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Poly (Lactic Acid) Modification to Impart Toughening and Enhance Biodegradation: Elucidation of Mechanisms.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Poly (Lactic Acid) Modification to Impart Toughening and Enhance Biodegradation: Elucidation of Mechanisms.
Author:	Greenland, Jordan L.
Published:	Ann Arbor : ProQuest Dissertations & Theses, 2023
Description:	148 p.
Notes:	Source: Dissertations Abstracts International, Volume: 85-02, Section: B.
Notes:	Advisor: Pearson, Raymond.
Contained By:	Dissertations Abstracts International85-02B.
Subject:	Polymer chemistry.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30634126
ISBN:	9798380138185

Poly (Lactic Acid) Modification to Impart Toughening and Enhance Biodegradation: Elucidation of Mechanisms.
Greenland, Jordan L.

Poly (Lactic Acid) Modification to Impart Toughening and Enhance Biodegradation: Elucidation of Mechanisms. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 148 p.

Source: Dissertations Abstracts International, Volume: 85-02, Section: B.

Thesis (Ph.D.)--Lehigh University, 2023.

This item must not be sold to any third party vendors.

Conventionally, two major factors navigate polymer resin and modifier selection: mechanical performance and price. Recently, material sustainability is growing in importance due to a reduction in the total amount of energy used and in the amount of plastics pollution. Industrial reduction, re-use, and recycling of energy is economically compelling, creating space in the market for innovative approaches to achieve material sustainability. At-home composting is becoming a viable option as demand for single-use plastics and consumer 3D-printing continues to bustle. Polylactic acid (PLA) is a high performing bio-based biodegradable polyester resin that has piqued the interest of materials scientists and engineers for its application in these niche markets. However, its uniquely brittle behavior limits its potential applications and requires toughness modification to slow the rate to failure when cracked. This concept is proven to work in the toughness modification of cross-linked epoxy and thermoplastic Polystyrene (PS) resins. Neat PLA resin is typically amorphous and produced through condensation polymerization. PLA resin’s mechanical behavior: stiffness, strength, and toughness, mimic that of PS and Polyamide 6 (PA6), which are two common 3D-printing resins. However, the PLA resins back-bone chemical structure has an affinity to undergo hydrolysis, reversing its polymerization reaction when exposed to heat and moisture. Melt-processing PLA resin modified with soft and biodegradable Multifunctional Particles (MP) yields a 200% higher elongation to break, 10% improvement in toughness, and rate of thermal and environmental degradation enhancement in the resin. Rigid Hemp Fibers (HF) are a secondary bio-sourced modifier added to formulate hybrid PLA resins retaining biodegradability. The use of solution, thermal, and mechanical treatments are performed on HF modifier prior to melt-processing. The treatments are investigated for their effect on the rate of degradation, stiffness, and strength enhancement imparted on PLA resin by the HF modifier. The Young’s Modulus of PLA resin is improved up to 20%. The strength reduction imparted by the MP modifier is mitigated up to 24%. The toughness of PLA resin is synergistically enhanced by hybrid modification 20%. In summary, bio-sourced modifiers improve the toughness, stiffness, strength, and degradation of PLA resin because of synergized hybridization. PLA resin’s propensity to craze and fracture strain energy release rate was accelerated by modification. Hybrid modification of PLA resin induces biodegradation mechanisms that exhibit preferential composting soil environments. Hybrid PLA resins can be applied in melt-processing applications: 3D-printing filament, extrusion, and compression molding to achieve plastics processing material sustainability and reduce plastics pollution of materials used in the plastics industry. The melt-processes employed in this study are proof of concept for further broadening of modified PLA resins melt-processing applications. The biodegradation enhancement imparted by PLA resin modification is a significant finding for solving plastics pollution.

ISBN: 9798380138185Subjects--Topical Terms:

708579
Polymer chemistry.
Subjects--Index Terms:

Polymer engineering

Poly (Lactic Acid) Modification to Impart Toughening and Enhance Biodegradation: Elucidation of Mechanisms.
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506 $a This item must not be sold to any third party vendors.
520 $a Conventionally, two major factors navigate polymer resin and modifier selection: mechanical performance and price. Recently, material sustainability is growing in importance due to a reduction in the total amount of energy used and in the amount of plastics pollution. Industrial reduction, re-use, and recycling of energy is economically compelling, creating space in the market for innovative approaches to achieve material sustainability. At-home composting is becoming a viable option as demand for single-use plastics and consumer 3D-printing continues to bustle. Polylactic acid (PLA) is a high performing bio-based biodegradable polyester resin that has piqued the interest of materials scientists and engineers for its application in these niche markets. However, its uniquely brittle behavior limits its potential applications and requires toughness modification to slow the rate to failure when cracked. This concept is proven to work in the toughness modification of cross-linked epoxy and thermoplastic Polystyrene (PS) resins. Neat PLA resin is typically amorphous and produced through condensation polymerization. PLA resin’s mechanical behavior: stiffness, strength, and toughness, mimic that of PS and Polyamide 6 (PA6), which are two common 3D-printing resins. However, the PLA resins back-bone chemical structure has an affinity to undergo hydrolysis, reversing its polymerization reaction when exposed to heat and moisture. Melt-processing PLA resin modified with soft and biodegradable Multifunctional Particles (MP) yields a 200% higher elongation to break, 10% improvement in toughness, and rate of thermal and environmental degradation enhancement in the resin. Rigid Hemp Fibers (HF) are a secondary bio-sourced modifier added to formulate hybrid PLA resins retaining biodegradability. The use of solution, thermal, and mechanical treatments are performed on HF modifier prior to melt-processing. The treatments are investigated for their effect on the rate of degradation, stiffness, and strength enhancement imparted on PLA resin by the HF modifier. The Young’s Modulus of PLA resin is improved up to 20%. The strength reduction imparted by the MP modifier is mitigated up to 24%. The toughness of PLA resin is synergistically enhanced by hybrid modification 20%. In summary, bio-sourced modifiers improve the toughness, stiffness, strength, and degradation of PLA resin because of synergized hybridization. PLA resin’s propensity to craze and fracture strain energy release rate was accelerated by modification. Hybrid modification of PLA resin induces biodegradation mechanisms that exhibit preferential composting soil environments. Hybrid PLA resins can be applied in melt-processing applications: 3D-printing filament, extrusion, and compression molding to achieve plastics processing material sustainability and reduce plastics pollution of materials used in the plastics industry. The melt-processes employed in this study are proof of concept for further broadening of modified PLA resins melt-processing applications. The biodegradation enhancement imparted by PLA resin modification is a significant finding for solving plastics pollution.
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