Slit die rheometry is known since middle of the sixties of the last century aiming at improving pressure drop measurement, avoiding Bagley correction and providing melt temperature measurement in the slit-die [1]. Due to shear dissipation in slit-dies at high shear rates apparent viscosities has to be corrected for temperature. The necessity for this correction and the effects firstly were shown experimentally by Daryanani et.al. [2]. Since end of the seventies of the last century processing machines like extruders and injection molding machines had been adapted with flexible slit die systems for rheological measurements widening the shear rate range to be covered and offering new possibilities to characterize compounds with complex rheological behavior such as wall slipping PVC [11,5], wood plastic composites and rubber compounds. These machine rheometers offered new possibilities in rheological characterization at melt preparing conditions close to processing and the
possibility for precise measurement of pressure drop and temperature in the slit-die. In this contribution the application of slit-die rheometers for thermoplastics and rubbers compounds will be discussed from first systems [1,3,4,5] up to special machine rheometers such as by-pass extrusion rheometers and injection molding machine rheometers [6,7]. Advantages and disadvantages as well as new possibilities in characterizing pressure dependency of viscosity using slit-dies [5,7,10,12] will be pointed out for
thermoplastics and rubber compounds. A new rheological split mold for measuring rubber compounds containing curatives will be presented for the first time. Rheological measurements will be presented for polypropylene, wall slipping PVC and rubber compounds non-containing as well as containing curatives. A special injection mold for slit-die rheometry offers the possibility to widen the shear rate range up to 106 s-1 and to measure the pressure dependency of viscosity up to pressure levels of approx. 600 bars [7,12]. The rheological evaluation of measured apparent viscosity values and the approximation of true viscosity curves takes into account temperature rise due to shearing at shear rates higher than 104 s-1 [9,10,11] according to a method, suggested firstly by Aggassant [8].