PVC is extensively used for municipal water supply/sewage pipes, spouts, profiles, etc., since its mechanical properties such as tensile strength and tensile modulus are better than those of other general purpose olefin plastics, and these products are robust and durable.
When plasticisers are added, PVC shows rubber-like elasticity with high tensile strength and fatigue strength, and can be used for industrial hoses, gaskets, automobile parts, and electric cable covering.
Tensile strength
Fig.1 shows the comparison of tensile strength of PVC products with other plastics. The tensile strength is expressed in terms of the maximum stress per unit area of the cross section when the test piece breaks by applied loads to both ends of the test piece. (An index to show the magnitude of force at break, when both ends of the test piece are pulled apart)
Fig. 1 Tensile strength of various plastics
Tensile modulus
Fig.2 shows the comparison of tensile modulus of PVC products with other plastics. The tensile modulus is also known as the Young’s Modulus, which is expressed in terms of the ratio between the tensile stress per unit area of the cross section and the elongation in the direction of the tensile stress. Plastics possessing large tensile modulus have a small stress-strain ratio. In other words, the tensile modulus is an index showing the magnitude of elongation, when a test piece is pulled apart. It is the equivalent of the spring constant.
Fig. 2 Young's modulus of various plastics
Bending strength
Fig.3 shows the bending strength of PVC products in comparison with other plastics. It is expressed in terms of the maximum stress upon break of the test piece, where the test piece is supported at two points apart and a vertical stress load is applied at the centre. (An index to show the magnitude of force at break, when the test piece is bent).
Fig. 3 Bending strength of various plastics
Compressive strength
Fig.4 shows the compressive strength of PVC products in comparison with other plastics. It is expressed in terms of the maximum stress at break per unit area of the cross section, when a vertical stress is applied to the test piece sandwiched by two pieces of the test panel.
Fig. 4 Compressive strength of various plastics
Fatigue strength
Fig.5 shows the fatigue strength of PVC products in comparison with other plastics. It is expressed in terms of the maximum stress at which the test piece would not break after applying repeated stress for 107 (10 million) times. (The maximum stress, which the test piece can endure after repeated application of an external force).
Fig. 5 Fatigue strenght of various plastics
Impact strength
The glass transition temperature (second order transition point) of PVC is over 70°C. The result is low impact strength at room temperature, which is one of the disadvantages of PVC. There are many ways to measure impact strength. Fig.6 shows the results of energies absorbed by test pieces when they are fixed and hammered to break (impact failure). Higher values show higher impact strength.
Fig. 6 Impact strength of various plastics
