Analysis of mixing during melt-melt blending in twin screw extruders usingreactive polymer tracers

Mixing during melt-melt blending of segregated polypropylene melt streams i n a co-rotating twin screw extruder was experimentally investigated. The mi xing limited reaction between two polymer reactive tracers, which are termi nally functionalized polyolefin oligomers, was used to determine the mixing performance of a kneading block section. The selected functional groups we re succinic anhydride and a primary amine, and Fourier-Transform Infrared S pectrometry F-IR) was used to determine the anhydride conversion. In the ab sence of interfacial tension, the reaction conversion was directly related to the amount of interfacial area generated. Experiments were completed to study the effects of operating conditions, kneading block design, and polym er material properties. The screw speed effect was observed to be non-linea r because of competing contributions from shear rate, residence time, chann el fill, and viscous heating. The mixing performance of kneading blocks bac ked by a reverse conveying element was observed to follow the trend of: for ward > reverse > neutral. For each kneading block design, the mixing perfor mance decreased with an increase in polymer viscosity.