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" Fabrication of Water- and Oil/Grease-Resistant Paper Coating for Packaging Application "
Li, Zhao
Rabnawaz, Muhammad
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1106412
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TLpq2390183303
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| Main Entry
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Li, Zhao
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Rabnawaz, Muhammad
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| Title & Author
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Fabrication of Water- and Oil/Grease-Resistant Paper Coating for Packaging Application\ Li, ZhaoRabnawaz, Muhammad
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| College
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Michigan State University
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| Date
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2020
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| student score
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2020
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| Degree
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Ph.D.
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| Page No
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194
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| Abstract
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Paper materials are highly desirable for a wide range of applications in packaging and non-packaging sectors due to their advantages of low cost, light-weight, excellent mechanical properties, biodegradability, and renewability. However, paper is a porous material with polar groups that cause it to absorb water and oil. Lamination and coating are commonly used methods to improve the water- and oil-resistance of paper. After use, the separation of laminates and coatings from the paper fibers/pulp presents a significant challenge. In addition, persistent and environmentally harmful fluorinated chemicals are also used to render paper water- and oil-resistant. Thus, there is an urgent need to address the above challenges by developing closed-loop approaches for water- and grease/oil-resistant paper. This research aims to develop facile, economical, and closed-loop approached for fabricating fluorine- and plastic-free water- and grease/oil- resistant paper coating. To achieve PFAS- and plastic-free water-repellent coating for paper, paper substrates were first coated with melamine as a primer, an FDA approved material for food contact applications, to provide amine group sites on the cellulosic fibers. Polydimethylsiloxane-isocyanate (PDMS-NCO) was applied as a water-repellent outer layer, which was bonded to cellulosic fibers via biodegradable urea linkages formed between the NCO and amine groups. The obtained coated paper substrate showed excellent water-resistant properties with high water contact angles (~ 125°) along with a significant reduction in water absorption. However, the coating paper was lacking oil resistance, which is evidently due to the porous textures of the coated paper. To impart paper substrates both water- and oil-resistant properties, a two-step PFAS-free approach was developed using chitosan as a first layer, while PDMS-NCO as a second layer Chitosan was applied as a coating to mask paper’s pores as well as create free amine groups on the paper substrate. A PDMS coating layer was then chemically grafted to the chitosan-coated-paper via urea linkages to render water and oil-resistant. The coated paper with a coating load of 8.6% of chitosan and 2.2% of PDMS showed excellent oil/grease resistance (kit rating value of 12/12) as well as excellent water contact angle (WCA 95.2°). Solvent extraction tests confirmed the robustness of the coating on the cellulosic substrates. Next, a closed-loop approach for one-step water- and oil-resistant paper-based materials was developed. Chitosan-graft-PDMS copolymer was prepared by grafting PDMS onto the chitosan polymer, which was then applied as an aqueous coating solution on paper substrates in a single step. Remarkable water- and oil-resistant properties were obtained which is evident from high WCA of 120.53°, low Cobb 60 values of 9.89 g/m2 and very high kit value of 11.7/12. In addition, the pulp of the coated paper was 100% recyclable by repulping and washing treatment. Furthermore, overall migration of siloxane into two food simulants (50% aqueous ethanol and Miglyol 812) was below 46.19 µg/mL (7.16 mg/dm2), which is well below the overall migration limit 60 mg/kg food (100 mg/dm2) by the Council of Europe’s Resolution AP (2004). The migration studies indicate the potential safe use of the coated paper for food contact application. Finally, sustainable and biobased chitosan-graft-castor oil (CHI-g-CO) copolymer was synthesized and applied for paper coating. A castor oil-capped-isocyanate (CO-capped-NCO) was prepared by the reaction between castor oil and isophorone diisocyanate. The resultant CO-capped-NCO was grafted onto the chitosan polymer backbone via a urea linkage formed between –NCO and amine groups to prepare CHI-g-CO. The obtained waterborne solution of CHI-g-CO was coated onto paper, which showed good water- and oil-resistance with a Cobb60 value of 29.16 g/m2 and a kit rating value of 9/12, respectively. Meanwhile, this fabrication strategy offers a sustainable and environmental-friendly approach toward grease- and water-resistant paper-based materials considering the biobased nature of chitosan and castor oil.
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Packaging
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