Poly L-lactic acid (PLLA) and Poly Methyl Methacrylate

115 Pages·2013·2.16 MB·English

Poly L-lactic acid (PLLA) and Poly Methyl Methacrylate
(PMMA) Blends and Their Interaction with C 02 at Sub-
Critical Conditions
By
Baisheng Yao
A thesis submitted to the
Faculty of Graduate Studies and Research
in partial fulfillment of the requirement
for the degree of
Master of Science
Carleton University
Department of Chemistry
1125 Colonel By Drive
Ottawa, Ontario, Canada
June, 2007
© Copyright
Baisheng Yao, 20007
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Abstract
This work demonstrated the possibility of processing blends of poly L-lactic acid
(PLLA) and poly methyl methacrylate (PMMA) with CO through studying changes in
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the glass transition temperature, solubility, diffusivity and finally generated foam
morphologies.
One glass transition temperature, Heat-induced crystallization and C02-induced
crystallization were observed in the samples. However, the addition of PMMA to PLLA
reduced the rate of PLLA crystallization and increased the decomposition temperature.
The solubility capacity for the blends was investigated. Analysis of the diffusion
coefficients indicated them to be concentration dependent and therefore the possibility of
existence of retrograde behavior in the blend-CC system. The foam morphologies were
>2
strongly related to blend composition, foaming temperature, CO saturation conditions as
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well as the CO induced crystallization and retrograde behavior in the system.
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A mathematical model was also implemented to predict CO solubility, blend
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swelling factors and glass transition behaviors in blend-CC system.
>2
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Acknowledgements
I am very glad to have had the opportunity to do my research and conduct my
experimental work at the National Research Canada under the supervision of Dr. Victoria
Nawaby. I thank her for her support, encouragement and sound advice. Her valuable
questions, comments and suggestions eventually enabled me to grasp rich complexity and
increased the value of this research greatly.
I would also like to express my most sincere thanks to Dr. Bob Burk and Dr. Liao
Xia, Steve Liu, David Kinston, Gill Roberson and Dr. Pam Whitfield for their kind
assistance in my research.
I wish to thank my entire extended families for providing a loving environment,
understanding and support during the two years. My wife Chunqi Ma, my son Martin
Yao, my mother-in-law Guilan Li and my father-in-law Shangzhi Ma were particularly
supportive.
Finally I thank Carleton University for a Graduate Scholarship which gave me
two years of financial support.
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Table of Contents
Abstract.....................................................................................................................................ii
Acknowledgements...............................................................................................................iii
Table of Contents...................................................................................................................iv
List of Tables........................................................................................................................viii
List of Figures.........................................................................................................................ix
Chapter 1: Introduction........................................................................................................1
1.1 Biopolymers.................................................................................................................1
1.2 Poly l-Lactic Acid (PLLA) and Poly Methyl Methacrylate (PMMA)...................2
1.2.1 Structure, Synthesis and Properties of PLLA...............................................3
1.2.2 Structure, Synthesis and Properties of PMMA............................................5
1.2.3 Approved Applications of PLLA and PMMA by U. S. Food and Drug
Administration (FDA)......................................................................................7
1.3 Polymer Properties Modification...............................................................................7
1.3.1 Polymer Physical Properties............................................................................8
1.3.2 Compounding Versus Blending.......................................................................9
1.4 Polymer Foams..........................................................................................................10
1.4.1 Foaming: Theoretical Aspects.......................................................................11
1.4.2 Foaming Techniques......................................................................................12
1.4.3 Cellular Morphologies...................................................................................14
1.5 Supercritical CO in Polymer Processing................................................................15
2
1.5.1 Mathematical Models for Prediction of Gas Solubility, Gas Diffusion and
Glass Transition............................................................................................16
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1.5.1.1 Gas Solubility in Polymers...............................................................16
1.5.1.2 Gas Diffusivity in Polymers...........................................................23
1.5.1.3 Glass Transition for Polymer-Gas System....................................25
1.5.2 CO induced crystallization in polymers......................................................26
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1.6 Interaction of CO with PLLA.................................................................................28
2
1.7 Interaction of CO with PMMA...............................................................................29
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1.8 Research Obj ects.......................................................................................................31
References.........................................................................................................................32
Chapter 2: Experimental....................................................................................................38
2.1 Introduction................................................................................................................38
2.2 Sample Preparation...................................................................................................38
2.2.1 Materials..........................................................................................................38
2.2.2 Melting Blending............................................................................................38
2.2.3 Compression Molding..................................................................................39
2.3 Blend Characterization..............................................................................................39
2.3.1 Differential Scanning Calorimetry (DSC)....................................................39
2.3.2 Thermo gravimetric Analysis (TGA)...........................................................41
2.3.3 X-ray Diffraction (XRD)...............................................................................42
2.4 CO Sorption Kinetic Studies..................................................................................43
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2.5 Foaming Studies.......................................................................................................45
2.51 Materials.........................................................................................................45
2.52 Foam Characterization...................................................................................46
References.........................................................................................................................47
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Chapter 3: Results and Discussions..................................................................................48
3.1 PLLA/PMMA Blend Characterization...................................................................48
3.1.1 DSC Analysis.................................................................................................49
3.1.2 TGA Analysis................................................................................................52
3.2 Absorption Kinetics, Solubility and Diffusion Coefficient...................................54
3.3 CO Induced Crystallization...................................................................................61
2
3.4 Foam Characterization..............................................................................................65
3.4.1 Foam Morphologies......................................................................................73
References.........................................................................................................................78
Chapter 4: Prediction of Gas Solubility, Polymer Swelling and Class Transition
Behaviors in PLLA/PMMA-CO System....................................................80
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4.1 Introduction...............................................................................................................80
4.2 Theory........................................................................................................................81
4.3 Results and Discussion.............................................................................................83
4.3.1 Characteristic Parameters of PLLA/PMMA Blend System and Interaction
Parameters of PLLA/PMMA-CO System.................................................84
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4.3.2 Prediction of CO Equilibrium Solubility in PLLA/PMMA.....................85
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4.3.3 Prediction of Solution Equilibrium Swelling..............................................88
4.3.4 Prediction of glass Transition Behaviors in PLLA/PMMA.......................90
References.........................................................................................................................93
Chapter 5: Conclusions and Recommendations.............................................................95
5.1 Conclusions................................................................................................................95
5.2 Recommendations....................................................................................................96
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Appendix A 98
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List of Tables
Table 3.1: Thermal transition of the neat and polymer blend samples...............................50
Table 3.2: Thermal transition for PLLA/PMMA 50/50wt% samples after annealing 52
Table 3.3: Henry’s Law Constant for CO in neat and polymer blends............................58
2
Table 3.4: Foam average cell size as a function of foaming temperature, saturation
conditions of 25°C and 5.5MPa..........................................................................72
Table 3.5: Foam average cell size as a function of foaming temperature, saturation
conditions of 0°C and 3.4MPa............................................................................72
Table 4.1: Characteristic parameters and interaction parameters at 25°C..........................84
Table 4.2: Flex energy of blends and neat polymers..........................................................90
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List of Figures
Figure 1.1: synthesis routes of PLA.........................................................................................4
Figure 1.2: The basic structure of the stereocomplex of (a) atactic PMMA, (b) isotactic
PMMA, (c) syndiotactic PMMA..........................................................................6
Figure 1.3: Diffusion coefficient of C02 in PMMA at 25°C............................................30
Figure 1.4: Retrograde vitrification in PMMA-CO system...............................................31
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Figure 2.1: A schematic of the gas handling and control system.......................................44
Figure 3.1: DSC thermograms of neat and polymer blend samples...................................49
Figure 3.2: DSC thermograms PLLA/PMMA 50/50 wt %, annealed at 90°C..................51
Figure 3.3: TGA thermograms of neat and polymer blend samples in air.........................53
Figure 3.4: Weight lost rates of the neat and polymer blends in air...................................53
Figure 3.5: Sorption kinetics of CO in 50/50 wt% PLLA/PMMA blend: (a) 25°C and (b)
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0°C........................................................................................................................55
Figure 3.6: Equilibrium solubility of CO in blends; (a) 25°C and (b) 0°C in 50/50 and
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75/25 wt% blend samples...................................................................................57
Figure 3.7: Diffusion coefficient of CO in neat and polymer blend samples at: (a) 25°C
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and (b) 0°C............................................................................................................59
Figure 3.8: X-ray diffraction patterns for PLLA/PMMA (50/50 wt%) after exposure to
CO as a function of pressures at 25°C..............................................................62
2
Figure 3.9: X-ray diffraction patterns for the blends as a function of saturation conditions:
(a) 5.5MPa C02 at 25°C and (b) 3.4MPa CO at 0°C.......................................63
2
Figure 3.10: Crystallinities of blends after exposed to CO at 25°C..................................64
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