Sun and Plastic: The Risk of Fading. Chimar’s Solution

Summer means outdoor living, relaxing under the sun, and spending time outside. But while a few hours of sun exposure might cause sunburn for us, the long-term effects on plastic can be even more visible… and permanent. Have you ever noticed that old garden chair that used to be a vibrant red but now looks faded and worn? It’s not just the passing of time — it’s mostly due to sunlight.

The Effect of Sunlight on Plastic: A Molecular Issue

Ultraviolet (UV) rays, part of solar radiation, are among the main causes of degradation in plastic materials exposed to the outdoors. When UV rays hit the surface of the material, they trigger a process called photodegradation, which can lead to color fading, cracking, or loss of mechanical integrity.

In particular, the color pigments in plastic can undergo molecular changes: UV rays break down the bonds in chromophore molecules — the ones responsible for color. This leads to a loss of brightness and the transformation of plastic into a dull, uneven surface.

This phenomenon is even more noticeable with organic pigments, which — due to their carbon content — are more sensitive to oxidation than inorganic pigments.

Light is only part of the story. Humidity, dust, salt, and rain are other atmospheric agents that interact with plastic materials, affecting both appearance and performance.

Imagine two identical objects: one left outdoors on a Tokyo terrace, the other under the Moroccan sun. Although both are exposed to sunlight, the different levels of humidity, pollutants, and UV intensity will cause them to age differently.

Geography and Solar Intensity: Colors Fade Faster in the Tropics

UV intensity varies significantly depending on latitude. It’s no coincidence that outdoor furniture lasts longer in Northern Europe than a similar item placed on a Mediterranean terrace.

The closer you are to the Equator, the greater the solar radiation intensity — and the faster the plastic degradation. Studies and global irradiation charts confirm it: the sun doesn’t shine the same way everywhere.

How Do We Test Plastic’s Resistance to Sunlight?

Waiting years to see if a material fades isn’t a practical option for the industry. That’s why specific machines exist to simulate in a short time what would happen in nature over months or years.

These are accelerated weathering machines, which expose samples to UV radiation (often using xenon lamps that simulate the solar spectrum very accurately) and sometimes to other environmental factors. These tests allow us to predict how a material will behave under extreme or prolonged conditions.

Waiting years to see if a material fades isn’t a practical option for the industry. That’s why specific machines exist to simulate in a short time what would happen in nature over months or years.

These are accelerated weathering machines, which expose samples to UV radiation (often using xenon lamps that simulate the solar spectrum very accurately) and sometimes to other environmental factors. These tests allow us to predict how a material will behave under extreme or prolonged conditions.

Preventing Fading: Pigments and Additives as Allies

To protect plastic products, two strategies can be used:

1. Choosing more resistant pigments
   Inorganic pigments offer superior light resistance compared to most organic ones, making them ideal for outdoor applications. However, they have a more limited and less vivid color range.
   A good strategy is to create hybrid formulations by combining organic and inorganic pigments to balance appearance and durability. In some cases, organic pigments can be treated to improve lightfastness. Among the most commonly used are zinc oxide and titanium dioxide, which also help protect the polymer.


2. Adding UV-protection additives
   Just as sunscreen protects skin, UV additives protect plastic. These substances are incorporated into the plastic mix during production and work by absorbing or deflecting UV rays before they reach the color pigments.
   Light stabilizers like HALS (Hindered Amine Light Stabilizers) and UV absorbers have different chemical mechanisms, but the same goal: protecting the material’s structure.

Color Can Be Protected

Sun, humidity, dust, and salt don’t have to be plastic’s enemies. With its expertise in high-performance masterbatch and pigment formulations, Chimar offers the right combination of targeted solutions to produce outdoor products that retain their beauty, color, and functionality over time.