calculating intrinsic viscosity from melt flow index

A series of calibration standards (polymers with known molecular weight) are also run through the column, which allows correlation of the elution time to a molecular weight. Exiting the column, the size-separated chains are effectively ‘counted’ by a refractive index detector according to their elution time from the column. The solution is injected into a packed column containing a distribution of pore sizes which separate the polymer chains by size. In GPC, a dilute solution of the analyte in question is prepared using a good solvent for the analyte to ensure good dissolution and expansion of the polymer chains in solution. GPC is the most commonly used technique for determination of molecular weight. CPG offers molecular weight analysis using GPC, Dilute Solution or Intrinsic Viscometry (IV) and Melt Flow Index (MFI). There are a variety of analytical techniques used to characterize molecular weight in polymers, each providing useful information about the influence of molecular weight on the measured properties. Standards can be obtained from appropriate standard authorities.The molecular weight of a polymeric or biological material usually has a direct effect on its mechanical properties, thermal behavior, and viscosity characteristics. **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

Calculating intrinsic viscosity from melt flow index