NC State
  • Researchpp 1158-1167Hu, J.-J., Lei, T.-Z., Xu, G.-Y., Shen, S.-Q., and Liu, J.-W. (2009). "Experimental study of stress relaxation in the process of cold molding with straw," BioRes. 4(3), 1158-1167.AbstractPDF
    In this article, five kinds of straws were used to do compressing molding experiments on stress relaxation by Electric Versatile Material Machine, with specially designed open mode equipment. According to the data from the transition stage of the compression process, regression equations with different straws were built by selective global fitting or piecewise fitting. In addition, the equations were verified by stress logarithm-time curves. A stress relaxation model of the five straws can be summarized by an expression involving the summation of exponential decay terms. This expression provides reference for reducing the specific energy consumption and increasing the pellet density.
  • Researchpp 1147-1157Zhuang, J., Lin, L., Liu, J., Luo, X., Pang, C., and Ouyang, P. (2009). "Preparation of xylose and kraft pulp from poplar based on formic/acetic acid/ water system hydrolysis," BioRes. 4(3), 1147-1157.AbstractPDF
    A formic/acetic acid/water system was used in the ratios of 30:60:10, 20:60:20, and 30:50:20 separately for efficient hydrolysis and bioconversion of poplar chips, under the solid/liquid ratio of 1:12(g/ml), at 105 oC for 30, 45, 60, 75, and 90 min, respectively. The highest yield of 69.89% was at a formic/acetic acid /water ratio of 30:50:20(v/v/v), with solid/liquid in the ratio of 1:12(g/ml) at 105 oC for 90min. Lower kappa number and similar yield were achieved when hydrolytic residual woodchips were used for kraft pulping with over 2% Na2O and temperature 5 °C lower compared to untreated chips. Pulps from prehydrolysis-treated chips were easy to beat. But the tensile index, tear index, and burst index of the handsheets obtained from pulp with lowest kappa number from prehydrolysis-treated poplar chips were lower than those of the pulp from the untreated chips. Considerable xylose could be obtained from the prehydrolysis stage following kraft pulping under the same conditions for prehydrolysis-treated chips and untreated chips. However, by building on the mature kraft pulping and xylitol processes, large amounts of xylose from the hemicellulose were obtained in prehydrolysis, allowing production of high-valued products via biorefinery pathways. An economical balance of chemical dosage, energy consumption, pulp properties, and xylose value for prehydrolysis with organic acid should be reached with further investigation.
  • Researchpp 1168-1177Ioelovich, M. (2009). "Accessibility and crystallinity of cellulose," BioRes. 4(3), 1168-1177.AbstractPDF
    The accessibility of cellulose samples having various degrees of crystallinity was studied with respect to molecules of water, lower primary alcohols, and lower organic acids. It was found that small water molecules have full access to non-crystalline domains of cellulose (accessibility coefficient α = 1). Molecules of the lowest polar organic liquids (methanol, ethanol, and formic acid) have partial access into the non-crystalline domains ( α <1), and with increasing diameter of the organic molecules their accessibility to cellulose structure decreases. Accessibility of cellulose samples to molecules of various substances is a linear function of the coefficient α and the content of non-crystalline domains. The relationship between crystallinity (X) and accessibility (A) of cellulose to molecules of some liquids has been established as A = α (1-X). The water molecules were found to have greater access to cellulose samples than the molecules of the investigated organic liquids. The obtained results permit use of accessibility data to estimate the crystallinity of cellulose, to examine the structural state of non-crystalline domains, and to predict the reactivity of cellulose samples toward some reagents.
  • Researchpp 1178-1189Shen, J., Song, Z., Qian, X., and Liu, W. (2009). "A preliminary investigation into the use of acid-tolerant precipitated calcium carbonate fillers in papermaking of deinked pulp derived from recycled newspaper," BioRes. 4(3), 1178-1189.AbstractPDF
    The use of acid-tolerant precipitated calcium carbonate fillers, including phosphoric acid/sodium hexametaphosphate modified precipitated CaCO3 filler, and sodium silicate/phosphoric acid/sodium hexametaphos-phate modified precipitated CaCO3 filler in papermaking of deinked pulp derived from recycled newspaper was explored. These two acid-tolerant fillers provided considerably more brightness improvement in papers in comparison the unmodified filler, presumably indicating alleviated pulp darkening achieved as a result of better acid-resistant properties. The addition of acid-tolerant fillers into the furnish slurries gave lower system pH as compared with unmodified filler. Among the three fillers used in this work, the effect on retention of modification of the filler with sodium silicate/phosphoric acid/sodium hexametaphosphate was probably the best, as evaluated from ash content measurements. For air permeability of the paper, the use of acid-tolerant fillers provided slightly more improvement in comparison to the unmodified filler. For tensile and burst strength of the paper, the use of sodium silicate/phosphoric acid/sodium hexameta-phosphate modified precipitated calcium carbonate filler gave better results as compared with the other two fillers. Additionally, the improving effect of acid-tolerant fillers on furnish static drainage was found to be slightly weaker than that of unmodified filler.
  • Reviewpp 1190-1209Shen, J., Song, Z., Qian, X., and Liu, W. (2009). "Modification of papermaking grade fillers: A brief review," BioRes. 4(3), 1190-1209.AbstractPDF
    The use of fillers in paper products can provide cost and energy savings, improved paper properties, increased productivities, and specifically desired paper functionalities. There are many problems associated with the use of fillers, such as unsuitability of calcium carbonate fillers in acid papermaking, negative effects of filler loading on paper strength, sizing, and retention, and tendencies of fillers to cause abrasion and dusting. In order to solve these problems and to make better use of fillers, many methods have been proposed, among which filler modification has been a hot topic. The available technologies of filler modification mainly include modification with inorganic substances, modification with natural polymers or their derivatives, modification with water-soluble synthetic polymers, modification with surfactants, modification with polymer latexes, hydrophobic modification, cationic modification, surface nano-structuring, physical modification by compressing, calcination or grinding, and modification for use in functional papers. The methods of filler modification can provide improved acid tolerant and optical properties of fillers, enhanced fiber-filler bonding, improved filler retention and filler sizabilities, alleviated filler abrasiveness, improved filler dispersability, and functionalization of filled papers. Filler modification has been an indispensable way to accelerate the development of high filler technology in papermaking, which is likely to create additional benefits to papermaking industry in the future.
  • Reviewpp 1210-1221Muszyński, L. (2009). "Imaging wood plastic composites (WPCs): X-ray computed tomography, a few other promising techniques, and why we should pay attention," BioRes. 4(3), 1210-1221.AbstractPDF
    Wood plastic composites are complex, anisotropic, and heterogeneous materials. A key to increasing the share of the WPC materials in the market is developing stronger, highly engineered WPCs characterized by greater structural performance and increased durability. These are achieved by enhanced manufacturing processes, more efficient profile designs, and new formulations providing better interaction between the wood particles and the plastic matrix. Significant progress in this area is hard to imagine without better understanding of the composite performance and internal bond durability on the micro-mechanical level, and reliable modeling based on that understanding. The objective of this paper is to present a brief review of promising material characterization techniques based on advanced imaging technologies and inverse problem methodology, which seem particularly suitable for complex heterogeneous composites. Full-field imaging techniques and specifically X-ray computed tomography (CT) combined with numerical modeling tools have a potential to advance the fundamental knowledge on the effect of manufacturing parameters on the micromechanics of such materials and their response to loads and environmental exposure.
  • Reviewpp 1222-1262Wu, N., Hubbe, M. A., Rojas, O. J., and Park, S. (2009). "Permeation of polyelectrolytes and other solutes into the pore spaces of water-swollen cellulose: A review," BioRes. 4(3), 1222-1262.AbstractPDF
    The rate and extent of transport of macromolecules and other solutes into cellulosic materials and fibers have important applications in such fields as papermaking, textiles, medicine, and chromatography. This review considers how diffusion and flow affect permeation into wood, paper, and other lignocellulosic materials. Because pore sizes within such materials can range from nanometers to millimeters, a broad perspective will be used, also considering some publications related to other porous materials. Factors that limit the rate or extent of polymer or other solute transport into pores can involve thermodynamics (affecting the driving motivation for permeation), kinetics (if there is insufficient time for the system to come to equilibrium), and physical barriers. Molecular flow is also affected by the attributes of the solute, such as molecular mass and charge, as well as those of the substrate, such as the pore size, interconnectedness, restricted areas, and surface characteristics. Published articles have helped to clarify which of these factors may have a controlling influence on molecular transport in different situations.