Shape Memory Polymers and Textiles by Jinlian HU

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Shape Memory Polymers and Textiles
by Jinlian HU
Shape Memory Polymers and Textiles

Contents
Preface ix
Acknowledgements xiii
1 Introduction 1
1.1 Concepts associated with shape memory materials 1
1.2 Principle of temperature-dependent shape memory polymers 12
1.3 Applications of shape memory polymers 15
1.4 Prospects for shape memory polymers 23
1.5 References 25
2 Preparation of shape memory polymers 28
2.1 Structures of shape memory polymers 28
2.2 Synthesis of shape memory polymers 39
2.3 Preparation of shape memory polymers for medical uses 53
2.4 References 59
3 Characterization techniques for shape memory polymers 62
3.1 Differential scanning calorimetry 62
3.2 Wide angle X-ray diffraction 69
3.3 Dynamic mechanical thermal analysis 77
3.4 Fourier transform infrared 84
3.5 Raman spectroscopy 87
3.6 Gel permeation chromatography 93
3.7 Polarizing microscopy 93
3.8 Transmission electron microscopy 99
3.9 Scanning electron microscopy 104
3.10 Positron annihilation lifetime spectroscopy 104
3.11 Vapor transport property 107
3.12 References 109
4 Structure and properties of shape memory polyurethane ionomer 113
4.1 Morphology of crystalline soft segment in shape memory polyurethane ionomer 114
4.2 Thermal properties of shape memory polyurethane ionomer 117
4.3 Isothermal crystallization kinetics of the soft segment in shape memory polyurethane ionomer 123
4.4 Analysis of crystallization activation energy of soft segment crystallization in shape memory polyurethane ionomer 128
4.5 Effect of ionic groups on equilibrium melting temperature 132
4.6 Dynamic mechanical property of shape memory polyurethane ionomer 136
4.7 Infrared absorption analysis 140
4.8 Shape memory effect of shape memory polyurethane ionomer 145
4.9 References 157
5 Water vapor permeability of shape memory polyurethane 160
5.1 Factors affecting water vapor permeability of SMPU 160
5.2 Factors affecting equilibrium sorption and dynamic sorption of SMPU 173
5.3 Dependence of WVP through SMPU membranes on temperature 179
5.4 Dependence of free volume of SMPU on temperature 189
5.5 References 195
6 Characterization of shape memory properties in polymers 197
6.1 Parameters for characterization 197
6.2 Measurements of parameters 201
6.3 Effect of thermomechanical cyclic conditions 208
6.4 Effect of sample preparation 214
6.5 References 216
7 Structure modeling of shape memory polymers 218
7.1 Structural skeleton of SMPs 218
7.2 Structural categorization of SMPs 219
7.3 SMPs and traditional polymers 225
7.4 Considerations for molecular design of SMPs 228
7.5 Relationship between structure and property of SMPUs 228
7.6 Modeling of SMPs 238
7.7 References 249
8 Environmentally sensitive polymer gel and its application in the textiles field 252
8.1 Environmentally sensitive polymer gel 252
8.2 Application of environmentally sensitive polymer gel to textiles 258
8.3 References 277
9 Evaluation of shape memory fabrics 279
9.1 Shape memory and wrinkle-free fabrics 279
9.2 Evaluation methods for shape memory fabrics 280
9.3 Subjective method for characterizing shape memory fabrics 284
9.4 Objective method for characterizing shape memory fabrics 290
9.5 Effect of temperature on shape memory effect 299
9.6 Conclusion 303
9.7 References 303
10 Shape memory textiles 305
10.1 Shape memory fibers 305
10.2 Role of smart materials in textiles 326
10.3 Shape memory material used in smart fabrics 327
10.4 Shape memory garments – active structure for fashion apparel 334
10.5 References 336
Index 339

Preface
Several recent developments in materials science have indicated that there is currently strong worldwide interest in using shape memory polymers in different fields, such as textiles, medical applications and vehicle manufacture. There have been significant developments in shape memory technology over the past few years and a number of achievements have been reported. It is not the scope of the book to cover adequately in one volume all aspects of shape memory polymer chemistry and technology in different fields. A systematic review is given of the use of shape memory polymers and their technology, mainly in textiles. Most of the original data presented here are essentially from the Shape Memory Textile Center in the Institute of Textiles and Clothing at the Hong Kong Polytechnic University. In addition, this book is intended to provide a thorough understanding of the concepts and principles of using shape memory polymers in textiles, in terms of its structure, synthesis, and underlying thermoresponsive behaviour. The book also covers the unique features characterizing the shape memory polymers found by different thermal and optical measurements.

Chapters 1–4 discuss the structure, synthesis, and characterizations of shape memory polymer. Chapters 1 and 2 review the kinds of materials showing the shape memory effect, with focus being on the structure and physical properties of thermally sensitive shape memory polymers. The concept of hard and soft segments leading to phase separation is described. The importance of the architecture of the polymer network is emphasized and shape memory polymers having different reversible phase transition temperature – glass transition and melting temperatures – are distinguished. Some typical shape memory polymers used in textiles are then categorized according to their structures – linear, segmented block, or graft copolymer. After that, the synthesis of temperature-sensitive segmented polyurethane and how it differs from ordinary polyurethane is described. Applications of the polymers in textiles, medicine, and other aspects are given, followed by a description of their prospects based on current research.

Some modern characterization techniques used in the study of shape memory polymers with emphasis on signifying the unique properties possessed by this class of polymer is then reviewed in Chapter 3; differential scanning calorimetry and wide angle X-ray, to investigate the microstructures of the synthesized PU samples; dynamic mechanical analysis to study the thermal properties of the polymer. The vibrational modes probed by Fourier transform infrared spectroscopy and Raman spectroscopy identify the major components and the hard segment’s molecular orientation in the samples. Other techniques such as gel permeation chromatography, polarizing microscopy, and transmission electron microscopy are then introduced. Lastly, the use of positron annihilation lifetime spectroscopy (PALS) to access the free volume of the sample is discussed.

Chapter 4 discusses the structural properties and applications of shape memory ionomers, covering mainly the influence of cationic groups and their content within structure on the shape memory effect. The focus is on the potential design of a novel shape memory polyurethane with a specific tailored shape memory function.

Chapters 5–7 are devoted to the investigation of temperature-sensitive shape memory effect in films, its associated structural property, and its modeling. Being of technological significance in textiles, thin shape memory polyurethane (SMPU) membranes with different water vapor permeabilities at various temperatures are specifically discussed in Chapter 5. Some critical factors, such as the chemical nature of the soft segment, distribution of the hard segment, hydrophilic segmental length, its content, and the amount of carbon nano-tubes, are selected and the ways they affect the water vapor transport properties in SMPU membranes are outlined. The dependence of swelling parameter and water vapor pressure at different temperatures are then stated. Subsequently, PALS is used to measure the free volume of holes at different temperatures in selected shape memory films. Chapter 6 defines the important parameters – shape fixity, shape recovery, recovery stress, and recovery rate – to quantify the shape memory effect in films. The experimental methods to measure these parameters are then followed. The influences of thermomechanical cyclic conditions, such as the deformation temperature, maximum applied strain, deformation rate, fixing condition, fixing temperature, recovery temperature and time, and the thermal history of samples on the overall shape memory effect of the sample, are discussed. The structure– condition property of shape memory polymers is discussed in detail in Chapter 7. Some theoretical models, based on the polymer viscoelastic theory, are used to describe the thermomechanical cyclic response under different environment conditions. Modeling of the shape memory effect by using different models, such as that of Lin, Tobushi, Li, and Abrahamson is reviewed. In general, it is observed that the shape memory behaviors of the samples can be qualitatively explained by the models. However most of the models do not adequately predict the detailed shape memory effects in terms of the stress–strain relationship.

In the final group of chapters an environmentally sensitive polymer gel for use in textiles is introduced. The evaluation methods for the shape memory effect in fabrics are given in-depth treatment. Then, shape memory fibers and their potential use in textiles are discussed. Chapter 8 describes a new type of polymer network which is partly cross-linked – a gel. It is a special gel showing abrupt changes in response to the stimuli of external environment conditions, such as temperature, pH value, solvent, light intensity/wavelength, ionic strength, and magnetic field. The underlying physics leading to the unique properties of a gel is then explained by the swelling theory. The application of using gel in smart fabrics is then covered.

In Chapter 9, the objective and subjective characterizations of shape memory fabrics are developed to quantify the shape memory effect in fabrics. Shape memory angle and coefficient are defined to characterize the shape memory effect in fabrics; in particular, investigation is devoted to the fabrics when they are placed in warm water and air. Lastly, the detailed structure and synthesis of shape memory fibers and their applications in textiles are described in Chapter 10.

The purpose of the book is to cover recent developments in the use of temperature-responsive shape memory polymers in textiles by experts in the field, the associated concepts of the underlying mechanism in shape memory polymers, and their characterization features through different experimental techniques. I feel these goals have been duly met.

Jinlian HU


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