Biaxially stretched poly (ethylene terephthalate) (PET), isotactic polypropylene (PE) and isotactic high density poly-propylene (HCPP) films have been characterized by crystallinity, dielectric constant, refractive index and birefringence. Anisotropy of refractive index by microwave for PET, PP and HCPP biaxially stretched films indicated higher value than refractive index by Abbe refractometer. We recognized good correlation between refractive indices by microwave and Abbe refractometer for biaxially stretched PET, PP and HCPP films, respectively.
