Introduction
Ultraviolet (UV) absorbers are important additives widely used in plastic products to improve light stability and durability. They function as light stabilizers, protecting polymers from degradation caused by ultraviolet radiation in sunlight.
UV absorbers work by absorbing harmful ultraviolet radiation and converting it into harmless thermal energy, preventing the UV light from damaging the polymer structure. These additives are commonly used in products such as:
- Plastic sheets and panels
- Electrical cables and wires
- Plastic pipes
- Plastic films and packaging materials
In many cases, UV absorbers are added to plastic films and protective materials to prevent UV radiation from damaging the contents or materials being protected.
Ultraviolet Radiation and Its Effects on Plastics
Sunlight contains a wide spectrum of electromagnetic radiation. The radiation that reaches the Earth’s surface mainly includes:
- Ultraviolet (UV) radiation
- Visible light
- Infrared radiation
The energy of electromagnetic radiation is inversely proportional to its wavelength, meaning shorter wavelengths carry higher energy.
Among these types, ultraviolet radiation in the wavelength range of 290–400 nm has the shortest wavelength and highest energy, making it the most destructive to polymer materials such as plastics.
Why UV Radiation Damages Polymers
The chemical bond energy of most organic polymer materials is typically in the range of 290–400 kJ/mol, which is similar to the energy of UV radiation. Because of this, UV radiation can easily break chemical bonds within polymer chains.
As a result, ultraviolet radiation becomes one of the main causes of photo-aging in plastics.
However, different polymer structures have varying sensitivity to different UV wavelengths, meaning some materials degrade faster than others when exposed to sunlight.
Photochemical Reactions in Plastics
The excellent mechanical and physical properties of plastics are largely due to their long polymer chains (macromolecular structures). However, when exposed to high-energy UV radiation, several photochemical reactions can occur.
When polymer materials absorb UV light, the molecules may enter an electronically excited state. These excited molecules can initiate a series of reactions, including:
- Free radical chain reactions
- Oxidation reactions
- Photo-oxidative degradation
These reactions can cause:
- Chain scission (breaking of polymer chains)
- Cross-linking of polymer molecules
Both processes significantly affect the material’s properties.
Effects of UV Aging on Plastic Materials
UV-induced degradation can lead to several visible and mechanical changes in plastic products, including:
- Color changes or darkening
- Material brittleness
- Hardening of the polymer
- Surface cracking
- Reduced mechanical strength
- Decreased electrical insulation performance
Over time, these changes cause the plastic product to lose its functional performance and service value.
Role of UV Absorbers
UV absorbers help protect plastics by absorbing harmful UV radiation before it can damage the polymer structure.
Key benefits include:
- Improved weather resistance
- Extended service life of plastic products
- Protection against color fading and surface cracking
- Preservation of mechanical and electrical properties
Because of these advantages, UV absorbers are widely used in plastics exposed to outdoor environments.
Typical Applications of UV Absorbers
UV absorbers are commonly used in a variety of plastic products, including:
- PVC sheets and panels
- Outdoor pipes and profiles
- Electrical cables and wire insulation
- Plastic films and packaging materials
- Automotive plastic components
These applications require long-term resistance to sunlight exposure and environmental aging.
