Moisture absorption analysis of high performance polyimide adhesive

The high temperature resistant polymers and metal composites are used widely in aviation, space, automotive and electronics industry. The high temperature resistant polymers and metals are joined together using high temperature adhesives. Polyimide and epoxy adhesives that can withstand high temperature (200 °C-300 °C) are commonly used for joining high temperature metals and polymers. The performance of adhesively bonded metals and polymers depends upon physical properties of these high temperature adhesives. The physical properties like modulus, Tg. coefficient of thermal expansion (CTE) etc., are affected by external factors such as force, temperature, humidity etc. The external factors play a vital role in the adhesive bond strength and the durability of bond between metal and polymer. In this investigation moisture absorption analysis of polyimide adhesive is performed using Q5000 moisture absorption analyzer. The moisture absorption data of polyimide at different temperatures and humidity level is obtained. Further, the moisture absorption data is fitted to well known Fickian-fit model to determine the diffusion coefficient (D) and saturated moisture gain Msat. Diffusion coefficient (D) and Msat of polyimide and epoxy adhesive are calculated at different temperature and different humidity level. It is observed that diffusion coefficient changes with the change in temperature and humidity level. The diffusion coefficient (D) and M sat data are used in Fick¿s second law of diffusion to estimate the time needed for preconditioning of the adhesively bonded titanium samples in humidity chamber at elevated temperature and higher moisture level. After preconditioning of adhesively bonded Titanium samples in moisture chamber for estimated time, samples will be subjected to lap shear tensile test to study the effect of these elevated conditions on adhesive bond strength.