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D5170-98 – Standard Test Method Technical Guide
🧪 Scope and Significance of the Peel Strength Test
Standard D5170-98 (Reapproved 2021) defines the “T” method for measuring the peel strength of hook and loop touch fasteners using a recording constant-rate-of-extension (CRE) tensile testing machine. This test quantifies the resistance to separation when forces are applied normal to the line of separation. Per Section 1.2, all values stated in inch-pound units are regarded as the standard for this test method.
Because the force registered in a peel test is inherently irregular, the standard provides two distinct empirical calculation methods in Section 3.3. The Integrator Average generally yields a lower value and is well suited for quality control. The Average of the Five Highest Peaks better reflects the force required to separate a closure, making it more representative of real-world performance. These methods are explicitly stated as not equivalent.
| 🟦 Feature | 📏 Integrator Average | 🎯 Five Highest Peaks |
|---|---|---|
| Calculation Method | Electronic integration of the force curve over the distance of peel | Arithmetic average of the five highest distinct force peaks |
| Typical Relative Value | Lower | Higher |
| Best Application | General characterization and quality control | Performance benchmarking and dispute resolution |
⚙️ Apparatus and Specimen Preparation
The required apparatus includes a recording CRE tensile testing machine. According to Section 4.1, specimens are prepared using a smooth steel roller approximately 4 ¾ in. (121 mm) in diameter. Standard conditioning of the hook and loop materials is mandatory prior to testing, following the protocol outlined in ASTM D618 (Practice for Conditioning Plastics for Testing) as referenced in Section 2.1.
💡 Unit Standardization: The standard mandates that inch-pound units are the standard. SI unit values provided in parentheses are mathematical conversions for reference only (Section 1.2). Always ensure CRE machine calibration and data recording comply with the required unit system.
📊 Inter-Laboratory Dispute Resolution Protocol
For acceptance testing of commercial shipments, Section 3.5 provides a clear protocol for resolving disputed results. The purchaser and supplier must conduct a comparative test using specimens that are as homogenous as possible, randomly assigning equal numbers to each laboratory. The average results are analyzed using Student’s t-test at an agreed probability level. Competent statistical assistance is strongly recommended for this investigation.
⚠️ Bias Management: If Student’s t-test reveals a statistically significant bias, the cause must be found and corrected. If the bias cannot be resolved, both parties must agree to interpret all future test results in the light of the known bias (Section 3.5). Users are also responsible for establishing proper safety, health, and environmental practices (Section 1.3).
❓ Frequently Asked Questions
🔍 What is the key property measured by ASTM D5170-98?
The test method measures the peel strength of hook and loop touch fasteners, specifically the resistance to separation when forces are applied normal to the line of separation of the fastener (Section 3.1).
💡 Why does the standard provide two different calculation methods?
Due to the irregular force curve generated during a peel test. The integrator average is relatively easy to calculate with modern equipment and is useful for quality control, while the average