表面改質二氧化矽/聚乳酸奈米複合材料基本鑑定與阻氣性之影響

Characterization of surface modified silica/poly(L-lactic acid) nanocomposites and the effect of barrier properties

黃嘉佑(Chia-Yu Huang)

指導教授 ： 孫一明

元智大學/工程學院/化學工程與材料科學學系/碩士(2012年)

https://doi.org/10.6838/YZU.2012.00175

摘要

本研究利用聚(L-乳酸) (PLLA)與改質之二氧化矽奈米粒子混合後，進行熱性質、結構與阻氣性質的探討。利用左式丙交酯(L-lactide)開環反應，接枝於奈米粒子表面上，從FTIR與TEM的結果證實，二氧化矽表面存在已接枝之PLLA。由TEM與FE-SEM觀察改質二氧化矽與未改質二氧化矽在聚乳酸內的分佈情況。
由DSC結果發現在改質二氧化矽/聚乳酸有明顯的熔融結晶出現，這說明了改質二氧化矽在此奈米複合材中為一良好的成核劑。從WAXD結果發現，各二氧化矽奈米粒子/PLLA複合膜材結晶度並沒有太大的差異，但是ordered domain size (D200)在二氧化矽/聚乳酸與改質二氧化矽/聚乳酸兩系統中卻有不同的結果。從SAXS結果發現聚乳酸的晶板層會隨著奈米二氧化矽的添加而有變厚的趨勢。
以氧氣與水氣的阻氣性可以看到其滲透值會隨著奈米粒子的添加而有下降的趨勢，添加表面改質之二氧化矽的高分子之阻氣性會比加入未改質的二氧化矽之高分子更為良好；阻氣性之間的差異應是由於結晶結構的不同導致的。經過熱處理後兩系統的氧氣與水氣的阻氣性沒有太大的差異，成核效應對於阻氣性沒有太大的差異，這可以由WAXS與SAXS的結果印證；由PALS的結果可以看出高分子的非結晶區沒有太大的差異，奈米粒子主要影響高分子的結構應在結晶區為主。

關鍵字

奈米二氧化矽 ； 聚乳酸 ； 表面改質 ； 阻氣性

並列摘要

The thermal, structure, and gas barrier properties of unmodified and modified silica/poly(L-lactic acid) (SiO2/PLLA and g-SiO2/PLLA) nanocomposites were investigated in this study. Silica nanoparticles were modified with L-lactide via ring-opening polymerization to form grafted PLLA on the surface of SiO2. The grafted PLLA on silica was confirmed by thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The grafting ratio was determined by TGA. The dispersion of nanoparticles and nanocomposites were obtained by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), respectively.
The thermal properties, crystallization behavior, and free volume properties of nanocomposites were investigated using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and small angle x-ray scattering (SAXS), respectively. It was found that the apparent melt-crystallization behavior in cooling and isothermal process indicated that g-SiO2 is a good nucleating agent in the nanocomposites. The crystallinity of all samples was similar, but the ordered domain sizes (D200) was different between SiO2/PLLA and g-SiO2/PLLA. And during melt crystalline process, SAXS result indicated the polymer lamellae become thicker with nano-silica content.
The gas permeation of oxygen and water vapor reveals that the permeability would decrease with the content of nano-silica, and the addition of graft-silica could obtain better gas barrier properties than the pure silica. The better gas barrier properties may due to the difference between graft silica and pure silica affect in polymer structure. After annealing process, the permeability difference between the PLLA composites with g-SiO2 and SiO2 would not significant. The nucleating effect of both nano-silica won’t affect the gas barrier remarkable, as same result in polymer lamellae structure in later mention by WAXD and SAXS. In PALS results, the polymer amorphous region would not change apparently. The barrier properties variation must be ascribed to the nanoparticle presence and not to the free volume changes. The presence of nanoparticle would influence the polymer crystalline structure.

並列關鍵字

nano silica ； poly( L-lactic acid) ； surface modification ； gas barrier properties

參考文獻

1. Cutter, C. N. Opportunities for bio-based packaging technologies to improve the quality and safety of fresh and further processed muscle foods, Meat Sci. 2006, 74, 131-142.

2. Sorrentino, A., Gorrasi, G., and Vittoria, V. Potential perspectives of bio-nanocomposites for food packaging applications, Trends in Food Sci & Technol. 2007, 18, 84-95.

3. Siracusa, V., Rocculi, P., Romani, S., and Rosa, M. D. Biodegradable polymers for food packaging: a review, Trends in Food Sci & Technol. 2008, 19, 634-643.

4. Komatsuka, T., Kusakabe, A., and Nagai, K. Characterization and gas transport properties of poly(lactic acid) blend membranes, Desalination 2008, 234, 212-220.

5. Mascheroni, E., Guillard, V., Nalin, F., Mora, L., and Piergiovanni, L. Diffusivity of propolis compounds in Polylactic acid polymer for the development of anti-microbial packaging films, J. Food Eng. 2010, 98, 294-301.