就是要符合《ASTM C920 弹性密封胶挤出性表干时间老化性能测试》中规定的Class 35级要求。见下截屏：
Class 50—Asealant that when tested for adhesion andcohesion under cyclic movement (8.8) shall withstand anincrease and decrease of at least 50 % of the joint width asmeasured at the time of application, and, in addition, meet allthe requirements of this specif i cation.4.1.7 Class 35—A...
4.1.7Class 35—A sealant that when tested for adhesion and cohesion under cyclic movement (8.8)shall withstand an increase and decrease of at least 35%of the joint width as measured at the time of application,and,in addition,meet all the requirements of this specification.1 This speci...
1、Designation: C920 14aC920 18Standard Specification forElastomeric Joint Sealants1This standard is issued under the fixed designation C920; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pa...