GW 3-3

Two-Component Batch Mix Urethane Coating Application

Gaco Western two-component, 1:1 ratio urethanes are liquid-applied elastomers. When properly combined and applied, they cure to tough, high-strength rubber membranes. These instructions cover use of standard cure materials. The use of fast cure material is covered in appropriate Spray Guide and Product Data Sheet.

MIXING

1. Observe cautions on the label about frozen components. Examine both Part A and Part B for graininess. If graininess is observed, warm the entire contents of the can to 60°F (16°C) or higher, and mix until smooth.
2. Partial containers of Part B (Iso) cannot be stored longer than one or two days as exposure to atmospheric moisture induces cure. When repackaged into smaller containers with minimal exposure to air, leftover Part B (Iso) may be usable for up to several weeks. Keep Part B (Iso) containers covered whenever possible.
3. All GacoFlex urethanes contain color pigment in the Part A (Polyol). Mix Part A (Polyol) to suspend pigment prior to mixing equal volumes of Part A (Polyol) and Part B (Iso). UB-64 Series Part B contains a small amount of pigment which also requires mixing prior to use. Stir thoroughly for five minutes, scraping sides of container. Quantities larger than two gallons (7 liters) must be power mixed. Best results are obtained by pouring Part A (Polyol) into Part B (Iso) while mixing. Polyethylene or polypropylene mixing containers are recommended as they can be re-used. Set up material is easily stripped out cleanly the following day. Other GacoFlex fast set urethanes use the same types of equipment. Refer to the individual spray guides for these fast set urethanes.

APPLICATION OF BASE COAT

1. After priming as required and installing tape, including coating where required, apply overall base coating of Gaco Western urethane in specified coverage. All specified quantities are on an undiluted basis. Better films are usually produced with less entrapped air when the rate of application is no more than 1½ gallons per 100 sq. ft. (6.1 L/10 m²). However, the recommended rate varies by specification. The specified gallons and uniformity of coating are the critical elements of a quality application.
2. GacoFlex urethanes cure rapidly. Cleaning of roller covers and brushes is usually impractical. Workers should have extra roller covers and brushes on hand.
3. Apply GacoFlex urethane in uniform thickness without skips or holidays. Standard cure or batch mix base coats can be rolled or sprayed, depending on job type and size. See separate instructions for spray equipment recommendations. Allow each coat to dry until tack free and sufficiently cured for foot traffic before applying additional urethane coating. Between 2–24 hours may be required depending on drying conditions, temperatures, and the particular product.
4. Gaco Western specifications recommend alternating colors, where possible, between multiple coats to maintain quality control on the job.
5. Extend each coat over cants and up vertical surfaces of pads, curbs, walls and parapets. The top of curbs and equipment pads shall be similarly coated. In the case of walls and parapets, extend coating to the point where counterflashings enter the masonry. Where no counterflashing is specified, hold the base coats just short of the termination line at edge of deck to avoid seeping under masking tape or spilling on adjacent unprotected surfaces.
6. If the entire job cannot be carried through to completion without interruption, the interruption should occur after the first coat. This will provide protection for the tape system and the general roofing area.

Be aware of the recoating windows for each product. UB-64 has the shortest at 7 days. U-66 can be left up to 90 days. If left longer than the recoat window priming with U-5677 is required.

Coated surfaces must be clean and dry before work resumes. The preferred method cleaning is to wash with liquid detergent and water and follow with a thorough rinse. An alternative method is to lightly solvent wipe, using extreme care to avoid lifting or wrinkling.

COLD WEATHER APPLICATION

During cold weather, special precautions must be taken in applying two-component urethanes. These coatings should not be applied to surfaces 40°F (4°C) or colder. Store materials above 65°F (18°C) prior to use. Mix together thoroughly then allow the mix to stand for a 15 minute pre-reaction time to provide better cross-linking. After this 15 minute period, thickening may occur which can be reduced by thinning with up to 15% with GacoFlex T-5130 or as per label. Pre-reaction time for UB-6407 should be reduced to 10 minutes maximum. An accelerator, U-5651, is available to increase cure rate.

One half ounce of U-5651 accelerator per gallon of combined Part A (Polyol) and Part B (Iso) will increase cure rate as follows:

• U-66 by 75%
• UA-60 by 100%
• UA-65 by 100%
• UB-6407 by 500%

This is the maximum amount acceptable, adding more accelerator may decrease physical properties.

HOT WEATHER APPLICATION

Product data on pot life and cure rate are provided for materials at 70°F (21°C). At temperatures above 70°F, (21°C) pot life and cure time will decrease proportionately as temperature increases. Store materials out of direct sun and mix only the amount that can be applied within the pot life. Refer to the Product Data Sheet for the particular GacoFlex urethane coating for details.

APPLICATION OF TOP COATS

• Apply urethane top coat or trowel coat the next day, after the base coat, if possible. (Note: See paragraph 2.6 in reference to interruptions.) UA-60 Series coatings are not suitable for trowel application. If used as a top coat directly over texture it will take two coats to adequately seal the texture.
• Inspect for damage prior to the application to top coat. Any surface damage must be repaired by re-flashing, re-taping and replacing of base coat so that a continuous membrane in substantially uniform thickness covers the entire surface prior to top coat application.
• While careful color matching procedures are used, different batches of urethane may vary slightly in hue. This variation will be too slight to be perceptible if changes are made at natural breaks in the surface. Inter-mixing of batches may be necessary or desirable to assure consistency in top coat color.

CAUTION: Excessively heavy applications of urethane (greater than 40 mils (1 mm) wet or greater than 16 mils (.4 mm) wet for UA-60) can cause pigment separation during drying, resulting in a blotched color. Uniform application at the specific coverage is important to provide proper results. Excessively heavy applications may cause additional problems.

• Remove masking tape at edges of coating area as soon as the final coat of urethane is applied. By removing the tape while the coating is wet, it will not be necessary to cut it off to avoid damage to the edge of the coating. Any seepage under the tape on rough surfaces can be wiped off with thinner while wet.