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D2400-99 – Standard Test Method Technical Guide
This specification governs the requirements for black and yellow varnished woven cloth and tape used primarily as electrical insulation. The base fabric combines poly(ethylene terephthalate) (PET) yarns in the warp direction with glass yarns in the filler direction, coated with an oleoresinous varnish. All values are stated in inch-pound units, which are regarded as the standard.
🧵 Materials and Construction
The base fabric construction is strictly defined to ensure uniform electrical and mechanical properties. The fabric has a nominal thickness of 0.004 in. (0.10 mm) and employs the following yarn specifications:
| 🔧 Parameter | 🟦 Warp (Polyester) | 🟩 Filler (Glass) |
|---|---|---|
| 📏 Yarn Type | 140 denier continuous filament | ECG-150-1/0 yarns |
| 🌀 Twist | 5 turns per inch | — |
| 📐 Thread Count (per in.) | 32 / in. (12.6 / cm) | 28 / in. (11.0 / cm) |
⚠️ Splices and Nonconformities: The material must be free from wrinkles, blisters, and imperfections that detract from its insulation value. Splices must be pre-approved by the purchaser and flagged appropriately. Rolls longer than 6 yd may contain no more than one splice per 100 yd; rolls of 6 yd or less must contain no splices.
⚡ Performance and Testing Requirements
Electrical and mechanical values must comply with specific limits provided in Table 1 of the standard. Sample quantities and judging procedures follow Practice D3636, while specific test methods refer to D295 and D902 for flexible coated fabrics.
The varnish film is critically evaluated for resistance to mineral insulating oil (Specification D3487). The film must show no evidence of blistering or disintegration, and the test oil must not become turbid.
💡 Oil Resistance Interpretation: Slight, evenly spaced swelling of the film between yarns is typical for freshly coated goods. This pattern is distinct from random, true blistering which indicates product failure. Proper testing procedure is critical to differentiating these conditions.
📐 Dimensional Specifications
Thickness requirements are selected according to the values in Table 2 of the standard and must be specified in the purchase agreement. The material must also meet stringent width tolerances, which vary based on the nominal width of the tape:
| 📐 Nominal Width (W) | 🎯 Tolerance (±) |
|---|---|
| W ≤ 1 in. (25 mm) | 1/32 in. (0.8 mm) |
| W > 1 in. (25 mm) | 1/16 in. (1.6 mm) |
All ordering information must clearly define the nominal thickness, width, length, and other specifics such as surface type (greasy or dry) and packing method (dry or in oil) as outlined in Section 4 of the specification.
❓ Frequently Asked Questions
🔍 What is the base fabric construction for this varnished cloth?
The base fabric has a nominal thickness of 0.004 in. (0.10 mm) with a warp count of 32 threads per inch and a filler count of 28 threads per inch.💡 What are the available color options for the varnish coating?
This specification covers both black and yellow color styles as selected by the purchaser.⚡ How is the material tested for oil resistance?
The varnish film is tested in mineral insulating oil per Specification D3487. It must show no blistering or disintegration, and the test oil must not become turbid.📌 What information must be included in an order for this material?
Orders must specify the color, nominal thickness, width, length, type of surface (greasy or dry), core size, packing type (dry or in oil), number of rolls per package, and marking details.