General Overview
Definition: An orange opaque pigment is a colored substance used to impart a bright, non-transparent orange color to paints, coatings, inks, plastics, and other materials. Its opacity means it effectively blocks light, preventing any underlying surface from showing through.
Composition
Chemical Nature: Orange opaque pigments can be organic or inorganic.
Inorganic examples:
Cadmium orange (Cadmium sulfoselenide): Bright and durable but toxic.
Iron oxide orange: Earthy, less vibrant but non-toxic and widely used.
Chromium-based pigments: Less common due to toxicity concerns.
Organic examples:
Azo pigments: Bright, vivid orange, good lightfastness.
Properties
Opacity: High opacity due to particle size and refractive index, which scatters and absorbs light.
Lightfastness: Varies depending on pigment type; inorganic generally more lightfast than organic.
Heat stability: Inorganic pigments typically have good heat resistance.
Toxicity: Depends on chemical composition (cadmium pigments are toxic; iron oxides are safer).
Particle size: Typically micron-sized to maximize opacity.
Chemical stability: Resistant to acids, alkalis, and solvents, particularly inorganic types.
Applications
Used in:
Paints and coatings (architectural, automotive, industrial)
Printing inks
Plastic coloration
Artist’s paints
Cosmetics (only non-toxic types)
Advantages
Provides bright, vivid color with excellent hiding power.
Durable and resistant to environmental factors.
Widely available in various formulations.
Disadvantages
Some pigments (like cadmium orange) are toxic and regulated.
Organic pigments may have lower heat resistance and lightfastness.
Some pigments may be more expensive due to rarity or synthesis complexity.