The linear and nonlinear dielectrical and depolarization processes of the copolymer of vinylidene fluoride and trifluoroethylene have been measured. The D vs. E hysteresis loop below room temperature indicates the ferroelectricity of this copolymer. The dielectric anomaly and the disappearance of remnant polarization at T0=70°C suggest that T0 is the phase transition temperature from the ferroelectricity to the paraelectricity phase. Results are analyzed on the basis of Weiss-type semimolecular theory.
Poly(lactic acid) (PLA) is a widely used biomass-derived polymer. It is chiral because the lactic acid monomer has an asymmetric carbon. If the L-lactide is polymerized, then the PLA polymer is an L-type PLA or poly(L-lactic acid) (PLLA); if the D-lactide in PLA is polymerized, then the polymer is a D-type PLA (PDLA). When these polymers undergo drawing or elongation, they exhibit shear piezoelectricity. PLA films are highly transparent and do not exhibit pyroelectricity because of the lack of intrinsic polarization. Therefore, if a PLLA film is used for a touch panel, which is operated by pressure, there is no spurious signal due to heating from the fingers. This suggests that PLLA films may be suitable for touch panels using pressure detection. We used PLLA as the base film of a projected capacitive touch panel with multiple electrodes, and demonstrated a multitouch gesture screen that was sensitive to pressure applied on the screen. This touch panel technology has potential applications for smart phones and tablet personal computers. #
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