What Are Estolides? - STLE 2021

Summary

Dr. Matthew Creek from Biosynthetic Technologies discusses the advancements in biosynthetic base oils, focusing on 'estelides'—polymerized chains of free fatty acids with enhanced hydrolytic stability. He evaluates estelides' performance against petrochemical oils across a wide viscosity range, highlighting their excellent solvency, low volatility, and good oxidative and hydrolytic stability. The script also explores estelides' application in various formulations, including gear oils, hydraulic fluids, and food-grade hydraulic fluids, demonstrating their environmental performance and potential as sustainable alternatives in lubricant formulations.

Takeaways

• 🧪 Ester-based polymers, known as 'estelides', are created by linking free fatty acids through a secondary ester bond, allowing for a range of viscosities by varying the chain length.
• 🌡 Estelides offer improved hydrolytic stability compared to traditional bio-based materials, which often use primary esters that are susceptible to degradation in the presence of water and heat.
• 📊 The viscosity range of estelides can be adjusted from ISO 22 to ISO 680, providing a wide array of applications from hydraulic fluids to gear oils.
• 🔬 Estelides exhibit good solvency, viscosity index, and low volatility, which are crucial for performance in low viscosity applications.
• 💧 Hydrolytic stability tests show that estelides maintain their integrity even when exposed to water, unlike some traditional bio-based oils.
• 🔥 Oxidative stability tests reveal that estelides perform similarly to petrochemical products, withstanding heat and maintaining their properties over time.
• 🤝 Estelides blend well with other base oils, such as PAOs and Group III, enhancing their properties without introducing negative effects.
• 🌱 Environmental performance of estelide-based formulations is high, with biodegradability levels exceeding 60%, meeting eco-friendly standards.
• 🛑 Toxicity tests indicate that estelide-based formulations are non-acutely toxic, which is a requirement for certain environmental applications.
• 💧 Demulsibility tests show that estelide-based fluids separate from water quickly, an important characteristic for hydraulic fluids.
• 🍽 A project sponsored by the United Soybean Board explored the use of high oleic soy oil blended with estelides for H1-approved food-grade hydraulic fluids, demonstrating the versatility of estelides in various applications.

Q & A

What is an ester bond and how does it relate to the formation of ester-based base oils?

An ester bond is a chemical linkage formed between the carboxylic group of one molecule and a hydroxyl group of another. In the context of ester-based base oils, the script describes an 'eslide' as a secondary ester bond across a site of functionality on a free fatty acid with the carboxylic group of another free fatty acid, allowing the polymerization of long chains of free fatty acids to create different viscosity ranges.

Why are secondary ester bonds preferred over primary ester bonds in ester-based base oils?

Secondary ester bonds are preferred due to their better hydrolytic stability. Primary esters are notorious for being unstable in the presence of water and can break down rapidly, especially under heat. Secondary esters, like those in 'eslides', are sterically hindered, providing enhanced resistance to hydrolysis, making them suitable for applications such as marine environments where traditional bio-based products may struggle.

What is the significance of the viscosity index in ester-based base oils?

The viscosity index is a measure of a fluid's resistance to changes in viscosity with temperature. Ester-based base oils with a good viscosity index, as mentioned in the script, maintain their viscosity across a wide temperature range, which is crucial for applications requiring stable performance under varying temperature conditions.

How does the solubility of ester-based base oils affect their performance in formulations?

The solubility of ester-based base oils, as indicated by the aniline point in the script, affects how well additives can be mixed into the base oil. Good solubility ensures that additives are evenly distributed, which is important for achieving desired properties such as lubricity and protection against wear in finished products.

What are some of the challenges traditional bio-based materials face in terms of hydrolytic stability?

Traditional bio-based materials often face challenges with hydrolytic stability due to the presence of primary ester bonds, which can break down in the presence of water, especially when heat is involved. This can lead to a rapid degradation of the material, limiting its application in environments where moisture is present.

How do ester-based base oils compare to petrochemical-derived base oils in terms of oxidative stability?

According to the script, ester-based base oils, specifically 'eslides', show very similar performance to petrochemical-derived base oils like PAOs and bright stocks in terms of oxidative stability. This is demonstrated through the RV pot test, where 'eslides' exhibit a high resistance to oxidation, a desirable trait for long-lasting performance in applications such as hydraulic fluids.

What is the role of the United Soybean Board in the development of ester-based hydraulic fluids?

The United Soybean Board sponsored a project mentioned in the script, which focused on the development of H1-approved, or food-grade, hydraulic fluids using a blend of ester-based base oils and high oleic soy oil. Their involvement supports the use of cost-effective, environmentally friendly, and high-quality base oils for various applications.

What are some of the key environmental performance metrics for ester-based hydraulic fluids?

Key environmental performance metrics for ester-based hydraulic fluids include biodegradability, as measured by the OECD 301B test method, and toxicity, as assessed by the 201, 202, and 203 tests. The script mentions that the formulations tested showed high biodegradability and non-acute toxicity, which are important for meeting environmental regulations and eco-label requirements.

How do ester-based base oils perform in terms of rust and foaming properties?

The script indicates that ester-based base oils, particularly those with 'eslide' technology, perform well in rust and foaming tests. They pass both fresh water and salt water rust tests without issue and demonstrate good demulsibility with no foaming tendencies, which are common challenges for traditional bio-based products.

What is the significance of the pour point in ester-based base oils?

The pour point is the lowest temperature at which a fluid will flow. It is significant for ester-based base oils because a lower pour point indicates that the oil will remain fluid and functional in colder temperatures. The script mentions that blending 'eslides' with other base oils, such as PAOs or group three stocks, can improve the pour point, enhancing the oil's performance in low-temperature applications.

How do different viscosity ranges of ester-based base oils impact their performance in various applications?

Different viscosity ranges of ester-based base oils allow them to be used in a variety of applications, from low-viscosity hydraulic fluids to high-viscosity gear oils. The script discusses how 'eslides' can be tailored to create products with specific viscosities, and how their performance in tests such as the four-ball weld test and RV pot test remains consistent across different viscosity grades.