Polyamide and Polyimide Resin

Polyimides are polymers with a noncarbon atom of nitrogen in one of the rings in the molecular chain (Fig. 3.4) [HARP03, p. 432 f.]. Polyamide-imide are members of the same polymer family and contain aromatic rings and nitrogen linkages (Fig. 3.4) [HARP03, p. 432 f.].

Polyamid and polyimide bondings have a higher toughness, thermal resistance and elasticity than phenol resin bondings [KLOC05a, p. 66]. Polyimide bonds have 5 to 10 times the toughness of phenolic bonds and can withstand temperatures of 300 °C for 20 times longer [MARI07, p. 121]. However, the higher price reduces the use of this bonding system type to special applications and to superabrasives [MARI07, p. 121]. Polyimide resin is a dominant bond type for high-production carbide grinding especially for flute grinding [MARI07, p. 121] or for cut-off grinding under cooling lubricant.

3.1.1.1 Epoxy or Urethane Resin

Epoxy or urethane wheels are the softest of resin bonded wheels. With conventional abrasives, they are popular for double disc and cylindrical grinding. However, for

Polyamide-imide

superabrasives, epoxy or urethane bonds appear to be limited to micron diamond grain applications for the glass and ceramics industries [MARI04, p. 413].

Epoxy resins are characterized by their epoxide group which consists of oxirane rings (-CH2-O-CH2-) [HARP03, p. 161 f., 388]. The epoxy resin then is hardened with a fluidic hardener to a polymer [KLOC05a, p. 63, COLL88].