Dimensional changes of polyimide films during curing

Creep experiments using small to medium stresses were performed to investigate processes occurring during the cure of PMDA-ODA polyamic acid films to polyimide. The observed dimensional changes originate from thermal expansion, modulus increase or decrease, plastic flow and volume contraction due to solvent loss and chain packing phenomena. The analysis of the experimental data presented confirms the complexation model without excluding the stress limited solvent loss model. A region of actual sample contraction is observed above 180 °C and explained by densification of the polyimide due to packing/ordering.