Jarrousse, Gauthier (2004) Self adhesion of semi-crystalline polymers between their glass transition temperature and their melting temperature. PhD thesis Chimie Physique, ESPCI.

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Abstract

We studied the self adhesion of semicrystalline polymers with variable degrees of crystallinity by performing fracture studies of interfaces formed between their glass transition temperature, Tg, and their melting temperature, Tm, in order to elucidate the role of crystallinity. We used a series of copolymers of polybutylene(terephthalate-co-isophthalate). For pre-crystallized samples, when the temperature of contact (Tcontact) was decreased below Tm, the fracture toughness, Gc decreased with Tcontact to vanish at a temperature corresponding to the onset of the fusion process. For quenched samples obtained in the amorphous state and put in contact before rising the temperature to Tcontact, Gc was very low for temperatures of contact well above Tg. The very thin crystalline layer observed in TEM was held responsible of this weak adhesion. The essential role played by surfaces and interfaces in nucleating crystallinity was shown to be an important factor affecting self-adhesion below Tm.

Table of content

Introduction
Chapter 1: Basic concepts and state of the art
1.1 Basic concepts
1.1.1 Brief introduction to polymers
1.1.1.1 Introduction
1.1.1.2 Types of polymers and classification
1.1.1.3 A few words on polymerization
1.1.1.4 Basic considerations of polymer physics
1.1.1.4.1 A single chain
1.1.1.4.2 Dense system of chains
1.1.1.4.3 The amorphous state
1.1.1.4.4 Mechanical properties of amorphous polymers
1.1.2 Semi-crystalline polymers
1.1.2.1 General structure of semi-crystalline polymers
1.1.2.2 Theories of crystallization kinetics
1.1.2.2.1 General considerations
1.1.2.2.2 Overall crystallization kinetics
1.1.2.2.3 Molecular mechanisms of crystallization
1.1.2.3 Melting
1.1.2.4 General mechanical behavior of semi-crystalline polymers
1.2 Fracture behavior of polymers
1.2.1 Introduction
1.2.2 Energy balance approach
1.2.3 The stress intensity factor approach
1.2.3.1 Plane strain, plane stress and different modes of fractures
1.2.3.2 Basic principles of the stress intensity factor approach
1.2.4 Relationship between G and K
1.2.5 Experimental considerations
1.3 Adhesion between polymers
1.3.1 Introduction
1.3.2 Different fracture mechanisms
1.3.2.1 Chain pullout
1.3.2.2 Chain scission
1.3.2.3 Crazing
1.3.2.4 Transition between the different mechanisms
1.3.3 Interdiffusion at polymer interfaces
1.3.3.1 Polymer interdiffusion
1.3.3.1.1 Diffusion at different time scales
1.3.3.1.2 Interdiffusion at polymeric interfaces
1.3.3.1.3 Fracture toughness and interdiffusion: early studies
1.3.4 Polymer adhesion between amorphous polymers: the modern view
1.3.4.1 Introduction
1.3.4.2 Direct adhesion between amorphous polymers
1.3.4.3 Reinforcement of interfaces (immiscible amorphous polymers)
1.3.5 Adhesion between semicrystalline polymers
1.3.5.1 Reinforcement of incompatible semicrystalline polymers
1.3.5.1.1 Compatibilization by formation of a copolymer
1.3.5.1.2 Compatibilizing less immiscible semicrystalline polymers
1.3.5.2 Self-adhesion of semicrystalline polymers
1.4 Conclusions and objectives of the current study
Chapter 2: Characterizations and experimental techniques
2.1 Brief review: structure and properties of PBT, PBI and PBT/PBI copolymers
2.1.1 PBT
2.1.1.1 Introduction
2.1.1.2 Crystallinity
2.1.1.3 WAXS study on PBT
2.1.1.4 The amorphous phase of PBT
2.1.1.5 Spherulitic structure
2.1.1.5.1 Lamellae
2.1.1.5.2 Spherulites
2.1.1.6 Crystallization and fusion
2.1.1.6.1 Crystallization
2.1.1.6.2 Cold crystallization
2.1.1.6.3 Fusion
2.1.1.6.4 Equilibrium melting temperature and heat of fusion
2.1.1.7 Some mechanical properties of PBT
2.1.2 PBI
2.1.3 PBT-PBI copolymers
2.2 Synthesis and molecular characterizations
2.2.1 Synthesis
2.2.2 End group analysis: determination of Mn
2.2.3 Rheology
2.2.4 NMR experiments
2.3 Bulk characterization
2.3.1 Temperature modulated Differential Scanning Calorimetry
2.3.1.1 Basic theory
2.3.1.2 Experimental procedure
2.3.2 Dynamic Mechanical Analysis
2.3.2.1 Experimental procedure
2.3.2.2 Results
2.3.3 X-rays
2.3.3.1 Sample preparation and results
2.3.3.2 Calculation of the degree of crystallinity
2.4 Adhesion: sample preparation and testing
2.4.1 Molding and assembling
2.4.1.1 Temperature controlled press
2.4.1.2 Molding
2.4.1.3 Cooling procedure
2.4.1.4 Assembling
2.4.2 Measurement of the fracture toughness
2.4.2.1 DCB tests
2.4.2.2 Measurements of the Young's modulus
2.5 Tensile tests
2.5.1 Sample preparation
2.5.2 Tensile test
2.6 Study of the crystallinity at the interface
2.6.1 General procedure for optical and electron microscope observations
2.6.2 Optical observations
2.6.2.1 microtoming the sample
2.6.2.2 observation in polarized light microscopy
2.6.3 Observation in transmission electron microscopy
2.6.3.1 Sample preparation for TEM
2.6.3.2 transmission electron microscope observations
Chapter 3: Results
3.1 PBT and 15PB
3.1.1 Adhesion measurements
3.1.2 DSC results
3.1.3 Microstructure
3.1.3.1 Optical observations
3.1.3.2 TEM observations
3.1.4 Simultaneous analysis of the different techniques
3.1.5 Partial conclusions
3.2 35PB and 45PB
3.2.1 Adhesion results
3.2.2 DSC results
3.2.3 Discussion
3.2.4 Conclusions
3.3 Amorphous 45PB: 45PBa
3.3.1 Characterization of the crystallinity of 45PBa by DSC
3.3.2 Crystallization kinetics
3.3.3 Observations of the samples
3.3.4 Tensile tests
3.3.5 Crystallinity and mechanical behavior
3.3.6 Adhesion results
3.3.7 Crack tip observations (optical and TEM)
3.3.8 Conclusions
3.4 PBI
3.4.1 Characterization of the crystallinity of PBI by DSC
3.4.2 Crystallization kinetics
3.4.3 Samples observations
3.4.4 tensile tests
3.4.5 Crystallinity and mechanical behavior
3.4.6 Adhesion results
3.4.7 Crack tip observation and TEM
3.4.8 Conclusion
Chapter 4: Discussion
4.1 First set :contact between pre-crystallized samples
4.1.1 Overview of the results
4.1.2 Discussion on the mechanisms
4.1.3 Conclusions
4.2 Second set: quenched samples of 45PB and PBI
4.2.1 Overview of the results
4.2.2 Discussion on the mechanisms
4.2.3 Conclusions
4.3 Outlook and ideas for future studies
Conclusion
References
Extended abstract in French

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