【作者】 罗锦；

【导师】 王府梅；

【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】 PTT (Polytrimethylene terephthalate)是一种新型可成纤高聚物,二十世纪末期先后由Shell化学公司和DuPont公司实现了其工业化生产。PTT/PET (Polyethylene terephthalate)并列复合纤维是利用PTT和PET两者的收缩率差,经过熔融复合纺丝得到的具有自发卷曲的复合纤维。这种类似卷弹簧结构的螺旋状卷曲给纤维带来了高延伸性能,又加上其中的PTT组分的“Z”字形大分子结构使其具备了低模量、高伸长、高回弹性等优异性能,使PTT/PET纤维可用于梭织和针织结构弹性织物的制造,并且具有比氨纶或锦包氨纱线更好的弹性持久性、耐氯漂性、尺寸稳定性、耐晒、耐高温、柔软舒适等性能。所以,该类纤维受到了产业界的高度重视,已经商业化生产的国际著名产品有Ivista公司的T400、Huvis的ESS等,Hyosung的X55,这些国外企业都有PTT/PET纤维的发明专利,国内企业像海宁新高也生产有PTT/PET纤维CM800,但是目前,国内纤维企业生产该类聚酯纤维还存在着设计盲从、纤维性能不清楚等问题。本文的目的是从研究复合纤维的卷曲结构特征出发,深入了解纤维的结构弹性,结合理论分析卷曲结构的成因、影响因素及弹性力学性能,得到设计PTT和PET新型双组份纤维时重要的参数,探明其弹性力学性能的预测方法,为国内外开发新型的PTT/PET自卷曲纤维提供理论依据和实验参考。全论文主要的工作及结论如下：关于PTT/PET纤维卷曲结构的研究,选取了4种已商业化生产的PTT/PET纤维试样,通过红外光谱分析及染色实验验证复合纤维的两种组分,并结合光学显微镜观察得到的复合纤维的横截面形状,综合得到各复合纤维中两组分的比值。实验观察得到PTT/PET纤维试样的横截面形状有“葫芦形”、圆形和“哑铃形”,对应的PTT和PET的两组分比分别为40/60、60/40和50/50,不同的横截面形状和组分比最终使复合纤维形成不同的卷曲结构。PTT/PET复合纤维在不同环境条件下,卷曲形态有很大不同,初步纺丝成型的纤维拥有松散、不明显的螺旋卷曲形态,但是,经过热处理的纤维的螺旋卷曲排列紧密。根据对PTT/PET纤维的卷曲特征观察,选用螺距、卷曲半径、卷曲曲率和卷曲轴向均匀度4个指标表征纤维的螺旋卷曲形态。测试纤维试样的这些指标,结果发现,随着PTT/PET纤维的线密度增加,纤维卷曲的螺距、卷曲半径增加,而卷曲曲率降低；横截面形状对获取较高的卷曲曲率有至关重要的影响,横截面的长短轴比值大的复合纤维有利于获得较高的卷曲曲率；纤维试样的螺旋卷曲规整度不高,“葫芦形”横截面纤维拥有最高比例的规整三维螺旋卷曲。PTT/PET复合纤维的重要特性是其所能提供的弹性。与普通纤维的强伸性测试时需要消除纤维的卷曲不同,PTT/PET纤维的弹性来自于纤维的卷曲结构,在测试时不应该有意消除卷曲,所以,需要确定该类纤维测试时的预加张力。通过实验确定出适合PTT/PET纤维拉伸性能测试的预加张力为0.001±0.0001cN·dtex-1。纤维拉伸实验测试结果表明,PTT/PET纤维的伸长包括卷曲伸直和纤维自身伸直两部分,卷曲伸直具有低模量高伸长的特征；热处理对纤维的伸长能力有重要影响,热处理后的纤维的断裂伸长率可增高至450%-600%,卷曲伸长率则可高达300%-450%,而且纤维的弹性模量明显降低。通过定伸长6次循环拉伸实验表明,PTT/PET自身的弹性回复率低于纯PTT纤维而明显高于纯PET纤维；热处理后的纤维弹性显著提高,在定伸长为150%时弹性回复率可达80%以上,螺旋卷曲结构提供了高弹性回复率。从双组分复合纤维的卷曲形成机理可分析PTT/PET纤维不同卷曲结构的成因,探明各因素对纤维卷曲的影响是控制PTT/PET纤维卷曲结构的关键。建立了3种不同横截面形状的实际PTT/PET纤维的截面惯性矩的计算模型,运用Denton建立的双组分纤维卷曲曲率的模型和测量的横截面结构参数,得到3种实际的PTT/PET纤维的卷曲曲率计算方程。为分析卷曲结构表征指标之间的关系,建立了横截面直径、卷曲曲率、卷曲半径和螺距的关系模型。用该模型分析PTT/PET纤维试样的卷曲结构参数发现,纤维的卷曲曲率处于可达到的卷曲曲率较小的范围内,而且卷曲半径趋于最大、而螺距趋于最小。因此,分析复合纤维的卷曲结构存在最小螺距值,也即是复合纤维束丝的直径,由单根纤维横截面面积及纱线充满系数,得到复合纤维束丝直径,也即是最小螺距值,实际测得纤维螺距值与最小螺距值的比值在1.39～2之间。PTT/PET纤维的卷曲结构是弹性来源的主体,其力学伸长特征关乎到纤维的使用性能,根据复合纤维组分的几何分布及卷曲结构参数可建立纤维的负荷—伸长模型,用于预测纤维卷曲结构的力学伸长性能。用两种方法建立了PTT/PET纤维卷曲结构的力学伸长模型,计算模型Ⅰ,基于复合纤维卷曲结构是螺旋曲线而建立的Holdaway模型,将该模型用于表示PTT/PET卷曲结构的负荷—卷曲伸直度关系,可以反映出纤维卷曲结构伸长的整体特征,但与实测值之间的差距明显,能用于预测纤维卷曲结构的伸直负荷；力学模型Ⅱ,由卷曲纱线伸长的力学原理出发,建立PTT/PET纤维卷曲结构伸长的模型,并通过修正复合纤维的弹性模量,可得到准确表达卷曲结构伸长的力学特征。PTT/PET纤维的卷曲曲率计算方程中含有两个未知的重要参数—PTT和PET的弹性模量比和收缩率差,本文用3种实际纤维求取这两个参数为研制新型双组分纤维的提供了重要依据。通过测试分析发现3种PTT/PET纤维试样中的PET组分的结晶度相近,PTT组分的结晶度也相近,从而认为纤维试样中相同组分的弹性模量近似或相等；通过复合纤维的应力—应变曲线和两组分的横截面面积求得PTT和PET的平均弹性模量比为0.573。两组分的收缩率差是双组分复合纤维形成卷曲结构的最根本原因,在弹性模量比已知的情况下,又有测量卷曲半径和螺距计算得到的纤维卷曲曲率,通过解方程得到PTT和PET两组分的收缩率差在6.70%-8.57%之间。弹性模量比和收缩率差对复合纤维卷曲曲率的影响显著,当弹性模量比在0-0.5范围内增加时,PTT/PET纤维的卷曲曲率增加迅速,而当弹性模量比超过0.5后,卷曲曲率增幅急剧降低,还有减小的趋势；横截面形状和组分分布一定的情况下,收缩率差越大,PTT/PET纤维的卷曲曲率越高。通过求取这两个材料参数发现,PTT和PET的高聚物是制造自卷曲纤维的绝佳配伍。关于PTT/PET纤维的新织物开发,本课题首先解决了PTT/PET纤维用于针织物时出现的布面随机性“条阴状不匀"问题,解除了针织产品开发时遇到的困扰。通过常用的调整布面不匀的方法不能改善这种不匀,根据对PTT/PET纤维卷曲结构的观察分析,发现热处理后的PTT/PET纤维卷曲结构存在随机性的“反转点",螺旋卷曲的方向在该点两侧发生变化,因此引起相邻两路纱线之间不一致的凸起或下陷,形成织物表面的不匀。找到形成织物不匀的原因之后,由PTT/PET纤维的卷曲特征,研发出一套切实可行的纤维后加工方法,经过该方法加工的新型纤维,能获得表面均匀、光滑的针织物。PTT/PET纤维能赋予织物优异的弹性才是其最终的应用价值所在,PTT/PET纤维的机织物弹性伸长率一般在10%-30%,是普弹织物的优良面料首选,可用作手感柔软及弹性自如的套装、修身衬衣等。设计织造3×11种织物试样,从织物组织类型、纬丝密度、PTT/PET纤维含量、捻度及纬丝卷曲结构等方面分析结构因素对织物弹性的影响,得到如下发现：斜纹和缎纹组织有利于织物获得高弹性性能；织物弹性随着PTT/PET纤维在纬丝中含量的增加而增加,但当纤维含量达到66.7%以后,织物弹性就保持在恒定水平；纬丝卷曲蓬松对织物弹性有利,而纬丝密度增加使织物弹性有减少的趋势,纬丝加捻后使织物弹性明显下降。织物中拆出的PTT/PET纤维保留了纱线在织物中的卷曲形态,不仅有经纬纱交织的屈曲状态,还有长丝热收缩的螺旋卷曲；复合纤维在织物的收缩卷曲受到交织阻力的影响,使得长丝处于浮长处的蓬松度高,而在交织点处的纱线的蓬松性稍差。弹性影响因素分析说明发挥PTT/PET纤维弹性的关键是使纤维在织物中有足够的空间和机会进行卷曲收缩。更多还原

【Abstract】 As a new and fiber forming polymer, PTT (Polytrimethylene terephthalate) was successfully industrialized by Shell Chemical Corp. and DuPont Corp. separately. PTT/PET fiber is produced via the conjugated spinning method to make the bicomponent fiber, which has self crimps because the different shrinkage of PTT and PET components. The fiber develops high frequency spatial helical crimp geometries similar to the appearance of a telephone wire. In addition, the PTT component has the "Z" macromolecule chain which gives the fiber low modulus and high elastic recovery. These crimps offer exceptional good stretch and wrinkle recoveries, and bulk to the yarns and fabrics. Although polyurethane based fibers (spandex) can provide comparable elasticity to fabrics, PTT/PET fibers are easier to dye, higher dimensional stability and more resistant to chlorine bleaching, sunshine and high temperature. PTT/PET fiber is very popular in textile industrial circle, and the commercial international brands have Invista’s T400, Huvis’s ESS and Hyosung’s X55. All of the patents of producing the bicomponent fiber were owned by the overseas factories. Although the domestic factories have the similar fiber production, they didn’t have their own technological property right to produce this fiber.In this research, we aimed to investigate the configuration and properties of the self-crimpsing of this fiber. We also make analysis on the crimps’ mechanical formation of PTT/PET fiber, and the factors affecting on the crimp configuration. Some obtained important parameters which are useful for designing new PTT and PET bicompoent fiber. The method of predicting the stress-strain properties of crimps was also verified. The results gave some experimental suggestions and theory basis to produce the new fibers. The main work and results of this thesis will be presented in the following.Four commercial PTT/PET fibers were selected to investigate the crimp configurations. The two components of fibers were verified by FTIR (Fourier Transform Infrared Spectroscopy) and fiber dyeing experiment. The optical microscope investigation results present that the shapes of the sample PTT/PET fibers have gourd-shaped, round and dumbbell-shaped, the component ratio is 40/60,60/40 and 50/50 accordingly. PTT/PET fibers have different crimps when the environment is changed, the preliminary spun PTT/PET fiber have loose and inconspicuous helical crimps configuration. When the fiber was treated in heat treatment, the crimps became much more compacter. Based on the investigation of crimps configuration, four parameters were selected to indicate the crimp configuration, they are crimp radius, helixes pitch, crimp curvature and axial uniformity. The results of measuring the parameters show that with the increasing of helixes pitch and crimp radius, the crimp curvature will decrease. The cross-sectional shape is the vital factor to acquire higher crimp curvature, the fiber cross section with larger ratio of long and short axis has the advantage to obtain higher crimp curvature. PTT/PET fiber samples don’t have higher axial uniformity, and the fiber with gourd-shaped cross-sectional shape has the highest axial uniformity.As a new elastic fiber result from crimp structure, it is necessary to set a standard method to measure the stretch and resilience of PTT/PET fiber. To apply a suitable pretention is the first important parameter needed to confirm. After several exploring experiments, the pretention was confirmed as 0.001±0.0001cN/dtex for measuring the tensile properties of-PTT/PET fiber. The experiment results show the elongation of PTT/PET fibers have two parts including the elongation of crimps and fiber oneself. Especially, the crimp elongation of PTT/PET fiber has the low modulus and higher elongation. The heat treatment has obvious influence on the fiber elongation, the elongation ability of treated fiber could reach as high as 450%～600% and the crimp elongation is 300%-450%. The 6 times stretch experiments results show the elastic recovery of PTT/PET fiber self is between the pure PTT and PET fiber, and the elastic recovery of treated fiber is above 80% when the elongation at 150%. The excellent elasticity of treated fiber comes from the crimp configuration.The crimp mechanism of PTT/PET fiber is same as that of common side-by-side bicomponent fibers. In order to investigate the effects of different factors on crimp structures, some models were built to calculate the second moment of PTT/PET fibers with complex cross-sectional shapes. Based on the Denton’s crimp curvature model of bicomponent fiber and measured cross-sectional parameters of PTT/PET fiber, the crimp curvature calculation model of PTT/PET fiber was built.Another model was built in order to analyze the relationship among the parameters of crimp configuration. When the model was used to analyze the crimp configurations of PTT/PET fiber sample, the analytical result shows that the crimp curvature of fiber in the lower possible value, and the crimp radius tend to maximum but the helical pith tend to minimum. The result also indicates that the crimp configuration of PTT/PET have the minimum helical pith which is the diameter of the filament yarn. The minimum helical pith could be got by the cross-sectional area of single fiber and the yarn block coefficient. The ratio between the measured and minimum helical pith is in the range of 1.39～2.The elasticity of PTT/PET fiber is come from the crimp configuration whose stretch property is associated closely with the usability of fiber. The stress-elongation model of crimps could be built by parameters of crimp configuration and geometric distribution of two components. Model I is Holdaway model based on the crimps configuration is helical curve. Applied model I to express the stress-crimp extension of PTT/PET fiber, the results present the classical characterization of crimp configuration elongation, but there is a gap between the measured and model value. The model II which followed the mechanical principle of yarn, the exact stress-crimp extension curve could be obtained by this model with corrected elastic modulus.There are two important unknown factors in the built crimp curvature calculation equation, the elastic modulus ratio and differential shrinkage of PTT and PET components. We found that both of the crystallinity of PTT and PET component are almost the same in the three fiber samples, so the elastic modulus of the same components could be regarded as same in different fiber samples. The average elastic modulus ratio of PTT and PET components is 0.573 which is calculated by the stress-strain curve and cross-sectional area of two components. As soon as the elastic modulus ratio and the crimp curvature calculated by measured crimp radius and helical pitch were known, the differential shrinkage of PTT and PET components could be got in the range of 6.70%～8.57% by solving the equations. It was found that as the elastic modulus ratio increased, the crimp curvature increases rapidly when the m increases from 0 to 0.5, and then approach to a stable value when m is larger than 0.5. The crimp curvature increased continuously as the differential shrinkage increased. After the experimental and theory analysis, the PTT and PET polymer are the best choice to make the bicomponent fiber.When PTT/PET fiber used in knitted fabrics it has a tendency of showing severe random uneven surfaces. The causes of this problem and ways to overcome it were investigated. Fabric surfaces and yarn crimp configurations of several knitted fabrics made with PTT/PET bicomponent filaments were studied by optical microscopy. Attempts to adjust the tensions and yarn speeds during knitting could not eliminate the unevenness entirely, especially when the fabrics were wet-heat treated. From microscopy and heat-treatment studies, the major cause for this unevenness was found to be due to the development of tight crimp configurations, which produced reversal points and changed the helical crimp directions after heat-treatment. They caused light to reflect differently, and the random tight crimps caused fabric to protrude and, therefore, the unevenness. This problem was mitigated by using PTT/PET filaments made by a new yarn manufacturing method, which controlled the development of crimp configurations and prevented the formation of reversal points and helical crimp direction changes.The most important thing for PTT/PET fiber is that it could give the fabric excellent elastic. PTT/PET fiber is usually used as in the fabric with medium elasticity, such as the free elastic suit, fitness skirt, etc. The influences of important structural variables on the elasticity of woven fabrics made of PTT/PET weft filaments by testing 3×11 samples with different weave structures, PTT/PET contents, weft densities and yarn twists. Fabric elasticity is described by two indices, fabric strain and resilience in tensile testing. The experiments results indicate that twill and stain weaves have greater potentials in obtaining high elasticity than a plain weave. Fabric elasticity increases with the increase of the PTT/PET content in the weft yarn, but the change becomes insignificant after the PTT/PET content exceeds 66.7%. Increase in weft density has a negative effect on fabric elasticity, while the weft twist limits crimp formation of PTT/PET filaments and thus undermines the fabrics elasticity noticeably. The built-in helical crimps in the PTT/PET filament result in good yarn elongation and recovery, and therefore can influence the elasticity of fabric. The PTT/PET fiber could not shrink more than the space between adjacent warp filaments during the heat-setting process. Hence, lowering warp density and having adequate finishing temperature and time can help the fabric to gain more elastic potential.更多还原