USE OF DYE CONTAINING POLYMERIC MICROCAPSULES FOR DETERMINING SHEAR STRESSES

This paper evaluates a method of measuring shear stress, in-situ, in p olymer flows. The rupture response of two different dye containing pol ymeric microcapsules, CM511 and CM567, is examined in both an internal batch mixer and a lab scale single screw extruder (SSE), using ultrav iolet/visible spectrophotometry (UV/VIS), colorimetric analysis (CA) a nd optical microscopy (OM). It is observed that both particles rupture over a wide range of shear stresses and times. In particular, both CM 511 and CM567 begin to rupture at similar to 100 kPa, while complete r upture is only detected for the CM567 at average stress levels greater than or equal to similar to 230 kPa. Complete rupture for the CM511 i s not observed over the average shear stress range investigated. The m icrocapsules further indicate the change in the melting mechanism in a SSE when the processing conditions are changed.