PU樹脂添加奈米SiO2/TiO2之性能提升研究

Performance Enhancement of Polyurethane Resins by Adding Silica /Titania Nanoparticles

范孝明(Shiao-Ming Fan)

指導教授 ： 林錕松

元智大學/工程學院/化學工程與材料科學學系/碩士(2004年)

摘要

本研究目的主要是以預聚法(prepolymer synthesis)合成PU樹脂(polyurethane resin)，合成方法係採用聚酯多元醇及二異氰酸酯，使之分別與鏈延長劑例如1,4丁二醇，以合成聚氨酯預聚合物，再利用凝膠滲透層析儀(GPC)測量分子量分佈狀況，發現PU樹脂平均分子量約為50000，再添加奈米SiO2微粒至樹脂中，分別以穿透式電子顯微鏡(TEM)及場發掃描式電子顯微鏡(FE-SEM)來觀察粒子之分散狀況，結果發現大部分奈米SiO2微粒能以分散在PU樹脂塗膜中。再針對以不同比例添加量，找出最佳添加顆粒及最佳添加比例，實驗結果顯示50 nm與4 μm奈米SiO2微粒混合比值為3/7，當28天時彈性係數及抗張強度己明顯高於完全添加奈米級PU樹脂，就能提高塗膜的抗張強度、彈性係數和耐候性強度性能等物性。以傅利葉轉換紅外線(FTIR)、X光粉末繞射儀(XRPD)來鑑定添加奈米SiO2微粒後其晶型改變，實驗結果發現奈米SiO2微粒為非結晶型態，奈米SiO2微粒易均勻分佈在塗膜中，並與聚酯貼合化學鍵結合，故彈性係數和抗張強度明顯提升。當系統中加入4和8 %奈米SiO2後，在1735 cm-1處的C=O吸收峰處的吸收峰分别漂移至1729 cm-1和1723 cm-1，因為C=O與OH基反應生成COOH官能機的結合。因此推測奈米SiO2表面的OH基可能已與NCO基發生反應。
研究中更進一步將PU樹脂添加奈米級SiO2/TiO2形成奈米複合樹脂，並以延伸X光吸收精細結構(EXAFS)及X光吸收近邊緣結構(XANES)來探討分析細微結構是否有改變，發現在PU樹脂添加TiO2/SiO2比值分別為0、1及2時，鍵長分別為1.09、1.97及1.96 ± 0.05 Å，其配位數分別約為5、4及4。Ti中O與Si間發生鍵結，故在TiO2/SiO2比值為1時結成Si-O-Ti化學鍵最穩定，以XRPD發現在2θ = 26、38、48、55其pattern明顯起伏存在與SiO2叠加，以FTIR發現其980 cm-1吸收峰中明顯看出奈米SiO2與奈米TiO2鍵結產生Si-O-Ti。再以電子順磁共振儀(EPR)觀察鈦原子之間的相互作用，結果發現吸收峰面積隨TiO2比例増加而增大，最後以拉力試驗機測試，發現添加奈米級SiO2/TiO2之複合樹脂其抗UV強度明顯提升。並且進行物性測試，在耐光性已在8小時均不裂化，故聚氨酯添加奈米級SiO2/TiO2後將會使改質過的樹脂共聚合體物性變佳。

關鍵字

聚氨酯樹脂 ； 奈米微粒 ； 二氧化矽 ； 二氧化釱 ； 性能測試 ； 延伸X光吸收精細結構 ； X光吸收近邊緣結構

並列摘要

The polyester-based polyurethane (PU) was prepared by using prepolymer synthesis method. The materials of polyesterpolyols and diisocyanate were reacted with a chain prolong dosage of 1.4 Butanediol in order to produce the PU resin. By the gel permeation chromatography (GPC) technique, the molecular weight of the PU resin was around 50,000 g/mol characteristically. The silica nanoparticles were embedded and well dispersed into PU resins measured by transmission electron microscopy (TEM) and field emission- scanning electron microscopy (FE-SEM). The optimal mixing ratio of 50 nm/4 μm for SiO2 particles was 3/7. Therefore, the modulus of elasticity, tensile strength or weatherability of the PU resin of this optimal formula was significantly enhanced for comparing with the one of all-nanosized SiO2. The chemical structures and morphology of TiO2-SiO2-PU nanocomposites were also characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometer (XRPD). The results showed that silica nanoparticles were amorphous and evenly dispersed in the PU coatings and intensively bonded with PU interstructures. Measurements of modulus of elasticity or tensile strength of the polyurethane by Instron tester indicated the PU coatings increased after adding silica nanoparticles. The optimal addition of 4 and 8 % of SiO2 into PU resins showed the C=O peaks shifted from 1735 cm-1 to 1729 cm-1 and 1723 cm-1, respectively. Thus, the bonding of C=O with OH might form the COOH group, a conjugation of OH and NCO in silica nanoparticle was observed.
In order to more thoroughly examine the nature of the TiO2-SiO2-PU nanocomposites, the extended X-ray absorption fine structure (EXAFS) or X-ray absorption near edge structure (XANES) spectroscopy was conducted. The Ti EXAFS spectra indicated that the weight ratio of TiO2/SiO2 of 0, 1/1, and 2/1 possesses the bond distances of 1.09, 1.96, and 1.97 ± 0.05 Å, respectively and the coordination numbers (CN) were of 5, 4, and 4, respectively. It also showed that the silica and titania nanoparticles were reacted and formed into Ti-O-Si bonding. In addition, the increasing of UV tensile properties of the PU resin films by the mixing of silica and titania nanoparticles were found. The XRPD patterns represented that the TiO2/SiO2 peaks of 2θ = 26、38、48、55 might undulate. The FTIR spectra also showed that the peak of 980 cm-1 might indicate the SiO2 and TiO2 nanoparticles bond to form the into Ti-O-Si. Electron paramagnetic resonance spectrometry (EPR) showed the adsorptive peaks at 2050 Gauss of Ti species increased with the increasing concentration of Ti. Moreover, Instron tester showed the PU coatings of UV tensile strength increased after mixing TiO2/SiO2 nanoparticles. The PU coating possessed an 8-hr cracking-resistance indicated the performance of PU resins increased by the mixing of embedded TiO2/SiO2 nanoparticles.

並列關鍵字

polyester-based polyurethane ； Nanoparticle ； Silica ； Titania ； Performance test ； EXAFS ； XANES

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