By Nihal Pandrapragada
Simply defined, additives are specialty chemicals used to enhance the performance of sealcoatings. By analogy, additives are the “flavors and spices” of a sealer. These products are specifically designed by material suppliers to boost performance in sealers based on refined tar, asphalt, and petroleum-based resins.
Today, sealcoating professionals are very familiar with these additives. Their use allows contractors to apply sealcoatings even under less-than-ideal conditions—achieving not only optimal performance, but often exceeding it. Through this article, we aim to provide detailed information about these additives and offer guidance on selecting and using the right products.
Sealcoating additives have been in use since the 1960s. Additives based on specialty latex and rubber polymers have been part of FAA specifications since the early 1970s. Since then, the technology has advanced significantly, offering improved efficiency and performance.
In terms of how additives work, polymer particles fuse with resin particles in the sealcoating as it dries, tightening the network within the film. This improves the overall performance of the cured film and produces a more uniform dry color. Conversely, any weakness in the polymer (additive) can introduce weak links in the sealer and lead to premature failure.
Types of Additives
Depending on job requirements and desired results, the right additive—or combination of additives—should be selected. Based on performance outcomes, additives can be categorized as follows:
1. Performance Boosting
Sealcoatings modified with properly selected additives show improved:
• Resistance to chemicals, deicing salts, oil, jet fuel, etc.
• Resistance to water and weather elements (UV exposure, etc.)
• Toughness, flexibility, and elongation
• Thermal stability
2. Fast-Drying Additives
These additives accelerate drying time—even under less-than-ideal weather conditions—reducing labor costs and allowing surfaces to reopen to traffic sooner.
3. Low-Temperature Curing Additives
Specifically designed to enable proper curing and drying at lower temperatures (such as the low 40s°F). These should not be confused with fast-drying additives.
4. Adhesion-Promoting Additives
Designed to improve bonding on challenging surfaces, such as those with smooth or polished aggregates.
5. Uniform Dry Color Additives
Help ensure consistent drying across sun and shade conditions, resulting in a uniform finished appearance.
6. Thickening Additives
Used to suspend larger amounts of sand or compensate for over-diluted sealer mixes. While effective for viscosity, they contribute little to performance and can introduce permanent water sensitivity. Use with caution.
Types Based on Composition
Most additives are manufactured using polymers and specialty chemicals and are typically formulated as water-dispersible products. The type of polymer or chemical used determines the additive’s performance characteristics.
Based on composition, additives can be categorized as follows:
1. Acrylonitrile Butadiene Rubber (NBR) Additives
Widely used for rubberizing refined tar, asphalt, and petroleum-based sealcoatings, improving flexibility and toughness. They also offer excellent resistance to chemicals, oils, greases, hydraulic fluids, and kerosene.
2. Acrylic Polymer and Copolymer Additives
Commonly used for thickening, sand/aggregate suspension, and faster drying.
3. Styrene Butadiene, Natural Rubber, and Butyl Rubber Additives
Used for thickening, aggregate suspension, faster drying, and improved chemical resistance. These polymers offer strong resistance to water, moderate chemicals, alcohols, and organic acids.
4. Polyvinyl Acetate/Acrylic Copolymer Additives
Often used for thickening and drying performance. However, they typically have poor resistance to water, UV exposure, salts, fuels, and oils, which limits their effectiveness as overall performance enhancers.
5. Alcohol-Based Additives
Designed to enhance drying properties, allowing sealcoatings to cure more effectively in cooler conditions. These improve color, durability, and performance but do not affect viscosity.
Cautions
• Additives must always be selected and used according to the manufacturer’s recommendations. A common misconception is that additives can be used universally across all sealcoatings—this is not the case. Most are formulated for specific sealer types and may be incompatible with others, potentially degrading performance. Always consult the manufacturer for compatibility and usage guidance.
• Additives will not compensate for poor mix design, such as substandard sealer, excessive water, or improper aggregate ratios. Always follow supplier recommendations.
• Do not mix additives from different manufacturers within the same sealcoating system. Even if they serve similar functions, their chemical compositions may differ and can negatively impact performance or void warranties.
• Follow recommended dosage levels carefully. Too little additive may yield no benefit, while too much can waste money or even degrade performance. For example, excessive thickener can make the sealer too viscous to mix or apply.
Final Thoughts
Although used in small quantities, additives can be a powerful tool—often making the difference between a good job and a great one. For contractors, this can lead to increased customer satisfaction and business growth. For property owners, it can mean longer-lasting pavement and reduced maintenance costs.
It’s a win-win for everyone.
Nihal Pandrapragada is a Technical Manager and Research & Development Chemist with STAR SEAL, Inc.