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Orifice geometry as a tool for evaluating extensional flow resistance of barrier coating colors, TAPPI Journal November 2024

ABSTRACT: Knowledge of extensional flow behavior of coating colors can be beneficial for improving runnability and eliminating defects in various coating processes. The current work evaluates the use of an orifice geometry attached to a commercial capillary viscometer as a tool to obtain extensional flow properties of barrier coating dispersions. By measuring the pressure drop across the orifice as a function of flow velocity, the method presents the flow resistance as Euler number at industrially relevant high deformation rates. The results agree with the earlier results obtained with a capillary entrance pressure loss technique. The type of polymer additive is shown to control the extensional flow resistance, with high molecular weight linear flexible polymers such as polyethylene oxide (PEO) and polyvinyl alcohol (PVOH) having highest impact. The orifice method offers advantages over other approaches, including the need for only a small sample amount, ease of measurement, and access to high deformation rates.

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Measurement and control of extensional viscosity in barrier coating dispersions, TAPPI Journal November 2023

ABSTRACT: This study aimed to understand the effect of various rheological additives on the extensional viscosity of barrier coating dispersions, as well as to understand the role extensional viscosity plays in stabilizing a liquid curtain. The apparent extensional viscosity was measured using two devices that create accelerating flows: a capillary viscometer and an orifice rheometer. Additives tested include several polyvinyl alcohols, a high molecular weight polyethylene oxide, and carboxymethylcellulose. Extensional viscosity plays a significant role in stabilizing a liquid curtain, as it slows down hole expansion and prevents impurities and disturbances from causing holes in the first place. Some of the additives could substantially increase the extensional viscosity of the dispersions without increasing the shear viscosity outside the typical range of processability for a curtain coater. Some of the additives exhibited coil-stretch transition, meaning they start increasing extensional viscosity above a certain extension rate. Polymers with low chain lengths exhibited finite extensibility, which indicates the polymer chain has fully extended and cannot provide further extensional viscosity, even though the extending force is increased. Polymeric additives with stiff or branched chains significantly raised shear viscosity without increasing extensional viscosity. Both methods could reliably measure extensional viscosity in curtain coating barrier dispersions.

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Open Access
An evaluation of household tissue softness, TAPPI Journal February 2021

ABSTRACT: This study extends our 2019 paper, a study of the softness of household tissues using a tissue softness analyzer (TSA) and hand-felt panels. It revisits the softness theory of Holger Hollmark by applying a reciprocal matrix approach to measure sheet bulk softness and surface softness, and then make comparisons with the results obtained using a TSA instrument. We ascertained that there was a high correlation of R=0.904 between panel-corrected hand-felt (CHF) softness and TSA softness (TSA-HF); and a low correlation of R=-0.678 between panel-corrected hand-felt surface softness (CHSS) and TSA smoothness (TS-750). Three hunches about TSA measurements were confirmed: 1) Hollmark’s theory was confirmed by a high correlation coefficient (R=0.895) between CHF and CHSS softness, indicating that the two parameters are mutually dependent; 2) TS-750 differs from CHSS and has partial influence on TSA-HF results with a correlation of R = -0.510; and 3) although TS-750 has only limited influences on TSA-HF, further opportunities for their application can be provided using pertinent regression equations.

Journal articles
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Open Access
Does the kappa number method accurately reflect lignin content in nonwood pulps?, TAPPI Journal November 2018

Does the kappa number method accurately reflect lignin content in nonwood pulps?, TAPPI Journal November 2018

Journal articles
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Open Access
Rewet in wet pressing of paper, TAPPI JOURNAL September 2018

Rewet in wet pressing of paper, TAPPI JOURNAL September 2018

Journal articles
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Open Access
Melt-blown compostable polyester films with lignin, TAPPI J

Melt-blown compostable polyester films with lignin, TAPPI JOURNAL March 2017

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Open Access
Low-temperature precausticizing — a hopeful approach for green liquor desilication, TAPPI JOURNAL February 2017

Low-temperature precausticizing — a hopeful approach for green liquor desilication, TAPPI JOURNAL February 2017

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Open Access
Removal of silicon from green liquor with low-temperature precausticizing, TAPPI JOURNAL January 2017

Removal of silicon from green liquor with low-temperature precausticizing, TAPPI JOURNAL January 2017

Journal articles
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Open Access
Understanding conductivity and soda loss

Understanding conductivity and soda loss

Journal articles
Magazine articles
Open Access
Estimating limits of wet pressing on paper machines, TAPPI JOURNAL February 2017

Estimating limits of wet pressing on paper machines, TAPPI JOURNAL February 2017

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