The influence of Grammage on Tensile Properties of Paper

We present theory for the influence of grammage on the tensile strength of paper and compare this with experimental data. The theory assumes the strength of the sheet to be influenced by the fraction of the fibres in the surfaces of the sheet and the likelihood of weak spots occurring. Agreement between theory and experiment is favourable. Our experimental results suggest that there is a density-dependent maximum in plots of tensile index and specific elastic modulus against grammage and that weak spots in the sheet are associated with bonds. We observe also that the influence of formation on tensile strength is greatest at low grammages and that the mean specific elastic modulus is insensitive to formation but the distribution of moduli narrows with increasing grammage.