Surface properties of epoxy systems, 1. Influence of the chemical structure on surface energy of monomers, comonomers and additives

The plate method was used to measure the surface tension of different epoxy prepolymers and different hardeners. The values are correlated to the chemical structure. The effect of molecular weight is very weak for diglycidyl ether of bisphenol A (DGEBA) prepolymers. For α,ω‐diamino‐terminated poly(propylene oxide) (PPO) oligomers, the surface tension remains constant when M̄n changes. However, the surface tension increases for PPO oligomers when the number of amino end‐groups increases, and for α,ω‐epoxy‐terminated oligomers when M̄n increases. These results are discussed in terms of a competition between the surface tension of the chain ends and the surface tension of the constitutional repeating units. The surface tension of carboxy‐(CTBN) and epoxy (ETBN)‐terminated butadiene‐acrylonitrile random copolymers is lower than the value of DGEBA prepolymers. In homogeneous blends these oligomers have a surfactant effect.