Pigment Dispersions: Frequently Asked Questions
Pigments are a key component in formulating and tinting coatings and plastics and play a critical role when it comes to performance. Here are the most common questions manufacturers have about pigment dispersions.
What Are Pigment Dispersions?
Pigment dispersions are dry pigments dispersed in liquid material that are stabilized using resins or surfactants/additives to minimize reagglomeration, a phenomenon where the pigments come back together to form “lumps”. They can contain water, solvent, or based on a resin that is liquid at room temperature. Pigment dispersions often have relatively high pigment concentrations and are used in additive quantities to impart color in a wide variety of products. The term “pigment dispersions” is often used synonymously with colorants, color concentrates, and pigment preparations.
What’s the Difference Between Pigment Dispersions and Colorants?
Colorants is a broader term than pigment dispersions, often defining a substance (either liquid or dry) that is added to change the color of a material or surface. They can contain pigment (solid particles) which can be dispersed, stabilized or suspended in a vehicle, such as water, solvent or resin. Colorants can also be dyes where the color component is soluble in the medium.
Why Are Pigments Dispersed?
In their dry state, pigments are rather large agglomerates with a wide range of sizes. By dispersing pigment in a liquid medium, energy is applied to the agglomerates to reduce their overall size to aggregates and narrow the range of aggregate sizes. The reduction and normalization of pigment aggregate size achieves a number of benefits:
- Stabilizes the particles in a homogenous suspension
- Prevents settling of particles in a liquid medium
- Maximizes color efficiency so that lower quantities of costly pigments are used
- Results in predictable and reproducible color
How Are Pigment Dispersions Delivered Into a System?
When in liquid form, dispersions are typically added to another material by either dispensing (volumetrically) or adding by weight (gravimetrically), which can be an automated or manual process. When in a dry form, dispersions are usually added by weight. However, recent advances in pigment dispersion technology allow for pre-dispersed dry pigment dispersions to be dispensed volumetrically.
Which Markets Are Pigment Dispersions Most Commonly Used in?
Manufacturers use pigment dispersions to color many types of materials, such as paint and coatings or plastics. Applications include decorative and industrial applications, thermoset composites, inks, plastics and textiles.
Are Pigment Dispersions Environmentally Friendly?
The environmental impact of dispersions vary. As a whole, the industry is shifting toward products that have a smaller impact on the environment and consumer health. However, not every product fits this description.
A dispersion’s designation as “eco-friendly” is typically tied to the presence (or lack thereof) of a class of compounds called VOCs. Volatile organic compound (VOC) is a broad term that includes compounds that are known to be harmful and ones not traditionally thought of as harmful. A dispersion is environmentally friendly if it contains low levels of VOCs.
More recent trends include the incorporation of sustainable materials, such as resins, into the pigment dispersions where those materials are produced from sustainable sources, such as plants. Also, pigments and pigment dispersions are used to reflect infrared radiation from the sun to lower surface temperatures and energy consumption.
What Traits Are Important to Look for?
Pigment dispersions are not one-size-fits-all when it comes to use in coatings and plastics. The end application should drive the dispersion choice and the factors you look for. Here are the top traits to consider:
- Fineness of grind
- Tinting strength & control
- Ease of use
- Consistency of color in the final application
- Color space
- Color retention
- Chemical resistance