Consistent and improved measurement of Tg is a critical parameter for polymer composites. Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and Thermo Mechanical Analysis (TMA) are techniques that are used to determine the Tg.

With DMA, the Tg is better defined because of the significant changes observed in mechanical properties that take place; Tg characterisation by DMA is also used in material qualification, processing, manufacturing, as well as for assessing long term performance. However, there is concern regarding the wide variation in the data undertaken by different laboratories for the same material. Choice of analysis options (using storage modulus, loss modulus and tan delta), multiple deformation modes (flexure, tension, compression, shear), thermal lag in the instrumentation are all identified as contributing factors. However, the absence of consistent and traceable temperature calibration was highlighted as a key factor affecting the results.  

The purpose of this project is to assess the metrological traceability and address the factors that influence the data

A two-point calibration protocol will be developed for DMA measurements using reference specimens manufactured embedding metals within carbon fibre composites. The traceability of the measurement will be addressed via an alternative technique (i.e. DSC). This will be a joint activity involving TCMM and TCT and it is planned to extend the study as a global intercomparison exercise.

It is expected that that a measurement note will be developed that will provide best practice guidance and support to global NMIs, industry and academia.