Rayon fabrics treated with ammonium sulfate were heated in the temperature range of 120 to 340°C in air and in nitrogen atmosphere, and the changes in the physical properties were investigated.
The results show that the temperature dependencies of the physical properties have inflections near 180°C. In the range of 120 to 180°C, dehydration and depolymerization seem to mainly proceed, being accompanied with weight loss as well as decrease in tensile strength. However, above around 180°C, the different but noteworthy changes were observed, namely, 1) marked increase in tensile strength, 2) release of carbon and introduction of nitrogen, 3) loss of solubility and changes in density. These may suggest that the introduced nitrogen plays an important role in recombining the splitted denatured molecules and hence in tightening the structure of the char.
Furthermore, an excellent flame-resistant fabric has been prepared by application of the procedure above mentioned. This fabric has a high L. O. I. value of 47, unmeltability, high hygro-scopicity and also excellent thermal and electrical insulatabilities, so that it seems to be useful in the fields where hazardous thermal environments exist.
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