【作者】 刘立柱；

【导师】 雷清泉；

【作者基本信息】 哈尔滨理工大学 ， 高电压与绝缘技术， 2006， 博士

【摘要】 目前,人们已将聚酰亚胺（PI）与SiO₂、TiO₂和蒙脱土等单组分无机物制成杂化材料,并且表现出优异的物理化学性能,但是将两种组分同时掺入PI基体中,由于工艺、制备等因素的复杂性,该方面的报道较少。本文用正交试验设计法,研究了聚酰胺酸固体含量、反应温度、加料间隔时间和反应时间对聚酰胺酸分子量及其分布的影响,采用凝胶渗透色谱仪测试了不同反应条件下合成的聚酰胺酸的分子量,确定了合成最高分子量聚酰胺酸的反应条件,该反应条件为反应温度:15℃;固体含量:8wt%;加料间隔时间:9min;反应时间:3h。用超声-机械共混法制备了PI/SiO₂、PI/Al₂O₃和PI/SiO₂-Al₂O₃杂化薄膜。采用红外光谱仪、原子力显微镜表征了杂化薄膜的结构和形貌,测试了杂化薄膜的热稳定性、紫外-可见光透过率、力学性能和耐电晕性。红外光谱分析表明杂化薄膜亚胺化不完全;原子力显微镜分析表明超声波对无机纳米粒子的分散作用明显,使纳米SiO₂粒子较均匀地分散在PI基体中,平均粒径70nm左右。杂化薄膜的耐电晕性比纯PI薄膜有所提高,且随着纳米粒子含量的增加有上升趋势,但提高不太明显,耐电晕时间最长提高4倍左右。杂化薄膜与纯PI薄膜相比,热稳定性稍有下降;拉伸强度和断裂伸长率稍有提高;紫外-可见光透过率降低。采用溶胶-凝胶法制备了PI/SiO₂、PI/Al₂O₃和PI/SiO₂-Al₂O₃杂化薄膜。探讨了无机含量、无机组分重量比、杂化工艺和亚胺化工艺对无机相形态结构、尺寸、均匀性、分散性以及杂化薄膜的热稳定性、电击穿场强、介电性能、耐电晕性、紫外-可见光透过率和力学性能的影响。通过红外光谱仪、原子力显微镜、紫外-可见分光光度计和示差扫描量热仪,分析了聚酰胺酸的亚胺化反应。结果表明随亚胺化温度的升高,无机相尺寸和紫外-可见光透过率先增大后减小,在140℃时出现峰值。混合溶胶使聚酰胺酸的反应热降低,加速了聚酰胺酸的亚胺化反应。在溶胶-凝胶法中,根据加入溶胶的方法不同进行一系列实验。首先,在合成聚酰胺酸后加入不同的溶胶。由傅立叶红外光谱谱图可以看出PI杂化薄膜已完全亚胺化,在硅铝共杂化的薄膜中,存在Si-O-Si、Al-O-Al结构,且PI基体与纳米粒子之间有一定键合,并有Si-O-Al结构形成。扫描电镜结果表明在硅铝共杂化的薄膜中存在球形和短纤维形两种无机相形貌,通过点元素分析某一无机颗粒处既存在硅元素又存在铝元素,进一步说明有Si-O-Al结构形成。其次,在合成聚酰胺酸过程中加入溶胶,并对中间加入溶胶是否使用超声波两种不同加胶方法进行比较。扫描电镜和原子力显微镜结果表明采用中间加入溶胶的方法制备的聚酰亚胺/无机杂化薄膜,其无机粒子的粒径为纳米级,溶胶在反应过程中加入比在合成聚酰胺酸后加入有利于无机纳米粒子的均匀分散,且粒子尺寸更小。溶胶在反应过程中加入时,使用超声更有益于无机纳米粒子的均匀分散。X-射线衍射实验结果表明未掺杂溶胶的PI薄膜具有一定有序度,而杂化薄膜中无机组分为非晶态,无机组分的加入破坏了PI薄膜有序度,加入偶联剂或改变亚胺化工艺可以改变杂化薄膜的有序度。偶联剂DB-550的加入改变了杂化薄膜的分子结构。各项性能测试结果表明无机含量和无机组分重量比影响杂化薄膜的紫外-可见光透过率、热稳定性、电击穿场强、耐电晕性、介电性能和力学性能。用超声溶胶并在合成聚酰胺酸过程中加入法所制备的薄膜,在紫外-可见光透过率、热稳定性、电击穿场强、耐电晕性和力学性能上,比其它溶胶加入方法好。硅铝共杂化薄膜,在性能上比SiO₂或Al₂O₃的杂化薄膜好。双无机组分与单无机组分掺杂的杂化薄膜相比,有可能实现某些性能在更宽范围内的调整。当杂化薄膜中的无机含量为4wt%,SiO₂与Al₂O₃的重量比为4:1,且加入一定量的偶联剂DB-550时,其综合性能最为优异。其热分解温度比纯膜提高了18℃左右;电击穿场强比纯膜提高了近20%,耐电晕时间是纯膜的16倍;拉伸强度比纯膜提高了近50%,断裂伸长率比纯膜提高了近136%。杂化薄膜的介电常数和介电损耗与频率的关系,符合德拜松弛极化机理。纳米无机氧化物对杂化薄膜的介电常数、介电损耗的影响是复杂和反常的,这些影响因素的因果关系有待进一步探讨。更多还原

【Abstract】 At present, fillers such as TiO₂, SiO₂ and montmorillonite have been hybridized with polyimide matrix. Moreover some of the favorable results have been obtained. But previous studies about polyimide/inorganic hybrids were concentrated on the binary systems, in which exists a sort of inorganic portion. Due to the key challenge for complicated techniques and preraration ,there were few reports about ternary systems.In this paper it investigates the influencing factors ,such as solid content, reaction temperature and time, time interval of adding material , which affect the molecular weight and its distribution of poly （amic acid） in virtue of orthogonal design method. Molecular weight of poly （amic acid） on different raction conditions is tested by gel permeation chromatography. The results indicates the condition for synthesizing the maximal molecular weight poly （amic acid） is that solid content is 8wt%, reaction temperature is 15℃; time interval is 9 minutes ; reaction time is 3 hours.Polyimide/silica（PI/SiO₂）,polyimide/alumina（PI/Al₂O₃）and polyimide/silica- alumina （PI/SiO₂-Al₂O₃） hybrid films are prepared by ultrasonic-mechanical method. Struture and morphology of hybride films are characterized by Fourier transform infrared apparatus and atomic force microscope. Thermal stability, transmittance of UV-Vis, mechanical properties and corona-resistance of polyimide hybrid films are tested. Fourier transform infrared spectra analysis show imidization of hybrid films is incomplete. It is effective for the dispersion of nano-SiO₂ particles to use ultrasonic. Nanoparticles distribute uniformly in the polyimide matrix and the average diameter of the particles is about 70 nm. Compare with pure polyimide films ,corona-resistance time of the hybrid films is longer, moreover with the increasing of the content of nanoparticles it reveals aggrandizement, but the increased range is unconspicuous.The longest corona-resistance time of hybrid films reaches four times than pure polyimide films.Compare with pure polyimide films, thermal stability of hybrid ones show degressive trend, tensile strength and elongation of them are slightly enhanced, transmittance of UV-Vis spectra are decline.PI/SiO₂, PI/Al₂O₃ and PI/SiO₂-Al₂O₃ hybrid films are prepared by sol-gel method. It discusses that morphology characterization and properties ,including struture and morphology , uniformity and dispersity of inorganic phase as well as thermal stability , breakdown strength ,corona-resistance and dielectric properties, transmittance of UV-Vis spectra ,mechanical properties of polyimide hybrid films ,are affected by some factors .And influencing factors are composed of the contents and weight ratio of inorganic components ,hybridized technology as well as imidization process.Imidization process is analysed by Fourier transform infrared spectra, UV-Vis spectrophotometer, atomic force microscope, differential scanning calorimeter and so on .It reveales that with the increasing of imidization temperature inorganic phase size and transmittance was increases at first, then decreases. Nevertheless it appeares peak value at about 140℃. Mixed sol makes reaction heat of poly （amic acid） reduce. At the same time imidization process is accelerated.In sol-gel method according to different modes charged sol ,a series of experiments are done. Firstly,after preparation of poly （amic acid） different sols are added in poly （amic acid） solution.As has been seen from Fourier transform infrared spectra,it indicates complete imidization of hybrid flims. Si-O-Si and Al-O-Al bonds exsiste in the films hybridized with silica and alumina sols.There are linkages between polyimide matrix and nanoparticles. Also this suggestes the existence of Si-O-Al bonds.In response to the results of scanning electron microscope there are spherical shaped and club shaped particles in the films hybridized with silica and alumina sols.Analysis of spot element reveales there are silicon and aluminium element in this point, which proves the form of Si-O-Al bond ulteriorly.Secondly, during preparation of poly （amic acid） different sols are added in poly （amic acid） solution,and the method using ultrasonic-mechanical method compared with nonuse of it. On the base of atomic force microscope and scanning electron microscope, it reveales the average diameter of the particles are nanometer in the hybrid films which sols are added in during the reaction. Also size of nanoparticles is much smaller. However making use of ultrasonic-mechanical method is beneficial to uniform distribution of inorganic nanoparticles.As has been seen from X-ray diffracition spectra results, it shows crystallinity exsisted in pure polyimide film. Inorganic phase is amorphous phase. Furthermore crystallinity of pure polyimide film is damaged by inorganic components. Coupling agents or the variety of imidization techonolgy may change crystallinity of polyimide film. Coupling agents DB-550 changes the structure of hybrid films.Results of diversified test indicate inorganic contents and weight proportion of inorganic components influences UV-Vis transmittance , thermal stability , breakdown strength, corona-resistance and dielectric properties , mechanical properties. All kinds of properties of hybrid films using ultrasonic-mechanical method during preparation of poly （amic acid） mixe solution are better than in other methods.The properties of ternary systems precedes that of binary systems. In comparision with the binary systems, some properties will be probably regulated in the ternary systems.When the inorganic content of the hybrid films added coupling agents DB-550 is 4wt% for SiO₂/Al₂O₃ （4/1）, its integrated property is the most outstanding. In comparison with pure polyimide films, decomposition temperature of the hybrid film increases about 18℃; Breakdown strength of it increases percent 20; Corona-resistance time is 16 times than pure polyimide film;Tensile strength increases percent 50.Relation of dielectric constant and dielectric loss angle with frequency in the hybrid films accordes with Debye relaxation polarization mechanism. In comparison with plain polyimide films, the change of dielectric constant and dielectric loss angle of hybrid films is anomalistic. Effect factors of dielectric constant and dielectric loss angle of hybrid films will be discussed ulteriorly.更多还原