Comparison of fracture toughness of paper with tensile properties

The paper web runnability is significantly affected by the presence of defects in the material. Fracture toughness (FT) of paper measures its resistance to fracture from pre-existing flaws and is closely related with the runnability. However, lack of rapid and reliable technique to measure the FT is a major drawback in the improvement of runnability. The aim of this work was to find any relationship between conveniently obtainable tensile properties (tensile strength, elastic modulus and Tensile Energy Absorption (TEA)) and the FT. Twelve samples were measured, from a mixture of machine made papers and handsheets. The range of FT measured by the EWF method was 8.2-28.9 Jm/kg. In this work, tensile index and TEA were both found to be linearly correlated with FT with correlation coefficients of R² = 0.72. However in neither case was the correlation strong enough to justify using the tensile property to predict the fracture toughness.