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D1795-13 – Standard Test Method Technical Guide
📐 Scope and Significance
This test method, ASTM D1795-13 (Reapproved 2021), specifies the determination of intrinsic viscosity for purified celluloses, including bleached wood pulps, cotton linters, and regenerated cellulose. It is limited to samples with an intrinsic viscosity of 15 dL/g or less. The method is sensitive to cellulose degradation from thermal, chemical, or photochemical effects during processing or purification. Intrinsic viscosity values can be converted to degree of polymerization (DP) or intrinsic fluidity for further analysis.
⚙️ Test Procedure and Apparatus
A weighed sample is dissolved in 0.5 M cupriethylenediamine hydroxide solution. The viscosity of the solution and the solvent is measured at 25°C using a calibrated glass capillary viscometer, such as the Cannon-Fenske or Ubbelohde type. For Cannon-Fenske viscometers, an outflow time of at least 80 seconds is required to avoid kinetic energy corrections. The relative viscosity is calculated, and the intrinsic viscosity is obtained from a reference table provided in the standard.
📊 Key Measured Properties
The intrinsic viscosity serves as a measure of cellulose degradation and can be used to assess the effects of processing conditions. Solutions of cellulose are non-Newtonian; however, under the conditions specified (low concentrations and molecular masses), the rate-of-shear effect is assumed negligible for referee purposes. For research or other conditions, this assumption may not apply, and additional considerations are beyond the scope of this test method.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Solvent | 0.5 M Cupriethylenediamine hydroxide |
| Temperature | 25°C |
| Viscometer Type | Glass capillary (Cannon-Fenske, Ubbelohde) |
| Minimum Outflow Time | 80 seconds (Cannon-Fenske) |
| 🟦 Material | 📐 Intrinsic Viscosity Limit |
|---|---|
| Purified celluloses | ≤ 15 dL/g |
| Native celluloses | Exceeds 15 dL/g (not applicable) |
⚠️ Safety Alert: The user must establish appropriate safety, health, and environmental practices. Cupriethylenediamine hydroxide is a chemical hazard; handle with care and follow regulatory guidelines.
💡 Technical Tip: To minimize kinetic energy corrections, ensure the Cannon-Fenske viscometer has an outflow time of at least 80 seconds. A size 100 viscometer is typically used for this standard.
❓ Frequently Asked Questions
🔍 What is the scope of this test method?
This test method covers the determination of intrinsic viscosity for purified celluloses such as bleached wood pulps, cotton linters, and regenerated cellulose, with an intrinsic viscosity of 15 dL/g or less.
💡 How is the intrinsic viscosity determined?
A weighed sample is dissolved in 0.5 M cupriethylenediamine hydroxide solution, and the viscosity is measured at 25°C using a calibrated glass capillary viscometer. The relative viscosity is calculated and the intrinsic viscosity is read from a table.
⚡ What are the limitations regarding flow behavior?
Cellulose solutions are non-Newtonian, but for samples within the specified limits, the effect of rate-of-shear is assumed negligible for referee purposes. This assumption may not be valid for research or other conditions.
📌 Why is temperature control important?
The viscosity is determined at 25°C, and exact temperature control is crucial for accurate results. Certified thermometers according to ASTM E1 or E2251 are recommended.