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Surface energy considerations for offset printing of coated paper and paperboard, TAPPI Journal November 2023

ABSTRACT: Offset printing of coated paper involves the complex interactions of ink with a surface that is characterized by three major properties: roughness, porosity, and related pore network structure and surface chemistry (related to surface free energy [SFE]). The effects of porosity and roughness are relatively well understood and are documented in the literature, whereas the influence of surface chemistry is much less studied and therefore the focus of this paper. The key results shown include: i) Coating porosity has a negligible effect on SFE determination by contact angle using two fluids. ii) The chemistry of the latex polymer in the coating formulation dominates the influence on SFE compared to pigment, with any surface energy differences present in the pigment being almost completely masked by latex. iii) Wetting agent and corona treatment can impact water absorption rate and surface spreading of water, resulting in small differences in printability. Increasing the concentration of the surfactant on a coated surface indicates switching orientation of the surfactant molecules, giving a “step wise” printing result. When looking to improve offset printability by selection of different pigments, the variation in SFE is less important than variation in either surface roughness or porosity.

Journal articles
Magazine articles
Open Access
Rice straw-based sustainable food packaging material with improved strength and barrier properties: Development and characterization, TAPPI Journal October 2023

ABSTRACT: Sustainable food packaging paper with high barrier and strength properties was developed with rice straw nanocellulose materials. Pulping and bleaching of rice straw were performed using an organosolv pulping and DED (D: chlorine dioxide bleaching; E: sodium hydroxide extraction) bleaching sequence. Bleached rice straw pulp was refined to 90°SR using a laboratory Valley beater. The laboratory handsheets were prepared using pulp slurry at 40°SR and 90°SR. The handsheets of cellulose nanofibrils (CNFs) made of highly refined pulp (90°SR) were surface sized using alkyl ketene dimer (AKD) wax to increase the barrier properties of paper for selective food packaging applications. The paper samples were tested for mechanical, optical, surface, and barrier properties, including tensile index, burst index, tearing index, bending stiffness, elongation, porosity, apparent density, opacity, Cobb value, water vapor transmission rate (WVTR), oil and grease resistance, and contact angle. The refined pulp (90°SR) was analyzed using field-emission scanning electron microscopy (FE-SEM), and it was observed that the morphology of the developed fibers changes to the nanoscale (<100 nm) for at least one dimension. The particle size distribution of the refined pulp using DLS analyzer also confirmed the cellulose fibers to near nanoscale. It was concluded that nanofibers were formed by a high degree of the mechanical pulp refining process and found to be much more economical than alternative processes in this direction. The sample handsheets of CNFs showed good strength and barrier properties. The barrier properties further increased when surface sizing was done using low-cost, nontoxic, and biodegradable AKD wax.

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Magazine articles
Open Access
Using bleaching stage models for benchmarking hardwood ECF bleach plants, TAPPI Journal October 2023

ABSTRACT: Steady-state models estimated the performance of the D0(EOP)D1 bleach sequence at two mixed hardwood bleach plants in the southern United States. At Mill 1, the full sequence’s chlorine dioxide charge that brightens the pulp to ~84% ISO was monitored for two weeks. Mill 2 considered the partial sequence that brightens the pulp to ~86% ISO for nearly four weeks. Elevated levels of chlorine dioxide were linked to increased washer carryover in brownstock and extraction areas. For Mills 1 and 2, an extra 0.24% and 0.33% chlorine dioxide was consumed in the D0 stage. This extra bleach demand was equivalent to an additional 4.8 and 5.5 kappa load to the brownstock, respectively. Some differences were observed for the D1 stage. Mill 1 had extraction carryover that averaged 1.1 units higher than was measured, contributing to use of an extra 0.22% of chlorine dioxide. Mill 2 had extraction carryover that averaged between 0 and 0.7 kappa units and consumed up to 0.13% more chlorine dioxide. Another data set from Mill 2 showed high brownstock and extraction carryover, leading to ~0.90% more total chlorine dioxide usage to brighten to 84% ISO. Overall, this investigation illustrated that the models could be employed as benchmarks.

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Optimizing the Large-Scale Frequency Analysis of Paper Machi

Optimizing the Large-Scale Frequency Analysis of Paper Machine Bearings, 1990 Engineering Conference Proceedings

Journal articles
Open Access
Development and Application of a Real-Time Recovery Boiler E

Development and Application of a Real-Time Recovery Boiler Expert System, 1991 Engineering Conference Proceedings

Journal articles
Open Access
Recovery of Sulfur from Spent Semichemical Pulping Liquors,

Recovery of Sulfur from Spent Semichemical Pulping Liquors, 1991 Engineering Conference Proceedings

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What You Need to Know Before Buying Your Next Chlorine Dioxi

What You Need to Know Before Buying Your Next Chlorine Dioxide Plant, 1992 Engineering Conference Proceedings

Journal articles
Open Access
Performance of High Vacuum Dewatering Elements in the Formin

Performance of High Vacuum Dewatering Elements in the Forming Section, 1993 Engineering Conference Proceedings

Journal articles
Open Access
Cold Blow Batch Cooking Plus Medium Consistency Oxygen: Heat

Cold Blow Batch Cooking Plus Medium Consistency Oxygen: Heat Exchanger Placement, 1993 Engineering Conference Proceedings

Journal articles
Open Access
Hydrodynamics of the Forming Section: The Origin of Nonunifo

Hydrodynamics of the Forming Section: The Origin of Nonuniform Fiber Orientation, 1994 Engineering Conference Proceedings

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