以水溶性聚醯胺酸為螯合劑之環保型混合材料於鋼材防腐蝕之應用研究

Abstract

鋼材因其優異的機械性質與成本效益，廣泛應用於建築、交通與工業等領域。然而，其在高濕與高鹽環境中極易腐蝕，導致結構劣化與重大資產損失，對經濟與公共安全構成嚴重威脅。傳統防腐塗層多採用溶劑型系統，但其所釋放的揮發性有機化合物(volatile organic compounds)對環境與人體健康造成負擔。為實現低污染且高效能之防腐機制，開發具環境友善性的水性混成塗層已成為材料科學中的重要研究趨勢。 本研究開發一種以高分子分散液為基礎之環保型水性塗層系統，用於鋼鐵(mild steel)之防腐蝕應用。首先，以乙二胺四乙酸二酐(ethylenediaminetetraacetic dianhydride)與2,2-(乙二氧基)雙(乙胺)(2,2-(ethylenedioxy)bis(ethylamine)合成具水溶性的聚酰胺酸(polyamic acid, PAmA)。其分子主鏈中之醚鍵與酰胺酸官能基提供大量極性位點，有助於促進3-甘油氧丙基三甲氧基矽烷(3-glycidoxypropyl trimethoxysilane, GPTMS)形成穩定的水性有機矽烷分散體，且無需額外添加界面活性劑或鹽類。進一步地，系統中最多可以25 wt%之四乙氧基矽烷(tetraethyl orthosilicate)替代GPTMS，以作為交聯劑與奈米二氧化矽前驅物，經最佳化條件製備水性有機/無機混成分散液。 與傳統聚丙烯酸分散液相比，本研究所製備之PAmA基有機/無機分散液經拉曼光譜(Raman spectroscopy)與29Si 核磁共振(29Si-NMR)分析顯示其縮合程度高達94.6%，證實已形成高交聯密度的矽氧網路結構，具被動保護層功能。該塗層在熱重分析中表現出超過380 °C的熱分解溫度，顯示出優異的熱穩定性。此外，PAmA的應用不僅促進交聯反應與矽氧結構生成，亦有助於形成酰亞胺結構，進一步增強塗層系統的結構完整性與化學穩定性，該現象亦由傅立葉轉換紅外光譜(FTIR)與示差掃描量熱分析(DSC)所驗證。

Steel is widely utilized in construction, transportation, and industrial sectors due to its excellent mechanical properties and cost-effectiveness. However, its high susceptibility to corrosion under humid and saline environments often results in structural degradation and significant asset loss, posing serious economic and safety concerns. Conventional anticorrosive coatings predominantly rely on solvent-based systems, which emit volatile organic compounds that are detrimental to both environmental and human health. In pursuit of low-pollution and high-efficiency corrosion protection, the development of eco-friendly waterborne hybrid coatings has become a key research direction in materials science. In this study, an environmentally friendly waterborne coating system was developed using a polymeric dispersion as the base, intended for corrosion protection of mild steel. A water-soluble polyamic acid (PAmA) was first synthesized via the reaction of ethylenediaminetetraacetic dianhydride and 2,2-(ethylenedioxy)bis(ethylamine). The incorporation of ether linkages and amic acid functional groups into the polymer backbone introduces numerous polar sites, which facilitate the formation of a stable aqueous silane dispersion primarily composed of 3-glycidoxypropyl trimethoxysilane (GPTMS), without the need for surfactants or salts. Up to 25 wt% of GPTMS can be replaced with tetraethyl orthosilicate , which functions as a crosslinking agent and a precursor to nanosilica, thereby forming an aqueous organic/inorganic hybrid dispersion under optimized conditions. Compared with reference samples such as polyacrylic acid dispersions, the PAmA-based organic/inorganic dispersion exhibited a high degree of condensation (94.6%) as confirmed by Raman spectroscopy and ²⁹Si nuclear magnetic resonance (²⁹Si-NMR), indicating the formation of a highly crosslinked siloxane network. This structure acts as a passive layer and contributes to the thermal decomposition temperature of the hybrid coating exceeding 380 °C, as demonstrated by thermogravimetric analysis. The presence of PAmA not only enhances the crosslinking density and silica network formation but also facilitates the development of imide structures, resulting in a more robust sol-gel derived hybrid coating system. These observations are consistent with findings from Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) analyses.