Interlaboratory tests on polymers by differential scanning calorimetry (DSC): Determination of glass transition temperature (Tg)

Abstract

The present report presents results obtained from an interlaboratory test. 28 participants, mainly from industry and research institutes, measured glass transition temperatures (Tg) by differential scanning calorimetry (DSC) on four different polymers. The materials used were poly(methyl methacrylate) (PMMA), polycarbonate (PC), polysulfone (PSU) and amorphous polyamide (PA 6I/6T). The measured data were collected by EMPA and were evaluated using a robust statistical method. Repeatability and reproducibility data were of special interest. The repeatability limit (r) of glass transition temperatures measured according to DIN 53765 was found in the region of 1-2°C, and the reproducibility limit (R) was around 3-4°C. In addition to the DIN standard, the set of interlaboratory test data was evaluated and considered according to some different approaches and was correlated with data from other EMAP interlaboratory tests performed previously. It was shown that the investigated statistical parameter was always in a similar dimension. The data of the PA sample were found to be an exception. Due to the hygroscopic character of polyamide, the r and R values increase sharply, to an almost three times higher reproducibility limit. Overall, the evaluated data can be used to estimate the results of own and external Tg measurements and their compatibility. The report should therefore support daily work in analytical laboratories where glass transition temperatures are measured by DSC.