Meaning
Mathematical logarithmic relations in solution viscometry express the relationship between relative viscosity and polymer concentration to evaluate intrinsic viscosity at the boundary of infinite dilution. The kraemer equation utilizes the natural logarithm of relative viscosity divided by concentration, modified by a characteristic dimensionless constant. It governs the analytical determination of polymer chain dimensions and molecular weight parameters during raw material quality audits.
The equation ceases to apply when solution concentrations rise into non-dilute regimes where chain entanglements distort linear viscometric behavior.
Logarithmic Form
Logarithmic mathematical formulations offer superior linear stability when evaluating high molecular weight polymers in good solvents. The kraemer equation constant carries a negative value, typically ranging between minus 0.10 and minus 0.15 for flexible polymer systems. Combining Kraemer determinations with Huggins evaluations provides a dual-check mechanism that verifies experimental data accuracy across concentration series.
When calculated constants from both equations fail to sum to approximately 0.50, laboratory analysts identify solvent contamination or incomplete resin dissolution.
Extrapolation Technique
Multi-point dilution plots project logarithmic viscosity numbers back to zero polymer concentration on a coordinate axis.
Viscometric Degradation
Polymer molecular weight measurements obtained through viscosity extrapolation reflect the true chain length distribution of raw resin lots. Moulding processes that subject virgin resin to high shear forces or excessive barrel temperatures break covalent backbone bonds, causing permanent molecular weight reduction. Evaluating regrind materials with the kraemer equation quantifies chain degradation resulting from consecutive heat histories.
Significant drops in intrinsic viscosity indicate severe thermal breakdown, warning moulders that reprocessed resin will exhibit lower impact strength and reduced stress crack resistance compared to virgin material.
