Meaning
Organohalide chemical reagents dissolve specific high-performance thermoplastics for solution viscosity testing and molecular weight determination. Laboratory technicians handle dichloroacetic acid to dissolve polyesters and polyamides that resist milder organic solvents at room temperature. The compound enables accurate solution viscosity measurement without heating the polymer solution to temperatures that induce thermal degradation.
Its application stops where non-polar resins like polyolefins fail to dissolve or where environmental safety regulations mandate non-toxic solvent systems.
Solvent Mechanism
Dissolution occurs through strong hydrogen bonding and solvation that breaks the intermolecular forces binding semi-crystalline polymer chains together. When preparing polyethylene terephthalate samples, dichloroacetic acid breaks down crystalline domains without hydrolysing ester linkages during the standard testing window. Rapid dissolution prevents chain scission from distorting intrinsic viscosity results.
Miscalibration of solvent concentration alters viscosity readings, leading moulders to misjudge polymer chain length.
Degradation Limit
Chemical stability of the polymer-solvent solution deteriorates over extended residence times or exposed storage. Moisture absorption from ambient air reduces solvent acidity, altering solution flow time through glass capillary viscometers.
Testing Impact
Quality control laboratories rely on solution viscosity data to verify incoming virgin resin lots against technical data sheets. Variations in intrinsic viscosity directly affect melt flow behavior during injection moulding, where lower viscosity increases flash risk at parting lines. Regrind integration often shows reduced intrinsic viscosity due to prior thermal history, which dichloroacetic acid testing quantifies before material enters the hopper.
