UPGRADING RECYCLED HDPE BY RHEOMETER-CONTROLLED CROSS-LINKING

An in-line rheometer previously described was evaluated for use in the upgrading of post-consumer, recycled HDPE. Feed resin of variable mel t index was brought to a preset, uniform viscosity by peroxide induced crosslinking in a twin-screw extruder. Closed loop control was demons trated using the rheometer as a viscosity sensor. Set-point tracking w as achieved using PID-IMC, Dahlin and minimum variance (MV) controller s. The Dahlin controller showed the best load rejection.