Morphological Structure Of PVDF Nanocomposite And The Application Of PVDF Piezoelectric Film In Monitor Of Heart Sound And ECG

Polymer/layered silicate nanocomposites represent a new class of materials with enhanced performance are great academic and industrial interested. The incorporation of nanoscale layers silicate into the polymer matrix has a profound effect on the crystallization behavior and crystalline morphology also improves the thermal and mechanical properties of polymers.Poly(vinylidene fluoride) (PVDF) is one of the polymers which exhibit pronounced polymorphic crystalline forms, depending on crystallization conditions. At least four different crystalline modifications, designated asα,β,γandδ, have been reported thus far. While theα-form is the most common one, theβ-phase is the one that has attracted the widest interest due to its extensive piezoelectric and pyroelectric applications. Many properties of PVDF are improved by the incorporation of microsize inorganic fillers such as SiO2, MgCl2 and MnCl2. Layered silicate has been used as an inorganic filler for nanoscale reinforcement in recent times. It was thought that the nanoscale reinforcement of PVDF in PVDF/ layered silicate nanocomposites would lead to interesting properties.The objective of this investigation was to elucidate the effect of the incorporation of layered silicate on the morphological structure, the crystallization kietics and the properties of PVDF. The morphological structure of the nanocomposites were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR). Differential scanning calorimetry (DSC) were used for the crystallization kietics investigation. The properties were studied by tensile and solve tests.The important results be received by the investigations of the nanocomposites. PVDF/ layered silicate nanocomposites can be successfully prepared by solvent-intercalation and melt-intercalation technique, the melt-intercalation technique is useful for industry. There exist mixed nanostructures with intercalated and exfoliated nanostructure becharacterized by XRD and TEM technique.The dispersion of nanometer silicate layers in PVDF brings about changes in the crystallization behavior. The nanometer-size silicate layers induce heterophase nucleation, but the crystallization growth be comfined by the nanometer-size silicate layers, else. The heterogeneous nucleation effect on silicate layers could accelerate crystallization rate of PVDF. A great number of nucleus generated from the nucleation agent simultaneously grow in a limit space and lead to the formation of small-size crystals. In addition, these nuclei centers will also cause more crystalline defects and confine the movements of polymer chains, which results in producing stress in crystals. So theβphase in PVDF matrix is formed, and that phase is stable even after annealing. The results of this study indicate that PVDF exist in different morphological structure in the two materials, and these differences induce the properties of the two materials are different too. The PVDF/ layered silicate nanocomposites includeβphase of PVDF could be piezoelectric and pyroelectric materials for applications.Obstruct properties and mechanical properties have been effected by the dispersion of nanometer silicate layers in the nanocomposites. The obstruct properties of nanocomposites enhanced clearly using solve tsets. But the tensile tests indicate mechanical properties have no obvious improvements in the nanocomposites.Meanwhile, in clinic application of PVDF piezoelectric film was performed. The PVDF piezoelectric films were prepared by extrusion, stretching and poling in continuous mode and were designed as heart sound transducer for the ambulatory ECG monitor. It is shown that, the heart sound transducer designed by PVDF piezoelectric film has a great many merits, such as highly sensitive, soft, sound impedance matching with human impedance, good chemical stability, smart deign and simple structure.The cardiac actions of 68 patients with cardiac disease were inspected by use of ambulatory ECG monitor designed by ourselves using PVDF piezoelectric film as heart sound transducer. The inspected results were quite consistent with the diagnostic yields detected by Doppler ultrasound system. However, the former smaller, more portable, cheaper, and more suitable for home use than the latter.