Engineering Materials·MCQ explained

The thinner used in plastic paint is:

Try it first: pick an option, then read the explanation.

Correct answer: B. water
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Water-Based vs. Solvent-Based Paints

"Plastic Paint" is a common term for modern water-based paints, also known as emulsion or latex paints. The "plastic" refers to the binder, which is a synthetic polymer like acrylic or vinyl acetate. The key feature of these paints is that the binder is dispersed in water. This determines the type of thinner used and differentiates them from traditional oil- or solvent-based paints.

Detailed Analysis of the Options

(a) Naptha & (d) Spirit

Type: Volatile Solvents.
Use: These are strong, fast-evaporating organic solvents. They are used to thin specific industrial coatings, lacquers, and spirit-based varnishes. They are not compatible with water-based plastic paints and would cause the paint to curdle and separate.

(b) water

Type: Universal Solvent.
Use: This is the correct answer. Since plastic paints are water-based emulsions, water is the appropriate and only thinner to use. Adding a small amount of water reduces the paint's viscosity, making it easier to apply with a brush or roller. It is also used for cleaning brushes and equipment after use.

(c) oil

Type: Oil-based Thinner.
Use: Linseed oil, mineral turpentine oil (MTO), or other oils are used as thinners for traditional oil-based paints and enamels. Mixing oil with a water-based plastic paint would be like mixing oil and water; they are immiscible and would ruin the paint.

Thinners for Different Paint Types

Paint TypeCommon NamePrimary Thinner
Water-Based EmulsionPlastic Paint, Latex PaintWater
Oil-Based PaintEnamel, Alkyd PaintMineral Turpentine Oil (MTO), White Spirit
Spirit VarnishFrench PolishAlcohol (Methylated Spirit)
Lacquer-Lacquer Thinner (a mix of solvents)
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