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CAN CGSB 4.2 No. 12.1-2016: Breaking Strength of Textile Fabrics – Strip Method
A comprehensive guide to the Canadian standard for determining the breaking force and elongation of textile fabrics using the strip test method.
Introduction
The standard CAN CGSB 4.2 No. 12.1-2016 – Textile Test Methods – Breaking Strength of Textile Fabrics – Strip Method is a key component of the Canadian General Standards Board (CGSB) series for textile evaluation. This method specifies a procedure for determining the maximum force (breaking strength) and the elongation at break of textile fabrics using a strip test configuration. It applies to woven, nonwoven, and coated fabrics, provided the fabric can be cut into strips without fraying excessively.
Unlike grab test methods, the strip method uses a specimen of full fabric width (typically 50 mm) that is raveled or cut to a specified width, thereby assessing the strength of the entire fabric structure. The standard is harmonized with international practices, notably ISO 13934-1, and is widely adopted in textile quality control laboratories across Canada and other regions referencing CGSB requirements.
Tip: When testing fabrics with low fray resistance, consider using a cut strip method (No. 12.2 – Grab Method) if the strip method yields inconsistent results due to edge threads slipping.
Scope and Application
CAN CGSB 4.2 No. 12.1-2016 covers the determination of the breaking force and elongation of textile fabrics using a constant rate of extension (CRE) testing machine. The method is applicable to:
- Woven fabrics (including industrial and apparel textiles)
- Nonwoven fabrics that can be cut into strips without excessive distortion
- Coated fabrics where the coating does not interfere with the strip preparation
- Fabrics that are not sensitive to edge fraying (for fray-sensitive materials, alternative clamp designs or pre-treatment may be required)
Exclusions
- Elastic fabrics (those with high stretch recovery) – use methods for elastomeric materials
- Fabrics narrower than 50 mm (unless otherwise specified)
- Testing of yarns or individual threads (see CAN/CGSB-4.2 No. 12.4)
Important: The results obtained by the strip method are typically lower than those from the grab method because a larger width of fabric is subjected to tension, allowing weaker yarns to influence the overall strength. Always specify the test method when reporting breaking strength values.
Technical Requirements
The standard defines detailed technical parameters for the test equipment, specimen preparation, conditioning, testing speed, and calculation of results. The following table summarizes the key requirements:
| Parameter | Requirement | Remarks |
|---|---|---|
| Test machine type | Constant Rate of Extension (CRE) | Loading rate: 50 mm/min (unless otherwise specified) |
| Specimen width | 50 ± 0.5 mm (raveled strip) or 50 ± 0.5 mm (cut strip) | Raveling: remove warp or weft threads to achieve 50 mm width |
| Gauge length | 200 ± 1 mm | Distance between jaws |
| Preconditioning | 4 hours at 20 ± 2 °C, 65 ± 4% RH | Required for dry testing |
| Number of specimens | 5 warp direction + 5 weft direction | Additional sets for wet testing if needed |
| Wet testing | Immerse in distilled water + 0.1% wetting agent for 20 min | Test within 2 minutes of removal |
| Reporting | Breaking force (N) and elongation at break (%) | Mean, CV, and individual values |
Specimen Preparation
For the raveled strip method, cut specimens at least 70 mm wide and then ravel threads from each side until the width is exactly 50 mm. Ensure the raveling is uniform. For the cut strip method, cut specimens directly to 50 mm width using a sharp template or cutter, avoiding fraying.
Specimens should be taken at least 100 mm from the fabric edge and spaced evenly across the width. In warp direction, avoid selvedge; in weft direction, avoid sections with obvious defects.
Testing Procedure
- Mount the conditioned specimen centrally in the jaws, aligning it perpendicular to the direction of pull.
- Apply a pre-tension of either 0 N (for nonwoven) or approximately 10% of the expected breaking force (for woven, but not exceeding 2 N) to remove slack.
- Start the machine and record force-extension curve.
- Continue until the specimen breaks; record the maximum force and the corresponding extension.
- Repeat for all specimens in warp and weft directions.
Implementation Highlights
Implementing CAN CGSB 4.2 No. 12.1-2016 in a laboratory requires attention to several critical aspects:
Equipment Calibration
The CRE tester must be calibrated according to manufacturer specifications and traceable to national standards. Verification of load cell accuracy (±1% of reading) and elongation measurement (±1 mm) should be performed regularly. Jaw faces should be clean, flat, and provide sufficient grip to prevent slippage without cutting the specimen.
Conditioning and Environment
Fabric samples must be conditioned in the standard atmosphere (20 ± 2 °C, 65 ± 4% RH) for at least 24 hours prior to testing, or until constant mass is achieved. The testing environment must also be controlled within these limits, as both temperature and humidity significantly affect the breaking strength of textiles (especially cellulosic fibers).
Best Practice: Use an automated data acquisition system to capture force-extension data at a minimum sampling rate of 100 Hz. This ensures accurate measurement of breaking force and elongation, particularly for fabrics exhibiting a sharp load drop at break.
Calculation of Results
Breaking force is recorded as the highest force observed during the test. Elongation at break is the percentage increase in gauge length at the point of break. For each direction, calculate the mean, standard deviation, and coefficient of variation. If any specimen breaks within 5 mm of the jaw, a discard is recommended, and an additional specimen should be tested.
Compliance Notes
Compliance with CAN CGSB 4.2 No. 12.1-2016 is often required for textiles intended for federal government procurement in Canada, and for products bearing the Canada Consumer Product Safety Act (CCPSA) marking. Key compliance considerations include:
- Certification: Testing must be performed by an accredited laboratory (e.g., ISO/IEC 17025) to ensure conformity.
- Documentation: Test reports must include the standard designation, specimen type (raveled or cut), direction, conditioning details, and any deviations from the standard (e.g., modifications for fragile fabrics).
- Interlaboratory Comparisons: Regular participation in proficiency testing programs helps validate results.
- Harmonization: CAN CGSB 4.2 No. 12.1-2016 is technically equivalent to ISO 13934-1:1999. Laboratories already using the ISO method can adapt with minimal changes, primarily in reporting format and specimen dimensions (ISO uses 200 mm gauge length and 50 mm width as well, but allows 100 mm width for certain fabrics).
Advisory: Failure to comply with the conditioning requirements can lead to variability of ±20% in breaking strength, especially for hygroscopic materials like cotton or wool. Always monitor and record environmental conditions during testing.
Frequently Asked Questions
Q: What is the difference between the strip method and the grab method in textile testing?
A: The strip method uses a full-width specimen (50 mm) held across the entire jaw face, engaging all warp and weft yarns. The grab method uses a narrow clamp (e.g., 25 mm) on a wider specimen (100 mm), thereby only loading a portion of the yarns. Strip method yields a more accurate assessment of fabric strength, while grab method better simulates the localized stress experienced during certain end-uses (e.g., seams).
A: The strip method uses a full-width specimen (50 mm) held across the entire jaw face, engaging all warp and weft yarns. The grab method uses a narrow clamp (e.g., 25 mm) on a wider specimen (100 mm), thereby only loading a portion of the yarns. Strip method yields a more accurate assessment of fabric strength, while grab method better simulates the localized stress experienced during certain end-uses (e.g., seams).
Q: Why must the raveled strip method not be used for fabrics with low yarn cohesion?
A: When raveling, edge threads may slip or shred, resulting in a specimen that is weaker than the actual fabric. In such cases, the cut strip method (using a sharp die) is recommended, provided that fraying during testing is negligible. Alternatively, a zigzag or serrated clamp may be used to reduce stress concentration at the jaw edges.
A: When raveling, edge threads may slip or shred, resulting in a specimen that is weaker than the actual fabric. In such cases, the cut strip method (using a sharp die) is recommended, provided that fraying during testing is negligible. Alternatively, a zigzag or serrated clamp may be used to reduce stress concentration at the jaw edges.
Q: Can this standard be used for coated or laminated fabrics?
A: Yes, but care must be taken during specimen preparation. Coating might cause sticking to the jaw faces or affect the raveling process. For coated fabrics, the cut strip method is often preferred. The test report should note the coating type and any difficulties encountered.
A: Yes, but care must be taken during specimen preparation. Coating might cause sticking to the jaw faces or affect the raveling process. For coated fabrics, the cut strip method is often preferred. The test report should note the coating type and any difficulties encountered.
Q: How does CAN CGSB 4.2 No. 12.1-2016 relate to ASTM D5035?
A: ASTM D5035 is the equivalent test method in the U.S. Both standards share the same principle (CRE machine, 50 mm strip width, 200 mm gauge length) but differ in conditioning—CGSB requires 65% RH, ASTM uses 65% RH as well (standard atmosphere) but may allow 50% RH for some materials. The choice of standard depends on the regulatory framework; for Canadian procurement, CGSB is mandatory.
A: ASTM D5035 is the equivalent test method in the U.S. Both standards share the same principle (CRE machine, 50 mm strip width, 200 mm gauge length) but differ in conditioning—CGSB requires 65% RH, ASTM uses 65% RH as well (standard atmosphere) but may allow 50% RH for some materials. The choice of standard depends on the regulatory framework; for Canadian procurement, CGSB is mandatory.
Article published for informational purposes. Always consult the latest version of the standard for official requirements.
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