PBLG/PMMA 압전 폴리머 복합체의 압전특성 향상 연구

Abstract

Piezoelectric material is the most used active material in underwater transducers. The most common piezoelectric materials in use today are ceramic crystals. Although most ceramics offer high piezoelectricity, they have high mechanical impedance and require expensive processing condition. Piezoelectric polymer is an alternative to ceramic crystals because they are flexible and have lower mechanical impedance ideal for underwater. But they have low and thermally unstable piezoelectric coupling constants. In an effort to develop new piezoelectric polymer with stable piezoelectric properties, Poly-γ-benzyl-L-glutamate Poly methyl methacrylate (PBLG/PMMA) composite polymer film, a new piezoelectric transduction material, was invented by Dawnielle et al. And Hwang have shown that the body composed of this new material can be produced by simultaneous poling and curing of a homogeneous solution comprising poly-γ-benzyl-L-glutamate (PBLG) and methyl methacrylate (MMA) via detachable molding. And, it was also shown that the piezoelectric coefficient (d33) of PBLG-PMMA composite is dependent on the PBLG concentration and the intensity of electric field applied during curing in molds. In this study, the improvement of piezoelectricity of PBLG/PMMA composite was attempted because the piezoelectric coefficient of PBLG/PMMA was only about one twentieth of that of PVDF. In order to improve the piezoelectricity, the PBLG concentration and the electric field intensity applied during fabrication processes are increased and young’s modulus of PLBG/PMMA was decreased. As a result, the piezoelectric coefficient was about 3 times higher than it in previous study. Then, a Tonpilz transducer was designed and fabricated using PBLG/PMMA composite disks in order to investigate the feasibility to apply this composite to acoustic transducers.