【作者】 张丽；

【导师】 王善元；

【作者基本信息】 东华大学 ， 纤维材料物理， 2008， 博士

【摘要】 纤维素纤维是一类重要的纺织原料而且资源丰富,人们在重视纤维素纤维使用性能的同时,对纤维素纤维的利用、处理和研究进行了重新认识和发掘。而微波加热处理技术是一种节能高效的热能技术,微波处理纺织材料正是微波技术与纺织领域相结合而开辟出来的新领域。尽管微波处理技术发展较早,但是关于微波对纤维作用的研究,大多数国家主要从事其应用方面的研究,而关于微波与纤维相互作用的微观机理方面的研究未见报道,因而目前仍然没有一套完备理论对微波与含水纤维素纤维的相互作用进行描述,对于微波处理后的纤维素纤维结构与性能的研究也未见系统的文献报道。本文选择棉和苎麻为天然纤维素纤维的代表,粘胶、天丝和醋酸纤维素纤维为再生纤维素纤维的代表,采用不同微波处理参数,对不同状态参数的五种纤维素纤维的外观形貌、微观结构及内部结构的影响进行系统性的研究,得出微波处理对纤维素纤维结构与性能的影响规律,并将微波干燥应用于纤维素纤维产业的毛巾干燥行业。首次建立了纤维素纤维微波干燥的动力学模型,系统的描述了微波作用下的纤维素纤维的失水程度和过程。同时首次采用核磁共振技术,对于微波处理前后的棉纤维进行晶粒内部结构表征的研究和对比,得出微波处理后棉纤维结晶结构的变化趋势。并将微波处理技术应用于企业生产中的毛巾烘干处理工序中。主要研究内容和结论如下:研究了纤维素纤维的介电特性,对纤维素纤维中水分的状态:游离水和束缚水的介电特性进行了分析和阐述,并对纤维素纤维的微波损耗进行了分析,建立了纤维素纤维的细度(N_tex)与纤维单位长度的微波损耗（P_l）之间的关系式。研究了微波处理后五种纤维素纤维的失水规律。醋酸纤维素纤维的干燥曲线和其它四种纤维差别较大。开始醋酸纤维素纤维干燥速率最大,随着水分的损失,粘胶和天丝的干燥速率逐渐成为最大,其次是棉纤维和苎麻;对于不同初始回潮率的同种纤维来说,干燥曲线的形状基本相同,即干燥规律相似,而且随着纤维初始回潮率的增加,微波干燥时间逐渐增加;随着润胀程度的增大,对于水分的去除也就越困难;随着功率以及纤维含杂率的增大,棉纤维的干燥速率大大增强。研究了微波干燥动力学模型,纤维素纤维的干燥模型可以用Page方程MR=exp（-ktⁿ）来表示。经回归拟合得出的方程可以用于描述棉纤维微波干燥过程中水分的变化情况。研究了不同回潮率的纤维进行微波处理后强伸性能的变化。除了醋酸纤维素纤维,其余四种纤维在初始回潮率为0的时候,经过微波处理,纤维强度都是显著性下降的:随着初始回潮率的增大,棉纤维、粘胶、天丝的断裂伸长率有了显著性的提高,其中升高的幅度为粘胶＞天丝＞棉纤维,苎麻没有显著性提高;在回潮率较小的范围内,微波处理之后纤维的初始模量是增大的,随着回潮率的增大,初始模量变化不显著。研究了微波功率与时间对纤维强伸性能的影响。对于棉,粘胶和天丝来说,在微波处理时间一定的情况下,随着微波功率的增大,纤维强度和断裂伸长率先增大,后减小。在微波处理功率一定的条件下,随着微波处理时间的延长,棉纤维、粘胶和天丝的纤维强度先上升,后下降,而苎麻只出现强度下降的数据点;随着微波时间的延长,棉和粘胶的断裂伸长率先上升,后下降,苎麻只有显著下降的数据点,而天丝只有显著上升的数据点;初始模量均先上升,后下降,但是下降后的数值也比原样的数值高。通过SEM图观察可知,微波处理后的纤维横截面和表面形貌变得粗糙但是变化微小,苎麻和天丝表面出现细小的裂缝和断纹,棉和粘胶的表面变化比较小,醋酸纤维素纤维表面几乎没有变化。通过X衍射分析可知,实验所提供的微波处理不会引起纤维素纤维内部晶体基本结构的变化,但是微波作用之后的棉,粘胶和天丝的结晶度以及晶粒尺寸均有下降,而且微波对于再生纤维素纤维的晶区作用比天然纤维素纤维作用强烈。通过红外光谱分析可知,经过微波处理后棉纤维的化学组成没有改变,在3100～3600cm^-1。区间内两条谱线的峰形不同,说明微波处理后纤维的分子间氢键、分子内氢键发生了变化。微波处理之后的吸湿指数增大。通过核磁共振碳谱表征分析可知,微波处理之后的结晶度要小于原样,但是由于微波处理之后的棉纤维有相当高的侧向有序指数,其在C2,3,5共振区域有更好的清晰度。X衍射和核磁共振均表明棉纤维是以纤维素I_β为主,微波处理改变了纤维素的晶型,晶型含量I_α和I_β均降低,但是比例基本保持不变,微波处理之后向次晶转化。以干燥毛巾为例,研究了微波在纤维素纤维产业中的应用,并与传统的干燥方式进行了对比。将初始回潮率为300%的纯棉一等品毛巾分别采用微波和烘箱两种方式进行干燥,结果表明,采用微波干燥比传统烘箱干燥的耗时短,速度快,干燥后的毛巾强度和吸水性能改善。两种干燥方式对毛巾脱毛率和色牢度影响等同。纤维素纤维的结构与性能是纤维素学科的基础性研究课题。本研究在微波一纤维素纤维作用理论的指导下,将微波应用于纤维素纤维产业上,以期为微波在纤维素纤维产业上的应用提供理论依据。更多还原

【Abstract】 Cellulose fiber is a kind of abundantly important textile raw materials.People not only pay much attention to cellulose fiber performance,but also take interested in gaining new insight into its processing and utilization.Microwave heating treatment （MHT） is a heating technology with advantages of energy saving and high efficiency. Based on a combination of microwave technology with textile industry,textile materials treated by MHT open up new areas.Despite the early development of MHT,studies on MHT acting on fibers are mainly focused on the application fields and little on the aspects of the micro mechanism of MHT to fibers.Neither complete set of theories to describe the interaction between microwave and wet cellulose fiber nor studies on the structure and properties of cotton fiber after MHT has been reported yet.Cotton and ramie are selected as the representative of the natural cellulose fibers while rayon,loycell and cellulose acetate fibers as the representative of the regenerated cellulose fibers.Under different MHT and fiber parameters,the changes of morphology,micro structure and crystalline structure of five-kind cellulose fibers are studied systematically.The law of influence of structure and properties of cellulose fiber after MHT is set a theoretical basis for the application of MHT towel drying of cellulose industries.MHT Dry dynamics model of cellulose fibers are firstly established in this paper,which describes systematically the degree of water lose and the cellulose fibers after MHT.Characterizations and comparisons of crystalline structure of cotton fibers before and after MHT were investigated using ¹³C-CP/MAS NMR spectroscopy technology as well as trends was studied.Besides,MHT technology was applied to towel drying process in industry production.Contents and conclusions of the studies are mainly as follows.The dielectric properties of cellulose fibers were studied and the water existent form in fibers including free water and bound water were analyzed and described. Microwave loss of cellulose fibers were analyzed and the mathematical relationship between fiber fineness(N_tex) and microwave loss of unit length of cellulose fibers（P_l） were also discussed.The water loss laws of the five-kind cellulous fibers were studied.The differences between cellulose acetate fiber and the other four-kind fibers are significant.Initially, cellulose acetate fiber shows the highest drying rate.However,with the loss of water, the drying rate of rayon and loycell becomes the biggest,followed by cotton and ramie fibers.As far as the same kind of fibers with different initial moisture regains are concerned,the drying curves are basically the same,that is to say,they share the similar drying laws.Furthermore,with increasing initial moisture regain,the time of MHT drying is increased;with increasing degree of water swelling in fibers, water removal became difficult;with increasing MHT power and impurity contents in fibers,drying rate of cotton is dramatically increased.Microwave dry dynamics model was studied,and the dynamics model of cellulose fibers was expressed by PAGE equation MR=exp（-ktⁿ）.The equation after regression fitting can describe moisture changes in microwave drying process of cotton.The changes of fiber tensile properties after MHT with different moisture regains were studied.Except cellulose acetate fiber,the strength of other four-kind fibers in completely dry state is decreased notably after MHT.With the initial moisture regain increased,the breaking elongations of cotton,rayon and loycell are improved remarkably after MHT.The increasing level is rayon＞loycell＞cotton,but ramie seems little improved.As the moisture regain is low,the fiber initial modulus is enhanced.However,when the moisture regain is higher,the fiber initial modulus did not change obviously.The influences of microwave power and time on fiber tensile properties were studied.For cotton,rayon and loycell fibers,with microwave power increases while MHT time keeps constant,fiber strength and breaking elongation initially increase and then decrease.Likewise,with MHT time increases while MHT power keeps constant,fiber strength of cotton,rayon and loycell increase and then decrease.Ramie, however,shows only decreased strength.With MHT time increases while MHT power keeps constant,breaking elongation of loyeell remains increasing but cotton,rayon increase and then decrease,still ramie only decreases.At the same time,all the initial modulus increased at first and subsequently decreased,but the resultant initial modulus are still higher compared with the fibers without MHT.Through SEM observation,we observed that axial morphology and cross section of fibers after MHT become slightly rough,but tiny cracks appear on the surface of ramie and loycell.For cotton and rayon,changes are very tiny,and cellulose acetate fibers have few changes.Through X-ray diffraction,we found that the basic crystalline structure of cellulose fibers can not be changed by MHT in the experiment.But after MHT,both the crystallinity and crystalline size of cotton,rayon and loycell are decreased. Meanwhile,the influence of MHT on regenerated cellulose fibers is stronger than natural cellulose fibers.Based on IR analysis,the chemical composition of cotton after MHT is not changed. At the wave number range of 3100～3600cm^-1,the two spectrums are different, which exhibits that the function of hydrogen bond between intermolecular and intramolecular is changed after MHT.Moisture index of fibers after MHT improve.Characterization of cotton fiber using solid-state ¹³C-CP/MAS NMR spectroscopy shows that the crystallinity after MHT is lower than the original sample,but the cotton after MHT has a higher lateral orientation index,which has a good definition in C2,3,5 resonance region.¹³C-CP/MAS NMR spectroscopy and X-ray diffraction reveal that cellulose I_βis the main cellulose in cotton,and microwave change the allomorphs content.In addition,the allomorphs content I_αand I_βdecreased,but the ratio keep stable.The paracrystalline of cotton fibers increased after MHT.Using towel drying as an example to study the microwave application in cellulose industries and compare to traditional way of drying（TD）,a comparison has been drawn between microwave drying（MD） and TD with first-class cotton towels with 300%initial moisture regain,and the results show that MD save much more time and dry faster than TD.The strength and moisture absorption properties of towel after MD improved.The two way of towel drying show the same effect on unhairing rate and color fastness of towel.Structure and properties of cellulose fibers is a basic research subject.Under the guidance of the microwave-cellulose interaction theory,we applied microwave to cellulose fiber industries with a view to provide a theoretical basis for the application of microwave radiation treatment in cellulose industries.更多还原