Creep effects on CTE measurements of rigid-rod-like polyimides

Abstract

Conventional wisdom demands that measurements of the linear coefficient of thermal expansion (CTE) of thin polyimide film, in thermal mechanical analyzers be conducted under small loads. We show that small loads lead to significant scatter in the data, load variations do not significantly affect the recorded CTE as long as the first and sometimes second thermal cycle does not exceed the glass transition of the polymer film, and experiments under large static loads result in very reproducible CTEs.