Bleaching polyvinyl alcohol

When making very dehcate materials it may be necessary to use a yam which is so fine that it would break down under the stresses imposed on it during manufacture. The strength, however, is sufficient once the fabric is made because of the mutual support of adjacent threads. In such cases it is customary to impart temporary strength to the yam by a process known as sizing. This consists of impregnating the thread with some easily removed substance such as starch or dextrine and, in the case of the more modern man-made fibres, with a synthetic product such as polyvinyl alcohol or polyacrylic acid. The size is usually removed before the article is dyed or bleached. Yarns are frequently referred to as warp or weft yarns. In a... 

To one such slide, a tissue dampened with 0.1 N HCl, 2% starch and 10% potassium iodide solution (made fresh daily) is applied. A weak color reaction, which is much stronger at the locations of charcoal flecks and any white droplets are potassium oxides and carbonate. A tissue overlay of hexamethylene rosaniline hydrochloride (crystal violet) is applied to another fresh slide. Bleaching and pH effects are observed. Other pH indicators and other peroxide sensitive solutions should be applied. The author finds that thickening the reagents with carbohydrate and polyvinyl alcohol to slow diffusion rates is advisable in some cases. 

Bleached cotton linters with a degree of polymerization (DP) of 1,300 were used as the starting cellulose sample. The cellulose was first dried imder vacumn at 40°C. A, A -dimethylacetamide (DMAc) purchased from Katayama Chemicals Co. Ltd. (99+%) was dehydrated with molecular sieve 3A and used without further purification. Lithium chloride (LiCl) powder (Katayama Chemicals Co. Ltd.) was oven-dried at least for 3 days at 105°C. Methylcellulose with a degree of substitution (DS) of 1.6 and polyvinyl alcohol (PVA) with a DP of 2,000 were purchased from Shin-Etsu Chemical Co. Ltd. and Katayama Chemicals Co. Ltd., respectively. Cellulose acetate with a DS of 2.45 (L-70) and purified chitin were provided by Daicel Chemicals Co. Ltd. and Katakura Chikkarin, respectively. 

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