Improvement in the Stretching Property of Paper Yarn by Shape Memorization Produced with High-pressure Steam Treatment

The demand for paper yarn has increased as a textile fabric because of its light weight and low static electricity. However, paper yarn wrinkles easily and its softness and stretching properties are low. So we attempted to improve the stretching property of paper yarn by the high-pressure steam method which could provide a shape memorization to cellulosic materials. The most suitable condition based on our finding was steaming at 170 °C for 2 min after soaking in 0.28 % NH3 aqueous solution. By this treatment, over 84 % of the number of twists of paper yarn was maintained while the strength decreased to 78 %. For the paper yarn twisted together with viscose rayon filament, the number of twists was maintained at 94 % at 120 °C for 2 min of steaming without pre-treatment while the strength decreased to 85 %. The most desirable stretching property was achieved by the multi-twisting at 400 r/m of ten paper yarns, followed by high-pressure steaming. X-ray diffraction and CP/MAS 13C-NMR revealed that the crystallinity was increased 2 %, and the width of cellulose micelle was much larger by high-pressure steaming. Iβ type rich crystals of Manila hemp cellulose were stable at the steaming condition, so little transformation of the crystal type was observed. However, the orientation of the crystal was slightly improved by high-pressure steaming. It was considered that the mechanism of permanent shape memorization was derived from some recombination of the hydrogen bonds in the crystal region. High-pressure steaming was effective in the shape memorization of cellulosic fabrics and then the method improved the stretching property of textile made of multi-twisted paper yarns.