Morphology of PEN

In addition to die crystal forms. X-ray scattering studies indicate that when unoriented PEN fiber was drawn at 120 °C ( Tg), a mesophase is generated. In diis form, die molecular chains are in registry with each other in the meridional diiection but not fully ciystallized in die equatorial direction. This conclusion was based on the presence of additional meridional peaks not accounted for by die ciystal sducture obtained by X-ray scattering. The mesophase is a intermediate phase and its existence is strongly dependent upon the processing conditions consequently, it could have implications with respect to the properties of commercially produced fibers and films, since it appears to be stable and not easily converted to the crystalline form, even at elevated temperature [25, 26]. The mesophase stractures of PET, PEN and polyfelhylene naphthalate bibenzoate) were compared by Carr et al. [27]. The phase behavior of PEN and PEN blends widi odier polymers has also been studied [28-32]. 

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An increase in flexural modulus and strength is observed. A heat treatment can further increase their mechanical performance. Already small amounts of graphene change the morphology of PEN from brittle to ductile [51]. 

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