Rubber surface treatment method before bonding

The surface of general rubber materials is relatively smooth, and it needs to be mechanically or chemically treated to increase its roughness in order to achieve higher mechanical strength.

Rubber can be divided into two major categories of natural rubber and synthetic rubber. Synthetic rubber can be divided into neoprene, chlorosulfonated polyethylene rubber, styrene-butadiene rubber, butyl rubber, ethylene propylene rubber, nitrile rubber, polysulfide rubber, polyurethane rubber, silicone rubber and fluorine rubber and other varieties. Among them, the silicone rubber and fluorine rubber have saturated molecular structures, large chemical inertness, low surface energy, and difficult to bond. Currently, a method of applying a layer of a silane treatment agent is generally used.

[method 1]
This method is a grinding method.
For natural rubber, lightly grind it with a brush, blow off the fine particles, and wipe with toluene or acetone.
For synthetic rubber, the surface is first washed with methanol, then ground with fine sand, washed with methanol, and dried.

[Method 2]
This method is a sulfuric acid method.
The natural rubber is soaked in concentrated sulfuric acid for 10-15 min. After the hard surface is formed, it is washed with distilled water (or washed with 5-10% ammonia for 5 min before washing) and dried at room temperature. Then bend the rubber to make the surface cracks, increase the surface area and improve the bonding strength.
Synthetic rubber is first wiped with methanol, then immersed in concentrated sulfuric acid for 10-15 minutes, and then washed with distilled water. Re-use 28% ammonia solution, immersed at room temperature for 5-10min, and then washed with distilled water. And repeated bending, so that the surface cracks.

[Method 3]
This method is suitable for silicone rubber.
After roughening the surface, the raft is skimmed. It was then treated with a 1% solution of tetrachlorosilane in toluene for 10 minutes and allowed to dry.
Alternatively, after roughening, degreasing, brushing with 5-10% t-butyl titanate in dichloroethane, air dry.
Alternatively, after roughening and degreasing, apply a layer of the following solution:
Vinyltriethoxysilane 100 Dibenzoyl peroxide 5 Boric acid 0.5

[Method 4]
This method is suitable for fluorine rubber.
After suitably roughening the surface with wooden pestle, dip for several minutes at room temperature in the following solution:
Acetylene sodium (or lithium acetylide) 6 Ammonium hydroxide 1000
Take out the water and dry it.
Alternatively, a layer of propylene triethoxysilane is applied and dried for 30 minutes.

Source: 21st Century Fine Chemicals Network