English Abstract

Adhesion Between Cured Silicone Rubbers

Hidetoshi HIRAHARA *1
Katsuhito MORI *2
Takahiro KUDO *2
Yusuke MATSUNO *2
Kunio MORI *2
*1:Graduate School of Engineering, Iwate University, Morioka, Japan
*2:Sulfur Chemical Laboratory Inc., Ueda, Morioka, Japan
Nippon Gomu Kyokaishi,(2013),86(11),327-332 Original Paper in Japanese

The adhesion of the cross-linking silicone rubbers (CSR) has been investigated to clarify the effect of the peel strength on corona discharge treatment and adhesion condition. The CSR with each other adhesion at the room temperature adhered in a short time so that corona discharge energy was higher. CSR adhered products obtained, gave a very high peel strength, as well as cohesive failure in a peel test. From the surface analysis result of XPS (X-ray photoelectron spectroscopy), it was found to be dependent on the number of CSR Si-OH groups after corona discharge treatment. The adhesion process of temperature and lapse of time influenced the surface chemical properties on CSR treated corona discharge. As for the effect of elapsed time on the adhesion between CSR after corona discharge treatment until the adhesion process, in the case of the corona discharge energy of 27 kJ/m2, it is believed that the polarity of the processed CSR surface causes inversion of polar groups (Si-OH) and non-polar groups (Si-CH3) at the nm level by the polarity matching with air. The longer is the time in contact with the air, the more Si-CH3 groups are thought to be present on the outermost surface. It is also believed that the formation of a chemical bond at the interface needs for Si-OH groups to be inverted and appear on the outermost surface, and the temperature rise of the adhesive will increase its probability. On the other hand, In the case of 272 kJ/m2, the degrading peel strength after 1h is attributed to be the decomposition of main and side chain of the rubber increasing the amount of Si-OH groups, the condensation reaction of adjacent Si-OH groups with each other increasing cross-linking density of the CSR surface, the amount of Si-OH groups decreasing with a lapse of time, the contact area decreasing due to hardening of the CSR surface and the diffusion of low-molecular siloxane components into the outermost surface.

Keywords: adhesion, silicone rubber, silanol, siloxane chemical bonds, polar matching, corona discharge treatment