醋酸乙烯酯的竞争反应对N-羟甲基丙烯酰胺接枝热固性淀粉基木材胶黏剂制备及性能的影响
首发时间:2021-01-22
摘要:本文通过引入N-羟甲基丙烯酰胺(NMA)来改善无甲醛淀粉基胶黏剂的性能并赋予其热固性。当醋酸乙烯酯(VAc)添加量为淀粉干基的6%,NMA添加量为4%时,胶黏剂的湿强度达到1.4 MPa,淀粉占总固含量的86.6%。热重分析(TGA)、傅里叶变换红外光谱(FTIR)和残留率测试表明,VAc可以适当降低NMA的接枝密度,避免NMA局部过度接枝形成凝胶。此外利用拉曼显微镜证实了VAc有效的提高了NMA分布的均匀性,制备出了具有流动性和较好稳定性的淀粉基胶黏剂。1H-NMR谱的化学位移和13C-CPMAS谱出现的明显的肩峰证明了VAc和NMA都更倾向于与淀粉C6位点的羟基发生反应,二者形成竞争性反应,从而抑制NMA与淀粉的过度反应。拉曼光谱统计分析表明,既与VAc接枝又与NMA发生反应的淀粉颗粒占胶黏剂总体的40.3%,并对胶黏剂的耐水性起决定性作用。
关键词: 食品科学 耐水性 无甲醛 高淀粉占比 反应均匀 活性位点
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Competitive reaction effect of vinyl acetate on preparation and characterization of thermosetting starch-based wood adhesives grafted by N-Methylol acrylamide
Abstract:N-methylol acrylamide (NMA) were introduced to improve characters and realize the thermosetting property of formaldehyde free starch-based adhesive. The content of NMA in adhesive was raised to 4% with the addition of 6% vinyl acetate (VAc), in which the wet strength reached 1.4 MPa and the starch accounted for 86.6% of the total solid content. It was observed from thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) and residual rate test that VAc could reduce the graft density to avoid forming gelation, which caused by local overgrafting of NMA. In addition, Raman microscopy was applied to prove that uniformity of NMA had been improved by VAc and the preparation of starch-based adhesive with fluidity and better stability was achieved. Chemical shifts in 1H-NMR spectrum and the appearance of a significant shoulder in 13C-CPMAS spectra pCompetitive reaction effect of vinyl acetate on preparation and characterization of thermosetting starch-based wood adhesives grafted by N-Methylol acrylamideroved that VAc and NMA were inclined to react at hydroxyl groups at C6 sites of starch to form a competitive reaction effect in order to inhibit overreaction between NMA and starch. Statistical analysis of Raman spectrums showed that the ingredients of starch reacted with both VAc and NMA, which accounted for 40.3% of the total particles, played an important role in the water resistance of adhesives. (10 Points, Times New Roman)
Keywords: Food science Water resistance Formaldehyde free High starch proportion Reaction uniformity Active sites
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醋酸乙烯酯的竞争反应对N-羟甲基丙烯酰胺接枝热固性淀粉基木材胶黏剂制备及性能的影响
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