A melamine type additive supplied by The C. P. Hall Company (Chicago, Illinois) was added at levels ranging from 0.3 to 6.0 % solids in solution to various sealants including a one – and two-part urethane sealant, and a one-part silane curing polyether sealant.
Solution concentrations were maintained at 85 % solids and 15 % solvent; solvent types included 2-ethylhexanol (2EH) and Methyl isobutyl ketone (MIBK). The study looked at changes in sealant physical properties and changes in substrate adhesion. Physical property testing included sealant resilience as measured with a plastometer, and the sealant stress/strain relationship as measured from stressing typical C 719 (or ISO 9047) configured sealant joints. The adhesion was studied after 21-day cure using the 90 deg peel test done at ambient conditions and then at 7-, 14- and 21-day 50° C water immersions. The peel test was appropriate for this study since it is comparing a product to itself and variations within a given formula.
Manuscript received May 23, 2005; accepted for publication October 20, 2005; published online February 2006. Presented at ASTM Symposium on Durability of Building and Construction Sealants and Adhesives, Second Symposium on 15-16 June 2005 in Reno, NV; A. T. Wolf, Guest Editor.
President of Klosowski Scientific Inc., Chief Chemist—Engineering Diagnostics Inc., FASTM, Retired Senior Scientist, Dow Coming Corporation, Klosowski Scientific Inc., 3031 State Street Rd„ Bay City, Michigan 48706.
" President, The Performance Strategy Group, www. performancestrategygroup. com, Registered Professional Engineer, Certified New Product Development Professional, John E. Plott, PE LLC, 6000 Woodpark Drive, Midland, Ml 48640.
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TABLH 1—Additive adhesion testing of two-part urethane sealant (dry and 9 days wet).
Noie: The resin additive was 85 ‘Z solids, 15 % 2HH solvent. 5=cohesive failure. 4=partial cohesion, 3=strong adhesion but adhesive failure,
2=moderate adhesion, 1 =weak adhesion, ()=no adhesion
For one part sealants, 94 g of sealant was put into the disposable cups that go with the (DAC) 150 mixer and 0.65, 1.7,4.0, 6.0 % additive solution was added. Each time it was mixed in gently by hand, and then mixed for 26 s, the top removed, scrapped down, and mixed again for 26 s. The head space was purged with an inert gas and the container was sealed and left to sit for 24 h to equilibrate. A 10 cc syringe with the bottom removed was used to draw the sealant and inject it into the test joints. The joints had Teflon003 spacers and were 12 mm by 12 mm by 50 mm ( by by 2 in.). Separately, a 3 mm (1/8 in.) thick slab of the same sealant was prepared by tooling the sealant between 3 mm (1/8 in.) spacers to check cure rate and durometer. For each test, a control was made and handled in the same manner.
The two-part sealants were handled in a similar fashion with the additive introduced into the base, allowed to equilibrate for 24 h. The pigment and activator were then added, mixed 12 s, scrapped down, mixed again for 12 s and then placed into joints and into a slab as done with the one part sealants.
The additive in 2EH represented 0.3, 0.65, and 1.7 % of the total sealant formulation; the additive in MIBK represented 4.0, 5.0, and 6.0 % of the sealant formulation. The resin additive was 85 % solids and 15 % solvent in each case. In each set of experiments, a separate experiment was run using 2EH and MIBK in the amount that is present in the additive solution.
No attempt was made to optimize the order of addition, sealant equilibration time or other manufacturing variables.
With each sealant and additive combination, an adhesion study was done on concrete, EPDM, glass, Kynar, PVC, cold rolled steel, anodized aluminum and brass. For this study, the concrete was wiped free of dust; the EPDM was wiped with xylene; the glass cleaned with IPA/water; the Kynar was wiped with MIBK, and the cold rolled steel with toluene. In each case the surface was cleaned twice, using the two-rag method each time, one to wipe it on and the other to wipe it off. These were than coated with approximately j in. thick by 1 in. wide sealant in strips and cured for 21 days. The adhesion was checked by forming a tab and pulling at 90 deg to the surface noting the resistance to the pull and the mode of failure. After the initial check, the samples were put into a 50°C water bath for one week, then checked, then re-immersed and rechecked on a periodic basis (e. g., 9-days wet (two-part urethane), 21-days wet (one – part urethane), 35-days wet (one-part silane curing polyether). These results were then compared to the control (without additive). Tables 1-3 represent the data generated from these experiments with various additive levels and solvent types.