Ceilings, cladding, curtain walls and partitions with aluminium wood finish are often seen in commercial buildings. In the home interior decoration, wood like aluminium doors and windows are very common now, and aluminum furniture with wood grain color has begun to into the market. Comparing with the surface of RAL color, the wood finish is more lively, atmospheric, and close to nature.
So how is this wood grain surface formed? And how to make aluminium look like wood?
There are mainly two methods for forming wood grain on the aluminum surface: SUBLIMATION PROCESS (famous as Decoral), and POWDER ON POWDER PROCESS(famous as Naturall).
SUBLIMATION PROCESS：The transfer of a pigment from a carrier (paper or film) into the prehardened base coated aluminum surface. For this process, the aluminum part to be covered must be in contact over all areas with the carrier which contains the pigment. The transfer of the pigment into the powder coating to create the texture is performed by using heat and vacuum.
POWDER ON POWDER PROCESS: When the base coating on aluminum surface is cured, a second thinly applied and differently colored powder is applied via a matrix, which contains the desired structure formed by very fine holes within the matrix. The second powder, generally in a darker color than the base color falls through the holes of the matrix onto the aluminum surface already covered with the base color. Both layers are being held onto the aluminum by electrostatic forces.
SUBLIMATION PROCESS technology makes the surface smooth, the grain is clear and realistic, and according to various heat transfer paper/film, it can transfer to a variety of realistic wood grain color.
POWDER ON POWDER PROCESS technology has a wood grain feel, and the wood grain is realistic, but the color is relatively simple. If you want to have a wood grain feel by SUBLIMATION PROCESS, you can get it by other machining fabrication, such as shavings, engraving, brushing, etc.
SUBLIMATION PROCESS to get a wood finish on aluminium is the most commonly used technology for aluminium industry in China. FONNOV ALUMINIUM, as a professional aluminum extrusion manufacturer, also has wood grain sublimation production lines and powder coating production lines, would like to introduce how to make wood grain aluminum through the sublimation process.
The mechanism of thermal transfer wood grain formation is the transfer penetration of wood grain ink. The transfer paper with wood grain is closely attached to the surface coating of the aluminum profile. During the curing process, the thermal motion of the ink molecules on the transfer paper is intensified, and the gap between the coating molecules of the surface of the aluminum profile is infiltrated, and the solvent of the ink volatile, most of the ink is combined with the coating to exhibit the wood grain color brought by the transfer paper.
At present, most of the wood grain sublimation process is:
aluminum pretreatment → base-color powder coating & curing → wood grain transfer paper covering → curing → paper removal.
The aluminum material must be pretreated before powder coating spraying, so that can improve the adhesion of the aluminum metal surface to the coating.
The Base-color Powder Coating and Curing:
The powder coating process adopts electrostatic spraying, and the powder coatings that used must be special coatings for wood grain sublimation process. The curing temperature and time of the transfer are determined according to the shape of the transferred aluminum material, as well as the depth of the texture to be transferred. The transfer curing temperature is usually 180 ° C for 10 min. After curing, the coating thickness should ensure the depth of transfer and penetration of the wood grain ink during the transfer process, and the coating film thickness should be basically 60- 80um.
Wood Grain Transfer Paper Covering:
Wrap the aluminum profile which needs to be transferred with wood grain paper, and sticks the paper with the high-temperature adhesive tape to prevent the grain paper. A plastic bag with high-temperature resistance and good airtightness is placed on the paper covered aluminum, and then vacuum is taken from both ends of the plastic plastic bag, so that the plastic bag which is close to the aluminum material presses the wood grain paper to make it closely attached to the aluminum material, the negative pressure is appropriately adjusted according to the shape of the transferred aluminum material and the negative pressure that the plastic bag can withstand, generally 0. 3 MPa ～ 0. 6 MPa.
The wrapped aluminum material is sent to the oven for curing.
After curing, the aluminium profile is pushed out from the oven, and the plastic bag is pulled out from one end of the aluminum material. And finally, the heat transfer wood grain paper is torn off.
This process gives you a clear and realistic wood finish on aluminium. If there are some problems in any step, it may cause the wood grain to be ghosted, unclear, or the surface is not smooth. Therefore, the guidance of the powder coating factory and the wood grain paper/film factory is necessary before production to produce a high-performance wood look aluminum.