Product description

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ECOBOND® Aluminium Composite panels consist of two aluminium sheets and a special polymeric core sandwiched between them. Polymeric core itself is rather flexible, so its strength properties at expansion are not high enough. In sandwich structures the polymeric core, firmly glued to covering aluminium sheets, fixes an exact distance between them and lends to the panel high degree of flatness and excellent mechanical properties, such as strength and rigidity.

ACP composition:
1. Anti-corrosive protective coating.
2. Aluminium alloy sheet.
3. Adhesion layer.
4. Polymeric core.
5. Adhesion layer.
6. Aluminium alloy sheet.
7. Primer.
8. PVDF or polyester paint layer.
9. Clear coating.
10. Protective peel-off film.

Protective film

Protective film on aluminium composite panels is intended for protection from scratches, abrasion, contamination and other damages of the surface. Ecobond composite panels have a two-layer protective film manufactured by co-extrusion, and in comparison with analogues it is thicker and, furthermore, has a better breaking strength and grinding resistance. It is based on low-density polyethylene with a white and black filling compounds.
A white layer outside is used for marking and light reflection, i.e. reduction of excessive light load exposure that may cause the surface heating under the sunlight. Black layer from the inner side of the film is intended for light absorption in blue and ultraviolet parts of spectrum.
One may ask: "Why is UV protection necessary for the film if the panels are used outdoors for years?". The matter is that the panel located on the building or used in some advertising structure may stay under the sunlight for several days or weeks, and the protective film should be easily removable after installation. The glue applied for sticking the film to the surface has an ability to get polymerized under the impact of intensive light, and especially under UV exposure. Such exposure will complicate protective film removal from the surface. If protective film is removed immediately after the panel or cassette is installed, it's possible to avoid excessive UV impact to the glue. However, it is recommended to remove the protective film only after completion of installing the whole cladding system or finished project in order to avoid harmful "contacts" that any construction site abounds in.
For ECOBOND® composite panels the manufacturer applies a special glue that has a strong adhesion to polyethylene and an average degree of sticking to the paint coat. Besides, the glue neither delaminates nor splits, it is resistant to high temperature, humidity and natural values of pH acidity that sometimes occur due to acid or alkaline rains.
In addition to surface protection, ECOBOND® protective film contains useful information. The first thing one should pay attention to are the arrows showing the direction of panels rolling. When light falls onto the surface of a composite panel, it is reflected differently in lengthwise and crosswise directions relatively to aluminium rolling direction. Multitude of particles have various sizes lengthwise and crosswise, but they are situated in such a way that the certain orientation prevails. Therefore, protective film is entrusted with an important function: to show by arrows how to install the cassettes and other items so that they would be placed in the same direction.
The arrows on the protective film indicate the time of surface staying under the sunrays. How does it work? The arrows fade in the course of time, so if the allowable period of keeping the protective film on the ACP surface is over, the faded arrows that turned from red into whitish crimson show that the protective film should be removed urgently. As determined by manufacturer, ECOBOND® Protective film should be removed from composite panels within 45 days at latest.

Kinds of coating: polyester, PVDF

ECOBOND® panels have two kinds of painted coatings: polyester (PE) and PVDF (polyvinylidene fluoride). These coatings have a three-layered structure and always include the primer. Primer improves the degree of adhesion of the painted coat to aluminium. For surface gloss effect and for better resistance to chemical, abrasive and UV exposure, a transparent lacquer is additionally applied. ECOBOND® Plus и ECOBOND® Plus FR panels have PVDF coating.
Colored polyester coating is considered to be relatively inexpensive and it is applicable for advertising and interior use. Color retention of polyester is not strong enough, so long-time UV exposure may gradually change the coating color tone. Application of polyester as aluminium sheet coating is a reasonable and economically sound choice when the material is not used in chemically contaminated environment, and the working load is not too heavy. For example, in interior the panels with such kind of coating can be used for dozens of years. For exterior use, resistance to color fading depends on the cumulative UV exposure and the color chosen. It should be noted that metallic finish coating has a better resistance to outer exposures, but in case of replacing separate panels the difference between old and new panels will always be visible. It happens because, firstly, separate lots of the panels may have a slight difference in color and grain of metal powder added to lacquering, and, secondly, a protective transparent lacquer is gradually tarnishing under the solar radiation exposure.
KYNAR 500® – three-layer PVDF coating
Kynar 500® –is a three-layered coating based on PVDF (polyvinylidene fluoride) developed by ATOFINA (now ARKEMA) company. A process of ECOBOND®Plus coating is performed under the license of this company. Chemical name of PVDF is homopolymer of 1,1-di-fluoro-ethene. It's a very tough thermoplastic that offers a unique balance of properties. It has high stability of fluoropolymer when exposed to harsh environment, including high and low temperatures, chemicals, UV radiation, abrasion, etc. Substitution of CH2 group by CF2 group along the polymer chain creates a unique polarity that influences its solubility, chemical interaction end electric properties. Fluoropolymeric coating Kynar 500® is a high-tech product that can be processed by standard methods of extrusion and hot-melt roller application. It is only at high temperatures that PVDF can be dissolved in polar solvents such as organic esters and amines. That's one of the main advantages of corrosion-proof cladding panels for architectural projects.

KYNAR 500® – three-layer PVDF coating

Main properties of PVDF KYNAR® 500:
• Mechanical strength
• High durability
• High thermal stability
• Hot-melt roller application processability
• Resistance to most chemicals and solvents
• Resistance to UV and radioactive radiation
• Remarkable resistance to weathering
• Excellent reliability for exterior application
• Good color retention
• Stains resistance, "anti-graffiti effect" (paints do not stick on PVDF)
• Self-cleaning from dust due to low surface energy
• Flexibility and elasticity (ability to stretch)
• Biological resistance to mould, fungi, bacteria
• Low permeability for most gases and liquids
• Low flammability and combustibility (does not burn itself), low smoke characteristics.
To create metallic tone of the coating, a fine aluminium-based metal powder is added to the polymeric coating. Good quality facing coat usually consists of three layers: primer, a colored layer and a transparent protective layer. Total thickness is approximately 30 μm. Without primer, polymeric layer cannot stick to the surface firmly enough. Lack of lacquering affects resistance to abrasion.
The process of application of polyester coating to rolled aluminium sheet differs from that of PVDF-coating. For polyester coating application, a polymer solution in a solvent is applied by roller method. This coating can be re-painted. PVDF coating cannot be painted because the adhesive force between a polar polymer and other substances is very weak. By the way, that's what self-cleaning property is explained by: no dirt can stick onto the surface. PVDF coat application process consists of several stages. First, PVDF polymer is heated to molten condition, then it is applied onto the surface painted by primer, and evenly spread by roller all over the surface with an uninterrupted broach of aluminium coil. Then, a procedure of thermal polymerization at high temperatures follows. Each further layer out of three-layered PVDF coating is applied at a lower temperature than a previous one. Elasticity and strength properties of the coating may be affected by "overheating" the polymer, i.e. exceeding the time or temperature of thermal processing. That is why in line production the process of rolled aluminium coating is supported by precise control of broaching speed and temperature at all application stages.
Application of advanced painting technology Kynar 500® makes it possible to increase the warranty life of ECOBOND® Plus panels up to 25 years.

How to check the quality of aluminium composite panel coating?
PVDF face coating differs from polyester coating by a better abrasion resistance and can be easily checked by harrowing, as well as grinding by felt disk or fine emery cloth. For example, you can harrow the panel coat by scraper with 1mm-thick blade, pushing it with 1 Kg force. If after 100 times harrowing the same place the aluminium becomes visible, it means that coating consists of polyester. If in some harrowed places you see a different color coating – primer, then the panel is coated by PVDF.
Good quality coating should neither whiten in the bending edges, nor crack when bent, nor peel-off from aluminium skin if ACP pre-grooved on the back side is bent and unbent for several times.
A kind of coating can be identified by chemical solubility. Xylene, an organic solvent, dissolves polyester to aluminium skin, but it cannot dissolve PVDF. Exposure time depends on coating thickness.
Quality of polyester coating, for instance, can be evaluated with the help of methyl ethyl ketone (MEK) that cannot dissolve two-and three-layered polymeric structure of coating, but disrupts it by penetrating into its pores. MEK exposure time is 8 to 24 hours. Painted coating layer can be then removed from aluminium surface by a piece of cloth, wiping it with a certain effort. Good quality coating resists to such process even in 24 hours after MEK solvent exposure.

Polymeric core

As a core of aluminium composite panels, two materials are applied: high-density polyethylene (HDPE) and a fireproof composite combination of a polymer with mineral base – aluminium hydroxide. Additionally, this composite combination contains antipyren – a flame-proofing agent. It should be noted that polymeric core with a mineral stuff increases the weight to ECOBOND® Plus FR panels, and they have a lower thermal insulation coefficient. In the ordinary panels, polyethylene filled with carbon is used. It is required for timing stability of the polymer, as well as protection from photo-destructive processes occurring under longtime exposure to direct or reflected sunlight falling onto the end surface of a composite panel. Unprotected high-density polyethylene under natural conditions is gradually ageing, i.e. losing its elasticity and other mechanical properties due to light and oxidation exposure.
Composite panels of other brands with the core made of other polymers, such as PVC foam or structured polypropylene, are characterized by a lower bending strength and elasticity, collapsibility under forge-rolling and narrow operating temperature range. Panels with honeycomb polymeric core should be 2-3 times thicker than ordinary panels for increasing of bending strength. Such panels have a smaller weight and are intended for specific applications, such as advertising and exhibition structures, as well as the facades with light load.

Aluminium layer

Excellent flatness and rigidity of the panels are explained by the fact that when the panel is bent, major load is taken by outer layer of metal sheet in the convex side. Major forces are applied not to bending but to elongation of outer metal layer and compression of the inner one. Though a thin aluminium layer (0.21mm or 0.3 mm) is easy to bend, its expansion and compression takes quite a considerable effort. A composite panel retains its rigidity (flexural strength) under considerable static load and dynamic load (such as wind force). That is why mechanical properties of covering metal sheets should meet high standards: high value of tensile modulus and breaking strength. At the same time, bending ability of panels requires flexible aluminium that would not crack in the bending corners. In ECOBOND® panels, a perfect balance between rigidity and flexibility was achieved in a special alloy composition based on aluminium and magnesium.
Tensile modulus and breaking strength of a composite panel mostly depend on total thickness of two aluminium skins and, to a lesser extent, thickness of polymer. That's why these mechanical parameters are approximately the same for the panels with various thicknesses of polymeric core. However, both polymer and aluminium covering layers' thicknesses influence ACP elastic properties at bending.
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