German:
Stabilisatoren
Spanish:
estabilizadores
French:
stabilisateurs
Italian:
stabilizzanti (stabilizzatori)
Russian:
стабилизаторы
Arabic:
المثبتات
Chinese:
安定面 (稳定剂)
Japanese:
スタビライザー
General overview of stabilizers
Stabilizers for polymers are additives which have to be added individually or in combinations to most polymers and elastomers. They enable safe processing, protect plastics against weathering, retard deterioration, and ensure that plastic products can be used for a long time. Heat stabilizers protect against the effects of heat, light stabilizers (UV absorbers) against the effects of light. Some additives act both against the effects of light and heat and against impacts of oxygen (for example phenols, see Antioxidants). Conversely, some heat stabilizers can act as anti¬oxidants, e.g. alkyltin mercaptides.
Stabilizers have an important influence on the physical properties and costs of plastic blends. Usually stabilizers are added to polymers during production. The trend is towards fluid systems, pellets, and increased use of masterbatches. There are monofunctional, bifunctional, and polyfunctional stabilizers. They are delivered in specific blends depending on the application. Metal soaps, metallic salts, and organic metal compounds are the main constituents. The phasing out of cadmium and lead changes the market in favor of other stabilizer systems.
Heat stabilizers are mostly based on metals, mainly lead, barium, calcium, magne¬sium, zinc, and tin. The main groups are lead stabilizers, barium-zinc stabilizers, calcium-zinc stabilizers, and tin stabilizers. They are usually combined with synergistic co-stabilizers, i.e., with organic materials like polyols or epoxy esters. Since the use of heavy-metal containing additives is increasingly limited or prohibited, there is a trend to develop organic compounds. Heavy-metal-bearing stabilizers are replaced by more complex (and usually more expensive) formulations based on metal soaps, organic co-stabilizers (polyols and phosphites), and lubricants, especially calcium-zinc systems. Lead and cadmium stabilizers are (or were) exclusively used for PVC products.
Light stabilizers reduce or prevent reactions caused by UV radiation or visible light. Some light stabilizers do not only act as light filters, but are multifunctional additives. Mostly blends of different light stabilizers are used in concentrations of 0.2% to 1%, usually together with other additives. Generally, light stabilizers only act properly if the polymers are not damaged by thermal oxidation during processing. Therefore, effective processing stability thanks to the use of heat stabilizers is very important when manufacturing durable plastic items. Light fastness of final products can also depend on the pigments used. Usually, inorganic pigments offer better resistance than organic pigments.
The global market for stabilizers will achieve revenues of almost US$4.8 billion by 2018. Demand for stabilizers depends on the development of the plastics industry, especially the field of polyvinyl chloride (PVC). As heat stabilizers are mainly used in PVC products used in construction, the construction industry in individual countries has a huge impact on demand. Most important sales markets currently include profiles, pipes, and cables - more than 85% of all stabilizers are used in these fields.
Comprehensive information on pigments - their characteristics, application areas, market data, and environmental aspects - can be found in Market Study: Stabilizers, by Ceresana Research.
Important types of stabilisers:
German:
Metallseifen
Spanish:
jabón de metal
French:
savon métallique
Italian:
sapone metallico
Russian:
металл мыло
Arabic:
المعادن والصابون
Chinese:
金属皂
Japanese:
ミッシュメタル
Solid metal salts are often called "soaps". Combinations of metal carboxylates (solid salts) and a series of lubricants and co-stabilizers (e.g. phenolic antioxidants, organophosphites or zeolites) belong to this group of stabilizers. Mainly calcium-zinc (Ca-Zn) and barium-zinc stabilizers (Ba-Zn) are used as metal soaps, e.g. as stearates. Other possibilities are e.g. blends with magnesium, oleates, or p-tert-butyl-benzoates. Usually they are fluid (especially for soft PVC-P, e.g., in garden hoses or toys). For rigid PVC-U, solid formes are produced, too.
Structure and function of barium-zinc and calcium-zinc stabilizers are similar to the cadmium stabilizers formerly used. Therefore, they were increasingly used as substitutes since the 1980s. Special co-stabilizers had to be developed, especially for durable products that are used outdoors. Today, Ca-Zn systems have replaced lead in all important application areas (PVC-U and PVC-P).
Calcium-zinc stabilizers are usually based on metal carboxylates. Their zinc content is normally between 0.5% and 3% by weight, in automotive cables almost up to 10%. In order to improve of their properties - mainly heat resistance, color stability, and weathering resistance -, they are blended with other elements (e.g., aluminum or magnesium), lubricants (e.g., paraffines, polyethylene waxes, or ester waxes), and co-stabilizers (e.g., polyols, epoxy soybean oil, antioxidants, or organic phosphites). These more complex stabilizers are more expensive than simple metal soaps, but they can be used in more challenging application areas, e.g., for cable protection or window profiles. Calcium-zinc stabilizers in PVC offer high clarity, good mechanical and electrical properties, and excellent organoleptic characteristics. Their light and weather fastness is superior to lead stabilizers; they retard chalking. Consequently, they are used in many applications ranging from blood bags, toys, and food films to water pipes. Calcium-zinc stabilizers and tested co-stabilizers are regarded as nontoxic and are approved for food contact applications. They can replace most other stabilizers, e.g. lead or barium-zinc. If barium or cadmium is replaced by calcium, the loss of stability must be compensated by higher concentrations of certain co-stabilizers - e.g. Cn-Zn systems need twice as many phosphites. As compared to lead systems, stabilizers based on calcium are more product specific. They often have to be tailor-made for certain applications. Calcium stabilizers without zinc are also available. In these stabilizers, organic molecules act as co-stabilizers.
Barium-zinc stabilizers are predominantly fluid metal soaps. In general, they are used in the form of carboxylates. They are equipped with the same co-stabilizers as Ca-Zn systems and can be optimized in regard to properties like clarity, weather fastness, color stability, durability, suitability for white pigments, low migration, or low odor generation. Sometimes solvents are added. Barium-zinc stabilizers are used for paste PVC. They are the main stabilizer type for flexible films, e.g. membranes, floor coverings, and shoes. However, they are increasingly replaced by Ca-Zn products. Special fluid Ba-Zn, Ca-Zn and Potassium-Zn soaps are used as activators ("kickers") for blowing agents, which are needed to produce foamed layers in plastisol applications. Barium compounds were used to replace cadmium stabilizers, although they are harmful to health and not permitted for food contact, toys, or medical applications. Some co-stabilizers are also regarded as toxic and environmentally harmful.
Ultrafine zinc oxide particles are also used as UV absorbers. As they are smaller than the wave length of visible light, they have only minimal effect on the transparency of polymers. According to producers, these particles do not migrate or degrade, they offer longer UV protection than conventional organic UV absorbers and are admitted for food applications.
Market Study: Stabilizers from Ceresana Research offers comprehensive information on the production, consumption, and price development of stabilizers, divided among the different world regions.
Manufacturers of metal soaps:
(-> for more information see Market Study: Stabilizers from Ceresana Research)
German:
Zinn-Stabilisatoren
Spanish:
estabilizadores de estaño
French:
stabilisateurs d'étain
Italian:
stabilizzanti a base di stagno
Russian:
стабилизаторы на основе олова
Arabic:
مثبتات القصدير
Chinese:
锡稳定剂
Japanese:
スズ安定剤
Tin stabilizers are predominantly organotin compounds. In these blends of mono- and dialkyl-tin salts, the respective shares can be varied according to application. Physical, chemical, and toxicological properties depend on the respective organic groups that are connected with the tin atoms by carbon, sulphur, or oxygen. Mainly sulphur-containing products are among the most effective heat stabilizers. Their typical odor is usually only a nuisance in soft final products. Organotin compounds without sulphur are odorless and offer good light and weather resistance. Tin stabilizers can replace lead-based products.
The most common tin stabilizers are produced by reaction of mono and dialkyl chlorides with mercaptoesters. They are not to be confused with trisubstituted organotin compounds used as biocides for agriculture (triphenyltin acetate, triphenyltin hydroxide). Trialkyltin compounds (Tributyltin / TBT) that are especially toxic for aquatic organisms are used in antifouling paints for ships.
There are two main types of stabilizers with mono or disubstituted organotin compounds. They are also available in blends in order to combine their properties:
• Dicarboxylic acid half esters are stabilizers with tin-oxygen compounds and are also called maleates or carboxylates. They are mainly used if good weather and light fastness and low odor generation are requested. Application examples are transparent panels and walls for greenhouses. Octyltin maleates are admitted e.g. for packaging of sweets.
• Thioacid half esters are stabilizers with tin-sulphur compounds like e.g. mercaptides. They enable the production of clear, rigid PVC articles. They are easier to process and more effective heat stabilizers than carboxylates. On the other hand, they usually develop a characteristic odor and offer only moderate light fastness (though light stability can be improved by using titanium dioxide, at least in light colored products). The strongest - and most widely used - compounds of this group are derivatives of thioglycolate esters.
Tin compounds are the most commonly used heat stabilizers in North America. Tin stabilizers based on methyl groups are used for practically all rigid PVC applications in the U.S. Stabilizers with butyl or octyl groups, which offer very good heat resistance and color stability, are more widely used in Europe. These types allow the production of rigid, transparent products. In Europe, tin stabilizers are classified as toxic, and there are discussions about whether several types should be prohibited.
Different countries approve some organic tin stabilizers for food contact applications, especially types with methyl, octyl and lauryl groups. For instance, tin stabilizers are used in drinking water pipes in countries where lead is prohibited for this application - especially in the U.S., France, and Belgium. Butyl tin is used in technical applications. The main field of application for tin stabilizers is PVC products: rigid packaging films (e.g. blister packages for medical drugs), bottles, technical items, injection molded fittings, and transparent panels for construction applications.
Further information on manufacture and consumption of tin stabilizers and other stabilizers can be found in Market Study: Stabilizers, from Ceresana Research.
Manufacturers of tin stabilizers:
(-> for more information see Market Study: Stabilizers from Ceresana Research)
Hindered Amine Light Stabilizers (HALS, also HAS)
German:
HALS
Spanish:
estabilizadores obstaculizados de la luz de amina
French:
stabilisateurs gênés de lumière d'amine
Italian:
stabilizzanti alla luce a base di ammine inibite
Russian:
помешанные стабилизаторы света амина
Arabic:
أعاق أمين الخفيفة المثبتات
Chinese:
受阻胺光稳定剂
Japanese:
ヒンダードアミン系光安定剤
HALS are the commercially most important light stabilizers. HALS are sterically hindered piperidines. They capture very efficiently free radicals produced by UV rays (therefore they are also called "scavengers") and deactivate hydroperoxides. They protect plastic without directly absorbing UV radiation. Their effectiveness does not depend on the material's thickness, i.e., they prevent reactions of aggressive photo-oxidation products also at the surfaces of plastic products. This is of particular importance for fibers with huge surfaces at low volumes. HALS already attain high stabilization at relatively low doses. They have a long life span because they regenerate in a cyclical process. HALS with high molecular weight are often blended with HALS of low molecular weight in order to get a good balance of UV stability, heat resistance, and compatibility with the substrate. Since HALS are transparent in UV light, other UV absorbers are often added, which may act synergistically.
Derivates of 2,2,6,6-tetramethyl piperidine were initially used as antioxidants and were later discovered to be very effective UV stabilizers. Nowadays, there are at least 40 different monomeric, oligomeric, and polymeric versions. Oxidation products of HALS, like hydroxylamines and hydroxylamine ether, also obstruct photo-oxidation. HALS can be used alone in polyolefins, especially in polypropylene and polyethylene HDPE. Styrene polymeres and PVC-P often need additional stabilizers, e.g. benzotriazoles. In the quite light fast acrylic polymers, e.g. PMMA, blends of HALS and UV absorbers are used to avoid discolorations.
A variant called NOR HALS is used in PVC. NOR HALS are based on alkyloxyamines. In contrast to conventional, basic HALS, they can be used for agricultural films made of polyethylene or polypropylene because they hardly react with acid derivatives from agrochemicals and are more resistant to pesticides. Technical polymers or other materials may be replaced by polyolefins due to the newest HALS light stabilizers. NOR HALS are usually more expensive than blends of nickel quenchers and UV absorbers, which are also able to stabilize agricultural films.
Information on production and consumption of HALS is provided by Market Study: Stabilizers, from Ceresana Research.
Manufacturers of HALS:
(-> for more information see Market Study: Stabilizers from Ceresana Research)
Last revision: 09. July 11
