Pural, PVC, matt polyester and polyester: a technical comparison and the properties of each coating.
| Pural/PUR | PVC | Matt polyester | Polyester | |
|---|---|---|---|---|
| Coating thickness µm | 50 | 200 | 35 | 25 |
| Corrosion resistance | excellent | excellent | good | good |
| Fading | good | excellent | good | average |
| Flexibility | good | excellent | satisfactory | satisfactory |
| Maximum temperature °C | 100 | 110 | 90 | 90 |
| Minimum bending temperature °C | -15 | -35 | 0 | 0 |
The Pural coating resists weathering in extreme climates and is particularly resistant to corrosion. It resists ultraviolet light, does not fade and is easy to clean, and it suits projects that need an especially tough, long-lasting coating. Sheets with this coating are most effective on roofs and external wall cladding.
PURAL by Rautaruukki is a multi-layer coating system on hot-dip galvanized steel sheet. The steel can be of different grades and the zinc coating of different thicknesses. The zinc layer gives effective protection against corrosion at cut edges and in areas where the organic coating is damaged.
At the start of the coating process the metal surface is first cleaned twice on both sides and then chemically treated to improve adhesion and corrosion protection. All treatment steps are controlled both automatically and manually and are intended to ensure proper coating adhesion and corrosion resistance.
Top side. The primer and the top layer are applied by roller coating and the coating is cured in a hot oven. PURAL is a coating system intended for outdoor use, so it consists of a weather-resistant top layer, a primer layer and a chemically treated layer applied over the galvanized steel sheet.
Reverse side. Although the coating on the reverse side does not necessarily have to resist UV light, it does have to resist rust and adhere very well. The primer and epoxy layers on the well-cleaned and chemically treated reverse side provide a coating that fully meets these requirements. Where the reverse side is exposed to sunlight and therefore has to resist UV light, it can be coated in the same way as the top side.
| Product property | Value | Test method |
|---|---|---|
| Minimum dry film thickness, µm | 50 | EN 10169-1 |
| Bending radius x sheet thickness | 1 | EN 10169-1 |
| Adhesion | 1 | EN 10169-1 |
| Colour shades | E < 1.0 | EN 10169-1 |
| Gloss | (34 … 46) | EN 10169-1 |
| Corrosion resistance, salt spray, h | 1000 | ASTM B 117 |
| QUV weatherometer UV-A | 5000 | ASTM G 53 |
| QUV weatherometer UV-B | 2000 | |
| Heat resistance, intermittent, °C | 100 | |
| Permeability, hours | 1000 | ASTM G 85-A5 |
The gloss level can be changed to a certain degree by agreement.
The PURAL coating was developed by Rautaruukki. It is particularly recommended for roofs that need good resistance to weathering.
Sheet coated with PURAL can be covered and formed by conventional methods. The coating may limit forming options. It is important to use the right tools and to keep them in suitable condition. Care must be taken not to damage the coating during handling.
Suitable cleaning agents must be used on PURAL-coated surfaces; strong organic solvents will damage the coating.
Used properly in a normal environment and with correct maintenance, a PURAL coating can last for several decades. Reaching that service life requires attention and maintenance. Cut edges may also need to be covered with a special coating. The time to first maintenance varies from 15 to 30 years depending on the environment, the profile, the orientation and the colour. In very strong sunlight, as well as in marine and industrial environments, maintenance may be needed earlier than in a clean rural environment.
Coated sheet is a highly refined material in which the strength and formability of steel are combined with the corrosion resistance and appearance given by the organic coating. Colour-coated sheets are produced on a continuous coating line.
Polyester is a polyester melamine resin coating. There are grades developed for outdoor and indoor use. Thanks to its smooth, soft surface the polyester coating is particularly suitable for interior finishing, but it also suits external walls and roofs. This coating is suitable for interior finishing in food industry buildings and has been certified for that purpose by the Lithuanian National Public Health Centre.
| Dry film thickness µm | 25 |
|---|---|
| Coating structure | smooth |
| Gloss, Gardner 60° | 10…100 |
| Max. continuous ambient temperature °C | 120 |
| Minimum forming temperature °C | -10 |
| Pencil hardness | H |
| Corrosion resistance, salt spray test | 500 h |
| Humidity chamber test | 1000 h |
Matt polyester resists climate and corrosion. Its surface is matt and does not shine. A typical use of matt polyester is tile-effect roofing sheet, which is ideal for residential buildings and for light public and commercial buildings.
Matt polyester is a polyester melamine coating. It gives the surface a matt appearance. The resistance of matt polyester to weather and corrosion is good. Its main feature is the matt surface.
| Dry film thickness µm | 35 |
|---|---|
| Max. continuous ambient temperature °C | 120 |
| Minimum forming temperature °C | -10 |
| Pencil hardness | F |
| Corrosion resistance, salt spray test | 500 h |
| Humidity chamber test | 1000 h |
The Rautaruukki colour range includes 15 standard colours. Shades that are not in the colour chart can be supplied by separate agreement. The reverse side of the sheet is always painted for protection. The type and shade of that surface are chosen by the manufacturer unless agreed otherwise. The reverse side colour is a light grey shade.
Sheet can also be supplied coated on both sides. A different colour can be chosen for each side.
Touching up. Any surface defects that appear during installation and handling must be repaired by touching up. Scratches only should be carefully touched up with a small brush.
Tell us the type of building and the environment and we will suggest a suitable coating.