De-wrinkling of cellulosic barrier materials coated on paper during scale-up on a roll-to-roll system

Packaging is crucial in safeguarding and facilitating the storage and transportation of diverse consumer goods, including food, medical supplies, pharmaceuticals, electronics, and textiles. With the growing emphasis on sustainability and the demand for renewable resources, paper has gained prominence due to its low environmental impact and cost-effectiveness in manufacturing. Researchers have been advancing paper properties by adding biopolymers to coating to make them a viable alternative to petroleum-based plastics across a broader spectrum of packaging applications. However, one of the challenges encountered during the fabrication process is the formation of surface wrinkles. The wrinkling instability could arise because of the mismatch strain between film and substrate, paper swelling, and external forces such as constrained edges during the coating and drying processes. This instability leads to surface buckling, which minimizes the total energy. Such instability of final films affects the uniformity and quality of overall barrier performance, resulting in a lack of consistency, poor adhesion, changes in mechanical properties, and non-uniform barrier properties. Highly wrinkled barrier films could also affect the quality of subsequent coatings or packing steps. In this study, the objective is to investigate factors and impacts of surface wrinkling on barrier-coated papers through scalable manufacturing and develop methodologies to de-wrinkle without compromising barrier properties. Here, manufacturing tools, i.e., a slot die or a wire-rod mounted on a roll-to-roll (R2R) system, are used to coat cellulosic barrier materials on paper. Modifications to the tooling, processing conditions, and fluid properties are all explored to de-wrinkles during the coating process. The relationship between the wrinkling wavelengths and the overall film quality is evaluated through post-image analysis, microscopy, oxygen transmission rate (OTR) tests, TAPPI T559 Kit tests, adhesion tests as well as mechanical tests. The study has shown that low constraints on the substrate along the edges during coating can effectively reduce surface wrinkling in both wet and dry states while obtaining adequate barrier quality. This effect is attributed to the allowance of more space for wet film to freely buckle when balancing introduced strain due to coating and paper swelling. Furthermore, the integration of vacuum assistance during the coating process can effectively minimize wrinkles formation for 2-pass coating and alter the orientation of wrinkling formation due to the shift of dominated strain. This work opens a pathway to high yield, high performance, sustainable cellulosic barrier thin film coated on paper and provides potential for smart packaging applications.

Level thesis:degree_level

Masters

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Georgia Institute of Technology

Year dc:date.issued

2025

Author dc:creator

• Yu, Xiaoqing Deemo

Advisors dc:contributor.advisor

• Harris, Tequila A. L.
• Shofner, Meisha L.

Committee member dc:contributor.committeemember

• Hu, Yuhang

• renewable food packaging
• barrier properties
• paper de-wrinkling
• vacuum assist coating process
• substrate edge control

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/1853/81578

OAI identifier oai:identifier

oai:repository.gatech.edu:1853/81578