On the overwrap seam of a thermal-acoustic insulation blanket in a pressurized airframe, Saint-Gobain CHR 26020 is used where the repair drawing allows a foil-faced acrylic pressure-sensitive adhesive closure tape. The aluminum foil backing is dead-soft enough to follow blanket corner radii without cracking, but the foil is not a fire barrier on its own. The tape must be evaluated as part of the complete blanket assembly under FAR 25.853(a) because the aluminum face reflects heat and can delay ignition of the underlying insulation resin. Peel adhesion to stainless steel is checked by ASTM D3330 Method A as an incoming material control. Static shear at 70 °C is a more operationally relevant metric than ambient shear because the crown skin temperature can rise during climb and cruise. The adhesive must be applied to a clean, dry foil substrate; hand burnishing with a 75 durometer rubber roller is the minimum required for full contact. Installation below 10 °C reduces wet-out and increases edge-lift risk. The acrylic adhesive system should not be exposed to phosphate ester hydraulic fluid or jet fuel without a compatibility coupon test; acrylic PSA can soften at the bond line and lose overlap shear. Published data for this specific configuration is limited; therefore qualification on the actual insulation stack is mandatory before release to line maintenance. The tape should be stored at 21 °C ± 2 °C and 50% ± 10% RH for 24 h before application to reduce handling-induced curl.

Why Does Duct-Board Sealing Demand a Different Acrylic Wet-Out Than Metal Duct Joints?

Rigid fibrous glass duct board presents a highly open, non-homogeneous surface that prevents an acrylic pressure-sensitive adhesive from building full contact area on raw fiberglass. CHR 26020 is therefore placed over the reinforced foil/kraft facing of the duct board, not over the cut fibrous edges. The objective is continuous adhesive contact across the scrim weave, because the acrylic polymer has limited cold flow at ambient temperature and will not completely fill deep voids in the board. Surface dust from field-cut duct board is a primary cause of peel loss; the foil facing must be wiped with anhydrous isopropyl alcohol and allowed to dry before tape application. A 2 in hard rubber J-roller is used to burnish the tape into the facing. Under UL 181A/UL 181B closure-system requirements, the tape is accepted only as part of a listed assembly; it is not a standalone listed product. Aluminum foil backing contributes a low water vapor permeance to the seam if the foil is not perforated, but any fold pinhole becomes a vapor path. Creep behavior of the acrylic bond above 70 °C makes adhesive-only closure unsuitable on high-pressure duct sections unless mechanical fasteners or supplementary support are part of the listed detail. Peel adhesion to galvanized steel is not representative of adhesion to foil-faced duct board; qualification must be done on actual duct board factory samples. Minimum overlap for unlisted applications should not be less than 50 mm on rectangular ducts.

When a Vapor-Control Layer Is Taped on the Warm Side of a Refrigeration Enclosure

On the warm side of a cold-storage wall panel, CHR 26020 is placed over polyisocyanurate insulation facer joints to restrict water vapor ingress from the ambient side. The aluminum foil backing is the dominant vapor retarder in this configuration; the acrylic adhesive itself is not a substitute for a continuous foil layer. The vapor pressure differential across the joint can exceed 2 kPa in tropical ambient conditions, and any pinhole introduced by creasing becomes a condensation site within the panel. Peel adhesion to the panel facer is measured by ASTM D3330 Method A on the actual facer material, because values obtained on stainless steel do not predict wet-out on polyethylene or polypropylene-rich facers. The facer should have a surface energy of at least 38 dyn/cm; low-energy facers require corona treatment or a compatible primer. Application should occur at panel temperatures between 10 °C and 40 °C to prevent condensation and to retain adhesive flow. A 2 in rubber roller is used to set the tape, and a minimum overlap of 50 mm beyond the joint centerline is required. Damp-heat aging at 85 °C and 85% RH for 500 h is an appropriate screening test for cold chain enclosures. Published data for CHR 26020 in this specific refrigeration panel configuration is limited; panel-level qualification is necessary.

In an appliance assembly line for residential laundry and dishwashing cabinets, CHR 26020 is used to anchor reflective insulation pads to the cold side of galvanized steel cabinet wrappers. The steel surface is first cleaned with a blend of aliphatic hydrocarbons to remove drawing oil. Acrylic adhesive performs more consistently than natural rubber PSA on galvanized steel after repeated thermal cycling at moderate cabinet temperatures. The tape should not be placed within 25 mm of a resistive heater housing because localized surface temperatures above 120 °C cause adhesive softening and foil delamination. A pneumatically actuated silicone roller applies uniform pressure and removes trapped air. Initial peel adhesion is checked by ASTM D3330 Method B after 7 days at 23 °C. Heat aging at 90 °C for 168 h should not reduce peel strength by more than 50% on a clean galvanized substrate if the joint is shaded from direct heater line-of-sight. The aluminum foil backing reflects radiant heat in warm-air discharge zones, but it is not a fire barrier and must not be used as the sole protection around heater boxes. Plasticized PVC harness contact is a known issue; acrylic adhesive is less susceptible to plasticizer migration than natural rubber PSA, but long-term contact should be checked by accelerated aging. Published data for this specific configuration is limited.

Marine Exhaust Lagging Hold-Down Without Continuous Compression

On a marine diesel exhaust lagging section, CHR 26020 is used as a positioning closure over needle-punched E-glass or mineral wool lagging during installation. The lagging thickness is designed to keep the outer surface below 120 °C, and the tape is placed only on that outer lagging surface. The acrylic pressure-sensitive adhesive retains sufficient short-term shear at 90 °C for assembly, but it is not a continuous high-temperature structural adhesive. A stainless steel band clamp must be installed over the taped overlap before the engine returns to service. Salt spray and condensation can undercut the adhesive edges; a 1,000 h ASTM B117 salt-spray exposure followed by ASTM D3330 peel comparison is a valid screening method for engine-room conditions. The aluminum foil backing should not be left in direct contact with uncoated stainless steel under wet conditions because galvanic potential may promote aluminum pitting. A protective lagging cloth, aluminum coating system, or inert separation layer must be used in wet engine-room spaces. The tape is not a fire barrier and must not be the only outer cover over lagging in spaces subject to marine classification society fire testing. Published data for CHR 26020 under marine classification society approval is limited.

Automotive Underfloor Heat-Shield Edges Are Not Exhaust-Facing Application Points

The exhaust-facing surface of an automotive underfloor heat shield can exceed 150 °C under load; an acrylic pressure-sensitive adhesive on CHR 26020 will soften at that condition and the aluminum foil will delaminate from the glass fiber core. The tape is therefore restricted to the cabin-side surface or the foil edge fold on prototype and field-repair heat shields. The cabin-side fastening plane should be kept below 90 °C in continuous operation. The tape may be used as an assembly aid or edge seal, but it does not replace mechanical clinching, spot welding, or hemming on heat shields. The adhesive bond to glass fiber mat is poor; the tape must contact the aluminum face sheet rather than the bare mat. Thermal shock cycling between -40 °C and 85 °C per ISO 16750-4 class 1 is an appropriate test for cabin-side attachment. Peel adhesion per ASTM D3330 after fuel splash exposure with the actual underbody fluid set is required; the acrylic adhesive has limited resistance to aromatic solvents and must be protected from direct contact with aggressive underbody waxes. Published data for this specific configuration is limited; validation must be conducted on the actual heat-shield laminate and floorpan geometry.