Zero-span tensile strength of paper | TAPPI T231 | ISO 15361
The zero-span tensile test provides information on the fiber strength of paper. The test is performed to Tappi T231 in the paper’s dry state. ISO 15361 also describes a method for determining the tensile strength of pulp at zero span in a wet or dry state.
A tensile load is applied to a test strip with a grip-to-grip separation approaching zero. This causes most of the load to be applied to the cellulose fibers and less to the total fabric of the paper. The zero-span tensile strength, together with the tensile strength measured to TAPPI T494, ASTM D828, or ISO 1924 is useful, to optimize fiber processing methods and maximize the use of fiber sources such as recycled fibers to achieve the highest possible quality of the final paper or cardboard product.
Zero-span test device Materials testing machines Downloads Request a consultation
Determining the zero-span tensile strength with ZwickRoell
Determining the zero-span tensile strength is generally carried out using single-purpose devices that are correspondingly complex and expensive.
For occasional tests performed with a tensile testing machine, the ZwickRoell modular system of specimen grips, grip inserts, and accessories are useful:
- The specimen grips must comply with minimum accuracy requirements, therefore pneumatic grips are needed.
- The exact position of the two specimen grip units relative to each other must first be set (once only) with reference to angular position and horizontal position. A mechanical add-on kit is available for this.
- The jaws required protrude upwards from the base of the grips, allowing a free length of less than 0.1 mm. Stepless grip-to-grip separation adjustment starting from 5 µm is possible.
For paper tensile tests that typically require much less than 5 kN, a single-column zwickiLine universal testing machine is a good choice.
