A section of clear polymeric tubing failed while in service. The failed sample had been used in a chemical transport application. The tubing had also been exposed to periods of elevated temperature as part of the operation. The tubing was specified to be a polyvinyl chloride (PVC) resin plasticized with trioctyl trimellitate. Investigation included visual inspection, micro-FTIR in the ATR mode, and thermogravimetric analysis. The spectrum on the failed tubing exhibited absorption bands indicative of a PVC resin containing an adipate-based plasticizer. Thermograms of the failed pieces and a reference sample of tubing that performed well showed that the reference material contained a trimellitate-based plasticizer and that the failed material contained an adipate-based material. The conclusion was that the failed tubing had been produced from a formulation that did not comply with the specified material and, as a result, was not as thermally stable as the reference material.

An injection-molded PVC water-filter housing fractured in service. 75x views and visual inspection supported the conclusion that failure occurred due to fatigue crack propagation, as indicated by the presence of discontinuous crack-growth bands and their evolution. However, an initial fissure was believed to have started first due to residual stresses developed during injection molding. No recommendations were made.