# 4.3.6.3 Flame Treatment

> From: LOCTITE®X Digital Manual for Bonding (https://www.loctitex.com/en/manuals/bonding/4.3.6.3-flame-treatment/)

##### 4.3.6.3 Flame Treatment

Flame treatment increases the bondability of plastic by oxidising the surface through brief exposure to flame. The oxidation proceeds as a free radical mechanism, accompanied by chain scissions and some crosslinking. The functionalities introduced by oxidation are hydroxyl, carbonyl, carboxyl and amide groups, with a typical oxidation depth of approximately four to nine nanometers. Wettability is improved by increased surface energy. The chain scissions on the surface contribute to higher interfacial diffusivity.