This high strength adhesive system provides excellent shear strength properties. The adhesive has the capability of providing excellent adhesion to high surface energy substrates such as metals, glass, polycarbonate, and acrylic. When adhesion is required on low surface energy substrates (such as powder coated paints, polypropylene, and polyethylene), acrylic-based adhesive systems do not perform as well as rubber-based adhesives.

R-25 (Synthetic Rubber) — Used in the construction of SJ-5200, SJ-6100, and SJ-6300 series molded Bumpon products. The adhesive thickness is 2 mils (0.002 inches)

This very high tack adhesive system provides excellent initial adhesion and has the capability of providing excellent adhesion to a wide variety of substrates, including many low surface energy substrates such as powder coated paints, polypropylene, and polyethylene.

R-30 (Natural Rubber) — Used in the construction of SJ-5000, SJ-5500, and SJ-5700 series molded Bumpon products. The adhesive thickness is 2 mils (0.002 inches)

This high tack adhesive system provides excellent initial adhesion and has the capability of providing excellent adhesion to a wide variety of substrates, including many low surface energy substrates such as powder coated paints, polypropylene, and polyethylene

Note: See Relative Adhesive Performance Characteristics for further performance differences between the A-20, R-25, and R-30 adhesive systems.

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Adhesives for Low and High Energy Substrates

Adhesion is the result of the molecular attraction between unlike materials, similar to a magnetic force. The strength of attraction is determined by the surface energy of the material. The higher the surface energy, the greater the molecular attraction. The lower the surface energy, the weaker the attractive forces. Greater molecular attraction results in increased interfacial contact between the adhesive and the substrate. In other words, on a high surface energy material (substrate) the adhesive can flow or "wet out" to assure a stronger bond.

Consider an automobile that has not been waxed for years. When water contacts the surface it spreads in large puddles. This demonstrates high surface energy; the molecular attraction allows the water to flow. In comparison, on a freshly washed car, the water will bead up into small spheres. This is an example of low surface energy; the liquid (or adhesive) does not flow out.

Examples of low surface energy substrates are powder-coated paints, polyethylene, or polypropylene.

When bonding Bumpon products to low surface energy substrates rubber-based adhesives (R-25 and R-30) are recommended.

Application Considerations
To obtain maximum adhesion, surfaces must be unified, dry, and free of contaminates. Surface contact is essential to adhesive performance. To maximize contact on a substrate:

• Clean surfaces with a low strength solvent such as isopropyl alcohol (rubbing alcohol) or heptane (be sure to follow the manufacturer’s precautions and directions for use when using solvents).

• Apply firm pressure to help increase cold flow and contact of the adhesive with the substrate.

• Allow time (dwell) to increase the surface contact and adhesion. Please note that acrylic based adhesives require a much longer dwell time versus rubber based adhesives (see illustrations below).

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Application Pressure
Since Bumpon products are PSA (pressure sensitive adhesive) bumpers, the products do require pressure in order for the adhesive to bond to a given substrate. A pressure of approximately 25 psi (lbs per square inch) is adequate for most Bumpon products in typical applications. Given this pressure, a force of 5 lbs for a 0.5 inch diameter product, e.g., SJ-5012, provides adequate bonding pressure.

Application Temperature
Recommend application temperature is 40°-125°F. Ideally, application should be completed at 60°-80°F.

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Dimension Tolerances
Unless specified, the dimension tolerance (height, width, and length) of molded Bumpon products is ± 0.020 inches.

Environmental Exposure
Bumpon products are intended for interior applications where physical properties will remain unchanged. When exposed to UV light for extended periods some slight discoloration may occur.

Bumpon products may be used in outdoor applications in protected areas with some discoloration possible. Colored Bumpon products may chalk. Simultaneous exposure to high temperatures and humidity may degrade (soften) the Bumpon product urethane.

Load Tolerances
Laboratory testing has confirmed that the shape of the Bumpon Protective Product makes a significant difference in its load bearing performance. See Load Tolerances (12 KB) for more details.

Relative Adhesive Performance Characteristics
The following table provides relative adhesive performance characteristics of the adhesive systems used in the construction of molded Bumpon products.

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Service Temperature
The service temperature for Bumpon products is as follows:

• -30°F (-34°C) to 150°F (66°C)
• 225°F (107°C) intermittent exposure

Shelf Life
The shelf life is 18 months form the date of manufacture when stored in original cartons at 60°-80°F (15°-27°C) and 40-50% relative humidity.

UL Flammability Recognition
Most Bumpon products are currently recognized by Underwriters Laboratories for passing UL 94HB flammability test requirements (UL File Number E116693). See our Technical Bulletin #1548 (40 KB).