In this study, we attempt to prepare a new blending system of poly（vinylidene fluoride） （PVDF） and aliphatic polyketone （POK） by melt compounding, The latter is a promising engineering plastic with comprehensive...In this study, we attempt to prepare a new blending system of poly（vinylidene fluoride） （PVDF） and aliphatic polyketone （POK） by melt compounding, The latter is a promising engineering plastic with comprehensive mechanical performances. When POK acted as minor phase to homogeneously disperse in and intimately contact with PVDF matrix, the brittle tensile behavior of neat PVDF transferred into a remarkably flexible manner （the elongation at break increased for 20 times）, and more interestingly, the room- temperature durability of β-form PVDF in the uniaxially drawn blend film was obviously better than that in the neat PVDF film. Fourier transform infrared spectroscopy revealed that specific dipole interaction existed between CF2 group of PVDF and C=O group of POK. The intermolecular dipolar interaction induced good compatibility in the PVDF/POK blends, as evidently proved by fine two-phase morphology and decreased melting points of POK crystals. Therefore, the good compatibility and interracial enhancement are responsible for the improvement of the stretch ductility and β-form room-temperature durability of the PVDF/POK blends.展开更多
Polymer nanocrystal composites were fabricated by embedding polyvinylidene fluoride (PVDF) with K0.5Na0.5NbO3 (KNN) nanocrystallites of different volume fraction using the hot-pressing technique.For comparison,PVDF-KN...Polymer nanocrystal composites were fabricated by embedding polyvinylidene fluoride (PVDF) with K0.5Na0.5NbO3 (KNN) nanocrystallites of different volume fraction using the hot-pressing technique.For comparison,PVDF-KNN microcrystal composites of the same compositions were also fabricated which facilitated the studies of the crystallite size (wide range) effect on the dielectric and piezoelectric properties.The structural,morphological,dielectric,and piezoelectric properties of these nano and micro crystal composites were investigated.The incorporation of KNN fillers in PVDF at both nanometer and micron scales above 10 vol％ resulted in the formation of polar β-form of PVDF.The room temperature dielectric constant as high as 3273 at 100 Hz was obtained for the PVDF comprising 40 vol％ KNN nanocrystallites due to dipole-dipole interactions (as the presence of β-PVDF is prominent),whereas it was only 236 for the PVDF containing the same amount (40 vol％) of micron-sized crystallites of KNN at the same frequency.Various theoretical models were employed to predict the dielectric constants of the PVDF-KNN nano and micro crystal composites.The PVDF comprising 70 vol％ micron-sized crystallites of KNN exhibited a d33 value of 35 pC/N,while the nanocrystal composites of PVDF-KNN did not exhibit any piezoelectric response perhaps due to the unrelieved internal stress within each grain,besides the fact that they have less domain walls.展开更多
The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differentia...The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differential scanning calorimetry(DSC). The βphase of PVDF was observed after quenching from the melt and further annealing above the glass transition temperature over a composition range. The PVDF/PEMA blend with weight ratio of 3:2 has formed higher content of PVDF β crystals than others. By taking advantage of fast cooling rate of ultrafast differential scanning calorimeter(UFDSC), the quenching process of blends was modeled and tested simultaneously, and the melting behavior of β crystals in all blends was investigated. Three types of crystallization behavior of βphase PVDF in blends were found after quenching-annealing at different temperatures.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 51373108 and 21574088)
文摘In this study, we attempt to prepare a new blending system of poly（vinylidene fluoride） （PVDF） and aliphatic polyketone （POK） by melt compounding, The latter is a promising engineering plastic with comprehensive mechanical performances. When POK acted as minor phase to homogeneously disperse in and intimately contact with PVDF matrix, the brittle tensile behavior of neat PVDF transferred into a remarkably flexible manner （the elongation at break increased for 20 times）, and more interestingly, the room- temperature durability of β-form PVDF in the uniaxially drawn blend film was obviously better than that in the neat PVDF film. Fourier transform infrared spectroscopy revealed that specific dipole interaction existed between CF2 group of PVDF and C=O group of POK. The intermolecular dipolar interaction induced good compatibility in the PVDF/POK blends, as evidently proved by fine two-phase morphology and decreased melting points of POK crystals. Therefore, the good compatibility and interracial enhancement are responsible for the improvement of the stretch ductility and β-form room-temperature durability of the PVDF/POK blends.
文摘Polymer nanocrystal composites were fabricated by embedding polyvinylidene fluoride (PVDF) with K0.5Na0.5NbO3 (KNN) nanocrystallites of different volume fraction using the hot-pressing technique.For comparison,PVDF-KNN microcrystal composites of the same compositions were also fabricated which facilitated the studies of the crystallite size (wide range) effect on the dielectric and piezoelectric properties.The structural,morphological,dielectric,and piezoelectric properties of these nano and micro crystal composites were investigated.The incorporation of KNN fillers in PVDF at both nanometer and micron scales above 10 vol％ resulted in the formation of polar β-form of PVDF.The room temperature dielectric constant as high as 3273 at 100 Hz was obtained for the PVDF comprising 40 vol％ KNN nanocrystallites due to dipole-dipole interactions (as the presence of β-PVDF is prominent),whereas it was only 236 for the PVDF containing the same amount (40 vol％) of micron-sized crystallites of KNN at the same frequency.Various theoretical models were employed to predict the dielectric constants of the PVDF-KNN nano and micro crystal composites.The PVDF comprising 70 vol％ micron-sized crystallites of KNN exhibited a d33 value of 35 pC/N,while the nanocrystal composites of PVDF-KNN did not exhibit any piezoelectric response perhaps due to the unrelieved internal stress within each grain,besides the fact that they have less domain walls.
基金financially supported by the National Natural Science Foundation of China (Nos. 21474049, 51673094 and 21404055)Tianshan Scholars Program by Yili Normal Universitythe Shenzhen Science and Technology Innovation Committee (Nos. JCYJ20160608140827794, JCYJ20160531151102203 and JCYJ20170818110206085)
文摘The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differential scanning calorimetry(DSC). The βphase of PVDF was observed after quenching from the melt and further annealing above the glass transition temperature over a composition range. The PVDF/PEMA blend with weight ratio of 3:2 has formed higher content of PVDF β crystals than others. By taking advantage of fast cooling rate of ultrafast differential scanning calorimeter(UFDSC), the quenching process of blends was modeled and tested simultaneously, and the melting behavior of β crystals in all blends was investigated. Three types of crystallization behavior of βphase PVDF in blends were found after quenching-annealing at different temperatures.
