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D5647-07 – Standard Test Method Technical Guide
📌 Scope and Significance
This guide covers the determination of the hairiness of most filament and spun yarns using a photo‑electric sensor apparatus. It is not intended for novelty yarns. SI units are standard. Users must establish appropriate safety and environmental practices. The method is not recommended for acceptance testing of commercial shipments due to significant machine variability but is valuable for process control.
Warning: Not for acceptance testing without bias correction. Comparative tests with statistical analysis are required if laboratory results differ.
⚙️ Test Procedure and Measurement Principle
Yarn passes through a photo‑electric device; protruding fibers or filaments interrupt a light beam. The number of interruptions for a specific fiber length over a specified yarn length is counted by a digital voltmeter or computer interface and reported as hairiness. Testing speed and tension may vary by manufacturer, influencing results.
Tip: Use consistent apparatus and settings for internal comparisons. Calibration with standard yarns can mitigate machine‑to‑machine variability.
📊 Key Terminology and Definitions
Key terms from Terminology D4849 relevant to this guide:
| 🟦 Term | 📏 Definition |
|---|---|
| Hairiness | Count of protruding fibers per unit yarn length. |
| Broken Filament | Broken filament protruding from the yarn body. |
| Frayed | Wear leading to numerous protruding fiber ends. |
| Fuzzy | Surface with many short protruding fibers. |
| Loopy | Yarn with loops of fibers on the surface. |
❓ Frequently Asked Questions
🔍 What yarn types can be tested?
Most filament and spun yarns, but not novelty yarns.
💡 Why is the photo‑electric method not for acceptance testing?
Due to variability in results between machines from different manufacturers.
⚡ What equipment is used in the test?
Photo‑electric device with a light beam, digital voltmeter or computer interface, and tension/speed controls.
📌 How is hairiness reported?
As the count of protruding fibers of a specific length per specified yarn length.