Effect of fibre properties on the ring crush strength and creep of high yield pine kraft pulp handsheets

摘要

This paper examines the relationship between the properties of Pinus radiata high yield kraft pulp fibres and the ring crush strength, and creep behaviour under cyclic humidity conditions, of paper produced from these fibres. Broad natural distributions in properties make it difficult to establish relationships between fibre and paper properties. Ideally one fibre property is varied whilst other properties are kept constant. We attempted to achieve this for fibre length by screening and cutting, for cross section dimensions by screening and fractionation in a hydrocyclone, and for microfibril angle by separation of rings in the logs prior to chipping and pulping. Ring selection and screening were used to keep some fibre properties approximately constant. Ring crush strength was almost constant and creep rate increased as fibre length increased. Sheet density also decreased and this may have affected properties rather than just the direct effect of fibre length. Ring crush strength decreased and creep rate increased with increasing fibre wall thickness whilst strength increased and creep rate decreased with increasing fibre diameter. Decreasing wall thickness and increasing diameter both lead to increased fibre collapse and thus fibre/fibre bonding. The effect of microfibril angle could not be determined as, despite screening, fibre length decreased as microfibril angle increased.