Standard Melt Flow Test Load Selection Criteria for Polyethylene Sourcing
Polyethylene sourcing requires specifying exact test loads, temperatures, and standards to isolate molecular structure and enforce contractual lot consistency.
Method a Mass Flow
Meaning
Gravimetric melt flow testing measures the mass of a polymer extruded through a standard die over a timed interval. Use of method a mass flow is common for materials with flow rates between 0.15 and 50 grams per ten minutes. It requires the operator to manually cut the extrudate at precise time steps and weigh the samples on an analytical balance.
This procedure stops being effective for high flow resins where manual cutting becomes inaccurate.
Melt Indexing
Resistance to flow is quantified by the weight of the material collected. A high mass result from method a mass flow indicates a low viscosity polymer that will fill moulds easily. Lower mass values point to high molecular weight resins that offer better mechanical properties.
Operational Procedure
Loading the resin into the heated barrel must be done consistently to avoid air entrapment. The process for method a mass flow uses a piston to apply a standard weight to the melt. Operators use a stopwatch to ensure the cut interval is exact.
Testing Boundary
Variations in cutting technique can introduce errors into the final result. Resins with very high flow rates are rarely tested using method a mass flow because automated displacement is more accurate. For standard quality checks on incoming virgin resin, this manual approach provides a cost effective verification of the material grade.