Date of Award

12-2015

Degree Name

Doctor of Philosophy

Department

Chemical and Paper Engineering

First Advisor

Dr. Margaret Joyce

Second Advisor

Dr. Paul D. Fleming

Third Advisor

Dr. Steven Bloembergen

Fourth Advisor

Dr. Do Ik Lee

Keywords

Coating rheology, curtain coating, biobased latex binder, curtain stability, coating formulation, paper coatine

Abstract

In this research, a conventional petro-based latex was partially replaced with a biobased latex in a curtain coating. A common petro-based rheology modifier used in curtain coatings, which is relatively costly and difficult to disperse, was also replaced with two inorganic rheology modifiers. The influence of these materials on coating rheology and curtain stability was thoroughly examined.

In the rheological study, the interactions between biopolymer nanoparticles and inorganic rheology modifiers were found to improve the rheological properties of the biobased latex coatings. Changes in the rheological properties of the coatings were found to depend on the type of rheology modifier used and ratio of rheology modifier to biobased latex. The extensional viscosity of each coating was measured by two methods; Capillary Break-up Extensional Rheometry (CaBER) and Squeeze/Pull-off Test (SPOT). As a novel method, the results from SPOT correlated well with CaBER results demonstrating its usefulness as a new analytical tool.

In a stability study, the effects of biobased latex and rheology modifiers on curtain stability were examined. A correlation between the surface tension and CaBER filament lifetime was revealed. Curtain stability studies were performed on a slot die over a flow rate range of 20 to 65 mL/s. It was found that the curtain stability significantly improved after adding petro-based rheology modifier, as well as the inorganic rheology modifiers when biobased latex was present. The relative importance of coating surface tension, shear rate dependence of viscosity, viscoelasticity, as well as extensional viscosity to curtain stability at different flow rates was learned.

As a final study, coating formulations were adjusted for the application on a slide die by changing the latex type and surfactant amount. Curtain stability was improved by increasing latex substitution in the presence of inorganic rheology modifier. The impacts of biobased latex and inorganic rheology modifier on the properties of coated linerboard were examined in terms of brightness, gloss, and dry pick strength. Coatings containing one of the two inorganic rheology modifier chemistries were found to be very promising. It is believed that this research advances the application knowledge for biobased latex in commercial curtain coating operations.

Access Setting

Dissertation-Open Access

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