高穿透度及低透濕性混掺奈米複合材料： 無溶劑光聚合壓克力/柏買石混成樹酯之研究

High transparency low water vapor permeation polyacrylate/boehmite nanocomposite from solventless photocurable resin system

林函廷(Han-Ting Lin)

指導教授 ： 林唯芳

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.01101

摘要

高分子與無機奈米粒子的複合材料可以達到良好的熱穩定性、低熱膨脹係數、優越的機械性能，以及對水氣及氧氣有好的阻絕能力及高的光穿透度，是一種極具潛力的封裝材料。本研究中我們欲開發可光聚合的奈米複合材料應用在太陽能電池的封裝，並研究奈米粒子的形狀、表面改質劑及對材料做熱處理後對奈米複合材料的性質影響。
我們在壓克力樹酯tricyclodecane dimethanol diacrylate(TCDDA)中混入7wt%以矽烷偶合劑3-trimethoxysilyl propyl methacrylate (MPS)改質的水合氧化鋁片狀奈米粒子(柏買石, 25nm x20nm x2nm)，可以有效的提升材料阻絕水氣的能力，水氣穿透率和純TCDDA高分子相較降低了約44%，且能少許的提升奈米複合材料的硬度9%，但由於片狀的柏買石會散射光線，使得壓克力樹酯未能完全聚合，並造成了熱裂解溫度(Td)較純壓克力樹酯降低約3%且熱膨脹係數升高了24%。我們將奈米複合材料以100oC熱處理24小時，可以進一步改善其熱性質及機械性質，但卻影響了其光學性質：和純壓克力樹酯相比，混入7wt%MPS改質後的柏買石的光穿透度在波長400nm的位置由90%降至70%，試片在熱處理之後產生了黃化的現象。而試片之所以黃化可能是因為起始劑所產生的安息香醛自由基在熱處理之後再結合形成benzil所導致。但我們經由置換表面改質劑為具有氨基的3-aminopropyltrimethoxysilane(APTMS)後可以改善試片黃化的問題，因為其表面的氨基可以抑制benzil的生成，並降低試片黃化造成的吸收提高光穿透度達85% (400nm~900nm)。
我們以含7%重量比的APTMS改質的柏買石添加的壓克力樹酯為基本配方再混入30wt%以MPS改質的二氧化矽奈米粒子(20~25nm)，相較於純壓克力樹酯，可以更有效的提升26%的硬度、降低22%的熱膨脹係數及降低達68%其水氣穿透率。若是以MPS改質的柏買石混入二氧化矽的系統中，硬度因為其改質劑表面的壓克力基可以和壓克力樹酯產生鍵結，使其在硬度方面表現更為優異(28Hv->35Hv)。在穿透式電子顯微鏡可以觀察到7wt%的片狀奈米柏買石在壓克力樹酯中分散的很好，但在添加二氧化矽奈米粒子時，其對柏買石產生了吸附的效果，形成較大卻不緊密的聚集，而隨者二氧化矽奈米粒子的量越來越多其分散在柏買石之外的壓克力樹酯中。
本研究中我們發現片狀的柏買石奈米粒子對阻擋水氣穿透具有極好的效果，而二氧化矽奈米粒子則能有效提升複合材料的機械性質及熱性質。不同的無機粒子表面改質劑因其表面官能基不同，對複合材料表現出的物性及化性也具有極大的影響。

關鍵字

封裝 ； 奈米複合材料 ； 透濕性 ； 吸溼性 ； 壓克力 ； 柏買石

並列摘要

Nanocomposite made from organic matrix and inorganic nanoparticles exhibits good thermal stability, low coefficient of thermal expansion (CTE), eminent mechanical properties, high transparency, excellent water vapor and oxygen barrier properties. They are potential materials for the applications of device encapsulation. In this research, we are developing UV curable nanocomposite for large area flexible solar cell encapsulation. We also investigated the effects of nanoparticle shape, type of the coupling agent and thermal post cure on the properties of nanocomposite.
By incorporating up to 7% by weight of 3-trimethoxysilyl propyl methacrylate (MPS) coupling agent modified platy boehmite nanoparticle (~25nm x20nm x2nm) in poly tricyclodecane dimethanol diacrylate (TCDDA), the moisture permeation of the neat polymer reduces by 44% and the hardness of the nanocomposite slightly increases by 9%. However, the boehmite scatters the light that causes the thermal decomposition temperature (Td) of neat polymer reducing by 3% and the CTE increasing by 24% from incomplete polymerization of organic matrix TCDDA. The thermal post cure at 100oC for 24 hours improves the thermal properties and hardness of the neat polymer but deteriorates its optical property. As compared with the neat polymer, the transmission at 400 nm of nanocomposite is reduced from 90% to 70% (yellowing). The yellowing maybe from the formation of benzil molecule by combining photoinitiated benzaldehyde radical during the thermal postcure process. The extent of yellowing can be reduced (~85% transmission 400nm-900nm) by replacing MPS coupling agent by 3-aminopropyltrimethoxysilane (APTMS), because the amino functionality of APTMS can inhibit the formation of benzil. By blending additional 30% by weight of MPS modified silica nanoparticle (~25 nm) into the 7% boehmite containing TCDDA, the moisture permeation of the neat polymer can be reduced by 68%, CTE reduced by 22% and the hardness increased by 26%. In contrast, the extent of hardness is increased by 54% for MPS coupling agent due to its acrylate functionality being polymerized with the acrylate matrix. The TEM investigation of the nanocomposites containg 7% by weight of boehmite shows the boehmite dispersed well in polymer matrix but it is not fully foliated. While adding silica nanoparticle to the nanocomposite, there is strong affinity between the boehmite and silica nanopartice, the nanoparticles are populated around the boehmite first to form loose aggregation then the excess nanoparticles are dispersed in the polymer matrix.
In conclusion, the platy boehmite nanoparticles are very effective moisture permeation stopper while the spheric silica nanoparticles are very effective mechanical and thermal properties enhancer. The coupling agent exhibits strong influence on the performance of nanocomposite through the chemical reaction with the photoinitiator and polymer matrix.

並列關鍵字

encapsulation ； nanocomposites ； water permeation ； water absorption ； acrylic resin ； boehmite

參考文獻

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