ASTM C679-15 pdf free download.Standard Test Method for Tack-Free Time of Elastomeric Sealants.
1 .1 This test method covers a procedure for the determinalion of the tack-free time property of single- and multi- component elastomerw sealants commonly used for sealing, caulking, and gIaing in buildings and related construction.
1.2 This test method is applicable to self-lei’eliizg and non-sag grades of sealant. Sealants requiring slight heating to facilitate extrusion from the cartridge or gun are also described by this test method.
4. Summary of Test Method
4.1 The test consists of lightly touching a surface of a curing sealant with a polyethylene film at regular intervals until the sealant does not attach itself to the film and the film appears clean when peeled from the surface.
4.2 More specifically a strip of polyethylene film is placed on the surface of the curing sealant and a 30-g (I .06-oz) weight is placed on the film. The weight is left in place for 30 s, then removed and the polyethylene strip is removed and examined for sealant attachment to the film. The length of time from when the sealant was first applied and tooled into the template until the time the sealant is no longer picked up by the film is called tack-free time.
4.3 With some sealants, interpretation of the end point is confusing in that a very thin film of sealant or oil will transfer to the film. For consistency of data, record the point where the bulk sealant is no longer transferred to the plastic but ignore the very thin uniform film of sealant or the plasticizer transferred to the plastic test strip.
5. Significance and Use
5.1 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.
5.2 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.
5.3 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 ditBrent than the standard conditions called out in this test method, then those conditions be used to test the sealant.
6. Apparatus
6.1 Cabinet, or Room, capable of maintaining Standard Conditions.
6.2 Weight, rectangular, with dimensions of 41 by 19 mm (1 5/8 in. long by 3/4 in. wide) and mass of 30 g (1.06 oz).ASTM C679 pdf download.