ASTM standards to determine the tensile strength of nylon fibers

The appropriate ASTM standard for evaluating the tensile strength of nylon depends on whether you are testing an individual single filament, a continuous filament yarn/thread, or a heavy monofilament/solid plastic.

1. Primary ASTM standards by form factor

ASTM D3822 / D3822M: Single Fiber/Filament

• Best for: Testing individual staple fibers or single filaments extracted from yarn or tow.
• What it measures: Breaking force, elongation at break, breaking tenacity (cN/tex or g/denier), initial modulus, and breaking toughness.
• Key considerations: Requires low-capacity load cells (often <5 N) and specialized mounting frames or pneumatic grips to avoid crushing delicate nylon filaments.

ASTM D2256 / D2256M: Yarns & Threads (Single-Strand Method)

• Best for: Nylon monofilament, multifilament, and spun yarns or industrial sewing threads.
• What it measures: Maximum breaking force, elongation, breaking tenacity, and chord/tangent modulus.
• Key considerations: Utilizes Constant Rate of Extension (CRE) testing machines, typically operating at a 20-second time-to-break. Capstan or pneumatic cord-and-yarn grips are recommended to prevent specimen slippage or jaw breaks.

ASTM D3217/D3217M: Loop & Knot Tenacity

• Best for: Evaluating manufactured fibers (like nylon) subjected to bending, tying, or interlocking.
• What it measures: Breaking tenacity in a double loop or single overhand knot configuration.
• Key considerations: Essential for fishing lines, industrial netting, and surgical sutures where knot failure is a primary performance constraint.

ASTM D638: Heavy Nylon Monofilaments & Molded Plastics

• Best for: Thick nylon monofilament lines, solid extrusions, or dumbbell-shaped plastic test specimens.
• What it measures: Tensile strength (MPa or psi), yield strength, elongation, and Young's modulus.

Key calculations

When running these tests on nylon, results are generally expressed as:

• Breaking tenacity: Tenacity=Linear Density (tex or denier)Breaking Force (cN or gf)​
• Tensile strength: Calculated when cross-sectional area is precisely known (MPa or N/sq m).
• Elongation at Break (%): Percentage increase in length at the point of rupture.