Both our mi40 and MI-ROBO 89.16 can perform automated multi-load measurements with only one filling of the barrel as described in ASTM D1238 Procedure D. Without additional effort additional data can be determined. From the results of the melt index measurement with different load weights, the so-called flow-rate ratio (FRR) is calculated. This ratio is a measure for the width of the molecular weight distribution and thus also for the process-relevant shear-thinning behaviour of the polymer.
Relaxation phase after weight change
Conventional multi-weight measurements do not offer a relaxation phase after the weight change. This causes a higher dispersion of measured values compared to single weight measurements (left picture). With the multi-load function (up to 8 weight steps) of the mi40, the material is given sufficient relaxation time after the weight change, which equalizes the influences of the pre-shear. This results in a much better agreement with single weight measurements (picture right).