变形纱线膨松性能的表征与EIB测试:2.工艺参数与膨松度的关系

 为最终达到空气变形纱线及其多重变形纱线结构和性能设计的目标,对长丝原料及几个关键变形工艺参数进行了初步的单因子实验。结果显示,异收缩空气变形纱的膨松度可以通过选择单、复丝的线密度、空气变形加工和异收缩变形加工工艺参数的方法加以有效控制。空气变形加工工艺参数中的超喂率和喂入方式,异收缩变形加工工艺参数中的异收缩率、平均收缩率对成纱的膨松性能有显著影响。     

变形纱表观条干均匀度和质量条干均匀度研究

 与短纤维纱线不同,变形纱的质量条干均匀度和外观条干均匀度是2个相对独立的指标。EIB检测结果表明,空气变形纱的表观条干CV值接近于短纤维纱条干CV值,异收缩-空气变形纱的表观条干CV值与短纤维纱条干CV值持平;空气变形纱表观直径变化总频数高于短纤维纱;空气变形纱表观直径变化频数集中分布于-25%~25%短片段区域,异收缩空气变形纱的表观直径变化频数分布集中于-25%~50%的较长片段区域,这与短纤维纱的情况相同,显示了良好的仿短纤维纱效果。Uster®条干均匀度仪测试结果表明,空气变形纱和异收缩空气变形纱的质量条干均匀度CV值明显低于短纤维纱条干CV值,这对保持纱线的力学性能有利。     

空气变形工艺对成纱熵变的影响

化纤长丝在变形加工,尤其是在空气变形加工过程中会发生明显的熵变现象,研究表明成纱熵变与变形纱各主要结构性能参数之间存在显著的相关性。为了查明变形工艺参数对成纱熵变的影响,针对目前较具代表性的空气变形工艺参数和异收缩变形工艺参数设计了单因子试验,主要包括单复丝规格、空气变形加工超喂率和异收缩差等。结果显示,在单丝线密度一定条件下,成纱熵变随着复丝线密度的增加而增加;在复丝线密度一定的条件下,成纱熵变随单丝线密度的增加而降低。在空气变形加工过程中,成纱熵变随丝束超喂率的增加而增加。在异收缩变形加工中,成纱熵变随着异收缩差的增大而增大。     

长丝变形纱的皮芯结构及其参数

在变形纱中,空气变形类和异收缩变形类纱线具有皮芯结构,有必要对其成形原理和结构模型加以概括和总结。借助实验观察和理论分析的方法,认为虽然上述2种变形纱皮芯结构的成形原理不相同,但模型都可以描述为紧密网络扭结的芯层和松散圈弧形态的皮层结构。结合EIB实验验证,可以进一步确认变形纱的皮芯结构参数主要包括由纱线平均直径、纱芯平均直径和丝圈丝弧高度等项目,因而也可断定变形纱皮芯结构与变形纱膨松度、变形纱条干均匀度以及变形纱毛羽的各项特性指标有密切关系。     

空气变形纱的抗弯性能

针对空气变形纱线抗弯刚度过高的现象,以及由此产生的其在日用纺织品和服装领域的应用和发展限制问题,利用悬臂梁法测量经典纱线、空气变形纱及异收缩丝空气变形纱的抗弯刚度值.结果显示,空气变形纱比同规格棉、毛纤维环锭纱的抗弯刚度高出2倍以上.空气变形纱加工成形过程中通过纤维空间排列秩序性变化形成的缠结结构是其抗弯性能的结构根据...     

工艺参数对变形纱不稳定性的影响

变形纱的不稳定性受快速变形时超喂和空气压力交互作用的影响。增加超喂和变形速度 ,纱线不稳定性会增大。变形纱在高速变形超喂加工中 ,不稳定性的变化会很大。空气压力增加 ,低速变形时纱线不稳定性就减少 ,而高速变形时会增大。决定织物中变形纱能够达到的蓬松程度方面 ,变形纱的不稳定性起了很重要的作用。进一步加工中 ,较大的不稳定性也会引起变形纱较大的不规则性 ,影响织物的外观。对工艺参数的影响已经有了报道 ,比如超喂、空气压力和变形速度。增加超喂和变形速度 ,纱线不稳定性增加。然而空气压力对变形纱不稳定性的影响也有截然…     

空气变形纱成纱熵变与外观光泽的关系

 纱线系统的相对熵值在成纱过程当中会发生明显的变化，因其与紊乱度直接相关，所以对纱线的外观光泽也存在较大的影响。为查明变形纱线成纱熵变与其外观光泽之间的内在联系和作用方式，选择具有典型的紊乱结构，且表面紊乱程度较大的空气变形类型的纱线为对象，对多种规格的原复丝进行了单因子试纺，并做相应测试分析。实验表明，空气变形加工可明显提高成纱结构的紊乱度（1.28－4.25）和相对熵值（0.3－1.45），而异收缩多重变形也同样可以提高纱线的紊乱度和相对熵值，不过增幅相对较小;随着相对熵值和紊乱度不断增加，变形纱线的峰值反射率和反射率下降，峰宽率增加，光泽柔和，极光减退。     

变形纱成纱熵变对条干均匀度的影响

长丝变形纱在变形加工过程中,其成纱熵变是增加的。成纱熵变是状态函数,其与变形纱紊乱度的对数成正比,因此成纱熵变对变形纱的表观条干均匀度有显著影响。随着成纱熵变和紊乱度不断增加,变形纱的外观和性能均发生明显改变,其表观CV值迅速增加,并接近短纤维纱条干CV值,仿短纤维纱化效果明显。这种状况可通过长丝变形纱表观直径变化总频数及频率分布加以表现。由膨松结构引起的空气变形纱表观条干均匀度值的异常改变使其与质量条干均匀度值不相关,这是变形纱区别于传统短纤维纱的主要特征之一。     

长丝变形纱成纱熵变对抗弯刚度的影响

 长纤复丝经变形加工,其结构系统熵值增大,这一现象往往与长复丝系统抗弯刚度的变化伴随发生。采用悬臂梁方法测试变形纱抗弯刚度,采用EIB测量变形纱直径而后测算变形纱相对熵值,可对变形加工过程中线性体发生的熵变现象和抗弯刚度变化的关系进行定量分析。经测试,空气变形加工可使成纱相对熵值由0.3增加到1.45,紊乱度由1.28增加到4.25;再经异收缩多重变形相对熵值可增加到1.65,而紊乱度可增加到5.00左右。长丝片段紊乱度增加直接导致空气变形类纱线紊乱结构和缠结结构的形成与扩大,在宏观上呈现纱线抗弯刚度的迅速增大,从而进一步导致纱线手感变坏;多重变形有可能使已形成的纱线缠结结构得到调整,从而使纱线抗弯刚度下降。     

提高CJ11.7tex纱条干均匀度的工艺配置

在生产CJ11.7tex纱的基础上分析了纱线条干均匀度的影响因素。为了提高细纱条干均匀度,对影响成纱条干均匀度的前区工艺参数、后区牵伸工艺进行了工艺配置。实验结果证明,采用较小的粗纱定量、细纱捻系数、前中罗拉隔距、较小的钳口隔距、较小的后区牵伸倍数,以及较大的前胶辊压力,采用较大前胶辊直径,适当增加粗纱捻系数等措施,可以提高成纱条干CV值。     

Steam as an alternative fluid for air in spun-like texturing: effect of core-yarn draw and core-yarn heat setting on texturing performance

The objectives of this research work were to investigate the use of high-pressure steam in order to replace air in the production of spun-like textured yarns and to investigate the effect of core-yarn draw ratio and core-yarn heat setting on texturing performance. An existing air jet texturing machine was modified to supply either air or steam to the texturing nozzle. Using an identical nozzle, both air-jet and steam-jet textured yarns were manufactured. Results show that the core-yarn and textured yarn tension increase and the loop instability decreases when the core-yarn draw ratio is increased. Therefore, it can be predicted that the core-yarn draw ratio has influence on the performance of both air jet and steam jet texturing. Boiling water shrinkage of core-yarn as well as air-jet and steam-jet textured yarn increases when the core-yarn draw ratio was increased. However, steam-jet textured yarn has lower boiling water shrinkage than both core-yarn and air-jet textured yarn. Core-yarn heat setting does not have influence on core-yarn and textured yarn tension in the air jet texturing. In steam jet texturing, core-yarn heat setting reduces core-yarn and textured yarn tension. Therefore, it can be predicted that core-yarn heat setting is important for steam jet texturing.     

Investigation of the effect of core-yarn wetting on air-jet and steam-jet spun-like texturing performance

The objective of the research work was to investigate the use of steam as an alternative fluid for air in spun-like textured yarn manufacturing and to investigate the effect of wetting on texturing performance. An existing air-jet texturing machine was modified to supply either air or steam to the texturing nozzle. Both air-jet and steam-jet textured yarns were made using the same process parameters with and without core-yarn wetting. The effect of core-yarn wetting on the texturing performance has been studied. Results show that core-yarn wetting is critical for air-jet texturing but do not have considerable impact on steam-jet texturing. Therefore, core-yarn wetting could be eliminated in steam-jet texturing. Further, steam-jet texturing shows its capability in manufacturing spun-like textured yarns with better performance than the air-jet. Therefore, it can be concluded that steam can be used as an alternative fluid for air in making spun-like textured yarns without core-yarn wetting.     

Effect of nozzle size on texturing performance: comparison between air-jet and steam-jet texturing

The objectives of this research work were to investigate the use of steam in order to replace air in the production of spun-like textured yarn and to investigate the optimum nozzle size for steam-jet textured yarn for the application of sewing thread. An existing air-jet texturing machine was modified to supply either air or steam to the texturing nozzle. Using four texturing nozzles, both air-jet and steam-jet textured yarns were manufactured. The effect of nozzle size on process and yarn parameters has been studied and compared with air-jet textured yarns. The results show that spun-like textured yarn manufactured using steam has lower loop instability and higher tensile properties than air at comparable fluid pressures. SEM image analysis shows that the entangled structure of the steam-jet textured yarns is similar to air-jet textured yarns. Further, sewability results show that steam-jet textured yarns are suitable to manufacture sewing threads.     

纱线膨松性能的表征与EIB测试:1.膨松度的概念与测试

 膨松性能是变形纱最基本的性能之一,可用膨松度表征。纱线的膨松度是以纱线空隙率即纱线体内部纤维间的空隙占纱线整体的体积分数定义的。实验证明:用EIB检测各类纱线的表观平均直径并计算膨松度有良好的适应性;空气变形纱的膨松度阈值在70%~75%之间;异收缩空气变形纱的膨松性好于空气变形纱,其膨松度约高出5%;2种环锭纺短纤维纱,精梳棉纱和精纺毛纱的膨松度阈值为55%~60%,其中精纺毛纱比精梳棉纱高5%;加捻化学纤维长丝束的膨松度为20%~25%,经变形加工后其膨松度可以提高2倍左右。     

Effects of core-yarn overfeed on texturing performance: comparison between air-jet and steam-jet texturing

The objectives of this research work were to investigate the use of high-pressure steam in order to replace air in the production of spun-like textured yarns and to investigate the optimum level of core-yarn overfeed ratio for steam-jet textured yarn for the application of sewing threads. An existing air-jet texturing machine was modified to supply either air or steam to the texturing nozzle. Using an identical nozzle, both air-jet and steam-jet textured yarns were manufactured. Loop instability and loop density increased and strength and tenacity decreased when the core-yarn overfeed was increased in both air-jet and steam-jet textured yarns. Steam-jet textured yarns have lower loop instability, lower loop density and higher tensile properties than that of the air-jet textured yarns. Sewability results show that for both air-jet and steam-jet textured sewing threads, core-yarn overfeed ratios of 5.5 and 8.3% give better sewability.