Plasticized Poly (lactic acid) Films - Preparation and Properties
(2003)- Abstract
- The development of biodegradable polymers from renewable resources is of importance in order to prevent the depletion of fossil fuels and the increasing emissions of carbon dioxide to the atmosphere caused by the commodity plastics of today. However, to be able to replace these non-environmentally friendly materials, production costs of biodegradable polymers have to be decreased and their physical properties need to be enhanced.
This research has been devoted to poly (lactic acid), PLA; a biodegradable, semicrystalline thermoplastic that can be produced from renewable resources. The main focus was to overcome the inherent problem of brittleness in PLA in order to enable it for potential use in the packaging material... (More) - The development of biodegradable polymers from renewable resources is of importance in order to prevent the depletion of fossil fuels and the increasing emissions of carbon dioxide to the atmosphere caused by the commodity plastics of today. However, to be able to replace these non-environmentally friendly materials, production costs of biodegradable polymers have to be decreased and their physical properties need to be enhanced.
This research has been devoted to poly (lactic acid), PLA; a biodegradable, semicrystalline thermoplastic that can be produced from renewable resources. The main focus was to overcome the inherent problem of brittleness in PLA in order to enable it for potential use in the packaging material industry. Blending PLA with suitable plasticizers in order to enhance its flexibility has been the explored route and obtaining sufficiently compatible blends in order to prevent phase separation and migration has been an important issue when modifying the physical properties of the polymer.
It was found that the presence of plasticizers in the PLA matrix contributed to a more complete crystallization of the polymer because of the increased chain mobility as a consequence of the depressed glass transition temperature, Tg. The more efficient the plasticizer, the larger the decrement in Tg and, thus, the faster the aging process leading to phase separation and migration of the plasticizer. It is clear that there exists a competition between the efficiency of the plasticizer and the speed of the aging/cold crystallization in the material and it is imperative to find an optimum where the Tg is as low as possible without the plasticized material cold crystallizing too fast.
Low molecular weight plasticizers, such as tributyl citrate, TbC, and diethyl bishydroxymethyl malonate, DBM, drastically decreased the Tg of PLA and the extent of the decrement was larger with an increasing amount of plasticizer. However, the blends were not stable over time since rapid cold crystallization caused a size reduction of the amorphous domains in PLA. Consequently, the ability of PLA to accommodate the plasticizer diminished with the increase in crystallinity and migration of the plasticizer occurred.
Increasing the molecular weight of the plasticizers by synthesizing oligoesters and olidoesteramides resulted in blends that displayed Tg depressions slightly smaller than with the low molecular weight plasticizers. The compatibility with PLA was dependent on the molecular weight of the oligomer and on the presence or not of polar amide groups that were able to positively interact with the PLA chains. Simulating current storage conditions in the packaging industry by aging the materials at ambient temperature revealed that cold crystallization did not take place in the films since the temperature was kept below the Tg:s of the blends. Thereby the enhanced flexibility in the plasticized films could be maintained. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/466310
- author
- Ljungberg, Nadia LU
- supervisor
- opponent
-
- Prof. Albertsson, Ann-Christine, Dept of Polymer Technology, The Royal Institute of Technology, Stockholm
- organization
- publishing date
- 2003
- type
- Thesis
- publication status
- published
- subject
- keywords
- phase separation, aging, thermal properties, dynamic mechanical properties, processing, film preparation, oligomer synthesis, poly (lactic acid), plasticizers, migration, cold crystallization, Polymer technology, biopolymers, Polymerteknik
- pages
- 154 pages
- publisher
- Department of Polymer Science & Engineering, Lund University
- defense location
- Center for Chemistry and Chemical Engineering, Lecture Hall B, Lund Institute of Technology.
- defense date
- 2003-10-29 10:15:00
- ISBN
- 91-7422-034-9
- language
- English
- LU publication?
- yes
- additional info
- Article: "The Effects of Plasticizers on the Dynamic Mechanical and Thermal Properties of Poly (lactic acid)"Nadia Ljungberg and Bengt WesslénJournal of Applied Polymer Science, 86, 1227-1234 (2002) Article: "Film Extrusion and Film Weldability of Poly (lactic Acid) Plasticized with Triacetine and Tributyl Citrate"Nadia Ljungberg, Thorbjörn Andersson and Bengt WesslénJournal of Applied Polymer Science, 88, 3239-3247 (2003) Article: "Tributyl Citrate Oligomers as Plasticizers for Poly (lactic acid): Thermo-mechanical Film Properties and Aging"Nadia Ljungberg and Bengt WesslénAccepted in Polymer (2003) Article: "Thermo-mechanical Film Properties and Aging of Blends of Poly (lactic acid) and Malonate Oligomers"Nadia Ljungberg and Bengt WesslénSubmitted to Polymer (2003) Article: "Plasticization of Poly (lactic acid) with Oligomeric Malonate Esteramides: Dynamic Mechanical and Thermal Film Properties"Nadia Ljungberg, Didier Colombini and Bengt WesslénSubmitted to Journal of Applied Polymer Science (2003) The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Polymer and Materials Chemistry (LTH) (011001041)
- id
- 4b458a24-d4d6-43d6-adbc-fc9f1e8c1287 (old id 466310)
- date added to LUP
- 2016-04-04 10:38:05
- date last changed
- 2018-11-21 20:59:54
@phdthesis{4b458a24-d4d6-43d6-adbc-fc9f1e8c1287,
abstract = {{The development of biodegradable polymers from renewable resources is of importance in order to prevent the depletion of fossil fuels and the increasing emissions of carbon dioxide to the atmosphere caused by the commodity plastics of today. However, to be able to replace these non-environmentally friendly materials, production costs of biodegradable polymers have to be decreased and their physical properties need to be enhanced.<br/><br>
<br/><br>
This research has been devoted to poly (lactic acid), PLA; a biodegradable, semicrystalline thermoplastic that can be produced from renewable resources. The main focus was to overcome the inherent problem of brittleness in PLA in order to enable it for potential use in the packaging material industry. Blending PLA with suitable plasticizers in order to enhance its flexibility has been the explored route and obtaining sufficiently compatible blends in order to prevent phase separation and migration has been an important issue when modifying the physical properties of the polymer.<br/><br>
<br/><br>
It was found that the presence of plasticizers in the PLA matrix contributed to a more complete crystallization of the polymer because of the increased chain mobility as a consequence of the depressed glass transition temperature, Tg. The more efficient the plasticizer, the larger the decrement in Tg and, thus, the faster the aging process leading to phase separation and migration of the plasticizer. It is clear that there exists a competition between the efficiency of the plasticizer and the speed of the aging/cold crystallization in the material and it is imperative to find an optimum where the Tg is as low as possible without the plasticized material cold crystallizing too fast.<br/><br>
<br/><br>
Low molecular weight plasticizers, such as tributyl citrate, TbC, and diethyl bishydroxymethyl malonate, DBM, drastically decreased the Tg of PLA and the extent of the decrement was larger with an increasing amount of plasticizer. However, the blends were not stable over time since rapid cold crystallization caused a size reduction of the amorphous domains in PLA. Consequently, the ability of PLA to accommodate the plasticizer diminished with the increase in crystallinity and migration of the plasticizer occurred.<br/><br>
<br/><br>
Increasing the molecular weight of the plasticizers by synthesizing oligoesters and olidoesteramides resulted in blends that displayed Tg depressions slightly smaller than with the low molecular weight plasticizers. The compatibility with PLA was dependent on the molecular weight of the oligomer and on the presence or not of polar amide groups that were able to positively interact with the PLA chains. Simulating current storage conditions in the packaging industry by aging the materials at ambient temperature revealed that cold crystallization did not take place in the films since the temperature was kept below the Tg:s of the blends. Thereby the enhanced flexibility in the plasticized films could be maintained.}},
author = {{Ljungberg, Nadia}},
isbn = {{91-7422-034-9}},
keywords = {{phase separation; aging; thermal properties; dynamic mechanical properties; processing; film preparation; oligomer synthesis; poly (lactic acid); plasticizers; migration; cold crystallization; Polymer technology; biopolymers; Polymerteknik}},
language = {{eng}},
publisher = {{Department of Polymer Science & Engineering, Lund University}},
school = {{Lund University}},
title = {{Plasticized Poly (lactic acid) Films - Preparation and Properties}},
year = {{2003}},
}