三聚氰胺交联改性水性聚氨酯的制备及性能

Preparation and properties of waterborne polyurethane modified by melamine as crosslinker

以异佛尔酮二异氰酸酯和聚丙二醇(PPG-2000)为主要原料,以三聚氰胺为交联剂,采用预交联(产物记为MWPU)和后扩链(产物记为mWPU)两种交联方式合成三聚氰胺交联改性水性聚氨酯乳液,并与以三羟甲基丙烷(TMP)为交联剂制备的改性聚氨酯(产物记为TWPU)进行了对比。通过测量乳液粒径、红外光谱分析、热重分析、力学性能测试、吸液率计算,考察了交联剂种类、用量以及交联方式对改性乳液及其胶膜结构与性能的影响。结果表明,交联改性增大了乳液的平均粒径,提升了胶膜的铅笔硬度,拉伸强度、热稳定性和耐水性,但对附着力的影响不大。用三聚氰胺改性所得胶膜的性能优于用TMP改性,采用预交联方式改性优于后扩链方式。当交联度为5/20时,MWPU胶膜的拉伸强度达到13.45 MPa,硬段最大分解速率对应温度为351℃,软段最大分解速率对应温度达到404℃。

A waterborne polyurethane emulsion was synthesized from isophorone diisocyanate and polypropylene glycol （PPG-2000） with melamine as crosslinker through pre-crosslinking （the product named as MWPU） or post-chain extending （the product named as mWPU）, and compared with the one modified by trimethylolpropane （TMP） as crosslinker （the product named as TWPU）. The effects of type and amount of crosslinker and crosslinking method on structure and properties of the modified emulsion and its cured film were studied by particle size measurement, infrared spectroscopy, thermogravimetric analysis, mechanical property testing and water absorption rate calculation. The results showed that crosslinking modification enlarges the average particle size of emulsion, improves its film＇s pencil hardness, tensile strength, thermal stability and water resistance, but has a slight effect on adhesion strength. The film obtained using melamine as crosslinker has better performance than that obtained with TMP. Pre-crosslinking is superior to post-chain extending. The MWPU film with a crosslinking degree of 5/20 has a tensile strength of 13.45 MPa, and a temperature at maximum decomposition rate of 351℃ for hard segment and 404 ℃ for soft segment.