聚氨酯接枝改性环氧树脂的微观结构

由端-NCO基聚氨酯预聚物(PU)与环氧树脂(EP)反应制备了聚氨酯接枝改性环氧树脂(EP-g-PU),考察了PU和活性稀释剂含量及异氰酸酯结构对EP-g-PU固化物玻璃化转变温度(Tg)和微观形貌的影响。结果表明,EP-g-PU固化物的Tg随PU含量增加而升高,随活性稀释剂含量增加而降低;三种异氰酸酯制备的EP-g-PU固化物的Tg顺序为IPDIMDITDI。异佛尔酮二异氰酸酯(IPDI)和二苯基甲烷二异氰酸酯(MDI)型EP-g-PU固化物的断面形貌为以EP为细胞核、PU为细胞壁的两相细胞状结构,甲苯二异氰酸酯(TDI)型EP-g-PU固化物的断面形貌为PU以岛状分布于EP基体中的海岛结构,但岛相也是以EP为细胞核、PU为细胞壁的两相细胞状结构。

Microstructure of Epoxy Resin Grafted by Polyurethane

Epoxy resins grafted by polyurethane (EP-g-PU) were prepared by reaction of NCO-terminated polyurethane prepolymer with epoxy resin.The effects of content of polyurethane and reactive diluter,diisocyanate structure on Tg and microstructure of cured EP-g-PU were investigated.The DSC results show that Tg of cured EP-g-PU increases with increasing content of polyurethane and decreases with increasing content of reactive diluter.The Tg of cured EP-g-PU derived from different diisocyanate is IPDI>MDI>TDI at the same conditions.The SEM results show that in fracture surface of cured EP-g-PU prepared by IPDI-polyurethane or MDI-polyurethane,epoxy resin is embedded by polyurethane to form a two-phase cell structure.Whereas,in fracture surface of cured EP-g-PU prepared by TDI-polyurethane,polyurethane as the island-phase is dispersed in epoxy resin phase to form an island-sea structure.But a two-phase cell structure of epoxy resin embedded by polyurethane is also observed in the island-phase.