Mechanically adaptable elastomer composites are a class of stimuli responsive polymer composites which can reversibly change its mechanical properties when it comes in contact with stimuli like electric field, light, water, solvents, ions and others. Mechanically adaptable composites are mainly inspired from the sea cucumber dermis which has the ability to change the stiffness of its dermis rapidly and reversibly (connecting tissue) when it is immersed in water.
In this work, efforts have been made to develop mechano-adaptive elastomer composites using water as stimuli. In such a case, elastomer composite should absorb water significantly, in order to respond quickly to the stimuli. Therefore, as a first step, stable and repeatable water swellable elastomer composites have been developed by blending epichlorohydrin terpolymer (GECO) with an ethylene oxide based hydrophilic polymer resin (GEPO).
Two different approaches have been thereafter explored to develop mechano-adapative composites based on the developed water swellable elastomer composite. In the first approach, the solid–liquid phase transition of the absorbed water is used to tune mechanical properties around 0 °C. The solidified absorbed water (ice crystals) below 0 °C, acts as reinforcing filler, enhancing the mechanical properties (hard state). The ice crystals liquefy above 0 °C and plasticize the polymer chain, thereby reducing the mechanical properties (soft state). In the second approach, the polymorphic transition of calcium sulphate (CaSO4) in presence of water/heat have been exploited by dispersing it as filler in the developed water swellable elastomer composite. Mechanical adaptability is realized by the reinforcement caused when the composite is exposed to water treatment process. Further, this mechanical strength (reinforcement) can be brought back to its initial soft state (unreinforced state) by the heat treatment process. This reversible reinforcing and non-reinforcing ability of the calcium sulphate filler is attributed to the differences in polymer–filler interaction, due to the in situ morphology transformation (micro to nano) of the filler particles.
This study reveals the possibility of utilizing conventional rubber technology in developing mechanically adaptable composites with an easily accessible stimulus like water. The two strategies explored here present huge opportunities in developing future smart materials.:Contents
1 Introduction 1
1.1 General introduction 1
1.2 Aim and motivation of the work 3
1.3 Scope of the work 5
2 Literature review 7
2.1 Mechanically adaptive polymer composites 7
2.1.1 Mechanical adaptability triggered by different stimuli 7
2.1.2 Water induced mechano-adaptive composites 10
2.1.3 Possible future applications of mechanically adaptive systems 14
2.2 Water absorption in elastomer composites 16
2.2.1 Strategies used for developing water swellable elastomer composites 17
2.2.2 States of water present in the polymers 20
2.2.3 Effect of water absorption on the thermal and mechanical properties 22
2.2.4 Kinetics of diffusion of water in the hydrophilic polymers 24
2.2.5 Application of water swellable elastomer composites 25
2.3 Calcium sulphate and its polymorphic transition 26
3 Experimental 30
3.1 Materials 30
3.1.1 Polymers 30
3.1.2 Fillers 31
3.2 Preparation of rubber composites 32
3.2.1 Compounding and mixing 32
3.2.2 Curing study and molding 34
3.3 Characterization 35
3.3.1 Water swelling studies 35
3.3.2 Thermal analysis (DSC and TGA) 36
3.3.3 Dynamic mechanical analysis (DMA) 36
3.3.4 Stress–strain studies 37
3.3.5 Fourier transform infrared spectroscopy (FTIR) 38
3.3.6 Morphological analysis 39
3.3.7 X-ray diffraction (XRD) 40
3.3.8 Raman spectroscopy 40
4 Results and discussions 42
4.1 Development of novel water swellable elastomer composites based on GECO/GEPO 42
4.1.1 Miscibility of the polymer blend (GECO/GEPO) systems 42
4.1.2 Water absorption behavior of GECO/GEPO blends 49
4.1.3 Effect of water swelling on thermal and mechanical properties 54
4.1.4 Cyclic water swellable characteristics 58
4.2 Thermo-responsive mechano-adaptable composites based on solid–liquid phase transition of absorbed water. 60
4.2.1 Quantitative analysis of in situ formed ice crystals 61
4.2.2 Characterization of the filler (ice crystals) morphology 64
4.2.3 Polymer–filler interaction 68
4.2.4 Mechanical adaptability analysis 71
4.3 Utilization of in situ polymorphic alteration of the filler structure in designing mechanically adaptive elastomer composites 77
4.3.1 Process and conditions for mechanical adaptability 79
4.3.2 Investigation of phase transition characteristics of CaSO4 filler 83
4.3.3 In situ morphology transformation analysis 86
4.3.4 Mechanical adaptability investigations 89
5 Conclusions and outlook 96
5.1 Conclusions 96
5.2 Outlooks 99
6 References 100
7 Appendix 109
8 Abbreviations 111
9 Symbols 114
10 Figures 117
11 Tables 123
12 Publications 124 / Mechanisch-adaptive Elastomer-Verbundwerkstoffe sind eine Klasse von stimuli-responsiven Polymer-Verbundwerkstoffen, welche ihre mechanischen Eigenschaften reversibel verändern können, wenn sie mit Stimuli, wie z.B. einem elektrischem Feld, Licht, Wasser, Lösungsmitteln oder Ionen angeregt werden. Mechanisch anpassbare Verbundwerkstoffe sind hauptsächlich von der Haut der Seegurke inspiriert, welche in der Lage ist, die Steifigkeit ihrer Dermis (Bindegewebe) beim Eintauchen in Wasser schnell und reversibel zu verändern.
Ziel dieser Arbeit war, mechanisch-adaptive Elastomer-Verbundwerkstoffe zu entwickeln, welche Wasser als Stimulus nutzen. Für diese Anwendung sollte das Elastomermaterial Wasser in einer signifikanten Menge aufnehmen können, um schnell auf den externen Reiz zu reagieren. Daher wurden in einem ersten Schritt stabile und reversibel wasserquellbare Elastomerblends hergestellt, indem ein Epichlorhydrin-Terpolymer (GECO) mit einem hydrophilen Polymerharz auf Ethylenoxidbasis (GEPO) verschnitten wurde.
In der Folge wurden zwei verschiedene Ansätze zur Entwicklung mechanisch-adaptiver Verbundwerkstoffe auf Basis des so entwickelten wasserquellbaren Elastomerkomposites verfolgt. Beim ersten Ansatz wird der Fest-Flüssig-Phasenübergang des aufgenommenen Wassers genutzt, um die mechanischen Eigenschaften im‚ Bereich von 0 °C einzustellen. Das erstarrte absorbierte Wasser (Eiskristalle) wirkt unter 0 °C als verstärkender Füllstoff und verbessert die mechanischen Eigenschaften (harter Zustand). Die Eiskristalle verflüssigen sich oberhalb von 0 °C und plastifizieren das Polymer, wodurch die mechanische Verstärkung wieder herabgesetzt wird (weicher Zustand). Im zweiten Ansatz wurde der polymorphe Übergang von Calciumsulfat (CaSO4) in Gegenwart von Wasser bzw. Wärme genutzt, indem es als Füllstoff in einem wasserquellbaren Elastomerkomposit dispergiert wurde. Die mechanische Adaptierbarkeit wird durch die mechanische Verstärkung erreicht, welche bei der Wasseraufnahme des Verbundwerkstoffes entsteht. Anschließend kann diese mechanische Festigkeit (Verstärkung) durch eine Wärmebehandlung wieder in ihren ursprünglichen weichen Zustand (unverstärkter Zustand) zurückgeführt werden. Diese reversible Schaltbarkeit der Verstärkungswirkung des Calciumsulfat-Füllstoffes wird auf die Unterschiede in der Polymer-Füllstoff-Wechselwirkung aufgrund der Transformation der in situ-Morphologie (Mikro zu Nano) der Füllstoffpartikel zurückgeführt.
Die vorliegende Arbeit verdeutlicht die Möglichkeiten des Einsatzes konventioneller Kautschuktechnologie bei der Entwicklung mechanisch anpassbarer Komposite mit einem
leicht zugänglichen Stimulus wie Wasser. Die beiden hier untersuchten Strategien eröffnen enorme Perspektiven bei der Konzeption zukünftiger intelligenter Materialien.:Contents
1 Introduction 1
1.1 General introduction 1
1.2 Aim and motivation of the work 3
1.3 Scope of the work 5
2 Literature review 7
2.1 Mechanically adaptive polymer composites 7
2.1.1 Mechanical adaptability triggered by different stimuli 7
2.1.2 Water induced mechano-adaptive composites 10
2.1.3 Possible future applications of mechanically adaptive systems 14
2.2 Water absorption in elastomer composites 16
2.2.1 Strategies used for developing water swellable elastomer composites 17
2.2.2 States of water present in the polymers 20
2.2.3 Effect of water absorption on the thermal and mechanical properties 22
2.2.4 Kinetics of diffusion of water in the hydrophilic polymers 24
2.2.5 Application of water swellable elastomer composites 25
2.3 Calcium sulphate and its polymorphic transition 26
3 Experimental 30
3.1 Materials 30
3.1.1 Polymers 30
3.1.2 Fillers 31
3.2 Preparation of rubber composites 32
3.2.1 Compounding and mixing 32
3.2.2 Curing study and molding 34
3.3 Characterization 35
3.3.1 Water swelling studies 35
3.3.2 Thermal analysis (DSC and TGA) 36
3.3.3 Dynamic mechanical analysis (DMA) 36
3.3.4 Stress–strain studies 37
3.3.5 Fourier transform infrared spectroscopy (FTIR) 38
3.3.6 Morphological analysis 39
3.3.7 X-ray diffraction (XRD) 40
3.3.8 Raman spectroscopy 40
4 Results and discussions 42
4.1 Development of novel water swellable elastomer composites based on GECO/GEPO 42
4.1.1 Miscibility of the polymer blend (GECO/GEPO) systems 42
4.1.2 Water absorption behavior of GECO/GEPO blends 49
4.1.3 Effect of water swelling on thermal and mechanical properties 54
4.1.4 Cyclic water swellable characteristics 58
4.2 Thermo-responsive mechano-adaptable composites based on solid–liquid phase transition of absorbed water. 60
4.2.1 Quantitative analysis of in situ formed ice crystals 61
4.2.2 Characterization of the filler (ice crystals) morphology 64
4.2.3 Polymer–filler interaction 68
4.2.4 Mechanical adaptability analysis 71
4.3 Utilization of in situ polymorphic alteration of the filler structure in designing mechanically adaptive elastomer composites 77
4.3.1 Process and conditions for mechanical adaptability 79
4.3.2 Investigation of phase transition characteristics of CaSO4 filler 83
4.3.3 In situ morphology transformation analysis 86
4.3.4 Mechanical adaptability investigations 89
5 Conclusions and outlook 96
5.1 Conclusions 96
5.2 Outlooks 99
6 References 100
7 Appendix 109
8 Abbreviations 111
9 Symbols 114
10 Figures 117
11 Tables 123
12 Publications 124
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:33707 |
| Date | 03 April 2019 |
| Creators | Natarajan, Tamil Selvan |
| Contributors | Heinrich, Gert, Reincke, Katrin, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/acceptedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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