Some aspects on strength properties in paper composed of different pulps

Sammanfattning: For papermakers, an understanding of the development of strength properties in the paper is of uttermost importance. Strong papers are desirable both in the traditional paper industry as well as in new fields of application, such as fibre-based packaging and light-weight building material. In this study, the effects of adding abaca (Musa textilis) as a reinforcement fibre for softwood pulp was investigated. Moreover, the LB Multilayer Handsheet Former for the production of stratified sheets was evaluated and used to study the effects of placing selected fibres in separate layers, rather than by making homogeneous sheets from a mixture of the pulps.Handsheets of a softwood sulphate pulp with the addition of abaca fibres were made in a conventional sheet former. It was seen that the addition of abaca fibres can increase the tearing resistance, fracture toughness, folding endurance and air permeance. Tensile strength, tensile stiffness and tensile energy absorption, however, decreased somewhat.It was shown that the LB Multilayer Handsheet Former is suitable for studying the effects of stratification of paper. The sheet former produces sheets with good formation and the variation of paper properties of the sheets is retained at a fairly constant level when the number of layers in the stratified sheets is increased. The uniformity of the sheets produced in the LB Multilayer Handsheet Former are generally at the same level as of those produced in conventional sheet formers.Homogeneous and stratified sheets were produced in the LB Multilayer Handsheet Former and it was found that by stratifying a sheet, so that pulp with a high tear index and pulp with a high tensile index are placed in separate layers, it was possible to increase the tear index by approximately 25%, while the tensile index was decreased by 10-20%.