1.1 本试验方法包括在单纱（细纱或长丝）、合股纱、缆索纱或新颖纱（不包括长期重复图案）的任何加捻阶段完成时测定捻度的大小和方向。该程序主要针对包装中的纱线设计，但在采取特殊预防措施后，适用于从织物中提取的纱线。纺纱工序 9.2 也适用于粗纱。 1.2 对于合股纱，本试验方法包括测定合股纱的捻度和合股前单纱的捻度。对于缆绳纱线，试验方法包括测定缆绳或缆绳的捻度； 合股后但在最后一次加捻操作之前合股纱线的捻度；以及单纱在合股前的捻度。当单纱和合股纱组成部分位于最终结构中时，还包括测定其捻度的程序。此外，还介绍了使用直接布线技术制造的股线捻度的测定方法。 1.3 本试验方法不适用于延伸超过5.0的纱线 % 当张力从2.5 mN/tex增加到7.5 mN/tex[0.25到0.75 gf/tex]时。遵循本试验方法的程序，此类纱线将独立于本试验方法确定的偏差和精度。 此类测试的报告应包括用于该测试的张力。 1.4 单位- 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值不一定是精确的等价物；因此，为确保符合本标准，每个系统应独立使用，且两个系统的值不得组合。 注1: 有关测定单纱捻度的更快速但不太准确的方法，请参阅测试方法 D1422 . 注2: 本试验方法已用于测定开口纱线的捻度，不推荐使用。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 试验方法 D1423 通过直接计数测试纱线捻度被认为是商业装运验收测试的满意方法，因为目前实验室间精度的估计是可以接受的，并且该方法已在验收测试行业中广泛使用。 5.1.1 如果两个实验室（或更多实验室）的报告测试结果之间存在实际意义上的差异，则应进行比较测试，以确定它们之间是否存在统计偏差，并使用适当的统计协助。作为最低限度的使用样品进行此类比较试验，样品应尽可能均匀，从相同批次的材料中提取，产生不同的试验结果，并随机等份分配给每个实验室。 应使用未配对数据的统计测试，在测试系列之前选择的概率水平上，对相关实验室的测试结果进行比较。如果发现偏差，必须找到并纠正其原因，或者考虑到已知偏差，必须调整该材料的未来测试结果。 5.2 测定纱线直段中的捻度并不像看上去那样简单直接，因为测试程序和技术的变化可能会极大地影响测试结果。在所有操作中，必须格外小心，以防止试样旋转在测试开始前改变扭转水平。 5.3 由于张力变化和退卷方法的影响，纱线在包装前的捻度可能不同于从包装中退卷后的捻度。如果纱线从末端抽出，则捻度会略有增加或减少，具体取决于纱线中的捻度方向、包装上的卷绕方向和包装上的包裹长度。 5.4 当纱线并入或从更复杂的结构中取出时，由于合股、解捻或散开操作，可能会发生变化。例如，当通过确定原始捻度的程序确定合股纱线的捻度时，当合股纱线未经捻度时，可将相当数量的捻度重新插入或从单根纱线中移除- 纱线成分。因此，单纱在合股操作之前具有大约原始的捻度，但在作为合股纱的组成部分时没有捻度。根据帘布层和单纱捻度的方向，可以通过将帘布层捻度添加到单纱捻度（或从中减去）来估计后一捻度或最终捻度。为了进行更精确的测定，必须修改试验程序。因此，有两种不同的程序来制备用于测定捻度的股线或缆索纱线的组成元素样本。原始捻度的程序测量复合股的一个组件在解开组件后的捻度。 最终扭转程序测量部件位于复杂股中时的扭转。虽然最常用的是原始扭曲程序，但特定程序的选择将取决于所需信息的类型。 注3: 从侧面退绕和从上方退绕之间的扭曲度差为1/4π d 哪里 d 是包装的直径。 3. 因此，对于25毫米[1英寸]直径包，差值约为13 tpm或约 1. / 3. tpi。 5.5 当纱线取自更复杂的纱线结构或织物时，由于退绕、处理和加工过程中遇到的机械应变的影响可能会发生变化，因此产生的捻度应仅被视为原始值的近似值。 5.6 最佳捻度取决于纱线的用途。捻度的大小会影响纱线的强度和伸长率，捻度的增加与伸长率的增加有关。扭转和强度之间的关系更为复杂。 5.6.1 在长丝纱线中，需要一些高达280 tpm[7 tpi]的捻度或适当的上浆，以便于纺织操作。扭曲度的小幅增加会导致强度略有增加，但进一步增加会导致强度损失。然而，这种纱线中较高的捻度可用于降低光泽或增加伸长率，或确保其他特殊效果，如在绉纱织物中。 5.6.2 在传统环锭纺纱线中，需要一定的最小捻度来将单个纤维结合或固定在一起，以生产出有用的纱线。在达到特定纱线的临界捻度水平之前，捻度的有限增加将导致强度的增加，但捻度的进一步增加会导致强度的损失。 5.7 不同尺寸（直径）的纱线中相同的捻度将产生不同紧密度、捻度特性和捻度角度的纱线。捻度倍增器或捻度系数与表面纤维与纱线轴线的夹角的切线近似成比例。 因此，角度越大，扭曲倍数越大。恒定的捻度倍数表示不同尺寸的纱线具有可比的紧密度和活力程度，相反，捻度倍数的差异表示相同尺寸的纱线具有不同的紧密度。用于不同用途的纱线通常使用不同的捻度倍增器制造，例如经纱和填充纱。 5.8 不同的布线过程将影响单组件扭曲测量的扭曲计算。使用直接布线技术计算单个组件的捻度时，使用解捻前的电缆纱线长度。 在两步或多步加捻技术的情况下，解捻后的电缆纱长度用于计算单纱组分中的加捻水平。 5.9 捻度倍增器和捻度系数是对纺纱“捻度硬度”的测量，因为它们与纺纱外表面纤维与纺纱轴线之间的夹角的切线近似成比例；这个角度越大，扭转就越困难。此外，该角度是捻度含量（单位长度的圈数）和每根纱线横截面的纤维数（纱线数）的函数。因此，单靠捻度不能测量纱线的捻度硬度。

1.1 This test method covers the determination of the amount and direction of twist at the completion of any stage of twisting in single (spun or filament), plied, cabled, or novelty (exclusive of long-term repeat patterns) yarns. The procedures are designed primarily for yarns in packages, but, with special precautions, they are applicable to yarns taken from fabrics. The procedure for spun yarn in 9.2 is also applicable to rovings. 1.2 For plied yarns, this test method covers the determination of the twist of the plied yarns and the twist of the single yarn before plying. For cabled yarns, the test method covers the determination of the cable or hawser twist; the twist of the plied yarn after plying, but prior to the last twisting operation; and the twist of the single yarn before plying. Procedures are also included for the determination of the twists of the single and plied yarn components as they lie in the final structure. Also, directions are included for the determination of twist in plied yarn made with direct cabling technology. 1.3 This test method is not intended for yarns that extend more than 5.0 % when tension is increased from 2.5 to 7.5 mN/tex [0.25 to 0.75 gf/tex]. Following the procedures of this test method for such yarns would be independent of the bias and precision determined for this test method. The report from such testing should include the tension used for this testing. 1.4 Units— The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. Note 1: For a more rapid but less accurate method of determining twist in single spun yarns, refer to Test Method D1422 . Note 2: This test method has been evaluated for use in determining twist in open end yarns and is not recommended. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Test Method D1423 for testing twist in yarns by direct-counting is considered satisfactory for acceptance testing of commercial shipments because current estimates of between-laboratory precision are acceptable and the method has been used extensively in the trade for acceptance testing. 5.1.1 If there are differences of practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum use the samples for such comparative tests as homogeneous as possible, drawn from the same lot of material that resulted in the disparate test results and randomly in equal numbers to each laboratory. The test results from the laboratories involved should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If a bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias. 5.2 The determination of twist in a straight section of a yarn is not the simple straightforward operation it appears to be, for the test results may be greatly influenced by variations in test procedures and techniques. In all manipulations, extreme care is necessary to prevent specimen rotation altering the twist level before testing begins. 5.3 The twist in a yarn before it is packaged may be different from that of the yarn after it has been withdrawn from the package because of changes in tension and the effect of the method of withdrawal. If the yarn is withdrawn over-end, a slight increase or decrease in twist will take place, depending upon the direction of the twist in the yarn, the direction of winding on the package, and the length of the wrap on the package. 5.4 When a yarn is incorporated into or removed from a more complex structure, alterations may occur as a result of the plying, untwisting, or raveling operation. For example, when determining the twist in plied yarn by the procedure for determining original twist, as the plied yarn is untwisted, a comparable amount of twist is reinserted in, or removed from, the single-yarn components. As a consequence, the single yarns have approximately the original twist prior to the plying operation but not the twist they have when they are functioning as components of the plied yarn. The latter or final twist may be estimated by adding the ply twist to (or subtracting it from) the single-yarn twist depending on the directions of the ply and singles twist. For a more precise determination, the test procedure must be modified. There are thus two different procedures for preparing specimens of the component elements of a plied or cabled yarn for twist determination. The procedure for the original twist measures the twist in a component of a complex strand after the components have been untwisted. The procedure for final twist measures the twist in a component as it lies in the complex strand. Although the original twist procedure is most often used, selection of a particular procedure will depend on the type of information needed. Note 3: The difference in twist between unwinding from the side and over-end is 1/π d , where d is the diameter of the package. 3 Thus, for a 25 mm [1-in.] diameter package, the difference would be about 13 tpm or about 1 / 3 tpi. 5.5 When a yarn is taken from a more complex yarn structure or from a fabric, the resultant twist should be considered only an approximation of the original value because of alterations that may have occurred as a result of the effects of unwinding, handling, and mechanical strains met in processing. 5.6 The optimum amount of twist depends upon the use for which the yarn is intended. The amount of twist affects both the strength and elongation properties of the yarn with increased twist being associated with increased elongation. The relationship between twist and strength is more complex. 5.6.1 In filament yarns, some twist up to 280 tpm [7 tpi] or a suitable sizing is required to facilitate textile operations. A small increase in twist results in a slight increase in strength, but a further increase results in a loss in strength. However, higher twist in such yarns may be used to subdue luster or increase elongation, or to secure other special effects, as in crepe fabrics. 5.6.2 In conventional ring spun yarns a certain minimum amount of twist is necessary to bind or hold the individual fibers together to produce a useful yarn. A limited increase in twist will result in an increase in strength until the critical twist level for the particular yarn involved has been reached, but further increase in twist results in a loss in strength. 5.7 The same amount of twist in yarns of different sizes (diameter) will produce yarns with different degrees of compactness, twist character, and twist angles. The twist multiplier or twist factor is approximately proportional to the tangent of the angle that the surface fibers make with the axis of the yarn. Therefore, the greater the angle, the greater the twist multiplier. A constant twist multiplier indicates comparable compactness and degree of liveliness in yarns of different sizes and conversely a difference in twist multiplier indicates a difference in compactness in yarns of the same size. Yarns intended for different uses are frequently made with different twist multipliers, for example, warp yarns and filling yarns. 5.8 Different cabling processes will influence the calculation of twist from single component twist measurement. The length of cabled yarn before untwisting is used for the calculation of twist for single components using direct cabling technology. In case of 2 or more step twist technology the length of the cabled yarn after untwisting is used for calculation of the twist level in the single yarn components. 5.9 Twist multiplier and twist factor are a measure of the “twist hardness” of spun yarn because they are approximately proportional to the tangent of the angle between fibers on the outer yarn surface and the axis of the spun yarn; the larger this angle, the harder the twist. Furthermore, this angle is a function of both the twist content (turns per unit length) and the number of fibers per yarn cross section (yarn number). Hence, twist content alone cannot provide a measure of the twist hardness of a yarn.