锂基润滑脂热流变特性及其变化机理

采用旋转流变仪探究了变温条件下的锂基润滑脂流动特性和黏弹特性,考察了温度对锂基润滑脂流变特性变化的影响规律,并对热流变过程中壁面滑移效应变化规律进行了讨论。进一步结合锂基润滑脂的微观形貌,探究了锂基润滑脂皂纤维结构与热流变特性变化的关联性。最后基于热流变和皂纤维结构研究结果,分析了锂基润滑脂胶体分散体系结构演化过程,给出了胶体分散体系及壁面滑移效应在热流变条件下的变化机理。     

基于变温下圆管内润滑脂流动特性的表征

为研究温度对润滑脂圆管流动特性的影响规律,采用旋转流变仪分析了润滑脂的流变特性,并基于流变特性研究结果和理论分析建立了润滑脂圆管流的速度场和应力场变化模型。结果表明:润滑脂具有高的屈服剪应力,表现出良好的黏温特性和剪切稀化特性,温度升高润滑脂的屈服应力和表观黏度均下降,表现为更好的流动性;利用MATLAB编程绘图对速度场和应力场分析,给出了润滑脂圆管流动特性规律的影响因素及变化关系;揭示了温度对润滑脂圆管流动特性的影响规律,提高输送介质温度利于润滑脂的输送。     

基于变温下圆管内润滑脂流动特性的表征

为研究温度对润滑脂圆管流动特性的影响规律,采用旋转流变仪分析了润滑脂的流变特性,并基于流变特性研究结果和理论分析建立了润滑脂圆管流的速度场和应力场变化模型。结果表明：润滑脂具有高的屈服剪应力,表现出良好的黏温特性和剪切稀化特性,温度升高润滑脂的屈服应力和表观黏度均下降,表现为更好的流动性;利用MATLAB编程绘图对速度场和应力场分析,给出了润滑脂圆管流动特性规律的影响因素及变化关系;揭示了温度对润滑脂圆管流动特性的影响规律,提高输送介质温度利于润滑脂的输送。     

立磨磨辊轴承装配工艺的改进

1原工艺流程磨辊作为立磨主要的粉磨部件,其轴承的装配精度直接关系到磨辊的使用寿命。所以磨辊轴承的装配是很重要的一个过程。某型号立磨磨辊组件结构及磨辊轴承装配原惯用的工艺流程见图1。     

零维及一维纳米坡缕石对润滑脂的摩擦性能对比

分别制备零维、短纤维状以及长纤维状的纳米坡缕石,添加到锂基润滑脂中,对试样进行四球摩擦试验,以便探究不同形态的纳米坡缕石对润滑脂摩擦性能的影响。结果表明,零维、短纤维状以及长纤维状的纳米坡缕石均能够改善润滑脂抗磨减摩性能;其中含零维及一维的短纤维纳米坡缕石润滑脂的减摩抗磨性能稳定性较好,而长纤维纳米坡缕石润滑脂的减摩抗磨性能稳定性较差。     

冷却器流化空气风机轴承润滑脂异常原因分析及处理

针对尿素装置冷却器流化空气风机检修中发现轴承润滑脂存在局部发黑、进水等异常现象,从轴承自身结构特点及密封件选用两方面,对可能导致异常的原因进行分析排查,提出解决措施。     

破碎机轴承失效原因分析及改造

通过对破碎机轴承的频谱分析、受力分析和载荷核算,得出其损坏的主要原因是轴承选用不当。采取轴承改型以及对轴承座密封和轴承支架进行改进后,取得了较好的运行效果。     

低速重载齿轮箱轴承故障的振动监测及分析

本文使用振动监测进行故障诊断,判断出低速重载轴承的故障,并通过对轴承轴窜量的计算进行了轴承损坏的原因分析,提出了低速重载轴承故障诊断和检修装配的建议。     

立磨减速机断齿原因分析及处理

1前言2008年以前的5000t/d水泥熟料生产线配用的原料立磨减速机,多为FLENDER减速机,近几年曾发生减速机一级弧齿锥齿轮副断齿事故。笔者参与处理过两起KMPS675减速机一级齿轮副弧齿锥齿轮断齿事故。现将事故原因与预防措施阐述如下。     

润滑脂流变性影响因素研究现状

润滑脂由于其复杂而独特的流变性能,近年来受到了学界的广泛关注。学者们选用一系列流变参数来定性定量描述润滑脂的流变性能。润滑脂组分、工作条件及制备手段的变化常常会影响和改变润滑脂的流变参数。综述了温度,稠化剂结构、含量及粒度,基础油,添加剂及填料,制备条件,微观结构等因素对润滑脂流变参数的影响情况,总结了润滑脂流变学发展中存在的问题,并对润滑脂流变学未来的发展进行了展望。     

锂基润滑脂的研制与应用

锂基润滑脂又称长寿命润滑脂。它是由中等粘度润滑油作基础油和氢氧化锂及稠化剂调合而成。根据不同的应用要求再加入适宜的添加剂。制备方法：将硬脂酸、１２－羟基硬脂酸、氢氧化锂、水及润滑油投入反应釜中，经皂化（１４０℃，２小时）、脱水、稀释皂基、加添加剂、冷却、研磨（１１５℃）至成品包装。本文还对基础油、脂肪酸对成品性能的影响和成品的应用进行了探讨。     

基础油和添加剂对复合锂基脂轴承寿命的影响

改变复合锂基脂基础油的种类、粘度及合理选择抗氧剂和极压荆的组合,能有效降低轴承振动、控制温升,进而延长润滑脂的轴承寿命.     

硬脂酸异辛酯在聚氯乙烯加工中的应用及其流变性能的研究

研究了硬脂酸异辛酯(EHO)作为聚氯乙烯树脂增塑剂使用的可能性和适宜用量,以及对聚氯乙烯流变性能的影响。实验结果表明:EHO只能作为聚氯乙烯的辅助增塑剂使用,适宜用量为5～10份;当EHO与邻苯二甲酸二辛酯(DOP)以5:45混合使用时,可提高聚氯乙烯软制品的拉伸强度、断裂伸长率和耐寒性等性能。同时,通过流变性能实验,发现EHO在聚氯乙烯硬塑料中具有良好的润滑作用。     

A Greener Alternative Titration Method for Measuring Acid Values of Fats,Oils, and Grease

A greener alternative method is proposed for measuring acid values (AV) of fats, oils, and grease (FOG) based on visual titration. Compared with Official Method Cd 3d-63 of the American Oil Chemists' Society (AOCS), this greener alternative method can eliminate the use of toluene, which in turn reduces toxicity and cost. A total of 44 samples of yellow and brown grease with AV ranging from 0.13 to 170.37 (mg KOH) g⁻¹ were titrated using both methods. The alternative titration method can provide accurate and reliable results to determine the AV of FOG by various statistical analyses including repeatability, linear regression, f-test, t-test, and method accuracy calibration with AOCS Cd 3d-63. This low-cost method can be recommended for routine titration in research and development, and in biodiesel plants for most FOG samples.     

Rheological and mechanical properties of cross-linked fish gelatins

Gelatin was extracted from the skins of Alaska pollock (Theragra chalcogramma) and Alaska pink salmon (Oncorhynchus gorbuscha). Amino acid analysis and gel electrophoresis were used to determine their amino acid composition and molecular weight profiles, respectively. Dynamic rheology was also used to characterize the fish gelatins’ gelation and melting behavior as well as their cross-linking behavior upon adding genipin and glutaraldehyde. Pollock and salmon gelatin had lower gelation and melting temperatures than that of a commercial porcine gelatin. Both fish gelatins that contained genipin showed faster cross-linking rates for samples with higher pH values. However, salmon samples exhibited greater dependence on pH. Also, pollock gelatin cross-linked faster with glutaraldehyde than with genipin. After five days of cross-linking, all porcine samples had much greater gel strengths than pollock samples. In addition, porcine samples containing genipin had gel strengths several times greater than those containing glutaraldehyde.     

Rheological and mechanical properties of percolated cyanate ester nanocomposites

The rheological properties and mechanical properties of percolated cyanate ester monomer/layered silicate mixtures are reported. A number of different cation exchanged montmorillonites were examined in an effort to achieve maximal montmorillonite delamination. The dispersion throughout the cyanate ester of a montmorillonite with phenylated ammonium cations (2MBHT MMT) results in the formation of a percolated network. The rheology of this percolated network undergoes a viscous liquid to elastic solid transition at 4 wt% montmorillonite. The percolation of the montmorillonite in the cyanate ester results in a significant improvement in crack resistance (80%) without a sacrifice of flexural strength.     

Rheological characterization of polystyrene-clay nanocomposites to compare the degree of exfoliation and dispersion

Polymer-clay nanocomposites are of great interest due to their improvement in certain material properties relative to virgin polymer or conventional composites. For example, compared to conventional materials, Nylon 6/montmorillonite nanocomposites demonstrated significant improvements, including high strength, high modulus and high heat distortion temperature. Because viscoelastic measurements are highly sensitive to the nanoscale and mesoscale structure of polymeric materials, when combined with X-ray scattering, electron microscopy, thermal analysis, and mechanical property measurements, they will provide fundamental understanding of the state and mechanism of exfoliation of the layered silicate (clay) in a polymer matrix. In addition, understanding rheological properties of polymer nanocomposites is crucial for application development and understanding polymer processability.The objective of this research is to develop a rheological technique to analyze the clay morphology in nanocomposite. Previous work has demonstrated the utility of the rheological technique to differentiate (qualify) the degree of exfoliation/dispersion. This report utilizes findings from the earlier work to further map out the structure-rheological response of polystyrene nanocomposites with various composition, clay types, and dispersion; and to quantify the key parameter that dominates the characteristic rheological response. This report explored a series of polystyrene (PS)-clay nanocomposites with 1,2-dimethyl-3-n-hexadecyl imidazolium (DMHDI) organically modified clays. These PS nanocomposites investigated here demonstrated a change of pattern in dynamic mechanical spectrum, as a function of the degree of exfoliation, from typical polymer response to a terminal response of [G′∼ω, G″∼ω], then to a pattern with double crossover frequencies, and finally to a solid-like response with G′>G″ in all frequency ranges. We showed that the number of particles per unit volume is a key factor determining the characteristic response of nanocomposites.In addition, the rheological response of PS-clays nanocomposite made from DMHDI modified clay combined with high-energy sonication (characterized as exfoliated by XRD and TEM) was compared with that of nanocomposites made by dimethyl, benzyl hydrogenated tallow (2MBHT) modified clay. We found that PS nanocomposites made by DMHDI-modified clay with high-energy sonication are better dispersed than the nanocomposites made previously using 2MBHT-modified clay. We also showed that the glass transition temperatures were not very sensitive to the degree of dispersion.The key finding of this research is that rheological measurements are complimentary to traditional polymer nanocomposite analysis techniques, and they may also serve as an analytical tool by itself (under appropriate conditions), now that some fundamental behavior has been identified.     

Effects of Fats and Oils on Rheological, Fatty Acid Profile and Quality Characteristics of South Indian Parotta

Keeping in view the present day demand for foods with healthy fats, the effect of different fats namely hydrogenated fat (HF) and bakery fat (BF); oils—sunflower oil (SFO), soyabean oil (SBO), olive oil (OLO), palm oil (POO) and coconut oil (CNO) separately at the level of 7.5 % on the rheological, fatty acid profile and quality characteristics of parotta was studied. Addition of fats and oils decreased Farinograph water absorption, Amylograph peak viscosity, Alveograph resistance of dough to deformation and increased average abscissa at rupture. In the micrographs of parotta dough with fats, the protein matrix appeared thick and intact, whereas in the case of parotta dough with oils the protein matrix appeared slightly less intact. The spread ratio and overall quality of parotta with oils were higher than fats. The highest overall quality score was observed for parotta with OLO, followed in decreasing order by SFO, SBO, CNO, POO, HF and BF. Determination of fatty acid profile showed that the parottas with fats contained a high amount of trans fatty acids (TFA), while parottas with oils had no TFA. During storage up to 48 h, the parottas with oils remained softer than the parottas with fats.     

Oolichan Grease: A Unique Marine Lipid and Dietary Staple of the North Pacific Coast

Oolichan grease, a dietary fat prepared from smelt-like fish, is highly prized by north Pacific coast aboriginal cultures. The composition of oolichan grease is unclear, with one report indicating a high 22:6n-3 content consistent with cold-water marine oils, but another reporting a much lower value. We noted that oolichan grease remains solid up to 15 degrees C, suggesting a low polyunsaturate content. After extracting total lipids from four fresh oolichan fish and four samples of grease, fatty acids were quantitated by high resolution gas chromatography (GC), as were additional samples of fish lipid and grease that were fractionated into triglyceride (TG), phospholipid (PL), and free fatty acids by thin-layer chromatography. In contradistinction to one prior report, we found EPA and DHA in fresh fish total lipids to be 0.9 and 2.2 wt%, respectively, while in the extracted grease, both were reduced to 0.5 wt%. Only the fresh fish PL fraction contained appreciable DHA. The bulk of the grease consisted of saturated fatty acids (30.3 wt%) and mono-unsaturates (55.0 wt%), explaining its high melting point. Excepting its very low omega-6 content (<2 wt%), oolichan grease is quite similar in composition to human adipose TG. Its solid state at environmental temperatures and low peroxidizability index made it suitable for storage and transport, explaining its status as a preferred trade item among regional aboriginal groups.