Adhesion Enhancement of Chlorosulfonated Polyethylene via Self-Interface Roughening on Aluminum Substrate

The adhesion of chlorosulfonated polyethylene (CSM) to aluminum (Al) and its adhesion mechanism was investigated. The lap-shear strength between CSM and Al was nearly 3 times higher than that between chlorinated polyethylene (CPE) and Al, suggesting that the chlorosulfonyl (SO₂Cl) group enhances the adhesion strength. The CSM-Al interfaces were analyzed using electron energy loss spectroscopy with scanning transmission electron microscopy (STEM-EELS), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results show that the CSM creates a rough interface with a thick oxide layer containing Al(OH)₃ simultaneously in the bonding process. Such an increase in the interfacial roughness is considered to result from the electrochemical reaction of Al mediated by the interaction between the free chloride ions detached from the SO₂Cl group and the Al oxide layer. The insoluble adsorbed layers of CSM and CPE on Al were also characterized by ellipsometry. CSM is more likely to contain loosely adsorbed polymer chains. The loosely adsorbed polymer chains behave as connection points between the Al substrate and bulk polymer chains, thereby enhancing the adhesion strength. SO₂Cl-containing polymers may offer a new type of adhesive material that does not require surface pretreatment of adherent.