DESIGN FOR MANUFACTURING (DFM) GUIDE

Designing Plastics for Outdoor Use

Sunlight can be surprisingly destructive to plastics. This guide covers the fundamentals of UV degradation and how to select the right material for products that will live outdoors.

What is UV Degradation?

Ultraviolet (UV) radiation, a component of sunlight, contains high-energy photons that can break down the chemical bonds in polymer chains. Over time, this exposure causes a process called photodegradation, which leads to undesirable changes in the plastic.

Common Effects of UV Degradation:

Color Fading & Yellowing: The most obvious effect is a change in color. White plastics may turn yellow, and colored plastics can fade or become chalky.
Brittleness: The material loses its ductility and impact strength, becoming brittle and prone to cracking under stress.
Loss of Strength: The material's tensile strength and other mechanical properties are significantly reduced.

A drone shell, an example of a product that requires UV resistant materials for outdoor use

Choosing Inherently UV-Resistant Plastics

The best strategy is to select a material with natural resistance to UV radiation.

ASA (Acrylonitrile Styrene Acrylate)

ASA is the champion of UV-resistant plastics for opaque parts. It is structurally very similar to ABS but is engineered to be highly resistant to UV light and weathering. It is the go-to material for automotive exterior trim, garden equipment, and outdoor electronics enclosures.

Acrylic (PMMA)

Acrylic has exceptional inherent UV stability. It can withstand years of sun exposure without yellowing or degrading, which is why it's the standard material for outdoor signage, architectural glazing, and automotive tail lights.

Polycarbonate (PC)

While standard PC has poor UV resistance, special UV-stabilized grades are widely available. These grades have additives that protect the polymer, making them suitable for outdoor use in applications requiring high impact strength.

Other Protection Strategies

Using Additives and Coatings

UV Stabilizer Additives: During injection molding, UV-absorbing additives can be mixed in with plastics that are normally vulnerable (like ABS or Polypropylene) to improve their weather resistance.
Protective Coatings: Applying a UV-resistant paint or clear coat is a very effective way to protect a non-resistant substrate. The coating acts as a barrier, absorbing or reflecting the harmful UV radiation before it can reach the plastic underneath.
Carbon Black: Adding carbon black pigment is one of the most effective and low-cost ways to protect a plastic from UV degradation. The black pigment absorbs the UV radiation and converts it to heat, protecting the polymer chains. This is why many outdoor plastic items (like garden hoses and car trim) are black.

UV Resistance FAQ

Why does my car's dashboard crack over time?

This is a classic example of UV and thermal degradation. Older cars often used plastics like ABS or PVC for dashboards. The combination of intense UV radiation coming through the windshield and high temperatures causes the plasticizers to leach out, making the plastic brittle and prone to cracking.

What is the best 3D printing material for outdoor use?

For FDM 3D printing, ASA is by far the best choice. It prints similarly to ABS but has vastly superior UV resistance. For powder-based printing, Nylon (via SLS or MJF) can be used, but it's recommended to paint or coat the part for long-term outdoor exposure.

How long will a "UV-resistant" plastic last outdoors?

This depends on the material, any additives, and the intensity of the UV exposure in the specific geographic location. Material datasheets often provide weather-resistance data based on accelerated lab testing (e.g., "F1" or "F2" ratings under UL 746C), which can help predict outdoor lifespan.