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.
Condition F
Meaning
High pressure measurement conditions describe the parameters for testing the flow of high molecular weight polyethylene resins. Testing under condition f uses a temperature of 190 degrees Celsius and a high load of 21.6 kilograms. This specific load allows for the characterization of materials that would flow too slowly under lighter weights.
It identifies the shear thinning behavior of polymers that are otherwise difficult to process.
Weight Influence
Using a load ten times greater than the standard baseline reveals the flow characteristics of extremely viscous grades. Higher mass during condition f testing forces the polymer chains to slide past each other more easily. This effect mimics the high pressures found inside the barrel of an injection moulding machine.
Grade Comparison
Different resin types respond in unique ways to the application of such a large force. A batch that shows a high flow rate under condition f may still be unsuitable for thin wall moulding if its low load viscosity is too high. Comparisons between these two points help moulders understand the processing window of the material.
Resins used for large extrusion blow moulding parts often rely on this specific test.
Testing Boundary
Resins with very low molecular weights often extrude too quickly for accurate measurement under these circumstances. When the material flows out in a few seconds, the results of condition f become unreliable and prone to human error. Consistent results require a material that resists flow enough to be timed accurately.