How does MFI correlate to the molecular weight of a polymer? At CPG, we often measure molecular weight by gel permeation chromatography or dilute solution viscometry. It is easy to see that lower viscosity materials will result in a higher MFI, since more material can be extruded for a given amount of time. This mass, normalized by time, provides the MFI. The amount of material extruded through the die at the bottom of the annulus is measured by weight for a measured period of time. A plastometer consists of a temperature-controlled cylindrical annulus through which a polymer melt is extruded by pressurization with a weight-loaded piston. This testing is normally performed per ASTM D1238 or ISO 1133 using a plastometer. Standards can be obtained from appropriate standard authorities.The certificate of analysis for polymer resins often includes a melt flow index (MFI) or melt flow rate (MFR), reported as grams of material/10 min under a specified temperature and load. **Please note that this test description is intentionally generic in nature and aimed at providing a descriptive summary to enhance test understanding. Melt flow rate values are calculated in g/10 min.įlow rate = ( 600/t x weight of extrudate ) A timed extrudate is collected and weighed. A weight specified for the material is applied to a plunger and the molten material is forced through the die. Alternatively, comparisons between "good" parts and "bad" parts may be of value.Īpproximately 7 grams of the material is loaded into the barrel of the melt flow apparatus, which has been heated to a temperature specified for the material. Typically, flow rates for a part and the resin it is molded from are determined, and then a percentage difference is calculated. Degraded materials would generally flow more as a result of reduced molecular weight, and could exhibit reduced physical properties. It provides a means of measuring flow of a melted material which can be used to differentiate grades as with polyethylene, or determine the extent of degradation of the plastic as a result of molding. Melt Flow Rate measures the rate of extrusion of thermoplastics through an orifice at a prescribed temperature and load. Melt Flow Index, Melt Flow Rate, ASTM D1238, ISO 1133
0 kommentar(er)
