【作者】 严佳萍；

【导师】 陈新；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2009， 硕士

【摘要】 动物丝,特别是蜘蛛丝近年来由于其优异的综合力学性能而倍受关注。但是天然动物丝的应用由于种种原因而受到各种限制,因此人们期望通过人工纺丝来获得性能与天然动物丝相近的再生丝蛋白纤维。本论文在本课题组已有的人工纺丝的基础上(即采用高浓度的再生丝蛋白水溶液作为纺丝原液,以硫酸铵水溶液为凝固浴,通过湿法纺丝的方法制备出性能较好的再生丝蛋白纤维,进一步研究了纺丝工艺参数,如卷绕速度、拉伸倍率及不同阶段拉伸倍率的分配等对最终获得的再生丝蛋白纤维结构和性能的影响,并成功地采用连续机械化过程纺制得到六倍后拉伸再生丝蛋白纤维,其断裂强度为0.39 GPa。断裂伸长为32.1%,断裂能为80.8 kJ/kg,其综合力学性能已经可以和天然蚕茧丝相媲美。在工艺方面,本论文首先讨论了不同的起始卷绕速度对再生丝蛋白纤维的影响。研究发现,即使在可纺的浓度范围之内,不同的再生丝蛋白纺丝液浓度所对应的适宜的起始卷绕速度也不同,较低的纺丝液浓度对应的初始卷绕速度较低。对于相同的拉伸倍数,采用相对较慢的起始卷绕速度获得的再生纤维的力学性能较差,其原因可能在于较慢的拉伸速度不利于破坏丝蛋白分子链的缠结,从而影响到分子链沿纤维轴方向的取向排列。其次,本论文讨论了第二辊与第三辊上拉伸倍率的分配对再生丝蛋白纤维的影响。结果表明,以50 rpm→150 rpm→300rpm方式获得的六倍拉伸纤维的力学性能要明显高于以50 rpm→200 rpm→300rpm方式获得的六倍拉伸纤维。因此我们得出再生丝蛋白纤维纺丝过程中一个重要的参数,即在整个纺制过程中,第二辊相对于第一辊拉伸倍率不能大于3,要获得高拉伸倍率的纤维,必须通过增长纺程,通过逐步增加拉伸倍率来得到最终的纤维。热力学性能分析结果表明,随温度增加,丝蛋白纤维(包括天然蚕茧丝和再生丝蛋白纤维)在140-160℃之间分子链之间的结合水被破坏,此过程为不可逆转变;在160-180℃之间分子链发生运动,出现一相转变过程,此过程为可逆转变;在210-225℃之间规整区域发生了转变,导致力学性能下降;在280-310℃之间丝蛋白分子链开始降解,最终的残留量为40-50%。从热力学的分析结果可以看出天然蚕丝结构仍然较再生丝蛋白纤维来得完善,表现在其降解峰出现在较高温度,且要使其发生分解需要较大的能量。同时热力学分析结果也表明随着拉伸倍数的增加,再生纤维的结构会趋于完善。本论文还首次采用同步辐射红外光谱对动物丝单丝进行了表征,结果表明通过凝固浴和初步拉伸两个过程之后,再生丝蛋白纤维中β-折叠的含量与天然蚕茧丝已相差无几,并且不同拉伸倍数所获得的再生丝蛋白纤维的β-折叠含量几乎相同,这表明后拉伸过程对于提高再生丝蛋白纤维力学性能主要起到破坏分子链的缠结,改善分子链沿纤维轴的取向上,而对于增加丝纤维中的规整结构,即β-折叠含量的作用很小。更多还原

【Abstract】 Natural silk, especially spider dragline silk, has been noted for its excellent comprehensive mechanical properties in recent years, though it is limited to apply them in life for kinds of reasons. So researchers are committed to prepare regenerated silk whose properties could be comparable with natural ones by artificial spinning. Regenerated silk fibroin (RSF) fibers were obtained by extruding of concentrated silk fibroin aqueous solution into ammonium sulphate coagulation bath. A custom-made simplified industrial wet-spinning device with continuous mechanical post-drawn was used in our trial spinning. It is interesting to note that the draw down ratio of 6 producing the best molecular orientation and tensile properties in the present work after modulation of rolling rate, draw ratio and step distribution. Its break strength is 0.39 GPa, break elongation is 32.1% and break energy is 80.8 kJ/kg.As to wet-spinning, firstly, in the range of spinning dope concentration, low concentration requires slow rolling rate, resulted in bad mechanical properties even underwent the same draw down ratio. It is possible that slow rolling rate is not useful to destroy the entanglement of molecular chain. Secondly, to the draw down ratio of 6, the mechanical properties of RSF fibers produced by 50 rpm→150 rpm→300 rpm surpass those of 50 rpm→200 rpm→300 rpm. So in the whole spinning line, the optimal draw down ratio of second roller is no more than 3, then adding spinning step to obtain high drawn-down RSF fibers.For RSF fibers with different drawn ratio and degummed silk, the molecular chain underwent a transformation with temperature increasing. As to range of 140 to 160℃, bound water between molecular chains is destroyed. It is an irreversible process. Change between 160 and 180℃is attributed to the movement of molecular chain in RSF fibers, corresponding to a phase transition. While DMA peak between 210 and 225℃is owe to transition in regular region. The degradation of molecular chain take place in the range of 280-310℃. At last, the residual fiber weight percent is 40-50%. In conclusion, degummed silk possess a more orientedβ-sheet conformation than RSF fibers. And with increase the draw down ratio, molecular alignment in RSF fibers is improved.In this dissertation, synchrotron FTIR is used to characterize single fiber firstly. As a result, after coagulation and post-draw in spinning line, the content ofβ-sheet in RSF fibers is close regardless of different draw down ratio, approaching that of natural silk. It is possible that post-draw could destroy the entanglement of molecular chain to improve the alignment in fibers, while could not increase the content of regular conformation.更多还原