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三聚氰胺甲醛树脂具有良好的耐热性和胶接强度大等特点,因此被广泛应用于木材加工用的胶粘剂、涂料的固化剂、纸张湿强剂中。但是三聚氰胺的刚性三嗪环结构会导致三聚氰胺甲醛树脂存在硬脆、力学性能差、强度低、拉伸和弯曲性能差等缺陷。上述缺陷限制了三聚氰胺甲醛树脂在某些领域中的应用。为了扩大其应用范围,三聚氰胺甲醛树脂的增韧问题得到了越来越多的关注。本文主要综述了小分子增韧和高分子增韧两种主要方法,其中小分子增韧又包括异氰脲酸酯增韧、二元醇增韧、二元醛增韧、胺类增韧以及多种小分子协同增韧。高分子增韧包括聚多元醇增韧和聚氨酯增韧。此外,还介绍了生物质增韧、硅烷增韧等其他几种方法,并阐述了上述方法的增韧机理。 相似文献
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Based on the parent tetrazole 2N-oxide, six series of novel carbon-linked ditetrazole 2N-oxides with different energetic substituent groups (-NH2, -N3, -NO2, NF2, -NHNO2) and energetic bridge groups (-CH2-, -CH2-CH2-, -NH-, -N=N-, -NH-NH-) were designed. The overall performance and the effects of different energetic substituent groups and energetic bridge groups on the performance were investigated by density functional theory and electrostatic potential methods. The results showed that most of designed compounds have oxygen balance around zero, high heats of formation, high density, high energy, and acceptable sensitivity, indicating that tetrazole N-oxide is a useful parent energetic compound employed for obtaining high energy compounds, even only combined with some very common energetic substituent groups and bridge groups. Comprehensively considering the effects on energy and sensitivity, the -NO2, -NF2, -NH-and -NH-NH-are appropriate substituent groups for combining tetrozale N-oxide to design new energetic compounds, while -NH2, -N3, -CH2-CH2-, and -N=N-are inappropriate. 相似文献
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半导体光催化技术不仅可以将太阳能转化为化学能,还可以直接降解和矿化有机污染物,因此其在抑制环境污染和解决能源短缺方面具有广阔的应用前景。类石墨相氮化碳(g-C3N4)具有独特的电子能带结构、优异的热稳定性以及化学稳定性,因此g-C3N4作为一种廉价的无金属光催化剂被广泛应用于光解水制氢产氧、污染物降解、光催化CO2还原、抗菌和有机官能团选择性转换等领域。然而,传统热缩聚法合成的g-C3N4光催化剂比表面积小、禁带宽度大、光生电子-空穴易于复合、光生载流子传输慢,抑制了其光催化活性。为了进一步提高g-C3N4的光催化活性,出现了多种改性方法。本文针对g-C3N4光催化剂的改性研究,综述了近年来国内外在g-C3N4光催化剂改性方面的重要研究进展,如采用模板法优化g-C3N4的纳米结构、元素掺杂及共聚合调控g-C3N4的能带结构、贵金属沉积或半导体复合提高光生载流子分离效率等。最后,本文还展望了g-C3N4光催化剂在改性方面的未来发展趋势。 相似文献
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