Synthesis and Characterization of Dual-Functional Carbamates as Blowing and Curing Agents for Epoxy Foam
Christian Bethke, Simon T. Kaysser, Du Ngoc Uy Lan, Sebastian Manfred Goller, Kasper P. van der Zwan, Jürgen Senker, Holger Ruckdäschel, Volker Altstädt
Abstract
With regard to upcoming regulations of common chemical blowing agents for epoxy foams, carbamates provide suitable alternatives. They act as blowing agents releasing CO2 and cure epoxy resins after decomposition and amine release. Thus, no undesired byproducts occur. In this study, a detailed analysis of the chemical structures, the decomposition, and the curing behavior of the carbamates received from N-aminoethylpiperazine (B-AEP), 4-methylcyclohexane-1,3-diamine (B-DMC), and isophorone diamine (B-IPDA) was attempted. The carbamates were finally used for foaming of diglycidylether of bisphenol-A (DGEBA)-based epoxy resins at different temperatures. By this, the performance of the carbamates in a foaming experiment could be qualitatively compared. The results show that all carbamates are suitable for foaming at specifically adapted temperatures. While B-DMC is able to foam properly only at 80 °C, B-IPDA requires 100–120 °C, and B-AEP is best used for foaming in the range between 120 and 140 °C.