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Chemical surface modification of polyethylene for improved adhesion to epoxy coatings Azimi, Mohammadyousef
Abstract
The surface modification of high-density polyethylene (HDPE) is critical in improving its adhesion to coatings, particularly in pipeline coatings where HDPE is used as the outermost layer of three-layer polyethylene (3LPE) systems. Despite HDPE's widespread use due to its chemical stability, low energy consumption in processing, and cost-effectiveness, its non-polar, hydrophobic surface and low surface free energy (SFE) limit its adhesion properties. This presents a major challenge in field joint coating (FJC) applications, where strong adhesion between HDPE and liquid epoxy is required to protect welded pipeline joints. Existing methods for HDPE surface modification, such as flame treatment or corona discharge, are either inconsistent or impractical for field use, necessitating the development of a more reliable, field-friendly solution. This thesis proposes several novel chemical surface modification methods for HDPE to significantly enhance its surface functionality, SFE, hydrophilicity, and adhesion to liquid epoxy coatings. The research explores the use of transition metal (TM)-activated peroxides, oxidative pastes, and grafting techniques to modify the HDPE surface. The first approach utilizes TM peroxide systems to activate peroxides such as proxymonosulfate (PMS), persulfate (PS), and hydrogen peroxide (HP), generating reactive radicals capable of functionalizing the HDPE surface. A two-step grafting method for glycidyl methacrylate (GMA) and maleic anhydride (MAH) is also introduced. Furthermore, oxidative pastes were developed to offer a practical alternative for field applications, providing significant improvements in adhesion and hydrophilicity. Key findings demonstrate that TM-peroxide systems—particularly those involving RuCl₃-PMS, CoCl₂-PMS, KMnO₄-PMS and KMnO₄-PS—dramatically increase HDPE surface polarity and improve adhesion to epoxy by over 200%. The study also shows that these chemical treatments do not adversely affect the bulk properties of HDPE, maintaining its mechanical strength and crystallinity. Finally, the thesis critically evaluates SFE models and contact angle (CA) measurement techniques, showcasing the unreliability of widely-used as-placed CA results for some surfaces and proposing a new method for calculating SFE using advancing and receding CAs to better align with surface functionality and adhesion test results. This work presents a practical solution for improving HDPE surface properties for FJC applications, with potential applications in other industries such as lithium-ion batteries and packaging.
Item Metadata
Title |
Chemical surface modification of polyethylene for improved adhesion to epoxy coatings
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Creator | |
Supervisor | |
Publisher |
University of British Columbia
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Date Issued |
2024
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Description |
The surface modification of high-density polyethylene (HDPE) is critical in improving its adhesion to coatings, particularly in pipeline coatings where HDPE is used as the outermost layer of three-layer polyethylene (3LPE) systems. Despite HDPE's widespread use due to its chemical stability, low energy consumption in processing, and cost-effectiveness, its non-polar, hydrophobic surface and low surface free energy (SFE) limit its adhesion properties. This presents a major challenge in field joint coating (FJC) applications, where strong adhesion between HDPE and liquid epoxy is required to protect welded pipeline joints. Existing methods for HDPE surface modification, such as flame treatment or corona discharge, are either inconsistent or impractical for field use, necessitating the development of a more reliable, field-friendly solution.
This thesis proposes several novel chemical surface modification methods for HDPE to significantly enhance its surface functionality, SFE, hydrophilicity, and adhesion to liquid epoxy coatings. The research explores the use of transition metal (TM)-activated peroxides, oxidative pastes, and grafting techniques to modify the HDPE surface. The first approach utilizes TM peroxide systems to activate peroxides such as proxymonosulfate (PMS), persulfate (PS), and hydrogen peroxide (HP), generating reactive radicals capable of functionalizing the HDPE surface. A two-step grafting method for glycidyl methacrylate (GMA) and maleic anhydride (MAH) is also introduced. Furthermore, oxidative pastes were developed to offer a practical alternative for field applications, providing significant improvements in adhesion and hydrophilicity.
Key findings demonstrate that TM-peroxide systems—particularly those involving RuCl₃-PMS, CoCl₂-PMS, KMnO₄-PMS and KMnO₄-PS—dramatically increase HDPE surface polarity and improve adhesion to epoxy by over 200%. The study also shows that these chemical treatments do not adversely affect the bulk properties of HDPE, maintaining its mechanical strength and crystallinity. Finally, the thesis critically evaluates SFE models and contact angle (CA) measurement techniques, showcasing the unreliability of widely-used as-placed CA results for some surfaces and proposing a new method for calculating SFE using advancing and receding CAs to better align with surface functionality and adhesion test results.
This work presents a practical solution for improving HDPE surface properties for FJC applications, with potential applications in other industries such as lithium-ion batteries and packaging.
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Genre | |
Type | |
Language |
eng
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Date Available |
2025-01-10
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0447731
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2025-05
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Campus | |
Scholarly Level |
Graduate
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Rights URI | |
Aggregated Source Repository |
DSpace
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Rights
Attribution-NonCommercial-NoDerivatives 4.0 International