UV stabilizers in plastic: 4 common types and applications - EuroPlas
UV stabilizers in plastic: 4 common types and applications - EuroPlas
Despite their outstanding mechanical properties, plastic products are highly prone to degradation as a result of excessive exposure to harmful environmental factors, one of which is ultraviolet (UV) light. Hence, to maintain their good conditions, the application of UV stabilizers in plastic will be an ideal choice. So, what are these substances and how exactly do they benefit plastic products? Let’s find out in this article!
For most plastic products, especially those that are used outdoors, it is inevitable to be vulnerable to negative environmental effects such as ultraviolet (UV) light, oxygen, temperature,... The frequent exposure to those elements leads to the transformation in the chemical structure of polymers, resulting in the degradation of end products’ mechanical properties.
1. Degradative impacts of UV light
UV light (also known as ultraviolet light) is a type of electromagnetic radiation with wavelength ranging from 290 nm to 400 nm. It accounts for approximately 10% of the total electromagnetic radiation released from the sun. The thing is, each type of polymer is sensitive to certain wavelengths within the 290-400 nm UV region.
When being exposed to UV lights, certain components in a polymer (known as chromophores) will absorb UV radiation. This long-term process eventually breaks down the polymer chains, thus leading to the deterioration of physical properties. These may vary between different groups of polymers but normally include the loss of impact strength, changes in color, cracking, loss of elongation, tensile strength or chalking of the surface.
Let’s take a plastic outdoor chair as an example. Under the effects of UV light, its color will be faded and spotted on the surface while the plastic itself becomes easily broken. In this case, the polymer's structure has been apparently changed, leading to the degradation in physical properties of the end-products. Hence, the application of UV stabilizers in plastic plays an indispensable part in the durability of your products.
2. UV stabilizers in plastic: What are they and how many types do they have?
As one of the most effective solutions to the UV degradation of plastic, UV stabilizers are chemically formulated to absorb UV light’s energy, thus minimizing the contact between plastic surface and the UV rays. Normally, UV stabilizers are embedded into polymer combinations during the mixing phase to ensure it will disperses well on products' surfaces. Interestingly, there are at least 3 types of UV stabilizers in plastic, which differ from each other regarding the mechanism of action.
2.1. Absorbers
Absorbers function by absorbing UV light, which may be absorbed by chromophores and change the harmful UV radiation into harmless infrared radiation or heat. Cost effective they might be, UV absorbers are most suitable for products with short-time exposure only. In the long run, this material is much less efficient. Some popular UV stabilizers of this type are: carbon black (which is the most common one thanks to its black color), rutile titanium oxide (which is effective in the 300 - 400 nm range but work less efficiently in the short wavelength ranging below 315), hydroxybenzophenone, hydroxyphenyl benzotriazole (this type is suitable for neutral or transparent applications but not very useful in thin parts below 100 microns), benzophenones for PVC, benzotriazoles and hydroxyphenyl triazine for polycarbonate, oxanilides for polyamides.
2.2. Quenchers
Another type of UV stabilizers in plastic are quenchers, which are also called light stabilizers. They work by quenching molecules that are over-excited during the UV absorption, and transfer the energy absorbed into heat. Generally, compared to its counterparts, quenchers are considered as the least effective methods of blocking UV radiation.
2.3. HALS
When it comes to the most effective UV stabilizers in plastic, HALS (Hindered amine light stabilizers) will undoubtedly be that one. Unlike its fellows, which work in the absorption phase of polymer, HALS take place in the early of the polymer degradation process. When free radicals are formed, it then traps them, thus preventing them from doing any damages to end-products. However, the chosen HALS must be compatible with the polymer, or else it can cause die build up at the extruder die and inefficient polymer protection.
3. Common applications of UV stabilizers in plastic industry
Since those types of UV stabilizers work differently, they’re commonly added in polymer combinations in multiple ways. Here is how they are applied in some popular types of polymers.
3.1. UV stabilizers for PP (Polypropylene)
Polypropylene is one of the most common types of polymers that are widely used in various applications such as raffia, extrusion,... However, its greatest disadvantage is the thermal sensitivity. As unstable species (hydroperoxides) and radicals can form during polypropylene’s processing, it strongly absorbs UV light when being exposed to the Sun. Hence, the application of UV stabilizers in PP is extremely important to end-products’ longevity. HALS is amongst the most commonly used UV stabilizers for PP products.
3.2. UV stabilizers for PE (Polyethylene)
Though less sensitive than PP, PE also needs specific stabilizers against UV light. The chosen one varies between multiple types of PE.
In HDPE tapes applications, a good retention of physical properties after light exposure is mostly required. Therefore, the combination of two types of HALS stabilizers, which is a low molecular mass HALS and a high one, is commonly used to improve the mechanical properties of HDPE tape applications.
Whereas, the deterioration of products’ visible appearance (such as chalking, loss of gloss and cracks) is the main concern in HDPE injection moulding. In this case, the mixture of two types of HALS still can fulfill end-products’ requirements. Furthermore, the lightfastness of the pigment can be improved by the addition of a small amount of benzotriazole type UV absorber.
For LDPE blown film, things get more complicated as UV stabilizers in plastic films are required to increase the films’ service life. However, the use of chemicals (such as pesticides) in agriculture often considerably afflict the function of UV stabilizers since they mostly are sulfur and/or halogen-based compounds. Nickel organics, after a long period being used as a temporary solution, has been finally replaced due to its serious environmental impacts by the combination of high Mw HALS with a metal oxide and a stearate.
3.3. UV stabilizers for HIPS (High impact polystyrene)
HIPS is a low cost plastic material that is specified for low strength structural applications (eg. covers, housings, signage, display items) when impact resistance, machinability, and low cost are required. The main requirement for UV stabilizers in this type is the retention of physical properties, which can easily be handled by the combination of UV absorber benzotriazole and liquid low Mw HALS.
4. Selection criteria of UV stabilizers
As we already discussed, there are different types of UV stabilizers in plastic and specific requirements for each type of resins. These below are key criteria needed consider carefully before making up your mind:
- Environment: Anti UV additives are formulated in accordance with the specific climate conditions that end-products are exposed to.
- End-product properties: As each product has different physical characteristics, the chosen UV stabilizers must be completely compatible with the current components in order to achieve the best result.
- Color: Pigments are vital components in almost every type of plastic product. Since each color has a different level of sensitivity to UV light, the stabilizers added must be fitted to the color characteristics to ensure it disperses well on the plastic surface.
- Product’s life cycle: As mentioned above, the protection capacity varies among three types of UV stabilizers. HALS can be active for the longest period, while the others only work sufficiently in the short term. Thus, plastic enterprises should consider carefully to find the light additives that suit them best.
5. EuroPlas UV stabilizers in plastic
With nearly 14 years of experience in the plastic material market, EuroPlas products have been available in over 80 countries worldwide. Plastic additives, especially UV stabilizers are one of our best sellers, which have won the trust of millions of customers. Most importantly, all of our products are tailor made based on customers’ requirements, making each output become a perfect right fit for your end-products.
AO, UV, FRs, Pigments, impact modifier additive for PVC
Baoxu Additives for PVC
Baoxu Chemical Supply Antioxidants, Colorants, flame-retardants, Heat Stabilizers, Impact Modifiers, Lubricants, OBAs, UV Stabilizers for PVC plastics. We Simply Plastic Compounding, Heat resistance, color are 2 difficulties in PVC processing.
Antioxidant for PVC
Polymer antioxidants can be added to improve the shelf life of the product or to improve its high-temperature stability. while adding a stability margin during thermal processing. Antioxidant BX AO , BX AO , BX AO TPP is used a general purpose Antioxidant for PVC plastics.
Compatibilizer & Impact Modifiers for PVC
Impact Modifiers are substances that increase the durability of molded or extruded plastics, especially those that need to be constantly subjected to impact forces like cold weather. They are added to compounded materials to provide performance features. They provide strength and break resistance to the product for which they are added. They also provide rigidity to the product to prevent it from wrapping or sagging during everyday use. Mbs and acrylic group impact modifiers are used for PVC plastic, used to replace Brands like Dow, Baoxu Chemical offer impact modifier for PVC as table below
TypeItem namekanekaDowMitsubishiApplicationDosage %AcrylicBX IM 750B564KM-1Opaque PVC4-5BX IM 81PA 20/B513Transparent PVC4-5MBSBX IM 156B622BTA 707/717Transparent PVC4-8BX IM 126B564BTA 736Opaque PVC4-8Heat Stabilizer for PVC
For the processing of PVC, thermal decomposition does not change its properties much, mainly affecting the color of the finished product, and adding heat stabilizers can inhibit the initial colorability of the product. In addition, if there is oxygen in the thermal decomposition process of PVC, there will be colloidal carbon, peroxide, carbonyl and ester-based compounds. In this case, it is necessary to add a heat stabilizer in the process of PVC processing, so that to a certain extent, it can replace the unstable chlorine atoms in PVC, absorb hydrogen chloride, and undergo addition reactions with unsaturated parts. Inhibits the degradation of PVC molecules.
If you are looking for more details, kindly visit Lianfu.
Explore more:4 Things to Consider When Choosing an Adhesive - GlueGun.com
Lead salts Heat stabilizer
Lead salts are the most commonly used heat stabilizers for PVC, and their dosage can account for more than half of PVC heat stabilizers.
Advantages: Excellent thermal stability, long-term thermal stability, excellent electrical insulation performance, and good weather resistance.
Disadvantages: poor dispersibility, high toxicity, initial coloring, difficulty to obtain transparent products, and difficulty to obtain brightly colored products, lack of lubricity, to generate sulfur and prevent pollution.Metal soap heat stabilizer
The second largest main stabilizer after lead salts in dosage, although its thermal stability is not as good as that of lead salts, it also has lubricity. It is non-toxic except for Cd and Pb, transparent and non-sulfurized except for Pb and Ca. Pollution, so it is widely used in soft PVC, such as non-toxic, transparent and so on. Metal soaps can be metal (lead, barium, cadmium, zinc, calcium, etc.) salts of fatty acids (lauric acid, stearic acid, naphthenic acid, etc.), among which stearate is the most commonly used, and its thermal stability is in the order of four: zinc salt > cadmium salt > lead salt > calcium salt/barium salt. Metal soaps are generally not used alone, and are often used between metal soaps, or in combination with lead salts and organic tin.
Organotin heat stabilizer
Organotin is the most effective and widely used class of heat stabilizers, and its outstanding advantages are: superior heat stability, and good transparency, and most of them are non-toxic. The disadvantage is that the price is high (but the amount added is small, generally only 0.5~2 parts), and another major disadvantage is that most of them have no lubricity. Most organotins are liquid, only a few are solid. It can be used alone or often combined with metal soap.
Organic Antimony heat stabilizer
This is a new type of PVC heat stabilizer. It has excellent initial hue and hue retention, especially when used in low amounts, and its thermal stability is better than that of organotins. It is especially suitable for PVC formulations in twin-screw extruders.
Rare earth stabilizer
The stabilizer is a unique stabilizer developed by our country and is a new type of heat stabilizer. Rare earth elements include 15 lanthanide elements with original serial numbers ranging from 57 to 71 and 17 elements in total, such as yttrium and thorium, which are similar to them.
Liquid composite Heat Stabilizer
The liquid composite heat stabilizer is composed of organometallic soaps, phosphites, hindered phenol antioxidants, and solvents. Organometallic soaps are the main components of liquid complex stabilizers. The main products are liquid barium/cadmium/zinc, barium/cadmium, calcium/zinc, barium/zinc and other composite stabilizers, which have been used in soft PVC calendered film, hard PVC transparent sheet, PVC transparent bottle, etc.
Flame Retardant for PVC
Combustion could occur when a substance is heated to its flammable temperature in the presence of oxygen. Flame retardants are generally designed to provide a particular level of resistance to ignition or flame spread. This is achieved by suppressing oxygen availability, building up of char at the surface, inhibiting the combustion reaction within the flame area, or by other mechanics.
Halogen Flame Retardants for PVC
Chlorinated paraffins is often used as a halogen flame retardant for PVC.
Halogen Free Flame Retardants for PVC
aluminum hydroxide, BX FR IPPP, BX FR TPP are often used as halogen-free flame retardants for PVC.
Impact Modifiers for PVC
Impact Modifiers are substances that increase the durability of molded or extruded plastics, especially those that need to be constantly subjected to impact forces like cold weather. They are added to compounded materials to provide performance features. They provide strength and break resistance to the product for which they are added. They also provide rigidity to the product to prevent it from wrapping or sagging during everyday use. MBS and Acrylic, Silicon import modifiers are used for PVC as impact modifiers. Baoxu Chemical offer impact modifier for PVC as table below
TypeItem namekanekaDowMitsubishiApplicationDosage %MBSBX IM 225M711/732EXL-PC、PC Alloys3-10BX IM 227M722EXL-PC、PC Alloys1-3AcrylicBX IM 365M577EXL-PC、PC/ABS、PBT3-5SiliconeBX IM 330S-PC、PC Alloys3-5Lubricant for PVC
Lubricants are a kind of additive used to improve the processing and appearance of polymers. The function of lubricants is to reduce friction, improve fluidity and mold release during resin or compound processing, and increase the surface smoothness of products. Stearic acid, PE Wax, metal soaps including Mgst, and Znst can be used as lubricant for PVC.
Optical Brightener for PVC
Optical brighteners are used to mask yellow or increase the whiteness of plastics, inks, coatings, paper, and fiber. OB1, KCB, and FP127 can be used in PVC as optical brighteners.
Pigment and Dyes for PVC
Colorants give color to polymers, plastics, coatings, inks, and fiber. Every color we see in our daily life is related to colorants. For industry usage colorants, we offer organic pigments, solvent dyes, fluorescent pigments, and titanium dioxide. In the colorant portfolio, our products are analogs to BASF and other brands.
1. General-Purpose Economic Pigments for PVC
Pigment Yellow 61, pigment yellow 168, pigment orange 13, pigment orange 34, pigment red 48:1, pigment red 48:2, pigment red 48:3, pigment red 57:1, pigment red 57:2.
2. High-performance Pigments for PVC
Pigment Yellow 139, pigment Yellow 183, pigment Yellow 191. pigment orange 43, pigment yellow 151, pigment red 214, pigment red 242.
3. Pigment for outdoor PVC
Pigment Yellow 110, pigment brown 23, pigment brown 25, pigment red 122, pigment blue 15:0, pigment blue 60, pigment green 7, pigment violet 23.
Things to know when selecting pigments for PVC
1. Only pigment, no dyes for PVC.
2. Light Fastness, it is suggested light fastness level above 5 degrees.
3. Immigration, normally use bright color and good migration resistance pigments.
4. Electrical properties, when coloring insulation materials, electrical properties shall take into consideration as pigment could somewhat decrease PVC electrical properties.
5. Heat resistance, for RPVC, mid to high heat resistance is required.
6. Safety, for food and medical usage PVC, no toxic and chemosmotic shall allow.
If you want to learn more, please visit our website PVC Compound Stabilizer.