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D1720-03 – Standard Test Method Technical Guide
📐 Scope and Terminology
The test method quantifies the volume ratio of hydrocarbon diluent to active solvent required to cause persistent heterogeneity (precipitation) in a cellulose nitrate solution. The end point is strictly defined as the maximum number of unit volumes of diluent that can be added to one unit volume of solvent at a specific concentration.
Definition of Dilution Ratio: The dilution ratio represents the maximum number of unit volumes of a diluent that can be added to a unit volume of solvent to cause the first persistent heterogeneity (precipitation) in the solution. This measurement must be conducted at a concentration of 8 g of cellulose nitrate per 100 mL of combined solvent plus diluent, at a temperature of 25 ± 3°C.
⚠️ Important Note on Concentration: The dilution ratio decreases as the cellulose nitrate concentration at the end point increases. Therefore, the standard mandates an arbitrary concentration of 8.0 g of cellulose nitrate per 100 mL of solvent plus diluent for the measurement.
⚙️ Test Procedure and Materials
The procedure involves titrating a prepared cellulose nitrate solution with a hydrocarbon diluent until the first sign of persistent precipitation occurs. The volume of diluent required is then used to calculate the dilution ratio.
Standard Materials:
- n-Butyl Acetate (90 to 92 %): Conforming to Specification D4615. This serves as the standard solvent.
- Nitration Grade Toluene: Conforming to Specification D841. This serves as the standard diluent.
- Cellulose Nitrate: As defined in the standard procedures, meeting the solubility characteristics outlined in Test Methods D301.
💡 Tip for Accuracy: To determine the effect of a specific solvent, standard cellulose nitrate and toluene should be used. To test a diluent, standard cellulose nitrate and n-Butyl Acetate serve as the reference.
📊 Key Conditions and Applications
The information developed through this test method is instrumental in formulating cellulose-based lacquers and adhesives. By keeping two of the three components (solvent, diluent, or cellulose nitrate) as standards, the effect of