Sintering high performance semicrystalline polymeric powders

Poly(ether ether ketone) (PEEK) is a high performance semicrystalline thermoplastic with a glass transition temperature of 143 degrees C. The melting point (Tm) is quoted as 334 degrees C. Because of its high thermal transitions, PEEK, requires high temperatures for processing, at least 370-400 degrees C. It has been determined that under the recommended processing conditions PEEK can undergo branching and eventually crosslinks. An alternative to melt processing PEEK is to apply the powder metallurgy technique of sintering. This involves cold (room temperature) compaction of the polymeric powder, followed by pressure free sintering of the resultant green body. We have reported a process for preparing submicron PEEK particles, and the focus here is on the free sintering of these particles with emphasis on the effects of particle size, sintering temperature, and compaction pressure. The data is evaluated using the two particle model developed by Frenkel as well as the crack healing theory developed by Wool.