Os pigmentos são tóxicos?

Olá a todos! Sou uma funcionária estrela da CHROMÉCLAIR, uma marca de esmalte em gel sem hema.Here are some questions and answers about pigments that I’ve compiled. I hope this helps you.

Are pigments toxic? Generally speaking, the environmental friendliness of pigments is relative. It is evaluated based on different industry standards to determine compliance with environmental requirements. Typically, pigments are considered environmentally friendly if their harmful components—that is, their toxicity—are restricted within certain limits (meeting a specific standard), thereby posing no threat to human health or causing environmental pollution.

Below are the toxicity evaluation criteria for inorganic/organic pigments.

• Pigments are primarily classified as organic or inorganic based on their chemical composition, and their toxicity differs accordingly. The criteria for determining whether a pigment is environmentally friendly also vary.
• For inorganic pigments, the primary toxicity evaluation indicators are eight heavy metals: antimony, arsenic, barium, cadmium, chromium, lead, mercury, and selenium.

Multiple standards exist. For instance, pigments used in electronics typically follow the EU RoHS standard, while those in coatings and plastics generally adhere to the EU EN71-3 standard. For industries involving direct food contact, such as non-stick cookware coatings, the U.S. FDA standard is applied for evaluation.

There are two evaluation methods:

One involves testing the heavy metal content of the pigment itself, while the other assesses the leaching of heavy metals after the pigment is incorporated into a product.

Research on the toxicity of organic pigments spans multiple fields, primarily encompassing the following aspects: acute toxicity, skin and mucous membrane irritation, subacute toxicity from repeated exposure, allergenicity, mutagenicity, chronic toxicity, and carcinogenicity.

Since pigments are primarily categorized as organic or inorganic, the key toxicity evaluation metric for inorganic pigments is the content of eight major heavy metals. For organic pigments, toxicity is assessed through acute toxicity, skin and mucous membrane irritation, subacute toxicity from repeated exposure, sensitization, mutagenicity, chronic toxicity, and carcinogenicity.

What Are Pigments？

Adding pigments to coatings provides rust prevention, coloring, and hiding power. Pigments reduce the permeability of the coating film, protect it from UV rays and weathering, and enhance its mechanical properties. Carefully formulated coatings can also exhibit self-cleaning and anti-chalking properties. Beyond delivering the desired gloss and color for topcoats, pigments can control gloss levels, as particles of varying sizes significantly influence light reflection. Increasing pigment particle size can also improve adhesion to existing coatings.

Common Types of Pigments

Based on chemical structure, pigments can be classified into inorganic and organic pigments; by function, they can be categorized as coloring pigments, rust-proofing pigments, and extender pigments; and by origin, they fall into natural and synthetic categories. Natural pigments are primarily derived from natural minerals, such as cinnabar and malachite. Synthetic pigments are predominantly inorganic or organic chemical compounds, such as iron oxide red, chrome yellow, and toluidine red.

Organic Pigments

Organic pigments possess vibrant colors and vivid hues, but they fall short of inorganic pigments in many properties. For instance, inorganic pigments exhibit greater stability under light exposure and atmospheric conditions, and they can form coating films that protect metals from corrosion.

Hundreds of pigment varieties exist, with properties varying by manufacturer, production method, and numerous other factors. Although hazards to humans differ among pigments, all should be considered harmful. Appropriate safety measures must be taken to prevent ingestion or inhalation. For instance, when mixing zinc powder into inorganic zinc-rich coatings, wear a suitable respirator.

Pigment Shape

Pigment shape is a critical characteristic that influences the physical properties of coatings. Common shapes include:

Spherical Pigments

In practice, spherical pigments are the most widely used. These pigments are block-shaped. They are typically color-adding pigments (e.g., titanium dioxide) or sacrificial pigments (e.g., metallic zinc).

Needle Pigments

Also known as needle-shaped pigments, such as zinc oxide or glass fibers, which are used to reinforce and strengthen the coating film while providing color. In the past, asbestos fibers were frequently added to coatings to enhance strength (cohesion and some thixotropy). Although no longer used today, asbestos pigments may be encountered during coating repairs or removal of existing coatings.

Flaky Pigments

Examples include mica, aluminum flakes, glass flakes, and micaceous iron oxide. These pigments overlap during paint drying, increasing coating density to prevent moisture penetration. Simultaneously, they effectively reflect ultraviolet rays in topcoats, enhancing the film’s resistance to aging. Flaky pigments are one of the primary pigment components selected for modern heavy-duty anti-corrosion coatings.

Functions of Pigments

The primary functions of pigments are coloring, rust prevention, and filling:

Pigmentos de coloração

Pigments are the most widely used category of colorants in coatings, primarily serving to provide coverage and decoration. Beyond being insoluble in water, oil, and solvents, they must exhibit vivid and attractive colors, possess strong tinting strength and high hiding power, and demonstrate excellent stability against light and heat.

That’s all for today! I hope this article helps you grasp pigment knowledge more easily!

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