To Paint or not to Paint, That is the Question!

When it comes to painting completed prototype, a gift or a product, we often consider:

  • Matching an actual color;

  • Applying an even coat of paint;

  • Choosing the “right paint” and hoping that it does not peal a month later or chip when the item is handled.

What is not so obvious is that many paints weaken plastics by up to 50% so your project may look great but will shatter when you drop it! Using plastics with molded-in colors avoids all of these problems!

One study on the effect of painting on four different plastic substrates: general-purpose ABS, high-impact ABS, weather-resistant ASA, and 10% talc-filled nylon 6/polyethylene ionomer blend found that impact strength by 20-50% on three of these plastics. That is a big change and can cause your parts to break even though they may look nice!

The effect of the topcoat on the general-purpose ABS was particularly notable. Unpainted, the general-purpose ABS had 22% strain at break. After painting with just the topcoat, the general-purpose ABS became very brittle, with just 5% strain at break. On the other hand, if the clear adhesion promoter was applied before the topcoat, the strain at break was 17.5%, still not very encouraging statistics. Obviously specific paint and adhesion promoters were tested in the study and if different chemistries were tested, the results would be different but it is hard to know which paint will give you a perfect outcome for your project. Using plastics with molded-in colors will give your project a perfect outcome!

To download full-text PDF of Paint on Plastic Study click here

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