Meaning
Polymer flow comparison evaluates the shear thinning behavior of thermoplastic resins by measuring melt flow rates under two different test loads. The calculation of high load melt flow ratio divides the flow rate obtained under a high load by the rate measured under a lower standard load. This ratio indicates the molecular weight distribution of the polymer.
It is a critical parameter for selecting resins for demanding extrusion applications.
Shear Sensitivity
Flow behavior at high shear rates differs from behavior at low shear rates due to the alignment of polymer chains. In the calculation of high load melt flow ratio, a higher value shows that the polymer becomes less viscous under intense shear stress. This sensitivity improves processing rates during high-pressure injection molding and blow molding.
Processing Benefits
Extrusion stability depends on the balance between flowability and melt strength during the forming process. A high high load melt flow ratio indicates that the resin flows easily during extrusion while maintaining sufficient strength when exiting the die. This performance reduces the occurrence of defects such as parison sag in blow molding.
Quality Assurance
Resin consistency is verified by checking the molecular properties of incoming polymer batches. Monitoring the high load melt flow ratio prevents processing interruptions by catching batch-to-batch variations in the resin structure. This simple check ensures consistent molded part quality.
