线性扫描伏安法检测润滑油中抗氧剂含量的研究

润滑油中抗氧剂含量决定着润滑油的剩余寿命,研究一种抗氧剂含量快速、简便的测量方法对于润滑油研究十分重要。研究线性扫描伏安法测定润滑油中抗氧剂含量的原理和方法,基于普林斯顿电化学工作站,探讨电解质溶液和扫描速率对测量体系中抗氧剂产生特征伏安峰的影响。结果表明,扫描速率为5 mV/s时,酚类和胺类抗氧剂在含有十二烷基磺酸钠、乙醇和硫酸的电解质溶液中都出现了特征伏安峰,并且抗氧剂的特征伏安峰高与抗氧剂浓度显示出正相关趋势,表明采用线性扫描伏安法测定润滑油中抗氧剂含量是可行的。线性扫描伏安法快速简便,可用于合成油和矿物油中抗氧剂含量的测定,该方法在合成油和矿物油中T501抗氧剂随着老化时间的延长而不断消耗的表征中取得良好效果     

利用超微电极测定润滑油中的抗氧剂

近年来,利用超微电极在不良电导介质中进行电位测定的技术已有突破性的进展。应用这一方法来监测润滑油中的抗氧剂,看来是很合适的。作者发现,只要将润滑油/抗氧剂溶液加入到乙腈中,所得的溶液就具有足够的电导,可以用电位法有效地来测量抗氧剂的浓度。     

某航空润滑油中抗氧剂的衰减研究

利用气相色谱,通过外标法定量分析某飞机发动机在用润滑油中低温抗氧剂和高温抗氧剂的衰变规律;利用加速氧化试验,探讨高温抗氧剂的热氧化动力学。结果表明:该航空润滑油在使用中,高温抗氧剂基本能维持在一定水平,其热氧化衰变过程近似为一级反应;补油可明显延缓润滑油高温抗氧剂的衰减速率,且补加油情况对抗氧化性能有一定影响;低温抗氧剂在使用中衰减比高温抗氧剂要快得多;通过检测润滑油的黏度和总酸值变化,可以监控航空润滑油的氧化衰变,从而有效保障飞机发动机的润滑油使用安全。     

红外光谱法测定润滑油中抗氧剂T501含量

介绍用红外光谱法快速测定润滑油中抗氧剂含量，在3650cm^-1处做为T501的测量峰，利用外标法测定，并考察了胺类、醇类等添加剂对T501的干扰。重点考察了方法的准确性，并同时与液相色谱做对比，结果令人满意。     

高压差热扫描分析技术在润滑油热氧化研究中的应用

对某型航空润滑油进行热氧化模拟试验 ,应用高压差热扫描分析仪 (PDSC)和GC评价润滑油中抗氧剂N-苯基 -α萘胺 (NPAN)的热氧化衰变程度。结果发现在该润滑油热氧化衰变过程中 ,1nCNPAN与PDSC的OIT (氧化诱导期 )具有极佳的线性相关性 ,表明PDSC是研究润滑油热氧化的理想手段     

高压差热扫描分析技术在润滑油氧化研究中的应用

对某型航空润滑油进行热氧化模拟试验，应用高压差热扫描分析仪（PDSC）和GC评价润滑油中抗氧剂N－苯基－α萘胺（NPAN）的热氧化衰变程度。结果发现在该润滑油热氧化衰变过程中，lnCNPAN与PDSC的OIT（氧化诱导期）具有极佳的线性相关性，表胆PDSC是研究润滑油热氧化的理想手段。     

润滑油抗氧化剂的作用机理及抗氧化剂的选择

该文介绍了润滑油使用过程中导致其氧化的影响因素和所形成氧化物对使用性能的影响,以及润滑油基础油的氧化机理,叙述了酚类,胺类抗氧化剂作用机理,并对酚类、胺类中经典的抗氧剂进行了评价。     

润滑油的抗氧化性能和分析检测技术

针对润滑油的抗氧化性能的要求 ,讨论了抗氧化性能对机器设备润滑的重要性 ,并介绍了几种常用的润滑油抗氧剂的作用机理和润滑油的抗氧化测试方法 ,并讨论了可用于润滑油氧化分析的现代分析测试技术。     

某型航空发动机润滑油的热氧化安定性研究

通过高温高压反应釜实验模拟发动机实际工况条件,研究不同氧化温度对以聚α-烯烃合成油为基础油、2,6-二叔丁基对甲酚和对,对’-二异辛基二苯胺为抗氧剂的某型航空润滑油理化性能的影响,并根据润滑油高温氧化后产物的结构组成,分析PAO航空润滑油的氧化衰变机制。结果表明:温度越高,该型航空润滑油产生的小分子越多,黏度降低,酸值增大;抗氧剂的加入可以明显减缓油品黏度的衰减过程,并抑制小分子异构烷烃和烯烃的生成;在高温氧化衰变过程中,PAO基润滑油的高温氧化衰变经历了自由基反应历程。     

发动机润滑油的电化学分析与鉴别

采用微分脉冲伏安法在0．01mol／L高氯酸锂的杉乙醇／乙酸溶液体系下研究了发动机润滑油的电化学特性。结果表明：润滑油的电化学分析数据具有很好的特征性，采用微分脉冲伏安法可快速获得在用润滑油中抗氧剂残留量，对润滑油的剩余使用寿命作出评价。利用Access2003和Visual C＋＋建立了润滑油鉴别分析系统，实现了对润滑油电化学分析数据的管理、查询和未知润滑油的鉴别。     

Evaluation of potassium trifluoroacetylacetonate as a synergist for arylamine antioxidant in synthetic lubricants

Differential scanning calorimetry (DSC) was employed to evaluate the performance of an ester lubricant containing potassium trifluoroacetylacetonate. In the isothermal DSC oxidation test, potassium trifluoroacetylacetonate is an effective synergist for arylamine antioxidants such as p, p'-dioctyldiphenylamine (DODPA). In combining with arylamine antioxidants, potassium trifluoroacetylacetonate can also effectively reduce the increase in viscosity and acid number of the ester oil in oxidation-corrosion tests. The electron paramagnetic resonance (EPR) results indicated that potassium trifluoroacetylacetonate can reduce the free radical content in the oxidised oil when arylamine antioxidants are present.     

A comparative study of phenol‐type antioxidants in methyl oleate with quantum calculations and experiments

Chemical software (Gaussian 98w) was used to calculate the highest occupied molecular orbital (HOMO) energy level of three phenol‐type antioxidants to evaluate their oxidation resistance performance. The conclusion drawn from the quantum calculations was that the decreasing order of the oxidation resistance effectiveness was 4,4‐methylene‐di(2,6‐di‐t‐butyl‐phenol) (T511)>2,6‐di‐t‐butyl‐4‐methylphenol (BHT)>phenol. Pressure differential scanning calorimetry (PDSC) and the rotary bomb oxidation test were also used to assess the antioxidants in a methyl oleate base oil. According to the experimental results, the oxidation resistance capability of the three antioxidants decreased in the order BHT > T511 > phenol. The results indicated that the quantum calculation method could be used to screen antioxidants with regard to their oxidation resistance effectiveness.     

The response to antioxidants in base oils of different degrees of refining

Base oils with different compositions and different degrees of refining have been subjected to three types of oxidation stability tests in the presence of antioxidants. A higher degree of refining of base oils depletes the natural antioxidants present in oils of lower degree of refining. However, the results of the study show that oxidation stability of highly refined oils, after addition of suitable antioxidant packages, by far outperforms that of the oils of lower degree of refining. This is true regardless of the dominating hydrocarbon type in the oil, or its feedstock origin. The results also show that in general, the viscosity index of a base oil, or any other simple physical property, has no direct correlation to oxidation stability or response to antioxidants. To analyse the response to antioxidants, a concept called oxidation stability response is introduced. A novel method for determining the oxidation onset temperature in differential scanning calorimetry measurements by inverse derivatives is introduced. Copyright © 2007 John Wiley & Sons, Ltd.     

Antioxidation Synergism between Alkali Metal Salts and Arylamine Compounds in Synthetic Lubricants

Differential scanning calorimetry (DSC) was employed to evaluate the performance of an ester lubricant containing alkali metal salts. In the isothermal DSC oxidation test, the alkali metal salts of perfluorobutyric acid are effective synergists for arylamine antioxidants such as p, p′-dictyldiphenylamine (DODPA). Among the salts, the order of synergistic effectiveness is K > Na > li. When used in combination with arylamine antioxidants, the Na and K slats can also effectively reduce the increases in viscosity and acid number of the ester oil in oxidantion-corrrosion test. The electron paramagnetic resonance (EPR) results indicated that the alkali metal salts can reduce the free radical contents in the oxidized oil with arylamine antioxidants present.     

凝胶渗透色谱-高效液相色谱法测定食品中的8种抗氧化剂

建立凝胶渗透色谱净化-反相高效液相色谱法同时测定8种抗氧化剂的分析方法。样品经乙酸乙酯-环己烷(1:1,V/V)振荡提取、凝胶渗透色谱净化、以及C_(18)色谱柱线性梯度分离后用高效液相色谱分析,其中流动相为1%乙酸溶液和乙腈。实验结果表明:8种抗氧化剂分离效果良好,样品回收率为75.62%～104.19%,相对标准偏差为0.17%～8.91%,检出限为0.31～1.46μg/g。     

Effect of antioxidants on the oxidative stability and combustion characteristics of biodiesel fuels in an indirect-injection (IDI) diesel engine

Biodiesel fuels that consist of saturated and unsaturated long-chain fatty acid alkyl esters are an alternative diesel fuel produced from vegetable oils or animal fats. However, autoxidation of biodiesel fuels during storage is easily caused by air, reducing fuel quality by adversely affecting its properties such as kinematic viscosity and acid value. One approach to improve the resistance of biodiesel fuels to autoxidation is to mix them with antioxidants. This study investigated the effectiveness of five such antioxidants in mixtures with biodiesel fuels produced by three biodiesel manufacturers: butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), propyl gallate (PrG) and α-tocopherol. An engine test was also performed to investigate the combustion characteristics of biodiesel fuel with antioxidants in an indirect-injection (IDI) diesel engine. Oxidation stability was determined using Rancimat equipment. The results showed that TBHQ, BHA, and BHT were the most effective and α-tocopherol was the least effective in increasing the oxidation stability of biodiesel. The combustion characteristics and exhaust emissions in diesel engine were not influenced by the addition of antioxidants in biodiesel fuel. This study recommends TBHQ and PrG to be used for safeguarding biodiesel fuel from the effects of autoxidation during storage.     

Oxidative stabilisation of synthetic fluids and vegetable oils

The use of ashless antioxidants to increase the useful working life of synthetic fluids, such as polyalphaolefins, polyalkylene glycols and carboxylic acids, is discussed, and some general guidelines are proposed. The application of ashless antioxidants in controlling the oxidative degradation of several different types of biodegradable vegetable oil is illustrated. The action of the naturally occurring antioxidant, vitamin E, in some of these fluids has been examined and some preliminary results are reported.     

热裂解-气相色谱质谱联用法快速检测聚丙烯材料中5种抗氧剂

采用热裂解气质联用仪,建立了一种无需任何样品前处理、全程无溶剂的、同时对5种常用塑料抗氧剂的定量分析方法.结果表明:通过该方法分析的5种常用抗氧剂,在0.2～1μg之间有很好的线性关系,且该方法操作简单、 快速准确,填补了热裂解气质联用技术在塑料助剂定量分析的空白.     

Benefits of antioxidants in lubricants and greases assessed by pressurised differential scanning calorimetry

The long‐term thermo‐oxidative stability of lubricants and greases is a prerequisite to meet today's ‘stay in grade’ and extended drain interval requirements. To achieve this goal, there is a need for a better understanding of thermo‐oxidative lubricant degradation and of how antioxidants can affect this process. In this paper a two‐stage degradation model is discussed. Primary degradation leads to the formation of very reactive species such as radicals and peroxides. These are the precursors for generating secondary degradation products, such as oligomers, sludge, or deposits. By applying the theory of reaction kinetics and the Arrhenius law, quantitative correlations may be derived between oxidation induction time (OIT) and temperature, and between OIT and antioxidant treat level. Pressurised differential scanning calorimetry (PDSC) data confirm these theoretical findings and demonstrate the benefit of the addition of aminic antioxidants in comparison with high‐molecular‐weight hindered phenolic antioxidants.     

Interaction of different types of additive with oil-soluble metal salts - homogeneous catalysts of oxidation

The interaction of zinc dithiophosphate and phenolic antioxidants with metal naphthenates, mainly with copper naphthenate, has been investigated. A complex compound is formed on the interaction of zinc dithiophosphate with copper naphthenate; this has a noticeable influence on the antioxidation effectiveness of zinc dithiophosphate. The possibility of increasing the antioxidising action of zinc dithiophosphate through its combination with a copper passivator is shown. The formation of complex compounds on the interaction of phenolic antioxidants with copper naphthenates depends on the structure of these additives.