Rust stains, extending into the cross section of natural fiber and nylon fiber yarns, can lower the line strengths by as much as what percent?

• A. 10%
• B. 40%
• C. 60%
• D. 20%

Answer: (B)

When rust stains extend into the cross section of natural fiber and nylon yarns, they create internal flaws that act as weak points where load concentrates. The iron compounds from rust penetrate between fibers and along the polymer structure, promoting micro-cracking and increased moisture interaction inside the fiber. This internal damage reduces the effective area that can carry tension, so the line strength drops significantly. In practical terms, the strength reduction can be as much as forty percent when rust contamination reaches the cross section. Smaller reductions assume only surface damage and don’t reflect the loss from internal weakening, while much larger reductions are not typically observed for this type of staining.