ASTM C679:2003 pdf free download – Standard Test Method for Tack-Free Time of Elastomeric Sealants.
6.4 capable of measuring minutes and hours.
6.5 Rectangular Plates, several (often 6 or more), rectangular. appwximatcly 152 by 76 mm (6 by 3 in.), made of non-porous material such as. tin plated steel or aluminum.
6.6 Template. rectangular. of steel, brass or other suitable material. 3.2 mm (hick with inside dimensions 95 by 25.4mm (334 by I in.); outside dimensions approximately 120 by 31 mm (5¾ by 2 in.).
7. Sampling
7.1 The lest sample shall consist of a factory-sealed can of compound (minimum contents. 450 mL or I p1) with an appropriate curing agent where applicable, or a standard cariridge. factory tilled and sealed.
8. Procedure (see Hg. 1)
8.1 Thoroughly clean the templates and rectangular plates with methyl ethyl kctonc. xylcnc, or similar solvent. (Warning—Methyl ethyl ketone, xylene, and similar solents are both toxic and ulaminable and should be handled with caution in a well ventilated hood.)
8.2 Condition the sample of sealant in the original closed container tbr 24 h at 23 ± 2°C (73.4 ± 3.6°F) and 50 ± 5 % relative humidity. For single-component scalants, weigh out approximately 250 g of the sealant before testing. For multi- component sealants, thoroughly mix 250 g of the base compound with the appropriate amount of curing agent following the manufacturer’s mixing instructions.
8.3 Prepare at least two specimens for each sealant as follows: Center the template on the metal plate and caretuilly fill it with sealant avoiding air pockets. Strike oil the surface flat using a metal straightedge. to a uniform thickness.
8,4 Relative i,ck-hre Thne Unknown. lithe relative tack- free time is unknown, the procedure is to pretest one of the test specimens by lightly touching the surface of the sealant with a film of polyethylene wrapped over the end of a finger. Touch the test piece in accordance with an appropriate time interval described in 8.5. Try to touch a difierent place on the surface each time. After the polyethylene wrapped fingcr is lightly touched to the surface of the sealant, it is immediately removed and examined to see if sealant was picked up on the polyethylene film. When no sealant is pickcd up on the polyethylene strip, perform the next tcst as described in 8.6.
8.5 lime intervals—If the relative tack-free time is unknown. the procedure is to pretest. as in 8.4. one test specimen each minute for the first 10 mm. each 2 mm for the next 10 mm. each 5 mm for the next 160 mm (3 h has elapsed), each hour for the next 69 h. each day until a positive result is achieved or until 21 days has elapsed. Table I summariies the time intervals.
Note 4—lnfurmaüon provided by the manufacturer can sase a great deal of time and lead the tester quickly to an apjwnpriatc time bracket.
8.6 After the pretest in 8.4 do the actual test by starting new. hut just before the tack-free lime estimated by the pretest. At the appropriate time lay a polyethylene strip over half of the same test specimen and gently place the brass weight on the strip and allow it to remain there for 30 s.