Structural Adhesive Film

AF 126 • AF 126 FR

Product Application

(continued)

Primer Application

Priming of bonding surfaces offers two distinct advantages: (1) Priming insures complete

wetting of metal surfaces which normally results in superior environmental and low

temperature properties and (2) Priming simplifies production by protecting cleaned parts

until bonding can be completed. The following system is suggested for spray application.

See separate Product Specification Sheet for 3M™ Scotch-Weld™ Structural Adhesive

Primer EC-2320 before using.

Spray Gun

DeVilbiss JGA

Air Cap

Number 78

Nozzle

AV-15-FX

Needle

FX

Line Pressure

35 psi

2.4 bar

Cup Pressure

1-2 psi

69-138 millibar

Distance from Panel

9 ± 3 inches

23 ± 7.6 cm

Primer Thickness (dry)

0.00005-0.0002 inches

1.3-5.1 micron

If part design permits, parts may be primed by dipping and draining.

Dry Cycle

The following dry cycle for Scotch-Weld EC-2320 is suggested for use with 3M™

Scotch-Weld™ Structural Adhesive Films AF 126.

Air Dry:

Air dry at 75-85°F (24-29.4°C) for a minimum of 30 minutes.

Plus Force Dry:

Circulating air oven with part at 200°F (93.3°C) for 30 minutes.

OR

Alternate Dry:

Air dry at 75-85°F (24-29°C) for a minimum of 2 hours.

Cure Cycle

General Cure Requirements

Time, temperature and pressure determine the final bond properties. These properties

may also be affected by the type of curing equipment used for each specific application.

Curing ovens must be vented to the outdoors. In general, the cure properties of Scotch-

Weld AF 126 are as follows:

Cure Pressure

Pressure is required during cure to keep parts in alignment and to overcome distortion

and thermal expansion in the adherends. When bonding honeycomb sandwiches

utilizing non-perforated core, pressure is required to overcome the thermal expansion of

the air contained in each cell of the honeycomb. Honeycomb sections have been bonded

successfully with Scotch-Weld AF 126 using perforated or non-perforated core under

pressure of 10-25 psi (68.9-172.3 kPa).

Cure Temperature

The cure temperature may be varied from 180 to 350°F (82-177°C) depending upon the

materials being bonded, equipment available and bond properties desired. The film will

soften as temperatures are increased and will wet the surface and fillet the core to which

it has been applied. A chemical cure will be initiated at 180°F (82°C) and a low strength

gel formed. Continued heating chemically converts this gel into a high strength, solvent

resistant bond. Cure temperatures in excess of 350°F (177°C) yield usefully, but lower

than optimum strengths.

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