Introduction

Most engineers and designers come from the metal world. Therefore, many of them make assumptions on the predicted performance of plastic properties based on their metals background.

Unlike metals, the knowledge of color and appearance is extremely important in the case of plastics. Most plastic parts have dual functions— physical performance and aesthetics.  Aesthetics are important since very few of the parts need to be painted or otherwise decorated if designed and manufactured with due diligence.

On the other hand, even if we are designing the most aesthetically critical metal components such as exterior automotive parts, we mostly choose the metals and alloys based only on the physical properties, weight, and cost. The aesthetics are left to the paint specialist, who will in most cases find a paint system (primer, paint, and application method) that will meet the cost, durability, and cosmetic requirements.  In other words, aesthetics and physical properties are quite independent of each other. A vast majority of metal parts meet their aesthetic and environmental requirements just by getting brushed, plated, chromate conversion coated or anodized.

Plastic parts not only need to meet the short-term color and appearance requirements, but also need to be resistant to long term color shift and fading.

This webinar is in two parts.  In part one we discussed the appearance and color factors consisting of:

• Material
• Design
• Tooling
• Processing

In part 2 we will discuss the fundamentals of color and appearance, specifications, measurement and tolerances.

The following topics will be discussed:

Perceived Color

Observer, pigment and Light

Color Measurement

Munsell system color – hue, value, and chroma

Hunter L, a, b system.

Color Difference

Delta E or E

McAdam’s ovals

Recommended E for plastics

Metamerism

Same color looking different under different lights

Avoiding metamerism

The Visible Spectrum

Common Light Sources

Gloss

How gloss affects overall appearance

Gloss Level Measurement

How to measure and specify gloss

Specifying and Controlling Custom Colors

Proven techniques for color specification and control

Standardizing Viewing Conditions

Cosmetic Specifications of Injection Molded Parts Publication Number AQ-103

Putting It Altogether