Study On Softness Treatment Of Ramie Fiber

Ramie fibers have many characteristics of high air permeability,moisture absorption and antibacterial activity.However,macromolecular chains arrange tightly and orderly,and crystallinity is high,resulting fibers with high modulus and low softness.It's difficult for ramie fibers to bend and tangle in spinning,which leads to much yarn hairness and causes prickle in wearing.In order to improve the softness of ramie fibers and improve their application value,N-methylpyrrolidone(NMP)was used to swell and decrystallize ramie fiber,and the effects of treatment on softness and tensile properties of ramie fibers were studied.First of all,NMP was used to treat ramie fibers,the effects of NMP mass fraction,t time and temperature on the softness and tensile properties of ramie fibers were explored.Meanwhile,the crystallinity and chemical groups of treated and untreated ramie fibers were charactered by X-ray diffractometer and infrared spectrometer.Results show that twisting number enhanced early and then reduced with NMP mass fraction and time increasing,while it enhanced quickly and then keep stable with temperature increasing.Tensile strength of ramie fibers reduced and elongation enhanced when NMP mass fraction,time and temperature increased.The optimum treatment conditions in single factor anysis were NMP mass fraction 15%,time 60 min and temperature 80?.Meanwhile,the degree of crystallinity of treated ramie fibers was reduced by 12.67%;chemical groups remain unchanged.Then,to optimize the softness treatment of ramie fibers,Box-Behnken Design combined experiments were analysed by response surface method based on single factor study,the significance of each factor for twisting number,tensile strength and elongation were analyzed,and the regression equations of factors and indexes were established.After optimizing the process by response surface,the optimum treatment conditions were NMP mass fraction 12.5%,time 69 min and temperature 79 ?.Under the condition,the predicted values were close to actual values.The regression equations were accurate and reliable.Compared with untreated ramie fibers,the softness and ductility increased by 67.27% and 38.60%,respectively,while tenacity decreased by 41.66%.Compared with the single factor,NMP mass fraction in the optimum condition of response surface increased by 16.77%.Finally,in order to enhance the efficiency of the use of NMP and ensure the effects of the softness treatment,Na OH was combined with NMP to treat ramie fibers.The effects of the mass fraction of Na OH and NMP on the softness and tensile properties of fibers were researched,surface's changes of treated and untreated ramie fibers were observed by scanning electron microscope.Results show that when the mass fraction of Na OH and NMP increased,the twisting number and elongation enhanced,however,tenacity and modulus reduced;When swelling,the surface of ramie fiber became smooth because residues were removed,then ramie fiber split off and got rough because of drastic swelling.The best combined treatment of Na OH and NMP for ramie fibers was Na OH mass fraction 6% and NMP mass fraction 10%.Under the condition,the twisting number,tenacity,elongation and modulus of ramie fibers were 467,5.20 c N·dtex-1,3.89% and 139.13 c N·dtex-1,respectively.Compared with untreated ramie fiber,the twisting number and elongation enhanced by 67.99% and 36.49%,tenacity and initial modulus decreased by 49.27% and 51.89%.Compared with single factor and response surface,the softness of ramie fibers was great,and NMP mass fraction in the best combined treatment of Na OH and NMP was decreased further.