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Processing and Characterization of Polyethylene Vitrimers.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Processing and Characterization of Polyethylene Vitrimers./
Author:	Montoya Ospina, Maria Camila.
Description:	1 online resource (117 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-11, Section: B.
Contained By:	Dissertations Abstracts International84-11B.
Subject:	Plastics. -
Online resource:	click for full text (PQDT)
ISBN:	9798379520052

Processing and Characterization of Polyethylene Vitrimers.
Montoya Ospina, Maria Camila.

Processing and Characterization of Polyethylene Vitrimers. - 1 online resource (117 pages)

Source: Dissertations Abstracts International, Volume: 84-11, Section: B.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2023.

Includes bibliographical references

Polyethylene (PE) is one of the most used commodity plastics worldwide. PE is versatile, lightweight, tough, easy to process, and exhibits excellent chemical resistance. Some of the limitations of this material are its lower strength, poor dimensional stability at elevated temperature, and strong creep behavior. Cross-linked PE (XLPE) offers an improvement to these limitations with the sacrifice of not being recyclable due to its permanent cross-links. A new class of materials, called vitrimers, combines the properties of thermoplastics and thermosets: they behave like traditional cross-linked materials at service temperature while being re-moldable and recyclable like thermoplastics when heated. Vitrimers consist of chemically cross-linked networks that engage in thermoactivated associative exchange reactions. These exchange reactions can impart malleability, healing, and recyclability properties to thermosets. While significant focus has been placed on the development of vitrimer chemistry, there is little understanding on how to process at scale. This research aims to enable industrial applications of polyethylene vitrimers by defining the relationships between processability, recyclability, and final part properties. In this dissertation, a one-step protocol to prepare PE vitrimer-like materials with disulfide exchange bonds via reactive blending is presented. The cross-linking reaction of maleic anhydride-grafted-polyethylene (PE-MAH) and 4,4' - dithiodianiline (DTA) is conducted in the melt state. The final rheological, thermal and mechanical properties of PE vitrimers (PE-V) are investigated. The disulfide exchange reactions enable re-processing of PE-V and the mechanical and rheological properties remain constant after two processing cycles. It is demonstrated that PE-V can be processed using single screw extrusion processes without the need to modify the standard equipment. The formation of cross-links in PE-V decreases the degree of crystallinity of the material which leads to a decrease in stiffness. However, PE-V exhibits higher thermal stability, higher dimensional stability above melting temperature, and lower shrinkage compared to PE. The improvement in these properties allows the use of PE-V in material extrusion additive manufacturing (ME-AM) to reduce mechanical anisotropy and improve dimensional accuracy.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798379520052Subjects--Topical Terms:

563477
Plastics.
Subjects--Index Terms:

CharacterizationIndex Terms--Genre/Form:

554714
Electronic books.

Processing and Characterization of Polyethylene Vitrimers.
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520 $a Polyethylene (PE) is one of the most used commodity plastics worldwide. PE is versatile, lightweight, tough, easy to process, and exhibits excellent chemical resistance. Some of the limitations of this material are its lower strength, poor dimensional stability at elevated temperature, and strong creep behavior. Cross-linked PE (XLPE) offers an improvement to these limitations with the sacrifice of not being recyclable due to its permanent cross-links. A new class of materials, called vitrimers, combines the properties of thermoplastics and thermosets: they behave like traditional cross-linked materials at service temperature while being re-moldable and recyclable like thermoplastics when heated. Vitrimers consist of chemically cross-linked networks that engage in thermoactivated associative exchange reactions. These exchange reactions can impart malleability, healing, and recyclability properties to thermosets. While significant focus has been placed on the development of vitrimer chemistry, there is little understanding on how to process at scale. This research aims to enable industrial applications of polyethylene vitrimers by defining the relationships between processability, recyclability, and final part properties. In this dissertation, a one-step protocol to prepare PE vitrimer-like materials with disulfide exchange bonds via reactive blending is presented. The cross-linking reaction of maleic anhydride-grafted-polyethylene (PE-MAH) and 4,4' - dithiodianiline (DTA) is conducted in the melt state. The final rheological, thermal and mechanical properties of PE vitrimers (PE-V) are investigated. The disulfide exchange reactions enable re-processing of PE-V and the mechanical and rheological properties remain constant after two processing cycles. It is demonstrated that PE-V can be processed using single screw extrusion processes without the need to modify the standard equipment. The formation of cross-links in PE-V decreases the degree of crystallinity of the material which leads to a decrease in stiffness. However, PE-V exhibits higher thermal stability, higher dimensional stability above melting temperature, and lower shrinkage compared to PE. The improvement in these properties allows the use of PE-V in material extrusion additive manufacturing (ME-AM) to reduce mechanical anisotropy and improve dimensional accuracy.
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