PAPERmaking! FROM THE PUBLISHERS OF PAPER TECHNOLOGY Volume 5, Number 1, 2019
Carboxymethylated cellulose nanofibrils in papermaking: influence on filler retention and paper properties, AF Lourenço et al, Cellulose , Vol.26 (5). The present paper deals with the production of cellulose nanofibrils (CNF) from bleached Eucalyptus kraft pulp by carboxymethylation and TEMPO-mediated oxidation, followed by high pressure homogenisation. The main purpose of the work was to increase the filler retention and mechanical strength of printing and writing paper grades. Mineral fillers are of utmost importance in papermaking and therefore a thorough study of the CNF influence in filler-containing handsheets is mandatory. In this sense, flocculation studies revealed the extraordinary ability of CNF to flocculate calcium carbonate, which was translated into high filler retentions in the paper matrix. Moreover, the interactions between bleached pulp, CNF, mineral fillers and common paper additives, such as cationic starch, alkenyl succinic anhydride and cationic polyacrylamide, were investigated. The results show that, depending on the materials applied, CNF are able to promote an adequate bonding between fibres and filler aggregates, reducing the requirements for the additives. The addition of carboxymethylated or TEMPO-oxidised CNF to the fibrous matrix led to handsheets with better structural, mechanical and optical properties than those of reference handsheets (without CNF and with additives). Mechanisms of strength and stiffness improvement of paper after PFI refining with a focus on the effect of fines, Hamid Reza Motamedian et al, Cellulose , Vol.26 (6). Refining (i.e., mechanical beating of pulp) is a common procedure that is used in paper- making to improve the mechanical properties of the final product. The improvements caused by refining are mainly attributed to increased density and to a better bonding between fibres. In this work, we study how various mechanisms that can be triggered by refining affect the tensile behaviour of the sheets. A paper sizing agent based on leather collagen hydrolysates modified by glycol diglycidyl ether and its compound performance, X Wang et al, International Journal of Biological Macromolecules , Vol.124. In this research, collagen hydrolysates with different average molecular weights from leather collagen were chosen as raw materials. Five environmental-friendly sizing agents (SA) were prepared by cross-linking collagen hydrolysates with glycol diglycidyl ether (GDE) and further grafting them with butyl acrylate (BA) and styrene (St). Then the compound sizing agents (SGDESA- x, x = 1, 2, 3 and 4) were obtained by simple physical mixing of GDESA and starch. The surface sizing performance of GDESA and compound sizing agents were studied. The coated corrugated paper exhibited strong water resistance, good physical and mechanical properties even after refolded for 20 times. PULP / PULPING Determining the repair and maintenance cost of wood chippers, Raffaele Spinelli et al, Biomass and Bioenergy , Vol. 122. Chipping weighs heavily on the total delivered cost of wood fuel, which calls for accurate chipping cost estimates. Chipper repair and maintenance cost is perhaps the most obscure among the figures required for a reliable estimate of chipping cost. To clarify this issue, the authors examined the long-term repair and maintenance records for 51 wood chippers operated by 48 chipping service contractors. The study also provides reference figures for the contribution of labour cost to total maintenance cost. Farm tractors incur more repairs than preventive maintenance, contrary to the other dedicated components of the chipping operation, where preventive maintenance represents most of maintenance cost. Forestry users should make allowance for the lower structural strength of tractors and select large models.
Technical Abstracts
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