Study On The Softening Treatment Of Ramie Fibers

Natural ramie fibers have the advantage of coolness,high permeability,moisture absorption,antibacterial function etc.It is high quality raw materials of clothing fabrics.However,ramie fibers have high degree of crystallinity so that it leads to the stiffness,the poor dyeability and elasticity.More importantly,the thick and rigid ramie fiber ends on the fabrics can apply a strong protruding force on skin and cause itchy feeling.This issue can hinder ramie fibers for development and application.In order to solve the drawback and improve the softness property of ramie fibers,N,N-dimethylacetamide(DMAC)was used to swell and reduce the crystallinity of ramie fibers.The effects of treatment process on the mechanical properties and softness of ramie fibers were studied which laid a foundation of the development of high-grade ramie fabric without tickling.The method of single factor experiment was used to investigate the effects of the concentration of DMAC,temperature,time and liquor ratio on the softening properties of ramie fibers.The results showed that DMAC can make ramie fibers more softer.The breaking strength of the ramie fibers showed the tendency of declining and then reached a balance state gradually,while the breaking elongation showed the tendency of increasing and then reached a balance state,and breaking rotation number showed the tendency of increasing and then gradually decline with increasing the DMAC mass fraction,treatment time and temperature.The optimum treatment conditions were 20% DMAC mass fraction,2 h time,80 ℃ temperature and 1:20 liquor ratio.The ramie fibers treated in the optimum conditions became rough and had some cracks on their surfaces but the original ramie fibers were smooth.The crystalline regions of fibers treated DMAC were reduced and the amorphous area was increased.The crystallinity of ramie fibers was decreased from 80.73% to 70.36%.The dyeing property of ramie fibers was improved,the dyeing rate was increasing about 2.5 times and fixation efficiency was enhanced by 32%.By design and analysis of the response surface method,it was concluded that when the DMAC mass fraction was 19.7%,time was 2 h,temperature was 75.4℃,the properties of ramie fibers had achieved their best.At the same time,the breaking strength,the breaking elongation and the breaking rotation number were 4.21 c N·dtex-1,4.42% and 456.6 times respectively.The predicted value was consistent with the measured value,which can illustrate that the model equations were accurate and reliable.In order to reduce the usage of DMAC,the ramie fibers were pretreated by sodium hydroxide.Although the pretreatment of Na OH could enhance the effect of DMAC to ramie fibers,the mass fraction of Na OH should be limited in 5% to meet the requirements of fiber strength.It was found that the treated scheme of 5% Na OH mass fraction pretreatment and 15% DMAC mass fraction was not only improve the softening property of ramie fibers,but also decline the usage of DMAC.What’s more,the damage of fiber’s breaking strength was also reduced.