ASTM D1243: Dilute Solution Viscosity of Vinyl Chloride Polymers
Representative Infinita Engineering Visual explaining the four-step workflow for Astm D1243 Viscosity Vinyl Chloride Polymer.What Is ASTM D1243?
ASTM D1243 is the Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride Polymers. It determines inherent viscosity (logarithmic viscosity number) of PVC resin dissolved in cyclohexanone — a value directly related to the average molecular size of the dissolvable portion of the polymer, and therefore a key quality and grade-differentiation metric for PVC resin producers.
Sample Preparation
Duplicate resin samples of 0.2600 +/- 0.002 g (moisture content under 0.1%) are weighed into a 100 mL glass-stoppered volumetric flask. The flask is filled with 50-70 mL of cyclohexanone to thoroughly wet the resin and prevent lump formation, then brought to volume, producing a 0.2% concentration solution.
Test Procedure
- Dissolve the weighed resin sample fully in cyclohexanone at the specified concentration, using controlled heating and stirring as needed
- Using a suspended-level Ubbelohde-type viscometer (commonly a Size 1), measure the flow time of pure cyclohexanone solvent at 30C
- Measure the flow time of the resin solution under identical conditions
- Repeat measurements until they agree within the standard’s required precision (typically within 0.1%)
- Calculate inherent viscosity from the ratio of solution to solvent flow times and the solution concentration
Applicability
The method is limited to vinyl chloride polymers that form clear, uniform solutions at the 0.2% test concentration — resins that don’t dissolve cleanly at this dilution fall outside the method’s scope.
Also Read – Hydrophobic Contamination Testing on Glass: Detection, Methods & Standards
Industry Specifications Referencing ASTM D1243
- ISO 1628-2: international equivalent, though technically not identical to D1243
- ASTM D3591: related method for determining logarithmic viscosity number of PVC in formulated (compounded) products, requiring extraction of additives before testing
- ASTM D2124: companion method for analyzing PVC compound components via infrared spectrophotometry
Conclusion
Inherent viscosity by ASTM D1243 remains the standard way PVC resin producers and converters communicate molecular weight and grade — a single number that correlates directly with processability and end-use mechanical performance, making it one of the most frequently specified QC checks in PVC resin supply agreements.
What does ASTM D1243 measure? The method determines inherent viscosity, also called the logarithmic viscosity number. This value indicates how a dissolved vinyl chloride polymer affects the flow behavior of a dilute solution.
Which polymers can be tested? The method is primarily used for vinyl chloride polymers, including suitable PVC materials. It is limited to polymers that form clear and uniform solutions at the specified test dilution.
How is the test performed? A measured quantity of polymer is dissolved in cyclohexanone. The flow times of the polymer solution and pure solvent are measured using a calibrated capillary viscometer under controlled conditions.
Why is cyclohexanone used? Cyclohexanone is the solvent specified by ASTM D1243 for dissolving vinyl chloride polymers. Consistent solvent purity and handling are important for obtaining reliable viscosity results.
What is inherent viscosity? Inherent viscosity is calculated from the relative flow behavior of the polymer solution compared with the pure solvent. It provides an indirect indication of polymer chain size in solution.
Other Categories
