UV resistance of natural Dematiaceae isolates. UV stabilizers are a necessary additive to polymer materials. They are not resistant to UV radiation.
Having collected a significant collection of dark-colored hyphomycetes isolated from different habitats, we began to study the relationship of natural fungal isolates to UV radiation. This study made it possible to identify differences in UV resistance among widely distributed species and genera of the family Dematiaceae in soil, to determine the distribution of this trait within each biocenosis, its taxonomic and ecological significance.
We studied the resistance to UV rays (254 nm, dose intensity 3.2 J/m2) of 291 fungal cultures isolated from meadow and floodplain-meadow (21 species of 11 genera), high-mountain (25 species of 18 genera) and saline (30 species 19 genera) soils. When studying the UV resistance of Dematiaceae crops isolated from flat saline soils in the south of the Ukrainian SSR, we proceeded from the assumption that with increasing unfavorable living conditions due to soil salinity, a greater number of resistant species of dark-colored hyphomycetes would accumulate in it than in other soils. In some cases, it was impossible to determine UV resistance due to the loss or sporadic sporulation of species.
We studied natural isolates of dark-colored hyphomycetes; therefore, each sample was characterized by an unequal number of cultures. For some rare species, the sample size did not allow for appropriate statistical processing.
The widespread and frequently occurring genus Cladosporium is represented by the largest number of strains (131), in contrast to the genera Diplorhinotrichum, Haplographium, Phialophora, etc., isolated only in isolated cases.
We conditionally divided the studied mushrooms into highly resistant, resistant, sensitive and highly sensitive. Highly resistant and resistant were those whose survival rate after 2-hour exposure to UV rays was more than 10% and from 1 to 10%, respectively. We classified species whose survival rate ranged from 0.01 to 1% and from 0.01% and below as sensitive and highly sensitive.
Large fluctuations in the UV resistance of the studied dark-colored hyphomycetes were revealed - from 40% or more to 0.001%, i.e., within five orders of magnitude. These fluctuations are somewhat smaller at the level of genus (2-3 orders) and species (1-2 orders), which is consistent with the results obtained on bacteria and tissue cultures of plants and animals (Samoilova, 1967; Zhestyanikov, 1968).
Of the 54 studied species of the family Dematiaceae, Helminthosporium turcicum, Hormiscium stilbosporum, Curvularia tetramera, C. lunata, Dendryphium macrosporioides, Heterosporium sp., Alternaria tenuis, and a significant part of Stemphylium sarciniforme strains are highly resistant to long-term UV irradiation at 254 nm. All of them are distinguished by intensely pigmented, rigid cell walls and, with the exception of Dendryphium macrosporioides, Heterosporium sp. and Hormiscium stilbosporum, belong to the Didimosporae and Phragmosporae groups of the Dematiaceae family, characterized by large multicellular conidia.
Much larger number species are resistant to UV rays. These include species of the genera Alternaria, Stemphylium, Curvularia, Helminthosporium, Bispora, Dendryphion, Rhinocladium, Chrysosporium, Trichocladium, Stachybotrys, Humicola. The distinctive features of this group, as well as the previous one, are large conidia with rigid, intensely pigmented walls. Among them, fungi of the Didimosporae and Phragmosporae groups also occupied a significant place: Curvularia, Helminthosporium, Alternaria, Stemphylium, Dendryphion.
23 species of dark-colored hyphomycetes are classified as UV-sensitive: Oidiodendron, Scolecobasidium, Cladosporium, Trichosporium, Haplographium, Periconia, Humicola fusco-atra, Scytalidium sp., Alternaria dianthicola, Monodyctis sp., Peyronella sp., Curvularia pallescnes, etc. Noteworthy Please note that the species A. dianthicola and C. pallescens, whose conidia are less pigmented, are sensitive to UV rays, although other species of these genera are resistant and even highly resistant.
According to the accepted division, species of the genus Cladosporium, which is widespread and represented in our studies by the largest number of strains, are classified as sensitive (C. linicola, C. hordei, C. macrocarpum, C. atroseptum. C. brevi-compactum var. tabacinum) and highly sensitive (C . elegantulum, C. transchelii, C. transchelii var. semenicola, C. griseo-olivaceum).
Species of the genus Cladosporium belonging to the first group were distinguished by rather dense, intensely pigmented, rough cell walls, in contrast to the second group of species, the cell walls of which were thinner and less pigmented. Sensitive species, the survival rate of which after irradiation with a dose of 408 J/m 2 was less than 0.01%, were Diplorhinotrichum sp., Phialophora sp., Chloridium apiculatum, etc. Large-spored dark-colored hyphomycetes were absent in this group. Species highly sensitive to UV irradiation had small, weakly pigmented or almost colorless conidia.
In some species of Dematiaceae, the morphology of conidia formed after irradiation with a dose of 800 J/m 2 was studied. Conidia of Cladosporium transchelii, C. hordei, C. elegantulum and C. brevi-compactum formed after irradiation are usually larger than those of non-irradiated species. This tendency was especially clear on basal conidia. Noticeable changes in the morphology of conidia were also observed in large-spored, UV-resistant species Curvularia geniculata, Alternaria alternata, Trichocladium opacum, Helminthosporium turcicum; they were detected only after irradiation with high doses of UV rays of the order of 10 3 J/m 2. At the same time, the conidia of Curvularia geniculata noticeably lengthened and became almost straight; in the conidia of Alternaria alternata, the number of longitudinal partitions decreased until they completely disappeared, and they themselves became larger than the control ones. On the contrary, the conidia of N. turcicum became smaller, the number of septa in them decreased, and sometimes the septa became curved. In the conidia of Trichocladium opacum, the appearance of individual, unusually swollen cells was observed. Such changes in morphology indicate significant disturbances in the processes of growth and division in irradiated fungi.
The study of natural isolates of fungi of the family Dematiaceae confirmed a certain dependence of UV resistance on the size of conidia and the pigmentation of their membranes. As a rule, large conidia are more stable than small ones. It should be noted that the indicator we selected - survival - of melanin-containing fungi after irradiation with a dose of 408 J/m 2 indicates high stability a group of fungi as a whole, superior to that of the unique microorganisms Micrococcus radiodurans (Moseley, Copland, 1975) and Micrococcus radiophilus (Lewis, Kumita, 1972). It is quite obvious that the nature of this phenomenon requires further study with the involvement of highly resistant and resistant species of the family Dematiaceae.
We studied the distribution of the UV resistance trait in dark-colored fungi isolated from floodplain-meadow, saline and high-mountain soils, which was depicted graphically. The resulting curves resembled normal distribution curves (Lakin, 1973). The survival rate of the majority (41.1 and 45.8%) of crops isolated from meadow and saline soils of Ukraine, respectively, after a dose of 408 J/m 2 (2-hour exposure) was 0.02-0.19%, and resistance to this factor was distributed within 6 orders of magnitude. Consequently, the assumption about increased resistance to UV irradiation of dark-colored hyphomycetes from saline soils was not confirmed.
The UV resistance of high-mountain species of the family Dematiaceae was noticeably different from that described above, which was reflected in the change in the position of the peak of the curve and the range of the distribution.
For 34.4% of cultures, survival rate was 0.2-1.9%. The survival rate of 39.7% of isolates exceeded 2%, i.e., the distribution curve of the UV resistance trait is shifted towards increased resistance to UV irradiation. The distribution range for this property did not exceed four orders of magnitude.
In connection with the identified differences in the distribution of the UV-resistance trait in lowland and high-mountain species and genera of the family Dematiaceae, it seemed appropriate to check why they occur: due to the predominant occurrence of highly resistant and UV-resistant species of dark-colored hyphomycetes in mountain soils, or is there an increased resistance to UV radiation of high-mountain strains of the same species or genus compared to lowland strains. To prove the latter, a comparison was made of crops of the family Dematiaceae isolated on the surface of lowland and high-mountain soils, as well as from the surface (0-2 cm) and deep (30-35 cm) horizons of lowland meadow soils. It is obvious that such mushrooms are in extremely unequal conditions. The samples we used made it possible to analyze, based on UV resistance, 5 common genera of the family Dematiaceae, isolated on the surface of lowland and high-mountain soils. Only strains isolated from high mountain soils of species of the genus Cladosporium and Alternaria are significantly more resistant than strains isolated from lowland soils. On the contrary, the UV resistance of strains isolated from lowland soils was significantly higher than that from high mountain soils. Consequently, differences in relation to UV rays in the mycoflora of areas with increased insolation (high mountain soils) are determined not only by the predominant occurrence of resistant genera and species of Dematiaceae, but also by their possible adaptation to such conditions. The last point obviously has a particular meaning.
A comparison of the UV resistance of cultures of the most common genera of dark-colored hyphomycetes isolated from surface, exposed to light, and deep soil horizons showed the absence of statistically significant differences between them. The range of variation in the UV resistance trait in natural isolates of widespread Dematiaceae species was for the most part identical in lowland and highland isolates and did not exceed two orders of magnitude. Wide variability in this trait at the species level ensures the survival of a stable part of the species population in environmentally unfavorable conditions for this factor.
The conducted studies confirmed the exceptionally high UV resistance of the species Stemphylium ilicis, S. sarciniforme, Dicoccum asperum, Humicola grisea, Curvularia geniculata, Helminthosporium bondarzewi, revealed in the experiment, in which, after an irradiation dose of about 1.2-1.5 ∙ 10 3 J/m 2 to 8-50% of conidia remained alive.
The next task was to study the resistance of some species of the family Dematiaceae to biologically extreme doses of UV radiation and high-intensity artificial sunlight (ASL) (Zhdanova et al. 1978, 1981).
We irradiated a monolayer of dry conidia on a gelatin substrate according to Lee’s method, modified by us (Zhdanova, Vasilevskaya, 1981), and obtained comparable, statistically reliable results. The source of UV radiation was a DRSh-1000 lamp with a UFS-1 light filter, transmitting UV rays of 200-400 nm. The light flux intensity was 200 J/m 2 ∙ s. It turned out that Stemphylium ilicis, Cladosporium transchelii and especially its mutant Ch-1 are highly resistant to this effect.
Thus, the survival rate of S. ilicis after a dose of 1 ∙ 10 5 J/m 2 was 5%. 5% survival for the Ch-1 mutant, C. transchelii, K-1 and BM mutants was observed after doses of 7.0 ∙ 10 4 ; 2.6 ∙ 10 4 ; 1.3 ∙ 10 4 and 220 J/m 2, respectively. Graphically, the death of irradiated dark-colored conidia was described by a complex exponential curve with an extensive plateau, in contrast to the survival of the BM mutant, which obeyed an exponential dependence.
In addition, we tested the resistance of melanin-containing fungi to high-intensity ASCs. The radiation source was a solar illuminator (OS - 78) based on a DKsR-3000 xenon lamp, providing radiation in the wavelength range 200-2500 nm with a spectral energy distribution close to that of the sun. In this case, the share of energy in the UV region was 10-12% of the total radiation flux. Irradiation was carried out in air or under vacuum conditions (106.4 μPa). The radiation intensity in air was 700 J/m 2 ∙ s and in vacuum - 1400 J/m 2 ∙ s (0.5 and 1 solar dose, respectively). One solar dose (solar constant) is the amount of total flux of solar radiation outside earth's atmosphere at an average distance the Earth - the Sun falling on 1 cm 2 of the surface in 1 s. Specific irradiance was measured using a special technique at the sample position using a lux meter 10-16 with an additional neutral density filter. Each strain was irradiated with at least 8-15 successively increasing doses of radiation. The irradiation time varied from 1 minute to 12 days. Resistance to ASC was assessed by the survival rate of fungal conidia (the number of macrocolonies formed) in relation to the non-irradiated control, taken as 100%. A total of 14 species of 12 genera of the family Dematiaceae were tested, of which 5 species were studied in more detail.
The resistance of cultures of C. transchelii and its mutants to ASC depended on the degree of their pigmentation. Graphically, it was described by a complex exponential curve with an extensive plateau of resistance. The LD value of 99.99 upon irradiation in air for mutant Ch-1 was 5.5 ∙ 10 7 J/m 2 , the original culture of C. transchelii - 1.5 ∙ 10 7 J/m 2 , light-colored mutants K-1 and BM - 7.5 ∙ 10 6 and 8.4 ∙ 10 5 J/m 2, respectively. Irradiation of the Ch-1 mutant under vacuum conditions turned out to be more favorable: the resistance of the fungus noticeably increased (LD 99.99 - 2.4 ∙ 10 8 J/m 2), the type of dose survival curve changed (multicomponent curve). For other strains, such irradiation was more destructive.
When comparing the resistance to UV rays and high-intensity ASC of cultures of C. transchelii and its mutants, many similarities were found, despite the fact that the effect of ASC was studied on “dry” conidia, and an aqueous suspension of spores was irradiated with UV rays. In both cases, a direct dependence of fungal resistance on the content of PC melanin pigment in the cell membrane was found. A comparison of these properties indicates the participation of the pigment in the resistance of fungi to ASC. The mechanism proposed below for the photoprotective effect of melanin pigment makes it possible to explain the long-term resistance of melanin-containing fungi to total doses of UV rays and ASCs.
The next stage of our work was to find cultures of melanin-containing fungi that are more resistant to this factor. They turned out to be species of the genus Stemphylium, and the resistance of S. ilicis and S. sarciniforme cultures in the air is approximately the same, extremely high and described by multicomponent curves. The maximum radiation dose of 3.3 ∙ 10 8 J/m 2 for the mentioned crops corresponded to the LD value of 99. In a vacuum, with more intense irradiation, the survival rate of Stemphylium ilicis cultures was slightly greater than that of S. sarciniforme (LD 99 is 8.6 ∙ 10 8 and 5.2 ∙ 10 8 J/m 2, respectively), i.e., their survival almost the same and was also described by multicomponent curves with an extensive plateau at the survival level of 10 and 5%.
Thus, a unique resistance of a number of representatives of the Dematiaceae family (S. ilicis, S. sarciniforme, mutant C. transchelii Ch-1) to prolonged high-intensity irradiation was discovered. To compare the results obtained with previously known ones, we reduced by an order of magnitude the values of sublethal doses received for our objects, since UV rays (200-400 nm) of the OS-78 installation amounted to 10% of its light flux. Consequently, the survival rate of the order of 10 6 -10 7 J/m 2 in our experiments is 2-3 orders of magnitude higher than that known for highly resistant microorganisms (Hall, 1975).
In light of ideas about the mechanism of the photoprotective action of melanin pigment (Zhdanova et al., 1978), the interaction of the pigment with light quanta led to its photo-oxidation in the fungal cell and subsequently to stabilization of the process due to reversible phototransfer of electrons. In an argon atmosphere and in a vacuum (13.3 m/Pa), the nature of the photochemical reaction of the melanin pigment remained the same, but photooxidation was less pronounced. The increase in UV resistance of conidia of dark-colored hyphomycetes in a vacuum cannot be associated with the oxygen effect, which is absent when “dry” samples are irradiated. Apparently, in our case, vacuum conditions contributed to a decrease in the level of photooxidation of melanin pigment, which is responsible for the rapid death of the cell population in the first minutes of irradiation.
Thus, a study of the resistance to UV radiation of about 300 cultures of representatives of the family Dematiaceae showed significant UV resistance to this effect of melanin-containing fungi. Within the family, heterogeneity of species on this basis has been established. UV resistance presumably depends on the thickness and compactness of the arrangement of melanin granules in the cell wall of the fungus. The resistance of a number of dark-colored species to sources of high-power UV rays (DRSh-1000 and DKsR-3000 lamps) was tested and an extremely stable group of species was identified, significantly superior in this property to such types of microorganisms as Micrococcus radiodurans and M. radiophilus. A unique pattern of survival of dark-colored hyphomycetes has been established according to the type of two- and multicomponent curves that were first described by us.
A study was carried out of the distribution of the trait of resistance to UV rays of dark-colored hyphomycetes in the high-mountain soils of the Pamirs and Pamir-Alai and in meadow soils Ukraine. In both cases it resembles a normal distribution, but the mycoflora of high-mountain soils was clearly dominated by UV-resistant species of the family Dematiaceae. This indicates that solar insolation causes profound changes in the mycoflora of the surface soil horizons.
Most oils and sealants are used with equal success for both interior decoration, and for external. True, for this they must have a certain set of properties, for example, such as moisture resistance, thermal insulation and resistance to ultraviolet radiation.
All these criteria must be met without fail, because climatic conditions Ours are unpredictable and constantly changing. It may be sunny in the morning, but by lunchtime clouds will appear and heavy rain will begin.
With all of the above in mind, experts advise choosing UV-resistant oils and sealants.
Why is a filter needed?
It would seem, why add a UV filter when you can use silicone or polyurethane sealant for outdoor use? But all these means have certain differences, which does not allow them to be used in absolutely all cases. For example, you can easily restore a seam if acrylic sealant was used, which cannot be said about silicone.
In addition, silicone sealant is highly aggressive to metal surfaces, which cannot be said about acrylic ones. One more distinctive feature with a minus sign silicone sealants they are not environmentally friendly. They contain solvents that are hazardous to health. This is why some acrylic sealants have begun to use a UV filter to expand their range of applications.
Ultraviolet radiation is the main cause of destruction of most polymer materials. Given the fact that not all sealants are UV resistant, you need to be extremely careful when choosing a sealant or oil.
Substances resistant to ultraviolet radiation
There are already a number of UV resistant sealants on the sealants and coatings market. These include silicone and polyurethane.
Silicone sealants
The advantages of silicone sealants include high adhesion, elasticity (up to 400%), the ability to paint the surface after hardening and resistance to ultraviolet radiation. However, they also have many disadvantages: not environmentally friendly, aggressive towards metal structures and the impossibility of suture restoration.
Polyurethane
They have even greater elasticity than silicone (up to 1000%). Frost-resistant: they can be applied to surfaces at air temperatures down to −10 C°. Polyurethane sealants are durable and, of course, UV resistant.
The disadvantages include high adhesion not to all materials (does not interact well with plastic). The used material is very difficult and expensive to recycle. Polyurethane sealant does not interact well with humid environments.
Acrylic sealants with UV filter
Acrylic sealants have many advantages, including high adhesion to all materials, the possibility of seam restoration and elasticity (up to 200%). But among all these benefits, one thing is missing: resistance to ultraviolet rays.
Thanks to this UV filter, now acrylic sealants can compete with other types of sealing agents and facilitate consumer choice in certain cases.
Oils with UV filter
Colorless coating agent wooden surfaces has high and reliable protection from ultraviolet radiation. Oils with a UV filter are successfully used for outdoor work, allowing the material to retain all its essential positive properties, despite external influences.
This type of oil allows you to slightly delay the next planned coating of the surface with oil. The interval between restorations is reduced by 1.5–2 times.
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 everywhere, even in regions where there are very few sunny days, because... 80% of rays penetrate clouds. The situation is aggravated in the northern regions with their long winters, since the permeability of the atmosphere for sun rays increases, and the snow reflects the rays, thereby doubling the 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 screeds cost the same as their neutral white counterparts, and the only difference is that to obtain a black color in the 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.
What it is?
Why is UV printing so good?
Why pay more?
The principle of ultraviolet printing
Ultraviolet printing (UV printing) is a type of printing using UV-curable ink by inkjet printing directly onto the material. When exposed to UV radiation of a certain wavelength, such ink instantly polymerizes and turns into a solid state. Since the ink is not absorbed into the material and does not spread over the surface, this allows you to create bright and rich images.
UV ink has a matte surface after polymerization, so it is necessary to additional processing varnish. But if you use glass printing with reverse side, then the images turn out juicy and glossy. Thus, the image can be applied to any surface. Glossy surfaces are treated with a special solution before application, which helps the ink adhere to the surface of the material. Even without varnish, after polymerization, the ink stops evaporating harmful solvents and becomes harmless to humans.
When printing on transparent materials(glass, plexiglass) with white color we get several layers: base (glass) + primer (for adhesion to the surface) + colored UV paints + white UV paint + white protective film security.
What are the advantages of printing with ultraviolet ink?
- Durability
UV ink is highly resistant to impact environment. In addition, they are more durable - they do not fade in the sun and do not dissolve in water and solvent. - Environmental friendliness
The components that make up UV inks, unlike solvent inks, do not contain resin-based solvents. In the process of working with ink, harmful effects on the atmosphere and humans are practically eliminated. This allows the use of ultraviolet printing in areas with high sanitary requirements(schools, kindergartens, hospitals) and in the interior. - Big choice material and surfaces
UV ink is not absorbed into the material, but remains on the surface. That is why you can print on any materials: flexible or hard, with smooth or uneven surfaces. - Bright and rich colors
Because UV ink is not absorbed and does not spread, the colors do not lose their richness, and the absence of bleeding allows you to print clear images as in the original file. That is why you can print on any surface without losing richness and clarity. - Durability
In indoor advertising, the service life of UV printing is 10 - 15 years, and in outdoor advertising it is limited to 4-5 years. This is explained by the fact that outdoor advertising materials are still exposed to ultraviolet radiation and significant temperature changes. - White printing
Currently, very few printers can boast the ability to print in white. Wherein White color can be a substrate, opaque, and simply as a 5th additional color when printing on dark surfaces
So why pay for UV printing?
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The UV printing technology itself is much more expensive than simple interior printing using solvent plotters. But when printing on a solvent plotter, there are a number of significant disadvantages, including those harmful to health, since even after a few days, solvent ink continues to evaporate from the surface of the film. And it’s better not to mention the list of diseases that it causes in a decent place. As an example, let's look at the most common case - making a skinali ( kitchen apron) So, the skinali is installed in the kitchen between the lower and upper drawers, in close proximity from cooking. It is natural in this case to use more environmentally friendly products. Tempered glass for gas stove located in an area with temperature changes, and the film in such places can “float”, with bubbles appearing and the film drying out towards the center of the glass, which in turn leads to the appearance of transparent stripes along the edges of the skin. This looks especially critical at the junctions of individual glasses. UV printing lacks all this, because... it is applied directly to the glass and is not afraid high temperatures. An additional bonus will be high quality pictures and printing into the edge of the glass, even bevels are sealed. The difference in the cost of one square meter of photo printing on film and UV printing is 600-800 rubles. With an apron length of 4 running meters. additional costs will be 1.5 - 2 thousand rubles. But for this money you will get bright colors, without dust and debris under the film, without transparent edges, with a 10-15 year guarantee. You deserve a good product for the money spent! |
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Main characteristics:
- Aesthetic/visual characteristics;
- Color;
- Shine;
- The surface is smooth, textured, grainy...;
- Performance characteristics;
- Formability and general mechanical properties;
- Corrosion resistance;
- UV resistance.
All these characteristics are checked either during the manufacturing process or after it, and can be verified by various tests and measurements.
Product specifications are based on these tests.
1. Mechanical properties paints
Required characteristics:
Molding methods:
- Bending;
- Profiling;
- Deep drawing.
Contact tool with organic coating:
- Wear resistance;
- Lubricating properties of paint.
Processing temperature minimum 16°C
2. Mechanical properties: Flexibility
T-bend
A flat sample of colored material is bent parallel to the rolling direction. The action is repeated to obtain an increasingly less rigid bend radius.
Determines the adhesion and flexibility of the coating system in the bending deformation mode (or tensile mode) at room temperature(23°С ±2°С).
The results are expressed, for example (0.5 WPO and 1.5T WC).
Impact test
A flat sample of painted material is deformed by impact with a 20 mm hemispherical punch weighing 2 kg. The height of the fall determines the impact energy. Coating adhesion and flexibility are tested.
The ability of the painted material to withstand rapid deformation and impact (resistance to coating peeling and cracking) is assessed.
3. Mechanical properties: Hardness
Pencil hardness
Pencils of varying hardness (6B - 6H) move along the surface of the coating under constant load.
The surface hardness is assessed using a “pencil”.
Klemen Hardness (Scratch Test)
An indenter with a diameter of 1 mm moves along the surface with constant speed. Various loads can be applied on top (from 200 g to 6 kg).
Determined various properties: hardness of the coating surface when scratched, friction properties, adhesion to the substrate.
Results depend on the thickness of the painted product.
Taber hardness (wear resistance test)
A flat sample of colored material is rotated under two abrasive wheels installed in parallel. Abrasion is achieved by circular motion of the test panel and constant load.
Taber hardness is the resistance to abrasion due to rough contact.
Measuring stress on metal tiles shows that deformations in some areas can be very strong.
Longitudinal stretch can reach 40%.
Shrinkage in the transverse direction can reach 35%.
5. Mechanical properties: an example of deformation in the production of metal tiles.
Marcignac test:
1st step: deformation in the Marcignac device;
2nd step aging in a climate chamber (tropical test).
To reproduce on a small scale the most severe deformations observed on industrial roofing tiles.
To simulate paint aging after profiling and evaluate the performance of paint systems.
6. Corrosion resistance.
The corrosion resistance of painted products depends on:
Environment (temperature, humidity, precipitation, aggressive substances, such as chlorides...);
The nature and thickness of the organic coating;
The nature and thickness of the metal base;
Surface treatments.
Corrosion resistance can be measured:
Accelerated tests:
Various accelerated tests can be carried out under various "simple" (artificially created) aggressive conditions.
Natural influence:
Possible exposure to various environments: maritime climate, tropical, continental, industrial conditions...
7. Corrosion resistance: accelerated testing
Salt test
The painted sample is exposed to a continuous salt spray (continuous spraying of a 50g/l sodium chloride solution at 35°C);
The test duration varies from 150 to 1000 hours depending on the product specification;
The ability of corrosion inhibitors (moderators) to block anodic and cathodic reactions at edges and risks;
Wet soil adhesion;
The quality of surface treatment through its sensitivity to an increase in pH level.
8. Corrosion resistance: accelerated testing
Resistance to condensation, QST test
A flat painted sample is exposed to condensation conditions (on one side the panel is exposed to a humid atmosphere at 40°C, the other side is kept at room conditions).
Moisture resistance, KTW test
A flat painted sample is subjected to cyclic exposure (40°C > 25°C) in a saturated aqueous atmosphere;
After testing, the appearance of bubbles on the metal of the test sample is determined;
Wet adhesion of soil and surface treatment layer;
Barrier effect of the outer layer coating and its porosity.
Corrosion test of internal coil turns
A flat painted sample is placed under a load of 2 kg in a pack with other samples and subjected to cyclic exposure (25°C, 50%RH > 50°C or 70°C, 95%RH);
Extreme conditions leading to corrosion between turns of the roll during transportation or storage (wet soil adhesion, barrier effect of the top layer coating and porosity in closed conditions packs).
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10. Corrosion resistance: Open exposure (Durability standards: EN 10169)
According to EN 10169, products for outdoor structures must be exposed to the environment for a minimum of 2 years.
Characteristics required for RC5: 2mm and 2S2, mainly under canopy (90°C sample) and in overlap areas (5° sample).
11. Resistance to UV exposure (fading)
After corrosion, UV exposure is the second major threat to the durability of painted materials.
The term "UV fading" means a change appearance paint (mostly color and shine) over time.
Not only exposure to UV radiation degrades paint quality, but also other environmental influences:
Sunlight - UV, visible and infrared ranges;
Humidity – time of surface wetting, relative humidity;
Temperature - crack resistance - maximum values and daily heating/cooling cycles;
Wind, rain - sand abrasion;
Salt – industrial, coastal areas;
Dirt – the effects of soil and pollutants...
12. UV fading
Accelerated UV resistance test
How is the test performed?
Standards: EN 10169;
A flat OS sample is exposed to UV radiation;
UV irradiation;
Possible periods of condensation;
2000 hours of exposure (4H condensation cycles 40°C/4H irradiation at 60°C with radiation 0.89V/m2 at 340 nm);
After testing, changes in color and gloss are determined.
13. UV resistance
- EN 10169: Accelerated testing
- EN 10169: Environmental exposure:
Only lateral impact on the sample for 2 years in places with fixed solar radiation energy (at least 4500 MJ/m2/year) > Guadeloupe, Florida, Sanari, etc...
