Effect of temperature on tensile properties of HDPE pipe material

The properties that make plastic of direct interest to designers and engineers are its good strength to weight ratio, low manufacturing and installation costs and high durability. The strength of polymers is known to be sensitive to temperature and this generally limits their use under service temperatures lower than the glass transition temperature. The present work addresses the effect of temperatures ranging from -10 to 70°C on the tensile properties of high density polyethylene PE-100 pipe material. Tensile tests are performed on dog bone type ASTM standard specimens. Yield stress and modulus of elasticity are found to decrease linearly with temperature. The average yield strength decreased linearly from 32 to 9 MPa when the temperature is increased from -10 to 70°C. The modulus of elasticity varied in the same fashion as the yield strength. The yield strain, however, showed a slight increase in this temperature range. Ductile fracture is observed to be the controlling failure mechanism at all the temperatures of interest. The deformation at room and high temperatures is accompanied by considerable necking. The temperature effect on the tensile properties of PE-100 pipe material is compared with that of CPVC and PVC pipe materials, used in comparable applications. In general, a similar effect was observed on yield stress, modulus of elasticity and yield strain in all these materials.