The right process oils can improve the flexibility, strength, appearance, and manufacturing efficiency of adhesives and sealants. Learn how oil selection affects performance and what manufacturers should consider when choosing a specialty oil. Questions? Contact us.
Adhesives and sealants are used in everything from packaging and automotive parts to construction materials and consumer products. Manufacturers need these products to apply smoothly, form reliable bonds or seals, and maintain their performance over time.
While polymers and resins often get the most attention, process oils also play an important role in many formulations.
The right oil can improve processing and help achieve specific product characteristics. The wrong one can contribute to poor adhesion, discoloration, oil migration, and other quality problems.
Let’s look at how process oils influence adhesive and sealant performance and what manufacturers should know when selecting them.
Suzanne Kingsbury, Director of Quality
What Do Process Oils Do in Adhesives and Sealants?
Process oils serve several purposes in adhesive and sealant manufacturing. Depending on the formulation, they may act as plasticizers, extenders, or blending aids.
As plasticizers, they help soften polymers and make compounds easier to process. As extenders, they can reduce formulation costs while maintaining the properties required for the finished product.
Process oils are especially important in certain hot-melt adhesives, pressure-sensitive adhesives, rubber-based sealants, and thermoplastic elastomer (TPE) formulations.
However, not every adhesive or sealant uses mineral oil. Its suitability depends on the polymer system, the manufacturing process, and the finished product’s requirements.
Research: Process Oils in Hot-Melt Adhesives
A technical review published in MRS Bulletin in 2011—still relevant today—explains how process oils and tackifying resins influence the performance of hot-melt adhesives. These ingredients can reduce viscosity and improve wet-out, or how effectively an adhesive spreads across and makes contact with a surface. They also affect the temperature at which polymers transition between rigid and flexible states. However, manufacturers must balance these benefits with the need for sufficient strength and heat resistance in the finished adhesive.
How Process Oils Affect Adhesive and Sealant Performance
1. Process Oils Improve Viscosity and Application
Viscosity describes how easily a liquid flows. It is especially important in hot-melt adhesives, which must flow during application and then develop sufficient strength as they cool.
Process oils can reduce the viscosity of an adhesive formulation, helping it flow through manufacturing equipment and spread across the surfaces being bonded.
Potential benefits include:
- Easier mixing and more consistent blending of ingredients
- Improved flow through pumps, nozzles, and coating equipment
- Better coverage of bonding surfaces
- More consistent application and product quality
However, reducing viscosity too much can create problems.
An adhesive that flows easily may not have enough internal strength to hold materials together under stress. Manufacturers must balance processing requirements with the performance expected from the finished adhesive.
As the Cambridge University Press study explains, formulators must balance viscosity and surface contact with adequate strength and heat resistance.
2. Process Oils Influence Tack, Adhesion, and Bond Strength
Adhesives must achieve the right balance between sticking to a surface and holding that bond over time.
Three properties are especially important:
- Tack: How quickly an adhesive sticks to a surface when pressure is applied.
- Peel adhesion: How much force is needed to pull an adhesive away from a surface.
- Cohesive strength: How well the adhesive holds together internally when placed under stress.
Process oils can influence all three.
In a study published through the Pressure Sensitive Tape Council, researchers from Eastman Chemical Company and Petro-Canada Lubricants tested 13 different base oils in pressure-sensitive adhesives.
They found that oil viscosity and chemical composition influenced several measures of adhesive performance. In the formulations tested, oil viscosity was particularly important in determining adhesive properties.
The findings show why simply matching the viscosity of two oils does not always make them interchangeable. Chemical composition can also affect how an oil interacts with the other ingredients.
For manufacturers, the goal is not necessarily to maximize tack or bond strength. It is to achieve the right balance for the intended application.
A packaging tape, for example, may need strong initial adhesion, while a removable label must release cleanly without damaging the surface.
3. Process Oils Help Control Flexibility and Elasticity
Sealants often need to accommodate movement without cracking or losing contact with the surfaces they protect.
Consider a construction joint between two building materials. As temperatures change, those materials may expand and contract at different rates.
A sealant that is too rigid may crack or pull away from the joint. A properly formulated sealant can stretch and recover as the joint moves.
Compatible process oils can help adjust the softness and flexibility of rubber-based and TPE sealants.
This can be especially valuable in:
- Construction joint sealants
- Automotive sealing compounds
- Rubber-based mastics
- Flexible waterproofing materials
- Polymer-modified asphalt products
Process oils can also influence low-temperature flexibility. Depending on the formulation, the right oil may help a compound remain flexible when temperatures fall.
But adding more oil is not always better. Excessive plasticization can reduce strength, while poor compatibility may allow the oil to migrate out of the material.
The importance of maintaining adhesion and flexibility is reflected in ASTM C719, a standard test method used to evaluate how elastomeric joint sealants perform under repeated movement, temperature changes, and water exposure.
4. Process Oils Affect Color Stability and Appearance
For manufacturers of clear, white, or light-colored adhesives, appearance is a critical quality requirement.
A hot-melt adhesive that gradually turns yellow may still function as intended, but the discoloration can make customers question its quality.
One possible contributor is the extender oil used in the formulation.
Certain compounds in less-refined oils can react with oxygen, heat, or light, contributing to gradual color changes. More highly refined oils with low levels of reactive compounds offer better color stability.
We’ve helped a manufacturer address this exact problem.
Adhesive Extender Oil Case Study
In this case study, a customer was experiencing yellowing in a clear hot-melt adhesive. We evaluated oil options using ultraviolet (UV) absorption testing, which can help indicate the presence of aromatic compounds. The customer ultimately switched to a higher-quality American Petroleum Institute (API) Group II process oil with low UV absorption. After testing the new oil in its formulation, the manufacturer confirmed an improvement in color stability.
This example demonstrates how selecting a different process oil can help solve a product-quality problem without requiring a complete reformulation.
5. Process Oils Influence Long-Term Stability and Durability
An adhesive or sealant must do more than perform well immediately after manufacturing. It must maintain its required properties during storage and use.
Two important considerations are volatility and oil migration.
- Volatility refers to an oil’s tendency to evaporate. Excessive evaporation during processing or service can change the composition of the finished material and affect its performance.
- Oil migration occurs when oil moves out of the polymer system. It can cause surface oiliness, staining, or changes in flexibility and strength.
Research published in Adhesives & Sealants Industry demonstrates how the chemical characteristics of process oils affect their compatibility with adhesive polymers. Researchers found that different types of mineral oils produced measurable differences in adhesive performance, even when used at relatively low concentrations.
Oil migration is especially important for construction sealants that come into contact with porous materials such as stone or concrete.
For example, ASTM C1248 provides a test method for evaluating the potential for joint sealants to stain porous surfaces because of materials migrating out of the sealant.
Choosing an oil with suitable compatibility, viscosity, and volatility can help manufacturers manage these risks. Extender oils that evaporate in service due to high volatility will result in a shrinking sealant that can pull away and stop performing. This is a catastrophic failure for sealants, which the right oil can prevent.
Choosing Between Paraffinic and Naphthenic Process Oils
One of the most important decisions manufacturers face is selecting the right type of process oil.
Two common options are paraffinic and naphthenic oils. Each has characteristics that may benefit different adhesive and sealant formulations.
Paraffinic Process Oils
Highly refined paraffinic process oils are valued for their stability and compatibility with many nonpolar polymers.
Depending on the grade, benefits may include:
- Excellent initial color and color stability
- Low volatility
- Good resistance to oxidation
- Compatibility with certain rubber and polymer systems
For example, our Chevron ParaLux premium process oils offer color stability, low volatility, and compatibility with rubber and TPE polymers that require paraffinic oils.
They are used in a variety of applications, including adhesives, sealants, and coatings.
Naphthenic Process Oils
Naphthenic oils generally provide greater solvency than paraffinic oils.
Solvency describes how effectively an oil dissolves or mixes with other materials. In adhesive manufacturing, this can affect how well the oil works with polymers and tackifying resins.
Greater solvency can be valuable in certain hot-melt adhesives and other formulations that require a closer match between the oil and polymer system.
In fact, research conducted by Nynas and published in Adhesives & Sealants Industry found that highly refined naphthenic oils improved certain adhesion and surface-contact properties in styrenic block copolymer pressure-sensitive adhesives while maintaining cohesive strength.
However, manufacturers may also need to consider lower color stability, potentially higher volatility, and other characteristics.
To help meet this need, we developed Renoil 500-X.
This highly refined naphthenic process oil combines:
- Higher solvency than conventional paraffinic process oils
- Light color and improved color stability compared with typical naphthenic oils
- An additional sourcing option for manufacturers that need these properties
The right choice depends on the formulation. Neither paraffinic nor naphthenic oil is universally better for adhesives and sealants.
What Should Manufacturers Look for in Process Oils?
Selecting process oils should involve more than comparing product prices or viscosity specifications.
Manufacturers should evaluate how candidate oils affect the complete formulation under actual production and end-use conditions.
Important questions include:
- Is the oil compatible with our polymers and resins? Poor compatibility can lead to separation, migration, or inconsistent performance.
- Does it provide the right viscosity? The oil must support efficient processing without compromising the finished product.
- How will it affect adhesion and flexibility? Test the properties that matter most for the product’s intended application.
- Will it maintain its appearance over time? Color, odor, and oxidation stability may be particularly important in consumer-facing applications.
- Does it meet our volatility and durability requirements? Evaluate performance under expected storage, temperature, and environmental conditions.
- Can the supplier deliver consistent quality and reliable inventory? Even a well-qualified oil creates manufacturing risks if its quality varies or shipments are delayed.
Whenever possible, manufacturers should test potential replacement oils in their existing formulations before making a change.
Even oils with similar published specifications can produce different results when blended with polymers, resins, and other additives.
Renkert Oil: Your Partner for Process Oils in Adhesives and Sealants
The performance of an adhesive or sealant depends on the interaction of all its ingredients. Process oils may be only one part of the formulation, but choosing the right one can make a significant difference.
At Renkert Oil, we help manufacturers find specialty oils that meet their processing, performance, and quality requirements.
Our portfolio includes paraffinic and naphthenic options, including Chevron ParaLux process oils and our Renoil products.
We also understand the importance of supply security. With strategically located inventory, flexible transportation options, and decades of logistics experience, we help customers maintain reliable access to the oils they need.
Whether you’re developing a new adhesive, optimizing an existing sealant, or troubleshooting a quality issue, we can help you evaluate your options.
Looking for process oils that support better adhesive and sealant performance? Contact Renkert Oil to discuss your application, request samples, or learn more about our specialty oil products.
FAQs: Process Oils for Adhesives and Sealants
- What Are Process Oils Used for in Adhesives and Sealants?
Process oils are used as plasticizers, extenders, and blending aids in many adhesive and sealant formulations. They help manufacturers control viscosity, flexibility, tack, and other properties. The right process oil can also improve manufacturing efficiency and support consistent product quality.
- How Do Process Oils Affect Adhesive Strength?
Process oils influence tack, peel adhesion, and cohesive strength. They can help an adhesive spread across a surface and form a bond, but excessive oil or poor compatibility can weaken the finished product. Manufacturers must balance adhesion with the internal strength required for the application.
- What Is the Difference Between Paraffinic and Naphthenic Process Oils?
Paraffinic process oils are often selected for their color stability, oxidation resistance, and compatibility with certain polymers. Naphthenic process oils generally provide greater solvency, which can improve compatibility with some polymers and resins. Neither type is universally better. The choice depends on the formulation and its performance requirements.
- Can Process Oils Improve the Flexibility of Sealants?
Yes. Compatible process oils can soften certain polymer systems, helping sealants stretch and accommodate movement. This is particularly useful in construction joints, automotive sealing compounds, and other flexible applications. However, too much oil can reduce strength or contribute to migration.
- Why Do Some Hot-Melt Adhesives Turn Yellow?
Yellowing can result from oxidation, heat exposure, ultraviolet light, or reactions involving formulation ingredients. Certain compounds in less-refined process oils may contribute to discoloration. Switching to a highly refined oil with better color stability may help. Renkert Oil has helped manufacturers address this problem by selecting more suitable extender oils.
- How Do Process Oils Affect Adhesive Viscosity?
Process oils can reduce the viscosity of certain adhesive formulations, making them easier to mix, pump, and apply. Lower viscosity can improve flow and surface coverage, especially in hot-melt adhesives. However, excessive viscosity reduction may compromise cohesive strength or other performance characteristics.
- What Causes Oil Migration in Adhesives and Sealants?
Oil migration occurs when oil moves out of the polymer system and reaches the surface or surrounding materials. Causes may include poor compatibility, excessive oil loading, or changes in temperature and other service conditions. Migration can lead to staining, surface oiliness, or changes in product performance.
- Are Highly Refined Process Oils Better for Clear Adhesives?
Highly refined process oils can offer advantages for clear and light-colored adhesives, particularly when appearance and color stability are important. Oils with low levels of reactive compounds may be less likely to contribute to discoloration. However, manufacturers must also evaluate compatibility, viscosity, and adhesion before selecting an oil.
- Can Manufacturers Substitute One Process Oil for Another?
Yes, but substitutions should be tested carefully. Two process oils with similar viscosities may differ in chemical composition, solvency, volatility, or compatibility with polymers. These differences can affect adhesive strength, flexibility, appearance, and long-term performance. Laboratory and production trials are recommended before changing oils.
- How Can Renkert Oil Help Adhesive and Sealant Manufacturers?
Renkert Oil supplies paraffinic and naphthenic process oils for adhesive and sealant applications, including Chevron ParaLux and Renoil products with detailed properties reported. We help manufacturers evaluate oil options based on compatibility, viscosity, color stability, and other requirements. Our nationwide inventory and transportation capabilities also help customers maintain a reliable supply.