It is discussed in the present paper the relation between improvement of wettability of aluminium with the chemical treatment on the surface and maximizing on the wood and aluminium gluability.
As test materials, BUNA plywood (three ply, equal consruction, 3 mm of thickness, 10 percent moisture content) and aluminium plates, 0.8 mm and 0.1 mm thick, were used.
The surface of aluminium plate was wiped with an acetone wet cloth and treated as follows.
Cleaning treatment : ---Aluminium plates soaked for 7-12 minutes into solution which was prepared by mixing 3.6 parts distilled water at 70-80℃. Then, it was washed with cold water and dried in the air.
Etching treatment : ---Aluminium plates soaked for 20 minutes into solution which was prepared by mixing 1 part sodium dichromate, 10 parts sulphuric acid and 30 parts distilled water at 60-65℃. Then, it was washed with cold water and dried in the air.
Some parts of the plates were recived either of the two treatment and other parts both in this order.
Wettability of aluminium plate was measured by the inclined method and droplet method with distilled water.
The treated aluminium plate and plywood were glued together with epoxy resin adhesive, nitril-phenol adhesive or neoprene-phenol adhesive. Tensile shear strength test for plywood was applied for the sandwich materials with the core of the aluminium plate, 0.8 mm thick(Fig. 1). Peel strength test was carried out with 0.1 mm thick aluminium plate according to ASTM D 903-49.
The gluing conditions were as follows : glued spread 140g/m^2 (aluminium surface spread), open assembly time ---20-25 minutes (nitril-phenol and neoprene-phenol) or 3-5 minutes (epoxy resin), pressure ---7 kg/cm^2 curig temperature ---25℃ and curing time ---24 hours. Also, the epoxy resin adhesive was cured at 80℃ for one hour.
The results obtained are shown in Fig. 4-7. The following conclusion may be drawn from these experimental results.
1 ) The surface treatment of aluminium plate improved the wettability and gluability. The etching treatment had the most important effect on the improvement of wettability and gluability.
2 ) The cosine-contact angles of water with aluminium as measured by the inclined plate method support the same conclusion.
3 ) Use of the epoxy resin adhesive resulted in the largest tensile shear strength and the least peel strength, while that of the nitril-phenol adhesive gave largest peel strength.