The global polyurethane market size was valued at USD 72.82 billion in 2021 and is expected to expand at a compound annual growth rate (CAGR) of 4.3% from 2022 to 2030. Over 24 million metric tons of polyurethane were used globally in 2021. Utilizing soybean oil for such a huge industry will generate a demand of ~ 15 million metric tons of soybean oil (over 3 billion soybean bushels) per year. The demand for such a large quantity of soybeans per year will provide huge economic benefits to the soybean farmer and the Kansas Soybean Commission.

The main objective of this proposal is to provide value-added applications of soybean oil for polyurethane industries. Polyurethanes (PU) are of great interest since they represent one of the largest categories of plastics by demand, with applications ranging from construction to the automotive and furniture industries. The global polyurethane market size was valued at USD 72.82 billion in 2021 and is expected to expand at a compound annual growth rate (CAGR) of 4.3% from 2022 to 2030. Over 24 million metric tons of polyurethane were used globally in 2021. Utilizing soybean oil for such a huge industry will generate a demand of ~ 15 million metric tons of soybean oil (over 3 billion soybean bushels) per year. About 55% and 10% of polyurethanes are used for foams and coatings & adhesives, respectively. Traditional polyurethane synthesis stems from the polyaddition reaction of diisocyanates and diols, both of which are largely derived from fossil fuel sources. The isocyanates are produced from hazardous and toxic phosgene gas by the phosgenation process. Phosgene is an extremely toxic gas. Additionally, the isocyanates are toxic and moisture-sensitive and cannot be prepared without sophisticated safety devices, thus posing serious environmental and human health risks. Consequently, a strong thrust has been directed to PUs that avoid diisocyanates and have a reduced carbon footprint.
This proposal provides a solution to both problems. We propose to synthesize non-isocyanate polyurethanes (NIPU) using soybean oil-based compounds as a substitute for petrochemical-based polyols. We will also use carbon dioxide during the synthesis of NIPU which is a global warming gas. The conversion of CO2 into value-added and safe chemicals is very attractive to industries and environmental protection agencies. Soybean oil based NIPU will be used to prepare foams, coatings, and adhesives for commercial applications.

There has been increased demand for the utilization of renewable materials for industrial applications. Soybean oil will be applied for value-added applications in polyurethanes, coating, and adhesive industries. The global polyurethane market size was estimated at over $72 billion in 2021, exhibiting a CAGR of 4.3% over the forecast period of 2022-2030. The market is driven by the presence of stringent environmental regulations designed by various regulatory bodies. Environmental concerns are likely to continue playing a key role in the formulation and use of these materials. The proposed research on soybean oil-based value-added materials will provide new pathways to utilize a large quantity of soybean oil providing greater value for the soybean farmers. The initial seed money from the Kansas Soybean Commission will help us to develop technology for commercialization. The societal impact of this project is significant as this proposal provides an opportunity for students to be involved in research, education, and product development. The outcome of this research will be used for business development, which will provide economic development to the State of Kansas. We expect to have a patent, two graduate thesis, and three peer-reviewed publications. The outcome of the project will be presented in seminars at Pittsburg State University and at conferences (after protecting intellectual properties). These seminars will be opened to the public to enhance community involvement in science and education. This will be a great platform to create public awareness regarding the value-added applications of soybean oil.

Updated January 15, 2024:
Summary of the Worked Performed
The main objective of this project is to provide value-added applications of soybean oil for polyurethane industries. Polyurethanes (PU) are of great interest since they represent one of the largest categories of plastics by demand, with applications ranging from construction to the automotive and furniture industries. The traditional polyurethane synthesis stems from the polyaddition reaction of diisocyanates and diols, both of which are largely derived from fossil fuel sources. The isocyanates are produced from hazardous and toxic phosgene gas by the phosgenation process. Phosgene is an extremely toxic gas. Additionally, the isocyanates are toxic and moisture-sensitive and cannot be prepared without sophisticated safety devices, thus posing serious environmental and human health risks. Consequently, a strong thrust has been directed to PUs that avoid diisocyanates and have a reduced carbon footprint.

During this period, we prepared non-isocyanate polyurethanes (NIPU) using soybean oil. For this soybean oil was chemically modified to epoxidized soybean oil using a facile approach. The epoxidized soybean oil was reacted with carbon dioxide (CO2) to synthesize carbonated soybean oil which was used to react with a diamine to prepare non-isocyanate polyurethanes. The prepared materials were characterized using standard methods to confirm the formation of desired chemicals. The carbonated soybean oil was used to prepare non-isocyanate polyurethane foams. The properties of the non-isocyanate polyurethane foams were tuned by varying the experimental conditions. Our results suggest that soybean oil can be chemically modified to be used for the preparation of non-isocyanate polyurethane foams. The use of carbon dioxide and soybean oil for the preparation of non-isocyanate polyurethane foams will be very attractive to industries due to low cost and government/environmental agencies as it is a green synthesis process that reduces greenhouse gas.

Detailed Report of the Work Performed
For the preparation of non-isocyanate polyurethane foams, soybean oil was used as the starting material. Soybean oil was purchased from a local Walmart in Pittsburg, KS. Soybean oil was epoxidized using a facile approach. For this, a molar ratio of soybean oil: acetic acid: hydrogen peroxide of 1:0.5:1.5 was used. 300 g of soybean oil, 75 g of amber lite resin, and 150 ml of toluene were thoroughly mixed at room temperature for 15 to 20 minutes using a mechanical stirrer in a three-neck round bottom flask attached to the condenser and thermometer. After cooling down the system to 5-10 °C 43.9 ml glacial acetic acid was added to the mixture in the dropwise manner and stirred the mixture for another 30 minutes. After adding 180 ml of peroxide (30%) the mixture was again stirred for 7 hours at 70°C. Following the mixture was allowed to cool down to room temperature and the amber lite resin was decanted and filtered out. After that, the soybean oil and aqueous layers were separated by gravity while being washed 7 to 8 times with 10% brine solution. To remove the excess solvent in the soybean oil the anhydrous sodium sulfate was used as a drying agent, followed by, rotary evaporation to dry the synthesized epoxidized soybean oil.

For the synthesis of carbonated soybean oil, the synthesized epoxide soybean oil and CO2 were reacted in the presence of tetrabutylammonium bromide as a catalyst. For this, 300 g of epoxide soybean oil and 12.5 g of tetrabutylammonium bromide were transferred into the Parr reactor under a CO2 pressure of 3.79 MPa. The reaction was carried out for 48 hours at 110° C and 1100 rpm stirring speed.

International Organization for Standardization (ISO) and American Society for Testing and Materials (ASTM) methods were used to characterize the synthesized epoxide and carbonated soybean oil. The Hanus method based on IUPAC 2.205 was used to determine the iodine value of the soybean oil and epoxidized soybean, which was 127.01 and 3.01 g I2/100g, respectively. The reduction in the iodine value indicates the successful modification of soybean oil. The percentage of oxirane oxygen was measured using glacial acetic acid and tetraethylammonium bromide and crystal violet indicator for epoxide soybean oil and carbonated oil which was 7.10% for synthesized epoxidized soybean oil but after modification, the value was decreased to 0.28%. The hydroxyl number was determined by the phthalic anhydride pyridine (PAP) method based on IUPAC 2.241. The hydroxyl value of carbonated soybean oil was almost zero. To determine the acid value, an indicator method was used according to the IUPAC 2.201 standard, and the observed acid value for soybean oil, epoxide soybean oil, and carbonated soybean oil was 0.69,0.86, and 5.38 mg KOH /g accordingly. Using an AR 2000 dynamic stress rheometer (TA Instruments, New Castle, Delaware, USA), the viscosity was examined by raising the shear stress from 1 to 2000 Pa. The rheometer came with a cone plate with a 2° angle and a 25 mm diameter cone. The viscosity of soybean oil, epoxidized soybean oil, and carbonated soybean oil was 0.033, 0.17, and 215 Pa.s, respectively. The details of the characteristics of soybean oil, epoxidized soybean oil, and carbonated soybean oil are provided below.

The synthesized epoxidized soyabean oil and carbonated soyabean oil were structurally characterized using Fourier-transform infrared (FT-IR) spectroscopy and Gel Permission Chromatography (GPC) spectroscopy. FT-IR spectroscopy was used to determine the presence of functional groups. A PerkinElmer Spectrum Two FT-IR Spectrometer was used to determine the changes in the structure of soybean oil after the modification into carbonated soybean oil. The stretching vibration of =C-H at 3010 cm-1 wavelength corresponds to the carbon-carbon double bonds (C=C) in the soybean oil. This peak disappeared in the epoxide soybean oil after the epoxidation process and a new peak of the epoxy ring (C-O-C) was observed at 820 cm-1 which indicates the successful modification of soybean oil into epoxide oil. After the modification of CSBO from ESBO the new sharp peak was observed at 1801 cm-1 wavelength was corresponds to the (-C=O) carbonyl group and the peak of the epoxide group disappeared after the conversion which indicates the successful modification of CSBO from ESBO.

The conversion of the soybean oil into epoxidized soybean oil and carbonated soyabean oil was further confirmed using gel permeation chromatography. As per the GPC curves, the retention time of soybean oil was 32.05 min which was lower than the epoxidized soybean oil 32.32 min which suggests a change in the soybean oil after epoxidation and carbonation.

Synthesis of Non-Isocynate Polyurethane Foams:
After the successful synthesis of epoxidized soyabean oil and carbonated soyabean oil, non-isocyanate polyurethane foams were prepared. For this, 10 g of carbonated soybean oil (CSBO) was taken in a hard plastic cup followed by the addition of 10 wt.% surfactant B8404, 20 wt.% of ethylene diamine (EDA), and different wt.% of NaHCO3 (1 wt.%, 5 wt.% and 10 wt.%) (all weight percentage was taken in respect of CSBO) was added and vigorously stirred the mixture by using mechanical stirrer for 2 min. After the homogenous mixture, the reaction mixture was allowed to room temperature for 24 hours, for batter curing foam was cured in the oven for a further 24 hours at ~ 50°C. The characterization of the foams is ongoing and a detailed report will be provided in the next six-monthly report. The project is going very well and is on schedule.

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Updated August 5, 2024:
This study examines the impact of blowing agent percentages (5,10,15, and 20%) and curing times (RT, 6, 12, 24, and 48 hours) on the microstructure and mechanical properties of non-isocyanate polyurethane (NIPU) foam. The NIPU foam was synthesized using carbonated soybean oil (CSBO) and ethylene diamine (EDA), with varying NaHCO3 concentrations added as a blowing agent. After initial mixing, the foam was cured at room temperature for 24 hours, followed by further curing at 50°C for various durations. Scanning Electron Microscopy (SEM) analysis revealed that longer curing times resulted in more uniform and well-defined foam cells, indicative of improved polymerization and structural stability. Lower blowing agent percentages produced smaller and denser cells, leading to a more compact and mechanically robust structure. Conversely, higher blowing agent percentages resulted in larger and more irregularly shaped cells, reflecting increased foam expansion and reduced density. Compression strength testing showed a significant decrease in foam strength from approximately 0.6 MPa to 0.1 MPa as the blowing agent percentage increased from 5% to 20%. This reduction indicates that while higher blowing agent content can enhance foam insulation properties by reducing density, it also compromises the foam's mechanical strength. However, longer curing times from 24 to 48 hours were found to significantly improve compression strength across all blowing agent percentages, reaching up to 0.6 MPa, underscoring the importance of adequate curing for achieving enhanced foam stability and strength. Post-compression recovery tests demonstrated that longer curing times significantly improved the foam’s ability to regain its original shape, highlighting the critical role of curing in maintaining foam integrity and performance after deformation. These findings emphasize the necessity of optimizing both blowing agent concentration and curing duration to tailor the foam’s mechanical and structural properties for specific industrial applications, such as in construction and automotive industries, where a balance between lightweight, insulative properties.

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We've used soybean oil to create polyurethane foams without using harmful isocyanates. Polyurethane foams are common in industries like construction and automobiles. In 2023, the global market for these materials was worth about USD 78.07 billion, and it's expected to grow by 4.5% annually from 2024 to 2030. Polyurethanes are used in making flexible foams (39%), rigid foams (26%), coatings (13%), binders (4%), elastomers, and adhesives. Using soybean oil for such a large industry could lead to a demand of around 15 million metric tons of soybean oil each year, which is over 3 billion soybean bushels. Kansas is the 10th largest soybean producer in the US, making soybeans a good source of raw materials for this industry.

Our simple method involves converting soybean oil into carbonated soybean oil (CSBO) using carbon dioxide, a greenhouse gas. We made the non-isocyanate-based polyurethane foams by mixing CSBO with eco-friendly chemicals like baking soda (NaHCO3) in different amounts (1%, 5%, 10%, 15%, and 20%). We tested the foam using various industrial methods and confirmed that it formed properly. As we increased the amount of NaHCO3, the foam's compression strength went up from about 0.1 MPa to 0.6 MPa, meaning that more NaHCO3 results in less dense but weaker foam. We also noticed a decrease in foam density from around 100 kg/m³ to 40 kg/m³ as we added more NaHCO3. This suggests that while more NaHCO3 can make the foam lighter and better for insulation, it also makes it less strong.

When we extended the foam's curing time from 24 hours to 48 hours, its compression strength increased from around 0.3 MPa to 0.6 MPa across all NaHCO3 levels. This shows that longer curing times allow for better polymerization and stabilization of the foam structure, leading to better mechanical properties. Even with different levels of NaHCO3, the foam's strength after 48 hours of curing was significantly higher than after 24 hours, highlighting the importance of curing time in achieving the desired mechanical characteristics.

Analyzing the data reveals that finding the right balance between NaHCO3 concentration and curing time is crucial for customizing the foam's properties for different applications. As curing time increases, the foam cells become more uniform and well-defined, indicating improved polymerization and stability. At lower NaHCO3 levels, the cells are smaller and more compact, creating a denser structure. Higher NaHCO3 levels result in larger, more irregularly shaped cells, which leads to more foam expansion and lower density. The images show that longer curing times improve the foam's structural integrity and uniformity, while higher NaHCO3 levels lead to more noticeable cell formation, affecting the foam's mechanical properties and density.

Polyurethanes are an important class of polymers because of their wide industrial applications in automobiles, construction, household appliances, medicine, packaging, furniture, thermal, and electrical/vibration insulations. There is a global effort to replace petrochemicals with compounds from renewable resources. We propose to use soybean oil for the preparation of polyurethanes using a cost-effective method that can be used for the consumer as well as industrial applications. Polyurethanes are used in the production of flexible foams (39%), rigid foams (26%), coatings (13%), binders (4%), elastomers, and adhesives. The global polyurethane market size was valued at USD 72.82 billion in 2021 and is expected to expand at a compound annual growth rate (CAGR) of 4.3% from 2022 to 2030. Over 24 million metric tons of polyurethane were used globally in 2021. Utilizing soybean oil for such a huge industry will generate a demand of ~ 15 million metric tons of soybean oil (over 3 billion soybean bushels) per year. Kansas ranked 10th in soybean production among US states. Soybeans will provide a good source of raw material for the polyurethane industry. Kansas Polymer Research Center and PIs have experience in commercializing technology and bio-based products. For example, Cargill Inc. is producing a wide range of soybean oil-based products from our technology. PIs have developed a process to fabricate high-performance bio-based batteries and supercapacitors and have filed a patent and working towards commercialization.