聚丙烯腈基初生纤维在牵伸过程中凝聚态结构变化的研究

Aggregation structure development during the stretching process of polyacrylonitrile(PAN)nascent fibers

利用XRD和拉伸恢复率等分析聚丙烯腈初生纤维在牵伸过程中凝聚态结构的变化规律,并得到初生纤维的玻璃化转变温度Tg。水洗纤维在水中的Tg为70℃,干燥后纤维在硅油中的Tg为90℃。纤维在90℃水浴中牵伸时,伸长率小于15%时为弹性形变,大于25%时为强迫高弹性形变,纤维的结晶度、晶粒尺寸和晶区取向度在伸长率小于45%时随牵伸倍数的增加而增加。纤维在90℃硅油中牵伸时,弹性形变和强迫高弹性形变比在水中小,纤维的结晶度和晶粒尺寸减小,晶区取向度增加。说明水对纤维起增塑作用,并且分子链的滑移和排入晶格使纤维无法恢复到拉伸前长度。

The relationship between the tensile behavior and the aggregation structure of the PAN nascent fibers were studied by tensile recovery and XRD, and the Glass-Transition Temperature Tg were obtained. Tg were 70℃ in the water and 90℃ in the dimethyl silicone oil respectively. When the fiber was stretched in the water at 90℃, the deformation was instantaneous elastic deformation below 15% elongation and was forced high-elastic deformation above 25% elongation. The crystallinity, crystal size and crystal orientation increased with the stretching below 45 % elongation. When the fibet was stretched in the dimethyl silicone oil, instantaneous elastic deformation and forced high-elastic deformation were smaller than those in the water. Moreover, the crystallinity and crystal size decreased and crystal orientation increased. These results indicated that the intermoleeular forces decreased and molecular chains were easy to form crystal under the action of water molecules during the stretching process. In the other words, the water played an important plasticization effect on the fibers. The reason for the fiber length could not recover before the stretch was the permanent relative displacement of fiber elements and the increasing of crystallinity.