表干时间，单组份室温硫化硅橡胶暴露在大气环境里固化过程中，用手指触摸表面，黏性消失，不黏手的时间，具体应用时候应指出环境温度。

英文：tack free time，简称：TFT

测定方法原理：在规定条件下将密封材料试样填充到规定形状的模框中，用在试样表面放置薄膜或者指接触的方法测量其干燥程度。报告薄膜或手指上无粘附试样所需要的时间。

详细可以参考GB/T 13477.5-2002 建筑密封材料试验方法 第5部分:表干时间的测定

The time period during which a sealant that is molded in the field remains tacky and is not yet fully serviceable. The tack-free time is a measure of the surface cure time and may generally be correlated to a variety of useful parameters such as the time interval before the sealant

(1) resists damage by touch or light surface contact,

(2) resists job-site or airborne dirt pick-up

(3) resists impinging rainfall.

The tack-free time is sometimes used as an on-the-job quality assurance test. A quality product that is consistent and reproducible will generally fall within a maximum and minimum tack-free time.

This test for tack-free time can be used at any temperature and humidity. It is important that if a sealant will be used in a climate quite different than the standard conditions called out in this test method, then those conditions be used to test the sealant.