Joseph M. Perez

Wax appearance temperatures of vegetable oils determined by differential scanning calorimetry: effect of triacylglycerol structure and its modification

Abstract Crystallization and wax appearance temperatures of a series of vegetable oils (natural, genetically and chemically modified) were studied using differential scanning calorimetry (DSC). The fatty acid chains of a triacylglycerol molecule have a bend ‘tuning fork’ conformation and undergo molecular stacking during the cooling process. Wax crystallization at low temperature is controlled by steric and geometrical constrains in these molecules. This study describes an approach to quantify and predict wax appearance temperature of vegetable oils based on the statistical analysis of DSC and NMR data. A molecular modeling program was used to design triacylglycerol molecules with different fatty acid (e.g. oleic and linoleic) chains to illustrate their effect on the crystallization process. Effect of pour point depressant (PPD) additives on vegetable oil crystallization is also discussed.

Oxidative properties of lubricants using thermal analysis

The development of automotive lubricants requires optimization of a number of performance parameters of both base fluids and additive systems. The final test of a lubricant requires that it perform well in a particular application or system. Prior to the final selection of a lubricant, a number of combinations of base fluids and additives need to be evaluated. The most practical way to do this is through inexpensive bench testing. The use of pressurized differential scanning calorimeter (PDSC), thermal gravimetric analysis (TGA) and thin-film oxidation tests will be described in the evaluation of several lubricants. Examples of some practical applications of the thermal methods to the evaluation of alternative fuels and lubricants, and to studies involving extended drain lubricants are reported. Incompatibility of alternative fuels and lubricants can result in significant extraction of some additives. Thermal analysis shows significant variation in stability of the fractions obtained from simulated crankcase tests. Results from some of the methods are compared.

Gear oil formulation designed to meet bio-preferred criteria as well as give high performance

A bio-based gear oil was developed from soybean oil (SBO). The SBO was first thermally polymerised and then mixed with additives and diluents. The effect of pour point depressants, co-base oils, antioxidants and anti-wear additives is reported. Lubricity, viscosity index and oxidation stability of the final formulation of the bio-based gear oil are compared with commercially available gear oils. The final formulation of bio-based gear oil gives test results: viscosity index 165, four-ball wear scar 0.375 mm. These numbers are comparable to or better than the commercially available gear oils tested for comparison. The oxidation onset temperature of the bio-based gear oil, 220°C, is lower than the evaluated commercial products, but still at an acceptable range for gear oil.

Quantitative NMR spectroscopy for the prediction of base oil properties

The performance characteristics of mineral base oils depend largely on their physiochemical properties. These properties in turn are dependent on the type and relative amount of different hydrocarbons present in the system. The physical properties of some molecules are known to be quite different when they are in a mixture and their influence on bulk physical properties of base oils can vary considerably. The evaluation of these properties can involve long procedures, considerable manpower, a large sample and a costly laboratory infrastructure. A rapid method was developed using quantitative 13C NMR derived structural information on a set of Group 1 type base oils. The molecular level characterization is considered more accurate, requiring less time and test sample to study base oil properties. If such structural data are correlated suitably with the bulk physical properties, they can be used as reliable tools for predictive models. A best subset multi-component regression analysis of the NMR data generated on several base oils are used to develop correlations to predict base oil properties such as API gravity, pour point, aniline point and viscosity. The method and some results are reported. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

Oxidation of Biodiesel Fuels for Improved Lubricity

Diesel engine emissions are a source of environmental concern. The use of vegetable oil based fuels, called biodiesels, lowers particulate emissions due to the increased oxygen content of the fuel. This study aims to further increase the oxygen content of biodiesel by oxidizing the fuel, analyzing the resulting product, and determining if favorable lubricity qualities result. Oxidation is performed in a non-catalytic vapor phase reactor at temperatures between 300–400°C. The product is characterized using various analyses including sulfuric acid solubility, density, gas chromatography, bomb calorimetry, and lubricity. Optimum blend ratios of the oxidized fuels in a low sulfur diesel fuel to obtain maximum lubricity are determined.Copyright

Kinetics of Oxidative Degradation: Applicability of Time and Temperature Superposition

New methodology is suggested to quantify the effect of temperature on oxidative degradation and compare test results obtained at different temperatures or evaluate changes in chemical mechanisms. Assumption of the pseudo-first-order kinetics to calculate activation energies in oxidative polymerization of uninhibited 100 percent oleic triglyceride under thin film oxidation provided only semiquantitative results from available oxypolymerization data at six temperatures from 100° to 175°C. As an alternative approach, Time and Temperature Superposition (TTS) was applied to analyze the data. Several TTS forms consistent with Arrhenius equation showed much greater accuracy in determining activation energies and induction periods. Different stages of oxidative degradation were identified after the data from different temperatures were combined into one kinetic map. Kinetic maps of alkali-refined high oleic sunflower oil, fully formulated synthetic oleate-based hydraulic fluid and additive-free super refined mine...

Oil consumption studies in a single-cylinder diesel engine using Solid-film lubricants

Solid-film additives (tungsten disulfide, lead sulfide, and graphite fluoride) were dispersed in a high temperature liquid lubricant, and their performance was evaluated in a single-cylinder diesel engine. Oil consumption and wear of the piston and rings were determined during the tests, and changes in oil properties such as viscosity and total acid number (TAN) were monitored as well. Tungsten disulfide and lead sulfide proved to be effective additives to reduce friction and wear under the operational conditions encountered in the diesel engine. This contrasted with the behaviour of graphite fluoride, which produced high friction and wear. The observed oil consumption correlated with degradation rates of the solid-film additive dispersions as indicated by the TAN, although high abrasion was also observed in the case of graphite fluoride. The use of solid-film additives had no effect on the brake-specific fuel consumption with respect to the reference baseline oil.

Oxidation Studies of Lubricants from Dornte to Microreactors

Friction, wear and the oxidation of lubricants are concerns in most mechanical systems. Selection of the best current thermoanalytical method to evaluate the oxidative performance of a lubricant for an application is an ongoing problem. The variability and complexity of mechanical systems makes correlation with bench tests difficult. The oxidative environment in automotive applications may vary from nil in sealed-for-life components to severe oxidative conditions found in piston, ring, and liner zones. The researchers task is to develop useful and meaningful bench tests to allow the engineer to concentrate his effort and resources on developing better lubricants for a given application. This paper reviews the evolution of oxidation test methods for the past 50 years from large complex systems to the current microanalysis methods. The mechanism of oxidation has changed very little but our understanding of additive interactions has advanced significantly. Additive depletion and the resulting oxidation process can be studied using the microthermooxidative methods. Often, a combination of methods can be used to obtain a better understanding of the thermal and oxidative processes occurring. Some comparisons of the methods and their applications are described.

A review of four-ball methods for the evaluation of lubricants

A review of four-ball wear tester and test methods developed at Penn State by Prof. Emeritus E.E. Klaus (Deceased) and students of Klaus. The test methods include standard methods for fluid and additive evaluation, microliter tests to evaluate tribochemical reactions in the contact zone, Ball-on-Three Flat tests to evaluate materials and fluids, scuffing test methods and sequential four-ball tests, one of which was developed to screen hydraulic fluids for full-scale pump stand tests and field vehicles. Applications range from room temperature to over 425 °C. The variety of methods demonstrate the versatility of the FBWT, including applications related to the tribology of hydraulic fluid systems.