Use of reactive polyetherimide to modify epoxy thermosets. I. Synthesis of an amino-grafted polyetherimide

The use of a nonreactive thermoplastic (TP) that is initially miscible and which phase separates during reaction has often been used to improve the toughness of epoxy networks. Most of the time no real improvement in fracture properties is obtained due to poor adhesion between phases. In this work the grafting of amino groups on the backbone of a polyetherimide (PEI) is studied. In order to avoid too high a degree of grafting and crosslinking of PEI, a synthesis in a dispersed medium is considered. Three amines are used: ethylene diamine (EDA), 1-2 aminoethyl-piperazine (AEP) and n-butylamine. The grafting reaction was characterized by FTIR, SEC and NMR. The influence of the drying and washing processes of the powder is shown. The degree of grafting is determined using both titration and nitrogen microanalysis and is in the range 1–5%. The glass transition temperatures of the amino grafted PEI decrease, almost linearly with the degree of grafting.