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D5650-97 – Standard Test Method Technical Guide
📐 Specimen Geometry and Apparatus Overview
This test method, designated D5650-97 (Reapproved 2007), is specifically designed for measuring the resistance to bending of papers exhibiting low grammage or high flexibility. It is ideally suited for materials with a bending stiffness in the range of 0 to 10 Taber stiffness units.
The standard specifies the use of a Taber-Type Tester configured for this low-stiffness range. The test specimen is precisely defined as a strip 38 mm (1.5 in.) wide. The instrument, whether motor-driven or manually crank-operated as described in Section 6 of the standard, uses a vertically oriented clamp to hold the specimen rigidly during the test.
⚙️ Test Procedure and Operational Mechanics
The operational mechanics of the D5650 test method are tightly controlled to ensure reproducibility. The vertically clamped specimen is deflected through a specific bending angle. The load is applied consistently at a set distance from the clamp to generate a standard bending moment.
⚠️ Instrument Configuration Alert: This test method utilizes the Taber-Type Tester in a modified configuration (0 to 10 unit range). Test results under D5650 have been reported to be as much as 40% different from those obtained using the basic configuration described in Test Method D5342. This method must not be substituted where D5342 is explicitly specified.
Key parameters of the apparatus and test procedure include:
| 🟦 Parameter | 📏 Specification |
|---|---|
| Specimen Width | 38 mm (1.5 in.) |
| Bending Angle | 15° from vertical center line |
| Lever Arm Distance | 10 mm (0.39 in.) from clamp face |
| Stiffness Measurement Range | 0 to 10 Taber Stiffness Units |
| Instrument Drive | Constant speed motor (preferred) or manual crank |
📊 Significance, Data Interpretation, and Regulatory Context
The resistance to bending measured by this method is critical for predicting performance in several end-use applications. The data directly relates to how paper behaves during high-speed mechanical handling in copy machines, wrapping processes, and printing operations. The bending moment is read directly from the instrument scale, from which the resistance to bending is calculated.
Proper testing requires strict adherence to referenced ASTM standards for sampling and conditioning:
| 📐 Standard | 🎯 Purpose in D5650 Context |
|---|---|
| ASTM D685 | Standard practice for conditioning paper and paper products for testing. |
| ASTM D585 | Standard practice for sampling and accepting a single lot of paper. |
| ASTM D1968 | Standard terminology relating to paper and paper products. |
| ASTM E122 | Practice for calculating sample size to estimate lot averages. |
💡 Technical Note on Flexural Rigidity: When testing extremely flexible papers within the 0 to 10 Taber stiffness unit range, ensure the instrument’s pendulum weight and frictionless bearings are properly calibrated. The manual crank and automatic motor-driven models detailed in Section 6 of the standard should yield identical results when correctly operated.
❓ Frequently Asked Questions
🔍 What specific type of paper is best suited for testing under this standard?
This standard is specifically written for papers of low grammage or high flexibility that exhibit a bending stiffness within the range of 0 to 10 Taber stiffness units, as detailed in Section 1.
💡 How is the bending load applied to the test specimen?
The specimen is clamped vertically, and the load is applied exactly 10 mm (0.39 in.) from the clamp. The free end of the specimen is deflected 15° from its vertical center line to determine the bending moment.
⚡ Can I use this test method as a direct replacement for ASTM D5342?
No. Section 1.4 explicitly states that results from this method can differ by as much as 40% from Test Method D5342. You must not use this method where D5342 is specifically mandated.
📌 What are the key application areas that depend on this bending resistance test?
Section 5 of the standard highlights that this property is significant for wrapping, printing, copy machine performance, and high-speed mechanical handling of documents.