Effect of agricultural residue fibers on newsprint strength properties

As newsprints, mostly made from recycled wood pulp, are not high quality papers according to its optical, mechanical and chemical characteristics, in this research the usage of straw pulp as an alternative raw material was analyzed. For that purpose, straw pulp was mixed with recycled wood pulp and strength properties of laboratory made papers were determined according to TAPPI standards. Selection of agricultural waste for preparing straw pulp was based on annual yield of crop species (Triticum spp., Hordeum vulgare L. and Triticale sp.). Results indicated that straw pulp can be efficiently used in portions up to 20% as a substitute for wood fibers or as an additive in order to obtain particular newsprint properties.

Short note: Shear strength estimation model for tropical wood species

For safety reasons, wood strength values are calculated based on their characteristic values. Brazilian national standard (NBR, in Portuguese “Norma Brasileira Regulamentadora”) 7190 (1997) establishes ratios for characteristic strength estimation and three forms of wood characterization, with an emphasis on the simplified procedure for common species, which allows obtaining the strength characteristic values through equations correlating different mechanical properties. The present work evaluates the accuracy of the relation proposed by NBR 7190 (1997) of shear strength along the grain (fv0,k) to compression strength along the grain (fc0,k) (fv0,k=0.12 fc0,k). 960 experimental measurements of shear and compression strength values were performed for 40 hardwood species, and the precision of the relation proposed by the Brazilian standard was evaluated using the analysis of variance (ANOVA) method. Linear, exponential, logarithmic, and geometric regression models were used as an alternative to the NBR relation for shear strength estimation. The statistical analysis revealed that the geometric regression is the model of best fit.