Correlation Between Microscale Indentation Creep and Macroscale Tensile Creep of PLA/PCL Polymer Blends

This study investigates the relationship between microscale indentation creep and macroscale tensile creep of immiscible polymer blends. Micro- and macroscale creep were measured across the full composition range of model poly(lactic acid)/poly(caprolactone) blends (PLA/PCL), using indentation loadings of 50 and 300 gf and a tensile loading of 2 kg. The creep data were fitted with the empirical power law (PL) model and three phenomenological elasto-visco-plastic (EVP) models implemented in our open-source Python package MCREEP (version 1.1.6). Traditional creep descriptors, such as indentation creep (C_IT) defined by ISO standard or the creep exponent (n) from the well-established empirical PL model (deformation = C·tⁿ), yielded inconsistent or even misleading results. However, detailed analysis of the creep curves showed that alternative creep descriptors, such as the total deformation corrected for the initial deformation, exhibited the same trends at the micro- and macroscale and strong linear correlations (R² > 0.97). These findings demonstrate that short-term microindentation creep can predict the ranking of macroscale creep behavior in polymer blends, provided that suitable creep descriptors are employed.