Meaning
Characterization method for investigating the non-linear viscoelastic properties of polymer melts through large amplitude oscillatory shear. While linear rheology probes small deformations, laos exposes the structural response of the polymer chains under conditions similar to actual processing. It reveals information about chain branching and molecular weight distribution.
Waveform Distortion
Stress responses in a non-linear regime deviate from a pure sinusoidal shape when the strain amplitude exceeds a specific limit. Fourier transform analysis of the laos signal identifies higher order harmonics that characterize the melt behavior. Simple viscosity curves miss these details.
Structural Fingerprinting
Molecular architectures respond uniquely to the large deformations imposed during the test. For instance, long chain branching in low density polyethylene creates a distinct signature in the laos data compared to linear polymers. This allows for precise identification of material components in recycled blends.
Analysts use the resulting Lissajous curves to visualize the energy dissipation and storage. Visual representation highlights the transition from elastic to viscous dominated flow.
Process Optimization
High shear environments in extrusion and injection moulding often push polymers into the non-linear zone. Correlating laos results with actual flow defects helps engineers refine die designs and screw profiles. It provides a more realistic map of how the resin will behave under pressure.
