Chloe Zhang
Ultraviolet (UV) light can cause problems for polymers, but it can also be used to join plastics together or to protect them. When plastics are exposed to UV light, they can degrade and turn yellow. To prevent this, anti-UV chemicals can be added to plastics, similar to those used in sunscreen, to protect against UV rays. There are three main kinds of UV-resistant additives: blockers, absorbers, and stabilizers. Blockers coat plastics with a protective layer, while absorbers are usually organic compounds designed to absorb UV light and emit less harmful energy in the form of heat. Stabilizers, such as hindered amine light stabilizers (HALS), turn excited UV reactions into stable chemical reactions. While no plastic is entirely protected against UV rays, some plastics offer excellent levels of UV resistance, such as acrylic, polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF). These plastics can be used in various applications, including outdoor signs, light fixtures, and protective tubing for optic fibers.
| Characteristics | Values |
|---|---|
| How to block UV light with plastic | Use anti-UV chemicals, similar to those used in sunscreen, during the mixing and injection moulding process |
| Use UV-resistant plastics such as acrylic, HDPE, PAI, PVDF, and polytetrafluoroethylene (PTFE) | |
| Use UV stabilizers, which absorb and dissipate UV radiation as low-level heat | |
| Use blockers like carbon black and titanium dioxide to coat plastics with a protective layer | |
| Use absorbers like benzophenones and benzotriazoles, which are organic compounds that absorb and re-emit UV light as less harmful wavelengths |
Explore related products
What You'll Learn
Plastic types that block UV light
Plastics are prone to UV damage, which can lead to discoloration, reduced impact and tensile strength, and deformation of the material. Therefore, it is important to select UV-resistant plastics for outdoor use. Here are some of the plastic types that can block UV light:
Acrylic
Acrylic is one of the few manufacturing materials that is inherently UV-resistant. It suffers only about 3% degradation over a 10-year period when used outdoors. It also offers good scratch resistance, making it a popular choice for long-term use in signs, displays, light fixtures, and decorative panels. However, acrylic is not very strong and is brittle, so it is rarely used for load-bearing parts.
HDPE (High-Density Polyethylene)
HDPE is a durable thermoplastic often used in playground equipment due to its soft yet strong qualities. It can be easily melted and molded into various shapes without forming sharp, dangerous edges when broken, making it safe for children's play equipment.
Polycarbonate
Polycarbonate is another plastic that can be used for outdoor applications. When combined with benzotriazoles, it maintains its transparency while blocking UV light.
PVDF (Polyvinylidene Fluoride)
PVDF is a UV-resistant plastic that offers excellent thermal stability, abrasion protection, and resistance to chemicals and UV radiation. It is easy to weld due to its high heat resistance. PVDF comes in two forms: homopolymer and copolymer, with the former being stronger and stiffer, while the latter offers superior impact and stress crack resistance.
PAI (Polyamide-Imide)
PAI is a strong, chemically-resistant plastic with a high melting point, excellent stiffness, wear resistance, and low friction qualities. It is commonly used for magnet wires, surgical instruments, and other parts requiring tight tolerances and dimensional stability. However, PAI is expensive and often requires additional post-curing processes to achieve full UV protection.
Kick Plastic Packaging: Eco-Friendly Alternatives for Your Home
You may want to see also
Explore related products
Additives to improve UV-resistance
Plastics are prone to UV damage, which can cause discolouration, loss of tensile strength, and make them brittle and prone to cracking. To prevent this, plastics can be treated with additives to improve their UV resistance.
There are three main kinds of UV-resistant additives: blockers, absorbers, and stabilizers. Blockers coat plastics with a protective layer, keeping them safe from UV radiation. Carbon black is a common blocker, blocking UV rays at a rate of about 2%. Titanium dioxide, a pigment, is also an effective blocking solution. Absorbers are usually organic compounds designed to absorb UV light and emit a less harmful wavelength, such as heat, in its place.
UV absorbers are formulated according to the product's exposure to the outdoors, direct sun, and specific climate conditions. They must also be designed in accordance with the plastic's chemical characteristics. UV stabilizers are another additive that can be added to plastics to increase their resistance to UV light. UV stabilizers are used in industries such as agriculture, where greenhouse films are exposed to UV light and must be protected.
Some plastics are naturally more resistant to UV light. Polycarbonate is a good option for windows and signage due to its transparency and strength. HDPE is a durable plastic that is easy to melt and mold into unique shapes and is resistant to alcohols, bases, and acids. It is often used in playground equipment and outdoor furniture.
Storing Bread Before Plastic: Ancient Techniques
You may want to see also
Explore related products
Plastic degradation and how to prevent it
Plastic degradation is a significant environmental concern, with plastic waste accumulating in the environment at an alarming rate. Plastics are useful materials that have become integral to our daily lives, but they can persist in the environment for hundreds of years or longer. The persistence of plastics is due to their chemical structure, which makes them resistant to degradation. However, this resistance has negative consequences, as plastic pollution can lead to ecological damage and adverse effects on human health.
The degradation of plastics occurs through various biological, chemical, and physical processes. In natural environments, plastics can degrade through processes such as thermal oxidation, hydrolytic cleavage, and photo-oxidation initiated by UV light. The specific degradation process depends on factors such as temperature, pH, salt concentration, and pressure. For example, plastics in the ocean can degrade primarily through slow, photo-oxidative degradation due to the low temperatures and UV light exposure. On the other hand, when plastics are landfilled or sink below the sunlit regions of the ocean, they may undergo slow thermal oxidative degradation and hydrolysis.
The rate of plastic degradation varies significantly, with biodegradation taking decades or even centuries, while some industrial processes can completely decompose plastics in hours. The type of plastic also influences the degradation rate, with different plastics having varying resistance to degradation. For instance, high-density polyethylene (HDPE) in the marine environment has a wide range of specific surface degradation rates (SSDR), with some bottles having estimated half-lives of 58 years, while pipes can take up to 1200 years to degrade.
To prevent plastic degradation and extend the lifespan of plastic items, several methods can be employed:
- Using polymer stabilizers: These additives help stabilize plastics against weathering and degradation, such as hindered amine light stabilizers (HALS) and UV-absorbers.
- Incorporating antioxidants: Antioxidants protect plastics from thermal degradation by terminating the chain reaction caused by the absorption of UV light.
- Biodegradable additives: These additives accelerate the degradation of plastic waste, improving its biodegradability and reducing the environmental persistence of plastics.
- Employing bacterial strains: Certain bacterial strains, such as PET hydrolase and PCL-cutinase, have the potential to efficiently degrade plastics and improve ecological health and human safety.
- Blocking UV light: UV light can accelerate plastic degradation, so using materials that block UV rays, such as specific types of plastics, can help prevent degradation.
The Evolution of Nicole Kidman's Appearance: Natural or Enhanced?
You may want to see also
Explore related products
The best UV-resistant plastics
While no plastic is entirely protected against UV rays and radiation, some plastics offer excellent levels of UV resistance. This is important because, like human skin, plastics are prone to UV damage, which can cause disintegration, discolouration, loss of strength, and increased brittleness.
One of the best UV-resistant plastics is acrylic, which is inherently UV-resistant and used in outdoor signs, light fixtures, and window frames. Acrylic is a transparent plastic that suffers as little as 3% degradation over a 10-year period when used outdoors. However, it is not very strong and is quite brittle, so it is rarely used for load-bearing parts.
Another good option is polyester, including PET, although it will eventually fog up and become powdery. Polyvinyl chloride (PVC) can also hold up for decades in the sun if it is treated for sun resistance. High-density polyethylene (HDPE) is a thermoplastic that is extremely resistant to acids, alcohols, and bases. It is often used in playground equipment because it is durable yet soft and safe, as it does not form sharp edges when it breaks.
EPDM is another material that withstands UV very well, although it is not a plastic. It forms an ash layer on its surface that prevents further deterioration.
Brain Plasticity: Unlocking Potential Through Intense Study
You may want to see also
Explore related products
How to test UV light resistance
To test the UV light resistance of plastic, one can perform a simple test at home or outdoors. Alternatively, one can use a testing lab.
For a simple test, one can hold a piece of paper behind the plastic and observe the difference in brightness. This test can be performed in a dark room or outdoors under sunlight.
Another simple test is to expose the plastic to sunlight for a long period. This method, however, is time-consuming, as it would take years to see the changes in the material caused by outdoor exposure.
For a quicker result, one can use a QUV accelerated weathering tester, which reproduces the damaging effects of sunlight, rain, and dew. This machine can reproduce in a few days or weeks the damage that occurs over months or years outdoors. The plastic can also be placed in a Xenon arc test chamber, which reproduces the entire spectrum of sunlight, ultraviolet, infrared, and visible light.
When using a testing lab, one should inquire about the standards the lab is using, as they can differ slightly. Some of the standards include:
- ASTM D4329-13 Standard Practice for Fluorescent Ultraviolet (UV) Lamp Apparatus Exposure of Plastics
- ASTM D5208-14 Standard Practice for Fluorescent Ultraviolet (UV) Exposure of Photodegradable Plastics
- ASTM D4587-11(2019)e1 Standard Practice for Fluorescent UV-Condensation Exposures of Paint and Related Coatings
- ISO 4892-3:2016(en) Plastics — Methods of exposure to laboratory light sources — Part 3: Fluorescent UV lamps
- IEC 60068-2-5 Ed. 3.0 en:2018 Environmental Testing – Part 2-5: Tests – Test S: Simulated Solar Radiation at Ground Level And Guidance For Solar Radiation Testing And Weathering
Septic Tanks: Plastic vs. Concrete in PA — Legal?
You may want to see also
Frequently asked questions
Acrylic is one of the only manufacturing materials that is inherently UV-resistant, offering good scratch resistance and long-term durability. Other UV-resistant plastics include PAI, PVDF, and HDPE.
UV stabilizers in plastics work by absorbing UV radiation and dissipating the energy as low-level heat. These chemicals resemble those in sunscreen products, which protect the skin from UV rays.
There are three main kinds of UV-resistant additives: blockers, absorbers, and stabilizers. Blockers coat plastics with a protective layer, keeping them safe from UV radiation. Carbon black is a common blocker for outdoor applications, blocking against UV rays at a rate of about 2%. Absorbers, such as benzophenones and benzotriazoles, are usually organic compounds designed to absorb UV light and emit a less harmful wavelength, such as heat, in its place.
One simple way to test if a plastic is UV-resistant is to hold it up to a light source and observe the brightness on the other side. The absorption spectrum of the plastic can also be checked to determine its UV resistance.
