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CAN CGSB 4.2 No. 19.1-2004 (2013): Standard Test Method for Bursting Strength of Fabrics – Diaphragm Method
A comprehensive overview of the Canadian standard for evaluating fabric bursting resistance using the diaphragm method
Introduction
CAN CGSB 4.2 No. 19.1-2004 (2013) is a Canadian national standard of the Canadian General Standards Board that describes a test method for determining the bursting strength of textile fabrics by the diaphragm method. The standard was originally published in 2004 and was reaffirmed without technical changes in 2013. It forms part of the CGSB 4.2 series of textile test methods and is widely used in quality control, product development, and regulatory compliance for fabrics such as knits, nonwovens, and other materials that are subjected to multidirectional stress.
This article provides a thorough technical analysis of the standard, covering its scope, key technical requirements, implementation considerations, and compliance aspects.
Scope
The standard specifies a procedure for measuring the bursting strength of textile fabrics using a hydraulic or pneumatic diaphragm bursting tester. The method is applicable to woven, knitted, and nonwoven fabrics, as well as fabrics produced by other methods, provided they can be clamped without slippage and can resist the applied pressure. The test is primarily intended for materials that exhibit a bursting failure mode, such as knits and stretch fabrics, where tensile testing in one direction does not fully characterize the material’s strength.
CAN CGSB 4.2 No. 19.1-2004 (2013) covers both constant-rate-of-increase-of-pressure (CRIP) and constant-time-to-burst (CTB) testing modes. The standard includes requirements for apparatus, test specimen preparation, conditioning, number of specimens, test procedure, calculation of results, and reporting.
The test is performed on a fabric specimen clamped over an expandable diaphragm. The diaphragm is expanded by hydraulic or pneumatic pressure until the specimen bursts. The bursting pressure is recorded and expressed in kilopascals (kPa) or pounds per square inch (psi).
Important: This standard does not purport to address all safety concerns associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.
Technical Requirements
Apparatus
The key apparatus components required by the standard include:
- Diaphragm: A flexible, non‑extensible diaphragm (typically made of synthetic rubber or similar material) that is clamped around its periphery and expands under pressure. The diaphragm must be replaced if it shows signs of deterioration or after a maximum of 500 tests.
- Clamping System: Two concentric annular clamps that firmly hold the test specimen without slippage. The recommended inside diameter of the clamping ring is 30.5 mm ± 0.5 mm, though other diameters are permitted if specified.
- Pressure Sensor: A calibrated pressure gauge or transducer with an accuracy of ±1% of the full scale reading over the operating range.
- Hydraulic/Pneumatic System: A pump or pressure source capable of increasing the pressure at a controlled rate. For the CRIP mode, the rate of increase is 100 kPa/s ± 10 kPa/s (or equivalent).
- Recording Device: A chart recorder, digital display, or data acquisition system to capture the burst pressure.
Test Specimens
Specimens are cut to a size sufficient to allow clamping without interference. A minimum of five representative specimens per sample are required unless otherwise specified. They are conditioned at 20°C ± 2°C and 65% ± 4% relative humidity for at least 24 hours before testing, or until equilibrium is reached. In cases of dispute, conditioning must be performed under these standard atmospheric conditions.
Procedure
The standard provides two procedures: Constant Rate of Increase of Pressure (CRIP) and Constant Time to Burst (CTB). The CRIP procedure is the primary method.
- Place the conditioned specimen over the diaphragm and secure it with the clamping ring to prevent slippage.
- Start the pressure increase at the specified rate (100 kPa/s). Record the pressure at the moment of rupture (burst pressure).
- If the specimen bulges significantly before burst, the test is considered valid. Any slip or failure at the clamp edge is noted and may require discarding that result.
- Repeat for the required number of specimens (typically five to ten).
- Report the average bursting pressure, standard deviation, coefficient of variation, and any observed anomalies (e.g., type of rupture).
Tip: When testing fabrics with high stretch (e.g., elastic knits), ensure that the clamping pressure is sufficient to prevent the specimen from being pulled into the test area. A thin rubber gasket between the clamp and fabric may help hold the specimen without damage.
Calculation and Reporting
Individual burst pressures are recorded and used to calculate the arithmetic mean, standard deviation, and coefficient of variation. Results are reported to the nearest 1 kPa (or 0.1 psi). The report must also include: sample identification, number of tests, conditioning details, any deviations from the standard, and the type of failure (e.g., edge burst, center burst, diaphragm rupture).
Table of Key Test Parameters
| Parameter | Requirement |
|---|---|
| Clamping ring inside diameter | 30.5 mm ± 0.5 mm (other diameters may be used with notation) |
| Rate of pressure increase (CRIP mode) | 100 kPa/s ± 10 kPa/s |
| Number of specimens | At least 5 (preferably 10) |
| Conditioning atmosphere | 20°C ± 2°C; 65% ± 4% RH |
| Conditioning time | ≥ 24 h (or until equilibrium) |
| Diaphragm replacement interval | After each 500 tests or when deterioration is observed |
| Pressure sensor accuracy | ±1% of full scale |
Implementation Highlights
Effective implementation of CAN CGSB 4.2 No. 19.1-2004 (2013) requires attention to several practical aspects:
- Calibration: The pressure sensor and rate‑control system must be calibrated periodically using traceable references. Regular verification ensures that burst pressures are accurate and repeatable.
- Diaphragm Condition: The diaphragm is critical for reproducing correct bulging behavior. Regular inspection for cracks, permanent deformation, or loss of elasticity is essential. Always replace the diaphragm if it has been in service for more than 500 tests or if irregularities are noted.
- Specimen Handling: Fabrics with a pronounced grain or direction (warp/weft, course/wale) should be tested with the same orientation for consistency. For isotropic materials, orientation is less critical.
- Wet Testing: While the standard primarily addresses dry fabrics, provisions for wet testing are included in some derivative procedures. If evaluating materials for end‑use in wet conditions (e.g., tarpaulins, geotextiles), ensure conditioning reflects the actual service environment.
- Data Management: Use software or automated testers that can capture the burst curve. Modern burst testers can calculate peak pressure, rupture time, and even provide stress‑strain data up to burst.
Success Factor: Laboratories that consistently achieve high repeatability often follow a strict regime for diaphragm replacement and routine cross‑verification of pressure readings against a reference gauge. This practice minimizes measurement uncertainty and enhances the credibility of test results.
Compliance Notes
Compliance with CAN CGSB 4.2 No. 19.1-2004 (2013) is essential for manufacturers and testing laboratories operating in Canada or supplying textile products to the Canadian market. Key compliance aspects include:
- Accreditation: Testing laboratories should be accredited to ISO/IEC 17025 for this specific test method by a recognized body such as the Standards Council of Canada (SCC). Accreditation ensures adherence to the technical and quality management requirements of the standard.
- Use in Combination with Other Standards: The method is often referenced together with product specifications that impose minimum burst strength requirements (e.g., for workwear, medical textiles, or upholstery). It may also be used as an alternative to the ball burst method (ASTM D3787) for certain fabric types.
- Test Report: A full statement of compliance must include the standard designation (CAN CGSB 4.2 No. 19.1-2004 (2013)), details of any deviations, and the raw data from which the average and variation are derived. A report lacking this information may be considered non‑compliant.
- Market Surveillance: Canadian regulatory bodies and retailers often require third‑party test reports to confirm that imported fabrics meet the minimum burst strength specified in relevant product safety or performance standards.
Safety Warning: The hydraulic pressure system can operate at high pressures (up to 10,000 kPa or more). Always ensure that safety guards are in place and that the diaphragm is properly installed to avoid fluid ejection. Use only recommended hydraulic fluids and dispose of them according to local environmental regulations.
Frequently Asked Questions
Q: What is the main difference between CAN CGSB 4.2 No. 19.1‑2004 (2013) and ASTM D3786 / D3786M?
A: Both standards use the diaphragm method and share many procedural similarities. The principal difference lies in the conditioning atmosphere and some dimensional tolerances. CAN CGSB 4.2 No. 19.1‑2004 (2013) requires 20°C ± 2°C and 65% ± 4% RH, while ASTM D3786 often specifies 21°C ± 1°C and 65% ± 2% RH. Additionally, the clamping ring diameter may vary slightly between the two standards. Users should select the standard that aligns with their target market or client specification.
A: Both standards use the diaphragm method and share many procedural similarities. The principal difference lies in the conditioning atmosphere and some dimensional tolerances. CAN CGSB 4.2 No. 19.1‑2004 (2013) requires 20°C ± 2°C and 65% ± 4% RH, while ASTM D3786 often specifies 21°C ± 1°C and 65% ± 2% RH. Additionally, the clamping ring diameter may vary slightly between the two standards. Users should select the standard that aligns with their target market or client specification.
Q: Which fabric types are best suited for the diaphragm method?
A: This method is ideal for fabrics that exhibit biaxial stress under use, such as knitted fabrics, nonwovens, stretch woven fabrics, and technical textiles. It is less suitable for very stiff or rigid materials that cannot bulge significantly without tearing at the clamp edge. For such materials, the ball burst method (CGSB 4.2 No. 19.2) or a tensile test may be more appropriate.
A: This method is ideal for fabrics that exhibit biaxial stress under use, such as knitted fabrics, nonwovens, stretch woven fabrics, and technical textiles. It is less suitable for very stiff or rigid materials that cannot bulge significantly without tearing at the clamp edge. For such materials, the ball burst method (CGSB 4.2 No. 19.2) or a tensile test may be more appropriate.
Q: How often should the diaphragm be replaced?
A: The standard recommends replacing the diaphragm after a maximum of 500 tests or whenever visible signs of wear, cracking, or permanent deformation are observed. In high‑throughput laboratories, a regular replacement schedule based on test count is essential to maintain test precision.
A: The standard recommends replacing the diaphragm after a maximum of 500 tests or whenever visible signs of wear, cracking, or permanent deformation are observed. In high‑throughput laboratories, a regular replacement schedule based on test count is essential to maintain test precision.
Q: Can the test be performed on wet or conditioned fabrics?
A: Yes. While the standard primarily describes testing under standard atmospheric conditions, it can be adapted for wet fabrics if the conditioning is performed by immersing the specimens in water at room temperature for a specified period (commonly 24 hours). In such cases, the testing conditions must be clearly reported, as wet bursting strength will differ from dry values.
A: Yes. While the standard primarily describes testing under standard atmospheric conditions, it can be adapted for wet fabrics if the conditioning is performed by immersing the specimens in water at room temperature for a specified period (commonly 24 hours). In such cases, the testing conditions must be clearly reported, as wet bursting strength will differ from dry values.
Last updated: January 2026. This article is intended as a technical overview and does not replace the official text of CAN CGSB 4.2 No. 19.1-2004 (2013). Always refer to the latest version of the standard for complete requirements.