Saint-Gobain CHR SG26-06(R) is a pressure-sensitive tape composed of a woven glass-fiber backing coated with polytetrafluoroethylene and supplied with a silicone adhesive on the opposing face. The product designation identifies a nominal total thickness of 0.006 in (0.152 mm). Roll stock is typically slit from 12.7 mm (0.50 in) to 914 mm (36 in) on 76.2 mm (3 in) internal-diameter cores. The construction is specified for applications requiring a non-porous, low-surface-energy release face together with a pressure-sensitive adhesive that remains serviceable at temperatures where acrylic or rubber adhesives soften. Representative uses include heat-sealing jaw covers, electrical insulation overwraps, composite tooling release layers, and high-temperature masking. Lot-specific certification commonly reports thickness, peel adhesion to stainless steel, tensile strength, elongation at break, and dielectric breakdown voltage using ASTM D3652, ASTM D3330, ASTM D3759, and ASTM D149.

Product Construction and Dimensional Register

The backing consists of an electrical-grade woven glass fabric that has been coated and sintered with polytetrafluoroethylene. Coating weight and fabric construction are not specified on all commercial certificates, but the finished backing is sufficiently filled to produce a non-porous face. The silicone adhesive is applied to the uncoated side of the glass fabric after a surface treatment. This creates an asymmetric construction: the PTFE face has a dynamic coefficient of friction against polished steel in the 0.05 to 0.10 range, while the silicone side develops adhesion through siloxane chain mobility rather than through the high-tack polar monomers typical of acrylic systems. The total thickness tolerance of ±0.001 in is significant in heat-sealing applications because caliper variation across the roll can shift jaw pressure distribution across the sealing land. On wide sealing jaws, users should map thickness with a micrometer across the roll width before installation and place the highest-caliper edge at the low-pressure end of the jaw.

Roll stock should be stored at 10 °C to 27 °C and 40 % to 60 % relative humidity. Storage outside these values does not necessarily destroy the tape but increases two failure modes: edge wicking of moisture into the glass fabric and cold-flow of the silicone adhesive at the roll edge. Rolls should be supported horizontally or hung on cores; flat stacking of narrow rolls can produce permanent flat spots that appear as irregular peel on the sealing jaw. Slitting should be performed with sharp rotary blades or shear knives. Dull slitting blades create fibrous glass-edge debris, which transfers to the PTFE face and contaminates the release surface.

The unwind and application tension on production equipment should be kept low enough to avoid necking the glass fabric. Because the backing is dimensionally stable, excessive tension does not generate useful elongation but can distort the adhesive layer at the nip. On a flat-bed laminator, a nip roll durometer of 60 to 80 Shore A and a pressure setting sufficient to produce uniform adhesive wet-out are typical; the optimum setting depends on surface texture and should be established by peel testing rather than by appearance alone. The tape does not require thermal curing after application, but a brief warm cycle above 100 °C improves adhesive flow into surface irregularities when the substrate is not perfectly smooth.

What Operating Limits Apply to the Silicone Adhesive Interface?

The practical upper temperature limit is governed by the silicone adhesive rather than the PTFE-coated glass. Continuous exposure to 260 °C in clean air is acceptable for limited intervals, but sustained runs at this temperature cause progressive oxidation of methyl side groups on the silicone polymer. The initial result is gradual reduction in peel strength and eventually a hard, non-tackified residue at exposed edges. Above 300 °C, degradation accelerates and the bond between the PTFE coating and the glass fabric can delaminate at cut edges. In sealing machinery, the actual bond-line temperature is lower than the jaw setpoint but depends on heater cartridge placement, jaw material, and cycle rate. Published data for specific jaw geometries and cycle rates is limited; validation should include oven aging at 260 °C for 72 h followed by peel testing according to ASTM D3330.

At low temperature the silicone adhesive loses quick-tack below approximately -20 °C, although the backing remains flexible at -73 °C. Manual application below 0 °C is not recommended because condensation on metallic substrates freezes and prevents wet-out. If the tape is wrapped outdoors or on cold cable, a post-application warm-up above 120 °C drives off surface moisture and sets the adhesive to the substrate. The PTFE face resists liquid water, but water vapor can travel along the exposed glass yarns from the cut edges. In wet installations, edge sealing with a compatible silicone RTV is standard practice to limit hydrolytic attack on the glass-silane interface.

Chemical compatibility is asymmetric. The PTFE face resists most acids, bases, and solvents, but the silicone adhesive is susceptible to swelling in non-polar hydrocarbons and chlorinated solvents. Immersion in toluene, MEK, methylene chloride, or trichloroethylene above 23 °C should be avoided because the adhesive can lose interfacial shear strength. Wiping with isopropanol or naphtha followed by complete evaporation is acceptable for surface preparation. If MEK is used for cleaning on a production line, residual solvent must be allowed to evaporate completely before tape application; entrapped solvent under the adhesive is the most common cause of blistering on heated rolls.

Electrical insulation usage requires attention to cut edges. The construction is commonly recognized under UL 510; assigned voltage and temperature class must be verified against the current UL yellow card for the specific lot. Dielectric strength measured under ASTM D149 on dry tape is not equivalent to the withstand voltage of a wrapped conductor after moisture conditioning. If the cut edge is contaminated by cutting fluid, moisture resistance drops, and end-item tests should be performed on wrapped specimens conditioned at 95 % relative humidity for 48 h. For aerospace wire harness overwrap, specimens are frequently evaluated against the 60° vertical burn requirements of FAR 25.853(a) and BSS 7230; pass/fail data must be obtained from the supplier for the current lot.

On a horizontal form-fill-seal line, the tape is applied to heated aluminum or stainless steel sealing jaws following abrasive cleaning and an isopropanol wipe. The release film is removed under controlled tension so that the adhesive is not pre-stretched before the nip. A spring-loaded or pneumatic lamination roll is set to produce full area contact without crushing the glass weave. Jaw setpoints above 205 °C are common in polyethylene and high-density polyethylene sealing; the tape must be inspected at shift intervals for edge char, adhesive bleed-out, or wrinkles caused by thermal expansion mismatch. Replacement is indicated when the PTFE face exhibits local darkening, when peel adhesion drops below a minimum specified for the process, or when the edge lift exceeds 3 mm along the jaw.

In transformer coil overwrap and cable bundling, the tape is spiraled with a controlled overlap, typically 50 % for high-voltage harnesses, and then consolidated by a heat-shrink or outer wrap. Because the backing is non-porous, trapped air must be allowed to escape through the overlap gap rather than through the tape. Tension should be held below the level that cuts into coil wire; the glass reinforcement provides sufficient tensile strength that operator-induced over-tension is the more common failure mode. The resulting wrap derives its dielectric properties from the combination of glass reinforcement and PTFE coating, but the system rating is established by the completed coil dielectric test, not by the tape datasheet alone.

For composite tooling release, the tape is laid onto a clean metal mold surface and adhered to the tool flanges or smooth tool regions outside the laminate area. The PTFE face provides a low-surface-energy separation interface for bleeder paper, vacuum bag seams, or reusable silicone intensifiers. The silicone adhesive holds at autoclave temperatures up to 200 °C for typical polyester and epoxy cure cycles. The tape should not be used where it will be embedded into the laminate stack without a peel ply, because silicone release from the adhesive side is not equivalent to a free PTFE film and can inhibit interlayer bond if accidentally placed between prepreg plies.

When This Glass-PTFE Construction Replaces Skived PTFE or Acrylic-Adhesive Tapes

A principal difference from skived PTFE film tape is tensile behavior. Unsupported skived PTFE tape elongates under modest mechanical load and can cold-flow, whereas the glass-reinforced backing in CHR SG26-06 holds warp-direction tensile strength near 125 lb/in and limits creep. The trade-off is conformability: the glass fabric is thicker and stiffer, making it less suitable for tight-radius contours below approximately 6 mm without heat forming. In heat-sealing release applications, the glass reinforcement prevents the wrinkling that occurs when skived PTFE tape is cycled on wide L-bar jaws; in exchange, the exposed cut edge is more visible and may require trimming to prevent delamination.

Against acrylic-adhesive glass-PTFE tapes, the silicone adhesive in CHR SG26-06 extends the upper continuous service limit from approximately 149 °C to 260 °C. Acrylic adhesives provide higher initial adhesion to stainless steel at room temperature, commonly in the 40 to 60 oz/in range, and are less expensive, but they soften and lose shear holding power above 120 °C. Silicone adhesive yields a lower room-temperature peel, often near 35 oz/in, but it does not exhibit the same abrupt thermal softening. The manufacturer’s stated service range should be paired with actual dwell-time data because silicone adhesive retains a measurable peel strength after 24 h at 260 °C, whereas many acrylics fail cohesively.

Relative to polyimide-plus-silicone tapes, the glass-PTFE construction provides lower coefficient of friction on the face and higher thickness for the same voltage class, but lower dielectric strength per unit thickness. A polyimide film tape may achieve 7,500 V or more per 0.001 in of thickness, while this construction is approximately 4,500 V over 0.006 in. The selection between these materials should follow the design requirement for surface release versus maximum insulation density. In transformer slot lining or coil bundling where low friction and chemical resistance dominate, the glass-PTFE face is preferred; in motor windings where space factor is critical, a thinner polyimide-silicone tape may be substituted.

Abrasive conditions create an additional distinction. The PTFE-coated glass face is more resistant to trailing abrasion than skived PTFE but is not as abrasion-resistant as a pure woven glass cloth without PTFE. Repeated contact with filled polymers or glass-fiber bundles can wear the PTFE surface and expose the glass fibers, after which coefficient of friction rises. For sliding release applications, the worn face should be replaced when the dynamic coefficient of friction exceeds 0.15 as measured by ASTM D1894.

In composite autoclave use, the glass-PTFE face functions as a separator for peel ply, breather and vacuum bag layers, and the silicone adhesive holds the tape to metal tooling at 180 °C to 200 °C. The tape is not intended for direct lamination into the resin stack. Published data for this specific configuration in long-duration autoclave cycles is limited; users should test peel retention after 4 h at 180 °C and after a repeated cycle to establish a replacement interval.