Exploring the caveats associated with estimating the properties of amorphous glassy thermoset

Structural-thermal-mechanical properties are examined for various cross-linked amorphous SU-8 samples via Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), and nanoindentation, respectively. It is found that room temperature FTIR spectra provide less cross-linking (%) estimation than baking temperature spectra due to the mobility effect of polymer chains. DSC results show that glass transition temperature ( T_g) is increasing with the extent of cross-linking (%). However, the correlation of T_g with FTIR measured cross-linking (%) will not be accurate because during DSC characterization sample will undergo cross-linking. From nanoindentation, counter-intuitive results are obtained by the conventional method for reduced elastic modulus ( E_r) and hardness ( H), i.e., decrease with an increase in cross-linking (%). The possible errors, i.e., physical phenomena and methodology, have been analyzed thoroughly for these trends. After minimization/elimination of physical phenomena errors, it is found that current analysis methods are not accurate to estimate E_r and H for glassy polymers.