Internal pressure resistance
Parallel standards to ISO 12230 exist which present the effect of time and temperature on the expected strength of PE-X (ISO 10146), PP-H, PP-R and PP-B (ISO 3213) and PE-RT (ISO 24033). These standards provide the basic data for the four respective piping systems standards, namely ISO 15876 for Polybutene-1, ISO 15875 for PE-X, ISO 22391 for PE-RT and ISO 15874 for the three types of polypropylene. The data presented in these standards provides a useful means of comparison of the performance of these three alternative plastic materials The following figure shows the performance reference lines for Polybutene-1, PE-X, PP-R and PE-RT at 70°C on an equivalent scale. After 10 years' exposure to continuously applied stress, Polybutene-1 retains 40% more strength than PE-X and almost double that of PP-R and PE-RT.

Design stress
By employing standardised dimensional criteria presented in ISO 10508 it is possible to calculate the maximum allowable hoop stress of these alternative polyolefin pipes for the various standardised applicational temperature classes. This calculation results in the comparisons presented in the table below where it is shown that the maximum allowable hoop stress for Polybutene-1 pipes is some 35% higher than for cross-linked polyethylene PE-X pipes, 45% higher than for polypropylene PP-R pipes and more than 50% higher than for non cross-linked PE-RT pipes. This effectively means that at equivalent thickness, Polybutene-1 pipes offer a significant safety factor over these alternative plastic materials for installed systems.