What Does Coefficient Of Thermal Expansion (CTE) Mean?
Coefficient of thermal expansion (CTE) is the ratio of the change in size of a material when its temperature is increased. It's also defined as the fractional increase in length per unit rise in temperature. It's represented as for solids and is measured in inverse Kelvin (1/K) or 1/degrees Celsius. Thermal expansion differs for different materials. Uniform linear objects have thermal expansion proportionate to temperature change.
Trenchless techniques for pipe rehabilitation such as cured-in-place pipe (CIPP) and thermoformed pipe utilize lining materials that expand upon heating and form a close fit to the original pipe.
Trenchlesspedia Explains Coefficient Of Thermal Expansion (CTE)
CIPP utilizes a resin impregnated lining that is inserted into the host pipe and allowed to expand by applying heat. The liner forms a close fit to the host pipe and on cooling hardens. To achieve a tight frictional interface, the liner should use a thermoset resin system with a base resin and hardener that can be cured with ambient temperature.
The resin should have a shrinkage value less than 0.5% when measured as per American Society for testing and Materials (ASTM) D6289. When tested in accordance with ISO 11359-2, over a temperature variation of -30ºC to 30ºC, the cured resin should have a maximum allowable CTE of 100x10-6 /K. Curing at ambient temperature instead of elevated temperature eliminates the influence of CTE.
Plastic pipes used in trenchless technology such as high density polyethylene (HDPE), polyethylene (PE) and polyvinyl chloride (PVC) are also sensitive to temperature change.