碱处理后苎麻的微结构及物理性能

THE FINE STRUCTURE AND PHYSICAL PROPERTIES OF MECERIZED RAMIE

用不同浓度的烧碱及不同的张力对苎麻纤维和纱线进行处理,观察并测定苎麻在烧碱溶液中的长度收缩情况,碱处理前后苎麻的结晶度、取向度、密度、吸附性能和力学性能。实验发现,在20℃条件下,碱液浓度达12％时,苎麻的长度收缩率急剧上升,结晶度、取向度、密度以及纤维强度大幅度下降,断裂伸长率成倍地增加,弹性回复性能明显改善,吸附性能大大提高.烧碱浓度达16％左右.这一系列变化基本达最大值.碱处理时轴向张力会阻止苎麻微结构及性能的这些变化。实验认为,经低张力或无张力碱处理后,苎麻纤维无定形密度下降,无定形部分取向下降很多;即使经过较为彻底的碱处理后,纤维中仍有部分纤维素Ⅰ存在。

This paper discribed the fine structure and physical properties of ramie fiber which was treated with various concentrations of sodium hydroxide at 20℃ for 5 min. And those of ramie yarn with different shrinkages were also discussed.The swelling and shrinkage along length of ramie fiber are low when the concentration of NaOH is below 12%, and steeply rise at 12% or higher, the maximun changes take place at 16%.After mecerizing, the crystallinity, orientation, density, absorption and mechanical properties of ramie fiber are changed. The changes are unremarkable when the toncentration of NaOH is below 12%. When the concentration of NaOH reaches 12% or higher, the crystallinity, orientation, density and tenacity of ramie fiber will drop markedly; but the absorption properties and elongation at breaking increase sharply, and the elastic recovery is improved obviously. All of the fine structures and properties have the maximum change at 16% NaOH. The tension along length during mercerizing impedes the changes of the fine structure and physical properties.It is found that the density of amorphous region of ramie fiber decreases after caustic soda treatment. And the optical orientation of ramie decreases more than x-ray orientation after mercerizing. So it is believed that the orientation of amorphous of mercerized ramie declines much more. We are sure that cellulose crystal does not transfer completely from cellulose I to cellulose II even the ramie is deeply mercerized.