Saint-Gobain CHR T skived PTFE film-backed silicone adhesive pressure-sensitive tape is a single-coated, non-reinforced fluoropolymer tape manufactured by applying a crosslinked silicone pressure-sensitive adhesive to a skived polytetrafluoroethylene film. The backing is not extruded or cast. It is produced by rotating a sintered PTFE billet against a stationary skiving blade; this yields a continuous, isotropic film without a woven or nonwoven carrier. The construction is used where the non-adhesive face must provide release, chemical inertness, and thermal stability while the silicone adhesive maintains bond integrity across a wider temperature window than acrylic or rubber systems. Standard CHR T suffixes differentiate backing calipers and liner configurations, so a production specification should cite the suffix, roll width, roll length, core size, and liner requirement. Saint-Gobain publishes grade-specific technical data for thickness, adhesion, dielectric strength, and compliance; the values in this document represent the family envelope and are not a substitute for the certificate of conformance.

How Does the Skived PTFE Film Backing Govern Dielectric and Release Properties?

Skived PTFE film is machined from a sintered PTFE billet, not deposited or extruded onto a carrier. The resulting backing is free of glass-cloth print-through and has isotropic in-plane mechanical properties. In comparison with biaxially oriented PTFE film, skived film generally provides lower tensile strength per unit thickness but broader caliper availability and enough conformability for small-radius bars. The non-adhesive face exhibits a surface energy in the range of 18–20 mN/m at 20 °C; this surface energy is the basis of its release function. Electrical performance is thickness-dependent. Breakdown values measured under ASTM D149 for unfilled PTFE film typically fall near 50–120 kV/mm, but total withstand voltage must be calculated from the actual backing thickness and electrode geometry. The silicone adhesive layer is anchored to the treated PTFE surface during coating; the exact corona or chemical treatment is proprietary. The adhesive side develops peel more slowly than acrylic systems, but it retains cohesive strength at sealing-bar temperatures that would melt or oxidize acrylic PSA. Roll products may be self-wound or interleaved with a release liner depending on grade.

On horizontal form-fill-seal machines, the tape is applied to heated sealing jaws and fin-seal bands to prevent molten polyolefin film from accumulating on the metal. A backing thickness of 0.10–0.15 mm is commonly selected when jaw radii exceed 3 mm; tight-radius bars usually require thinner film because thicker skived PTFE can lift at the wrapped edge. The metal surface is degreased before application, allowed to flash off for 10–15 min, and then rolled with a silicone-covered laminating roller at approximately 0.2–0.4 MPa nip pressure. The tape should not be stretched during installation; tension in the backing becomes shear creep at the adhesive interface when the bar reaches 200 °C. In wire harness and coil wrapping, the PTFE backing provides an oil-resistant, low-friction overwrap and a continuous dielectric barrier. For adhesive metering lips, chute liners, and roll coverings, the silicone adhesive may be insufficient at exposed edges under high shear; a mechanical clamp or a narrow high-tack acrylic transfer adhesive edge strip is applied where peel-lever failure is observed.

Surface Preparation, Dwell Time, and Silicone Adhesive Transfer

Aluminum and stainless steel are the most predictable substrates for silicone PSA. Production-scale failure analysis on heated bars has linked bond loss to residual cutting oil and to silicone oil contamination; solvent wiping with methyl ethyl ketone or isopropanol followed by a dry polyester wipe is the minimum preparation. Wetting tension should be characterized by ASTM D2578 when applying to polyethylene or polypropylene; for polyamide, acetal, or other engineering plastics, surface energy is verified by contact angle or the tape supplier’s wet-out method. Values below 38 dyn/cm generally produce weak ultimate adhesion unless corona or plasma treatment raises the surface to 42–48 dyn/cm. Silicone PSA develops adhesion more slowly than acrylic PSA. At 23 °C ± 2 °C and 50 % ± 5 % RH, peel strength on clean steel reaches approximately 80 % of final value within 24 h, with full wet-out over 72 h. Dwell at 60 °C accelerates wet-out but must not exceed the substrate’s thermal tolerance. Direct bonding to cured silicone rubber often requires a compatible silicone primer because the adhesive’s initial tack on silicone is lower than on metal or high-energy plastic.

In continuous flex-service on roller surfaces, the skived PTFE backing is selected for release rather than load-bearing. Because the backing has no woven carrier, it should not be used as a primary belt splice or as the sole insulation where mechanical stress exceeds the manufacturer’s tensile rating. Edge lifting is the dominant failure mode on small-diameter rollers when total caliper exceeds 0.20 mm; field data from packaging operations suggest that narrower tape widths and calendered silicone adhesive layers reduce the peel-lever effect at the edge. Chemical resistance of the backing is limited at elevated temperature by molten alkali metals and elemental fluorine, while the silicone adhesive may degrade in continuous contact with strong polar solvents, chlorinated solvents, and some ester-based plasticizers. In paint-shop and electronics-cleanroom environments, silicone low-molecular-weight migration should be assessed before installation because silicone contamination can create coating defects in subsequent operations. Roll blocking can occur if self-wound rolls are stored above 40 °C; liner-equipped grades are selected for long-term storage or high-temperature warehouses.

When Silicone Adhesive Replaces Acrylic or Rubber Systems

Acrylic pressure-sensitive adhesives typically provide higher peel adhesion at 23 °C and lower cost, but their continuous service is limited to approximately 120 °C and low-temperature flexibility can drop below -40 °C. Rubber-based PSAs offer aggressive initial tack but have poor solvent resistance and are unsuitable at sealing-bar temperatures. Silicone PSA is specified when the bonded assembly must survive repeated thermal cycles between -73 °C and 204 °C, or when the adhesive must not shrink or char on a heated sealing jaw. The selection trade-off is initial peel versus thermal endurance and low-temperature performance. Comparison should be made using ASTM D3330/D3330M peel data generated at both 23 °C and the intended operating temperature, because silicone PSA retains a larger fraction of its room-temperature peel at 150 °C than typical acrylic PSA.

Published datasheets for individual CHR T suffixes differ from these family typical ranges. The following property envelope is therefore a selection guide rather than a batch-specific specification.

Because dielectric strength is thickness-dependent, transformer insulation and high-potential testing should not rely on a single volts-per-mil value across the family. A 0.10 mm backing may show a total withstand voltage in the general range of 6–10 kV depending on electrode geometry and conditioning, while a 0.25 mm backing provides a higher absolute barrier but lower conformability on tight winding tubes. If UL recognition is a requirement, the specific CHR T suffix and its status must be checked against the current UL 510 file; not every thickness class necessarily carries the same recognition. Generic PTFE electrical data should not be substituted for certified CHR T values in a production dielectric specification.

What Regulatory and Standards Documentation Applies to the CHR T Family?

PTFE homopolymer film is commonly referenced under FDA 21 CFR 177.1550 for food-contact applications. The silicone adhesive layer must carry its own food-contact status, typically under an applicable adhesive or pressure-sensitive adhesive regulation such as 21 CFR 175.105 or 21 CFR 175.125 depending on the end use. These references do not automatically apply to every CHR T suffix or liner; a grade-specific compliance statement from Saint-Gobain should be retained in the lot qualification record. Purchasing for electrical insulation should verify UL 510 recognition where specified, and environmental compliance is usually documented against REACH Candidate List obligations and RoHS 2011/65/EU. A general technical note does not replace a certificate of conformance for production, food-contact, or regulated electrical use.

Roll storage before application affects silicone adhesive transfer and unwind. Flat or core-suspended storage is used; edge-on storage under high humidity can cause liner waviness and adhesive offset. A controlled warehouse at 10–27 °C and 40–60 % RH preserves wet-out behavior. Manufacturer shelf life for silicone PSA tapes is commonly 12–24 months from the date of manufacture in original packaging; after that period, adhesion should be re-qualified by ASTM D3330/D3330M peel and ASTM D3654 shear testing before production use.

Roll widths are typically supplied from 6 mm to 500 mm, depending on slitting capacity. When replacing a PTFE-coated glass cloth tape with CHR T on a sealing jaw, a common design change is to reduce backing thickness by one step to compensate for the loss of woven reinforcement and to maintain thermal transfer through the tape. Qualification should measure seal-strength retention on the production film after 72 h of continuous sealing at the highest setpoint; if seal strength varies by more than 10 % from the incumbent construction, the sealing temperature and dwell time should be adjusted before full production release.