Discussion

For purposes of this evaluation, adhesion data was based on the following number scale; 5 equals cohesive failure, 4 equals partial cohesion, 3 equals strong adhesion but adhesive failure, 2 equals moderate adhe­sion, 1 equals weak adhesion and 0 equals no adhesion, that is, the sealant almost falls off the substrate.

Tables 1-3 show the adhesion results for both one – and two-part urethane sealants and one-part silane curing polyether for the control and with various additive levels and solvent types.

In all cases, the additive did not hurt adhesion, and with several substrates, adhesion was improved. Pictures of actual samples tested are also shown in Figs. 1-3.

Standard cure, two-part urethane control on aluminum joint (left) showing 100 % adhesive failureand

Teflon* is a registered trademark of the DuPont Corporation.!).

TABLE 2—Additive adhesion testing of one-part urethane sealant (dry and 21 days wet).

One-part silane curing polyether control on concrete joint (left) showing 40 % cohesive failure versus 4.0 % additive in MIBK (right) showing 70 % cohesive failure.

The photos reinforce the previous comment that the additive solution does not harm adhesion and may have some improvement.

Additional testing was done to validate the effect of the additive on sealant modulus. Within an optimum range of additive level—that is, 1.7 % in 2EH for one – and two-part urethane sealants, and 4.0 to 6.0 % in MIBK for one-part silane curing polyether sealant—the elongation increased approximately 60 % percent. When the equivalent amount of solvent was used without additive, tensile force was lowered but no resultant increase in elongation was seen. See Figs. 4-6.