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D3936-21 – Standard Test Method Technical Guide
ASTM D3936‑21 defines a standardized procedure for measuring the resistance to delamination of the secondary backing applied to pile yarn floor coverings. This test is essential for evaluating the construction integrity and long‑term durability of tufted carpets during manufacturing and acceptance testing.
📏 Scope and Significance
This test method covers the measurement of the resistance to delamination of secondary backings, including those made from natural and manufactured fibers, as well as attached cushion backings. According to the scope, the values stated in inch‑pound units are regarded as the standard for reporting results; SI unit equivalents provided in parentheses and are for information only. The method is primarily used for acceptance testing of commercial shipments.
Section 5 establishes a comprehensive protocol for resolving disputes between laboratories. When a significant statistical bias is identified, the cause must be investigated and corrected, or both parties must agree to interpret future test results considering the known bias. A group of homogeneous test samples should be randomly assigned for comparative testing before any dispute analysis begins.
⚠️ Dispute Resolution Protocol: If a bias is found between two laboratories, competent statistical assistance is recommended. Either the cause must be found and corrected, or the purchaser and supplier must agree to interpret future test results with consideration of the known bias. Comparative tests as directed in Section 5.2 are critical for this process.
⚙️ Test Procedure and Specimen Preparation
Specimens are first conditioned in the standard atmosphere for testing textiles in accordance with Practice D1776. A conditioned specimen is prepared by manually separating the secondary backing from the primary construction for a distance of approximately 1.5 in. (38 mm). The separated ends are then placed into the opposing clamps of a constant‑rate‑of‑extension (CRE) tensile testing machine conforming to Specification D76.
The machine is started and operated at a specified crosshead speed. The force required to continue the delamination over a defined recording distance is continuously recorded. The peak forces observed within the specified length intervals are averaged to calculate the final resistance to delamination.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Specimen Width | 3.0 ± 0.03 in. (75 ± 1 mm) |
| Initial Manual Separation Distance | 1.5 in. (38 mm) |
| Gage Length (Clamp Separation at Start) | 2.0 ± 0.03 in. (50 ± 1 mm) |
| Crosshead Speed (CRE Tester) | 12.0 ± 0.5 in./min (300 ± 13 mm/min) |
| Length of Delamination Recorded | 5.0 in. (125 mm) |
📊 Key Measured Properties and Terminology
The primary result of the test is the average resistance to delamination, calculated by averaging the peak forces recorded over the specified test intervals. This value is reported in units of force per unit width of the specimen. Terminology used in the standard is derived from Terminology D5684 (Pile Floor Coverings) and Terminology D123 (Textiles).
| 🎯 Property | 📐 Definition / Unit |
|---|---|
| Peak Force | The maximum force recorded within a specified interval during the delamination process. |
| Resistance to Delamination | The average of the peak forces per unit width of the specimen, reported in lbf/in. or N/m. |
| Constant‑Rate‑of‑Extension (CRE) | The standard type of tensile testing machine required for this test, defined in Specification D76. |
| Secondary Backing | An additional layer applied to the underside of the pile floor covering to provide dimensional stability and durability. |
💡 Testing Best Practice: The manual separation of the specimen at the beginning of the test must be performed carefully and consistently. The specified distance of approximately 1.5 in. (38 mm) allows sufficient material for secure clamping without pre‑stressing or damaging the bond line before the tensile test begins. Always condition the test specimens per Practice D1776 to ensure reproducible results.
❓ Frequently Asked Questions
🔍 What is the specific purpose of the D3936‑21 test?
The standard specifically measures the resistance to delamination of the secondary backing applied to pile yarn floor coverings. This helps evaluate the construction integrity, lamination quality, and long‑term serviceability of the carpet under mechanical stress.
💡 Which type of testing machine is required by this standard?
The standard requires a tensile testing machine that conforms to Specification D76, which establishes the requirements for a Constant‑Rate‑of‑Extension (CRE) testing machine. The machine must be capable of operating at a crosshead speed of 12.0 in./min.
⚡ Are inch‑pound or SI units considered standard in D3936‑21?
Inch‑pound units are regarded as the standard for reporting values under this test method. SI unit equivalents provided in the standard text are for information only and are not considered standard units.
📌 How is the test specimen prepared for the delamination procedure?
The secondary backing layer is manually separated from the primary backing for a distance of approximately 1.5 in. (38 mm). This gives the technician enough material to insert the separated layers securely into the upper and lower clamps of the tensile tester without damaging the remaining bond.