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Design Course
Designing of Plastic Products for Injection Moulding
Manufacturing Methods and Technologies
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Painting
Painting on plastic parts are done to enhance the aesthetics and to obtain uniformity in color and texture in assemblies made of different material and different processes. Painting also hides the molding defects. Painting also protects the plastic part from harsh environmental conditions. There are four basic components of paints. They are polymeric resign, pigment or dyefor color, thinning agent and additives for adhesion and appearance.
Types of paints used on plastics
- Polyurethane paints – It provides durable finish and cures without heat. It is compatible with most of the plastics.
- Vinyls – They produce soft rubbery finish.
- Epoxies – They produce hard, tough and glossy finish.
- Acrylic paints – They provides brittle, scratch resistant and oil resistant finish.
Type of solvent system used in painting of plastics
- Organic solvent system – In this the organic solvent forms a strong chemical bond with the plastic substrate for better adhesion.
- Water based system – In this the solvent forms a weaker bond with the plastic substrate. They are mostly preferred because of environmental and health issues.
Methods to cure paint
- Air-curing
- Heat curing
- Two component paint system
- Exposure to oxygen or UV radiation
Animation Wipe on Paint:
Animation Painting Guns:
Spray painting – This is the most common method for painting plastics. The method can be conventional, airless or electrostatic.
There are five basic type of spray gun machine used
- Gun is stationary and part is movable
- Gun is reciprocating part is stationary
- Rotating gun and movable part
- Rotating gun and stationary part
- Spinner type movable part
