1.1 本试验方法是试验方法的扩展 D1238 专门用于测量聚氯乙烯（PVC）化合物的流速，同时检测和控制与流速相关的各种聚合物不稳定性。 1.2 以国际单位制表示的数值应视为标准值。括号中给出的值是英寸-磅单位的数学转换，仅供参考，不被视为标准值。 1.3 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。 注1: 没有已知的ISO等效于本标准。 1.4 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 本试验方法适用于具有广泛熔体粘度的PVC化合物的质量控制试验。在接近1秒的剪切速率下进行测量 −1. . 5.2 除试验方法中提及的性能外 D1238 该技术对增塑剂含量、聚合物分子量、聚合物稳定性（热稳定性和流变性）、剪切不稳定性和一般成分敏感。材料对温度的敏感性需要比试验方法中规定的更严格的控制 D1238 . 5.3 该测试方法的灵敏度有助于与加工条件相关，并有助于预测加工过程中的变化。然而，作为相对于剪切速率的流动的单点测量，其一个缺点是，对于具有不同加工性能的材料，可以获得相同的PVC熔体流动值；然而，如果这些化合物的成分相似，则发生这种情况的可能性最小。 5.4 与广泛加工条件的相关性支持了以下结论:在试验过程中，成分变化很小或没有变化。 因此，该测试能够检测并跟踪挤出、注塑、铣削或混合过程中发生的深刻变化。这些变化是由于聚合物中测量到的三种不稳定性引起的: 5.4.1 温度效应引起的热不稳定性。 5.4.2 聚合物键断裂引起的剪切不稳定性。 5.4.3 由于粘度或分子量元素的不均匀分布而导致的流变不稳定性。 5.4.4 因此，可以检测和预测PVC分子结构变化的影响。

1.1 This test method is an extension of Test Method D1238 specific to the measurement of flow rates of poly(vinyl chloride) (PVC) compounds while detecting and controlling various polymer instabilities associated with the flow rate. 1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard. 1.3 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. Note 1: There is no known ISO equivalent to this standard. 1.4 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 This test method is useful for quality-control tests on PVC compounds having a wide range of melt viscosities. Measurements are made at shear rates close to 1 s −1 . 5.2 In addition to the properties mentioned in Test Method D1238 , this technique is sensitive to plasticizer content, polymer molecular weight, polymer stability (both thermally and rheologically), shear instability, and general composition. The sensitivity of the material to temperature necessitates slightly tighter controls than those stated in Test Method D1238 . 5.3 The sensitivity of this test method makes it useful for correlating with processing conditions and as an aid in predicting changes in processing. However, as a one-point measure of flow relative to shear rate, its one drawback is that the same PVC melt flow values can be obtained for materials having different processibility; the chance of this happening is minimized, however, if the compounds are similar in composition. 5.4 Correlations with a wide range of processing conditions have supported the conclusions that little or no change in composition occurs during the test. Thus, this test is able to detect and follow profound changes which occur during extrusion, injection molding, milling, or mixing. These changes are due to three types of measured instability in polymers: 5.4.1 Thermal instability due to temperature effect. 5.4.2 Shear instability due to breaking of polymer bonds. 5.4.3 Rheological instability due to nonuniform distributions of widely different viscosity or molecular weight elements. 5.4.4 Thus, implications with respect to PVC molecular structural changes can be detected and predicted.