Saint-Gobain CHR SG33-10(R) is a pressure-sensitive tape constructed from a woven fibreglass cloth that has been coated and encapsulated with polytetrafluoroethylene resin; the opposite face carries an acrylic pressure-sensitive adhesive. The (R) suffix identifies roll-pack format and does not denote a change in the PTFE-glass chemistry. The product is supplied in slit-roll form and is used as a release surface, electrical insulation wrap, and anti-adhesion facing on heated process equipment. The glass scrim provides tensile resistance and dimensional stability that a homogeneous skived PTFE film cannot match under comparable load.

During manufacture, the glass cloth is coated or dip-impregnated with an aqueous PTFE dispersion and then sintered. Multiple dip passes may be used to build the non-stick envelope. The sintering step drives off water and surfactant, leaving a fused fluoropolymer layer. The composite backing has anisotropic properties: the machine direction has higher tensile strength and lower elongation than the cross direction because the glass yarn orientation is not perfectly isotropic. Slit rolls should be oriented so that the machine direction aligns with the load direction in wrapping and sealing applications. Misalignment can produce early fatigue at the wrap edge.

Typical properties from manufacturer product literature for this configuration include a total thickness of 0.006 in (0.15 mm), comprising a PTFE-glass backing of 0.0045 in (0.11 mm) and an acrylic layer of 0.0015 in (0.038 mm). Slit widths are commonly available from 0.25 in (6.4 mm) to 36 in (914 mm), with standard roll length of 36 yd (33 m) and other log lengths on request. Peel adhesion to stainless steel at 180° peel under ASTM D3330 is reported in the 45 oz/in to 65 oz/in range (12.3 N/25 mm to 17.8 N/25 mm) after 24 h dwell. Breaking strength of the backing under ASTM D3759 is approximately 150 lb/in (263 N/25 mm), with elongation at break below 5%. Short-time dielectric breakdown of the backing under ASTM D149 is commonly quoted at 4.0 kV. These are representative lot-centre values; production qualification should use the supplier certificate of analysis because slit-roll tolerances and adhesive coat-weight variation can move the measured values.

For incoming quality assurance, the following standard method map is used to evaluate the tape against its advertised characteristics. The presence of a method below does not imply that every commercial lot is certified to that method; test selection depends on the final application and the purchaser’s specification.

Installation on production equipment requires attention to the acrylic adhesive’s minimum application temperature and pressure. Bond formation is poor below 10 °C. The tape should be applied to degreased substrates at 15–30 °C with a hand roller or nip roller delivering 3–5 N/cm pressure. Full peel strength is not immediate; final wet-out can require 24–72 h depending on substrate roughness. Cleaning of the substrate with isopropanol or a 50:50 isopropanol/water mixture is preferred. Acetone, methyl ethyl ketone, and toluene should not be allowed to contact the adhesive side because they can swell the acrylic polymer and reduce shear holding power.

Roll stock should be stored in original packaging at 10–27 °C and 40–60% relative humidity; shelf life for acrylic pressure-sensitive tapes is typically 12 months from date of manufacture when protected from direct sunlight and heat sources above 30 °C. If rolls are conditioned below application temperature, they should be brought to ambient in sealed packaging to prevent condensation on the adhesive face.

The acrylic PSA is a viscoelastic polymer that exhibits time-temperature superposition; its peel force accordingly depends on rate and temperature. At high peel rates, peel strength can be lower than the static wet-out value. On textured steel, pressure and dwell time increase the contact area and raise the observed peel value. The glass transition temperature of common acrylic PSAs is below −20 °C, which is why room-temperature tack is available but low-temperature peel may still be affected by substrate stiffness and backing modulus.

What separates an acrylic-adhesive PTFE-glass tape from silicone-bearing equivalents?

An acrylic pressure-sensitive adhesive on a PTFE-glass backing has a lower continuous-temperature ceiling than a silicone-PSA version in the same product family, but it reduces the risk of siloxane transfer to electrical contacts, relays, and optical surfaces. Silicone PSAs retain tack above 230 °C; the acrylic layer is generally limited to 177 °C (350 °F) continuous service, with short high-temperature excursions tolerated only when the shear load is low and the dwell time is short. Acrylic adhesion to polar substrates such as steel, aluminium, epoxy-glass, and polyimide is typically more aggressive than silicone, especially after 24–72 h wet-out. The acrylic system also shows better resistance to aliphatic hydrocarbon oils, but it is more sensitive to ketone and ester solvents than silicone.

The woven glass scrim changes the failure mode of the backing. Homogeneous skived PTFE tape may elongate by several hundred percent before break; SG33-10(R) generally fails at less than 5% elongation. This low elongation provides stable registration on heated sealing jaws and rotating drums, but it forces the installer to cut relief notches when wrapping radii below approximately 3 mm. The glass scrim also raises tensile strength and cut-through resistance compared with skived PTFE film of similar total thickness. The PTFE encapsulation lowers the backing surface energy to below 20 mN/m, producing a non-stick release face and a coefficient of friction near 0.05–0.10 under ASTM D1894 sled conditions.

Relative to a standard glass-cloth silicone tape, the PTFE encapsulation provides better chemical inertness and a cleaner release face, while the acrylic adhesive avoids silicone-oil migration at the price of lower maximum service temperature. The acrylic PSA is also less effective on low-energy substrates such as untreated polypropylene, polyethylene, or silicone-treated release liners; those surfaces require corona, plasma, or a primer before the tape can achieve structural bond values.

Electrical, Thermal, and Mechanical Limit Conditions

In electrical insulation, the manufacturer-quoted short-time dielectric breakdown of 4.0 kV does not establish a continuous working voltage. A 600 V class winding wrap or interlayer application requires partial-discharge and thermal-endurance evaluation under IEC 60454 or UL 510. PTFE-glass has high surface resistivity, but carbon dust, metallic swarf, or solvent residues can create tracking paths. In varnished coil assemblies, the tape must be tested after impregnation because solventborne varnish can interact with the acrylic interface and reduce shear adhesion during thermal cycling.

The backing tolerates continuous exposure at 260 °C, but the acrylic adhesive does not. At jaw setpoints of 180–200 °C, the adhesive edge may creep if the tape is under shear from product contact, especially when the wrapped edge is on the radius of an L-bar sealing jaw. Mechanical clamps, high-temperature adhesive tie coats, or a fold-over edge are used on production sealers to prevent edge lift. Below −18 °C, the acrylic peel strength decreases and the glass backing remains flexible but can become more brittle at heavily flexed points; low-temperature trials are required for freezer-grade packaging lines.

The PTFE face resists dilute mineral acids, aliphatic hydrocarbons, and most process solvents up to the adhesive temperature limit. It is not compatible with molten alkali metals, elemental fluorine, or chlorine trifluoride at elevated temperatures. The acrylic side is degraded by prolonged immersion in aromatic or ketone solvents, and by plasticizer migration from flexible PVC or amine bloom from freshly cured epoxy surfaces. Such exposure can plasticize the PSA, reduce shear holding power, and leave residue on demounting.

When woven glass scrim replaces skived PTFE in a heated release application

On rotary band sealers operating at 3–5 m/min with jaw temperatures between 150 °C and 180 °C, the PTFE-glass tape is installed with the PTFE face against the polyolefin film. The low-elongation backing prevents stretching and wrinkling that can distort the seal area. Operators observe consistent release of low-density polyethylene when the PTFE face is periodically wiped with isopropanol; wax and slip additives from the film can condense on the release face and increase drag if not removed. Abrasive filler in the film can produce surface whitening of the glass scrim after extended operation, but replacement should be based on physical damage and release degradation rather than colour change alone.

In powder-coat masking of steel and aluminium profiles, the tape is applied to clean metal and placed through a cure cycle of 180–200 °C for 15–20 min. The acrylic adhesive’s edge hold is adequate on straight and gently curved sections, but sharp radii may lift and require die-cut shapes or mechanical hold-down. The PTFE face prevents fusion of the powder coating; however, a silicone-adhesive variant may be selected when repeated cycles exceed 200 °C or when the part remains in the oven for longer than 30 min. The acrylic system tends to leave less post-peel residue than rubber-based masking tapes when removed after cooling below 60 °C.

As a release surface in carbon-fibre/epoxy layup, SG33-10(R) should be used only when the cure temperature and dwell remain within the adhesive limit and when the adhesive is not in direct contact with liquid resin. Published data for this specific configuration is limited; qualification coupons are required to verify that low-molecular-weight acrylic species do not migrate into the resin surface or affect secondary bonding.

Regulatory compliance must be verified against the manufacturer’s material declaration. The product is not automatically food-contact approved; any use in contact with food requires separate assessment under FDA 21 CFR 175.125 or EU 10/2011. The supplier’s REACH declaration under EC 1907/2006 and EU RoHS recast 2011/65/EU are the controlling documents for restricted substances.

Wound components and transformer leads are wrapped with the PTFE face outward to provide a low-friction outer surface and cut-through resistance against copper edges. The acrylic tack permits hand application without heat activation. Adhesion to varnished magnet wire and epoxy-impregnated paper is sufficient for temporary bundling and lead anchoring, but a mechanical tie is required when the assembly is subjected to solventborne varnish dip or thermal cycling because the varnish can plasticize the PSA and reduce shear holding power.