Common Additives Used in Coatings

PCI’s online Additives Directory has just launched. The Directory features suppliers and distributors of the multitude of additives used to formulate and manufacture coatings. Below is a selection of some common additives featured in our Directory, along with a few of the suppliers of these products.

Click on the additive type to link to that section in our Directory. And click on the company logos to view those specific listings.

Abrasion Resistance Improvers

Abrasion is a phenomenon caused by the mechanical action of rubbing, scraping or erosion. It has two forms — marring or wearing. Mar abrasion is the permanent deformation of a surface, but the deformation does not break the surface. Wear abrasion is removal of a portion of the surface by some kind of mechanical action: wind erosion, sliding back and forth of an object, wear of tires on traffic paint, etc. The surface removal is gradual and progressive in nature.

Abrasion resistance is a combination of basic factors such as elasticity, hardness, strength (both cohesive, tensile and shear strength), toughness, and, especially in the case of wear resistance, thickness. In addition, abrasion resistance is intimately related to scratching and slip. Thus, compounds that enhance these properties will improve abrasion resistance. (Source: 2013 Additives Handbook, By Dr. Joseph V. Koleske, Robert Springate and Dr. Darlene Brezinski, June 2013 issue, PCI)

Defoamers

Defoamers, deaerators and antifoaming agents are all additives used to prevent, reduce or eliminate foam in a coating, whether in-can, during application or in the final film. While these terms are used interchangeably, they are different. Defoamers are designed to work at the surface to break bubbles already created. Deaerators are designed to work in the bulk liquid to move air bubbles to the surface so defoamers can break them. Antifoaming agents are designed to prevent foam from forming. While an additive is designed to do one, they will all tend to do all three, but with varying efficiency. (Source: Mike Praw, Indorama Ventures: Integrated Oxides and Derivatives)

Defoamers, Non-Silicone

Non-silicon defoamers are designed to be used in systems where the presence of silicone is not allowed, such as in automotive coatings. Non-silicone defoamers have limits on the incompatibility due to the nature of the chemistry. (Source: Mike Praw, Indorama Ventures: Integrated Oxides and Derivatives)

Defoamers, Silicone

These are based on silicone chemistry for higher incompatibility and greater efficiency. The higher the incompatibility of the additive, the greater the defoaming but the higher the chance of surface defects. (Source: Mike Praw, Indorama Ventures: Integrated Oxides and Derivatives)

Flow and Leveling Agents

Flow and leveling agents are chemical compounds that increase a coating’s mobility after application, thus enabling the process of leveling. They reduce the surface tension of the wet coating and, more importantly, maintain a uniform surface tension over the entire surface area. Flow is the resistance to movement by a liquid material. Leveling is a measure of the ability of a coating to flow out after application, so as to obliterate any surface irregularities such as brush marks, orange peel, or craters. (Source: 2013 Additives Handbook, By Dr. Joseph V. Koleske, Robert Springate and Dr. Darlene Brezinski, June 2013 issue, PCI)

Surface Modifiers

A surface modifier is an additive intended to modify a particular surface property. Typical functions of surface modifiers are to:

• reduce the effect of friction/surface tension of the film;

• improve abrasion resistance;

• alter a coating’s “feel”;

• modify surface appearance; and

• enhance other performance properties.

(Source: 2013 Additives Handbook, By Dr. Joseph V. Koleske, Robert Springate and Dr. Darlene Brezinski, June 2013 issue, PCI)

Surfactants and Dispersing Agents

Surfactants encompass a variety of compounds that are used in various ways. The term ‘surfactant’ is derived from ‘surface-active agents,’ and as the name implies, the compounds are used to alter surface phenomena. These chemicals will reduce surface tension and improve wetting and spreading (wetting agents); aid in dispersion of pigments in formulated products (dispersants); inhibit foam formation (defoamers) although others will stabilize foams; and cause or improve emulsion formation (emulsifiers).

A dispersant is an additive that increases the stability of a suspension of powders (pigments) in a liquid medium. The pigment dispersing step is the most difficult and time/energy-consuming part of the paint manufacturing process. This is because of the difference in surface tension between the liquids (polymers and solvents) and the solids (pigments and extenders). When changing pigmentation in a formula, the dispersant needs to be checked quite carefully to see if it is stable in the formulation. Good dispersion provides the end user with better hiding and color stability. (Source: 2013 Additives Handbook, By Dr. Joseph V. Koleske, Robert Springate and Dr. Darlene Brezinski, June 2013 issue, PCI)

Thickening Agents and Rheology Modifiers

A material used to thicken (increase the viscosity of) a liquid. Thickening agents provide the proper consistency to coatings, aid in applying an adequate thickness of coating to a substrate, and inhibit phase separation and prevent pigment settling. Basically, thickening agents increase the viscosity at moderate shear rates and thereby increase the coating’s resistance to flow during mixing, pouring and stirring. They are important to all phases of the manufacturing process, storage and application.

Rheology modifiers are chemicals that alter the deformation and flow characteristics of matter when it is under the influence of stress. A basic understanding of coatings rheology is essential to the development of acceptable flow properties in a coating. In coatings formulations and manufacturing, rheological additives control rheology.

The rheology (viscosity as a function of applied shear) of a coating determines many of the properties such as in-can appearance, anti-settling of pigments, color stability, application performance (including sag and spatter resistance), brush or roller loading, brush drag, film build, and flow and leveling. (Source: 2013 Additives Handbook, By Dr. Joseph V. Koleske, Robert Springate and Dr. Darlene Brezinski, June 2013 issue, PCI)

Waxes

The term "wax" encompasses a large range of naturally occurring and synthetic material made from high-fatty-acid esters (typically C36 – C50) or from polymeric compounds (700 < molecular weight < 10,000) that differ from fats in being harder and less greasy. It is, however, important to realize that the chemical composition alone does not determine a wax. The term wax is basically a generic term for materials that have the following physical characteristics:

• solid at 20 °C, varying in consistency from soft and plastic to brittle and hard;

• a melting point of at least 40 °C without decomposing, which distinguishes waxes from oils and natural resins; and

• a relatively low viscosity at temperature slightly above the melting point; non-stringing but producing droplets. Droplet formation will exclude most low-molecular-weight polymers.

(Source: 2013 Additives Handbook, By Dr. Joseph V. Koleske, Robert Springate and Dr. Darlene Brezinski, June 2013 issue, PCI)