Evaluation of different specimen geometries and testing configurations for the assessment of the degree of gelation of unplasticized poly(vinyl chloride) pipes using the essential work of fracture approach

Abstract

An unplasticized (U-PVC) pipe sample (ABNT NBR 5647-2, nominal diameter DN 100, outside diameter 110 mm) is studied using essential work of fracture (EWF). This pipe sample is also tested for the quality of processing (degree of gelation) via differential scanning calorimetry (DSC) and tensile strength. The comparative evaluation of different specimen configurations – flat (SENB) and curved (CTPB) specimens in three-point bending, using different support spans, and C-shaped (SNRB) and full rings in tension (SNRT), shows significant differences in their suitability for EWF testing. While SENB- and CTPB-type specimens, independently of the support span ratio S/W adopted, confirm previous findings that both specimen configurations are very suitable for EWF testing of pipe samples, SNRB- and SNRT-type specimens, by their turn, do not show suitability for the purposes of this study, at least using the testing configurations here adopted. When comparing results from this study with previous publications from the authors, it is shown that EWF seems to be an interesting alternative approach for gelation assessment, since it is evident from the comparative results that there is some high degree of correlation between EWF parameters and the DSC degree of gelation.