Date of Award
Summer 8-16-2024
Level of Access Assigned by Author
Open-Access Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemical Engineering
Advisor
Douglas W. Bousfield
Second Committee Member
M. Clayton Wheeler
Third Committee Member
G. Peter van Walsum
Additional Committee Members
Mehdi Tajvidi
Jinwu Wang
Abstract
Plastics are widely used in food packaging because of their good barrier properties; however, plastics have environmental implications. Paper-based packaging can reach the barrier properties with coatings, but these coatings often make the paper hard to recycle and break down in the environment. Bio-based barrier coatings may be the key solution but recycling of these is not clear. The paper properties, barrier layer type, and other processing conditions that lead to good fiber recovery in a recycling system are not clear in the literature. This study aims to understand the paper and coating layer properties that lead to poor/good recycling applications defined by fiber recovery. The key hypothesis of the work is that high penetration of the barrier coating into the paper leads to poor recycling and poor barrier properties because fibers intermix with the barrier material. The influence of paper properties, a pre-coating layer such as cellulose nanofibrils (CNF), and types of barrier layers on fiber recovery were characterized. Base papers were characterized in terms of basis weight, thickness, permeability, and pore size. A CNF pre-coating layer was used in some cases to adjust the penetration of the barrier coating layer and to influence the release of the barrier layer upon repulping. Coated samples were characterized in terms of coat weight, water vapor permeability, and pore volume. A lab-based method to characterize the percent of fiber recovery was developed that was similar to current standards; the influence of various parameters on fiber recovery and fiber characters was determined. Moreover, a life cycle analysis using Argonne National Laboratory’s GREET software assessed the environmental sustainability of the entire process for producing 1 kg of PE-laminated paper from both virgin and recycled fibers. In this study, a lab-based recycling test method was proposed to determine fiber recovery for coated paper, comparing it with existing recycling methods. This method involved preparing samples with a 10-minute soaking time, followed by a 20-minute repulping process in the disintegrator, and a 20-minute screening using a Somerville screen. This method was then used to identify the influential factors on the recyclability of coated paper. Consistency was found to be a significant parameter affecting recyclability while soaking time did not impact fiber analysis and recovery results. The energy input for the disintegrator used in this method was calculated and set to 336 kWh/ton for all repulping experiments. The PE-laminated/extruded samples resulted in good fiber recovery. The dispersion-coated papers exhibited very high fiber recovery, around 98%. A key finding was that a CNF precoating layer facilitates the separation of the barrier coating from the base paper, resulting in high fiber recovery. Life Cycle Analysis results confirmed that using higher ratios of recycled fibers has a lower environmental impact for the base case compared to virgin fibers.
Recommended Citation
Najd Mazhar, Aysan, "Parameters That Influence Recycling of Barrier-coated Paper" (2024). Electronic Theses and Dissertations. 4069.
https://digitalcommons.library.umaine.edu/etd/4069