【作者】 刘维；

【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， 2011， 博士

【摘要】 目前,占纺织原料60%以上是化学纤维,并且主要是用石油制造的合成纤维。随着石油资源枯竭以及合成纤维生产、使用、废弃全过程对环境危害问题的日益突出,人类不得不重新审视天然纤维资源。受耕地、牧场等多种资源的限制,棉、毛、丝、麻四大类天然纤维的可增长量非常有限。为挖掘和利用“沉睡”的天然纤维资源,弥补纺织原材料的不足,同时为开发绿色纺织品添砖加瓦,本文在测试分析木棉纤维基本性能的基础上,有针对性地开发出适合木棉纤维的絮状材料制造技术,包括木棉絮料和木棉羽绒混纤絮料,并且推导出改进的纤维集合体传热模型。(1)木棉纤维的基本性能由木棉纤维的SEM照片,观测到其横向为薄壁大中空结构,胞壁厚度仅仅为1μm左右,纤维直径约为20μm,胞壁断面有微孔呈现。纤维纵向表面光滑无转曲,纤维根端封闭。纤维受外力作用下断裂面呈撕裂状,断口不齐。同为吉贝属木棉的印尼产木棉和泰国产木棉的形态结构无明显差异,和国产木棉属木棉的形态结构也基本—致。木棉纤维的长度范围和亚洲棉比较接近,为16-24 mm；线密度为0.6～0.9dtex,比棉纤维中线密度最低的海岛棉还要低；原产地为印尼和泰国的木棉纤维的直径范围为17-22μm。采用XQ-1单纤维强伸度仪测试了四种木棉纤维的拉伸性能,木棉纤维的拉伸曲线与棉纤维和麻纤维类似,没有明显的屈服点。不同原产地的木棉纤维拉伸性能存在差异,原产地相同拉伸性能也比较接近。木棉纤维的强力均值在1.44-1.71 cN之间,断裂伸长率的范围为1.8-4.2%,均有一定的离散性。木棉的断裂强度范围为2.03-2.70cN/dtex,初始模量范围为45～116 cN/dtex,与棉纤维相差不大,但是其绝对强力比棉纤维低。木棉纤维的断裂伸长率小于棉纤维。采用KES-FB2纯弯曲测试仪测试纤维片的方法可以有效地折算出单纤维的弯曲性能指标。木棉单纤维的弯曲刚度为0.823×10-5 cN·cm2,小于采用相同的测试方法测试的七孔中空涤纶纤维、四孔中空涤纶纤维和PTT纤维的弯曲刚度。这四种纤维的弯曲刚度与纤维线密度呈明显的线性关系,随纤维线密度的增加,弯曲刚度增大。木棉纤维折算到每tex的相对弯曲刚度为20.80×10-4cN·cm2·tex-2,明显大于棉纤维和其他所测试的三种纤维。(2)木棉絮料由于木棉纤维长度短、强度低,容易飞扬、漂浮等特性,传统纺织设备很难加工木棉纤维。本文开发出气流成网等一整套工艺技术,制作木棉絮状材料,可以使木棉纤维含量高达80%。成功试制四种木棉絮料。压缩性能测试结果表明,含有四孔三维卷曲中空涤纶、七孔三维卷曲中空涤纶和PTT纤维的三种絮料的压缩功弹性回复率好于喷胶棉,这三种纤维的使用可以有效地提高絮料的压缩回复性能。木棉含量80%的絮料的压缩功弹性回复率略低于喷胶棉,四种木棉絮料的压缩功弹性回复率相比手工铺絮木棉絮料要高很多,说明粘结纤维的使用可以有效地提高絮料的压缩功弹性回复率。分析经过压缩性能测试后木棉絮料的SEM截面照片,木棉纤维的中空状态得以保持,合理的机器加工方式对木棉纤维的损伤有限,有利于絮料的持久保暖。采用Pearson相关性分析分析了纤维线密度、中空度、卷曲数和卷曲回复率与絮料的体积密度、压缩率、线性度和弹性回复率之间的相关度。三维卷曲纤维的使用有利用提高絮料的蓬松度,压缩率也会增加,而线性度会降低。絮料的压缩弹性回复率与纤维中空度呈负相关,中空度越大絮料的压缩弹性回复率越小。木棉含量80%和含有中空纤维的絮料的面密度热阻大于含有PTT纤维的絮料,说明中空纤维的使用有利于减轻服装重量。四种木棉絮料的厚度热阻均大于喷胶棉。木棉含量80%的絮料的面密度热阻和厚度热阻均大于其他三种木棉絮料,与手工铺絮木棉絮料和白鹅绒也很接近,说明木棉纤维絮料有良好的保暖性能。木棉絮料具有一定的防蛀性能,驱螨率达到87.54%,驱螨效果明显,对于大肠杆菌具有明显的杀菌和抑菌效果,对于金黄色葡萄球菌无明显的杀菌和抑菌效果,以上特性源于木棉纤维的特性,与纤维外壁的蜡质有一定关系。(3)木棉羽绒混纤絮料总结了木棉羽绒混纤絮料的试制经验。喂给机中原料总重量以1.5-2公斤为宜,约占喂给机储料箱的70%-80%。当原料中含有羽绒或者飞丝时,随着羽绒含量的增加,喂入辊转速呈线形递减趋势。使用低熔点涤纶粘结比使用ES纤维作为粘结纤维温度要低。面密度每增大100g/m2,固结时间约需翻一倍。木棉羽绒混纤絮料中混入细旦涤纶等合纤可以有效地提高絮料的压缩功弹性回复率。粘结纤维含量小范围的增加会提高压缩功弹性回复率,但是不明显。以木棉纤维取代羽绒或飞丝会导致压缩功弹性回复率略微下降,当其含量变化较小时差异并不明显。羽绒的使用有利于提高絮料的保暖性。木棉纤维对絮料保暖性的贡献仅次于羽绒,高于其他合纤。羽绒飞丝的使用会导致絮料的保暖性下降,但是下降程度不大。(4)改进的纤维集合体传热模型以Woo等的模型为基础模型,改进了基本结构单元的计算方法,给出了改进模型。推导过程中,引入了接触热阻的分析。将去掉接触热阻影响因子的改进模型和Woo等模型的预测值与试样导热系数的实测值进行了分析和比较。对于熔喷非织造布,改进模型和Woo等的模型都能比较准确地预测纤维集合体的导热系数。对于作为保暖材料使用的低密度纤维集合体,在受到较小压力时,纤维体积分数很小,改进模型和Woo等的模型的预测值都偏小。当纤维体积分数为3%左右时,预测值都比较准确。在受到压力较大时,改进模型的预测值较为准确。初步计算了接触热阻的影响因子,计算结果表明与实际情形有较大的差异,因此计算方法尚待进一步的工作。更多还原

【Abstract】 The basic properties of kapok fiber were investigated in this study. With SEM images from kapok fiber, a thin-walled hollow lumen structure was observed in transverse direction, with the thickness of cell wall of about 1μm, and fiber external diameter of about 20μm. A smooth surface with no convolution and closed fiber ends were found along the fiber axis. Kapok fiber of varied genera had no significant difference in the morphology.The length of kapok fiber was closed to Asian cotton ranging from 16 to 24 mm, and the linear density ranging from 0.6 to 0.9 dtex was lower than Sea Island cotton. The fiber diameter of kapok from Indonesia and Thailand was about 17 to 22μm.The tensile properties of kapok fibers were studied by XQ-1 single fiber strength and elongation test meter. The tensile curve of kapok was similar to cotton and flax which had no obvious yield point. Kapok fiber from Indonesia and Thailand had differences in tensile properties. The strength of 1.44 to 1.71 cN and the elongation of 1.8 to 4.2% were found from kapok fiber, and both of them had a certain discret. The relative break strength of 2.03 to 2.70 cN/dtex and the initial modulus of 45 to 116 cN/dtex were closed to cotton, but the strength of kapok was lower than cotton, as well as the elongation.The bending properties of single fibers can be obtaind successfully by testing the fiber sheet employed KES-FB2, Pure Bending Tester. The bending rigidity of kapok was 0.823×10-5 cN·cm2, which was lower than seven-hole hollow PET fiber, four-hole hollow PET fiber and PTT fiber with the same test. The bending rigidity showed a linear relationship between linear density of fibers, but with no significant correlation between the degree of hollowness of fibers. The bending rigidity increased with higher fiber linear density. The bending rigidity of the cotton was slightly less than kapok, but the relative bending rigidity significantly less than kapok. The relative bending rigidity of kapok was 20.80×10-4 cN·cm2tex-2, which was greater than cotton and other three fibers tested.Four kapok battings were obtained successfully by air-forming process and thermo-bonded method. The three of them with seven-hole hollow PET, four-hole hollow PET and PTT had better compressive resilience than PET spray bonding battings, which meant the usage of these fibers leading to better resilience properties. The batting with high proportion of kapok fiber had less resilience properties than PET spray bonding battings. All of them had better resilience properties than kapok batting carded by hand, which confirmed by thermo-bonded method. SEM image of kapok batting after compression test showed kapok fiber still had hollow lumen structure. A reasonable way of machining had no obvious damage on kapok fiber, which leading to better warn retention properties of battings.Pearson correlation analysis was used to verify the relationship between fibers’ linear density, hollowness and crimp to battings’ bulk density, compressibility, compressive resilience and linearity. Using three-dimensional crimp hollow PET fibers improved battings’bulk density and compressibility, but decreased battings’linearity. The resilience properties of battings were negatively correlated with the degree of hollowness of fiber.The battings with high proportion of kapok and other hollow fibers had bigger area density thermal resistance than the one with PTT fibr, which implied battings with hollow fibers be useful to reduce the weight of clothing. Thickness thermal resistance of four kapok battings was greater than PET spray bonding battings. The batting with high proportion of kapok had larger area density thermal resistance and thickness thermal resistance than other three, and closed to the one carded by hand and white goose down, which showed kapok fiber play an important role in battings’warm retention properties.Kapok batting had some anti-moth property. In the anti-mite test, the mite expelling rate was 87.54%, which proved the anti-mite property of kapok batting was obvious. Kapok batting was confirmed to possess both the bactericidal effect and bacteriostatic effect on Escherichia coli. But in contrast, it hadn’t these effects on Staphylococcus aureus. The microbiological properties of kapok batting came from kapok fiber, and the wax in the fiber’s exterior surface could be the contributing substance to provide such properties.On the basis of trial-producing kapok/down battings by air-forming process, some outlines were summarized. The total weight of raw materials in feeding machine was appropriate with 1.5 to 2 kg, and about 70% to 80% of feeding machine’s storage box. When down or down fiber emerging in the raw materials, feed roller speed linearly decreased with the content of down higher. The bonding temperature of low melting point PET fibers was lower than ES fibers. With the Area density increasing by 100 g/m2, the bonding time was about double.The usage of chemical fibers, such as fine-denier PET fibers, etc, could effectively improve the compressive resilience of battings. The compressive resilience of battings had no obvious enhanced by increasing the content of bonding fibers. When kapok replaced down or down fibers in the battings, the compressive resilience of battings would reduce slightly, and it wasn’t obvious while the content of kapok was changed to a small extent. The usage of down could improve the warmth retention abilities of battings, and kapok was less important for improving the warmth retention abilities of battings, but more useful than other chemical fibers, PP, PET, etc. Down fiber could reduce the warm retention abilities of battings, but was not significant.Based on Woo’s heat transfer model, a modified model was given in this study. The numerical model of thermal conductivity of basic structural unit was improved. Thermal contact resistance was concerned on the modified model. Modified model without thermal contact resistance factors was compared to Woo’s model. For melt-blown nonwovens, both of them can accurately predict the thermal conductivity of fiber assemblies. For thermal insulation nonwovens with small fiber volume fraction, the thermal conductivity calculated by Woo’s model and modified model was less than the experiment data. The polar orientation parameter of such materials was difficult to measure directly, and should confirm with more experiments. Radiation heat transfer could not be negligible to the total heat transmitted, which leading to the predicted value of thermal conductivity smaller. Calculation of the thermal contact resistance was still be explored.更多还原