For certain occupations special clothing is worn t provide protection against heat and fire; the amount of protection needed varies widely with the specific occupation. Fabrics made from natural fibers have been traditionally used for ordinary protection such as that needed in routine work situations of foundary workers, firefighters, etc. This study was conducted to determine the insulative properties of fabrics as measured in single layers, as well as their retention of integrity under various heat loads. Fabrics investigated ranged in weight from 85 to 740 g/m 2 and varied in fiber content, color construction, etc. Radiative heat was supplied by a quartz panel at flux levels of 0.84 to 1.68 W/cm2; an open flame provided convective heat at 8.4 W/cm2. The total heat transferred through the fabric after exposure, and the time to reach a second-degree burn injury (based on the Derksen curve), were used to evaluate insulation characteristics. The report describes the apparatus, the test methods, and procedures used to conduct the study., Some interpretations of the results are presented.
SynopsisPreliminary thermal studies were made of cotton fabrics which had been made flame resistant by chemical modification or by blending with a flame-resistant modified acrylic fiber. DTA and TGA thermograms were made in both nitrogen and oxygen atmospheres. Differences were found in the thermograms of the untreated controls, depending upon amount of purification. Fabrics treated with the flame-retardant formulations had lower decomposition temperatures and higher percent residue. Decomposition in oxygen was more complete and proceeded a t a lower temperature. Infrared spectra of selected samples, which had been partially or completely charred, were examined. These data are related to theories about the degradation of flame-resistant cotton fabrics.
Wet and dry density measurements were made on a wide variety of wash-and-wear cotton fabrics and some interpretations of these values are given. Methylenated cotton was selected for more extensive fundamental study because of the simplicity of the formaldehyde cross link and the fact that formaldehyde can be reacted with cotton under greatly different conditions. Formaldehyde was used to cross link cotton print cloth at various degrees of fiber swelling by reacting in systems ranging from completely aqueous to anhydrous using hydrochloric acid as catalyst. The amount of water in the system at the time of reaction is related to the extent of fiber swotting. The extent of swelling at the time of cross-linking and the extent of cross-linking influence wet density, which may be considered to be a measure of the water swellability of a fiber. Cross-linking tends to fix or stabilize a fiber in a given state of swelling: the stabilization is more effective when the cross-linking is done in nearly anhydrous systems. The state of swelling at the time of cross-linking modifies moisture regain, water of imbibition, dyeabitity, and wet and dry wrinkle recovery. There seems to be an optimum water content in the reaction system at the time of cross-linking for maximum dry and wet wrinkle recovery. As the water content in the reaction system is increased beyond the optimum, the amount of dry wrinkle recovery becomes much less than wet wrinkle recovery. This phenomenon leads to vastly different wash-and-wear ratings of fabric.A mechanism is presented diagrammatically to explain wet and dry wrinkle recovery. The mechanism is based upon hydrogen-bond cross links, covalent-bond cross links, and the position of the two types of cross links.AL.'FHOUGH wrinkle resistant cotton fabrics have heen known for about 30 years, many of the basic principles for imparting wrinkle recovery are not too well understood. The wrinkle recovery and washand-wear characteristics of a textile are affected by its construction and by the construction of the yarns of which it is composed. However, the properties of the fiber which make tip the yarn and fabric have, perhaps, an even greater influence on wrinkle recovery and wash-and-wear properties. Cross-linking within the fiber seems to have been accepted by most researchers as the hasic requirement for wrinkle recovery. It provides an excellent way of changing many of the properties of cotton fiber. The physical properties of cross-linkeci goods are quite well known, but the principle of producing physical changes with -----.-----.. cross links within the microstructure of the fiber, which is actually responsible for the fiber properties, is not too well defined. Differences have been observed between the wrinkle recovery of cotton fabrics finished by the pad, dry, and cure process and the wrinkle recovery of fabric finished while swollen in mercerizing strength alkali solution. The first of these processes, which is often thought of as reacted in the collapsed state, imparts wet and dry wrinkle recovery....
Information is given to explain why or how bromine or nitrogen contributes to phosphorus-containing flame retardants. Amide and amine nitrogen generally increase flame resitance, whereas, nitrile nitrogen can detract. Essentially, all of the phosphorus in a flame retardant is accounted for in the char or solid phase and this is also true when amide or amine nitrogen is present. Nitrile nitrogen can cause a significant reduction in percent phosphorus accounted for in the char. The amount of nitrogen accounted for in the char is dependent upon the type of nitrogen and the atomic ratio of N to P in the flame retardant. When large proportions of amide or amine nitrogen are present they also contribute to flame resistance in the gas or vapor phase. Bromine makes its contribution to flame retardants by acting mainly in the vapor phase, and its action appears independent of phosphorus.
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