Capacitors are two terminal devices for energy storage. Polymers like biaxially oriented polypropylene (BOPP), polyethylene terephthalate (PET) are widely used in capacitor applications because of their good properties such as low cost, high dielectric strength and low loss. State of art of polymeric dielectric films are biaxially oriented polypropylene with breakdown strength of 600-700 V/µm (for 10 µm thickness) and with dielectric constant of ~2.21,2. Various strategies have been used to increase the dielectric constant and the dielectric strength of polymeric dielectrics. One of them is to orient crystalline domains of polymers to make a torturous path, by applying mechanical deformation in semi-molten state. However, it is challenging to understand the polymer responses under deformation. In this research, two different blends are investigated; PEI (polyether imide)/PBT (polyethylene terephthalate) and PEI/PET. PBT and PET which are semi crystalline thermoplastic polymers, blended with different ratios of PEI which is an amorphous thermoplastic polymer with Tg ~2200C for high temperature applications. By doing so, processability of PBT also increased. It is found that up to 70/30 (PEI/PBT) blend can still crystallize on the other hand for PEI/PET above 30 % PEI the blend crystallizability disappears. In the absence of orientation, the increase of PEI fraction leads to decrease of crystallizability as expected from the dilution effect that spatially prevents the crystallizable polymer chains from coming together. Blends with high PBT & PET amount can be stretched more and during stretching in blends, amorphous orientation takes place rapidly, followed by crystallization. (1)Barshaw, E. J.; White, J.; Chait, M. J.; Cornette, J. B.; Bustamante, J.; Folli, F.; Biltchick, D.; Borelli, G.; Picci, G.; Rabuffi, M. IEEE Trans., Magn. 2007, 43, 223−225. (2)Offenbach, I.; Gupta, S.; Chung, T.; Weiss,R.A.; Cakmak M., Macromolecules, 2015 48, 6294-6305