【作者】 黄丽娜；

【导师】 张平余； 张晟卯；

【作者基本信息】 河南大学 ， 凝聚态物理， 2019， 博士

【摘要】 合成酯类润滑油由于热氧化稳定性好、润滑性能良好、可生物降解和对极性物质较好的溶解性等优点,成为润滑油研究的重要方向。酯类润滑油在使用过程中,在氧气、金属等作用下不可避免会发生氧化,从而引起油品变质,轻则影响润滑性能,重则形成油泥和漆膜,腐蚀机械设备,堵塞管路,加快换油频率,增加环境负担。因此,在酯类润滑油使用过程中需要加入抗氧剂以延长润滑油的寿命。目前最常用的润滑油抗氧剂一般为小分子化合物。较小的分子量会使其热稳定性较差、易挥发,从而影响其在高温下的抗氧能力。如何有效地提高抗氧剂的热稳定性,减少挥发造成的物理损失,并提高抗氧化效率,是当前润滑油抗氧添加剂研究的重要方向。本论文期望通过有机抗氧剂与无机纳米材料制备复合抗氧剂,包括通过无机纳米介孔材料对有机抗氧剂进行担载、原位包覆和有机抗氧剂修饰制备纳米材料几个方面。本论文获得的创新性成果如下:(1)以正硅酸乙酯为硅源,在十六烷基三甲基溴化铵形成的胶束模板上,制备得到介孔二氧化硅。以介孔二氧化硅为载体,分别担载商用抗氧剂3-(3,5-二叔丁基-4-羟基苯基)丙酸甲酯和3-(3,5-二叔丁基-4-羟基苯基)丙酸,研究了其作为抗氧添加剂对酯类油癸二酸二异辛酯(DIOS)氧化安定性的影响。结果表明有机抗氧剂经介孔二氧化硅担载后可以使基础油的氧化诱导时间增长,减缓酸值和粘度的增加,有效抑制油品颜色的加深。当复合抗氧剂添加到润滑油中,介孔二氧化硅孔道中的抗氧剂通过扩散进入润滑体系,并随着润滑油体系中有机抗氧剂的消耗不断向润滑体系扩散补充。此外,有机抗氧剂向润滑体系扩散后,在介孔二氧化硅中留下的空余孔道空间可以对油品产生的氧化产物进行吸附。在有机抗氧剂抗氧作用和介孔二氧化硅的缓慢释放和吸附作用的共同结合下,可以有效提高润滑油的氧化安定性。(2)选用介孔氧化铝进一步考察介孔材料与有机抗氧剂制备的复合抗氧剂对油品安定性的影响。首先以异丙醇铝为铝源,聚(环氧乙烷)-聚(环氧丙烷)-聚(环氧乙烷)三嵌段共聚物为模板剂,通过软模板法制备得到介孔氧化铝。然后通过旋转氧弹测试仪、高压示差扫描量热法和烘箱加速氧化实验测定介孔氧化铝担载3-(3,5-二叔丁基-4-羟基苯基)丙酸甲酯的复合抗氧剂对酯类润滑油DIOS氧化诱导时间的影响。结果表明复合抗氧剂可以显著提高酯类油DIOS的抗氧化能力,并在一定程度上延缓油品酸值、粘度和颜色的变化。复合抗氧剂的抗氧机理包括两个方面,包括有机抗氧剂的缓慢释放和孔道结构对氧化产物的吸附作用。(3)为了提高复合抗氧剂在油品中的分散稳定性,在制备二氧化硅的过程中加入抗氧剂3-(3,5-二叔丁基-4-羟基苯基)丙酸甲酯,原位合成二氧化硅包覆有机抗氧剂的有机-无机复合材料。通过红外光谱、透射电镜、热重分析对制备的复合材料的结构和组成进行了分析,结果表明复合材料为包覆结构,有机抗氧剂的含量为70%。分散性实验表明复合材料在DIOS基础油中的溶解分散性良好。通过旋转氧弹法、高压扫描量热法和烘箱加速氧化实验对复合材料作为抗氧剂对酯类基础油的氧化诱导时间、酸值和粘度进行了研究。结果表明复合材料具有较好的抗氧性能,并且可以有效延缓油品酸值和粘度的增加,是一种性能良好的抗氧剂。(4)为了提高复合材料的热稳定性以及在油品中的分散稳定性,利用含可反应官能团的受阻酚抗氧剂3-(3,5-二叔丁基-4-羟基苯基)丙酸(DBHP),通过化学键修饰到无机纳米氧化锌表面(DBHP-ZnO),原位制备有机-无机复合抗氧剂。红外光谱和XPS谱图等结果证明抗氧剂分子通过共价键连接在纳米氧化锌表面。由于微粒表面存在有机抗氧修饰剂,可以提高纳米氧化锌在DIOS中的分散稳定性。此外把DBHP-ZnO纳米微粒作为抗氧剂加入酯类油DIOS中,研究了其对润滑油抗氧能力的影响。结果表明有机-无机复合抗氧剂DBHP-ZnO具有较强的清除自由基的能力,可以显著提高DIOS的氧化安定性。其抗氧机理是由于具有清除自由基能力的纳米氧化锌与有机抗氧剂3-(3,5-二叔丁基-4-羟基苯基)丙酸的协同作用。(5)为了提高在高温下的抗氧能力,修饰剂选用工作温度较高,抗氧耐久性好的二苯胺类抗氧剂(N-苯基邻氨基苯甲酸),通过原位修饰技术中合成了N-苯基邻氨基苯甲酸(Panh)修饰的纳米氧化锌(Panth-ZnO)。研究了溶剂、反应时间以及碱液添加量对其形貌的影响。抗氧性能结果表明得到的有机-无机复合抗氧剂Panth-ZnO可以显著提高酯类油DIOS在高温下的抗氧能力。更多还原

【Abstract】 Lubricants,as the significant and indispensable compositions in the modern mechanical systems,play an important role in ensuring the safety and reliability during the service life of mechanical systems.Along with the enforcement of various more and more restrictive regulations for environmental protection,the development of novel biodegradable lubricants becomes increasingly urgent while the environmental awareness rises all over the world.Driven by this,a series of synthetic ester-based lubricants have been developed due to their high biodegradability,low toxicity,and environmentally benign nature.Their anti-oxidation stability,however,still needs to be improved in association with the reduction in life-cycle cost.But most of the organic antioxidants,especially sterically-hindered phenol and diphenylamine,have small molecular weight,which make them unstable and volatile,which affects the oxidation resistance of lubricating oil at high temperature.This paper is expected to improve the thermal stability of antioxidants through the combination of organic antioxidants and inorganic nanomaterials which includes carrying organic antioxidants through inorganic nano mesoporous materials,preparation of nanomaterials using the method of in situ encapsulation or modification.(1)Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate(brand name T512)was loaded by mesoporous silica nanospheres(MSNs)to afford the antioxidant for synthetic ester lubricant oil.Rotary oxygen bomb tests,pressure differential scanning calorimetry and oven oxidation tests were conducted to investigate the effect of the as-prepared antioxidant on the antioxidant stability of di-iso-octylsebacate(denoted as DIOS).When MSNs are combined with T512 at a properly selected mass ratio,the oxidation of the DIOS base oil is greatly slowed down while the oxidation induction time is significantly prolonged.This may be attributed to the gradual release of T512 from the MSNs and the adsorption of the oxidation products into the channels of MSNs.(2)The mesoporous alumina was prepared by soft template method by using aluminum isopropanol as the aluminum source,poly(epoxy ethane)-poly(epoxy propane)-poly(epoxy ethane)three block copolymer as template.The effects of sintering temperature on the pore structure of alumina were investigated by IR,nitrogen adsorption desorption curves and transmission electron microscopy.The effect of the compound antioxidant of 3-(3,5-ditert butyl-4-hydroxyphenyl)propionate on the oxidation induction time of the ester lubricating oil was studied by a rotating oxygen bomb tester,high pressure differential scanning calorimetry and oven oxidation experiment.The results showed that compound antioxidant could significantly improve the antioxidant capacity of ester oil DIOS,and delay the change of acid value,viscosity and color to a certain extent.The mechanism of oxygen resistance is that organic antioxidants enhance the antioxidant capacity of lubricants through slow release after loading mesoporous alumina.(3)SiO2 coated octyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate(denoted as T512@SiO2)was synthesized.The morphology and microstructure of the prepared sample were analyzed with a transmission electron microscope and a Fourier transfer infrared spectrometer.Moreover,the antioxidant performance of the prepared sample in di-iso-octylsebacate(denoted as DIOS)was evaluated by a series of methods including the oven oxidation stability test,rotary oxygen bomb test and pressure differential scanning calorimetry.All the tests showed that the T512@SiO2 exhibit excellent antioxidant capacity using as antioxidant additive for DIOS and can effectively inhibit the increase of the kinematic viscosity and acid value of oil during the oxidation process.(4)3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionic acid(DBHP)functionalized ZnO nanoparticles were synthesized by in situ surface modification technology.DBHP as an organic hindered phenol antioxidant was used as surface modifier,which can improve the dispersion stability of the prepared composite nanoantioxidant in the lubrication oil and scavenge free radicals produced during the oxidation process of oil.The structure and morphology of the composite antioxidant were investigated by FTIR,TEM,XRD and TG.The results demonstrate the thermal stability of the prepared composite antioxidants is greatly enhanced compared with DBHP.Moreover,rotary oxygen bomb test,pressurized differential scanning calorimetry and free radical scavenging method were utilized to evaluate the antioxidant behaviors of the prepared sample,which can effectively improve the antioxidant stability of the based oil.In addition,activation energy of the oxidation process was analyzed by model-free methods,including Flynn-Wall-Ozawa and Kissinger methods.The results indicated DBHP-ZnO had better antioxidant properties than DBHP under high temperature.更多还原