【作者】 刘健；

【导师】 于伟东；

【作者基本信息】 东华大学 ， 纺织材料与纺织品设计， 2010， 博士

【摘要】 我国是牦牛的主要饲养国,约占世界总数的92%,具有丰富的牦牛毛纤维资源。牦牛毛纤维中大多数为粗毛,长度较长,但粗、硬、品质差,主要作为一般纺织原料,因此其经济价值一直较低。随着生活水平的提高,人们对于假发制品的需求日益旺盛,限于人发资源量的限制,使用牦牛粗长毛作为其替代品已被广泛应用。由于假发的利用纤维长度越长其价值越高,因此,增加纤维长度降低其细度是提升纤维价值的有效途径。人工拉伸细化工艺是目前对角蛋白纤维最有效的拉长变细的加工方法,但现有研究主要集中在羊毛细化,对于牦牛粗毛的拉伸细化报道很少。此外,人们对于牦牛粗毛纤维的认识也不够全面,这将为进一步的改性处理造成很大的困难。本文首次对我国产牦牛粗毛纤维的形态结构、皮质细胞特征、细胞及细胞间微细结构以及化学结构进行了细致研究。利用显微镜技术观察了牦牛粗毛纤维的外观形态结构,得到了单根纤维以及纤维之间的直径分布特点,同时阐述了纤维表面鳞片结构及截面特征。利用超声分离技术成功地分离出来牦牛粗毛纤维的皮质细胞,结合电子显微镜观察明晰了皮质细胞形态及其在纤维中的堆砌结构特征,并首次采用“长径比”指标表征皮质细胞形态,结果表明牦牛粗毛纤维皮质细胞整体形态较羊毛粗短,此外还对皮质细胞尺寸分布进行了研究。利用包埋技术成功制取到牦牛粗毛纤维的截面超薄切片,并利用透射电子显微镜观察到纤维的内部微细结构,发现多数纤维中含有髓腔,且纤维细胞无正副皮质之分,仅由单一结构组成。利用红外光谱技术得到牦牛粗毛纤维的红外光谱图,并分析其基本结构键吸收峰特征,结果表明其具有与羊毛相同的内部分子结构及结合键,但牦牛粗毛纤维内部无序结构多于羊毛。为了对牦牛粗毛拉伸进行工业开发,本文利用实验拉伸装置对无捻牦牛粗毛纤维片状拉伸工艺进行了研究,重点分析了影响工业连续化生产的相关参数。利用不同工艺条件下牦牛粗毛纤维片的拉伸曲线,结合低初始模量、大屈服区长度、大断裂点伸长、低拉伸断裂率的评价标准,确定了最优工艺条件,即预处理时间10min,最佳拉伸方式为多级变速拉伸,最佳纤维拉伸率为60%；通过正交试验及方差分析,以沸水回缩率为评价指标,确定了牦牛粗毛最优定型处理时间,即一次定型时间5min,二次定型时间3min,烘燥时间20min,焙烘时间3min。同时,开发了一种全新的片状纤维连续化拉伸方法,并首次采用预处理拉伸一体化拉伸方式,并通过AutoCAD软件对其拉伸设备进行了模拟。利用激光显微拉曼光谱技术,对拉伸过程中牦牛粗毛纤维二级结构的转变过程进行了深入研究,发现拉伸后牦牛粗毛纤维拉曼光谱酰胺Ⅰ带、酰胺Ⅲ带和C-C骨架振动区均发生了显著变化,但对纤维二硫键的影响不大；纤维拉伸细化过程中存在α螺旋大分子向p折叠大分子的转变,同时伴随着部分已转变为p折叠结构的大分子重新回复为α螺旋结构的过程,且对细化纤维进行沸煮处理也会导致这一变化发生。同时,本文借助广角X-ray衍射仪,对原毛及细化毛纤维的结晶度和取向度进行定量分析,结果显示拉伸细化处理对牦牛粗毛的结晶度有较大的影响,而对纤维取向度影响相对较小,拉伸细化过程中存在大分子或微结构块的滑移。机理分析发现,牦牛粗毛纤维拉伸细化机理应是“大分子构象转变”理论和“微结构体的滑移”理论两者相结合的一个更为复杂的过程,其中以“微结构体的滑移”机制最为主要。本文提出“大分子转变滑移”理论,其基本原理为：打开纤维分子间交联,部分保持分子内的相互作用；在外力拉伸作用下,大分子首先发生构象转变,继而出现分子、微结构体的滑移,同时伴随分子构象的往复变化；完成拉伸后,迅速重建分子间交联,实现纤维的拉长变细的同时保持纤维弹性。为了便于后期进一步的加工和使用,本文对拉伸后牦牛粗毛纤维形态、结构以及性能的变化进行了研究。结果显示：①纤维表面鳞片结构被劣化,覆盖密度随拉伸率的提高而降低,部分出现边缘翘起,甚至部分鳞片细胞出现滑移和损伤；②纤维直径显著降低,90%的细化纤维直径可比原毛减少约30%,截面形态由近圆形变为椭圆形：③纤维皮质细胞被拉长变细,在纤维中沿长度方向取向更加明显,排列更加紧密；④细化纤维的断裂强度和初始模量均高于原毛,且随着拉伸率的提高而逐渐增大,但断裂伸长率却呈现相反变化,另外,细化纤维抗弯刚度低于原毛；⑤细化纤维的摩擦系数逐步增大,其变化量随拉伸率增加而减小；⑥纤维浸润接触角随拉伸率的提高而逐渐减小,吸湿性大大增强,并极大地改善了纤维的染色性能,使低温染色变为可能。更多还原

【Abstract】 Yaks are mainly bred in China, and its number is over 92% in the world, thus there is rich resource of yak hair fiber. But most fibers among them are coarse and long, so they are basically used for slub materials with lower economic value. With the increase of living standard, the need for the production of wigs is increasingly strong by people. Due to the limit of the quantity of human hair resource, coarse yak hairs are widely used instead of it now. The longer the length of yak hair fiber is, the high the price of wig, thereby it is an effective way for raising fiber value to increase its length and decrease its diameter. The stretching slenderization is most efficient method at present for increasing fiber length, while the relatively research is mainly focused on wool fiber, and there is rare work to be report about the slenderization of coarse yak hair fiber. In addition, due to the tiny knowledge for coarse yak hair fiber, it will be very difficult to modify these fibers further.This paper studied amply the morphologic structure, cortical cell character, cell and substance between cells, and chemical structure of Chinese coarse yak hair fiber for the first time. Using scanning microscope electron (SEM) and optical microscopy observed the appearance morphological structure of coarse yak hair fiber and obtained the diameter distribution situation of single fiber and between fibers, at the same time it is revealed for the surface scale structure and character of cross section of fiber. Making use of ultrasonic separation achieved the cortical cell and observed its morphological and packing structure in fiber. The "length/diameter ratio" was put forward to characterize the shape of cortical cell for the first time, and the result show that the shape of coarse yak hair is thicker and shorter than that of wool fiber. Furthermore, the dimension distribution of cortical cell was also studied. The ultrathin section dyed was achieved very well using embedding method, and through the TEM the microfine structure of coarse yak hair fiber was investigated in detail. It was found that the medulla existed in most coarse yak hair fiber, and fiber is made up of one sort of cortex-cell but not the structure of ortho-and para-cortex. By FTIR techniques studied the basic absorbent apics characters of coarse yak hair and compared with wool fiber, it presented that two kind fiber have same inner molecular structure and bonding forms but the disordered structure in coarse yak hair fiber is more than wool.For the commercial development of stretching slenderization of coarse yak hair, the stretching process of the untwisted fiber sheet has been investigated, and the processing parameters which will affect the continuous production have been studied mainly. By means of strain-stress curves of coarse yak hair fiber stretching with different technological conditions and with lower initial module, longer yield region, lower breakage ratio as a evaluation criterion, the optimum process conditions were decided, i.e., the time of pretreating process is 10min, and the best stretching method is varying speed mode with 6 grade, and the stretch ratio should not exceed 60%. Using the retraction ratio of slenderized fiber in boil water as the evaluating indicator, the optimum setting time were found, i.e., first setting 5min, and second setting 3min, and drying process 20min, and baking process 3min. According to the slenderization process of coarse yak hair sheet, a whole new method of continuous stretching has been developed, and the relative machine has also been simulated, particularly adopted a new stretching method, i.e., all-in-one of pretreating and stretching.Through laser confocal Raman microscopy, the secondary structure transformation of coarse yak hair fiber during stretching process was studied in depth. It was proved that amide I, amide III and C-C backbone vibration regions all took notable change except for S-S bond. The result also showed that the conformation transformation occurred from the a-helical toβ-pleated-sheet in coarse yak hair fiber during stretching, meanwhile some a-helical macromolecule transformed would restore fromβ-pleated-sheet. This change could also be found when the fiber slenderized undergo boiling treatment. In addition, the degree of crystallinity and orientation has been analyzed quantificationally on coarse yak hair fiber after and before stretching. The results showed that the degree of crystallinity was changed obviously, while the change of degree of orientation is tiny. It follows that the slippage of macromolecule or microstructure mass exists during the stretching process. On the basis of the microstructure analysis to coarse yak hair, it was found that the mechanism should be a more complicated process for stretching slenderization of coarse yak hair, which involved "macromolecular conformation transformation" and "microstructure mass slippage", and the latter was primary. The mechanism of "macromolecule transformation and slippage" is put forward in present paper. Firstly, the crosslinks between the a-helical macromolecule are taken apart by the pretreating solution and keep partially the crosslinks inside the molecules. Secondly, the fibers are stretched by force, and the conformation transformation happened on the macromolecule first, and then the slippage of macromolecule and microstructure mass begin present, at the same time the reciprocate of the conformation of molecule arise. Finally, the stretched fibers are set quickly and restructure the crosslinks between molecules. This will keep the length of slenderized fiber and elasticity.For the sake of the convenience of treatment and use in the future, the morphology, structure and properties of slenderized coarse yak hair fiber were studied. The results showed that the scale structure has been deteriorated in the surface of coarse yak hair fiber stretched, and the density of that decreased gradually with the stretching ratio increase. Some scales turned up at the edge of cell, even the partial of scales come forth situation slippage and damage. After stretching slenderization, the diameter of fibers decrease evidently, especially that of the fiber stretched at 90% ratio could reduce approximate 30% than the original fiber. Moreover, the shape of cross-section of fibers change from near circular form to oval. The cortical cells have been elongated and slenderized, and the orientation along the fiber axis became more obvious, and the density of packing of those gets increase. The breaking strength and initial module of slenderized fibers are both higher than the original fiber, and with the increase of stretching ratio the value of those raise gradually. However, the variation of the extension at break was different. Furthermore, the bending rigidity of fibers is lower than its original fiber after stretching. Slenderized fibers have a higher friction coefficient than the original coarse yak hair fiber have, and the variation quantity of that reduce gradually with stretching ratio increase. The hydroscopic property of the fibers has been improved obviously, so that the slenderized fiber’s dyeability is made better greatly and it become possible for dyeing at lower temperature.更多还原