本研究以離子共沉澱法製備鎂鋁比為2：1之水滑石，經鍛燒後以離子交換法製備以十二、十四及十八烷基硫酸鈉插層之有機改質水滑石(layered double hydroxides, LDHs)。將所得水滑石與thermoplastic polyurethane (TPU)、polyethylene terephthalate (PET)及polyethylene 1,4-cyclohexylenedimethylene terephthalate (PETG)機械混摻製備奈米複合材料。
由於TPU為極性高分子，與長鏈烷基之相容性較差，因此有機插層鏈長越長之水滑石分散越差，使得TPU/LDHs形成插層型複合材料。添加水滑石可將複合材料之機械性質提升，但添加過多水滑石易造成聚集，機械強度亦變差。添加水滑石造成氣體透過速率下降，表示以層狀分散其中之水滑石增長穿透路徑，阻擋氣體透過。然而水滑石隨溫度升高釋出層間結晶水加速TPU第一階段的解聚合，且水滑石插層助劑層間長鏈烷基裂解，造成整體熱穩定性的下降。
無論插層助劑與添加比例為何，PET/LDHs複合材料可形成部分插層/部分剝離型奈米複合材料。當水滑石添加比例達5 wt%時，熱裂解溫度有最高的提升，然添加過多的水滑石可能造成水解的情形產生，使熱穩定性下降。添加水滑石可以幫助高分子結晶，使其成核速率與結晶速率增加，原因在於水滑石的存在在結晶過程中可作一異相成核子，此外，奈米級的水滑石層板均勻分散在複合材料中，可幫助高分子鏈堆疊成結晶型態。由於PET結晶速率過快且過於硬脆，本實驗摻入50 wt%無序之PETG以改善之，可成功製備部分插層/部分剝離型奈米複合材料。在機械性質測試中，最大應力與楊氏係數隨水滑石添加比例增高上升，表示材料硬度的強化。添加越多水滑石，其氣體透過速率越低，可提升阻氣程度。

Nanocomposites composed of the organic-modified layered double hydroxide (LDHs) and thermoplastic polymers, including thermoplastic polyurethane (TPU), polyethylene terephthalate (PET), and polyethylene 1,4-cyclohexylenedimethylene terephthalate (PETG) were prepared by a melt-blending method. We modified LDHs by a series of alkyl sulfates to investigate the effect of the chain length of the surfactants on the properties of the nanocomposites.
Since the TPU chains are polar, the compatibility between TPU and alkyl sulfates is poor. As a result, the dispersion of the long-chain alkyl sulfate-tethered LDHs in TPU was poor, forming intercalated nanocomposites. The addition of LDHs enhanced the mechanical properties of the composites and the tetradecyl sulfate-tethered LDHs showed the best improvement. However, when the amount of the added LDHs was high, the LDHs formed aggregation, which led to the reduction of the mechanical strength. The addition of the LDHs also resulted in a decrease of the gas transmission rate, indicating that the dispersion of LDHs caused an increase in the penetration path of the gas. However, the thermal stability of the nanocomposites decreased as the length of the alkyl group increased. This was caused by the release of the alkyl group and crystalline hydrate during thermal decomposition that increased the decomposition rate of the nanocomposites.
In PET / LDHs nanocomposites, the addition of LDHs developed to the exfoliated nanocomposites. When the amount of the LDHs was 5 wt%, the thermal decomposition temperature increased 18℃.The inclusion of LDHs significantly increased the nucleation rate and crystallization rate of the nanocomposites. This was attributed to the presence of LDHs that acted as heterogeneous nuclei and the nanoscale LDHs layers uniformly dispersed in PET facilitated the polymer chains to be stacked in a crystalline form. In this study, we further added 50 wt% amorphous PETG to reduce the degree of crystallization of PET and increase the processibility of the nanocomposites. In the mechanical measurement, the stiffness of LDHs enhanced the hardness of the nanocomposites. Additionally, the gas barrier increased with the addition of LDHs, indicating that the presence of the layered structure of LDHs provided the tortuous path for gas diffusion and lower the transmission rate.

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