Black, toughened ethyl-based instant adhesive. Well suited to plastics, rubbers, metals as well as porous/acidic surfaces.LOCTITE 438 is a black, toughened ethyl-based instant adhesive. It has a fixture time of 10 - 20 secs., high impact resistance and is flexible. It is suitable for bonding plastics, rubber, metals, porous and absorbent substrates and acidic surfaces. Good resistance in humid environments.