Kraft pulp refining and reinforcement potential in fibre-cement composites

摘要

The refining response of a high coarseness radiata pine unbleached krafl pulp has been studied at low consistency using a laboratory disc refiner. The refining intensity ranged from 0.3 - 2.8 Ws/m. Results showed that, at a given freeness, the average fibre length decreased with increasing refining intensity. At intensities less than 1 Ws/m fibre length reduction was minimal but refining to target freeness required significantly more energy than at higher intensities. The fibre length distributions were flattened and skewed to a shorter mean length with increasing refining intensity. Fibre coarseness and fibre strength were unaffected by refining. The mechanical strength of fibre-cement composites was also measured in an attempt to correlate flexural strength and toughness with fibre properties and refining strategies. Long-fibred pulps, from low intensity refining, formed fibre-matrix composites of lower density and flexural strength. At higher refining intensities, panel densities and flexural strength increased, despite a reduced fibre length. Composite fracture toughness was positively correlated with fibre length. The influence of fibre length, panel density and the fibre-matrix interfacial region on the role of fibre pullout and fibre fracture in composite failure, is discussed.