Glass cloth tape is a woven fibreglass fabric tape coated with silicone or acrylic adhesive, rated for temperatures up to 200 degrees Celsius (silicone adhesive) or 130 degrees Celsius (acrylic adhesive). It is used for transformer insulation, motor coil wrapping, cable bundling in high-temperature environments, and thermal protection in industrial equipment.
Introduction
Glass cloth tape is the workhorse insulation tape for high-temperature electrical applications. When standard PVC or polyester tapes cannot handle the heat, glass cloth tape provides reliable insulation, mechanical strength, and flame resistance at temperatures that would destroy other tape materials.
Made from woven fibreglass fabric, glass cloth tape combines the thermal resilience of glass fibres with the convenience of pressure-sensitive adhesive application. This guide covers the properties, types, and applications that make glass cloth tape essential in transformer manufacturing, motor insulation, and industrial thermal protection.
What is Glass Cloth Tape Made Of
The backing material is a woven fabric made from E-glass fibres, the same glass fibre type used in fibreglass composites. E-glass provides excellent tensile strength, dimensional stability, and thermal resistance. The weave pattern, typically plain weave or satin weave, determines the tape conformability and surface smoothness.
The adhesive is usually silicone-based for high-temperature applications or acrylic-based for moderate-temperature uses. Silicone adhesive maintains its bond at temperatures up to 200 degrees Celsius. Some specialised grades use thermosetting adhesives that cross-link during baking, creating a rigid insulation barrier.
Key Properties of Glass Cloth Tape
| Property | Glass Cloth + Silicone | Glass Cloth + Acrylic | Why It Matters |
|---|---|---|---|
| Temperature Rating | Up to 200 °C continuous | Up to 130 °C continuous | Determines application suitability |
| Dielectric Strength | 5,000–7,000 V/mil | 5,000–7,000 V/mil | Electrical insulation capacity |
| Tensile Strength | High (90+ N/25mm) | High (90+ N/25mm) | Resists tearing during wrapping |
| Flame Resistance | Self-extinguishing | Self-extinguishing | Safety in electrical failures |
| Chemical Resistance | Good | Good | Resists varnish, oils, solvents |
| Conformability | Moderate (depends on weave) | Moderate | Wraps around coils and irregularities |
| Moisture Resistance | Good | Good | Protects insulation in humid environments |
Types of Glass Cloth Tape
Standard Glass Cloth Tape (Silicone Adhesive)
This is the most common type, used for Class H (180 °C) insulation in transformers and motors. The silicone adhesive provides clean, non-corrosive bonding that maintains performance through temperature cycling. Available in standard thicknesses of 0.13mm to 0.25mm.
Varnish-Compatible Glass Cloth Tape
Some glass cloth tapes are designed to be compatible with impregnating varnishes used in motor and transformer manufacturing. The tape resists varnish penetration during the vacuum pressure impregnation (VPI) process, maintaining its insulation integrity.
Self-Adhesive vs Non-Adhesive Glass Cloth Tape
Self-adhesive versions have silicone or acrylic PSA for easy application. Non-adhesive glass cloth tape is used where the tape will be secured by varnish impregnation or overwrapping rather than adhesive bonding.
Applications of Glass Cloth Tape
Transformer Insulation
Glass tape for transformers is the primary insulation tape for transformer coil winding. It is applied between winding layers and as outer wrap insulation. The combination of high dielectric strength, temperature resistance, and mechanical toughness makes it essential for power transformer manufacturing.
Electric Motor Insulation
Motor manufacturers use glass cloth tape for slot insulation, phase insulation, and coil end wrapping. Class H motors operating at 180 degrees Celsius require glass cloth tape with silicone adhesive to maintain insulation integrity over the motor service life.
Industrial Thermal Protection
Beyond electrical applications, glass cloth tape provides thermal protection on industrial equipment, piping, and exhaust systems. It wraps around hot surfaces to protect adjacent components, wiring, and personnel from heat exposure.
Cable Bundling in High-Temperature Areas
In environments where temperatures exceed the limits of PVC or polyester tape, glass cloth tape bundles and protects cables. It is used in furnaces, ovens, kilns, and industrial process equipment where ambient temperatures require insulation tape rated above 150 degrees Celsius.
Adhesive Specialities Glass Cloth Tape Products
Adhesive Specialities manufactures glass cloth tape with silicone and acrylic adhesive for transformer, motor, and thermal insulation applications. Explore our electrical tapes category for related products. For applications above 200 °C, consider our polyimide tape — see our comparison guide for selection guidance.
