PAINTING AND COATING OF PLASTICS JAIME CYPHER RYAN

PAINTING AND COATING OF PLASTICS JAIME CYPHER RYAN SEYLER DANIEL WILSON

Introduction n Purpose of coating and painting • Decorative • For consumers • Protection • From unwanted environmental effects • Helps overall performance n Methods: Painting, Powder Coating

Introduction n Background on Painting • • More aesthetically pleasing Most common method of coating Paint applied to surface as liquids Higher surface energy = Better

Introduction n Background on Powder Coating • Used on metals, ceramics, & plastic • Powdered solid coating applied

Preparation of Plastic n Prevent foreign substances • Detergent cleaning • Salts and Oils • Gloves • Fingerprint soils • Destaticizing air blow-off • Operate in “clean room”

Paint Adhesion n Overcoming surface smoothness • Micro-etch with chemical agent • Avoid over and under etching • Solvent choice is critical • De-glazing with abrasive media • Areas of frictional heating • Cross-linked skin forms

Paint Adhesion • Oxidative surface treating • • • For non-polar plastic surfaces Polarity from chemical reaction Polypropylene and Polyethylene Open flame exposure Photosensitizers and UV light

Painting n Advantages of Painting • • Protective coating Richer color than internal colorants Thin coatings possible Same color parts in assembly

Painting n Disadvantages of Painting • Poor adhesion to certain plastics • Air pollution • Disposal of waste • Paintability varies among plastics

Types of Painting Processes n Spray n Silk-Screening n Dip-Coating n Rolling n Brushing n Wiping

Spray n Most common and versatile method n Easily automated n Air pressure & liquid stream mixed n Distance from part & speed important n Overspray unimportant, booths used

Spray n Advantages • Excellent surface quality • Uniform thickness • Few runs • Few imperfections

Silk-Screening n Series of screens prepared • Multi-color images • One screen per color • One screen per portion n Drying time necessary

Silk-Screening n Advantages • Flat & cylindrical parts • High volume production n Disadvantages • Adhesion problems • Due to bad preparation • Presence of mold release

Others n Dip-Coating • Immersion in paint & rotating n Brushing, Rolling, & Wiping • Used less frequently • Advantages • Special effects • Small lots

Powder Coating n Process • Immersion in plastic particles or sprayed • Baked at high temperatures • Caution of degradation from fusion

Powder Coating n Types • • Epoxy Hybrid Aromatic Urethane TGIC Polyester

Powder Coating n Advantages of Powder Coating • • Many types of finishes Better performance Better for environment Low cost

Powder Coating n Disadvantages of Powder Coating • Degradation or softening possible • Causes part deformation • Long color change time

New Technology n In-Mold Painting • Automotive uses • Insert-molding technique • Eliminates paint-facility expenses • Better design flexibility • Recycling easier

New Technology n 2 K Polyurethane Coating • Automotive uses • Excellent appearance • Excellent performance • Curing at low temperatures • Wide variety of plastics

Materials n Not to be considered • PE, PP, and low polarity plastics • Low surface energy n Cautionary materials • PC & PS • Exposure to sensitive solvents

Design Requirements n Material Selection n Adding raised part details • Ink applied using roller n Flat surfaces if possible • Uniform thickness • Cheaper

Examples n Painting

Examples n Powder Coating

Conclusion n Coating & Painting valuable • Decorative • Protective n Preparation is crucial n Many different processes n Becoming more popular today