Saint-Gobain COHRlastic 300AR Reinforced Silicone Sponge/Aggressive Acrylic Adhesive Pressure Sensitive Tape is a roll-form closed-cell silicone sponge supplied with an acrylic pressure-sensitive adhesive on one face and protected by a release liner. The product is specified primarily by the COHRlastic 300AR designation, in which the reinforced closed-cell sponge is combined with an aggressive acrylic adhesive rather than a silicone transfer adhesive. Standard roll widths, thicknesses, and liner types are assigned in the manufacturer’s lot database; common manufactured thicknesses for this product family range from 1.6 mm to 12.7 mm. The closed-cell sponge body provides compressibility and recovery, while the internal scrim reinforcement limits tensile strain during handling. The acrylic adhesive is a pressure-sensitive layer whose initial tack and peel characteristics differ from the silicone adhesive systems used on some other silicone sponge tapes.

Because the tape is supplied as a pressure-sensitive roll good, the converting and application sequence differs from that of loose gaskets or liquid-dispensed silicones. No mixing, degassing, or curing is required at the point of use. The installer removes the release liner, places the exposed adhesive face against a cleaned substrate, and applies pressure to wet out the adhesive. The sponge side may be left exposed as a cushion or compressed against a mating flange. In both configurations, the adhesive line is a separate design element with its own service limits.

What separates the reinforced closed-cell form from unreinforced solid, foam, and silicone-adhesive tape products?

The main structural differentiator is the internal reinforcement. In unreinforced closed-cell silicone sponge, tensile loading during roll unwinding or die-cutting can produce permanent elongation and width loss. The 300AR construction uses a scrim reinforcement that constrains this deformation, making the tape more stable in automated gasket placement. The comparative difference is not a change in the silicone chemistry; it is a change in mechanical symmetry. At the same time, the reinforcement reduces the tape’s ability to be stretched into sharply convoluted channels compared with an unreinforced sponge. A solid silicone rubber tape has lower compressibility and much higher closure force; a closed-cell sponge tape is specified where flange force is limited. Polyurethane foam tapes are generally lower in cost but are not suitable for continuous service above approximately 80 °C; the silicone sponge body of the 300AR family can be considered for higher-temperature portions of an assembly, subject to the acrylic adhesive limit. Silicone pressure-sensitive adhesive tapes may provide a bond line that survives higher heat than an acrylic adhesive, but their initial peel to low-energy plastics and some painted surfaces is often lower; the 300AR product uses an aggressive acrylic layer for assembly to those substrates.

For sealing applications in sheet metal enclosures, lighting fixtures, HVAC plenums, and outdoor telecommunications housings, the product is usually specified as a die-cut gasket or as a continuous roll-applied strip. The closed-cell structure minimizes water absorption and provides compression recovery after repeated thermal cycles. On production gasketing lines, the elimination of liquid silicone bead dispensing reduces the need for cold storage and mixing equipment; however, the pressure-sensitive bond must be supported by flange design. If the flange gap varies by more than 0.5 mm along the length of the joint, the gasket must be compressed to its minimum thickness at the tightest point while still maintaining contact at the widest point. Selection of a thicker tape cannot resolve all gap variation because higher compression of closed-cell sponge increases closure force. The manufacturer’s compression-force-deflection curves should be used with actual flange flatness data rather than with nominal flange drawings alone.

Compression set recovery and stress relaxation under flanged load at elevated temperature

When the tape is compressed between two rigid flanges, the gasket force at any given deflection derives from the compression-force-deflection behaviour of the closed-cell silicone foam, not from the acrylic adhesive. For short-term sealing, the adhesive has minimal influence on closure force. Over hours at elevated temperature, the sponge can undergo stress relaxation; closed-cell silicone sponge of this class is designed to retain sufficient recovery to follow flange movement after thermal cycles. Compression set tests commonly apply 25 % deflection and measure recovery after 22 h at 70 °C using ASTM D395 Method B. A representative limit for this product class is 25 % compression set, but lot-specific data from the certificate of analysis controls. The sponge can tolerate excursions that the acrylic bond cannot. Therefore, an accelerated life test must separate adhesive degradation mode from sponge compression set mode.

The acrylic adhesive may soften and allow bond-line slip before the sponge loses sealing force. In thermal cycle studies on enclosure gaskets, adhesive delamination often begins at the edge of a die-cut part where the liner was flexed during removal. A heavier adhesive coat weight can reduce edge flagging but increases adhesive bleed at elevated die-cut temperatures. For assemblies exposed to continuous shear load, the maximum continuous service temperature of the acrylic bond should be treated as 93 °C to 120 °C unless the product data package specifies otherwise. The sponge body is commonly rated from -73 °C to 260 °C. Consequently, specifying a single temperature number for the entire tape is inaccurate; the adhesive and sponge service ranges must be separated in the design file.

Environmental compliance, flammability classification, and outgassing record must be requested from the supplier for the specific stock-keeping unit because liner and adhesive formulations can change. The standard product is generally positioned for industrial and electrical gasketing; however, no blanket statement covers food-contact use, medical use, or vacuum-critical outgassing. For flame resistance, silicone sponge may be classified under UL 94 at specific thicknesses, but the acrylic adhesive can contribute to flame propagation differently. The relevant test report should be matched to the exact thickness and liner configuration. For outgassing, publications for this specific configuration are limited; if a design requires ASTM E595 total mass loss and collected volatile condensable material limits, a dedicated test specimen of the actual laminate should be submitted.

Chemical incompatibility is driven by both the silicone sponge and the acrylic adhesive. The sponge body resists oxidation and many polar fluids but swells or degrades in prolonged contact with strong alkalis, concentrated acids, and some hydrocarbon solvents. The acrylic adhesive is relatively insensitive to water but can be softened by plasticizers migrating from flexible PVC and by certain amines and esters. Bonding to low-surface-energy substrates such as untreated polypropylene or some powder-coated surfaces may require an adhesion promoter or corona/plasma pretreatment. Silicone release liners on the adhesive side are selected to avoid premature adhesive transfer, but storage at temperatures above 32 °C can increase liner release force and lead to slivering during automated liner removal.

The substrate surface temperature at application should be above 15 °C for adequate initial wet-out. Application below 5 °C can reduce tack and produce weak edge bonds. Surface preparation normally consists of drying and removal of oils or dust; solvent wiping with isopropanol is common. Ketone and aromatic solvents should be avoided unless compatibility has been verified, because they can attack the acrylic adhesive and may extract low-molecular-weight siloxane species from the sponge. Roll goods should be stored in original packaging at 15 °C to 25 °C and 40 % to 60 % relative humidity. Moisture absorption by the liner can change its release characteristics. The acrylic adhesive has a shelf life that is normally specified by the manufacturer; aging beyond the stated shelf life can cause cohesive weakening and liner transfer.

When the tape is kiss-cut or slit, tool clearance and liner tension define the process window

On rotary and flatbed converting lines, the reinforced closed-cell sponge cuts cleanly when the blade is sharp and the anvil clearance is set to cut through the foam and adhesive but not the liner. Standard practice is a kiss-cut depth that penetrates to 0.02 mm to 0.05 mm into the liner, leaving enough liner structure for matrix stripping. Because the scrim reinforcement resists deformation, the web can be run at a moderate tension of 0.5 N/mm to 1.0 N/mm of web width. Higher tension can cause the sponge to recover after slitting and alter the cut dimension. If heated tool cutting is used, die temperature should remain below the temperature at which the acrylic adhesive begins to flow. Typical converting lines set the die temperature between 20 °C and 40 °C; acrylic adhesive bleed increases above this range. Use of dry-web cutting or chilled blades below 15 °C can reduce adhesive transfer to tool surfaces, but excessive chilling can embrittle the liner and cause fracture during matrix stripping.

Polyethylene terephthalate film liners of approximately 0.05 mm thickness tolerate the kiss-cut window more repeatably than densified paper liners, which tear when blade penetration exceeds approximately 0.02 mm into the liner. Adhesive buildup on cutting dies is controlled by tool coatings, release sprays, or dry ice de-flashing in special cases. Release sprays must be selected for compatibility with the acrylic adhesive and must not contaminate the silicone sponge surface if the sponge side is later laminated or painted. The scrim reinforcement produces a cleaner cut edge than a non-reinforced sponge at the same thickness, but it also requires higher tool closure force. Cutting presses should be sized accordingly, rather than using the force required for polyurethane foam of equivalent thickness.

In roll-to-roll lamination, the tape can be applied to metal, plastic, or painted coil stock with nip pressure calibrated to avoid crushing the closed-cell foam. Nip pressure is typically held below the point at which the sponge loses more than 10 % of its original thickness as the laminate is formed. Crushing during lamination changes the effective compression range and can create a visible thickness gradient across the roll. The resulting laminate may also show higher peel strength after dwell but lower gasket recovery if the sponge has been permanently set. For that reason, process validation should measure both peel adhesion after 24 h dwell and compression recovery of the laminated part, not the incoming sponge alone.

Because the acrylic adhesive is pressure-sensitive, the bond develops without a curing step. Initial handling strength is available immediately, but full adhesive wet-out to a clean metal surface may require 24 h to 72 h at ambient temperature. Higher substrate surface temperature during application accelerates wet-out, while lower temperature slows polymer chain mobility at the interface. The adhesive is not a structural adhesive and should not be used to carry continuous tensile or cleavage loads without mechanical support. The product is intended for sealing, cushioning, gasketing, and gap-filling functions in which the adhesive is positioned predominantly in compression or low-shear peel.

In direct comparison with other Saint-Gobain COHRlastic silicone sponge tapes, the 300AR designation indicates the presence of the reinforced closed-cell sponge and the aggressive acrylic adhesive combination. The actual certified values for thickness tolerance, density, compression-force-deflection, peel adhesion, and flame classification vary by SKU and should be taken from the manufacturer’s current datasheet or certificate of analysis. Using only a generic industrial description of silicone foam is insufficient for a production specification, because liner type, adhesive coat weight, and reinforcement stiffness can alter converting behaviour and installed performance.