Document EmB8qqZrL76EoLEVJ9mBzN4rg

828 CHAPTER 45 1946 Guide penalties for excesses. Deficiencies result in loss of revenue to seller and loss of desirable quality to buyer. Manufacturing economy therefore requires that the moisture content be maintained at a percentage favorable to rapid and satisfactory manipu lation and to a minimum loss of material through breakage. A uniform condition is desirable in order that high speed machinery may be adjusted permanently for the desired production with a minimum loss from delays, wastage of raw material and defective product. In the processing of hygroscopic materials, it is usually necessary to secure a final moisture content suitable for the goods as shipped. Where the goods are sold by weight, it is proper that they contain a normal or standard moisture content. Moisture Content and Regain The terms moisture content and regain refer to the amount of moisture in hygroscopic materials. Moisture content is the more general term and refers either to free moisture (as in a sponge) or to hygroscopic moisture (which varies with atmospheric conditions). It is usually expressed as a percentage of the total weight of material. Regain is more specific and refers only to hygroscopic moisture. It is expressed as a percentage of the bone-dry weight of material. For example, if a sample of cloth weighing 100.0 grains is dried to a bone-dry weight of 93.0 grains, the loss in weight, or 7.0 grains,, represents the weight of moisture originally contained. This expressed ;as a percentage of the total weight (100.0 grains) gives the moisture content or 7 per cent. The regain, which is expressed as a per- ............... . 7.0 centage of the bone-dry weight, is or 7.5 per cent. The use of the term regain does not imply that the material as a whole has been completely dried out and has re-absorbed.moisture. During the processing of certain textiles, for instance-, complete drying during manu facturing is avoided as it might appreciably reduce the ability of the material to re-absorb moisture. A basis for calculating the regain of textiles is obtained by drying, under standard conditions, a sample from the lot and the dry weight thus obtained is used as- a basis in the calcu lations to determine the regain. The moisture content of a hygroscopic material at any time depends upon the nature of the material and upon the temperature and especially the relative humidity of the air to which it has been exposed. 'Not only do different materials acquire various percentages-of moisture-after prolonged; exposure to a given atmosphere, but the rate' of absorption or drying varies with the nature of the material, its thickness and density. Table 2 shows the regain or hygroscopic moisture content of several organic arid inorganic materials when in equilibrium at a dry-bulb tem perature, of 75 F and various relative humidities. The effect of relative humidity on regain of hygroscopic substances is clearly indicated'. The effect of temperature is comparatively unimportant.- In the case of cotton, for instance, an increase in temperature of 10 F has the same effect ori regain as a decrease in relative humidity of one per cent. Changes in temperature do, however, affect the rate-of absorption or drying. Sudden changes in temperature cause temporary fluctuations in regain ' even when the relative humidity remains stationary., The regain or moisture content affects the physical properties of textiles to a marked degree, changing the strength, pliability and elasticity. The fact that the regain of textiles will come into equilibrium with the Industrial Air Conditioning 829 Table 2. ; Regain op Hygroscopic Materials Moisture Content Expressed in Per Cent of'Dry Weight of the' Substance at . * Various Relative Humidities--Temperature, 7.5 F CUESF rlCATION Material - Description Relative Humiditt--Per Cent Acthobitt 10 20 30 40 50 60 ' 70 80 90 Cotton Cotton Sea island--roving American--cloth 21 3.7 4.6 51 6.6 7.9 91 111 14.1 Hartshorne 2.6 3-7 4.4. 5.2 5.9 61 .8.1 too 141 Schloesing Cotton Absorbent 41 9.0 115 15.7 181 201 221 241 251 Fowa Natural Textile Fibers Wool Silk linen Australian merino--skein 4.7 7-0 8.9. 108 118 14.9 171 19.9 23.4 Hartshorne Raw chevennes--skein 3*2 5.5 6,9 8.0 8.9 10.2 11.9 141 18.8 Schloesing Table doth 1.9 2.9 3.6' 41 5.1 6.1 7.0 8.4 102 Atkinson linen Dry spun--yarn 3.6 5.4 61 71 8.1 8.9 91 111 131 Sommer Jot* - - Average of several grades 3.1 5.2 6.9 81 102 12.2 14.4 17.1 20.2. Storch Hemp Manila,and sisal--rope 2.7 4.7 6.0 7.2 81 9.9 11.6 13.6 15.7 Fuwa Rayons ' Viscose Nitrocellu lose Cupramonhun Average skein CefluloBe Acetate Fiber 4.0 5.7 64 7.9 9.2 101 12.4 141 16.0 Robertson 01 1.1 1.4 1.9 2.4 3.0 3.6 41 51 Robertson M. F. Newsprint Wood pulp--24% ash 2.1 3J 4.0 4.7 51 6.1 71 8.7 10.6 U. 8. B. of S. H. M. F. Writipg Wood pulp--3% ash 3.0 4.2 5.2 61 7.2 81 9.9 11.9 14.2 H.8. B. of S. Paper White Bond f - Rag--1% ash 2.4 3.7 4.7 5.5 -61, 71 81 10.8 13.2 U. S. B.ofS. Com. Ledger 75% rag--1% ash 3.2 4.2* 5.0 5.6 6.2 6.9 8.1 103. 13.9 U. 8. B. of S. Kraft Wrapping. Coniferous 3.2 4.6 5.7 6.6 7.6 8.9 101 12.6 14.9 D. R B. of 8. Leather Sole oak--tanned 5.0 8.5 11.2 15.6 16.0 181 20.6 24.0 29.2 Phelps Catgut Racquet strings 4.6 7.2 8.6 102 110 14.3 171 19.8 21.7 Fuwa Glue Misc. Organic Rubber Materials Wood Hide, Solid tire Timber (average) . 3.4 41 5.8 6.6 7.6 9.0 10.7 11.8 121 Fuwa an 021 032 044 014 0.66 016 0.88 099 Fuwa 3.0 4.4 5.9 7.6 91 111 14.0 17.5 22.0 Forest P. Lab. Soap White 1.9 3.8 5.7 7*6 10.0 12.9 16.1 19.8 231 Fuwa Tobacco' Cigarette ` : 5.4 8.6 11.0 131 16.0* 191 25.0 331 500' Ford White Bread ' 05 L7 3.1 i 6.2- '81; 11.1 141 19.0 Atkinson Crackers - 2.1 18 3.3 3.9' 5.0 61 81 10.9 14.9 Atkinson Foodstuffs Macaroni Floor 5.1 7.4 8JJ 102 11.7 13.7 161 19.0 22.1 Atkinson 16 4.1 51 6.5 8.0 9.9 114 15.4 19.1 Bailey Starch Gelatin T; ' ' 12 >.8 5.2 6*4' 7.4 81 91 10.6 12.7 Atkinson 07 1.6 2.8'. 3.8. 4.9- 6.i 7.6 91- 11.4 Atkinson Asbestpe Fiber Finely divided 016 0.24 .0.26 012 041 051 062 073 014 Fuwa Silica Gel ' ` * Mac. Inorganic Domestic Coke Material Activated Charcoal Steam activated , '5.7 9.8. 117 is.2; 17.2 1818 201 211 22.6 Fuwa 0.20 .040 061 081 1.03 114 1.46 1.67 119 Sehrig . . - 7.1 14.3 218 26.2 281 291 300 3L1 32.7 Fuwa Sulphorle Add - ' HtSOt - 33.0 41.0 471 515 57.0 611 67.0 731 821 Mason conditions of the surrounding air and vary with its temperature and relative humidity is the fundamental basis for the control of, physical qualities-during manufacture. During the preparation processes in-a cotton mill, the cotton fibers should be in a condition to be easily carded. These, preliminary processes are carried out best in a relative humidity