藉由導入微量電活性苯胺五聚體側鏈官能基以有效提升聚亞醯胺塗層之金屬防蝕效果之應用研究

Effectively enhance the corrosion protection of polyimide coating on CRS electrode by incorporation of small amount of electroactive aniline pentamer as pendant group

10.6840/cycu201700691

李致瑋

聚亞醯胺 ； 側鏈電活性 ； 防蝕 ； 苯胺寡聚體 ； Polyimide (PI) ； Pendant-Electroactive ； Anticorrosion ； Aniline oligomer

中原大學化學系學位論文

2017年

碩士

葉瑞銘

繁體中文

本碩士論文的研究主軸在開發電活性聚亞醯胺，並將其應用在金屬防蝕塗料的研究上，並利用電化學上量測其防蝕的量化效果。 首先，利用有機合成方式，依序將苯胺五聚體(AP)、五聚體-二氟苯單體(AP-DFB)及側鏈苯胺五聚體之二胺單體(P-DAM)合成出來，進一步使用液相層析質譜儀(LC-MS)確認其分子量，並利用傅立葉轉換紅外光譜(FT-IR)鑑定其特徵官能基、核磁共振光譜(NMR)進行化學結構之判定。 再使用化學法(即紅外光-可見光光譜儀(UV-visible))及電化學法(即循環伏安法(CV))證實P-DAM的氧化還原特性。 在電活性聚亞醯胺的熱縮合製備方面，將不同比例之側鏈苯胺五聚體之二胺單體(P-DAM)與4,4’-二胺基二苯醚(ODA)溶解於N-甲基吡咯烷酮(NMP)中做為聚亞醯胺反應之二胺單體溶液，經過升溫攪拌後，再加入二酸酐單體(BPADA)，進行反應得到聚醯胺酸(polyamic acid)溶液，將溶液塗布在冷軋鋼片上進行、烘乾退火(270C)等熱縮合步驟，最後即可得到不同比例具側鏈苯胺五聚體之電活性聚亞醯胺(EPI)塗層。 進一步利用傅里葉轉換紅外光譜(FT-IR)鑑定來判斷亞醯胺化反應(Imidization)的效果，同樣的，利用循環伏安法(CV)確認EPI之電活性，當電活性比例愈高，其氧化、還原電流也隨之增高。 但經由測試前驅聚醯胺酸的黏度顯示: 導入越多的側鏈苯胺五聚體於電活性聚亞醯胺中會大幅降低高分子的聚合度(對應於黏度)，進而降低相對應的電活性聚亞醯胺的熱性質與機械性質(由DSC及TGA顯示)。 因此，若電活性聚亞醯胺薄膜內具有太多的側鏈苯胺五聚體含量，將會使造成所合之電活性聚亞醯胺無法成膜(意即膜會有碎裂狀況發生)，而無法應用於後續電化學防腐蝕塗料的研究上。 由實驗結果顯示，電活性聚亞醯胺薄膜具有5 莫耳%的側鏈苯胺五聚體(EPI5)含量仍可成膜，超過5 莫耳%，則膜材會碎裂而無法應用。 最後，在電化學腐蝕的量測方面，以塗佈電活性聚亞醯胺薄膜的冷軋鋼片(直徑1.8 公分)作為測試樣品，以標準電化學腐蝕量測法量測塔伏(Tafel)曲線及電化學阻抗(Impedance)，來測試具不同側鏈苯胺五聚體含量(0, 1, 3, 5莫耳%)的電活性聚亞醯胺薄膜對金屬防腐蝕的能力。 由塔伏曲線發現，所合成之電活性聚亞醯胺以EPI5具最好的防蝕能力。 另一方面，由電化學阻抗測得的奈奎斯特圖(Nyquist plot)及伯德圖(Bode plot)亦發現同樣的趨勢，兩圖譜都再次證實了EPI5具有最佳的防蝕效果。 電活性聚亞醯胺薄膜的電催化能力可促使下方接觸的金屬表面(如: Fe)產生緻密的鈍性金屬氧化層(如: Fe2O3及Fe3O4)，此現象亦以拉曼光譜(Raman)光譜證實，其中以EPI5所產生的鈍性金屬氧化層拉曼特徵峰值最為明顯。

In this study, a series of electroactive polyimide containing pendant aniline pentamer was synthesized and characterized, followed by employed in anticorrosion coating application. First, aniline-pentamer (AP), pentamer-difluorobenzene (AP-DFB) and pendant electroacive-diamine monomer (P-DAM) were synthesized, followed by performing the structure characterization with LC-MS, FT-IR and 1H-NMR spectroscopy. The reversible redox capability of P-DAM can be further monitored by chemical approach (UV-visible absorption spectroscopy) and electrochemistry approach (cyclic voltammetry). Subsequently, for the preparation of electroactive polyimide, specific feeding ration of diamine for P-DAM and 4,4'-Oxydianiline (ODA) were dissolved in NMP. 4’-(4,4’-isopropylidene-diphenoxy) bis(phthalic anhydride) (BPADA) was introduced into the previous mixing solution. After heating treatment, pendant-electroactive poly(amic acid) (PAA) solution had made. After casting onto the surface of specific substrate, the electroactive polyimide (EPI 1, EPI3, EPI5) can be obtained by treating PAA with thermal imidization at specific programmed heating. The as-prepared electroactive polyimide was further characterized by FTIR spectroscopy. The redox capability of as-prepared electroactive polyimide containing different molar percentage of pendant aniline pentamer was further identified by cyclic voltammetry. However, based on the studies of viscosity for corresponding electroactive poly(amic acid), increasing the feeding molar ratio of pendant aniline pentamer in as-prepared electroactive polyimide may decrease the degree of polymerization of polymers, as reflecting by the decreasing of thermal/mechanical property of polymers (as evidenced by TGA and DSC data). It should be noted that, if the molar percentage feeding ratio of P-DAM excessed 5 mole%, the film formation of electroactive polyimide (EPI) was fail and became brittle. Therefore, following electrochemical corrosion of as-prepared EPI coating containing pendant aniline pentamer was focused on PI, EPI1, EPI3 and EPI5. For the investigation of anticorrosion properties of as-prepared EPI, the Tafel plots and electrochemical Impedance spectroscopy approach were used to study upon cold rolled steel (CRS) coupons. It should be noted that the EPI5, as compared to that of EPI1 and EPI3, was found to show the best corrosion protection upon CRS. Moreover, Nyquist/Bode plot was found to exhibit similar trend of corrosion protection. Redox capability of EPI coating upon underlying metal substrate was also found in this study, the densely passive metal oxides (Fe2O3 and Fe3O4) layers were induced by EPI and confirmed by Raman spectroscopy.

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