Leather Tearing Power: Stunning Durability Unveiled

The number of loads borne on the crack per unit thickness of the leather crack when the leather is stretched. Tear strength is an important mechanical property of leather. It measures the strength of leather samples with existing cracks when they are torn again under external force, i.e., the strength of cracks and re-tearing. This helps determine the tear resistance of leather under external force, so that shoes and clothing made from leather are not damaged during sewing or bonding during wear. Tear strength is a key indicator of leather used in clothing, basically reflecting the durability of the leather.

Why measure tear force?

The tearing force is light leather It measures the force required to tear a leather sample with an existing crack under external force. That is, it measures the force required for the crack to re-crack, and to assess the leather’s tear resistance under external force, so that leather shoes, leather clothing, and other items are protected from damage during sewing or bonding during wear.

In other words, this test simulates sewing and glue tearing encountered during wearing.

Why does it tear?

In 1950, Glassman mentioned in his study “On the Physical Properties of Leather, Leather Structure, and Tanning Relationships” that when measuring tensile strength and tear force, the adaptation and changes of fiber tissue can be correspondingly divided into three stages: (1) mesh deformation of the tissue; (2) The elastic deformation of individual fibers and the force generated by the relatively high rigidity value here; (3) Elastic or destructive deformation at the joint or individual fiber due to tearing.  

This refers to the fiber bundles of leather deformed when they are subjected to tensile force. From a mechanical property perspective, leather deformation occurs in two ways: elastic deformation and permanent deformation.

Leather is an elastic material. When subjected to external tension, the fiber bundles deform and generate internal forces. This internal force helps the fiber bundles return to their original positions and shapes. Therefore, when the external force is removed, the extended parts of the fiber bundles largely return to their original state, which is called elastic deformation. When subjected to external force and tension, due to differences in the direction of the fiber bundle and the applied force, the original position changes and the elastic limit is exceeded. After removing the external force, the original position cannot be restored. This part of the body is irreversible deformation called permanent deformation.

For leather, no matter how strong the external force, elastic deformation and permanent deformation can occur simultaneously.

Measurement Methods?

Currently, the bilateral tearing method is commonly used.

Reference standard: “QB/T2711-2005 Determination of Tear Force in Physical and Mechanical Leather Tests”

    Tear strength test results for leather of different thicknesses

Experimental materials	Thickness mm	Tear force N
cow leather	1.2	16.3
Pork skin	1.2	15.5
Sheepskin	1.2	13.6

Testing uses both longitudinal and transverse types; generally, the transverse tear force is greater than the longitudinal tear force.

How to improve tearing force?

(1) Maintain the good strength properties of natural fibers. In other words, it avoids collagen hydrolysis and enzyme damage. In other words, avoid excessive tanning agent deposits that weaken the fibers.

(2) Ensure good fiber mobility, so that fibers may form a mesh-like deformation in the direction of force. That is, small grease additives or loose tanning agents are added to keep the fibers soft.

(3) Achieve good sliding properties of microfibers and fibrous materials. In other words, various large-particle lubricants are added or sufficiently wet.

(4) Microfibers adhere to form elastic microfiber bundles. That is, use as little tanning agent as possible or tanning agents that do not separate microfibers.