AbstractThe melt rheology of commercial poly‐ε‐caprolactam/polypropylene blend, Orgalloy R‐6000 was studied by a number of university, industrial, and government laboratories as part of the Versailles Project on Advanced Materials and Standards (VAMAS), Technical Working Party on polymer blends round‐robin research program. The objective of the organization is to facilitate the development of standard test methods for the characterization of such complex materials. The program was established to evaluate proposed test methods for characterization of the melt rheology of commercial blends. Orgalloy R‐6000 was studied in both shear and extensional flows. A number of the laboratories also compared its rheology to that of a polypropylene and a polyamide that are similar to those that were used to produce it. This material showed all the viscoelastic properties expected of molten thermoplastics but was found to be significantly more elastic than its constituent materials. The poor quantitative agreement of the interlaboratory results indicate that improvements in the standardization of test methodologies and sample conditioning for such hydroscopic materials is necessary.