Correlation of the cyclic cracked round bar test and hydrostatic pressure test for unplasticized polyvinylchloride. (March 2021)

• Record Type: Journal Article
• Authors: Frank, Andreas; Messiha, Mario; Koch, Thomas; Poduška, Jan; Hutař, Pavel; Arbeiter, Florian; Pinter, Gerald
• Is Part Of: Polymer testing. Volume 95(2021)
• Publication Date: 2021-03
• Subjects: Slow crack growth -- Fracture mechanisms -- Stress intensity factor -- PVC-U -- Pipe -- Material ranking; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2021.107125
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: 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. Highlights: The cracked round bar test allows a quick and sensitive characterization of the SCG resistance of PVC‑U. The slow crack growth resistance of unplasticized polyvinylchloride is highly dependent on the molecular mass. The cycles to failure in the cracked round bar test correlates linear to hydrostatic pressure tests. A failure after 97′000 cycles (2.7 h testing time) in the CRB test correlates to the 1′000 h requirement of EN 1401-1.