Enamel resistance to fading

Conditional lightfastness was determined on samples of dark gray RAL 7016 enamel on REHAU BLITZ PVC profile.

The conditional light fastness of the paintwork was 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". p. 7.2, tab. 1, approx. 3.

Determining the conditional light fastness at a radiation intensity of 80±5 W/m 2 was controlled by changing the gloss of the coatings and color characteristics. The color characteristics of the coatings were determined on a Spectroton device after wiping the samples with a dry cloth to remove the formed plaque.

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			Gloss loss, %	Color coordinate - L	Color coordinate - a	Color coordinate -b	Color change Δ E to standard
		Before testing	After testing

Samples 1 to 4 are considered to have passed the test.

The 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:

Luminous flux power up to 80±5 W/m 2 leads to sharp drop gloss of coatings by 98% after 36 hours of testing as a result of plaque formation. With continued testing, no further loss of gloss occurs. Light fastness can be characterized in accordance with GOST 30973-2002 - 40 conditional years.

The color characteristics of the coating are within acceptable limits and comply with GOST 30973-2002 on samples No. 1, No. 2, No. 3, No. 4.

Main characteristics:

• Aesthetic/visual characteristics;
• Color;
• Shine;
• The surface is smooth, textured, grainy…;
• performance;
• Formability and general mechanical properties;
• Corrosion resistance;
• UV resistant.

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 of the paint

Required characteristics:

Forming Methods:

• Bending;
• Profiling;
• Deep draw.

Contact tool with organic coating:

• wear resistance;
• Lubricating properties of paint.

Processing temperature min. 16°C

2. Mechanical properties: Flexibility

T-bend

A flat piece of colored material is bent parallel to the rolling direction. The action is repeated to obtain an increasingly less rigid bending radius.

The adhesion and flexibility of the coating system in bending mode (or tensile mode) at room temperature (23°C ±2°C) is determined.

The results are expressed, for example (0.5 WPO and 1.5T WC).

impact test

A flat sample of the colored 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 a painted material to withstand rapid deformation and impact is evaluated (resistance to coating peeling and cracking).

3. Mechanical properties: Hardness

Pencil hardness

Pencils of different hardness (6B - 6H) move along the surface of the coating under constant load.

The hardness of the surface is evaluated by the "pencil".

Klemen Hardness (Scratch Test)

An indenter with a diameter of 1 mm moves along the surface at a constant speed. Various loads can be applied from above (from 200 g to 6 kg).

Various properties are determined: surface hardness of the coating during scratching, frictional properties, adhesion to the substrate.

The results depend on the thickness of the painted product.

Taber hardness (wear test)

A flat piece of dyed material is rotated under two abrasive wheels installed in parallel. Abrasion is achieved by a circular motion of the test panel and a constant load.

Taber hardness is the resistance to abrasion at rough contact.

Measurement of the stress on the metal tile shows that the deformations in some areas can be very strong.

Stretching in the longitudinal direction 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 climatic chamber (tropical test).

To reproduce on a small scale the most severe deformations observed in industrial roof tiles.

For modeling paint aging after profiling and evaluating 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 in various "simple" (artificially created) aggressive conditions.

Natural influence:

Various environments are possible: maritime climate, tropical, continental, industrial environments…

7. Corrosion resistance: accelerated tests

salt test

The painted specimen is exposed to continuous salt spray (continuous spraying of 50g/l sodium chloride solution at 35°C);

The duration of the test varies from 150 to 1000 hours depending on the product specification;

The ability of corrosion inhibitors (retarders) to block anodic and cathodic reactions at the edges and risks;

Wet soil adhesion;

The quality of a surface treatment through its sensitivity to an increase in pH.

8. Corrosion resistance: accelerated tests

Condensation resistance, QST test

A flat painted sample is exposed to condensate conditions (one side of 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 primer and surface treatment layer;

Barrier effect of outer layer coating and its porosity.

Internal Coil Corrosion Test

A flat colored 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 coil windings during transport or storage (wet soil adhesion, top coat barrier effect and porosity in closed pack conditions).

90° North	5° South

10. Corrosion resistance: Open exposure (Durability standards: EN 10169)

In accordance with EN 10169, outdoor products must be exposed to environment for at least 2 years.

Characteristics required for RC5: 2 mm and 2S2, mainly under canopies (sample 90°C) and in overlapping areas (sample 5°).

11. UV resistance (fading)

After corrosion, UV exposure is the second major threat to the durability of painted materials.

The term "UV burn" means a change appearance paint (mostly color and gloss) over time.

Not only does exposure to UV radiation degrade the quality of the paint, but other environmental influences also:

Sunlight - UV, visible and infra-red ranges;

Humidity – surface wet time, relative humidity;

Temperature - crack resistance - maximum values ​​and daily heating/cooling cycles;

Wind, rain - abrasion with sand;

Salt - industrial, coastal zones;

Dirt – soil impact and pollutants…

12. UV fading

Accelerated UV resistance test

How is the test carried out?

Standards: EN 10169;

A flat OS sample is exposed to UV radiation;

UV irradiation;

Possible periods of condensation;

2000 hours exposure (Cycles 4H condensation 40°C/4H irradiation at 60°C with 0.89V/m2 radiation at 340 nm);

After testing, changes in color and gloss are determined.

13. UV resistance

- EN 10169: Accelerated tests

- EN 10169: Environmental exposure:

Only lateral impact on the sample for 2 years in places with a fixed energy of solar radiation (at least 4500 MJ / m2 / year) > Guadeloupe, Florida, Sanary, etc…

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. Such a study made it possible to reveal differences in UV resistance among species and genera of the Dematiaceae family widely distributed in the soil, to determine the distribution of this trait within each biocenosis, and its taxonomic and ecological significance.

We have studied resistance to UV rays (254 nm, dose intensity 3.2 J/m species of 19 genera) soils. When studying the UV resistance of Dematiaceae cultures isolated from the flat saline soils of the south of the Ukrainian SSR, we proceeded from the assumption that with an increase in unfavorable living conditions due to soil salinity, a greater number of resistant species of dark-colored hyphomycetes will accumulate in it than in other soils. In some cases, it was not possible to determine UV resistance due to the loss or sporadic sporulation in the 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 frequent 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. Species whose survival rate ranged from 0.01 to 1% and from 0.01% and below, we classified as sensitive and highly sensitive.

Large fluctuations in the UV stability 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 genera (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 Dematiaceae family, 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 characterized 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.

A significantly larger number of species are resistant to UV rays. These include species of the genera Alternaria, Stemphylium, Curvularia, Helminthosporium, Bispora, Dendryphion, Rhinocladium, Chrysosporium, Trichocladium, Stachybotrys, Humicola. 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. Note that 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 fairly dense, intensely pigmented, rough cell membranes, in contrast to the second group of species, the cell walls of which are thinner and less pigmented. Sensitive species whose survival rate after irradiation with a dose of 408 J/m 2 was less than 0.01% are Diplorhinotrichum sp., Phialophora sp., Chloridium apiculatum, etc. There were no large-spore dark-colored hyphomycetes 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. The 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 trend was especially clear in the basal conidia. Noticeable changes in the morphology of conidia were also observed in large-spore, 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 elongated and became almost straight; in the conidia of Alternaria alternata, the number of longitudinal septa decreased until they completely disappeared, and they themselves became larger than the control ones. On the contrary, the conidia of H. turcicum became smaller, the number of septa in them decreased, 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 Dematiaceae family confirmed a certain dependence of UV resistance on the size of conidia and pigmentation of their membranes. As a rule, large conidia are more resistant than small ones. It should be noted that the index chosen by us - the survival rate - of melanin-containing fungi after irradiation with a dose of 408 J/m , Kumita, 1972). It is quite obvious that the nature of this phenomenon needs further study with the involvement of species of the Dematiaceae family that are highly resistant and resistant to this trait.

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, was 0.02-0.19% after a dose of 408 J/m 2 (2-hour exposure), and resistance to this factor was distributed within 6 orders of magnitude. Consequently, the assumption of increased resistance to UV irradiation of dark-colored hyphomycetes from saline soils was not confirmed.

The UV resistance of alpine species of the Dematiaceae family differed markedly from that described above, which was reflected in the change in the position of the peak of the curve and the range of distribution.

For 34.4% of cultures, the 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 radiation. The distribution range for this property did not exceed four orders of magnitude.

In connection with the revealed differences in the distribution of the trait of UV resistance in lowland and high-mountain species and genera of the Dematiaceae family, it seemed appropriate to check how they occur: due to the predominant occurrence of highly resistant and UV-resistant species of dark-colored hyphomycetes in mountain soils, or there is an increased resistance to UV radiation of high-mountain strains of the same species or genus compared to lowland strains. To prove the latter, we compared cultures of the Dematiaceae family isolated on the surface of plain and high mountain soils, as well as from surface (0–2 cm) and deep (30–35 cm) horizons of plain meadow soils. Obviously, such mushrooms are in extremely unequal conditions. The samples we used made it possible to analyze 5 common genera of the Dematiaceae family isolated on the surface of plain and high mountain soils on the basis of UV resistance. Only strains isolated from alpine soils, species of the genus Cladosporium and Alternaria are significantly more resistant than strains isolated from plain soils. On the contrary, the UV resistance of strains isolated from lowland soils was significantly higher than that of highland soils. Consequently, differences in the microflora of areas with increased insolation (alpine soils) in relation to UV rays 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 provision is obviously of particular importance.

Comparison of 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 changes in the trait of resistance to UV rays in natural isolates of widespread Dematiaceae species was mostly the same in lowland and high-mountain isolates and did not exceed two orders of magnitude. The 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 the conidia remained alive.

The next task was to study the resistance of some species of the Dematiaceae family to biologically extreme doses of UV radiation and artificial sunlight (ISS) high intensity(Zhdanova et al. 1978, 1981).

A monolayer of dry conidia on a gelatinous substrate was irradiated according to the Lee method modified by us (Zhdanova and Vasilevskaya, 1981), and comparable, statistically significant results were obtained. The source of UV radiation was a DRSh-1000 lamp with a UFS-1 light filter that transmits 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 Ch-1 mutant are highly resistant to this effect.

Thus, the survival of S. ilicis after a dose of 1 ∙ 10 5 J/m 2 was 5%. A 5% survival rate for Ch-1 mutant, C. transchelii, K-1 and BM mutants was observed after doses of 7.0 x 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 ISS. The source of radiation was a solar illuminator (OS - 78) based on a DKsR-3000 xenon lamp, providing radiation in the wavelength range of 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 value of the total flux of solar radiation outside the earth's atmosphere at an average Earth-Sun distance, incident on 1 cm 2 of the surface in 1 s. The measurement of specific irradiance was carried out according to a special technique at the position of the sample using a luxmeter 10-16 with an additional neutral light filter. Each strain was irradiated with at least 8-15 successively increasing radiation doses. Irradiation time varied from 1 min to 12 days. Resistance to ISS was judged by the survival rate of fungal conidia (the number of formed macrocolonies) in relation to non-irradiated control, taken as 100%. A total of 14 species of 12 genera of the Dematiaceae family were tested, of which 5 species were studied in more detail.

The resistance of cultures of C. transchelii and its mutants to ISS depended on the degree of their pigmentation. Graphically, it was described by a complex exponential curve with an extensive resistance plateau. The LD value of 99.99 upon irradiation in air for the Ch-1 mutant was 5.5 10 7 J/m 2 , the initial 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 increased markedly (LD 99.99 - 2.4 ∙ 10 8 J/m 2 ), the type of dose survival curve changed (multicomponent curve). For other strains, such exposure was more detrimental.

When comparing resistance to UV rays and high-intensity ISS of cultures of C. transchelii and its mutants, many similarities were found, despite the fact that the effect of ISS was studied on “dry” conidia, and an aqueous suspension of spores was irradiated with UV rays. In both cases, a direct relationship between the resistance of fungi and the content of melanin pigment PC in the cell membrane was found. A comparison of these properties indicates the participation of the pigment in the resistance of fungi to ISS. The mechanism of the photoprotective action of the melanin pigment proposed later makes it possible to explain the long-term resistance of melanin-containing fungi to total doses of UV rays and ISS.

The next stage of our work was the search for cultures of melanin-containing fungi more resistant to this factor. They turned out to be species of the genus Stemphylium, and the stability of cultures S. ilicis and S. sarciniforme 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 cultures corresponded to the value of LD 99 . In a vacuum, with more intense irradiation, the survival rate of Stemphylium ilicis cultures was somewhat higher 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 rate of 10 and 5%.

Thus, a unique resistance of a number of representatives of the Dematiaceae family (S. ilicis, S. sarciniforme, C. transchelii Ch-1 mutant) to long-term high-intensity ISS irradiation was found. In order to compare the obtained results with the previously known ones, we reduced the values ​​of sublethal doses obtained for our objects by an order of magnitude, since the UV rays (200–400 nm) of the OS-78 facility amounted to 10% in its luminous 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 the light of ideas about the mechanism of the photoprotective action of the melanin pigment (Zhdanova et al., 1978), the interaction of the pigment with light quanta led to its photooxidation in the fungal cell and, subsequently, to stabilization of the process due to reversible electron phototransfer. In an argon atmosphere and in 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 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 melanin pigment photooxidation, 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 Dematiaceae family 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 resistant group of species was identified, which significantly exceeds such microorganisms as Micrococcus radiodurans and M. radiophilus in this property. A peculiar character of the survival of dark-colored hyphomycetes was established according to the type of two- and multi-component curves, which were first described by us.

A study was made of the distribution of the trait of resistance to UV rays of dark-colored hyphomycetes in the high-mountain soils of the Pamir and Pamir-Alay and in the meadow soils of Ukraine. In both cases, it resembles a normal distribution, but UV-resistant species of the Dematiaceae family clearly predominated in the mycoflora of alpine soils. This indicates that solar insolation causes profound changes in the microflora of the surface soil horizons.

IN AND. Tretyakov, L.K. Bogomolova, O.A. Krupinin

One of the most aggressive types of operational impacts on polymer Construction Materials is UV exposure.

To assess the resistance of polymeric building materials, both full-scale and accelerated laboratory tests are used.

The disadvantage of the former is long duration tests, the impossibility of isolating the influence of a single factor, as well as the difficulty of taking into account annual fluctuations in atmospheric effects.

The advantage of accelerated laboratory tests is that they can be carried out in a short time. At the same time, in some cases, it is possible to describe the obtained dependences of changes in properties over time by known mathematical models and predict their durability for longer periods of operation.

The purpose of this work was to assess the resistance to UV radiation in the conditions of the Krasnodar Territory of samples of white laminated polypropylene fabric with special additives in the shortest possible time.

Laminated polypropylene fabric is used for temporary protection of erected and reconstructed building structures, as well as individual elements from atmospheric influences.

The resistance of the material to UV irradiation was evaluated by changing the tensile strength according to GOST 26782002 on samples - strips, dimensions (50x200) ± 2 mm and a change in appearance (visually).

For the limiting value of the aging of the material is taken to reduce its strength to 40% of the original value.

Tensile strength tests were carried out on a ZWICK Z005 universal testing machine (Germany). The initial tensile strength of the tested samples was

115 N/cm. ""

" Picture 1.

Ultraviolet irradiation of the image

material samples were carried out in an irradiation apparatus

artificial weather (AIP) type "Xenotest" with a xenon emitter DKSTV-6000 according to GOST 23750-79 with a water cooling system and a quartz glass jacket. The radiation intensity in the wavelength range of 280-400 nm was 100 W/m2. The hourly dose of UV irradiation (O) is 360 kJ/m2 for this spectral regime.

During exposure to AIP, the intensity of tissue irradiation was controlled by an intensimeter - a dosimeter manufactured by OBkDM (Germany).

The samples were irradiated continuously for 144 h (6 days). Removal of samples to assess the change in tensile strength was carried out at certain intervals. The dependence of the residual tensile strength (in %) on the initial value of the laminated polypropylene fabric on the time of irradiation in the AIP is shown in Figure 1.

After mathematical processing of the obtained data using the least squares method, the obtained experimental results are generalized by the linear dependence shown in Figure 2.

20 40 60 80 100 120 140 160 Dependence of residual tensile strength (in %) on the value of laminated polypropylene fabric on time in AIP

building materials and structures

Theoretical Observatory of Moscow State University is 120,000 kJ/m2 year (O f M)

At the same time, there are no data on the annual dose of the UV part of solar radiation in the Krasnodar Territory (Ouf c c) in the literature. The above values ​​of Osum for Moscow and the Krasnodar Territory make it possible to approximately calculate the total annual UV dose for the Krasnodar Territory according to following formula:

O f -O c / O

uv M sums K.k "

Figure 2. Linear dependence of the residual tensile strength of a laminated polypropylene fabric on the logarithm of the irradiation time in the AIP

1 - experimental values; 2 - values ​​calculated using equation (1)

Consequently,

Of k \u003d 1200001.33 \u003d

160320 kJ/m2 year

P% \u003d P0 - 22.64-1dt,

where P% ost - residual value of tensile strength (in%) after UV irradiation; P0 - initial value of tensile strength (in%), equal to 100; 22.64 - a value numerically equal to the tangent of the slope of the straight line in the coordinates: residual tensile strength (in %) - the logarithm of the irradiation time in the AIP; T is the exposure time in the AIP, in hours.

The results of mathematical processing (see equation (1) and figure 2) allow extrapolating the obtained data for a longer test period.

An analysis of the obtained results shows that a decrease in the residual strength of the laminated polypropylene fabric up to 40% will occur after 437 hours of irradiation. In this case, the total dose of UV radiation will be 157320 kJ/m2.

A visual assessment of the appearance of the irradiated material shows that already after 36 hours of irradiation, the tissue has a denser structure, becomes less loose and less shiny. With further irradiation, the stiffness and density of the tissue increase.

According to GOST 16350-80, the total dose of solar radiation (Osumm) for the temperate warm climate with mild winters in the Krasnodar Territory (GOST, table 17) is 4910 MJ / m2 (Osum Kk), and for the temperate climate of Moscow - 3674 MJ / m2 (Osum M ). The annual dose of the UV part of solar radiation according to the Moscow

Comparison of the annual dose of UV irradiation for the Krasnodar Territory (160320 kJ/m2) with the dose of UV irradiation in laboratory conditions (157320 kJ/m2) allows us to conclude that under natural conditions the strength of the material will decrease to 40% of the initial value under the action of UV radiation. exposure for approximately one year.

Conclusions. Based on the presented material, the following conclusions can be drawn.

1. The resistance of samples of laminated polypropylene fabric for construction purposes to the action of UV irradiation in laboratory conditions was studied.

2. By calculation, the annual dose of UV radiation for the Krasnodar Territory was determined, which is 160320 kJ/m2.

3. According to the results of laboratory tests for 144 hours (6 days), it was found that the change in tensile strength under the influence of UV irradiation is described by a linear logarithmic dependence, which made it possible to use it to predict the light fastness of a polymer fabric.

4. Based on the dependence obtained, it was determined that the decrease in the strength of the laminated polypropylene fabric for construction purposes to a critical level under the influence of UV irradiation under natural conditions in the Krasnodar Territory will occur in approximately one year.

Literature

1. GOST 2678-94. Materials are rolled roofing and waterproofing. Test methods.

building materials and structures

2. GOST 23750-79. Devices of artificial weather on xenon emitters. General technical requirements.

3. GOST 16350-80. Climate of the USSR. Zoning and statistical parameters of climatic factors for technical purposes.

4. Collection of observations of the meteorological observatory of Moscow State University. M.: Publishing House of Moscow State University, 1986.

Accelerated method for evaluating UV resistance of laminated polypropylene fabric for construction purposes

To assess the light resistance of samples of laminated polypropylene fabric for construction purposes to UV irradiation in laboratory conditions by reducing the tensile strength of the test material to a limit value of 40%, a linear dependence of the residual strength on the exposure time in an artificial weather apparatus was obtained in logarithmic coordinates.

Based on the dependence obtained, it was determined that the decrease in the strength of the laminated polypropylene fabric for construction purposes to a critical level under the influence of UV irradiation in natural conditions of the Krasnodar Territory will occur in approximately one year.

The accelerated method of an estimation of resistance of the laminated polypropylene fabrics for building appointment to the ultraviolet-irradiation

by V.G. Tretyakov, L.K. Bogomolova, O.A. Krupinina

For an estimation of light resistance of laminated polypropylene fabric samples for building appointment to ultraviolet-irradiation influence in vitro on durability decrease at a stretching of a tested material to limiting value of 40% the linear dependence of residual durability on irradiation time in the device of artificial weather in logarithmic coordinates is received.

On the basis of the received dependence it has been defined that decrease in durability laminated polypropylene fabrics for building to a critical level under the influence of the ultraviolet-irradiation in natural conditions of Krasnodar territory would be occur approximately in one year.

Keywords: light fastness, ultraviolet irradiation, prediction, critical strength level, climate, laminated polypropylene fabric.

Key words: light resistance, ultraviolet-irradiation, prognostication, critical level of durability, climate, laminated polypropylene fabric.

It has already been noted above (see the previous article) that the rays of the UV range are usually divided into three groups depending on the wavelength:
[*]Long wave radiation (UVA) - 320-400 nm.
[*] Medium (UVB) - 280-320 nm.
[*]Shortwave radiation (UVC) - 100-280 nm.
One of the main difficulties in taking into account the impact of UV - radiation on thermoplastics is that its intensity depends on many factors: the ozone content in the stratosphere, clouds, location altitude, the height of the sun above the horizon (both during the day and during the year ) and reflections. The combination of all these factors determines the level of UV radiation intensity, which is reflected on this map of the Earth:

In areas colored in dark green, the intensity of UV radiation is highest. In addition, it must be taken into account that fever and humidity further enhance the effect of UV radiation on thermoplastics (see previous article).

[B]The main effect of UV radiation on thermoplastics

All types of UV - radiation can cause a photochemical effect in the structure of polymeric materials, which can both be beneficial and lead to degradation of the material. However, by analogy with human skin, the higher the radiation intensity and the shorter the wavelength, the greater the risk of degradation of the material.

[U]Degradation
The main visible effect from the impact of UV radiation on polymeric materials is the appearance of the so-called. "chalky spots", discoloration on the surface of the material and increased fragility of surface areas. This effect can often be seen in plastic products permanently operated outdoors: seats in stadiums, garden furniture, greenhouse film, window frames, etc.

At the same time, thermoplastic products often have to withstand exposure to UV radiation of types and intensities that are not found on Earth. We are talking, for example, about the elements of spacecraft, which requires the use of materials such as FEP.

The effects noted above from the action of UV radiation on thermoplastics are noted, as a rule, on the surface of the material and rarely penetrate deeper than 0.5 mm into the structure. However, the degradation of the material on the surface under load can lead to the destruction of the product as a whole.

[U]Buffs
IN Lately Special polymer coatings, in particular those based on polyurethane-acrylate, which are "self-healing" under the influence of UV radiation, have found wide application. The disinfecting properties of UV radiation are widely used, for example, in coolers for drinking water and can be further enhanced by the good transmission properties of PET. This material is also used as a protective coating on UV insecticidal lamps, providing up to 96% light transmission at a thickness of 0.25 mm. UV radiation is also used to restore ink applied to a plastic base.

The positive effect of exposure to UV radiation is the use of fluorescent whitening reagents (FWA). Many polymers have a yellowish tint in natural light. However, the introduction of UV rays into the composition of the FWA material is absorbed by the material and emits back the rays of the visible range of the blue spectrum with a wavelength of 400-500 nm.

[B] Effect of UV radiation on thermoplastics

UV radiation energy absorbed by thermoplastics excites photons, which in turn form free radicals. While many thermoplastics in their natural, pure form do not absorb UV radiation, the presence of catalyst residues and other contaminants in their composition that serve as receptors can lead to material degradation. Moreover, to start the degradation process, insignificant fractions of pollutants are required, for example, a billionth of sodium in the composition of polycarbonate leads to color instability. In the presence of oxygen, free radicals form oxygen hydroperoxide, which breaks the double bonds in the molecular chain, making the material brittle. This process is often referred to as photooxidation. However, even in the absence of hydrogen, degradation of the material still occurs due to related processes, which is especially typical for spacecraft elements.

Thermoplastics with poor UV resistance in their unmodified form include POM, PC, ABS and PA6/6.

PET, PP, HDPE, PA12, PA11, PA6, PES, PPO, PBT are considered sufficiently UV resistant, as is the PC/ABS combination.

PTFE, PVDF, FEP and PEEK have good UV resistance.

PI and PEI have excellent UV resistance.