熱塑性聚酯彈性體(TPEE)具備橡膠的柔軟性與彈性，以及熱塑性高分子的可塑性和耐熱性，這些優異的特性使此材料得以應用於眾多領域。由於熱塑性彈性體的性質可以藉由硬軟段的比例進行調整，多元的材料特性使它被引入3D列印加工。選擇性雷射燒結(SLS)是3D列印常見的製程之一，欲進行選擇性雷射燒結的材料需要事先磨成粉末才得以進行加工。然而，DSC的實驗數據顯示TPEE在磨成粉末後會出現結晶行為改變的情況，而此結晶速率提升的現象無法藉由熱處理消除。材料的結晶速率提升會對SLS加工造成負面影響。因此，了解TPEE粉末樣品結晶速率提升的機制和成因是重要的課題。
基於本研究之分析結果，我們發現造成粉末樣品的結晶溫率與結晶速率提升的主因是源自材料對於加工狀態的記憶(memory)效應。冷凍研磨的過程中，材料會被施予高強度的剪切作用力，造成TPEE分子鏈形構產生局部有序區域。由於TPEE在熔融態時仍然有微相分離的情況，PBT硬段之間的極性作用力使有序結構即使在高於熔點的溫度也能被保留。因此，在降溫過程中此有序結構會降低盛和自由能障，造成結晶速率提升。偏光顯微鏡觀察顯示，與原始酯粒樣品相比，粉末樣品確實呈現較高的成核密度。本研究證明TPEE的加工狀態會影響其結晶行為，此成果對於3D列印材料之設計有所助益。

Thermoplastic polyester elastomers (TPEEs) has recently attracted much attention for the increasing applications in various fields due to their excellent properties. In particularly, they have been introduced to three dimensional printing (3D printing) technique. The materials applied to the selective laser sintering (SLS) process, one of the 3D printing technique, requires the printing materials to be grinded into powder and the crystallization temperature of the polymer measured by differential scanning calorimetry (DSC) in the cooling process is a key processing parameter. However, DSC results reveal an obvious change in crystallization temperature of the TPEEs consisting of PBT hard segment and PTMEG soft segment after freeze-grinding. The anomalous increase in crystallization temperature may have negative influence on the SLS process; moreover, the changes cannot be eliminated by thermal treatment even at the temperatures much higher than the melting point. In this scenario, the cause for the enhanced crystallization kinetics by freeze-grinding is a significant issue and needs to be further investigated.
On the basis of the experimental results of the present study, the increase in crystallization rate of the powder samples is attributed to the memory of the mechanical processing conditions. That is, the mechanical shear stresses imposed by the freeze-grinding process induces local ordering of the chain conformation of TPEEs, and the local zones of orientation retain in the molten state due to the persistent microphase separation and the polar interactions between the PBT hard segments. Therefore, the persistent aggregates and pre-existing ordered structures accelerate the crystallization kinetics during cooling process. The enhancement of crystallization rate is found to arise from the stress-induced nucleation compared with the virgin pellet samples, they have an increase in overall crystallization rate owing to the enhanced nucleation process. We thus demonstrate that the processing condition has drastic effect on the crystallization behavior of TPEEs, and the underlying mechanism is important for the development of 3D printing crystallite polymers.

Abstract----I
摘要----III
Table of Contents----IV
List of Figures----VI
List of Tables----IX
Chapter 1 Introduction----1
1-1 The Properties of Thermoplastic Polyester Elastomer (TPEE)----1
1-2 The Morphology and Phase Structure of TPEEs----4
1-3 Three-Dimensional Printing (3D Printing) Techniques and Selective Laser Sintering (SLS) Process----8
1-4 Research Motivation and Objective----12
Chapter 2 Experimental Section----13
2-1 Materials----13
2-2 1H Nuclear Magnetic Resonance (1H NMR) Spectroscopy Measurement----13
2-3 Fourier Transform Infrared Spectroscopy (FTIR) Measurement----13
2-4 Differential Scanning Calorimetry (DSC) Measurement----14
2-5 Polarized Optical Microscopy (POM) Observation----14
2-6 Thermal Gravimetric Analysis (TGA)----14
2-7 X-ray Diffraction Measurement----15
2-8 Small Angle and Wide Angle X-ray Scattering (SAXS/WAXS) Measurement----15
Chapter 3 Results and Discussion----16
3-1 Chemical Structures of TPEEs----16
3-2 Particle Characteristic of TPEE Powder Samples----26
3-3 Thermal Stability of TPEEs----30
3-4 Comparison of Melting and Crystallization Behavior of TPEEs in Different Sample Forms----33
3-5 Crystal Structure of TPEEs----44
3-6 Spherulite Morphology and Nucleation Density of TPEEs----47
3-7 Verification of the Effect of Stress on the Crystallization Kinetics of TPEE by Exploiting Various Treatments----53
3-8 The Microphase Separation and the Pre-existing Structure in the Molten State of TPEEs----58
3-9 The Proposed Mechanism of Crystallization in TPEEs----62
Chapter 4 Conclusion----65
References----67

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