The applicability of the cracked round bar (CRB) test according ISO 18489 for the characterization of slow crack growth (SCG) in unplasticized polyvinylchloride (PVC–U) was analyzed by testing three PVC-U pipe compounds with different molecular mass, represented by different intrinsic viscosity numbers (K-values). The tests were conducted at lower stress loading ranges than recommended by the standard. The SCG resistance showed a clear dependency on the K-value resulting in a higher crack resistance with increasing K-value. Moreover, the results of the CRB tests were correlated to hydrostatic pressure tests of PVC-U pipe grades with different K-values. A clear linear correlation between the results of both methods was established, thereby demonstrating a significant acceleration of testing times with the CRB test. With a special focus on EN 1401–1, it was elaborated that the requested minimum failure resistance of 1′000 h in the hydrostatic pressure test at T = 60 °C correlates to 97′000 cycles, or 2.7 h, respectively, in the CRB test at T = 23 °C.
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