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October 22, 2021 - Building & Construction

Structural Adhesives in Garage Door Assembly

According to IBISWorld, U.S. garage door manufacturing is a $4 billion market that has seen significant growth as the economy recovers. Fueled by new residential and commercial construction as well as remodeling projects, this market is expected to continue to grow.

In an effort to bond foam to metal, build garage doors that can maintain strength in changing temperatures and increase production line efficiency, garage door manufacturers are turning to adhesives. Let’s take a closer look at types of structural adhesives and the role they play in garage door assembly.

What are Structural Adhesives?

Structural adhesives are adhesives that generate their strength from chemical crosslinking. These thermosets become stronger through chemical reactions with either moisture in the air or with a second added component.

The high strength generated through these chemical reactions allows the adhesive to handle high tensile and shear stresses, causing adhesives to potentially replace mechanical fasteners.

Type 1: Hot Melt Polyurethane Adhesives (HMPURs)

HMPURs are used in the following garage door assembly application methods:

  • Flat panel lamination
    • FRP(fiber reinforced plastic) to foam
    • Metal bonding/lamination
    • Other structural bonding exposed to the elements

These structural adhesives offer strengths up to 3,000 psi and elongation up to 500%. Additionally, HMPURs provide as high as 400°F heat resistance and down to -40°F cold resistance. They can be applied in garage door assembly using roll coating, swirl spray and extrusion methods.

Bostik offers smart HMPURs for garage door assembly. Two in particular that can both be roll coated include:

  • SG1578-164: This HMPUR offers excellent green strength and quick tack. In additional to superior creep resistance, the product also has a long open and good adhesion to a variety of substrates including steel, wood, fiberboard, polyurethane foam and most plastics.
  • SG9621: This solvent-free, quick-setting product offers low application temperature and good green strength. It has excellent chemical and elevated heat resistance as well as superior adhesion to wood, steel and a variety of plastics.

Type 2: Silyl-Modified Polymers (SMP)

SMPs are a hybrid of silicone and urethane chemistries. Silicone and isocyanate free, SMPs are used in the following garage door assembly applications:

  • Structural panel bonding
  • Expansion joint sealing
  • Window bonding
  • Metal-to-metal bonding

Some of the benefits SMP offers are:

  • Primerless adhesion to a variety of substrates including:
    • Glass
    • Vinyl
    • Fiberglass
    • Painted steel/aluminum
  • Moisture curing chemistry
  • Great shear/tensile strength
  • Excellent paintability

SMP adhesives are applied to garage doors using a hand caulked/extruded method or mechanically pumped from pails or drums.

Bostik’s SMP adhesive products for garage door assembly include:

  • STR350A: Isocyanate and PVC-free, STR350A has very good UV resistance and aging properties. This product has odorless curing and adheres well without a primer a variety of substrates such as powder coated metal, most lacquered metal surfaces, lacquered wood and glass.
  • STR360A: Designed for panel assembly, this product has great UV resistance and aging properties. It has high green strength immediately after installation and a 30-minute open time, allowing for flexibility in manufacturing processes.

Type 3: Silicone and Urethane Adhesive Sealants 

Silicone and urethane adhesive sealants are used in the following garage door assembly application methods:

  • Some panel bonding
  • Expansion joint sealing
  • Sealing of windows and other inserts
  • General waterproofing

Silicone sealants offer the following benefits:

  • Great UV resistance
  • Can be clear in color
  • Low VOC
  • Quick cure
  • Good low temperature gunnability

Urethane sealants also offer benefits for garage door assembly:

  • Good history of sealing/elastic bonding performance
  • Highest strengths at break for sealants
  • Good paintability
  • Great adhesion to tough substrates

These sealants can be applied using a hand caulked/extruded method or mechanically pumped from pails or drums.

Bostik manufactures smart silicone and urethane sealants. Some products in particular include:

  • Pro MS 50: This silicone sealant offers long lasting elastomeric qualities for building envelop applications. With adhesion to Kynar® resin-based coatings, aluminum and other common building materials, this product also does not yellow in UV light and is asphalt compatible with self-adhered flexible flashings and wraps.
  • 915 FS: This fast setting urethane adhesive sealant is capable of dynamic joint movement totaling 70% of original joint geometry (+/- 35%). Its fast skin time enables a quicker top coat. Additionally, this product has adhesion to Kynar resin-based coatings and a best-in-class warranty.

Type 4: Epoxies 

Epoxy structural adhesives are typically used in the following garage door assembly applications:

  • Panel bonding
  • Metal-to-metal bonding
  • Clip/hinge bonding
  • Skin to core lamination

These structural adhesives offer the following benefits:

  • Great chemical and temperature resistance
  • Short, medium and long open times
  • Can be cured using heat
  • Bonds well to low surface energy substrates
  • High shear strength performance

Common application methods for epoxy structural adhesives include:

  • Hand roll-coating/brush: pre-mix A and B components to activate curing prior to coating/brushing the substrates
  • Bead: closed system, hand apply, drum or pail un-loader with static mixing nozzle

Bostik’s epoxy products included 7575, which typically has a 5-minute cure time, and 7538, which cures in 30 minutes.

Type 5: Elastosols

Elastosols are used in structural panel bonding and metal-to-metal bonding garage door assembly applications. These adhesives offer the following benefits:

  • High viscosity paste at room temperature
  • Low modulus, anti-flutter material
  • Adheres to a wide range of metal substrates
  • Can be overpainted with oil, cellulose or stoving-based paints
  • Excellent chemical resistance
  • 450 psi bond strength

Elastosols can be applied using a hand caulked/extruded method or mechanically pumped with heated inductor plate for pails or drums.

Bostik’s elastosol products include M91 and M83.

To compare all structural adhesives for garage door assembly, please consult this chart:

For more information on how Bostik’s structural adhesives for garage door assembly can help with your project, contact a Bostik repesentative.

Other content relevant to this topic:

Non-Structural Adhesives Used in Garage Door Assembly

The Growing Popularity of Fiberglass Garage Doors, Adhesives for Them

Structural Insulated Panels (SIPS) in Construction

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