Abstract: | Wallace plasticity and the weight‐average molar mass (Mw) were measured on natural rubber samples of different origins. A sigmoidal model describes the relations between Wallace plasticity and Mw (0.872 > r2 > 0.992) for given families of samples. The families of samples analyzed differed through their clonal origin, collection method (cup lumps or latex), and type of processing (CV or non‐CV). This study showed that two samples of natural rubber can be identical in terms of plasticity, but very different in terms of the average polyisoprene chain length or Mw. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3078–3087, 1999 |