1.1 规范中所述由交联聚乙烯塑料生产的管材的凝胶含量 第876页 而其他管道或管材标准品是通过用溶剂如二甲苯萃取来确定的。本文描述了一种定量测定凝胶含量的试验方法。该方法适用于所有密度的PEX管道，包括含有填料的管道，并对其中一些化合物中存在的惰性填料进行校正。 1.2 连续提取（见第节中的定义 3. )在该方法中用于测试交联聚乙烯样品的凝胶含量。当用于测试凝胶含量时，连续提取具有降低测试成本、提高结果的准确性和一致性以及减少测试时间的优点。这是因为用纯溶剂提取比用部分饱和溶剂提取更有效。 1.3 虽然可以对任何形状的物品进行提取试验，但该试验方法适用于测定交联聚乙烯管道的凝胶含量。 1.4 本试验方法使用二甲苯或替代溶剂。替代溶剂要么具有比二甲苯更低的毒性，要么允许减少提取时间。从经济和环境的角度来看，替代溶剂也是潜在的有益的。 二甲苯用于鉴定试验。 1.5 以国际单位制表示的数值应视为标准。括号中的英寸磅单位仅供参考。 1.6 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的使用者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。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 交联乙烯塑料的许多重要性能随凝胶含量的不同而变化。因此，凝胶含量的测定为控制生产过程提供了基础，也为确定成品质量提供了手段。 5.2 提取试验允许验证任何给定交联乙烯塑料的适当凝胶含量，也允许比较不同的交联乙烯塑料，包括含有填料的交联乙烯，前提是后者满足以下条件: 5.2.1 在提取温度下，填料不溶于该方法中使用的溶剂。 5.2.2 存在于化合物中的填料的量是已知的或者可以确定。 5.2.3 已经实现了足够的交联以防止填料在提取过程中迁移。已经发现，在凝胶含量超过30 %, 溶剂保持澄清且不含填料。 5.3 由于材料和溶剂的一些氧化降解可能在溶剂的回流温度下发生，因此向溶剂中添加合适的抗氧化剂以抑制这种降解。 5.4 该测试方法通常用于由产品整个横截面的相等表示组成的样品，但也可用于检查产品的特定部分与产品标准或另一样品相比交联程度的差异。 5.5 本试验方法旨在测试不吸湿的交联聚乙烯化合物。如果使用这种方法测试吸湿性化合物，则需要在提取前后对样品进行调理。 5.6 本试验方法与试验方法不同 2765英镑 ，ISO 10147和试验方法 第7567页 其还描述了用于测定交联聚乙烯的凝胶含量的程序。它允许使用环烷烃混合物、异链烷烃溶剂或轻质芳香族溶剂石脑油作为二甲苯的替代品。二甲苯是唯一允许用于鉴定试验的溶剂。在这种测试方法中，样品制备的首选方法是使用车床制作PEX材料的薄带。 本标准要求使用连续萃取器，以提供一致的结果并允许可靠的溶剂重复使用。专门的样品支架用于最大限度地减少样品颗粒损失造成的可变性。 注1: 已发现加压提取技术在较短的时间内产生有用的结果，然而并非所有等级的PEX都能耐受升高的提取温度而不会显著降解。因此，只有当可以确定交联的PEX基质在提取温度下不会分解时，才建议使用加压提取技术进行对照试验

1.1 The gel content of pipe and tubing produced from crosslinked polyethylene plastics as described in Specification F876 and other pipe or tubing standards is determined by extracting with solvents such as xylenes. A test method for quantitative determination of gel content is described herein. The method is applicable to PEX pipe and tubing of all densities, including those containing fillers, and provides correction for the inert fillers present in some of those compounds. 1.2 Continuous extraction (see definition in Section 3 ) is used in this method to test the gel content of crosslinked polyethylene specimens. Continuous extraction when used for testing gel content has the advantages of decreased cost of testing, increased accuracy and consistency of results, and decreased test time. This is because extraction with a pure solvent is more efficient than extraction with a partially saturated solvent. 1.3 While extraction tests may be made on articles of any shape, this test method is applicable for determining the gel content of crosslinked polyethylene pipes and tubing. 1.4 This test method makes use of xylenes or alternative solvents. Alternative solvents either have lower toxicity than xylenes or allow decreased extraction times. The alternative solvents are also potentially beneficial from an economic and environmental viewpoint. Xylenes are used for referee tests. 1.5 The values stated in SI units are to be regarded as standard. The inch-pound units in brackets are for information only. 1.6 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. 1.7 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 Many important properties of crosslinked ethylene plastics vary with the gel content. Hence, determination of the gel content provides a basis for controlling production processes and a means of establishing the quality of finished products. 5.2 Extraction tests permit verification of the proper gel content of any given crosslinked ethylene plastic and they also permit comparison between different crosslinked ethylene plastics, including those containing fillers, provided that, for the latter, the following conditions are met: 5.2.1 The filler is not soluble in the solvent used in this method at the extraction temperature. 5.2.2 The amount of filler present in the compound either is known or can be determined. 5.2.3 Sufficient crosslinking has been achieved to prevent migration of filler during the extraction. It has been found that, at gel content above 30 %, the solvent remains clear and free of filler. 5.3 Since some oxidative degradation of the material and solvent may occur at the reflux temperature of the solvents, a suitable antioxidant is added to the solvent to inhibit such degradation. 5.4 This test method is normally used for specimens consisting of an equal representation of the entire cross section of the product, but may also be used to examine specific portions of a product for differences in extent of cross-linking when compared to either a product standard or another sample. 5.5 This test method is intended for testing crosslinked polyethylene compounds that are not hygroscopic. If compounds that are hygroscopic are tested using this method, specimen conditioning before and after extraction is required. 5.6 This test method differs from Test Methods D2765 , ISO 10147 and Test Method D7567 which also describe procedures for determining the gel content of crosslinked polyethylene. It allows for the use of naphthenic hydrocarbon blend, isoparaffin solvent, or light aromatic solvent naptha as alternatives to xylenes. Xylenes are the only solvent allowed to be used for referee tests. The preferred method of sample preparation in this test method is to use a lathe to create thin ribbons of PEX material. This standard requires the use of a continuous extractor in order to provide consistent results and to allow for reliable solvent re-use. Specialized specimen holders are used to minimize variability resulting from loss of specimen particles. Note 1: Pressurized extraction techniques have been found to yield useful results in a shorter time frame, however not all grades of PEX tolerate the elevated extraction temperatures without substantial degradation. For this reason pressurized extraction techniques are recommended for control tests only if it is possible to determine that the crosslinked matrix of the PEX does not break down at the temperature of extraction