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Effects of preincubation on the gelatinization of cassava and corn starch suspensions containing sodium hydroxide as a main component of corrugating adhesives
ABSTRACT: Effects of the preincubation temperature and the caustic-ratio, the molar ratio of sodium hydroxide to starch glucose residue, on the gelatinization of cassava starch and corn starch suspensions were studied using differential scanning calorimetry in view of utilization for corrugating adhesives. The gelatinization temperature and enthalpy change of cassava starch suspensions after the preincubation at 30°C decreased as the caustic-ratio increased, similar to those of corn starch ones: The gelatinization starting temperature (Ts) decreased considerably more than the peak temperature and the conclusion temperature (Tc). Although Ts lowered and the width of gelatinization temperature expanded, compared with those of corn starch suspensions, the two starch suspensions with the same half gelatinization transition temperature showed similar gelatinization characteristics of almost the same Ts and Tc. During 1 h-preincubations at 30°C•50°C, the starch granules with Ts that were lowered considerably below each preincubation temperature by sodium hydroxide showed limited gelatinization. The gelatinization transition did not rapidly spread over the whole suspension, but progressed stepwise in response to the increase of the causticratio and the rise of the preincubation temperature. In a prolonged preincubation at a constant temperature, Ts gradually rose at higher caustic-ratios in which stepwise gelatinization commenced. Although the starch gelatinization was irreversible and not in a stable equilibrium state for a long time, we concluded that such stepwise gelatinization progress controlled the practical preparation and use of corrugating adhesives.
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Editorial: Diverse content characterizes PaperCon 2019, TAPPI Journal November 2019
ABSTRACT: PaperCon 2019 was held from May 5-8 in Indianapolis, IN. Many of us visiting Indianapolis had little or no perception of the area beyond, of course, race cars and good sports teams. We also found a lovely, walkable downtown with a myriad of restaurants, parks, historic sites, and state government. As with the diverse offerings of PaperCon 2019’s host city of Indianapolis, the conference technical program was exceptionally broad this year. In this special issue of TAPPI Journal, we share both the breadth and quality of the content presented at PaperCon 2019 through peer-reviewed papers from the conference, as described below.
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Rheological characterization of tack and viscoelasticity of compositions of crepe coating used in the Yankee dryer, TAPPI Journal November 2019
ABSTRACT: The vast majority of tissue production uses creping to achieve the required set of properties on the base sheet. The Yankee coating helps to develop the desired crepe that in turn determines properties such as bulk and softness. The adhesion of the sheet to the Yankee surface is a very important characteristic to consider in achieving the desired crepe. The coating mix usually consists of the adhesive, modifier, and release. A good combination of these components is essential to achieving the desired properties of the tissue or towel, which often are determined by trials on the machine that can be time consuming and lead to costly rejects. In this paper, five compo-sitions of an industrial Yankee coating adhesive, modifier, and release were examined rheologically. The weight ratio of the adhesive was kept constant at 30% in all five compositions and the modifier and release ratios were varied. The normal force and work done by the different compositions have been shown at various temperatures simulating that of the Yankee surface, and the oscillatory test was carried out to explain the linear and nonlinear viscoelastic characteristic of the optimal coating composition.
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A novel predictive method for filler coflocculation with cellulose microfibrils, TAPPI Journal November 2019
ABSTRACT: Different strategies aimed at reducing the negative impact of fillers on paper strength have been the objective of many studies during the past few decades. Some new strategies have even been patented or commercialized, yet a complete study on the behavior of the filler flocs and their effect on retention, drainage, and formation has not been found in literature. This type of research on fillers is often limited by difficulties in simulating high levels of shear at laboratory scale similar to those at mill scale. To address this challenge, a combination of techniques was used to compare preflocculation (i.e., filler is flocculated before addition to the pulp) with coflocculation strategies (i.e., filler is mixed with a binder and flocculated before addition to the pulp). The effect on filler and fiber flocs size was studied in a pilot flow loop using focal beam reflectance measurement (FBRM) and image analysis. Flocs obtained with cationic polyacrylamide (CPAM) and benonite were shown to have similar shear resistance with both strategies, whereas cationic starch (CS) was clearly more advantageous when coflocculation strategy was used. The effect of flocculation strategy on drainage rate, STFI formation, ash retention, and standard strength properties was measured. Coflocculation of filler with CPAM plus bentonite or CS showed promising results and produced sheets with high strength but had a negative impact on wire dewatering, opening a door for further optimization.
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Lignin-based resins for kraft paper applications, TAPPI Journal November 2019
ABSTRACT: We investigated miscanthus (MS) and willow (W) lignin-furfural based resins as potential reinforce-ment agents on softwood and hardwood kraft paper. These resins might be sustainable alternatives to the commercial phenolformaldehyde (PF) resins. Phenol is a petrochemical product and formaldehyde has been classified as a carcinogen by the U.S. Environmental Protection Agency. The lignin used in this study was derived from hot water extraction (160ºC, 2 h) of MS and W biomass, and may be considered sulfur-free. These biorefinery lignins were characterized for their chemical composition and inherent properties via wet chemistry and instrumental techniques. The resin blends (MS-resin and W-resin) were characterized for their molecular weight, thermal behavior, and mechanical properties. Mechanical properties were measured by the resin’s ability to reinforce softwood and hard-wood kraft papers. The effect of adding hexamethylenetetramine (HMTA), a curing agent, to the resin was also examined. Mixtures of PF and lignin-based resins were investigated to further explore ways to reduce use of non-renewables, phenol, and carcinogenic formaldehyde. The results show that lignin-based resins have the potential to replace PF resins in kraft paper applications. For softwood paper, the highest strength was achieved using W-resin, without HMTA (2.5 times greater than PF with HMTA). For hardwood paper, MS-resin with HMTA gave the highest strength (2.3 times higher than PF with HMTA). The lignin-based resins, without HMTA, also yielded mechanical properties comparable to PF with HMTA.
Journal articles
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The solubility of calcium carbonate in green liquor handling systems, TAPPI Journal October 2019
ABSTRACT: The formation of hard calcite (CaCO3) scale in green liquor handling systems is a persistent problem in many kraft pulp mills. CaCO3 precipitates when its concentration in the green liquor exceeds its solubility. While the solubility of CaCO3 in water is well known, it is not so in the highly alkaline green liquor environment. A systematic study was conducted to determine the solubility of CaCO3 in green liquor as a function of temperature, total titratable alkali (TTA), causticity, and sulfidity. The results show that the solubility increases with increased temperature, increased TTA, decreased causticity, and decreased sulfidity. The new solubility data was incorporated into OLI (a thermodynamic simulation program for aqueous salt systems) to generate a series of CaCO3 solubility curves for various green liquor conditions. The results help explain how calcite scale forms in green liquor handling systems.
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Static and dynamic sorption of lignin removed Populus euramericana, TAPPI JOURNAL February 2018
Static and dynamic sorption of lignin removed Populus euramericana, TAPPI JOURNAL February 2018
Journal articles
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Lignocellulose fibers elaborating super-swollen three-dimensional cellulose hydrogels from solution in N, N-dimethylacetamide/lithium chloride, TAPPI JOURNAL February 2018
Lignocellulose fibers elaborating super-swollen three-dimensional cellulose hydrogels from solution in N, N-dimethylacetamide/lithium chloride, TAPPI JOURNAL February 2018
Journal articles
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Functionalization of wood/plant-based natural celluslose fibers with nanomaterials: a review, TAPPI JOURNAL February 2018
Functionalization of wood/plant-based natural celluslose fibers with nanomaterials: a review, TAPPI JOURNAL February 2018
Journal articles
Magazine articles
Editorial: The changing face of the coated paper industry, TAPPI JOURNAL January 2018
Editorial: The changing face of the coated paper industry, TAPPI JOURNAL January 2018