An analysis has been made of the factors involved in the A.S.T.M. Trapezoid Tear-Strength Test. The tear strength of a fabric measured by this test is dependent mainly on the extensibility of the threads, the breaking strength of the threads, the effective specimen length, and the number of threads per inch of fabric. An analytical interpretation of the part played by each of these factors resulted in a general equation relating tear strength to the breaking strength and extensi bility of a given fabric. The evaluation of the derived equation gave a good correlation between the calculated and measured tear-strength values of the fabrics investigated.

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Experiments relating to the chemistry of the technologically important cellulose-formalde hyde reaction are described. While for many reasons definitive statements about the reaction cannot now be given, certain of its gross features are revealed. As the formalization process is usually carried out, the reaction with cellulose is com petitive with the evaporation of the formaldehyde. At low temperatures (to 30°C) no reaction takes place. At higher temperatures (150°C) reaction takes place over a wide range of con ditions of acidity. The product formed at high acidity is stable to hydrolysis and is charac terized by reduced swelling, increased elastic modulus, and resistance to creep. At lower acidities and under alkaline conditions, the properties of the product are much more like those of the starting material and the formaldehyde is easily removed by washing in neutral aqueous solutions. The combining weight of formaldehyde with cellulose varies, among other things, with the concentration of the formaldehyde applied. The lower the concentration the more nearly the combining weight approaches 12, which corresponds to the formation of simple methylene ethers with the cellulose. At higher concentrations, the combining weight increases toward a value of 30, indicating the formation of polyoxymethylene ether linkages.

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A review and an a nalys is of the t heor y of water repellency of textile fab ri cs have been made. The physicochemical basis underl ying the we ttability, or wa ter repe llency, of t reated fabrics is di sc ussed. A survey of the laborator y test methods for e valuating water repe lle ncy of tex til e fabri cs is presented . A s tudy wa s made of 'the water-rep ellent properties of 11 commercial ra in coat and 4 mi li tary fabric". For this s tudy two of th e more recent test methods were examined , the drop-penetration and the contact-angle tests. Two other , and older, test m e thods were a lso studied, the spray-rating and the hydros taticpress ure tests. Several exploratory observations were made in an attempt to dete rmi ne the mechanism by which water-repell en t fabrics lose the ir repellency when exposed to rai n.

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