Specified for high-temperature release, masking, and supplementary electrical isolation duties, Saint-Gobain CHR SG35-05(R) is a pressure-sensitive tape formed from a woven fiberglass cloth carrier impregnated with polytetrafluoroethylene and coated on one face with a silicone adhesive. The glass reinforcement limits elongation and resists cut-through; the PTFE surface provides release, low friction, and resistance to aggressive process chemicals. The silicone adhesive is selected for retention of peel strength after sustained exposure up to 260°C (500°F) and for adhesion to low-porosity surfaces that are frequently preheated in thermal processing. The (R) suffix appears in supplier part-numbering for standard roll-pack configurations; it does not indicate a change in backing chemistry or adhesive type. Representative values for this product class are shown in Table 1. These are single-point or narrow-lot data drawn from supplier technical bulletins and should be verified against the certificate of analysis for the specific production lot before setting a purchasing specification.

Peel adhesion values in Table 1 are obtained with 180° peel from stainless steel after a 20-minute dwell at 22°C and 50% relative humidity. Full adhesive bond development can require 24 h at 22°C; post-cure at 65°C for 4 h accelerates wet-out and increases peel values by 10% to 20% relative to short-dwell measurements. Silicone pressure-sensitive systems do not exhibit the rapid room-temperature tack of solvent-borne acrylic or rubber adhesives; initial repositionability should be expected on cold steel or aluminum substrates. Initial positioning below -18°C is not recommended because silicone PSA tack declines sharply; the tape can be stored at temperatures below freezing but should be conditioned at 22°C for 4 h before application.

Because the glass cloth is not calendered to a film grade, thickness variation across a 1,000 mm web may range from ±0.012 mm to ±0.025 mm. This variation influences dielectric withstand voltage and platen contact uniformity; converters should specify thickness binning when the tape is used for precision die-cutting or automated wrapping. The silicone adhesive layer thickness is typically held to 0.038 mm (0.0015 in) with a tolerance of ±0.008 mm.

What Operating Limits Control Silicone Adhesive Transfer on Heated Platens?

On flat-bed sealing equipment with cartridge-heated steel platens, the tape is positioned on the non-sealing tool face to prevent molten polyethylene or polypropylene from building up on the platen. In production-scale rotary sealers, platen temperatures of 160°C to 230°C, dwell times of 0.8 s to 3.0 s, and mechanical pressures of 0.28 MPa to 0.55 MPa (40 psi to 80 psi) are common for polyethylene films. At the upper end of this range, the silicone adhesive remains stable; transfer to the platen is more likely when the platen temperature exceeds the adhesive’s continuous service limit by more than 15°C or when dwell pressure exceeds 0.7 MPa. Bond failure under heated shear is observed primarily at the adhesive-backing interface where the silicone layer has undergone additional crosslinking or where low-molecular-weight silicone fractions have migrated to the exposed edge. Edge ooze of 0.2 mm to 0.5 mm has been documented on wide-web laminators when wound roll tension was set above 0.6 kN/m; controlling unwind tension to 0.35 kN/m or lower reduces telescoping and adhesive transfer at slit edges.

Substrate surface energy governs initial wet-out. The silicone adhesive can bond to clean metals and high-energy polymer films without primer, but untreated polypropylene and polyethylene surfaces below 32 dyn/cm typically require corona or plasma treatment. Wetting tension is evaluated by ASTM D2578; the treated surface should be processed within the window specified by the corona treater, commonly 40 dyn/cm to 48 dyn/cm. On stainless steel, peel adhesion after 20 minutes is approximately 45% of the 24-hour value. For humid environments, condensation on the substrate at temperatures below the dew point lowers initial tack; pre-drying at 60°C for 5 minutes or maintaining a substrate temperature at least 3°C above dew point is required.

Because the PTFE surface is non-stick, the tape is used as a release interface in heat sealing; it does not transfer silicone oil to the film when the adhesive is on the opposite face. The dynamic coefficient of friction of the PTFE face against steel is typically 0.08 to 0.12 per ASTM D1894. This low-friction surface can alter film slip behavior on inclined conveyors; equipment guarding and feed rolls must be adjusted when the tape is installed on high-angle transfer plates. Film contamination in heat sealing is assessed by visual inspection for silicone transfer under UV light; the PTFE face should show no adhesive bleed-through at platen temperatures up to 230°C. If bleed-through occurs, the tape should be replaced with a thicker backing or process pressure reduced.

At temperatures above 260°C, PTFE may evolve trace fluorine-containing decomposition products. Local exhaust ventilation is required when continuous exposure exceeds 260°C; at temperatures above 350°C, PTFE degradation becomes measurable and the tape should not be used without site safety review. The silicone adhesive itself can shift from a tacky viscoelastic solid to a brittle elastomer after extended exposure above 250°C; peel strength may drop by 30% to 50% and cohesive failure may occur within the adhesive layer. Thermal mapping on narrow seal bars shows edge temperatures can exceed centerline by 10°C to 15°C, so the control temperature at the tape edge should be included in process capability studies.

In plasma spray masking and thermal spray coating operations, the tape is applied to adjacent surfaces to prevent adhesion of molten metal droplets and ceramic overspray. The glass-PTFE backing resists particle abrasion and allows overspray to be peeled away with the spent masking. The silicone adhesive provides holding power at preheat plate temperatures up to 120°C; published data for this specific configuration is limited above 260°C, and sustained exposure to plasma plume radiation above that limit can embrittle the adhesive and cause partial lifting at tape edges. In wire harness and cable bundling operations, the tape is spiral-wrapped with 50% overlap; the low elongation prevents the tape from necking during tensile wrapping, and the silicone adhesive remains non-corrosive on copper and nickel-plated connectors. Insulation resistance of the wrapped assembly is tested under IEC 62631-3-1 or comparable service authority procedures; the tape alone is supplementary insulation and not primary dielectric isolation.

Compared with skived PTFE film tapes using silicone adhesive, CHR SG35-05(R) has lower elongation and higher tensile strength; skived PTFE film tapes commonly exceed 200% elongation and are used where conformability to complex geometry is required, whereas the woven glass backing of CHR SG35-05(R) remains below 5% elongation and resists cut-through during slitting and die cutting. Compared with acrylic adhesive PTFE film tapes, the silicone adhesive extends continuous service temperature from approximately 149°C to 260°C, but silicone PSAs generally develop lower initial room-temperature tack and can be more sensitive to aromatic hydrocarbon exposure. Compared with silicone-coated fiberglass cloth without PTFE, the PTFE surface provides a lower coefficient of friction and does not transfer silicone oil from the backing face, which is relevant in heat sealing where film contamination is a rejection condition.

Comparative Construction and Performance Matrix for High-Temperature Tape Families

Table 2 is a comparative summary of supplier technical data for high-temperature tape families; the values are not process specifications for a particular converting run. Product selection between CHR SG35-05(R) and skived film or acrylic constructions depends on elongation recovery requirements, die-cutting tolerances, and wet-out characteristics on three-dimensional parts.

For electrical insulation and chemical processing, the tape is applied to roll ends, flange faces, and conductive enclosure seams where supplementary arc-flash or corrosion protection is required. The dielectric strength class in Table 1 is applicable only when the tape is dry and free of conductive contamination; voltage withstand is tested at the assembled part level per IEC 60243 or ASTM D149. Dielectric strength is temperature-dependent; the short-time value at 23°C should be derated by approximately 10% to 15% at 180°C. Surface resistivity of the PTFE face is typically 10¹⁶ ohm/square under laboratory humidity per ASTM D257; contamination by release agents or carbon dust lowers surface resistivity and must be controlled before high-voltage testing.

Chemical exposure is limited on the adhesive side: aromatic hydrocarbons, ketones, and chlorinated solvents soften silicone PSA and reduce cohesive strength. Wipe-down with isopropyl alcohol or aliphatic hydrocarbon is acceptable; immersion in methyl ethyl ketone is not recommended because the adhesive can lose more than 50% of its original peel strength after extended exposure. For food-contact use, the PTFE component may be evaluated under FDA 21 CFR §177.1550; the silicone adhesive may be evaluated under FDA 21 CFR §175.300; migration test data for the assembled tape under specific food-simulant conditions is limited and must be obtained from the supplier for the intended contact time and temperature. Regulatory declarations for RoHS 2011/65/EU and REACH 1907/2006 should be obtained from the converter because the assembled tape may contain residual solvents or cure byproducts not fully disclosed on the safety data sheet.

Roll stock should be stored at 10°C to 27°C and 40% to 60% relative humidity. Moisture uptake by the backing is low, but condensation below the dew point will reduce initial adhesion. Slitting tolerances from converters are typically ±0.4 mm for widths up to 100 mm; wider formats may exhibit ±1.0 mm edge drift on rotary shear equipment. Rotary shear slitting of CHR SG35-05(R) generates less adhesive buildup than skived PTFE film tapes because the glass cloth resists stretching and adhesive ooze at the cut edge. Dull blades above 0.02 mm wear can produce fiber pullout and white edge dust; blade life on high-speed slitting lines is typically 20,000 m to 40,000 m per edge. When the tape is applied to heated platens, a break-in period of 2 to 5 heat cycles is often observed before the silicone adhesive reaches stable shear holding; production acceptance trials should include this conditioning interval.