Melt Flow Index (MFI) Measurement
In order to investigate the rheological properties of the produced masterbatches and compounds, the relative melt flowability or melt flow index (MFI) is measured based on the capillary viscometer method, according to ASTM 1238 or ISO 1133. Melt flow index unit (MFI) is defined as the mass of molten polymer in garm flowing in ten minutes through a capillary of a specific diameter and length by a pressure applied via prescribed alternative gravimetric weights for alternative prescribed temperatures. Therefore MFI standard unit is g/10 min. The melt flow index is inversely related to the melt viscosity; so thath it decreases as the average molecular weight of the polymer increase and consequently the polymer melt viscosity increase. Higher melt flow index indicates greater fluency at processing temperatures. It is primarily intended to represent rheological properties as a measure of extrudability. In general, with increasing melt flow index, tensile strength, tear strength, softening temperature and polymer toughness are somewhat reduced.