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Keeping It All Together with Adhesives and Fasteners

August 13, 2007

9 Min Read
Keeping It All Together with Adhesives and Fasteners

Adhesives and other fasteners are among the unsung heroes in most products, providing high reliability and keeping size down. In everything from cell phones to race cars, adhesives help keep weight and volume down while bonding products that withstand being bounced around. In larger products where the permanence of adhesives isn't always beneficial, fasteners like nuts and bolts continue to evolve, making engineers' lives easier.

Rugged Adhesive Holds Racer Together

The MP4-22 Loctite 246 adhesive from Henkel is currently used on the Vodafone McLaren Mercedes MP4-22 race car. The adhesive is used in 12 applications as varied as brake pads, driveshaft and the rear wing assembly. Loctite 246 lets the racing team secure components with an adhesive that withstands extreme conditions yet still disassembles easily while permitting re-use of components. Engineers can replace parts easily using standard hand tools during a race weekend or test session. When the instant adhesive bonds plastic parts to the model's rear wing, the low viscosity material quickly wicks between the parts, leaving no excess residue that would affect the airflow during testing.

Adhesive Doubles as Potting Material

Henkel Corp.'s Loctite Indigo Visible Light Cure Adhesives cure in seconds upon exposure to light in the visible spectrum. Loctite 3552 and 3553 are suitable for industrial and medical device assembly They can also be used for potting applications that require rapid cure to depths of 13 mm.

Loctite 3552 is a low viscosity (200 cP) formulation, while Loctite 3553 I is a medium viscosity (3,500 cP) adhesive. Both clear acrylic adhesives offer fluorescence for easy quality control inspection. They are suitable for bonding polycarbonate and other thermoplastics without causing stress cracking.

The adhesives perform optimally when cured with the Loctite Indigo CureJet LED system, which emits no UV light and requires no venting or specialized protective equipment.

3M™ VHB™ Structural Glazing Tapes

3M™ VHB™ Structural Glazing Tape has been proven in thousands of international buildings since 1990 as an alternative to structural silicone and spacer tape for glazing in curtain walls. It is specially formulated to permanently bond glass to metal frames in interior and exterior curtain walls. 3M Tapes feature immediate handling strength for increased productivity with no curing time, no liquid mess and less waste. Viscoelasticity absorbs shock and allows movement for reliability against wind, vibration and thermal expansion/contraction. Clean edges and consistent color provide eye appeal from a distance and even up close from the inside out.

Metal Adhesives Don't Sag

Plexus Metal Bonder Adhesives provide a blend of high strength, fatigue endurance, impact resistance and toughness on metals including stainless steel and aluminum, as well as thermoplastics and composites. The two-part methacrylate adhesives are non-sagging gels developed for rugged metal bonding applications like bus and coach, marine, heavy truck and specialty vehicle manufacturing. They don't need primers or much surface preparation on most substrates.

Packaged in ready-to-use cartridges, pails and drums, they offer 12-mil solid glass bead spacers for bond gap thickness control. They can also be applied in bulk using Plexus FusionMate or other meter-mix dispensing systems. The working time of Plexus MA830 is 4 - 6 min, with a fixture time of 20 - 25 min. It cures at room temperature to a tensile strength of 3,200 - 3,800 psi. Plexus MA832's working time is 14 min and its tensile strength is 3,500 - 4,000 psi.

Epoxy Cures at Ambient Temperatures

Polymer System EP40 is a two component epoxy resin compound from Master Bond that's designed for bonding, sealing and casting engineering metals and plastics that feature high shear and peel strength. It's been formulated to cure readily at ambient or more quickly at elevated temperatures with a non-critical 1:1 mix ratio by weight or volume. EP40 augments the strength properties of epoxy resins with flexibility and peel strength characteristics. It also has resistance to thermal cycling and mechanical vibration and shock, along with high electrical insulation properties. It bonds with engineering plastics like polycarbonates, acrylics and metals like steel and aluminum. Steel and aluminum bonds have shear strength values as high as 1,800 and 1,500 psi. Service temperatures range from -100 to +230F.

Light-Cured Adhesives Bond and Protect

Light-cured Tru-Bond Series adhesives from Devcon cure in seconds when exposed to ultraviolet light, either direct sunlight or UV lamps. It instantly bonds or coats glass, aluminum, steel, ceramics, plastics and other dissimilar substrates. Bonds are flexible and withstand service temperatures from 65 to 225F.

Tru-Bond 18100 provides three viscosities from 205 to 75,000 cps for use with glass, metal and ceramic bonding. Tru-Bond 18200 Plastic Bonder Series adhesives form permanent impact-resistant bonds that are flexible, with 450 percent elongation. They can also create a mar-resistant surface for plastics. Tru-Bond 18300 is thick (2240 cps) for adding decorative “dome coatings” to decals mounted on metal or glass. Tru-Bond 18305 is less viscous (750 cps) and is ideal for creating thin coatings (0.1 - 0.5 mil) on thin, flexible substrates such as polycarbonate sheets.

Clear Adhesive Targeted at Displays

MasterSil 415 is a versatile one component silicone elastomer compound that can be used for bonding, sealing and coating. The transparent formulation from Master Bond Inc. is particularly suited to optical and display applications. It cures at ambient temperatures to a flexible, rubbery solid. It has a paste consistency and can be applied on vertical surfaces without sagging or running.

Its set-up time is 8 to 12 min at 75F. The adhesive provides electrical insulation, with a dielectric strength of 500 V/mil for a 1/8 inch thick test specimen. Shore A hardness is 30, elongation at 75F of 400 and tensile strength is 325 psi. Its service temperature range of from -185 to +400F.

New PUR Adhesive System from 3M Features Longer Open Time

The Scotch-Weld™ Polyurethane Reactive (PUR) Easy 250 Adhesive System from 3M puts powerful dual-production capability in the hands of assembly operators; production benefits of hot melt technology with the performance benefits of structural adhesive technology. The hand-held, self-contained system dispenses adhesive at 250F with the squeeze of a trigger. The higher application temperature allows a longer open time for production flexibility.

The electrically heated, pneumatic applicator is easy to use and maintain with disposable nozzle, no tip cap, no grease and no system purging. Adhesive can stay in the applicator at dispensing temperature for up to 16 hours. An optional dual temperature pre-heater keeps cartridges ready to use.

The new system has a choice of five 3M adhesives with a range of properties including adhesion in difficult-to-bond jobs such as hardwood miter corners. Use for bonding wood, plastics, metal, glass and many surface combinations.

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