Abstract: ［Objective］ To meet the protective requirements for certain engine parts that areexposed to moderate operating temperature of ≤120 ℃ for long periods，a two-component clear coating based on silicone-modified waterborne polyurethane（Si-WPU）was developed.［Methods］Si-WPU dispersion was synthesized by the prepolymer-dispersion method，and paired with a hydrophilic modified polyisocyanate curing agent. The developed dispersion was characterized by infrared spectroscopy（FT-IR）， and the synthesis mechanism of Si-WPU，the curing mechanism，and the preparation process of two-component clear coating were studied. The key properties of the coating， including heat resistance（120 ℃），wear resistance，and chemical resistance，as well as the dispersion’s stability were systematically analyzed.［Results］The results showed that the Si-WPU dispersion canbe successfully prepared and remains stable even after centrifuging at 8 000 r/min for 20 minutes. With a 33% addition of organosilicon，after long-term thermal aging at 120 ℃，the adhesion remained at grade 1，the pencil hardness was ≥H，the water absorption rate was ≤5%，and the resistance to engine oil，coolant，and other media met the actual application requirements of engine parts.［Conclusion］ This provides an environmentally friendly and efficient protective coating solution for engine parts witha maximum operating temperature of ≤120 ℃.

Key words: silicone-modification, waterborne polyurethane, two-component varnish, heat resistance, wear resistance

摘要： 【目的】针对长期处于 ≤120 ℃的中温工况且存在一定程度机械摩擦的发动机外表特定部位的耐热耐磨防护。【方法】采用预聚体 -分散法合成了主链含有机硅的改性水性聚氨酯（ Si-WPU）分散体，然后与亲水改性多异氰酸酯固化剂混合，制备有机硅改性水性聚氨酯（ Si-WPU）双组分清漆。采用红外光谱仪（ FT-IR）表征所得分散体，系统分析分散体的稳定性和涂层的耐热性（ 120 ℃）、耐磨性和耐介质性等关键性能。【结果】所制备的 Si-WPU分散体在 8 000 r/min下离心 20 min仍保持稳定；在有机硅添加量 33%时，涂层在 120 ℃热老化 1 000 h后附着力仍保持 1级、铅笔硬度 ≥H、溶胀率 ≤5%，且耐机油、耐冷却液等性能均满足发动机部位实际使用要求。【结论】开发的有机硅改性水性聚氨酯清漆，低毒环保且性能可靠，为发动机表面部件耐热耐磨防护提供了可参考的工程化解决方案。

关键词: 有机硅改性, 水性聚氨酯, 双组分清漆, 耐热性, 耐磨性

CLC Number: 

• TQ637. 81