Polyimide belongs to a family of heat resistant polymers. One of them is aromatic polyimide. Aromatic polyimide sheets have outstanding electrical insulation, solvent resistance and mechanical properties along with the maximum thermal resistance property among organic polymers. Few of aromatic polyimide is a polyimide that is prepared from bis ether that is 4- amino phenyl ether and pyromellitic dianhydride that is vespel, kapton which are products of a cooperation. Another is a polyimide that is prepared from bis ether that is 4- amino phenyl ether and 3, 3’, 4, 4’-biphenyltetracarboxylic dianhydride that is ubilex, a product of ube industries cooperation.

Heat melting of this polyimide is not that easy, therefore, these polyimides are developed by casting a polyamic acid precursor initially into a form of sheet and then running a heat imidization reaction. In the solvent removal step, there is a rate determining stage in the preparation process. The imidization step is not good in productivity and requires further a solvent recovery stage. As a result, this process is not favorable economically. Polyetherimide is developed as another polyimide that has thermo plasticity. This uses melt extrusion process to prepare a sheet. Although, the sheet that is prepared using polyetherimide is not much satisfactory in its chemical and heat resistance.