What Is High-Temperature Canvas? Types, Materials and Applications

Pipework and ductwork expand and contract as temperature changes. If that movement is not absorbed, connections fail or the seal is lost. High-temperature canvas — a flexible connector — is the heat-resistant fabric joint that absorbs this thermal movement while keeping the system gas-tight. It is also called a canvas joint, flexible joint or expansion canvas.

Why high-temperature canvas is needed

• Absorbs thermal expansion — metal duct expands about 1.2 mm/m per 100°C, risking failure if connected rigidly
• Isolates vibration — stops fan, blower and pump vibration transmitting into ducts and pipework
• Reduces noise — vibration isolation also reduces noise transmission
• Maintains the seal — blocks fluid and gas leakage through expansion and contraction
• Absorbs installation tolerance — compensates for misalignment during installation

Types by material

1. Silicone coated canvas

• Service temperature: −60°C to +300°C (450°C peak)
• Silicone rubber coated onto a glass fiber substrate
• Excellent flexibility and waterproofing, suitable for outdoor installation
• Strong against oil and steam contact
• Colours: red, grey, white
• The most general-purpose high-temperature canvas — the industrial standard
• Uses: industrial duct expansion joints, HVAC systems, incinerator flue joints

2. Teflon coated canvas (PTFE)

• Service temperature: −70°C to +260°C
• PTFE (Teflon) coated onto a glass fiber substrate
• The best chemical resistance — for acid, alkali and solvent contact
• Non-stick — no dust or debris adhesion
• Suitable for connections in food, pharmaceutical and chemical plants
• Colours: white, brown
• Uses: chemical ducts, incinerator exhaust lines, connections in food processing facilities

3. Silica canvas

• Service temperature: ambient to +1000°C (1200°C peak)
• Woven from high-purity silicon dioxide (SiO₂) fiber
• Purely inorganic, withstanding over 1000°C without any coating
• Flexible enough to install on complex shapes
• Excellent acid resistance
• Colours: white to off-white
• Uses: flue joints on incinerators, furnaces and heat-treatment plant, 1000°C-class duct expansion joints

4. Kevlar (aramid) canvas

• Service temperature: ambient to +450°C (600°C peak)
• A high-strength heat-resistant fabric based on aramid (Kevlar®) fiber
• Outstanding tensile strength — the strongest in its class
• Excellent abrasion and cut resistance
• Minimises tearing risk in high-vibration, high-pressure service
• Colour: its distinctive gold
• Uses: high-pressure and high-vibration duct joints, expansion joints in abrasive service, power station flues

5. Ceramic fiber canvas

• Service temperature: ambient to +1260°C
• Woven from ceramic (Al₂O₃ + SiO₂) fiber
• Handles higher temperatures than silica canvas
• Excellent thermal shock resistance — for repeated rapid heating and cooling
• Colour: white
• Uses: flue joints above 1000°C on incinerators, furnaces and petrochemical plant

At a glance

Installation — flanged connection

High-temperature canvas is clamped between the flanges at each end of the duct or pipe and bolted through. The canvas width — the effective movement length — is set by the expected expansion and vibration amplitude of the installation, typically designed between 50 mm and 200 mm. In hot service, using a heat-resistant gasket alongside improves the seal further.

Selection summary

• General industrial ductwork, HVAC and steam lines (below 300°C) → silicone coated canvas
• Pipework in contact with chemicals, acids or alkalis → Teflon (PTFE) canvas
• Incinerator and heat-treatment flues below 1000°C → silica canvas
• High-pressure, high-vibration, abrasive service → Kevlar (aramid) canvas
• Extreme temperature above 1000°C → ceramic fiber canvas
• Outdoor installation exposed to rain → silicone coated (best waterproofing)