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Title Page

Contents

Abstract 7

Chapter 1. Introduction 9

1.1. Nanocomposites 9

1.2. Halloysite Nanotube (HNT) as an Eco-friendly Material 16

1.3. Effective Dispersion of Nanofillers in Nanocomposites 19

Chapter 2. Experimental Work 23

2.1. Materials and Methods 23

2.1.1. Preparation of UP/HNT Nanocomposites 23

2.1.2. Heat Treatment of HNTs at Different Temperatures 30

2.1.3. HNT Dispersion by Ultrasonic Homogenization 33

2.2. Characterization of UP/HNT Nanocomposites 36

2.2.1. X-ray Diffraction 36

2.2.2. Transmission Electron Microscopy (TEM) 38

2.2.3. Impact Test 39

2.2.4. Tensile Test 41

Chapter 3. Results and Discussion 44

3.1. Observation of Structural Changes by X-ray Diffraction and TEM Imaging 44

3.2. Changes in Mechanical Properties 52

3.2.1. Impact Properties 52

3.2.2. Tensile Properties 57

3.2.3. Considerations on the Effects of Nanoparticle Dispersion on Mechanical Strength 62

Chapter 4. Conclusion 65

Reference 67

List of Tables

Table 2.1. Description of main materials 24

Table 2.2. Conditions of ultrasonic homogenization used 34

List of Figures

Fig. 1.1. Curing reaction of thermoplastic resin 12

Fig. 1.2. Structure of thermosetting resin 13

Fig. 1.3. Classification of composite material according to the component 15

Fig. 1.4. Comparison of nanofiller dispersion method as observed by optical microscope 21

Fig. 2.1. Manufacture of polyester resins based on coal and petroleum 25

Fig. 2.2. Matrix and addition 26

Fig. 2.3. HNTs at room temperature 27

Fig. 2.4. Chemical structure of HNT 27

Fig. 2.5. Sample preparation procedure 28

Fig. 2.6. Schematic diagram of resin infusion and shape preservation 30

Fig. 2.7. Heat treatment machine 31

Fig. 2.8. Process diagram of heat treatment 32

Fig. 2.9. Ultrasonic homogenization machine 33

Fig. 2.10. Process schematic diagram of ultrasonic homogenization 36

Fig. 2.11. Equipment used for impact test and the samples 40

Fig. 2.12. Machine for tensile test 41

Fig. 2.13. Samples for tensile test 42

Fig. 3.1. X-ray observation of HNTs at various heat treatment temperatures 46

Fig. 3.2. TEM of HNTs at various temperatures 51

Fig. 3.3. Comparison of impact strength of neat UP and its nanocomposites... 54

Fig. 3.4. Comparison of impact strength of neat UP and its nanocomposites... 55

Fig. 3.5. Results of tensile test of neat UP and its nanocomposites under 45W... 59

Fig. 3.6. Results of tensile test of neat UP and its nanocomposites under 60W... 61

초록보기

Nanoparticle refers to a particle within the scope of a hundred nanometers and nanoparticles have a wide specific surface area. By controlling their size or using nanoparticles of various types, the properties of material can be improved with only a small amount of particulate filler.

Halloysite is a naturally occurring aluminosilicate in the form of nanotubes, also known as halloysite nanotubes (HNTs). The HNTs are odorless, white particles with the chemical formula H4Al2O9Si2·2H₂O. Halloysite nanotubes are readily obtainable and are much cheaper than other tubular nanoparticles such as carbon nanotubes. There HNTs have been considered as a functionally effective material capable of mechanically strengthening resins by restrictive matrix dislocation movement. Especially, there are studies showing that adding HNTs to plastics improves tensile strength, impact resistance, fire retardancy and gives the added advantage of improved cycling time in production by injection molding.

In this study, samples consisted of nanocomposites manufactured by adding HNTs to unsaturated polyester resin (UP). Herein, the contents of HNTs were 0.5, 1 and 3 wt.%. The purpose was to analyze the mechanical properties of nanocomposites on a function of HNTs content and through this, to find the optimal conditions for developing UP matrix HNT reinforced nanocomposites. The HNTs used in this study were treated by heat. Heat-treated HNTs were divided into 4 groups: untreated HNT (UTHNT), 300℃ (300HTHNT), 500℃ (500HTHNT), 700℃ (700HTHNT) and 1000℃ (1000HTHNT) heat-treated HNT, according to treating temperatures. To achieve a uniform distribution of nanoparticles in the matrix, the factors optimized for dispersion were considered and a suitable process environment for materials to be used was adopted by dividing these factors into constants and variables. The ultrasonic homogenization is used in the production of nano-size materials, dispersions and emulsions, because of the potential in deagglomeration. Ultrasonic homogenization is an easy way to separate particle aggregate, and obtain homogeneous phase. Ultrasonication was carried out by varying some parameters. The operating time and the volume of the sample were maintained at fixed values, namely 300 s and 18 ml, respectively. The output power was divided into two cases, at 45W and 60W.

Finally we established the optimal dispersion condition of HNTs using ultrasonication, and the reinforcement effect of HNTs was studied by X-ray diffraction and evaluation of mechanical properties of nanocomposites such as impact strength and tensile strength. Also, the structural changes of HNT by heat treatment at various temperatures were evaluated.

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