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Sustainable Polyurethane-Like Materials: Renewable Sources, Reprocessability, and Polymer Circularity /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Sustainable Polyurethane-Like Materials: Renewable Sources, Reprocessability, and Polymer Circularity /Yixuan Chen.
Author:	Chen, Yixuan,
Description:	1 electronic resource (415 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-02, Section: A.
Notes:	Advisors: Torkelson, John M. Committee members: Broadbelt, Linda J.; Lopez, Jeffrey; Shull, Kenneth R.
Contained By:	Dissertations Abstracts International86-02A.
Subject:	Chemical engineering.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31331703
ISBN:	9798384016588

Sustainable Polyurethane-Like Materials: Renewable Sources, Reprocessability, and Polymer Circularity /
Chen, Yixuan,

Sustainable Polyurethane-Like Materials: Renewable Sources, Reprocessability, and Polymer Circularity /Yixuan Chen. - 1 electronic resource (415 pages)

Source: Dissertations Abstracts International, Volume: 86-02, Section: A.

Polyurethane (PU) is the sixth most produced plastic globally. Its extensive use and fast market growth raise significant sustainability concerns, including the use of toxic isocyanate precursors, reliance on non-renewable resources, and lack of recyclability. This dissertation aims to address the sustainability challenges of traditional PU by developing renewable, high-performance, and circularly recyclable non-isocyanate polyurethane (NIPU) materials of two types, polyhydroxyurethane (PHU) and non-isocyanate polythiourethane (NIPTU) with various structural designs and corresponding applications.The first part of this dissertation describes a rheology-guided method to rapidly synthesize self-blowing PHU crosslinked network foams, reducing the synthesis time from hours to minutes and significantly promoting the possibility for self-blowing PHU foams toward commercialization. Building on this method, biowaste-based self-blowing PHU network foams derived from renewable precursors, such as cashew nutshell liquid, were developed. Leveraging the inherent dynamic covalent chemistry of PHU, the spent PHU network foams can be reprocessed into bulk materials, which are robustly crosslinked network materials but can be repeatedly reprocessed with full retention of crosslink density after each thermal reprocessing step.The second part of this dissertation explores thermoplastic segmented PHUs with alternating hard and soft segments on their linear backbones. Due to the long, bulky, and asymmetric structure of the cashew nutshell liquid-based hard-segment precursor, the resulting thermoplastic segmented PHU exhibits remarkable phase mixing, achieved even without the existence of inter-segment hydrogen bonding. This leads to an exceptionally broad temperature range where this particular PHU is suitable for potential application as a damping material.The third part of this dissertation considers the intrinsic limitations of PHU, such as slow synthesis and excessive hydrophilicity, and describes the development of non-isocyanate polythiourethane (NIPTU) crosslinked networks. These NIPTU networks containing crosslinks of two types, thionourethane and disulfide, the latter obtained by auto-oxidation of pendant thiol groups on NIPTU backbone, exhibit excellent reprocessability with full recovery of crosslink density. Starting from renewable biowaste-based precursors, NIPTU networks and structurally analogous PHU networks were made, with NIPTU networks manifesting remarkably more rapid synthesis, higher crosslink densities, enhanced tensile properties, and improved water resistance. These combined outcomes suggest that NIPTU is a more favorable alternative to traditional PU than PHU. This dissertation also reports the first demonstration of NIPTU foams. Leveraging the interplay of fast chain growth to form NIPTU linear backbone and slightly slower thiol auto-oxidation to form inter-chain disulfide crosslinks, the gelling reaction synchronized well with the foaming process, resulting in homogeneous foam structures. Capitalizing on the disulfide dynamic chemistry, the NIPTU foam shows both compression-molding reprocessability and melt-extrudability for foam-to-film recycling. More excitingly, foam-to-foam recycling, or refoaming, was achieved for the first time for any NIPU materials via melt extrusion with bicarbonate salts as additional blowing agent.The final part of this dissertation describes the end-of-life chemical recycling of both PHU and NIPTU materials via small-molecule recovery. Leveraging the newly discovered dynamic chemistry of NIPTU, trans(thio)carbamoylation, a biowaste-derivable NIPTU network was successfully depolymerized under mild conditions via methanolysis, yielding high-purity small molecules with an outstanding, high recovery level. Combined with their excellent thermal reprocessability, this establishes the multi-dimensional recyclability of NIPTU networks. Harnessing the inherent transcarbamoylation dynamic chemistry, PHU materials also exhibit the ability to undergo small-molecule recovery, albeit with a lower recovery yield that can be attributed to the abundant hydroxyl groups on the PHU backbone which diminish the efficiency of the base catalyst that is essential for the depolymerization reaction.

English

ISBN: 9798384016588Subjects--Topical Terms:

206267
Chemical engineering.
Subjects--Index Terms:

Polyurethane

Sustainable Polyurethane-Like Materials: Renewable Sources, Reprocessability, and Polymer Circularity /
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520 $a Polyurethane (PU) is the sixth most produced plastic globally. Its extensive use and fast market growth raise significant sustainability concerns, including the use of toxic isocyanate precursors, reliance on non-renewable resources, and lack of recyclability. This dissertation aims to address the sustainability challenges of traditional PU by developing renewable, high-performance, and circularly recyclable non-isocyanate polyurethane (NIPU) materials of two types, polyhydroxyurethane (PHU) and non-isocyanate polythiourethane (NIPTU) with various structural designs and corresponding applications.The first part of this dissertation describes a rheology-guided method to rapidly synthesize self-blowing PHU crosslinked network foams, reducing the synthesis time from hours to minutes and significantly promoting the possibility for self-blowing PHU foams toward commercialization. Building on this method, biowaste-based self-blowing PHU network foams derived from renewable precursors, such as cashew nutshell liquid, were developed. Leveraging the inherent dynamic covalent chemistry of PHU, the spent PHU network foams can be reprocessed into bulk materials, which are robustly crosslinked network materials but can be repeatedly reprocessed with full retention of crosslink density after each thermal reprocessing step.The second part of this dissertation explores thermoplastic segmented PHUs with alternating hard and soft segments on their linear backbones. Due to the long, bulky, and asymmetric structure of the cashew nutshell liquid-based hard-segment precursor, the resulting thermoplastic segmented PHU exhibits remarkable phase mixing, achieved even without the existence of inter-segment hydrogen bonding. This leads to an exceptionally broad temperature range where this particular PHU is suitable for potential application as a damping material.The third part of this dissertation considers the intrinsic limitations of PHU, such as slow synthesis and excessive hydrophilicity, and describes the development of non-isocyanate polythiourethane (NIPTU) crosslinked networks. These NIPTU networks containing crosslinks of two types, thionourethane and disulfide, the latter obtained by auto-oxidation of pendant thiol groups on NIPTU backbone, exhibit excellent reprocessability with full recovery of crosslink density. Starting from renewable biowaste-based precursors, NIPTU networks and structurally analogous PHU networks were made, with NIPTU networks manifesting remarkably more rapid synthesis, higher crosslink densities, enhanced tensile properties, and improved water resistance. These combined outcomes suggest that NIPTU is a more favorable alternative to traditional PU than PHU. This dissertation also reports the first demonstration of NIPTU foams. Leveraging the interplay of fast chain growth to form NIPTU linear backbone and slightly slower thiol auto-oxidation to form inter-chain disulfide crosslinks, the gelling reaction synchronized well with the foaming process, resulting in homogeneous foam structures. Capitalizing on the disulfide dynamic chemistry, the NIPTU foam shows both compression-molding reprocessability and melt-extrudability for foam-to-film recycling. More excitingly, foam-to-foam recycling, or refoaming, was achieved for the first time for any NIPU materials via melt extrusion with bicarbonate salts as additional blowing agent.The final part of this dissertation describes the end-of-life chemical recycling of both PHU and NIPTU materials via small-molecule recovery. Leveraging the newly discovered dynamic chemistry of NIPTU, trans(thio)carbamoylation, a biowaste-derivable NIPTU network was successfully depolymerized under mild conditions via methanolysis, yielding high-purity small molecules with an outstanding, high recovery level. Combined with their excellent thermal reprocessability, this establishes the multi-dimensional recyclability of NIPTU networks. Harnessing the inherent transcarbamoylation dynamic chemistry, PHU materials also exhibit the ability to undergo small-molecule recovery, albeit with a lower recovery yield that can be attributed to the abundant hydroxyl groups on the PHU backbone which diminish the efficiency of the base catalyst that is essential for the depolymerization reaction.
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650 4 $a Polymer chemistry. $3 708579
650 4 $a Energy. $3 212397
650 4 $a Sustainability. $3 376755
653 $a Polyurethane
653 $a Non-renewable resources
653 $a Sustainability challenges
653 $a Cashew nutshell liquid
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690 $a 0640
690 $a 0495
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710 2 $a Northwestern University. $b Chemical and Biological Engineering. $3 603226
720 1 $a Torkelson, John M. $e degree supervisor.
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