纳米纤维素改性聚偏氟乙烯膜材料性能研究
发布时间：2018-09-11 12:47
【摘要】：本论文以纤维素浆粕为原料,制备了纳米纤维素(CNF)、硅烷偶联剂KH-540改性纳米纤维素(K-CNF),并将CNF、K-CNF对聚偏氟乙烯(PVDF)进行共混改性,采用浸没-沉淀相转化法制备出CNF/PVDF膜材料和K-CNF/PVDF.膜材料,以提高PVDF膜的渗透性能、亲水性能、抗污染性能和力学性能。对CNF、K-CNF以及共混膜材料的各方面性能进行了表征。使用CNF/PVDF膜材料和K-CNF/PVDF膜材料分别超滤处理牛奶蛋白料液,探究了两种膜材料处理牛奶蛋白料液的最优工艺条件,考察了膜清洗方法的清洗效果。分别从热力学和动力学角度对CNF/PVDF膜材料和K-CNF/PVDF膜材料的成膜机理做出探讨,使用旋转流变仪系统研究了CNF/PVDF和K-CNF/PVDF铸膜液的流变学性质。CNF呈棒状纤维结构,直径为20nm-50nm,长度为200-550 nm,结晶度较纤维素浆粕有所提高。将CNF与PVDF共混制备CNF/PVDF膜材料,得出CNF/PVDF膜材料的最优制备条件,即：PVDF浓度为16 wt%,CNF浓度为0.5 wt%,溶剂为N,N-二甲基乙酰胺(DMAc),致孔剂PVP K30质量分数为3 wt%,凝胶浴为去离子水。对比纯PVDF膜,最优制备条件下制备的CNF/PVDF共混膜的渗透性能提高了72.0%,抗张强度和断裂伸长率分别提高了18.2%和36.4%,接触角从81.4。降低至66.9。膜材料的衰减系数从44.59%降到31.65%。使用硅烷偶联剂KH-540改性CNF制备出K-CNF。AFM表征表明K-CNF维持了CNF的形貌,长度为200-500 nm,直径为30-40 nm,FTIR与XPS表征共同证明KH-540与CNF发生了偶联反应。XPS结果显示K-CNF表面羟基的数量少于CNF。当K-CNF质量分数为0.5 wt%时,K-CNF/PVDF共混膜各方面性能达到最佳,与纯PVDF膜相比,K-CNF/PVDF共混膜的渗透、亲水及抗污染性能均有显著提升,抗张强度提高了36.77%,断裂伸长率提高了61.18%。相比于CNF/PVDF膜,K-CNF/PVDF膜的力学性能得到进一步改善。热力学研究表明CNF和K-CNF的引入分别使PVDF/DMAc/H2O体系的浊点线向PVDF-DMAc轴靠近,体系变得热力学不稳定,减弱了溶液体系对水的容纳能力,促进了相分离。动力学研究表明CNF和K-CNF的引入分别提高了PVDF铸膜液的凝胶速率,加快了凝胶成膜的进程。CNF/PVDF铸膜液与K-CNF/PVDF铸膜液的非牛顿指数均小于1,故均为假塑性流体。分别升高CNF、K-CNF和PVDF的浓度,PVDF铸膜液的非牛顿指数降低,恒剪切粘度、零剪切粘度、粘流活化能和模量均升高。CNF/PVDF膜材料和K-CNF/PVDF膜材料处理牛奶蛋白料液的最佳操作条件均为：0.1MPa的操作压力,1g/L的牛奶蛋白料液浓度,料液的pH值：11,料液温度：40℃。考察了膜清洗方法对CNF/PVD F膜材料和K-CNF/PVDF膜材料的清洗效果。对于两种膜材料,氢氧化钠溶液清洗+水力反冲洗法的清洗效果最好。
[Abstract]:In this paper, nano-cellulose (CNF), silane coupling agent KH-540 modified nano-cellulose (K-CNF) was prepared by using cellulose pulp as raw material, and CNF,K-CNF was blended to modify polyvinylidene fluoride (PVDF). CNF/PVDF membrane material and K-CNF / PVDF were prepared by immersion-precipitation phase inversion method. Membrane materials to improve the permeability, hydrophilicity, pollution resistance and mechanical properties of PVDF membranes. The properties of CNF,K-CNF and blend film were characterized. CNF/PVDF membrane material and K-CNF/PVDF membrane material were used to ultrafiltration the milk protein material respectively. The optimum processing conditions of two kinds of membrane materials to treat milk protein material were investigated and the cleaning effect of the membrane cleaning method was investigated. The film forming mechanism of CNF/PVDF and K-CNF/PVDF membrane materials was studied from the viewpoint of thermodynamics and kinetics, and the rheological properties of CNF/PVDF and K-CNF/PVDF casting solution were studied by rotating rheometer. The crystallinity of 20nm-50nm in diameter and 200-550 nm, in length was higher than that of cellulose pulp. CNF/PVDF membrane materials were prepared by blending CNF with PVDF. The optimum preparation conditions of CNF/PVDF membrane materials were obtained, that is, the concentration of CNF/PVDF was 16 wt%,CNF, 0.5 wt%, solvent was NN- dimethyl acetamide (DMAc), pore-inducing agent PVP K30, and the mass fraction of PVP K30 was 3 wt%, gel bath as deionized water. Compared with pure PVDF membrane, the permeability, tensile strength and elongation at break of CNF/PVDF blend membrane were increased by 72.0%, 18.2% and 36.4%, respectively, and the contact angle was increased from 81.4% to 81.4%. Down to 66.9. The attenuation coefficient of the membrane material decreased from 44.59% to 31.65%. The K-CNF.AFM characterization of CNF modified by silane coupling agent KH-540 showed that K-CNF maintained the morphology of CNF. The length of 200-500 nm, was 30-40 nm,FTIR and XPS. The results of KH-540 coupling reaction with CNF showed that the number of hydroxyl groups on K-CNF surface was less than that of CNF.. When the mass fraction of K-CNF is 0.5 wt%, the properties of K-CNF / PVDF blend membrane are the best. Compared with pure PVDF membrane, the permeation, hydrophilicity and pollution resistance of K-CNF / PVDF blend membrane are improved significantly, the tensile strength is increased by 36.77 and the elongation at break is increased by 61.18. Compared with CNF/PVDF membrane, the mechanical properties of K-CNF / PVDF membrane were further improved. Thermodynamic studies show that the introduction of CNF and K-CNF makes the cloud point line of PVDF/DMAc/H2O system close to the PVDF-DMAc axis, and the system becomes thermodynamically unstable, which weakens the water holding capacity of the solution system and promotes the phase separation. Kinetic studies show that the introduction of CNF and K-CNF increases the gelation rate of PVDF casting solution, and accelerates the gelation process. The non-Newtonian exponents of both CNF / PVDF and K-CNF/PVDF casting solutions are less than 1, so they are pseudoplastic fluids. By increasing the concentration of CNF,K-CNF and PVDF respectively, the non-Newtonian index of PVDF casting solution is decreased, and the constant shear viscosity and zero shear viscosity are obtained. Viscosity flow activation energy and modulus were increased. The optimal operating conditions for milk protein solution treated with CNF / PVDF membrane material and K-CNF/PVDF membrane material were: 1 g / L operating pressure of 1 g / L, 1 g / L of milk protein concentration, pH value of feed solution: 11, feed temperature: 40 鈩，
本文编号：2236730
[Abstract]:In this paper, nano-cellulose (CNF), silane coupling agent KH-540 modified nano-cellulose (K-CNF) was prepared by using cellulose pulp as raw material, and CNF,K-CNF was blended to modify polyvinylidene fluoride (PVDF). CNF/PVDF membrane material and K-CNF / PVDF were prepared by immersion-precipitation phase inversion method. Membrane materials to improve the permeability, hydrophilicity, pollution resistance and mechanical properties of PVDF membranes. The properties of CNF,K-CNF and blend film were characterized. CNF/PVDF membrane material and K-CNF/PVDF membrane material were used to ultrafiltration the milk protein material respectively. The optimum processing conditions of two kinds of membrane materials to treat milk protein material were investigated and the cleaning effect of the membrane cleaning method was investigated. The film forming mechanism of CNF/PVDF and K-CNF/PVDF membrane materials was studied from the viewpoint of thermodynamics and kinetics, and the rheological properties of CNF/PVDF and K-CNF/PVDF casting solution were studied by rotating rheometer. The crystallinity of 20nm-50nm in diameter and 200-550 nm, in length was higher than that of cellulose pulp. CNF/PVDF membrane materials were prepared by blending CNF with PVDF. The optimum preparation conditions of CNF/PVDF membrane materials were obtained, that is, the concentration of CNF/PVDF was 16 wt%,CNF, 0.5 wt%, solvent was NN- dimethyl acetamide (DMAc), pore-inducing agent PVP K30, and the mass fraction of PVP K30 was 3 wt%, gel bath as deionized water. Compared with pure PVDF membrane, the permeability, tensile strength and elongation at break of CNF/PVDF blend membrane were increased by 72.0%, 18.2% and 36.4%, respectively, and the contact angle was increased from 81.4% to 81.4%. Down to 66.9. The attenuation coefficient of the membrane material decreased from 44.59% to 31.65%. The K-CNF.AFM characterization of CNF modified by silane coupling agent KH-540 showed that K-CNF maintained the morphology of CNF. The length of 200-500 nm, was 30-40 nm,FTIR and XPS. The results of KH-540 coupling reaction with CNF showed that the number of hydroxyl groups on K-CNF surface was less than that of CNF.. When the mass fraction of K-CNF is 0.5 wt%, the properties of K-CNF / PVDF blend membrane are the best. Compared with pure PVDF membrane, the permeation, hydrophilicity and pollution resistance of K-CNF / PVDF blend membrane are improved significantly, the tensile strength is increased by 36.77 and the elongation at break is increased by 61.18. Compared with CNF/PVDF membrane, the mechanical properties of K-CNF / PVDF membrane were further improved. Thermodynamic studies show that the introduction of CNF and K-CNF makes the cloud point line of PVDF/DMAc/H2O system close to the PVDF-DMAc axis, and the system becomes thermodynamically unstable, which weakens the water holding capacity of the solution system and promotes the phase separation. Kinetic studies show that the introduction of CNF and K-CNF increases the gelation rate of PVDF casting solution, and accelerates the gelation process. The non-Newtonian exponents of both CNF / PVDF and K-CNF/PVDF casting solutions are less than 1, so they are pseudoplastic fluids. By increasing the concentration of CNF,K-CNF and PVDF respectively, the non-Newtonian index of PVDF casting solution is decreased, and the constant shear viscosity and zero shear viscosity are obtained. Viscosity flow activation energy and modulus were increased. The optimal operating conditions for milk protein solution treated with CNF / PVDF membrane material and K-CNF/PVDF membrane material were: 1 g / L operating pressure of 1 g / L, 1 g / L of milk protein concentration, pH value of feed solution: 11, feed temperature: 40 鈩，
本文编号：2236730
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