Saint-Gobain CHR G565 is identified by its construction as a woven glass cloth backing tape with a silicone pressure-sensitive adhesive. The product is used in high-temperature masking, electrical insulation, thermal spray protection, and general splicing operations where room-temperature handling is followed by exposure to ovens, hot-air cycles, or impingement media. The glass cloth backing contributes tensile strength, cut-through resistance, and slit-edge stability. The silicone adhesive contributes peel adhesion with a broader temperature range than acrylic or rubber systems. Product dimensions, adhesion to specific substrates, and electrical properties are defined by the current Saint-Gobain technical data sheet and the batch-specific certificate of analysis. Test methods commonly referenced for this product class include ASTM D3330/D3330M for peel adhesion, ASTM D3759/D3759M for tensile strength and elongation, ASTM D1000 for pressure-sensitive adhesive tape test methods, and IEC 60626 for electrical insulating materials. CHR G565 is commercially supplied as log rolls and slit rolls; slit-edge quality and winding tension affect automated die-cutting and manual application on profiled parts.

What Distinguishes CHR G565 from Acrylic, Rubber, and Polyimide Tape Systems?

The silicone adhesive is the primary differentiator. Silicone pressure-sensitive adhesives are formulated from siloxane polymers and silicate resin tackifiers, producing a viscoelastic response that remains useful at temperatures where acrylic and rubber adhesives soften or crosslink excessively. Acrylic systems typically exhibit severe softening above 120 °C, while natural rubber adhesives can degrade at lower temperatures. Silicone adhesive glass cloth tapes are generally specified for continuous service in the 180 °C to 200 °C range, with short-term excursions dependent on dwell time, air flow, and substrate thermal mass. The glass cloth backing distinguishes CHR G565 from polyimide tape. Polyimide offers lower profile and smoother surface, but it has lower abrasion resistance and greater susceptibility to cut-through in coil winding. Compared with polyester-backed silicone tapes, CHR G565 has higher thermal capability and lower elongation at break, but the woven backing produces a higher profile and requires more application time on compound contours.

Compared with PTFE-coated glass cloth tapes, CHR G565 has no fluoropolymer top layer. PTFE-coated products are selected when a low-friction, nonstick surface is required. CHR G565 is selected when fluoropolymer contamination is unacceptable but the woven glass and silicone adhesive combination is still compatible with the process. Silicone pressure-sensitive adhesives can transfer trace siloxane residues to some substrates after heating. For coating or adhesive bonding operations, surface-energy checks or X-ray photoelectron spectroscopy may be required after process trials to verify that no contaminating silicone transfer remains on the masked surface.

For applications requiring paint overspray resistance, the glass cloth backing provides a rough surface that traps dry overspray and reduces flaking. Smooth film backings can allow overspray to crack and generate particles. This difference is significant in powder coating and liquid painting booths. The woven structure also provides a mechanical key for some coating adhesion; however, the product is intended as a removable mask, not as a permanent adhesion promoter or coating substrate.

The silicone adhesive may undergo oxidative crosslinking rather than chain scission at cure temperatures. Residue after overheating often appears as a brittle film rather than a tacky smear. The governing variables are oven temperature, dwell time, air velocity, and substrate thermal mass. Heavier substrates with longer ramp times expose the adhesive to a longer integrated thermal history than light parts, even when the peak metal temperature is identical. This thermal history difference can change clean-removal performance on otherwise identical powder coating lines.

When G565 Enters a Powder Cure Oven at 200 °C

Powder coating operations employ glass cloth silicone tape as a masking medium. The tape is applied after cleaning and pre-treatment and before electrostatic powder application. The silicone adhesive is selected because it maintains peel adhesion on phosphate or silane-treated metal surfaces and can be removed after the cure cycle without heavy residue, provided the oven profile does not exceed the adhesive’s upper limit. During a conventional cure at a peak metal temperature of 200 °C for 10 min to 30 min, the glass cloth backing remains dimensionally stable. The silicone adhesive may undergo additional crosslinking; this can reduce residue transfer if the profile is controlled, but excessive cure above 260 °C can embrittle the adhesive and increase residue. The actual operating limit for CHR G565 should be confirmed against the current product data sheet because time-at-temperature and air flow influence adhesive degradation.

Field data from batch convection ovens and continuous belt ovens indicate that edge lifting is the most frequent failure mode on inside radii below 3 mm and on seams where the tape has been stretched during application. Application tension should be limited to avoid necking the woven glass backing. Because glass cloth is anisotropic, slit strips should be oriented so that the higher tensile direction follows the mechanical load during handling. Peel adhesion after conditioning at process temperature is more relevant than room-temperature tack. The tape should be applied to a clean, dry surface; moisture, oils, and loose phosphate dust reduce adhesive contact and produce premature lifting. A minimum room-temperature dwell before powder application is common practice because silicone adhesives build adhesion through wetting. The required dwell time is process-dependent and should be determined by peel trials on the production line.

Silicone adhesive transfer to powder-coated surfaces is evaluated by visual inspection under UV light or by water-break-free testing. If transfer is observed, the cure cycle, tape age, and application tension should be reviewed before changing to a different tape class. Bake-off residue testing can be performed on the actual substrate by subjecting a small masked panel to the production cure profile and measuring the contact angle or surface energy of the previously masked area. This approach is more reliable than laboratory peel data alone because it includes the effect of pre-treatment chemicals and surface roughness.

Dielectric Withstand and Mechanical Integrity at Elevated Process Temperatures

The woven glass cloth backing provides mechanical strength, cut-through resistance, and thermal stability. In electrical insulation service, the tape is subjected to winding tension, varnish impregnation, and thermal cycling. The relevant property set includes tensile strength, elongation at break, dielectric breakdown voltage, and resistance to varnish solvents. These properties are evaluated according to ASTM D3759/D3759M for tensile properties and ASTM D149 for dielectric breakdown voltage. Because dielectric breakdown is thickness-dependent and electrode-dependent, a published value for a similar glass cloth silicone product is not a valid substitute for CHR G565. The manufacturer’s technical data sheet should be consulted for the exact grade, thickness, and test conditions.

The table below lists the test methods commonly used to qualify glass cloth silicone tapes for masking and electrical service. The table does not provide design values for CHR G565 because those are controlled by the manufacturer’s published specification and the batch-level certificate of analysis.

For automated masking, slit-edge quality and roll winding are as important as bulk properties. A poorly slit edge generates fiber pull-out and adhesive transfer to cutting dies. The use of hard-shell cores and controlled winding tension reduces telescoping and edge damage. Incoming inspection often includes measurements of roll width, splice count, and unwind force. These properties are not standardized at the product level but are typically agreed between converter and end user in a quality agreement.

Plasma Spray Masking and Grit Blast Edge Lifting

Thermal spray masking is a more severe application than powder coating. During plasma spray or HVOF, the tape is exposed to reflected heat, high-velocity particles, and occasional direct plume contact. The glass cloth backing provides erosion resistance and particle impingement protection that a film backing cannot match. The silicone adhesive retains some peel strength at the elevated substrate temperatures produced by the spray process, but direct flame or plasma impingement will char the backing and adhesive. The tape is intended as a sacrificial mask, not as a permanent thermal barrier. Multi-layer applications or metal shields are required for long production runs.

Grit blasting of masked surfaces can lift the tape edge if the blast direction is opposite the application edge. This is a known failure mode in surface preparation before thermal spray. The tape should be applied with its leading edge away from the blast direction or protected by a secondary metal shroud. Edge lifting increases as grit size and blast pressure increase. Adhesive residue after exposure to high temperature is evaluated by solvent wipe and surface energy testing, because silicone contamination can reduce the adhesion of subsequent coatings. Published data for CHR G565 under specific plasma spray parameter sets is limited; process qualification should record standoff distance, traverse speed, number of passes, substrate temperature, and carrier air pressure.

Regulatory compliance should be confirmed against the manufacturer’s current statement for REACH SVHC and RoHS Directive 2011/65/EU Annex II. Glass cloth and silicone pressure-sensitive adhesive systems are generally halogen-free; however, if a halogen-free declaration is required for a specific application, the exact backing and adhesive formulation should be verified against the supplier’s certificate of conformance. Food-contact status should not be assumed; where indirect food contact is relevant, the appropriate FDA or local food-contact regulation must be reviewed for the specific product grade and thickness.