【作者】 杨庆；

【导师】 梁伯润；

【作者基本信息】 东华大学 ， 材料学， 2005， 博士

【摘要】 壳聚糖由于其优异的生物性能,在生物医用材料领域倍受人们的关注。与此同时,对其物理与化学结构的研究也得到了极大的发展。壳聚糖纤维可以用于制备医用敷料、人体可吸收缝合线、组织工程载体材料等,但目前壳聚糖纤维的强度较低,严重制约了其应用的领域。因此,对壳聚糖纤维进行改性以改善其机械性能已成为近年来这一领域的重要研究方向。本论文的主要目的是采用干湿法纺丝新工艺制备壳聚糖纤维,并通过交联反应以提高壳聚糖纤维的机械性能。为此,我们研究了壳聚糖原液的流变性能;探讨了纺丝工艺对纤维强度的影响;采用乙二醛对壳聚糖纤维进行了交联反应,并探讨了反应机理;系统研究了交联工艺对纤维强度的影响,并对交联纤维的化学结构、晶体结构和耐热性能等进行了表征。通过研究,取得了如下主要结果: 1、研究了壳聚糖/乙酸原液在不同剪切速率(?)和温度下的流变性能。结果表明,原液表观粘度ηa随壳聚糖含量增加而上升,在3%左右到达原液的临界浓度C~*,过了C~*点,大分子链之间缠结显著增加,ηa急速上升。作为纺丝原液的饱和浓度约在3.8%左右。高浓度原液在低温、低(?)区呈现一个类似于宾汉流体的屈服应力τy,低于τy值时,(?)≈0。原液在低(?)区间为牛顿流体,n约为1;随着(?)的加大,表观粘度下降,原液呈切力变稀的假塑性流体特征,n<1。温度在较大剪切速率范围内影响着原液的粘度。原液的粘流活化能△Eη随浓度和(?)的增大而降低。原液的结构化程度随原液体系温度上升、浓度下降而减小,因此适当的加温有利于干湿法纺丝的顺利进行。 2、系统地研究了干湿法纺丝工艺条件对纤维强度的影响。结果表明,纺丝流程中从喷丝孔至凝固浴之间的空气层对初生纤维结构的形成及其机械性能起着很重要的作用;若原液细流在空气层中受到轴向拉伸(喷头拉伸比大于1)并使其在喷丝孔内因剪切应力所形成的大分子链取向度得到加强,则纤维强度提高;若原液细流在空气层中为负拉高强度壳聚糖纤维的制备及结构性能研究伸(喷头拉伸比小于1),喷孔内形成的剪切取向会在空气层中松弛,从而使纤维强度降低。空气层的最佳长度随原液浓度的变化而变化。扫描电镜照片显示,干湿纺纤维截面比较细密,几乎看不到孔洞;而湿纺纤维的截面明显粗糙,孔洞很多。凝固浴的组成和温度是影响纤维强度的两个重要因素:较高的NaOH浓度或较高的温度使得纤维凝固过程激烈,纤维机械性能下降;过低的Na0H浓度或较低的温度致使纤维凝固过程过于缓慢,纤维结构形态恶化,机械性能下降或甚至难以固化成形。拉伸浴温度的升高使得大分子链的活动性能加强,内部溶剂容易排出,因此拉伸倍数以及纤维强度随温度提高而增加,但其影响在80℃以上趋于平缓。3、采用乙二醛作为交联剂对壳聚糖纤维进行交联反应。研究了反应条件对交联纤维力学性能的影响,并对反应机理作了探讨。当乙二醛含量达到一定浓度后,溶胀度趋于一个定值。FT一IR和’3c NMR的分析结果表明,乙二醛与壳聚糖葡萄糖胺环上的CZ氨基进行了SChiff交联碱反应,并与C6轻基进行了缩醛化交联反应;其中,Schiff碱反应占据了主导地位。交联过程中,交联剂浓度、溶液pH值、反应温度和时间在不同程度上影响交联效果以及纤维的机械性能。乙二醛的最佳浓度在4%左右,浓度过低则增强效果不明显,而过高的浓度导致交联纤维结晶性能恶化,机械性能下降。最佳反应的pH值约为4左右,弱酸性对Schiff碱反应起着催化作用,酸性的减弱(pH>5)将降低反应速度。反应温度对交联反应的影响程度并不大,40℃左右对纤维强度的增加较为有利。交联反应大约在30分钟左右到达平衡值。交联纤维的强度和初始模量分别比交联前显著增加了88%和28%,而断裂伸长则有所下降。4、采用广角X光衍射(WAXD)、差示扫描量热法(DSC)、电镜扫描(SEM)、热解重量分析(TGA)和偏光热台显微镜(PLM)等方法对壳聚糖交联纤维的结构进行了分析并与未交联纤维作了比较。wAXD的结果表明:未交联纤维的结晶度较高,主要为a晶型结构。经交联反应之后,纤维内部部分Q一晶体转化为p一晶体;结晶度从交联前的34.7%下东华大学博士论文2005年3月更多还原

【Abstract】 Chitosan has attracted great attention in the area of biological medical materials duo to its unique biological properties and, at the same time, the research on its physical and chemical structure has made tremendous progress. Chitosan fiber can be used to prepare medical dressing, human body absorbable suture, support material for tissue engineering etc., but its lower tenacity greatly hinders its application area. Therefore, the modification to improve the mechanical properties of chitosan fiber has been as an important research direction in this area in recent years. The purpose in this dissertation is to ameliorate the mechanical properties of chitosan fiber by using dry-jet wet spinning and cross-linking reaction. The rheological behavior of chitosan dope was studied and the effect of spinning technology on the fiber tenacity was discussed. Glyoxal was used as a cross-linking agent to deal with chitosan fiber and the cross-linking mechanism was approached. The effect of cross-linking technology on the fiber tenacity was systematically studied and the chemical structures, crystal structure as well as the heat endurance of the cross-linked fiber were characterized. Based on above research works, the main results obtained are as follows:1. The rheological behavior of chitosan /acetic acid at various shear rate γ and temperature was studied. The results showed that the apparent viscosity η a of chitosan dope is increased with increasing chitosan content and reaches its critical concentration C* at about 3%. Above the C*, the entanglement of macromolecular chains is significantly intensified and thus the n a is remarkably increased. The saturation concentration of spinning dope is about 3.8%. There is a yield stress τ_y, similar to Bingham fluid, appearing in the high concentration, low temperature and lower γ region of the flow curves. When shear stress τ is less than τ y, γ approaches to 0. The dope exhibits Newdonian fluid behavior with n about 1 at lower γ region. With the γ increasing, the dope exhibits a behavior of pseudoplastic fluid with shear thinning character (n<l) and theη a of the dope decreases. In a wide range of shear rates, the n a is dependent on the temperature. The activation energy for the viscous flow of the dope is decreased with the increasing of concentration and γ. The extent of the structured dope is decreased with elevating the temperature and reducing the concentration. Therefore, to suitably elevate the temperature of the dope is profitable for the dry-jet wet spinning.2. The effect of dry-jet wet spinning conditions on the fiber tenacity was systematically studied. The results showed that the air gap between spinneret and coagulating bath in the spinning line plays an important role in the formation of the as-spun fiber. If the dope thread was axially drawn (draw down ratio>l) and the orientation of chain segments created during nozzle channel by shear stress was strengthened in the air gap, as a result, the fiber tenacity was increased whereas if the dope thread was negatively drawn (draw down ratio<l), the shear orientation created during nozzle channel would be relaxed in the air gap and then the fiber tenacity was decreased. The optimal length of air gap is changed with the variation of the dope concentration. The SEM micrographs showed that the cross-section of dry-jet wet spun fiber presents a fine texture with little aperture while the cross-section of wet-spun fiber looks quite coarse with much pores existed. The constitution and temperature of coagulating bath are both important factors which affect the fiber tenacity. The higher NaOH concentration or bath temperature made the nascent fiber be fierily coagulated, leading to poor fiber mechanical properties. On the other side, the over lower NaOH concentration or bath temperature made the nascent fiber be coagulated too slowly so that fiber structure morpha was worsen, mechanical properties were falling down and even the fiber was hardly solidified. With elevating the temperature of drawing bath, the mobility of m更多还原