Influence of CNT on the Crystallization Behavior of P(VDF-CTFE) Copolymers
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0949-C03-19
Influence of CNT on the Crystallization Behavior of P(VDF-CTFE) Copolymers Xiaobing Shan, Suiqiong Li, Xin Yang, and Zhongyang Cheng Materials Research and Education Center, Auburn University, Auburn, AL, 36849
ABSTRACT P(VDF-CTFE) based nanocomposites were prepared by mixing the polymer with carbon nanotube (CNT) or C60 using solution cast method. The volume fraction of the CNT or C60 was from 0.1 % to 1.0%. The influence of CNT and C60 on the crystallization behavior of P(VDF-CTFE) was determined using XRD and DSC as well as the P-E loop. It is found that the CNT or C60 enhances the β-phase and the crystallinity. The crystallinity process in the composites was studied using DSC. INTRODUCTION Due to the conversion between electric and mechanical energy, there is a constant effort to develop Electroactive polymer (EAP) for a broad range of application, such as actuators, electromechanical (E-M) and acoustic transducers, artificial muscles and high energy density dielectric capacitors. Among many Electroactive polymers, poly (vinylidene fluoridetrifluoroethylene), P(VDF-TrFE) has been widely studied and used [1, 2, 3, 4]. Comparing with piezoceramics, polymer have many advantages, such as high dielectric strength, flexibility and light weight, however, piezo-polymer, such as P(VDF-TrFE) suffers low strain, low elastic energy density, and low electromechanical conversion efficiency. All those disadvantages have limited their applications. In order to explore and develop Electroactive polymers, a high-energy irradiated P(VDF-TrFE) has been developed, whose electrostriction is about 5%, energy density is above 0.5 Jcm-3 and E-M coupling effect is about 30%. Besides irradiated P(VDF-TrFE), high electrostriction can also be realized by adding a third bulky monomer to form terpolymer, such as P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE). The electrostriction for P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE) are 4% and 4.5% respectively. By irradiation and adding monomer, a defect has been introduced to polymer which can lower the energy barrier between polar phases (β) and none-polar phases (α) [4, 5]. Recently, a high electric energy density and discharge speed have been realized in a new copolymer P(VDF-CTFE), whose energy density can reach as high as 17 J/cm3 [2]. By introducing CTFE, it can expand space lattice and then enable the transformation from α phase to β phase under electric field. FTIR and X-ray studies indicated that such high electrostrictive is related with the molecular conformational change. Besides the conformation change theory and Maxwell stress effect, the study of P(VDF-TrFE-CTFE) terpolymer and P(VDF-CTFE) copolymer indicated that there are some unknown mechanisms responsible for the high electrostriction. It was reported that the nanopolar regions or nanosize crystals in the interfacial layer between crystalline and amorphous regions may contribute to the significant electrostriction [6].
In this paper, in order to better understand the mechanisms related with high electrostriction, the influence o
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