ASTM D6325 Test for Open Assembly Time of Carpet Mastic Adhesives

Scope:

Standard method ASTM D6325 describes the procedure to determine the open assembly time for a trowelled carpet adhesive. It is important that sufficient assembly time should be available to an installer to prepare and place the carpet sections for bonding onto the substrate. An adhesive with too short an open assembly time will not allow the installer to place the carpet before it completely dries out. Conversely, if the open assembly time is too long, then the adhesive will still be wet and cause movement of the carpet after placement, besides affecting the bond strength. The ASTM D6325 test can aid the adhesive manufacturer and the carpet installer to select the appropriate adhesive for the application.

It is stated in ASTM D6325 that the test method is modeled upon ASTM C679 (test for tack free time of elastomeric sealants). The ASTM D6325 variations relate to substrate, adhesive, the use of rigid LDPE pieces to test the tackiness, the time intervals, and the use of 1 kg deadweight.

Procedure:

Test specimens, as specified in Section-8 of ASTM D6325 are marked for identification. They are then heat-aged at 140 ±5 ℉ for seven days, followed by exposure to UVA light for 48 hours. Thereafter, comparative color measurements between test and control specimens are performed, using a colorimeter or spectrophotometer. The reflectance values measured by the instrument are converted to the CIELAB color scale by computation.

Video 01: ASTM C679 Standard test method for tack-free time of elastomeric sealants

Specimen size:

For ASTM D6325, each LDPE piece will be 2 inches × 2 inches × 0.006 inches.  The glass piece should be 12 inches × 12 inches.

Result:

The ASTM D6325 open assembly time is expressed in minutes. 

Conclusion:

Standard method ASTM D6325 describes the procedure to determine the open assembly time for a trowelled carpet adhesive.