Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5735-95 – Standard Test Method Technical Guide
📐 Specimen Geometry and Conditioning
This article details the procedure for ASTM Designation D 5735 – 95 (Reapproved 2001), which specifies the Standard Test Method for Tearing Strength on Nonwoven Fabrics by the Tongue (Single Rip) Procedure. The test specimen must be cut to precise dimensions to ensure repeatable tear propagation. The specimen is cut to 75 ± 1 mm (3.0 ± 0.1 in) wide by 200 ± 1 mm (8.0 ± 0.1 in) long. A precise longitudinal cut of 75 mm (3.0 in) is made from the center of one narrow edge, running parallel to the length of the fabric to form the two distinct “tongues” for clamping in the tensile tester jaws.
Proper conditioning of the specimens is mandatory for valid results. All test specimens must be conditioned in the standard atmosphere for textile testing as specified in Practice D 1776: 21 ± 1 °C (70 ± 2 °F) and 65 ± 2 % relative humidity for a minimum of 4 hours immediately prior to testing.
💡 Directional Marking is Critical: Because an easily distinguishable pattern for orientation (machine direction vs. cross direction) may not be apparent in nonwovens, especially when removed from the roll, the standard strongly recommends taking care to maintain the directionality by clearly marking the specimen direction upon sampling.
⚙️ Test Procedure and Speed Selection
The preferred testing apparatus for this method is a Constant-Rate-of-Extension (CRE) tensile testing machine conforming to Specification D 76. The machine must be equipped with a recorder capable of producing a complete force-extension curve. It is recognized that Constant-Rate-of-Traverse (CRT) machines continue to be used in some laboratories; these instruments may be used strictly when formally agreed upon between the purchaser and the supplier, with specific operational conditions defined in Appendix X1 of the standard.
| 🟦 Setup Parameter | 📏 SI Units | 📐 Inch-Pound Units |
|---|---|---|
| Gauge Length | 75 mm | 3.0 in |
| Rate of Extension | 300 mm/min | 12 in/min |
| Full Scale Load (typical range) | 100 – 1000 N | 20 – 200 lbf |
| Frequency of Test | Minimum 5 specimens per direction (machine/cross) | |
One tongue of the specimen is clamped in the upper jaw and the other in the lower jaw. As the machine operates at the specified rate of extension, the tear propagates along the length of the specimen. The recording of the force required to continue the tear is stopped once the tear reaches the end of the uncut portion of the fabric.
⚠️ Handling Untearable Fabrics: The standard explicitly notes that if the fabric tear does not run substantially lengthwise in the direction of the applied force, the fabric shall be described as untearable in that direction by this test. This method is also explicitly noted as potentially not useful for highloft nonwoven fabrics.
📊 Key Measured Properties
The primary measurable property is the Tongue Tear Strength, which is explicitly defined in the standard as the maximum single-peak force required to continue or propagate a tear previously started in the specimen. This value represents the combined force required to shift fibers, break fibers, break fiber bonds, and break fiber interlocks within the nonwoven structure. It is important to note that the reported value is not directly related to the force required to initiate the tear.
During data analysis, the maximum peak value on the force-extension curve is identified. For nonwoven fabrics, the tearing force may appear as either a single peak or a series of peaks. If a small decrease in force occurs at a time when the applied force is generally increasing, it is typically not counted as a distinct peak for the calculation. The average of the maximum peaks from the set of specimens is calculated and reported for each test direction (machine and cross).
❓ Frequently Asked Questions
🔍 What is the difference between the tongue tear (D5735) and the trapezoidal tear (D4533)?
The tongue (single rip) procedure involves gripping the two separate tongues of a specifically slit specimen to propagate the tear in a precise center axis. The trapezoidal tear method clamps a trapezoidal-shaped specimen along its non-parallel edges. The stress distribution and deformation of the fabric during tearing differ significantly between the two geometries. D5735 specifically standardizes the tongue procedure for nonwoven fabrics.
💡 Can this test be performed on coated or resin-treated nonwovens?
Yes, the standard states this test method applies to most nonwoven fabrics, including those that are heavily sized, coated, or resin treated. The primary caution is that fabric must tear in the direction of the applied force; if the materials are too strong and the tear deviates, the fabric is considered untestable in that direction by this method. Highloft fabrics are an noted exception where the method may not be useful.
⚡ How is the specific tearing force value determined from a complex force-extension curve?
The tearing force is taken as the maximum single-peak force recorded during the entire tearing of the specimen, regardless of whether the curve contains one peak or multiple peaks. This is a crucial distinction from tests that use an “average force” calculation, recognizing the unique failure response of nonwoven structures where a single critical peak often dictates the ultimate tear resistance.
📌 What specific safety considerations are cautioned in this test method?
Section 1.5 of the standard states that it does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. This typically includes guarding against pinch points in the tensile tester jaws and proper handling of fabric dust or sharp edges.