Tensile strength of paper

What is the tensile strength of paper?

Tensile strength is the maximum stress at which a strip of paper breaks. It is one of the important basic physical properties of paper and board. Tensile strength is based on differences in fiber orientation. Since the fiber orientation differs between machine direction (MD) and cross direction (CD), tensile strength was measured in both directions. The machine direction is the direction of the web running on the machine, while the CD is the direction perpendicular to the sheet running on the machine in the papermaking process. Vertically larger than horizontally. Calculated in force per unit width and expressed as N/m.

Tensile strength testing for paper is similar to other material testing, but expressed differently. Tensile strength is usually expressed in terms of load per unit cross-section in most cases, and in the paper industry it is expressed in terms of load per unit of specimen. If the tensile strength of the paper is low, the quality of the paper is lowered and it is necessary to improve the quality of the paper by improving different factors.

Tensile Strength of Paper

Tensile strength is used to determine a paper's resistance to web breakage. The strength, length and bonding of the fibers, the degree of refinement of the fibers, and the orientation of the fibers are the main sources of the tensile strength of the paper. This also depends on the quality and quantity of fillers used. This is an important factor for many applications such as printing paper, converting paper and packaging paper.

Tensile index and its calculation

Tensile index is defined as tensile strength divided by basis weight and is expressed in Nm/g.

Tensile Strength = N/m 

Basis Weight = g/m2 
Therefore, Tensile Index (TI) = (N/m)/(g/m2) = Nm/g

Tensile strength testing machine

There are several types of Tensile Strength Testers that can be used with specimens oriented horizontally or vertically. There are five types of Tensile Strength Tester equipment used in the paper industry, such as rigid crosshead type, inclined plane type, hydraulic type, and spring type. Among them, the pendulum tensile strength test is commonly used.