Effects of drying conditions on properties of textile yarns

Abstract

Yarns made from raw cotton, "purified" cotton , merceri7.edcotton, clothing wool, carpet wool, viscose rayon, cuprammonium rayon, cellulose acetate, and degummed silk were saturated with water and t hen exposed for perions of }of to 6 hours in air having temperatures of 221 °, 257°, and 302° F and absolute humidities of approximately 1, 55, and 95 p ercent, respectively.After conditioning the dried yarns for at least 24 hours in air of 65-percent.relative humidity and 70° F, measurements were made of the breakin g strengths, elongat.ions at break, and moisture contents of the yarns; the fluidi ties of dispersions of thc cellulosic fibers in cuprammonium solution, of the s ilk in aq ueous zinc chloride, and of the acetate in aqueous acetone; and the r elative affinities of the cellulosic fibers for the dye benzopurpurine 4B and of the wools for acid dyes . .Heat ing the yarns for 6 hours at 221° F at each of the three humidities weakened all of them.The breaking strength and elongat ion at break of t,he viscose, cuprammonium, degummed silk, and cotton yarns decreased st.ill more at higher temperatures.In comparison with heating at I-percent absolute humidity, heating at 95-percent absolute humidity res ul ted in lower break ing strengths and elongations at break for a ll yarns except the raw cotton, higher fluidities , lower affinity of cellulosic fi bers, and higher affinity of wool fibers for the d yes.H eating for Yz hour at 302° F had little effect, on the properties of the yarns except the viscose and cuprammonium rayon, which were adversely affected.The damage which occurred at a given temperat,ure and humidity increased throughout the heating period. CONTENTSPage manufacture, and to controlled and duplicable conditions of temperature, relative humidity, airflow, and thoroughness of exposure, it was possible to obtain data which may be considered basic to all types of textile drying.The results are given in this paper. II. MATERIALSThe characteristics of the yarns and the purification treatments they received are given below.Where treatment with water is indicated, distilled water was used.The raw cotton yarn (1/24)2 was washed thoroughly in water.The "purified" cotton yarn was prepared from the raw cotton yarn by successive extractions with alcohol, ether, and I-per cent NaOH solution, followed by rinsing in 5-percent acetic acid solution and then in water.The mercerized cotton yarn (2/25) was washed in a 5-percent NH40H solution, then rinsed in water.The clothing wool yarn (2/2.3) and the carpet wool yarn (3 /1.2) were extracted with alcohol and ether, and rinsed in warm water.The viscose-rayon yarn (1/30; commercial designation 150 denier, 40 filament), the cuprammoniumrayon yarn (1/30; commercial designation 150 denier, 112 filament), and the cellulose-acetate yarn (1/30; commercial designation 150 denier, 46 filament) were washed in a warm I-percent NH40H solution, then rinsed in warm water.The degummed silk yarn was prepared from a raw silk yarn (4 /75) by degumming with an olive oil soap solution, followed by rinsing in warm water.'The typp system for designating sizes of yarns is employed.The first number (1 in the case of the raw ootton yarn ) indicates the num ber of units of wbicb tbe yarn is composed, that is, the ply.The second number (24 in the case of the raw cotton yarn) indicates the nnmber of thousands of yards of the finished yarn in 1 pound.3 J.G. W iegerink, Equipment [or conditioning materials at constant humidities and at elevated temperatures, J .Research NBS 24.639 (1940) RP1303.• The term "relative humidity" as used in this report is the ratio of the actual pressure of water vapor to the maximum posRible pressure of water vapor in the atmosphere at the same temperature, expressed as a percentage.The teem "absolute humidity" as used in this report is the actual percentage by volume of water vapor in the system.