Optimized preparation of elastically soft, highly piezoelectric, cellular ferroelectrets from nonvoided poly(ethylene terephthalate) films
Optimized preparation of elastically soft, highly piezoelectric, cellular ferroelectrets from nonvoided poly(ethylene terephthalate) films
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DOI：
10.1002/adfm.200600162
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发表时间：
2007-01-22
影响因子：
19
通讯作者：
Gerhard-Multhaupt, Reimund
中科院分区：
文献类型：
--
作者：
Wirges, Werner;Wegener, Michael;Gerhard-Multhaupt, Reimund
带电荷的多孔聚合物膜可以表现出非常高的压电活性，因此越来越多地用于先进的机电和电声换能器。在本文中，我们报告了一个优化的顺序的步骤，从商业无空隙聚（对苯二甲酸乙二醇酯）（PETP）薄膜通过发泡与CO2双轴机械拉伸，控制空隙膨胀，和双极充电。在适当的高压下，用超临界CO2使无空隙PETP膜发泡，随后退火以稳定。通过在商业拉伸机中良好控制的双轴拉伸以及有时随后在压力室中的燃烧来进一步优化多孔泡沫结构。通过在SF 0气氛中施加高电场，实现了内部空隙的双极充电。新的优化的PETP铁电体表现出相当大的压电系数高达近500 pCN（-1），只有约0.3 MPa的异常低的弹性刚度是必不可少的。PETP泡沫铁电体的非箝位厚度扩展谐振频率在约120和250 kHz之间，因此非常适合于几种已建立的以及新型的超声换能器应用。
Electrically charged cellular polymer films can exhibit very high piezoelectric activity and are therefore more and more often employed in advanced electromechanical and electro-acoustical transducers. In this paper, we report an optimized sequence of steps for preparing such ferroelectrets from commercial nonvoided ploy(ethylene terephthalate) (PETP) films by means of foaming with CO2 biaxial mechanical stretching, controlled void inflation, and bipolar electric charging. The nonvoid PETP films foamed with supercritical CO2 at a suitably high pressure and subsequently annealed for stabilization. The cellular foam structure was further optimized by means of well controlled biaxial stretching in a commercial stretcher and sometimes subsequent inflamation in a pressure chamber. Bipolar electric charging of the internal voids was achieved through the application of high electric fields in an SF0 atmosphere. The new optimized PETP ferroelectric exhibit quite large piezoelectric coefficients up to almost 500 pCN(-1), for which unusually low elastic stiffness of only around 0.3 MPa are essential. The PETP foam ferroelectrics posses unclamped thickenss-extension resonance frequences between approximately 120 and 250 kHz, and are thus highly suitable for several established as well as novel ultrasonic-transductant applications.