John C. Whitwell

Statistical Treatment of Data and Extreme-Value Theory in Relation to Fatigue in Textiles

The use of central measures of lifetime to characterize fatigue behavior is misleading, and more attention should be paid to early failures and expected minimum life. Differences in the dispersions of lifetimes between samples may lead to faulty conclusions if these are based on mean lifetimes. The possible dependence of dispersion on stroke is considered. Because of dispersion in fatigue data, it is necessary to test large numbers of specimens to make reliable predictions. The inadequacy of observed central values as bases for judging the applicability of a distribution is discussed. Criticism leveled against the commonly used logarithmic-normal distribution is cited. Criteria are presented for the development of a lifetime distribution that takes into account the physical realities of the fatigue process. Analytical expressions for a number of concepts in the statistics of fatigue are reviewed. The theory suggesting the application of the third asymptotic distribution is outlined. The distribution has been adapted to accumulated fatigue data on an acrylic fiber sample.

The Amino Acid Compositions of Several Wool Fractions as Determined by Paper Chromatography

A paper chromatographic study of the amino acid compositions of several histo logical fractions of wool has been conducted. The fractions considered were epicuticle, cortical cell membranes, paracortex, and regenerated oxidized keratin. Samples of these fractions were hydrolyzed with hydrochloric acid, and quantitative analyses of the amino acid content of these hydrolysates were accomplished through a modification of the standard two-dimensional paper chromatographic technique. The epicuticle was found to contain normal amounts of cystine but extraordinarily large quantities of aspartic acid and glutamic acid. In addition to confirming the results of the phosphotungstic acid analyses for cystine reported in a previous paper [14], the chromatographic studies of the paracortex showed large amounts of the basic and small amounts of the dicar boxylic amino acids to be present. The extremely low total of amino acid content found in the cortical cell membranes indicated the possible presence of some nonprotein constituent.

Reduced Designs of Resolution Five

The two level fractional factorial designs of resolution five enable the experimenter to estimate independently all main effects and two-factor interactions under the assumptions that higher order interaction effects are negligible. By relaxing, very slightly, the requirement that all two-factor interactions be estimable, or that all estimated effects be orthogonal, the number of runs required for many resolution five designs can be greatly reduced.

Studies of Nonwovens: Part I : A Multivariable Approach

The performance characteristics of nonwoven fabrics have been studied as a function of fiber properties, binder properties, and web construction. The particular type of nonwoven selected for study was a web of random-laid base fibers in which randomly placed thermoplastic fibers provide the bonds. The responses studied were those related to rupture, elastic, and handle (aesthetic) properties. Fourteen variables were investigated: Base fiber linear density, base fiber staple length, amount of crimp in base fiber, post-yield extension of base fiber, type of binder, linear density of binder, staple length of binder, binder concentration, mass per unit area of nonwoven, amount of needle looming, number of laminations per web weight, pressure of bonding, temperature of bonding, and time of bonding. The performance characteristics measured as a function of these variables were maximum tenacity at dry and wet conditions, elongation at dry and wet conditions, tear strength, abrasion resistance, elastic modulus at dry and wet conditions, proportional limit at dry and wet conditions, crease recovery, bending length, flexural rigidity, bending modulus, bulk density, and air permeability. Crimp, linear density, and staple length of the base fiber influence rupture, elastic, and handle prop erties, as expected. Binderproperties, other than type, have no effect due to the destruction of the fiber in the bonding process. Bonding conditions, particularly pressure and temperature, are extremely influential in all types of properties. These variables govern the effectiveness of the bonds. Concentration of binder is extremely important to all types of responses since it governs the number and distribution of bonds. Needle looming affects only rupture properties.

Thermal Resistance Factors in Differential Scanning Calorimetry

In the analysis of heat flow processes in differential scanning calorimetry it has been generally agreed(O’Neill) that the controlling thermal resistance is between sample container and sample holder, and, consequently, that the sample and sample container are at the same temperature. The thermal equation applying to this situation, usually referred to as Newton’s Law, is

The Viscosity of Newtonian, Pseudoplastic, and Dilatant Liquids: Use in the Measurement of the D.P. of High Polymers

\frac{{d{q_s}}}{{dt}} = \frac{{{T_p} - {T_s}}}{R}

Thermomechanical Behavior of Nonwovens: Part I: Responses to Changes in Processing and Post-Bonding Variables

(1) where dqS/dt = total rate of flow of thermal energy to the sample, Tp = programmed temperature, Ts = sample temperature, and R = thermal resistance.

Properties of Apparel Wools II. Modification of Fiber Surface During Worsted Processing

Mechanical processing of cotton causes two types of damage: the first type is physical in nature, resulting from the breaking and bruising of fibers; the second type is chemical in nature, as shown by a decrease in D.P. This change in D.P. is brought about by a mechanical-chemical rupture of molecular bonds and not through a thermal mechanism. A quantitative estimate of the relative damage occurring in each mechanical operation investigated is presented. A loss in D.P of 30 percent was measured as a result of the mechanical operations which converted an Empire seed cotton into yarn.