Paints and Pigments
No description yet. This curated deck is ready for daily study.
Card preview (24)
Dyes and Pigments
• Collectively termed “colourants” • Dyes are soluble • Pigments are insoluble particels dispersed in a matrix • Mainly designed to enhance a product’ss appeal
What are dyes and pigments made of and where are they used?
• Dyes are primarily organic based, used in textiles • Pigments are equally represented by organic and inorganic components, used in paints, inks, plastics, cement, ceramics, glass
What are dyes and pigments classified by?
Colour Index Scheme (CI)
What does the Colour Index Scheme tell you about a colourant?
• Generic name • Its hue • Its CI number • Application methods • Properties • Companies that manufacture it • Trade names • Chemical composition
What are the three colour characteristics?
• Hue • Saturation • Value
Define Hue
Colour that is dependent upon wavelength
Define saturation and other names that mean the same
Purity of colour (Also called intenisty, stength or chroma)
Define value and give the other names for it
How light or dark the colour is (Brightness and luminance)
What effects the value but not the hue of a colour?
Tint and shade
What is tint? In terms of colour
Addition of white
What is shade? In terms of colour
Addition of black
What is colour determined by?
• Light absorption/reflection • Crystal lattice • Particle size/shape
What determines the opacity of pigments?
• Determined by the degree of light scattering • Higher refractive index (RI), higher the opacity, higher coverage
Pigment size How do you get a glossy or matt pigment?
Glossy: Use small particles at low concentrations, finely dispersed in the formulation Matt: Opposite of gloss
What are the benefits of inorganic pigments?
• Resistant to heat • Resistant to light • Resistant to weathering • Resistant to solvents • Resistant to chemicals • Cheaper (mineral derived or metal based are cheapest)
What are the benefits of using organic pigments?
• Better colour intenisty and brightness • Lower RI = lower opacity = more transparent • Need to have translucency to work in harmony to produce the colours on a print out
What does different particle size mean in pigments with examples?
Larger particle size for maximum opacity * TiO2 pigment grade (0.25 μm) Smaller size for sunscreens * Nano TiO2 particles (<0.1 μm)
What are non-hiding white pigments used for, with examples?
Extenders (bulk stuff out) * Calcium carbonate * Talc * China clay * Silica
What are organic pigments sometimes called?
Lakes
Why are paints good for forensic analysis?
Huge variety and complexity so there is good discrimination between samples
What are the main components of paint?
• Binders • Pigments • Fillers • Drying agents • Texturisers • Emulsifiers • Fungicides, biocides, insecticides • UV stabilisers and corrosion inhibitors • Plasticisers
What are binders and give examples?
It is what makes paint, paint like (sticky and brittle) * Polymers * Acrylic
What do pigments do in paint with examples?
Gives paint its colour and opacity * TiO2 * ZnO * BaSO4 * Fe2O3
What are fillers and examples?
Increase the thickness of coatings * Non-hiding white powders * Talc