The temperature effects on high density polyethylene (HDPE)‎ pipes

الملخص EN

The mechanical characteristics and properties of HDPE gipes are highly affected by the environmental conditions.

In this investigation the influence of temperature on the mechanical characteristics (i.e., stress-strain) curves as well as the viscoelastic properties of these tubes is examined.

A range of testing temperatures of 23 to 80°C is covered for HDPE pipes of both classes (3) and (5) with working pressures of 4 and 10 bars respectively.

Various pipe sizes ranging from 16 to 32 mm are investigated.

In this investigation, mainly, the standard Japanese axial tensile test (JIS K6761) is employed.

The results of this investigation show that all pipes tested exhibit temperature sensitivity to varying degrees (i.e., decreased resistance to deformation as the temperature is increased) regardless of the pipe size and class.

All the mechanical properties of these tubes except for ductility are decreased non-linearly as the testing temperature increases.

The values of the yield stress, tensile strength, modulus of elasticity, and specific work are found to be degraded by about 45 to 60% over the tested range of temperatures.

Generally, the pipes of class (5) are found to be superior to pipes of class (3) in all their mechanical properties over the whole testing range of temperatures.

Finally, polymer degradation problem is discussed, including its principles, causes, mechanisms and factors affecting this phenomena.

Also, the thermal and mechanical degradation types of HDPE pipes in particular are discussed and presented.