Effect of fast electron irradiation on the dielectric and pyroelectric response of radially-oriented PVDF film
Radiation-induced functionalization of ferroelectric P(VDF/TrFE) copolymers was found to be effective in production of polymer relaxors attractive for applications. We studied radiation-induced changes in the dielectric relaxation and pyroelectric response of radially oriented PVDF film irradiated with electrons of energies 0.5-1.5 MeV. Radiation damage to the samples was characterized by ESR and IR spectroscopy. An increase in activation energy of segmental motion of the polymer and a downward shift of the freezing temperature of segmental motion and the Curie temperature, induced by electron irradiation, was related to a damage in all-trans conformation of the polymer chain and formation of polar regions.
The photopyroelectric method in a non contact detection configuration is proposed to study water migration in starch sheets. This allows the exchange of humidity between the moist atmosphere and the starch sample during the experiment. The sensitivity for the total water content measurement was about 0.3%. A theoretical model was developed, taking into account a continuous depth profile of humidity in the starch sample. A water profile in the material and its evolution in time were evidenced when exposing one side of the sample to a humid atmosphere.