SThM-based local thermomechanical analysis: Measurement intercomparison and uncertainty analysis

Abstract

We assess Scanning Thermal Microscopy (SThM) with a self-heated doped silicon nanoprobe as a method for determining the local phase transition temperature of polymeric materials by means of nano-thermomechanical analysis (nano-TA). Reference semi-crystalline samples and amorphous test samples, characterized first using differential scanning calorimetry (DSC), are studied by nano-TA in the temperature range 50–250 °C. The repeatability, the reproducibility and the reliability of nano-TA are evaluated by three laboratories by applying the same calibration protocol prior to and after the measurements. The calibration of the probe temperature scale and the variability of the sample thermomechanical response are validated by Monte Carlo uncertainty analysis, resulting in a calculated uncertainty between 3 and 5 K. The SThM probe temperature data represented as a function of DSC-measured phase-transition temperatures of the semi-crystalline samples rule out the possibility of a quadratic fit and call for a linear calibration in absence of additional information. The maximum deviation obtained between SThM and DSC temperatures with such linear calibration reaches ± 30 K for melting temperatures and 50 K for glass transition temperatures.