Japan has developed a surface reforming technology to improve the bonding strength of aluminum alloy and resin

A few days ago, Professor Teruhito Kanaya from Okayama University of Science, Japan, and Professor Hino Minoru from SERTEC Nagata, Okayama Industrial Technology Center, Hiroshima Institute of Technology, etc., developed a surface reforming technology that can improve the bonding strength of aluminum alloy and resin "Multilayer Film Anodizing".

When the aluminum alloy and high-performance resin are joined by epoxy adhesive, the strength is about 4 times higher than that of sulfuric acid anodized aluminum, and 95 times higher than that of no treatment. Due to its excellent weather resistance, it is expected to be used as parts of transportation equipment under severe environmental conditions, such as in-vehicle electronic control units (ECUs).

Generally, the single-layer anodized (acid-resistant aluminum) coating is multi-layered, taking into account both adhesion and corrosion resistance. Two types of anodic electrolysis are applied to the aluminum alloy, and the multi-layer oxide film formed on the surface ensures the corrosion resistance of the lower layer, and the adhesive flows into the fine unevenness of the bonding surface, and the fixing effect after hardening improves the adhesion. This upper part has a higher bond with the resin. In addition, it has heat dissipation, and it is difficult to peel off even in high-temperature and high-humidity corrosive environments.

The new technology is based on acid-resistant aluminum, which is less expensive than electroplating materials. The processing device only needs to be added to the usual equipment, and it is fully automated. In addition, the epoxy adhesive can also be replaced by thermoplastic synthetic elastic rubber to improve the resistance of the thermal cycle test.

Further reading

According to the "2013 Patent Application Technology Trend Survey Report" released by the Japan Patent Office, Japan ranks first in the number of joining technology patent applications. When developing joining technology, it takes a huge amount of effort to establish the technology until sufficient peel strength is achieved, and it takes a long time before it can be applied, so this is an area that is rarely entered by companies looking for short-term profits.

There are several technologies that can be used to firmly bond resin and metal. For example, Japan's Taisei PLAS developed in the early 2000s by setting small grooves (micropores) on the metal surface and injecting resin here to obtain Anchoring effect. Japanese circuit board manufacturer MEC has realized the practical application of the technology of bonding resin by using metal treatment of chemicals.

In addition, some companies use other methods to set small holes on the metal surface. One of the methods is to use a laser, that is, first carefully irradiate the laser to melt the metal surface, and then cut the groove. Some companies have also tried to use anodic oxidation treatment (acid-resistant aluminum treatment, the joint object is limited to aluminum alloy).

In addition, in addition to resin and metal bonding, there are also technologies for bonding dissimilar resins. For example, Japan Polyplastics has developed a technology to obtain an anchoring effect through tiny pits on the bonding surface. This technology is envisaged to bond glass fiber reinforced plastics. Resin-based composite materials use a laser to melt the surface of a molded resin product (called a primary material) and cut fine grooves on it.