George Macon Bryant

Stiffness and Resiliency of Wet and Dry Fibers as a Functi of Temperature

The cotton and cottonseed industries are modernizing technical methods and instruments along with suppliers of other raw materials. Described herein is an improved electrical conductivity instrument for measuring rapidly and accurately the moisture content of lint cotton, seed cotton, and cottonseed. Moisture contents in percentages, based on total weights of samples, are indicated on a direct reading dial. Accurate measurements of ± 1% in the 3.3-22% moisture range are obtainable with this instrument when compared with standard oven metheds. A relatively large representative sample (35 g. lint cotton, 100 g. seed cotton and cottonseed), control of sample density (600 lb./sq. in. pressure), and a stable electrical system are the contributing factors for a successful instrument. Background of Development The industry has long recognized the need for a rapid and accurate method of determining the moisture content of cotton and cottonseed samples. As early as 1875 an international conference assembled in Switzerland to adopt standards for moisture regain in textile fibers and fabrics. Since then research has continuously provided a wealth of information on this subject; as a result, a number of useful instruments have been developed to measure moisture content. Essentially all of the instruments developed to date that operate with speed and accuracy are of the elecI trical type, and these instruments can be divided into two general classes : the capacitance type, in which the dielectric constant is associated with nwisture; and the conductivity type, in which the electrical resistance of the sample is correlated with the percentage of moisture. Of the two, the resi~oe method is the nwst popular. Ed’ef sen [ 2 ] summarized the potentials of the dielectric method for measuring the moisture content of textik materials; more recently, Heark (3) has investigated the dielectric properties of fiber sasanblies. Whitten and coworkers 141 concluded that the resistance method is the most practical for cottonseed.

Effect of Elongation and Temperature on the Recovery and Apparent Glass Transition Behavior of an Experimental Modacrylic Fiber

The shape of the stress-strain curve of the modacrylic fiber is correlated in a definite manner with the stress-relaxation and recovery behavior. At the yield point, where the stress-strain curve has minimum slope, the tensile recovery decreases most rapidly with increasing elongation, and the rate of stress relaxation passes through a maximum. Above the normal (low-strain) glass transition temperature of the fiber (90° C.), the stress-strain curve no longer has a yield point, and the recovery and stress-relaxation behavior become relatively independent of elongation. The tensile- and work-recovery values show a definite minimum (permanent set shows a maximum), occurring at the glass transition temperature at low, 1%, strain, and shifting to lower temperatures with increasing elongation. This shifting of the minimum in the recovery-temperature curves is interpreted to indicate a lowering of the glass transition temperature with stretching. At temperatures of 25° and 60° C., the yield strain approximates that elongation required to reduce the minimum in the recovery-temperature curves to that temperature. These results lead to a fundamental definition of the yield point as the strain level at which the glass transition temperature is lowered to the experimental temperature. A free volume increase accompanying stretching is postulated as the underlying mechanism whereby the glass transition temperature is reduced. The equations of Ferry [13, 14] indicate that a quite reasonable value of 0.35 for Poissons ratio could lead to an increase in free volume sufficient to speed up the molecular response by a factor of 105 at the yield strain.

Dynamic Sorption of Semistable Foams by Fabrics Part I: Implications for Textile Foam Application Processes1

Foam is an effective medium for chemical treatment of fabrics at low wet pickup, due to the expanded volume and large internal surface area of the foam bubbles. For a high speed continuous process combining foam application and dissipation steps, foam of limited stability, with high shear susceptibility and dynamic sorption rate is needed. Such semistable foams require delivery of uniformly aged foam to the fabric under positive hydrostatic pressure and precise control of the foam-fabric contact time to achieve uniform distribution in the substrate. For these reasons, semistable foams cannot be applied uniformly by conventional coating methods using a doctor blade and foam bank of variable dimensions. Conversely, stable foams applied by coating methods lack the rapid dynamic sorption rate needed for high speed single- step application. A mechanism of high speed foam application is proposed, whereby the breaking foam is distributed through the fabric via yam interstices under hydrostatic pressure, and the broken foam liquor wets the interfiber pores driven by interfacial forces. Wetting rates are calculated using typical FFT process operating conditions and cotton fabric geometric parameter estimates. The results indicate that through-fabric wet- out is completed during the interval when the fabric is over the applicator slot. The wetting of interfiber pores is predicted to be slower than through-fabric wetting, but rapid enough to be completed at the applicator. The comparatively rapid wetting rates of yam and fiber surfaces with respect to fiber swelling rates is postulated to make possible the uniform semistable foam application of finishing chemicals to hydrophilic fiber substrates at pickup levels substantially below their moisture ab sorption capacity.

Relation of Lubricant Structure to Frictional Properties : Polyoxyalkylene Monoether Lubricants on Filament Yarns

The fiber-to-metal frictional behavior of polyester, polyamide, and polypropylene multifilament yarns lubricated with random copoly (oxyethylene-oxypropylene) monoethers having number average molecular weights ranging from 360 to 4200 has been studied over the sliding speed range of 0.01 to 400 m/min and temperatures from 21 to 225°C. It has been found that striking similarities exist between the frequency dependence of dynamic mechanical properties of the bulk lubricant polymers and the speed dependence of dynamic fiber-to-metal friction exhibited by the copolyether lubricants. Plots of yarn tension vs. sliding speed pass through a maximum, and the speed at which friction reaches its maximum value, U max, is inversely related to the lubricant molecular weight (Mn ). By plotting U max against the reciprocal average molecular weight, a straight line of positive slope is obtained in agreement with a transformed expression of the Fox-Loshaek equation relating reciprocal molecular weight and the lubricant glass transition temperature. These indications of a fundamental relationship between the maximum in the friction versus sliding-speed curve and the frequency of the maximum for the dynamic mechanical loss modulus of the lubricant polymer are further substantiated by the temperature dependence of U max, which follows an Arrhenius type equation. At low sliding speeds, below 10 m/min, the fiber-to-metal friction of the copolyoxyalkylene monoether lubricants is largely governed by the hydrodynamic effect of the lubricant film. Thus, the relation between the friction force F, speed U, and the steady state viscosity of the lubricant η can be described by the expression F = k(ηU)1/ n , where the constant k is dependent on the fiber polymer, and the constant n is independent of the fiber type.

Influence of Resin Add-on and Co-applied Water in Foam Finishing of Cotton Fabric

Multiple regression analysis is used to determine the effect of resin add-on and co-applied water in crease resistant finish on cotton. Dry crease recovery angle (DWRA) and tear resistance of treated fabrics are measured. Regression equations show that increasing resin add-on increases DWRA and decreases tear resistance. Conversely, increased co-applied water reduces DWRA and increases tear resistance. A hypothesis is presented to account for the independent and interactive effects of resin add-on and the amount of co-applied water, when used with the FFT process.