To understand what coating additives are, we must first learn about additives. What are they? Why are they so vital to our economy? Can we function without them?
Additives are used in many industries like plastics, rubber, and paint to give products distinct and necessary qualities and improvements that would be absent without them.
In the paint industry, which we’ll discuss in depth in this article, additives or coating auxiliary materials impact the appearance, flow, and color.
Coating Additives And Their Types
Coatings like paint use a complex mix of substances like solvent, pigments, resin, and additives like dispersants, performance enhancers, rheology modifiers, silicone, and thickeners to render them usable, effective, and dynamic.
Additives improve the inherent resin properties so that the final product is appealing from its formulation to the final storage. However, they only form a small component of the entire blend.
Flow And Leveling Agents
Flow and leveling agents reduce or eliminate surface defects like craters, orange peel texture, overspray, and fisheyes.
They also diminish surface tension due to pretreatment problems or contaminants by enhancing substrate wetting and degassing, and balancing adhesion and cohesion. This results in a smooth and glossy surface without brush and roller marks.
They spread the paint evenly for a uniform layer.
Polyacrylates work as flow and leveling agents due to their flow performance. However, they alone may not reduce surface tension significantly to improve substrate wetting or remove cratering.
When fluorinated side chains are added, they reduce surface tension and provide excellent flow and leveling, good wetting, and strong anti-cratering abilities.
Silicone-based leveling agents are also great additives in this category that:
- Provide good flow
- Reduce surface tension
- Increase surface slip
- Avoid silking and air draft sensitivity
- Reduce orange peel
- Decrease turbulence and rheological currents due to solvent evaporation
- Improve scratch and mar resistance.
Rheology Modifiers
These crucial thickeners are extensively used to give rheological characteristics to coatings. They help achieve the desired viscosity, extend paint shelf stability, and produce easier applications by controlling flow behavior.
But What Is Rheology?
Rheology in paints and coatings examines how easily paint spreads during application, whether paint drips, sags, or levels properly, and how it behaves under different conditions such as brushing, rolling, and spraying. So the most crucial aspect to consider here is viscosity.
It influences traits like vertical flow and leveling, adhesion, covering power, film thickness, brush and roll resistance, pigmentation stabilization, gloss, spattering, and sedimentation.
Two Types Of Rheology Modifiers
Inorganic modifiers include clay and silicas, while organic agents are cellulose, xanthan gum, and polyacrylates. These can further be divided into waterborne and solventborne system thickeners.
Most organic modifiers are surface-active and exhibit properties like improved flow, gloss, and appearance.
Dispersants
Dispersing agents evenly distribute solid particles, such as pigments and fillers, in paint and prevent them from clumping or settling. They improve color strength, stability, and overall paint performance. Proper dispersion ensures consistent color, gloss, and opacity. The amount used depends on pigment loading but typically ranges from 0.5-3% of the formulation.
Before we discuss dispersants in detail, understand that they’re different from wetting agents. While both improve pigment distribution, wetting agents focus more on pigment wetting in the paint mix. Both are often used together for optimal performance.
Dispersants consist of two parts: anchoring groups and soluble tails.
Examples include sodium polyacrylate, sodium hexametaphosphate, and polymeric dispersants.
Surfactants And Wetting Agents
Surfactants reduce surface tension between the liquid paint and surfaces. They improve paint flow, substrate wetting, and pigment dispersion.
Common surfactants include alkylphenol ethoxylates, acetylenic diols, and silicone-based agents. These additives are crucial for preventing defects like cratering and ensuring smooth application.
Defoamers
Defoaming agents eliminate foam created during paint manufacturing and application. They include mineral oils, silicones, and fatty acid derivatives that disrupt the stability of foam bubbles.
Effective defoamers must be insoluble in the paint system but have enough surface activity to spread throughout the foam. They’re used at 0.1-0.5% concentrations, as excessive amounts can cause surface defects.
Biocides
Biocides prevent bacterial and fungal growth in water-based paints during storage with in-can preservatives and after application with film preservatives.
Common in-can preservatives include isothiazolinones like MIT, BIT, and CIT, bronopol, and formaldehyde donors. Film preservatives often contain zinc pyrithione, OIT, and IPBC.
Driers Or Solvent-Based Paints
Driers catalyze oxidative crosslinking in alkyd and oil-based paints. Primary driers like cobalt, manganese, and iron compounds facilitate oxygen uptake, while secondary driers like calcium and zirconium compounds promote thorough drying.
Modern formulations increasingly use less toxic alternatives to cobalt.
Freeze-Thaw Stabilizers
These prevent water-based paints from destabilizing during freezing cycles. Glycols such as propylene glycol and ethylene glycol, and glycol ethers lower the freezing point of the aqueous phase.
UV Stabilizers And Absorbers
These protect paint films from UV degradation, preventing color fading and film breakdown. Hindered amine light stabilizers or HALS scavenge free radicals while benzotriazoles and benzophenones absorb UV radiation.
Anti-Skinning Agents
Used in solvent-based systems to prevent skin formation during storage. Oximes like methyl ethyl ketoxime, butyraldoxime, and phenolic antioxidants inhibit surface drying.
Flash Rust Inhibitors
These prevent instantaneous rusting when water-based paints are applied to ferrous metals. Sodium nitrite, amino carboxylates, and phosphate esters form protective films on metal surfaces.
Adhesion Promoters
These improve bonding to difficult substrates. Silanes, titanates, and functionalized polymers create chemical bridges between paint and substrate.
They’re particularly important for coatings on plastics, metals, and previously painted surfaces.
Matting Agents
These reduce gloss levels in paint films. Silica in precipitated, fumed, or gel types, waxes, and some clays creates microscopic surface irregularities that scatter light.
Their Importance
Ideal additives reduce expenses and improve industrial goals. In paints, for instance, they boost traits like leveling, flow, appearance, durability, drying capabilities, and mildew resistance. Here are some amazing benefits of paint additives that add to their importance.
Critical Performance Enhancers
Most people don’t realize that the tiny fraction of additives in paint completely transforms how it performs. I’ve seen paints with excellent resins and pigments fail miserably without the right additives.
They’re like the secret sauce that turns basic ingredients into something that actually works in the real world – standing up to weather, applying smoothly, and looking good for years.
Application and Workability
Have you ever tried using paint without decent surfactants or rheology modifiers? It’s a nightmare. The paint streaks, sags, and you end up with terrible coverage. I remember a project where we tried to save money by skimping on these additives – complete disaster.
The paint was impossible to work with. Those bubbles that form without defoamers? They don’t just look bad, they create weak spots in the protective film.
These additives are what make paint actually usable, whether you’re a contractor with a spray gun or a homeowner with a roller.
Durability and Longevity
I’ve seen houses in Florida where one side had paint with good UV stabilizers and the other didn’t. After just two years, the difference was shocking – the unprotected side was chalky, faded, and starting to peel.
Those UV additives essentially double or triple the life of exterior paint. And don’t get me started on biocides – especially in humid areas, without them, you’ll have mildew and algae growing on your walls within months.
The flash rust inhibitors and adhesion promoters are what keep paint from failing prematurely when exposed to moisture and temperature swings.
Storage Stability
It’s easy to take for granted that you can open a can of paint that’s been sitting on a shelf for years and it still works. That’s entirely because of additives. Before modern preservatives and stabilizers, paint had a shelf life measured in weeks or months, not years.
My grandfather, who worked in a paint store, told me stories about the constant problems with paint spoiling, skinning over, or freezing solid. These additives have completely transformed the economics of paint manufacturing and retail.
Environmental and Regulatory Compliance
When the regulations on VOCs started tightening up, it was additives that saved the day. Everyone thought water-based paints would never perform like the old solvent stuff.
But clever additive combinations made it possible to get the same results with much lower environmental impact. I’ve watched this evolution personally – the early low-VOC paints were terrible, but now they often outperform the old formulations, all thanks to advanced additives.
Health and Safety
Remember when people would have to leave their homes for days after painting because of the fumes? Modern additives have changed all that. My sister has severe asthma and used to react badly to freshly painted rooms.
Now with low-emission additives, she can be in the house the same day. And the improvements in biocide technology mean we’re not exposing ourselves to the highly toxic preservatives that were once common in paint.
Economic Impact
The funny thing about additives is they often cost more per pound than the base paint materials, but they create so much value. They’re what lets paint companies charge premium prices for special features like stain resistance or one-coat coverage.
I’ve calculated that good additives can actually reduce the overall cost of a painting job by improving coverage and durability, even though they make the paint itself more expensive per gallon.
Customization and Innovation
Every cool new paint innovation I’ve seen in the last 20 years has been made possible by additives. Self-cleaning paints, heat-reflective coatings, paints that reduce airborne pollutants – none of this would exist without specialized additives.
The base paint technology hasn’t changed that much, but the additives keep evolving and creating new possibilities. It’s where all the excitement in paint chemistry happens.
Manufacturing Efficiency
Having worked in a paint factory, I can tell you that good additives make manufacturing so much easier. With the right dispersants, you can incorporate pigments in half the time with less energy.
Proper defoamers prevent production delays and quality issues. The best additive packages simplify the whole production process, saving time and money while actually improving the final product.
