Meaning
Binary liquid solvent mixtures serve within standardized polymer laboratory testing methods to dissolve high-rigidity aromatic polymers for dilute solution viscometry. A sixty to forty weight ratio mixture of phenol 1 2 dichlorobenzene acts as a reference solvent system for measuring the intrinsic viscosity of polyethylene terephthalate and related polyesters. It governs resin receiving inspections and quality verification steps by establishing precise baseline viscosity metrics for incoming virgin pellets.
Application of this mixture stops when non-polyester polymers require non-polar organic solvents or when high-temperature gel permeation chromatography replaces dilute solution viscometry.
Solvent Dissolution
High crystalline melting points and strong intermolecular forces make aromatic polyesters insoluble in standard room-temperature organic solvents. Phenol 1 2 dichlorobenzene provides sufficient solvency at elevated temperatures around 110 degrees Celsius to completely break interchain hydrogen bonding and dissolve solid resin pellets. The phenolic component provides polar solvency while 1,2-dichlorobenzene lowers solvent vapor pressure and prevents rapid volatilization during testing.
Complete polymer dissolution ensures that individual chains separate into isolated hydrodynamic volumes required for accurate viscometry.
Viscometric Measurement
Capillary flow timing using calibrated glass viscometers requires strict temperature control within liquid bath enclosures.
Polymer Degradation Risk
Moisture contamination in polyester samples causes rapid hydrolytic scission when heated inside acidic solvent mixtures. Water molecules react with ester linkages at elevated temperatures, permanently reducing polymer backbone length and distorting intrinsic viscosity test results. Laboratory technicians dry resin samples thoroughly before dissolution in phenol 1 2 dichlorobenzene to eliminate hydrolysis artifacts.
Accurate viscosity data allows injection moulders to distinguish between true raw material defects and process-induced polymer degradation occurring inside hot runner systems.
