62], and may also help to shield any conductive materials below the air gap, which may attract unwanted non-aligned nanofibers. Substrates with bulk resistivity greater than 10 Q cm, such as quartz and polystyrene, are suitable for placement between parallel electrodes, while materials with bulk resistivity of less than 10 Q cm, such as glass, may result in random fiber orientations [67, 68]. 

In tins connection it diould be borne in mind that structural modification of the fibor is a double-edged weapon since the improvements ate often achieved at the expense of existing fiber properties. The newly modifkd textile material may definitely show some valuable new properties for the required performance, but at the same time some of its excellent ori nal features may have become inq>aired so as to exclude the modified fiber from some of the tn itkmalmd uses of the KT material. Modification of the macromolecule should this be achieved with m oa-tion in order to ensure real success in in roving fiber quality at lea in a ven textfle area. This fact, explains why the modifications have resulted in different effects for different ends and why the improvements concern only one or a few properties of the fiber. For this reason, the big producer conq nies put on the market a great number of modified PET fibers, each of vhich is onfy capable of satisfying the requirements for specific performances. 

Two variables — leaving aside fiber quality and construction of the textile — are essential for evaluation of the redeposition behavior of dirt ... 

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