| Poly(vinylidene fluoride)(PVDF) electrospun fibrous web has the characteristics of soft, light, good permeability and so on. It is the ideal choice of wearable sensors. To study the performance of sensors of PVDF nanofibers film prepared by electropun technology, it is necessary to know the optimal manufacturing conditions for electrospinning and the influence degree of processing parameters. However, there is big difference among the performance of piezoelectricity of PVDF fibrous web due to the use of different spinning process of the preparation of PVDF fibrous web. In addition, the existing research conclusion are mostly based on single factor experiment about the piezoelectricity of PVDF fibrous web, and yet it needs to comprehensively undstand the effect of these processing parameters on the properties of PVDF piezoelectric fibrous web.In order to solve the above-mentioned problems, the control variable method and the orthogonal experiment method were used to improve the design of experiment. In this paper, PVDF fibrous web was fabricated by electrospinning. The beta phase content and crystallinity of the PVDF fibers was characterized by FTIR and XRD test method. The dynamic response of the PVDF fibrous web was tested by a customized piezoelectricity testing device. The results indicated that different processing parameters had different influence on PVDF crystal structure and dynamic responses, and the optimal technology level was obtained by the experiment. Moreover, the different frequency response tests showed the influence of frequency on the dynamic strength of PVDF fibrous web.Specifically, this paper has carried out the following research work.(1) To determine the influence of main processing parameters on the properties of crystal structure of PVDF fibrous web. The control variable method and the orthogonal experiment method for experimental have been designed, and the microstructure has been characterized. The results showed that processing parameters have different impacts on PVDF crystal structure, including the crystallinity and beta phase. The crystal structure has inverted "U" shaped relationship with spinning voltage, and linear regressive relationship with the needle diameter. At the same time, the beta phase content has a linear relationship with spinning speed, whereas the crystallinity is an inverted "U" shaped relationship with it.(2) To define the processing parameters on the effect of dynamic response performance of PVDF fibrous web and the relationship between the content of beta phase and dynamic response ability. The control variable method and the orthogonal experiment have been designed. The results showed that there is an inverted "U" relationship between the dynamic response performance with spinning voltage and spinning speed, and a linear relationship with the needle diameter. At the same time, the effect of spinning speed on beta phase content is different from that of dynamic response.(3) For the explicit influence of excitation frequency on the dynamic peozoelectric intensity of PVDF fibrous web, the same excitation pressure with different frequencies have been applied to the PVDF sample. The response output signal value was setted as an index of characterization of dynamic strength. The results showed that the output signal of the PVDF fiber membrane in a low excitation frequency(<1.0Hz) significantly increased with an increase of frequency. However, in the high excitation frequency(1.0-10.0Hz), the output signal of fibrous web were stable, and no signal increases with the frequency’s change.In a word, this study gave a basic multi-dimentional relationship between the morphology structure and the dynamic response performance with the spinning voltage, spinning speed and needle diameter. Through the research, it obtained the optimal parameter combination about the beta phase content in the highest and the largest dynamic response of PVDF fibrous web. At the same time, the comparison of the the effect law of spinning speed between the beta phase content and the dynamic response showed that only the beta phase content can’t judge the dynamic piezoelectric response performance of PVDF fiberious sheet. In addition, the piezoelectric reposnes of electrospinning PVDF fibrous sheet under the different excitation frequency showed that the PVDF piezoelectric sensors is more suitable for high frequency(>1.0Hz) dynamic pressure monitoring. |
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