Morphology and rheology sensors for in-line and on-line microstructure monitoring in compounding

The need for rapid process adjustment to maintain or achieve a desired product quality has led to the development of in-line and on-line techniques for process monitoring in the plastics industry. In large production setups, any time that a process parameter is changed, or a fluctuation in the process occurs, the time required for off-line analysis to check product quality is long enough for the generation of large quantities of material of unknown characteristics (1). On-line and in-line methods are increasingly in use for several reasons. For example, some applications process materials which may exhibit drastic changes once taken from the process line for off-line analysis, thus presenting challenging sampling procedures. In some other cases, factors such corrosiveness and toxicity preclude the use of off-line methods, and require closed-loop product evaluation techniques. This paper addresses recent developments in in-line/on-line sensors for monitoring blend rheology and morphology to evaluate the extent of mixing and/or reaction in continuous compounding equipment. Areas of possible applications as well as limitations of these sensors are discussed.