Recipient Organization
IOWA STATE UNIVERSITY
2229 Lincoln Way
AMES,IA 50011
Performing Department
MECHANICAL ENGINEERING - ENG
Non Technical Summary
Future automotive sectors, especially electric vehicles (EVs), require efficient and highly customized lubrication technologies for heavy-duty, high torque, and acceleration operations. The contact conditions, referred to as the boundary-lubrication regime, are where the direct contacts between the mating surface asperities under low lubricating film thickness affect friction and wear behavior. Biolubricants are produced from renewable, non-toxic, and biodegradable natural resources, such as vegetable and animal-based oils. Due to competing land availability for food production and increased price of vegetable oil-based lubricants, there is a need to find alternate resources and processes that can be readily available, economically justifiable, and environmentally friendly to formulate biolubricants. Waste Cooking Oils (WCO), which are two to three times cheaper than raw vegetable oils, can play a crucial role in this aspect. There are a few to no systematic investigations evaluating WCO's potential as an efficient lubricant. We plan to derive lubricant base oils after proper filtration and chemical modification of WCOs in this project. Select ionic liquid additives will be mixed with this chemically modified base oil to enhance its tribological and thermo-oxidative behavior. A set of rheological, corrosion, thermo-oxidative, and tribological investigations will be performed on the WCO-derived base oils and IL additized formulations, then compared to traditional EV transmission fluids to evaluate the potential of the WCO-derived lubricants as the next generation EV lubricant. A set of profilometry and microscopy techniques will be performed to correlate the physio-chemical and lubrication properties of the novel formulated lubricants with their friction and wear behavior.
Animal Health Component
20%
Research Effort Categories
Basic
80%
Applied
20%
Developmental
(N/A)
Goals / Objectives
We plan to first derive a proper filtration protocol to remove the suspended/undissolved food residues from the WCO to be used as a cheap feedstock for lubricant formulation. We will then chemically modify WCO and additize it with select additives to enhance its tribological behavior. We hypothesize that targeted chemical modification and additives can allow WCO to be used as an EV transmission fluid. The copper compatibility, thermal-oxidative stability, viscosity, and low temperature flow properties of pure WCO, chemically modified WCO, and IL additized formulations will be studied. The formulated oils' rheological properties will then be evaluated to understand the lubricants' viscosity. Reciprocating friction and wear testing at different test conditions will be conducted to evaluate the tribological behavior of the formulated lubricants. The overarching long-term goal is to develop fully formulated EV-compatible transmission fluids composed of WCO-derived base oil and selected additive packages.
Project Methods
The project encompasses strategically ddefined six major tasks as described briefly below:Task 1: Synthesis of WCO-based biolubricant base oils WCO samples will be collected from 2-3 different sources, and chemical and physical properties will be analyzed. The pretreatment process includes gravitational filtration to remove the suspended and undissolved food residues. The cleaned WCO will be subjected to acid-catalyzed transesterification to generate fatty acid alkyl esters (FAAE). FAAE with unsaturated carbon-carbon bonds will be skeletally isomerized to produce branched-FAAE (b-FAAE).Ammonium cationic zeolite will be used which requires only heat treatment for its activation and re-activation offering an eco-friendly procedure. Other commercially available zeolites (e.g., Na+ or K+ cationic zeolite) require acid treatment for their activation/reactivation generating acid waste. Reusability of the catalyst will also not only offer a cost-effective, but green process for producing b-FAAE. Methyl branching on b-FAAE will be delocalized due to the resonance character of the carbocation intermediate produced during the reaction and thus produce an isomeric mixture of b-FAAE.?Task 2: Formulation and characterization of IL additized WCO derived lubricants Chemically modified WCO is a complex mixture that contains additional chemicals and WCO with modified chemical bonding. A systematic study that presents the physio-chemical and lubrication characteristics of IL additized chemically modified WCO does not exist in the literature to the best of our knowledge. We will prepare novel biolubricants by mixing two select phosphonium cations ([P8888] [DEHP] and [P4444] [DEHP]) but same anion based ILs with chemically modified WCO (0.5-3 weight percent IL).Task 3: Rheological, corrosion, and thermo-oxidative behavior of the formulated lubricants The formulated lubricants will be analyzed for density, absolute and kinematic viscosity at 40 and 100°C to determine the viscosity index.Copper corrosion will be studied to analyze the lubricant's corrosion potential as per ASTM D130.The oxidation stability of the formulated lubricant will be analyzed using a pressure differential scanning calorimeter (PDSC) as per ASTM D6186. Oxidation onset temperature (OTT) and oxidation induction times (OIT) will be determined from the thermogram at the start of the peak. The top 10% of the formulations with higher oxidation stability will be subjected to the Rotating Pressure Vessel Oxidation Test (RPVOT) following ASTM D2272 with some modifications after screening using PDSC.Task 4: Large-scale formulation of chemically modified base oils from WCO The purpose of this task is to develop a design methodology for the scale-up of the conversion process consisting of (1) WCO refinement and (2) refined WCO conversion to ester products. We have demonstrated the large-scale synthesis of soybean oil EDE esters up to a 10L scale. We will scale up b-EDE product synthesis from WCO derived b-FAAE using a similar approach. Reactor design options are (a) a batch-reactor with a specific reaction time; (b) coupled heat and mass transfer with the reaction in a Reactive Distillation model; and (c) a Continuous Stirred Tank Reactor (CSTR).Task 5: Reciprocating sliding wear characteristics of the formulated lubricants The primary objective of laboratory-scale tribological testing is evaluating surface protection for gears and bearings in an EV drivetrain that results from using ecofriendly WCO-derived, chemically modified, and IL additized lubricants as a function of applied load, sliding frequency, and operating temperature. The friction and wear behavior of the fabricated samples in dry and lubricated conditions will be evaluated using Ducom UniTest reciprocating test rig.The test rig can measure in-situ applied normal force, resultant friction force, contact resistance, and lubricant temperature during the experiments.Wear tracks will be analyzed using a Zygo 3D optical surface profilometer, which works based on the white light interferometry technique and can resolve height differences up to 0.001 μm. High-resolution SEM imaging and EDS elemental analysis will be conducted to reveal the wear mechanisms.Task 6: Characterization of test samples after tribological testsIt is necessary to characterize the experimental surfaces properly for different lubricant cases to correlate the observed friction and wear behavior to the surface protection mechanisms provided by WCO-derived lubricants. Three different approaches will be pursued to determine the lubricant's working mechanisms. (1) The white light interferometry-based technique will be used to generate three-dimensional height maps of the worn-out regions from the contacting ball and flat samples to quantize the variation in ball and flat wear volumes under different lubrication conditions. (2) High-resolution SEM imaging can reveal wear track morphologies under different lubricated conditions. EDS spectroscopy-based spectrum analysis and elemental mapping will allow us to capture wear mechanisms by evaluating the material transfer between the tribopairs. These imaging methods will give us a broad overview of the formed tribofilms on the ceramic (Si3N4) ball and steel (AISI 52100) flat samples. (3) Focused Ion Beam (FIB)-Scanning Transmission Electron Microscopy (STEM)-based analysis of extracted thin slices from the wear scar regions of the steel flat samples will help us further understand the lubricant working mechanisms and potential tribofilm formation along with its composition and morphology.