GB/T 17821-2008 in English

《GB/T 17821-2008胶乳 5℃至40℃密度的测定》由TC35（全国橡胶与橡胶制品标准化技术委员会）归口，TC35SC8（全国橡胶与橡胶制品标准化技术委员会天然橡胶分会）执行，主管部门为中国石油和化学工业联合会。
本标准代替ＧＢ／Ｔ１７８２１―１９９９《胶乳　５℃至４０℃密度的测定》。本标准规定了在5℃～40℃温度下测定浓缩天然胶乳密度的方法。本标准是为了在不能直接称量或不能控制实验室温度的情况下利用密度测定来计算已测定体积的胶乳的质量而制定的。用于测定密度的胶乳样品中所含的空气数量应与测定体积时所含的空气数量相同。因此，在取样前应让胶乳静置至少24h，以便能除去气泡。测定密度时的温度宜与测定体积时的温度相同，否则就应进行校正。本标准适用于各种天然胶乳以及合成胶乳、配合胶乳和预硫化胶乳，也适用于橡胶水分散体。但7.2中所列的温度校正对这些胶乳不一定都适用。在第２章规范性引用文件引用了ＧＢ／Ｔ８２９０，该标准与ＩＳＯ７０５：１９９４ 的相应部分没有技术性差异。 本标准与ＧＢ／Ｔ１７８２１―１９９９相比主要差异是按ＧＢ／Ｔ１．１―２０００和ＧＢ／Ｔ２０００１．４―２００１的要求对ＧＢ／Ｔ１７８２１―１９９９作了编辑性修改。

Scope

WARNING—Personnel using this standard should have experience in formal laboratory practice. This standard does not address all possible safety issues. It is the user's responsibility to take appropriate safety and health measures and ensure compliance with the conditions stipulated in the relevant national laws and regulations. This standard specifies the method for measuring milk density at a temperature of 5°C to 40°C. This standard is formulated for the use of density determination to calculate the mass of latex whose volume has been determined when it is not possible to directly weigh or control the temperature of the laboratory. The latex sample used for density determination should contain the same amount of air as it was for volume determination. Therefore, the latex should be allowed to stand for at least 24 hours before sampling in order to remove air bubbles. The temperature when measuring the density should be the same as the temperature when measuring the volume, otherwise it should be corrected. This standard applies to all kinds of natural rubber latex and synthetic latex, compound latex and prevulcanized latex, and also applies to rubber aqueous dispersions. However, the temperature corrections listed in 7.2 do not necessarily apply to these latexes.