Compounding of thermosets in continuous kneaders

Various rheological and ultimate properties of thermosetting resins are strongly dependent upon the thermomechanical history that the resin is subjected to during the compounding step. Besides the considerations of the dispersion and homogeneity of various ingredients in the compound, thermosetting resins can easily crosslink to some extent during compounding. In this study, a Buss Continuous kneader, Model PR 200 was employed to compound a phenol–formaldehyde molding powder. The operating conditions in the continuous kneader were varied systematically, and samples were collected. The processability behavior of the resin samples were characterized employing the eccentric rotating disc (ERD) flow in conjunction with a Rheometrics Mechanical Spectrometer, squeezing flow under constant pressure, and torque rheometry, utilizing a Brabender Plasticorder. The extent of curing of resin samples were further determined by acetone extraction. It is shown that the stability of the thermoset compounding rate, temperatures, and power consumption, strongly depends on the operating conditions selected. Furthermore, unstable operation invariably leads to the premature curing of the thermosetting compounds during the compounding operation. The premature curing of the compound adversely affects its flow, curing, and processability behavior. Copyright © 1986 John Wiley & Sons, Inc.