Saint-Gobain CHR 2255-5 is constructed from a high-modulus polytetrafluoroethylene film backing and a pressure-sensitive silicone adhesive layer. Manufacturer-published dimensional data list backing thickness at 0.127 mm (5 mil) and total tape thickness at 0.165 mm (6.5 mil). The backing is differentiated from conventional skived PTFE by higher modulus and lower elongation under tensile load, which reduces dimensional distortion during web-fed converting. Typical tensile strength is reported as 35 lbf/in (6.1 N/mm) when measured according to ASTM D3759, and elongation at break is approximately 50%. Pressure-sensitive adhesion to stainless steel is typically 20 oz/in (2.2 N/cm) by ASTM D3330. These values are typical rather than guaranteed.

What Distinguishes High-Modulus PTFE from Standard Skived PTFE Tape?

The high-modulus backing alters the relationship between web tension and strain. Under a tensile load of 1.0 N/mm, standard skived PTFE can exhibit measurable necking and elongation; the high-modulus grade reduces this deformation, which is critical on narrow-web converting lines where width loss must remain below 0.5%. Dimensional stability is further influenced by the crystalline transition of PTFE near 19 °C and melting near 327 °C. Below the first transition, the polymer is slightly more rigid, but the tape remains flexible enough for wrapping rolls and irregular surfaces.

Coefficient of friction against polished steel is approximately 0.05–0.10 when measured by ASTM D1894. The exposed PTFE face also exhibits low surface energy, typically below 20 mN/m, so molten polyethylene, hot-melt adhesives, and aqueous coatings do not wet the backing. This nonstick face is not a coating; it is the bulk property of the film, which prevents release-property loss from surface abrasion during long sealing cycles. However, PTFE is subject to cold flow under concentrated compressive stress. High-modulus backing reduces but does not eliminate thickness loss under heated roller pressure.

In electrical insulation applications, the film-backed construction provides a more uniform dielectric barrier than woven glass-cloth PTFE tapes because there are no glass-fiber interstices. Volume resistivity of the PTFE backing is on the order of 10¹⁷ Ω·cm by ASTM D257. Dielectric breakdown for a 0.165 mm total thickness is typically above 10 kV by ASTM D149, although the adhesive layer and contamination on the surface can reduce measured values. Users performing motor coil wrapping or transformer interlayer insulation should verify the insulation class against the specific design voltage and mechanical stress.

Thermal, Electrical, and Chemical Limits of the Silicone—PTFE System

The silicone adhesive is specified for continuous service from -73 °C to 260 °C. Intermittent operation above 260 °C accelerates silicone oxidation, reduces tack, and can transfer low-molecular-weight siloxane species to adjacent webs. At the low end of the range, silicone polymer retains flexibility, but adhesion to cold metal surfaces may decline below -50 °C unless the substrate is cleaned with isopropanol and warmed above 10 °C. The PTFE backing itself can withstand higher temperature excursions, but the adhesive typically governs the practical upper limit.

Chemical resistance of the PTFE face is broad across acids, bases, ketones, esters, and aliphatic hydrocarbons. The backing is not resistant to molten alkali metals, fluorine gas, or chlorine trifluoride at elevated temperature. The silicone adhesive can swell in contact with aromatic hydrocarbons and certain chlorinated solvents, which may temporarily lower shear strength. For applications involving strong solvents, pre-testing under the exact immersion or wipe condition is required. Silicone adhesive systems are not recommended for surfaces destined for subsequent painting, coating, or adhesive bonding because silicone transfer can inhibit wetting. The exposed PTFE backing itself is extremely difficult to bond without chemical etching or plasma treatment.

Storage before application should be in a dry area at approximately 21 °C and 50% RH. Under these conditions, a shelf life of 12 months from the date of manufacture is common for silicone pressure-sensitive tapes, though published data for this specific configuration should be confirmed on the certificate of analysis. Rolls should not be stored in direct sunlight or near ozone-generating equipment because silicone adhesives can undergo oxidative crosslinking over time.

In heat-sealing operations on polyethylene and polypropylene films, the tape is applied to seal bars operating at surface temperatures between 150 °C and 220 °C. The silicone adhesive transfers heat from the bar to the polymer web while the PTFE face prevents molten polymer build-up. Seal dwell times below 0.8 s and pressure settings of 2–4 bar are common on rotary equipment. Field observations on packaging lines indicate that residue accumulation is influenced more by seal-bar temperature uniformity than by tape thickness. Thermocouple surveys of heated bars show edge-to-center deviations of ±5 °C increase polymer tack transfer to the PTFE face.

During laminating nip service, the smooth PTFE surface prevents adhesive and coating transfer to idler rollers. High-modulus backing resists elongation under nip tension, but thermal expansion of PTFE must still be accommodated. The coefficient of linear thermal expansion of PTFE is approximately 12 × 10⁻⁵ K⁻¹ near 250 °C. A roller tape applied at ambient temperature and heated to operating temperature can expand significantly; edges may lift if the tape is not cut with allowance for thermal movement. Operators should avoid excessive overlap because a double-thickness seam can create a hard band that marks thin polymer webs.

When the 2255-5 Replaces Acrylic-Adhesive PTFE Tape on Heated Rollers

Acrylic-adhesive PTFE tapes typically offer higher initial peel to stainless steel at 25 °C, often in the range of 3.0–4.0 N/cm, but lose shear strength above 150 °C. The silicone adhesive on CHR 2255-5 is specified for continuous service at 260 °C, though prolonged exposure at that temperature reduces tack and increases the risk of adhesive transfer. For applications requiring high room-temperature bond and no silicone contamination, acrylic versions are preferred. For high-temperature release and low-surface-energy bonding, silicone is preferred.

Compared with standard skived PTFE tape, the high-modulus backing shows lower elongation and better retention of width under converting tension. This difference is most visible on narrow rolls below 25 mm width, where standard PTFE can neck down enough to expose the backing edge. The silicone adhesive is the same chemistry used on many higher-temperature PTFE tapes, but the backing modulus is the key variable. In applications where conformability around sharp corners or complex shapes is more important than dimensional stability, a lower-modulus or glass-cloth PTFE tape may be a better match.

Compared with glass-cloth PTFE tapes, CHR 2255-5 provides a smoother surface and a thinner total profile. Glass-cloth reinforced products have higher tear strength and puncture resistance, which helps in abrasive or sharply angled service. The film-backed tape is more suitable for electrical wrapping and heat-seal bars where a thin, uniform, non-reinforced dielectric layer is required. The trade-off is lower resistance to edge tear and lower puncture resistance.

Application Practice on Impulse Seal Bars and Laminating Nips

The tape should be applied to a clean, dry substrate. Recommended surface preparation includes wiping with isopropanol or methyl ethyl ketone and allowing the solvent to flash completely. Substrate temperature should be between 10 °C and 40 °C. A laminating roller or hand roller with a contact pressure of approximately 4.5 kg is used to wet out the adhesive; full adhesion build occurs over 24 h. Heat-seal bars should be cycled briefly after installation to allow the adhesive to flow and establish contact with the heated surface. Re-tensioning after 24 h is often necessary on rotating roller wraps.

Silicone adhesive systems are not compatible with certain addition-cure silicone elastomers or tin-catalyzed silicone coatings. Contact with amine-based epoxy curing agents or strong organic bases can interfere with adhesive performance and accelerate degradation. For food-contact applications, the PTFE backing resin may be manufactured from materials complying with FDA 21 CFR 177.1550, but the silicone adhesive must be evaluated separately under the applicable food-contact regulation. The product is normally supplied without intentionally added restricted substances under RoHS 2011/65/EU, and the supplier should provide a REACH 1907/2006 SVHC declaration for the specific lot.

For silicone-sensitive areas, including paint preparation booths, semiconductor cleanrooms, and coating lines, CHR 2255-5 should be segregated from surfaces that will later receive optical coatings, conformal coatings, or adhesion bonding. Silicone transfer from the adhesive can migrate through air currents and handling. If a low-silicone or silicone-free high-temperature release surface is required, alternative fluoropolymer tapes with non-silicone adhesives or mechanical fastening should be considered. Published data for this specific configuration in semiconductor cleanroom applications is limited; qualification under cleanroom protocol is required before production use.

In wire and cable harness processing, the tape is wrapped with 50% overlap on PTFE-jacketed wire bundles. The silicone adhesive remains tacky through thermal cycling, but adhesion to silicone rubber cable jackets may be lower than to crosslinked polyethylene or PTFE. When exposed to hydraulic fluid or jet fuel, the PTFE backing resists degradation, but the adhesive bond may be weakened by plasticizer migration from adjacent elastomeric components. Pre-testing under the full fluid and temperature profile is necessary.

The product can be slit to narrow widths for automated taping heads on wire processing equipment. Dimensional stability of the high-modulus backing supports clean slitting with less edge fray than standard skived PTFE. Slit rolls should be inspected for adhesive ooze at the edges; ooze becomes more likely when storage temperatures exceed 32 °C. Refrigeration of slit rolls is not recommended because moisture condensation on cold adhesive can interfere with bonding.

For high-voltage motor winding, the tape is used as an interlayer insulation over magnet wire. The dielectric breakdown value is influenced by wire surface roughness, varnish compatibility, and winding pressure. A varnish compatibility test is required because some polyester or epoxy impregnating resins contain solvents that can soften the silicone adhesive. In such cases, the tape should be applied over the wire and varnished before the adhesive has been exposed to solvent outside the tape edges. If varnish bleed is observed along the seam, the adhesive bond may degrade during cure.

On laminating machines, the tape is installed on heated idler rolls and coating transfer rolls. The roll surface should be free of pits larger than 0.25 mm because PTFE film can bridge small depressions but will not hide surface roughness. The adhesive layer is thin and does not fill deep scratches. A polished roll surface with roughness below 0.4 µm Ra provides the best visual and release uniformity. Roll runout above 0.05 mm total indicated motion can cause cyclic tension variation that overcomes the dimensional stability gain of the high-modulus backing.

Differences from other products are most apparent under sustained thermal cycling. A standard skived PTFE tape with similar adhesive may show greater thickness loss under heated pressure because PTFE cold flow is not restrained by orientation. The high-modulus backing retains more of its original thickness after repeated heating and compression, which helps maintain consistent seal pressure. This is not a zero-creep condition; after extended cycles, some thickness loss remains measurable by micrometer. Therefore, seal-bar gap settings should be checked after the first 500 h of production or after any visible change in seal impression depth.