Analytical Testing Methods for Quantifying Recycled Content in Polyolefin Compounds
Accurate quantification of recycled polyolefins requires combining DSC thermal integration, high-temperature GPC, ICP-MS trace metals, and melt rheology sweeps.
Rotational Rheology
Meaning
Testing technique that measures the viscous and elastic properties of polymer melts under varying shear and temperature profiles. Resin producers and compounders use this method to evaluate polymer structure and processing behavior. This test is useful for understanding how resins will behave in extrusion and moulding.
Viscous Response
The analysis is performed by placing a polymer melt between two plates and rotating one plate relative to the other. This movement generates a shear stress that is measured as a function of the rotation speed and temperature. Sourcing teams use rotational rheology to determine the viscosity profile of the resin under different shear rates.
Tooling Assessment
This rheological data is used by tooling designers and process engineers to optimize mould filling and gate placement in injection moulds. If the viscosity is too high at the moulding temperature, the polymer will not fill the cavity, causing short shots. This testing helps moulders simulate and prevent these filling defects before the tool is built.
Molecular Architecture
The elastic and viscous curves generated by this test provide information about the molecular weight distribution and polymer branching. High elasticity at low shear rates indicates a broad molecular weight distribution or long-chain branching, which improves melt strength during extrusion. This detailed profiling allows resin buyers to verify the consistency of incoming resin lots.