Technical papers on decorating and finishing plastic parts: preparation, painting, printing and special-effect finishes.
- Techniques for Measuring Adhesion and Abrasion Durability of Coatings and Inks – Part 2
Abrasion test methods for coatings and inks: Norman RCA abrader, Taber rotary and linear abrasers, applicable ASTM standards and fixturing. - Techniques for Measuring Adhesion and Abrasion Durability of Coatings and Inks – Part 1
Adhesion test methods for coatings and inks on plastics: ASTM D3359 tape test, ASTM D4541 pull-off testing, and where each method misleads. - Advanced Technologies for Decorating Polyethylene
Secondary processes for polyethylene: why PE resists decorating, plasma and Pyrosil pretreatment, single-pass UV LED inkjet, coatings and laser marking.
Other topics
- Laser Marking
- Surface Pretreatments & Adhesion Bonding
- Inkjet Printing
- Anti-counterfeiting
- Industrial Coatings
- Laser Welding
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Frequently Asked Questions
Which decorating process is right for a given plastic part?
It follows from the geometry, the volume, the durability requirement and the substrate. Pad printing handles contoured and steeply drafted surfaces -- 360-degree pad printing on a 60-degree draft angle is a documented example. Digital inkjet suits mass customisation and variable data. In-mould decorating puts the graphic behind the surface. Screen printing and hot stamping remain right for particular finishes. Most programs end up combining two of them.
Why does decorating fail on plastic parts that printed fine in trials?
Almost always at the interface rather than in the ink. Low surface energy substrates, mould release, slip agents and plasticiser migration all interfere with wetting, and a part that prints acceptably on a clean trial moulding can fail weeks later in production when the release agent changes. Pretreatment and incoming surface control are therefore part of the decorating specification, not a separate concern.
How is decorating durability actually tested?
Adhesion and abrasion are distinct properties and need distinct tests -- a mark can pass a tape adhesion test and still fail in service through abrasion, and the reverse also happens. Standard adhesion test methods are used alongside abrasion testing appropriate to the application, and the acceptance criteria come from how the product is handled in use.
Can special-effect finishes be achieved without secondary painting?
Often, yes. Special-effect colourants and topcoats can simulate soft-touch, woodgrain, slate and cedar shake finishes. Documented work includes polymer roofing tiles decorated and coated to simulate slate and cedar shake with a 40-year lightfastness, fire and wind warranty, and full-colour digital printing under an FDA chemical-resistant clear topcoat that survives dishwasher cycling.
What is backlit day/night decorating?
It is the technique behind automotive buttons that read as a solid surface in daylight and illuminate a legend at night. The part is painted and then the legend is removed by laser ablation through the paint layers, so the light passes only through the ablated character. It depends on tight control of ablation depth against paint film build.
