In the present work, magnetite (Fe<sub>3</sub>O<sub>4</sub>) nanoparticles have been prepared by a simple chemical method. Polymer nanocomposites based on the blend between poly vinylamine fluo...In the present work, magnetite (Fe<sub>3</sub>O<sub>4</sub>) nanoparticles have been prepared by a simple chemical method. Polymer nanocomposites based on the blend between poly vinylamine fluoride (PVDF) and (methyl methacrylate) (PMMA) doped with different concentrations of Fe<sub>3</sub>O<sub>4</sub> nanoparticles have been prepared. The structural, optical, and magnetization properties of the nanocomposite samples were studied using suitable techniques. The X-ray study reflected that the cubic spinal structure of pure Fe<sub>3</sub>O<sub>4</sub> crystal. No small peaks or ripples were found in the X-ray spectra, conforming to good dispersion of Fe<sub>3</sub>O<sub>4</sub> within PVDF/PMMA matrices. The FT-IR analysis demonstrated the miscibility between the PVDF and PMMA blend with the interaction between the polymer blend and Fe<sub>3</sub>O<sub>4</sub>. The values of the band gap from UV-Vis study were decreased up to 4.21 eV, 3.01 eV for direct and indirect measurements, respectively. The magnetization was measured as a function of the applied magnetic field in the range of −2000 - 2000 Oersted. The curves of the magnetization indicated a paramagnetic behavior of pure Fe<sub>3</sub>O<sub>4</sub> nanoparticles and PVDF/PMMA-Fe<sub>3</sub>O<sub>4</sub> nanocomposites. The values of saturation magnetization for pure Fe<sub>3</sub>O<sub>4</sub> are nearly 75 emu/g, exhibiting a paramagnetic behavior, and it is decreased with the increase of Fe<sub>3</sub>O<sub>4</sub> content.展开更多
Background:poly(vinylidene fluoride)PVDF and PVDF/PMMA blends have been investigated with a focus on the crystal structure,immiscibility and mechanical properties.However,few reports were found on the crystallization ...Background:poly(vinylidene fluoride)PVDF and PVDF/PMMA blends have been investigated with a focus on the crystal structure,immiscibility and mechanical properties.However,few reports were found on the crystallization behaviors of PVDF and PVDF/PMMA blends,especially on crystallization kinetics.The article is to report the research on isothermal and nonisothermal crystallization kinetics for PVDF and PVDF/PMMA blends using differential scanning calorimetry(DSC).Results:Besides crystallization temperature and isothermal crystallization activation energy,the Avrami equation exponent of PVDF in blends decreased compared with pure PVDF.The nonisothermal crystallization kinetics of PVDF and PVDF/PMMA(70:30)blends were investigated by Ozawa equation,Jeziorny method and crystallization rate constant(CRC)in detail.The nonisothermal crystallization energy of pure PVDF and its blends were determined by the Kissinger and Vyazovkin’s method.Conclusion:The nucleation and growth mechanism of PVDF in blends changed compared with pure PVDF.The Ozawa equation is not applicable in nonisothermal crystallization kinetics of PVDF and PVDF/PMMA blends.The decreasing of crystallization ability of PVDF in blends were found and confirmed by CRC and the decline of crystallization rate constant in Jeziorny method.Such is opposite to the results of Kissinger’s and Vyazovkin’s method,chances are that these two methods were not used to calculate the nonisothermal crystallization activation energy where the nucleation process was influenced.展开更多
The attainment of a better understanding and improvement of electrical properties of ternary blend is a task of particular scientific and economic importance. Ternary films of Poly (methylmethacrylate), Poly (ethlymat...The attainment of a better understanding and improvement of electrical properties of ternary blend is a task of particular scientific and economic importance. Ternary films of Poly (methylmethacrylate), Poly (ethlymathacrylate) and poly (vinlylidenefluoride) were prepared using solution cast technique. Thereafter, to study the hetro charges, homo-charges and interfacial charge formation in ternary system, the short circuit thermally stimulated discharge current (SC-TSDC) measurements were carried out on bilaterally metallized electrets. The ternary blend samples taken for the present investigations are hetrogeneous system involving three polymers differing in their conduction behaviour and dielectric property. Thus, unequal ohmic conduction currents arriving at the interface are expected to result in accumulation of charges at the interface or the Maxwell-Wagner effect. Clearly the Maxwell Wagner effect is expected to contribute discernibly to the observed TSDC’s of the ternary blends. The PMMA: PEMA: PVDF:: 100:100:50 blend exhibits highest tendency while 100:50:100 the least, towards the anomalous current flow. Moreover, the conductivity of 100: 100: 50 is found to be more and, therefore, a large amount of homocharge is injected leading to anomalous current.展开更多
为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜对电解液体系的亲和性和导电性,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,并添加有机增塑剂聚乙二醇PEG-400对PVDF基聚合物隔膜进行改性研究。采用先干法后湿法的相转化方...为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜对电解液体系的亲和性和导电性,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,并添加有机增塑剂聚乙二醇PEG-400对PVDF基聚合物隔膜进行改性研究。采用先干法后湿法的相转化方法制备PVDF/PMMA/PEG型聚合物隔膜。通过对制备的聚合物隔膜的孔隙率、吸液率、微观形貌和电化学性能的分析研究,确定制膜的最佳工艺条件为聚合物占溶剂质量百分比为8%,PVDF∶PMMA=7∶3,增塑剂含量为30%,非溶剂含量为3%,反应温度为45℃,在此最佳工艺条件下制备的PVDF/PMMA/PEG隔膜的离子电导率可达2.848 m S/cm,对电解液体系的亲和性和导电性得到显著提高。展开更多
采用溶剂挥发法,以丙酮和DMF做混合溶剂制备PVDF-HFP/PMMA聚合物电解质,通过X射线衍射、热失重分析、交流阻抗、恒流充放电循环及倍率充放电等测试手段,考察了PMMA的添加量对聚合物电解质性能的影响.研究发现当PMMA的添加量为50%时,聚...采用溶剂挥发法,以丙酮和DMF做混合溶剂制备PVDF-HFP/PMMA聚合物电解质,通过X射线衍射、热失重分析、交流阻抗、恒流充放电循环及倍率充放电等测试手段,考察了PMMA的添加量对聚合物电解质性能的影响.研究发现当PMMA的添加量为50%时,聚合物电解质表现出最佳性能,室温离子电导率从0.26 m S/cm提升到1.35 m S/cm,以Li Co O2作正极材料,锂片作负极材料组装的聚合物锂离子电池初始容量从80.1 m Ah/g提升到143.6 m Ah/g,在0.2 C倍率条件下,50个循环后容量保持率还能达到80%,表现出优异的锂离子电池性能.展开更多
文摘In the present work, magnetite (Fe<sub>3</sub>O<sub>4</sub>) nanoparticles have been prepared by a simple chemical method. Polymer nanocomposites based on the blend between poly vinylamine fluoride (PVDF) and (methyl methacrylate) (PMMA) doped with different concentrations of Fe<sub>3</sub>O<sub>4</sub> nanoparticles have been prepared. The structural, optical, and magnetization properties of the nanocomposite samples were studied using suitable techniques. The X-ray study reflected that the cubic spinal structure of pure Fe<sub>3</sub>O<sub>4</sub> crystal. No small peaks or ripples were found in the X-ray spectra, conforming to good dispersion of Fe<sub>3</sub>O<sub>4</sub> within PVDF/PMMA matrices. The FT-IR analysis demonstrated the miscibility between the PVDF and PMMA blend with the interaction between the polymer blend and Fe<sub>3</sub>O<sub>4</sub>. The values of the band gap from UV-Vis study were decreased up to 4.21 eV, 3.01 eV for direct and indirect measurements, respectively. The magnetization was measured as a function of the applied magnetic field in the range of −2000 - 2000 Oersted. The curves of the magnetization indicated a paramagnetic behavior of pure Fe<sub>3</sub>O<sub>4</sub> nanoparticles and PVDF/PMMA-Fe<sub>3</sub>O<sub>4</sub> nanocomposites. The values of saturation magnetization for pure Fe<sub>3</sub>O<sub>4</sub> are nearly 75 emu/g, exhibiting a paramagnetic behavior, and it is decreased with the increase of Fe<sub>3</sub>O<sub>4</sub> content.
基金This work was financially supported by Start Fund For High Level Talents of Nanjing Polytechnic Institute(China).
文摘Background:poly(vinylidene fluoride)PVDF and PVDF/PMMA blends have been investigated with a focus on the crystal structure,immiscibility and mechanical properties.However,few reports were found on the crystallization behaviors of PVDF and PVDF/PMMA blends,especially on crystallization kinetics.The article is to report the research on isothermal and nonisothermal crystallization kinetics for PVDF and PVDF/PMMA blends using differential scanning calorimetry(DSC).Results:Besides crystallization temperature and isothermal crystallization activation energy,the Avrami equation exponent of PVDF in blends decreased compared with pure PVDF.The nonisothermal crystallization kinetics of PVDF and PVDF/PMMA(70:30)blends were investigated by Ozawa equation,Jeziorny method and crystallization rate constant(CRC)in detail.The nonisothermal crystallization energy of pure PVDF and its blends were determined by the Kissinger and Vyazovkin’s method.Conclusion:The nucleation and growth mechanism of PVDF in blends changed compared with pure PVDF.The Ozawa equation is not applicable in nonisothermal crystallization kinetics of PVDF and PVDF/PMMA blends.The decreasing of crystallization ability of PVDF in blends were found and confirmed by CRC and the decline of crystallization rate constant in Jeziorny method.Such is opposite to the results of Kissinger’s and Vyazovkin’s method,chances are that these two methods were not used to calculate the nonisothermal crystallization activation energy where the nucleation process was influenced.
文摘The attainment of a better understanding and improvement of electrical properties of ternary blend is a task of particular scientific and economic importance. Ternary films of Poly (methylmethacrylate), Poly (ethlymathacrylate) and poly (vinlylidenefluoride) were prepared using solution cast technique. Thereafter, to study the hetro charges, homo-charges and interfacial charge formation in ternary system, the short circuit thermally stimulated discharge current (SC-TSDC) measurements were carried out on bilaterally metallized electrets. The ternary blend samples taken for the present investigations are hetrogeneous system involving three polymers differing in their conduction behaviour and dielectric property. Thus, unequal ohmic conduction currents arriving at the interface are expected to result in accumulation of charges at the interface or the Maxwell-Wagner effect. Clearly the Maxwell Wagner effect is expected to contribute discernibly to the observed TSDC’s of the ternary blends. The PMMA: PEMA: PVDF:: 100:100:50 blend exhibits highest tendency while 100:50:100 the least, towards the anomalous current flow. Moreover, the conductivity of 100: 100: 50 is found to be more and, therefore, a large amount of homocharge is injected leading to anomalous current.
文摘为提高锂离子电池聚偏氟乙烯(PVDF)基聚合物隔膜对电解液体系的亲和性和导电性,引入聚甲基丙烯酸甲酯(PMMA)与聚偏氟乙烯(PVDF)进行共混,并添加有机增塑剂聚乙二醇PEG-400对PVDF基聚合物隔膜进行改性研究。采用先干法后湿法的相转化方法制备PVDF/PMMA/PEG型聚合物隔膜。通过对制备的聚合物隔膜的孔隙率、吸液率、微观形貌和电化学性能的分析研究,确定制膜的最佳工艺条件为聚合物占溶剂质量百分比为8%,PVDF∶PMMA=7∶3,增塑剂含量为30%,非溶剂含量为3%,反应温度为45℃,在此最佳工艺条件下制备的PVDF/PMMA/PEG隔膜的离子电导率可达2.848 m S/cm,对电解液体系的亲和性和导电性得到显著提高。
文摘采用机械共混法制备了Si O2改性的CPVC/PVDF/PMMA复合材料,考察了Si O2用量、PVB、PVC、丁腈粉、DBP对材料成膜性能、吸墨性能、柔软性和韧性的影响.结果表明:1当Si O2的质量浓度为4.5%时,CPVC的成膜性和吸墨性能最佳;2当DBP、丁腈粉的质量分数分别为3.0%和3.4%时,膜的柔韧性最佳;3最佳的制备工艺是将PMMA、CPVC、PVDF和丁腈粉溶于DMAC和DBP的混合溶液中,再恒温4 h.
文摘采用溶剂挥发法,以丙酮和DMF做混合溶剂制备PVDF-HFP/PMMA聚合物电解质,通过X射线衍射、热失重分析、交流阻抗、恒流充放电循环及倍率充放电等测试手段,考察了PMMA的添加量对聚合物电解质性能的影响.研究发现当PMMA的添加量为50%时,聚合物电解质表现出最佳性能,室温离子电导率从0.26 m S/cm提升到1.35 m S/cm,以Li Co O2作正极材料,锂片作负极材料组装的聚合物锂离子电池初始容量从80.1 m Ah/g提升到143.6 m Ah/g,在0.2 C倍率条件下,50个循环后容量保持率还能达到80%,表现出优异的锂离子电池性能.
