Saint-Gobain CHR HM650 High Modulus PTFE Film Backing Silicone Adhesive Pressure Sensitive Tape is manufactured in roll form, including spooled slit rolls and die-cut service parts, for release-surface, roller-wrap, electrical insulation overwrap, and high-temperature masking applications. Nominal total thickness is 0.165 mm (6.5 mil); the backing contributes 0.127 mm (5.0 mil) and the adhesive contributes 0.038 mm (1.5 mil). The continuous operating temperature range published by Saint-Gobain is −73 °C to 260 °C (−100 °F to 500 °F). The high-modulus backing differs from conventional skived PTFE film by exhibiting lower elongation under tensile load, which reduces width necking in tension-controlled application systems.

Which construction values are specified for CHR HM650?

The construction is unsupported: no glass fabric or polyester carrier is present. Thickness measurements are performed with methods referenced in ASTM D3652/D3652M. Peel adhesion to stainless steel is measured using ASTM D3330/D3330M after a defined dwell time; tensile strength and elongation of the tape are measured using ASTM D3759/D3759M. Dielectric strength is measured in air or oil using ASTM D149, with the reported value dependent on electrode configuration and ramp rate. The table below lists nominal published values from Saint-Gobain technical literature. Lot-specific certificates of analysis supersede typical values, particularly for thickness tolerance and peel adhesion after aging.

The reported peel adhesion value of 22 oz/in (6.1 N/25 mm) applies to a stainless steel substrate after short dwell at 23 °C and 50 % RH. Longer dwell tends to increase peel adhesion; elevated temperature exposure can first increase and then decrease peel values as the silicone adhesive crosslinks and embrittles. Production qualification should therefore include peel checks after exposure to the actual sealing-bar temperature cycle rather than at ambient only.

On form-fill-seal lines operating at sealing-bar temperature setpoints between 120 °C and 240 °C, polyolefin melt residues adhere to bare steel jaw faces. A strip of CHR HM650 applied across the jaw face introduces a low-surface-energy release interface; the critical surface tension of PTFE is approximately 18.5 mN/m at 20 °C. The adhesive layer remains tacky within the continuous service range, but production records from rotary band sealers show that edge lift and char occur earlier when thermocouple overshoot exceeds the 260 °C limit by more than 10 °C for repeated cycles. Temperature controllers with PID tuning and thermocouple placement within 5 mm of the jaw face are used to reduce setpoint overshoot. The tape thickness introduces a small thermal resistance; a setpoint offset of 5 °C to 10 °C is commonly required to maintain melt temperature at the sealing interface.

In continuous roll-to-roll lamination, unwind tension from automatic taping heads can neck standard skived PTFE film. The high-modulus backing is specified where width reduction under tension causes exposed adhesive zones or uneven release. Published elongation at break of 150 % is not an allowable service strain; cyclic loading should remain below 2 % to 5 % strain to avoid permanent deformation. Application on cylindrical rollers below 25 mm diameter may require pre-curled slit rolls or higher-tack silicone adhesive to prevent edge lift. Rollers should be cleaned with isopropyl alcohol or methyl ethyl ketone and dried before tape application; a 3 mm to 6 mm overlap is maintained in the machine direction to reduce seam leakage.

Measurements and failure modes define incoming conformance limits

When CHR HM650 is qualified for a new line, the incoming inspection plan should include total thickness, width, peel adhesion to the actual sealing-bar alloy, and dielectric strength if electrical insulation is claimed. Thickness is measured at multiple points across the web using a calibrated thickness gauge; width is measured with a steel scale under no tension. Peel adhesion on the actual substrate is more informative than the stainless steel datasheet value because chrome-plated sealing bars may produce different values. Failure modes observed on production equipment include adhesive edge bleed after cycling to 260 °C, film tearing at die-cut notches, and release-character loss after silicone oil contamination. Contamination by hydrocarbon-based lubricants can often be removed from the PTFE surface with isopropyl alcohol, but silicone-oil contamination may require replacement because it plasticizes the adhesive interface.

In roller wrapping, the tape is applied under controlled tension not exceeding 10 N per 25 mm width. Excessive tension can exceed the elastic recovery limit and cause adhesive delamination at the overlap seam. The wrapped roll is run at low speed to confirm concentricity before full production. On crowned rollers, wrinkles can form unless the tape is spirally wrapped at a 15° to 20° angle. Edge sealing with a heated roller or silicone edge adhesive is required in wet-coating service to prevent coating penetration under the seam.

Heat-seal bar release, roller wrapping, and electrical overwrap

Three use environments are supported by the same construction. In heat-seal release, the unsupported film prevents melt adhesion without transferring a fabric pattern to polyethylene or polypropylene webs. In roller wrapping, the PTFE surface reduces coating build-up on idler rolls, lay-on rollers, and gravure backing rolls; the silicone adhesive permits removal without excessive adhesive transfer, though long aging at upper temperatures can increase residue. For electrical insulation overwrap, the published dielectric strength of 1000 V/mil (39 kV/mm) supports use in low-voltage harness wrapping; final insulation system performance should be verified to ASTM D1000 or the relevant end-product standard, not inferred from tape dielectric strength alone.

Thermal aging of the silicone adhesive changes peel strength. At continuous exposure near 200 °C, peel adhesion to stainless steel can increase during the first 24 h to 72 h as wetting improves, then decline as crosslinking proceeds. Qualification programs for heat-seal bars therefore include peel adhesion samples aged at the actual setpoint for 100 h and inspected for adhesive transfer. The PTFE backing remains stable below 260 °C; above that threshold, decomposition products include fluorine-containing gases, and mechanical properties degrade even if the film remains intact.

When PTFE-coated glass cloth tape is too thick or patterned

PTFE-coated glass cloth tapes with silicone adhesive provide higher tensile strength and puncture resistance but have a woven surface pattern that can transfer into heat-seal films. CHR HM650 uses an unsupported high-modulus PTFE film, so it provides a smooth release face with no fiber print-through. The trade-off is lower tensile strength: published tensile strength for HM650 is 30 lb/in (131 N/25 mm), whereas glass-cloth composites can exceed 100 lb/in (438 N/25 mm). Conventional skived PTFE film tape may show elongation at break greater than 300 %; HM650 at 150 % exhibits reduced extensibility under load. Polyester/silicone tapes are generally limited to 150 °C continuous service and have lower solvent resistance. Polyimide/silicone tapes can match temperature capability but lack the same low-surface-energy release character of PTFE.

Values in the comparison table are representative of commercial product classes; individual product datasheets and lot certificates should be used for qualification. Comparative tensile and elongation values are measured according to ASTM D3759/D3759M or equivalent tape test method; thermal limits are manufacturer-rated.

Silicone pressure-sensitive adhesives are not specified for load-bearing structural attachment. Bond strength on polyethylene, untreated polypropylene, and other low-surface-energy substrates is lower than on polar metals; corona or plasma treatment of the substrate may be required but can introduce variability if treatment level falls below 38 mN/m wetting tension measured by ASTM D2578. In semiconductor cleanrooms, paint spray booths, and silicone-sensitive optical assemblies, low-molecular-weight siloxane species can evolve under heat and vacuum. The tape should not be introduced into those environments unless extractable siloxane testing to a customer-defined limit demonstrates compatibility. PTFE is chemically resistant to most acids, bases, and solvents up to the continuous temperature limit; elemental fluorine, chlorine trifluoride, and molten alkali metals attack PTFE and must be excluded. The adhesive bond line should be kept below 260 °C; prolonged dwell at the upper limit can increase crosslinking and reduce peel adhesion. If dielectric testing exceeds 1000 V/mil in production, electrode geometry and tape thickness variation must be controlled.

Roll stock is stored at 21 °C and 50 % RH for a shelf life of 12 months from date of manufacture. Storage outside these limits can accelerate adhesive oxidation or interlayer blocking. Compliance records for RoHS Directive 2011/65/EU and Regulation (EC) No 1907/2006 (REACH) should be obtained from the manufacturer’s current certificate of conformance rather than assumed from material class. Food-contact suitability requires specific end-use review against FDA 21 CFR 177.1550 and 21 CFR 175.300; the adhesive system may not be cleared for all food types.