A device for the influence of ultraviolet radiation on plastic. UV resistance of natural Dematiaceae isolates. A few words about the market
Nylon cable ties are a universal means of fixation. They have found application in many areas, including outdoor work. On outdoors cable clamps are exposed to multiple natural influences: precipitation, winds, summer heat, winter cold, and most importantly - sunlight.
Sun rays are detrimental to screeds; they destroy nylon, make it brittle and reduce elasticity, leading to the loss of the basic consumer properties of the product. In conditions middle zone In Russia, a screed installed on the street can lose 10% of its declared strength in the first 2 weeks. The reason for this is ultraviolet radiation, invisible to the eye electromagnetic waves present in daylight. It is the long-wave UVA and, to a lesser extent, the mid-wave UVB (due to the atmosphere, only 10% reaches the Earth's surface) UV ranges that are responsible for the premature aging of nylon ties.
The negative effects of UV are ubiquitous, even in regions where there are very few sunny days, because... 80% of rays penetrate clouds. The situation is aggravated in northern regions with their long winters, as the permeability of the atmosphere to solar rays increases and snow reflects the rays, thereby doubling UV exposure.
Most suppliers offer the use of a black tie as an option to solve the problem of aging of a nylon clamp due to exposure to sunlight. These ties cost the same as their neutral counterparts white, and the only difference is that to obtain black color finished product A small amount of coal powder or soot is added to the raw material as a coloring pigment. This additive is so insignificant that it is not able to protect the product from UV destruction. Such screeds are commonly called “weather-resistant.” Hoping that such a screed will work conscientiously outdoors is the same as trying to stay warm in cold weather by wearing only underwear.
When installed outdoors, only ties made from UV-stabilized polyamide 66 can reliably withstand loads over a long period of time. Their service life, compared to standard ties when exposed to ultraviolet radiation, differs significantly. A positive effect is achieved by adding special UV stabilizers to the raw materials. The scenario of action of light stabilizers can be different: they can simply absorb (absorb) light, releasing the absorbed energy then in the form of heat; can enter into chemical reactions with products of primary decomposition; can slow down (inhibit) unwanted processes.
IN Lately in society (including the scientific community), the idea of the versatility of plastics and composites, which are expected to solve most problems, began to dominate traditional materials. It is believed that new types of plastics and composites will soon replace not only metals, but also glass, heat-resistant inorganic binders, and building materials. It is quite common to think that by chemically or physicochemically modifying plastics (for example, filling them) impressive results can be achieved.
To a large extent this is true. However, polymers have several “Achilles heels” that cannot be corrected by the chemistry and physics of carbon and its compounds. One of these problems is heat and chemical resistance under the influence of the sun and other radiation. UV stabilizers (UFS) solve this problem.
In the presence of ubiquitous oxygen, the sun's rays have a powerful polymer-decomposing effect. It is clearly visible from plastic products lying outdoors in the sun - first fading and turning white, then cracking and crumbling. They behave no better in the sea: according to ecologists, sea water and the sun turn plastic products into dust, which the fish then confuse with plankton and eat (and we then eat such fish). In general, without UVC and anti-radiation additives (ARA), the polymer is not suitable for many of our usual applications.
Polymers are sensitive to UV radiation, so the service life of products is reduced under the influence of atmospheric factors due to light destruction of the polymer. The use of a light stabilizer concentrate makes it possible to obtain products with high resistance to UV radiation and significantly increase their service life. In addition, the use of UVC prevents color loss, clouding, loss mechanical properties and the formation of cracks in finished products.
Light stabilizers are especially important in products large area exposed to solar or other irradiation - films, sheets. The concept of “UV stabilization” means that the film loses no more than half of its original value over a certain period of time under the influence of sunlight. mechanical strength. UVC, as a rule, contains 20% of “sterically hindered” HALS amines (i.e., amines with a spatial structure that impedes the conformational movements of molecules - this makes it possible to stabilize radicals, etc.) and an antioxidant.
CharacteristicsUV stabilizers
The mechanism of action of light stabilizers (in addition to UVC there are IR stabilizers, etc.) is complex. They can simply absorb (absorb) light, releasing the absorbed energy then in the form of heat; can enter into chemical reactions with products of primary decomposition; can slow down (inhibit) unwanted processes. There are two ways to introduce UVC: surface coating and introduction of polymer into the block. It is believed that it is more expensive to introduce into the block, but the effect of UVC is more durable and reliable. True, the bulk of products (for example, all Chinese) are stabilized by applying a polymer surface layer - usually 40-50 microns. By the way, for a long service life (3–5 years or up to 6–10 seasons) it is not enough to add a lot of UVC; you also need sufficient thickness and a margin of safety. So, for a service life of 3 years, the film must be at least 120 microns thick; for 6–10 seasons, a three-layer material up to 150 microns thick, with a reinforced middle layer, is required.
UVC can be divided into absorbers and stabilizers. Absorbers absorb radiation and convert it into heat (and their effectiveness depends on the thickness of the polymer layer; they are ineffective in very thin films). Stabilizers stabilize the radicals that have already appeared.
In the CIS, forms of polymers are sold, both stabilized (more expensive) and unstabilized (cheaper). This largely explains the lower quality of cheap analogue products from China or other countries. It is clear that polymers (films) with cheaper stabilization will serve less than the established period. For example, stability is often declared for 10 seasons, but the degree to which stability decreases under increased loads is not indicated. As a result, the service life is often half the declared one (i.e. 1–2 years).
A good example of the effect of polymer stabilization is polycarbonate, polyethylene and films. The validity period of polycarbonate in the form of a honeycomb sheet ranges from 2 to 20 years, depending on the degree of stabilization. Due to savings on stabilizers, 90% of manufacturers cannot confirm the stated validity period of PC sheets (usually 10 years). The same with films. For example, instead of 5–10 seasons, agrofilms last only 2–3, which leads to significant losses in the agricultural sector. Polyethylene without UVC does not work for a long time, since it quickly decomposes under UV radiation (pay attention to the appearance and condition of PE products 10–15 years ago). Because of this, for example, polyethylene gas or water pipes are prohibited from being laid on the surface of the earth or even indoors. It is not recommended to process large-scale polymers such as polypropylene, polyformaldehyde, and rubbers without UVC and ARD.
High-quality UVCs, unfortunately, are expensive (most of them are produced by branded Western companies), and because of this, many local manufacturers save on them (they must be added in quantities of 0.1–2, or even 5%). Instead of new GOSTs, specifications and GOSTs from 20 years ago are used in production. For comparison, in the EU standards for stabilizers are updated every 10 years. Each type of UVC has features that should be taken into account when using. For example, amine UVCs lead to darkening of the material, and their use for light-colored products is not recommended. Phenolic UVCs are used for them.
Note that the presence of UVC in polymers, especially films, is not yet taken for granted, which consumers need to remember. Reputable manufacturers focus on the presence of UVC in any product. Thus, Mitsubishi-Engineering Plastics claim that their NOVAREX polycarbonate granules contain a UV stabilizing additive “to cellular polycarbonate could be used for 10 years under increased exposure to sunlight." An example “closer” is the latest April release of the Belarusian enterprise Svetlogorsk-Khimvolokno regarding the implementation new products– PE films with UVC. In addition to explaining why UVC is needed, the company’s press service notes: film with UVC “can have a service life of up to three seasons.” Information from one of the oldest and respected enterprises in the industry (founded in 1964, produces chemical fibers, polyester textile threads, household goods) shows: the consumer must monitor the presence of UVC in the polymer himself.
A few words about the market
The global market for light and thermal stabilizers is approaching the $5 billion mark—more precisely, by 2018 it is expected to reach $4.8 billion. The largest consumer of stabilizers is the construction industry (in 2010, 85% of stabilizers were used for the production of profiles, pipes and cable insulation). Taking into account the growing fashion for siding (whose resistance to light irradiation is the most important condition), the share of UFS in construction can only increase. It is not surprising that the market for light stabilizers is still in high demand - the largest consumer of stabilizers is the Asia-Pacific region, which accounts for up to half of global demand. Next come Western Europe and the USA. Then there are the markets in South America, CIS and Eastern Europe, in the Middle East - where the growth in demand for UVC is ahead of average values, reaching 3.5–4.7% per year.
Since the 70s, the world market has been replenished with offers from leading European companies. Thus, Tinuvin brand UVC has been successfully used for almost half a century, to expand the production of which Ciba built a new plant in 2001 (in 2009 Ciba became part of BASF). The IPG (International Plastic Guide) company tested and brought to market the LightformPP brand UVC concentrate for films and spunbonds (this is a non-woven polypropylene microporous vapor-permeable insulating material). New UVC, in addition to light protection, protects against the destructive effects of pesticides (including sulfur), which is especially important in the agricultural industry. New UFS have already begun to be supplied to the CIS (as a rule, supplies come from Western Europe, USA and South Korea). UVC development is carried out by the Japanese Novarex, Western Clariant, Ampacet, Chemtura, BASF. Recently, Asian producers have become increasingly influential - not only South Korean, but also Chinese.
Dmitry Severin
Resistance of enamels to fading
Conditional light fastness was determined on samples of dark gray enamel RAL 7016 on a REHAU BLITZ PVC profile.
Conditional light fastness paint coating determined in tests in accordance with the standards:
GOST 30973-2002 "Polyvinyl chloride profiles for window and door blocks. Method for determining resistance to climatic influences and assessing durability." clause 7.2, table 1, note. 3.
Determination of conditional light resistance at a radiation intensity of 80±5 W/m2 was controlled by changes in the gloss of coatings and color characteristics. The color characteristics of the coatings were determined using a Spectroton device after wiping the samples with a dry cloth to remove the deposits that had formed.
The change in the color of the samples during the test was judged by the change in color coordinates in the CIE Lab system, calculating ΔE. The results are shown in Table 1.
Table 1 - Change in gloss and color characteristics of coatings
|
Holding time, h |
Loss of gloss, % |
Color coordinate - L |
Color coordinate - a |
Color coordinate -b |
Color change ΔE to reference |
|||
|
Before testing |
After testing |
|||||||
Samples 1 to 4 are considered to have passed the tests.
Data are given for sample No. 4 - 144 hours of UV irradiation, which corresponds to GOST 30973-2002 (40 conditional years):
L = 4.25 norm 5.5; a = 0.48 norm 0.80; b = 1.54 norm 3.5.
Conclusion:
A luminous flux power of up to 80±5 W/m2 leads to a sharp drop in the gloss of coatings by 98% after 36 hours of testing as a result of plaque formation. As testing continues, no further loss of gloss occurs. Lightfastness can be characterized in accordance with GOST 30973-2002 - 40 conditional years.
The color characteristics of the coating lie in permissible limits and comply with GOST 30973-2002 on samples No. 1, No. 2, No. 3, No. 4.
Rigid (unplasticized) polyvinyl chloride was the first to appear on the Russian advertising market, and, despite the increasing range of polymer materials offered every year, it continues to steadily maintain a leading position in some areas of advertising production. This is explained by the presence of a set of properties in PVC that are necessary to solve various problems and satisfy the most stringent requirements for construction materials this type.
PVC is characterized natural resistance to ultraviolet radiation, chemical exposure, mechanical corrosion and contact damage. Over a long period of use on the street does not lose original properties. Does not absorb atmospheric moisture and, accordingly, is not prone to condensation on the surface. Among all other plastics, it has unique fire resistance. Under normal operating conditions it poses no danger to humans or environment. Easily machined, formed (compact material), welded and glued. When applying film, there is no need to think about “pitfalls” - PVC without human intervention will not present “surprises”.
The conditional disadvantages of polyvinyl chloride include:
- short-term resistance of color modifications to sunlight (this does not apply to materials with additional UV stabilization);
- the possible presence of surface release agents in materials of unknown origin that require removal;
- limited frost resistance (up to -20 ° C), which is not always confirmed in practice (subject to all technological rules for the manufacture of structures and their installation, in the absence of significant mechanical loads, PVC behaves stably even at more low temperatures);
- higher than many others polymer materials coefficient of linear thermal expansion, i.e. a wider range of dimensional distortions;
- insufficiently high degree of light transmission of the transparent material (approx. 88%);
- increased requirements for disposal: smoke and combustion products are dangerous to humans and the environment.
Rigid polyvinyl chloride is produced in various modifications only by extrusion. Wide range of PVC, including sheets:
- compact and foamed;
- with glossy and matte surface;
- white, colored, transparent and translucent;
- flat and embossed;
- standard design and increased bending strength,
allows the use of this material in almost any area of advertising production.
Tatiana Dementieva
process engineer
Acrylic in architecture
Acrylic glass is used to create the most beautiful architectural structures- transparent roofing, facades, road barriers, awnings, canopies, gazebos. All these structures are operated outdoors under constant exposure to solar radiation. A reasonable question arises: will acrylic structures be able to withstand the “onslaught” of the rays of the scorching sun, while maintaining excellent performance characteristics, shine, and transparency? We hasten to please you: there is no reason to worry. Acrylic structures can be safely used outdoors under constant exposure to ultraviolet radiation, even in hot countries.
Comparison of acrylic with other plastics in terms of resistance to UV radiation
Let's try to compare acrylic with other plastics. Today, a large number of different transparent plastics are used for the manufacture of facade and roof glazing and fencing structures. At first glance, they are no different from acrylic. But synthetic materials, similar to acrylic in their visual characteristics, lose their visual appeal after just a few years of operation under direct sun rays. No additional coatings or films can protect low-quality plastic from ultraviolet radiation for a long time. The material remains sensitive to UV rays, and, alas, there is no need to talk about the reliability of all kinds of surface coatings. Protection in the form of films and varnishes cracks and peels off over time. It is not surprising that the guarantee against yellowing of such materials does not exceed several years. Acrylic glass from the Plexiglas brand manifests itself in a completely different way. The material has natural protective properties, therefore, does not lose its excellent characteristics for at least three decades.
How does the technology for protecting acrylic from sunlight work?
Plexiglas is UV resistant unique technology comprehensive protection Naturally UV Stable. Protection is formed not only on the surface, but throughout the entire structure of the material at the molecular level. Plexiglas manufacturer Plexiglas provides a 30-year guarantee against yellowing and clouding of the surface when constant operation on the street. This guarantee applies to transparent, colorless sheets, pipes, blocks, rods, corrugated and ribbed slabs of Plexiglas brand acrylic glass. Awnings, roofing coverings, transparent acrylic facades, gazebos, fences and other plexiglass products do not acquire an unpleasant yellow tint.
The diagram shows changes in the light transmittance index of acrylic over warranty period operation in various climatic zones. We see that the light transmission of the material decreases slightly, but these are minimal changes, invisible to the naked eye. A decrease in the light transmittance index by several percent can only be determined using special equipment. Visually, acrylic remains pristinely transparent and shiny.
On the graph you can trace the dynamics of changes in the light transmittance of acrylic in comparison with ordinary glass and other plastics. Firstly, the light transmission of acrylic in its original state is higher. This is the most transparent material of the plastics known today. Over time, the difference becomes more noticeable: low-quality materials begin to darken and fade, but the light transmission of acrylic remains at the same level. None of the known plastics, except acrylic, can transmit 90% of light after thirty years of operation under the sun. This is why acrylic is preferred modern designers and architects when creating their best projects.
When we mention light transmission, we are talking about the safe spectrum of ultraviolet rays. Dangerous part of the solar radiation spectrum acrylic glass delays. For example, in a house under an acrylic roof or on an airplane with acrylic windows, people are protected by reliable glazing. To clarify, let's look at the nature of ultraviolet radiation. The spectrum is divided into short-wave, medium-wave and long-wave radiation. Each type of radiation has different effects on the world. The highest energy radiation with the shortest wavelength absorbed ozone layer planet, can damage DNA molecules. Medium wave - with prolonged exposure causes skin burns and inhibits basic body functions. The safest and even useful is long-wave radiation. Only part of the dangerous medium-wave radiation and the entire long-wave spectrum reaches our planet. Acrylic transmits the beneficial spectrum of UV radiation, while blocking dangerous rays. This is a very important advantage of the material. Glazing the house allows you to retain maximum light in the room, protecting people from negative impact ultraviolet.
