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D1578-93 – Standard Test Method Technical Guide
📐 Skein Preparation and Test Options
This test method, designated D1578‑93 (Reapproved 2022), covers the determination of the breaking strength of yarn in skein form. It is applicable to spun yarns, single or plied, from any fiber or blend, but is not suitable for yarns that stretch more than 5% when tension is increased from 2.5 to 7.5 mN/tex (0.03–0.08 gf/denier). The method provides three options based on reel perimeter, number of wraps, and machine speed or time‑to‑break:
- Option 1: 80, 40, or 20 turns on a 1.50 m (1.5‑yd) reel, broken at 300 mm/min (12 in./min). This is the general US practice.
- Option 2: 50 turns on a 1.00 m (1‑yd) reel, broken at 300 mm/min (12 in./min). Used for woolen yarns.
- Option 3: 50 turns on a 1 m reel, broken in 20 s. Proposed by ISO for international use.
Note: Metric reels with 1 m and 1.125 m circumferences give about 1% difference in data; ISO uses a 1 m circumference reel.
| 🟦 Option | 📏 Reel Perimeter | 📐 # Wraps | ⚡ Speed or Time |
|---|---|---|---|
| 1 | 1.50 m (1.5 yd) | 80, 40, or 20 | 300 mm/min (12 in./min) |
| 2 | 1.00 m (1 yd) | 50 | 300 mm/min (12 in./min) |
| 3 | 1 m | 50 | 20 s time‑to‑break |
⚙️ Test Procedure and Speed Selection
The test requires winding yarn into skeins on a reel of the specified perimeter and wraps. The skeins are mounted on a tensile testing machine conforming to Specification D76. For Options 1 and 2, the cross‑head speed is 300 mm/min (12 in./min). For Option 3, the machine is set to achieve break in 20 s. Breaking strength is recorded as the maximum force observed, in units of force (N, kgf, etc.).
This method is often combined with linear density determination (Test Method D1907) on the same skeins; special reeling precautions are noted in the standard. Conditioning of all skeins must follow Practice D1776 (21 ± 1 °C, 65 ± 2% RH).
🚫 Not for Stretchable Yarns: Do not use this method for yarns that stretch >5% under the specified tension range. Such yarns require single‑strand testing per D2256.
📊 Key Measured Properties and Calculations
The primary measured value is the breaking strength (force). From this, two derived properties are calculated:
- Skein Breaking Tenacity: breaking force divided by linear density (typically mN/tex or gf/denier).
- Skein Break Factor: a composite value combining breaking strength and yarn number, useful for comparative purposes.
Definitions and equations are given in Terminology D4849 and in the standard text.
| 🟦 Property | 📐 Formula | 🎯 Units |
|---|---|---|
| Skein Breaking Tenacity | Breaking force ÷ Linear density | mN/tex or gf/denier |
| Skein Break Factor | Breaking strength × Yarn number | Various (e.g., lb·yd/lb) |
🔧 Practical Tip: Calibrate the tensile tester and verify the speed. For Option 3, the break must occur within 20 s ± 3 s. Always condition skeins before testing to avoid moisture effects.
❓ Frequently Asked Questions
🔍 What types of yarns can be tested with D1578?
This method is intended for spun yarns (single or plied) of any fiber or blend, except those that stretch more than 5% under the specified tension increase.
💡 Which option is recommended for international testing?
Option 3 (50 turns on a 1 m reel, broken in 20 s) is the ISO‑proposed method and is recommended for global harmonization.
⚡ Can I combine skein breaking strength with linear density testing?
Yes, the standard explicitly allows combining with Test Method D1907 using the same skeins, but special reeling care is required to maintain accuracy.
📌 How does skein testing differ from single‑strand testing?
Skein testing measures the collective breaking strength of multiple strands simultaneously, giving an average. Single‑strand testing (D2256) measures individual yarn strength and elongation.