Fibers solubility testing

B) Natural fiber solubility tests Here the same general procedure and test tube set-up will be used except that we will be testing the solubility of three natural fibers - cotton, wool and silk in two solvents ... 

The progress of the partial saponification can be checked by a simple solubility test. About 1 ml of the solution is withdrawn and the cellulose acetate precipitated with water. The small sample is quickly washed free of acid and dried as much as possible by pressing between two filter papers. Some fibers of the still damp material are placed in a test tube with 15-20 ml oholuene/ethanol (volume ratio 1 1) and heated to boiling in a water bath. If the fibers go into solution, then after about 15 min the whole charge can be worked up as described above. 

For mineralization, the normal, metastable state is adjusted by nucleation, measured by the seed and solubility tests. The seed test measures amount of solid apatite required to precipitate Ca2+ and HP042- ion concentrations exceeding their solubility product. The solubility test measures the minimal concentrations of Ca2+ and HP042- necessary to induce precipitation. Type I collagen fibers nucleate bone formation as the concentrations of Ca2+... 

Quantitative determination of the percentage of fiber in a yarn/fabric blend (solubility test)... 

Perform the applicable solubility tests. Use acetone first. Time, temperature, and reagent concentration are important, as well as the size of the fiber bunch, yam, or fabric piece. Use the smallest sample possible in order to speed up the test results. 

A robbery occurred in which the thief or thieves entered through a skylight. One of the thieves caught his shirt on a wood splinter and several fibers were tom loose. The police have a suspect, but they have no evidence except the fibers. Other scientists are comparing the fibers by microscopy, infrared, x-ray diffraction, dying, and burning tests. Your part is to do solubility tests to see if fibers from the suspect match those at the crime scene. 

Fibers of the control and selected chemically modified cottons were examined techniques of optical microscopy described previously.Ultra thin cross sections of the fibers were subjected to layer expansion by polymerization of methyl methacrylate and to solubility tests in 0.5 M cupriethylenediamine (cuene) and were examined by the techniques of transmission electron microscopy as previously reported.Scanning electron micrographs of fibers of selected samples before and after subjection to various solvents were also obtained. 

Solubility Tests Fibers of cellulose esters (e.g., cellulose acetate, cellulose nitrate) dissolve in acetone or chloroform, polyamide fibers dissolve in cone, formic acid, and polyacrylonitrile fibers dissolve in cold, cone, nitric acid and in boiling dimethylformamide. Polyester fibers are soluble in 1,2-dichlorobenzene or nitrobenzene, while wool dissolves in potassium hydroxide. Polyamide fibers can be differentiated by their different solubilities in 4.2 N hydrochloric acid polyamide 66 (nylon 66) is soluble upon heating, and polyamide 6 (nylon 6) dissolves at room temperature (4.2 N HCl is prepared as follows one carefully pours 35 ml of fuming (12.5 N) HCl into 65 ml of water). 

Fiber identification There are several methods that the fiber industry uses to identify fibers and distinguish them from one another. Some of the most coimnon methods include microscopic examination, solubility test, heating and flammability test, density, and staining techniques [10]. 

Chemical test. Solubility is a very effective test to identify fibers. Polyolefins have excellent chemical resistance to most common solvents, and they can be easily distinguished from a polyester or nylon fiber by a simple solubility test. Functional groups can also be identified using a technique such as FTIR which wiU help identify the fiber type. 

Bonding Permanency ofWater- or Solvent-Soluble Liquid Adhesives for Automatic Machine Sealing Top Flaps of Fiber Specimens, Test for (D 1713)... 

If an exhibit of evidence is consumed in testing, the tests performed on it can never be repeated or verified. While this is not a limitation when the case consists of several milliliters of blood or a large bindle of white powder, other cases are not so simple. If the exhibit is a single fiber or one tiny paint chip, analytical options are limited. Solubility tests would be a poor choice for a single paint chip, but microspectrophotometry (nondestructive) would be ideal. 

Solubility tests were performed on each of the fibers. The basic fiber solubility analysis scheme was that used by the Federal Bureau of Investigation (1978). 

Aqueous systems have been studied by a very large number of investigators. Economy, safety, convenience and quality of product have combined to make this the method of choice for commercial production of copolymers. The industrial importance of such end products as elastomers and acrylic fibers has been a special incentive to related fundamental studies. Furthermore, the relatively high solubility of acrylonitrile monomer in water coupled with insolubility of the polymer make it a convenient test monomer for studies of initiation by redox systems (6, 25, 102). Large numbers of homogeneous chemical initiators and some heterogeneous initiators have been studied as well as initiation by photochemical means, by ultrasonics and by ionizing radiation. It will not be possible here to review the enormous world literature. Several publications (/, 92, 117) refer in some detail to the older papers, and we shall restrict our comments to recent interpretations that have received support from several quarters. 

Metabolism of pectin. Pectin has only recently come, to be considered a part of the dietary fiber complex. Previously it was excluded because 1) it is not fibrous (except at the molecular level), 2) it escapes detection in standard fiber tests owing to its solubility, and 3) it usually does not survive intestinal passage. In a reassessment of which dietary components should be considered fiber, Trowell (49) proposed that dietary fiber include those constituents of food resistant to hydrolysis by man s alimentary enzymes. Spiller (50, 51) suggested that confusion surrounding the term "fiber" be avoided by using the term "plantix" to denote those plant materials of polymeric nature not attacked by human digestive enzymes. 

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