Friction Adhesive

Bonding surfaces must be free of moisture, oils, dirt and other contaminates. Typical cleaning processes include aqueous alkaline cleaners, solvent vapor cleaners, or burning or baking contaminates off of the surface. After cleaning, a surface preparation process like phosphating, grit blasting or wheel abrading will enhance the adhesive bond. Reliobond^® 1706 adhesive will bond very well to a clean, bare metal surface, but preparing the surface with one of these methods will improve the consistency and overall strength of the bond.

Reliobond 1706 should be thoroughly mixed before application. Mix the product using an air mixer with high shear mixing blade, pail tumbler or drum roller for 30 minutes to 1 hour. Reliobond 1706 can be reduced to a desired viscosity/solids by using methyl ethyl ketone, acetone, n-butyl acetate, methyl acetate or t-butyl acetate in any proportion. Toluene, xylene and alcohols can be used in small amounts but will destabilize the product if too much is added.

Reliobond 1706 adhesive can be applied to the friction material or metal surface. Experimentation is necessary to determine the optimum adhesive thickness and coating pattern for each part design.

For friction paper applications the adhesive is usually roll coated or curtain coated onto the substrate. For clutch or transmission parts, a dry film thickness of 0.5-1.5 mils is a recommended starting range. The optimum film thickness allows for full wetting of adhesive onto the metal surface during cure but does not squeeze out of the bond line or penetrate too deeply into the friction paper. If Reliobond 1706 adhesive consistently penetrates too deeply into the friction material regardless of coating thickness, try Reliobond 5007 which flows very little during cure and is designed to minimize penetration into low density friction paper.

DRYING
Reliobond 1706 must be fully dried before curing. Residual solvent in the adhesive can cause a weak, “spongy”, “blown” bond. It is difficult to recommend exact drying parameters. Environmental conditions, coating thickness, and drying equipment type all significantly affect dry time. Here are some general guidelines for drying:

• Drying oven temperatures can range from 100°F-250°F (38-121°C). Do not exceed 250°F (121°C) as higher temperatures can prematurely cure the adhesive or cause blistering of the adhesive film.
• Air flow in the drying oven is crucial to achieving fast dry times. More air flow will reduce dry time.
• Contact Ruscoe Technical Service for a test procedure to determine if your part is fully dried.

CURING
The phenolic resins in Reliobond 1706 generate water vapor during cure. This water vapor must be forced out of the adhesive using pressure during the cure cycle. Most bonding problems with this type of adhesive are related to inadequate or uneven pressure. At least 100 psi must be continuously and uniformly applied during the curing process to ensure a good bond.

Reliobond 1706 adhesive will cure in the temperature range of 300-450°F (148-232°C). Keep in mind that this is the temperature that the adhesive must reach, not the oven setting. The adhesive will take longer to cure at lower temperatures but will allow more time for water vapor to escape and for adhesive to flow and wet the metal surface. Curing at too high of a temperature can cause the adhesive to gel quickly which will trap water vapor in the adhesive and cause a weak bond. Experimentation is required to determine the optimum cure cycle for each part design. A good starting point is to cure for 30 minutes at 400°F (204°C) at 200 psi.