【作者】 陈剑；

【导师】 李继定；

【作者基本信息】 清华大学 ， 化学工程与技术， 2005， 硕士

【摘要】 等离子体改性技术能快速、高效地引发常规反应中不能或很难实现的物理或化学变化,赋予膜材料表面各种优异性能,而不改变基体材料本身的性质,是拓展高分子膜材料应用范围的一种重要方法。本文以聚丙烯腈（PAN）超滤膜和聚偏氟乙烯（PVDF）超滤膜为基材,利用低温等离子体技术对其进行接枝改性,在膜表面引入不同的单体,使膜表面孔径大小可以进行控制和调节,达到提高分离性能的目的。采用气相接枝技术在 PAN 膜表面引入疏水性单体苯乙烯,用液相接枝技术在 PAN 膜表面引入亲水性单体 N-乙烯吡咯烷酮（NVP）。通过傅立叶红外光谱（FT-IR） 和 X 射线光电子能谱（XPS）分析膜的表面结构变化,用差示扫描量热仪（DSC）分析接枝前后膜表面孔径的变化。研究了等离子体照射功率、照射时间、接枝时间对膜分离性能的影响以及水通量的变化规律。考察了 PAN 接枝苯乙烯改性膜对润滑油脱蜡溶剂（甲苯和丁酮）体系的分离性能及其酮苯溶剂浓度对分离性能的影响,结果表明,采用接枝的 PAN 膜用来回收溶剂甲苯丁酮效果良好,可使苯酮溶剂的含量由 83.94wt%提高到 98.42wt%,对润滑油的截留率达到了90.2%。此外,考察了 PAN 接枝 NVP 改性膜的脱盐率,结果表明,在 2MPa 操作压力下,对混合盐（MgSO₄、NaCl）/体系的脱盐率最高达到 83.54%。采用低温等离子体接枝技术改性聚偏氟乙烯膜（PVDF）,在 PVDF 膜表面引入疏水性单体苯乙烯,通过改变反应条件,达到改变膜表面孔径大小的目的。采用傅立叶红外光谱仪（FTIR-ATR）和原子力显微镜（AFM）考察改性前后 PVDF 膜的官能团的变化;通过接触角的变化考察改性前后亲疏水性。采用示差扫描量热仪（DSC）分析 PVDF 改性前后膜的孔径分布,考察改性条件对膜孔径大小和分布的影响。通过扫描电子显微镜（SEM）观测了 PVDF 膜改性前后表面形态的变化。结果表明,随着接枝时间的延长、接枝温度的提高,PVDF 改性膜的孔径分布变窄,纯水通量下降,接枝率提高。更多还原

【Abstract】 Low-temperature plasma technique has been developed to modify the surfaces ofpolymer membranes. It could endow the polymer membrane surface many excellentproperties without changing its bulk properties. The physical or chemical changeswhich could not be realized by normal reactions could be initiated quickly andefficiently by plasma technique. So low-temperature plasma technique has beenextensively used to modify the polymer membranes.This dissertation concerns using the low-temperature plasma toprefunctionalize poly-acrylonitrile(PAN) and polyvinylidenefluoride(PVDF)ultrafiltration membranes in vapor or liquid phase, and then the monomerswith different properties were introduced to the surface pores of themembranes. Therefore, the surface pore size and its distribution of themembranes can be adjusted from ultrafiltration to nanofiltration by the reationconditions.Styrene, the hydrophobic monomer, was grafted onto the surface of PANmembranes by the low-temperature plasma in gas phase, whileN-vinylpyrrolidone (NVP), the hydrophilic monomer, was grafted onto themembrane surface in aqueous phase. The surface structure of the modifiedmembranes were determined by FTIR-ATR and XPS, while the pore size ofthe membrane before and afer grafting were measued by DSC technique. Theeffect of operation condition, such as plasma power, plasma treatment time,grafting reaction time, on the separation properties and water flux of themembranes were investigated. The styrene grafted PAN membrane using lowtemperature plasma technique showed excellent chemical resistance andrejection for the separation of toluene and ketone from lube oil. For the feedcomposition of 83.94wt% solvent, the solvent in permeate solution was98.42wt%, and the rejection of lube oil was 90.2%. Furthermore, the flux andrejection of NVP graft PAN membranes were invesigated by the separation ofmixed salt (MgSO4+NaCl)/water system. The NVP grafted PAN membranesexhibited applicable separation performances for mixed salt(MgSO4+NaCl)/water system. At 2 MPa, the rejection of mixed salt by using the modifiedmembrane reached 83.54%.Moreover, PVDF ultrafiltration membrane surface was modified by lowtemperature plasma technique, so that the surface pore size of the membranedcan be adjusted by the reaction condition. By argon (Ar) treating andsubsequent grafting reaction, styrene, a hydrophobic monomer, wasintroduced onto PVDF membrane surface. The structure and chemicalcomposition of the PVDF membrane surface were characterized by ATR-FTIR.The surface morphology of PVDF membrane were observed by scanningelectron microscope (SEM), and atomic force microscopy (AFM). The poresize and its distribution of the membrane surface was determined bydifferential scanning calorimeter (DSC). The varation of the pore size and itsdistribution and the water permeability with grafting reaction condition, suchas plasma treatment time, the graftiong time, and the grafting temperaturewere investigated. The results showed that styrene monomer was successfullygrafted onto PVDF membrane surface. With the increasing in plasma time andgraft time, the pore size of modified membranes decreased and thedistribution of pore size narrowed, and the pure water flux decreased.更多还原