Free volume and damping in a miscible high performance polymer blend: Positron annihilation lifetime and dynamic mechanical thermal analysis studies.

ABSTRACT High performance polymer blend of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) was examined for their free volume behavior at different compositions of PEI using positron annihilation lifetime spectroscopy (PALS). The damping property of the blend was studied using tan-δ obtained from dynamic mechanical thermal analysis (DMTA). The dependence of tan-δ on temperature revealed that the blend is miscible in all compositions, in agreement with earlier studies. The tan-δ peak height is found to increase with increase in free volume fraction for the entire blend composition signifying that the free volume plays an imperative role in understanding the damping property. Using DMTA, master curves were obtained at a reference temperature T₀ by applying the time-temperature-superposition (TTS) using Williams-Landel-Ferry (WLF) relationship. From the shift factor a_T, the WLF coefficients [ABSTRACT FROM AUTHOR]