Good afternoon, "E" is the "epoxy value" representing its epoxy equivalent, that is, the epoxy value marked on the barrel of component A. The bigger the number, the easier it is to react, and the higher the crosslinking density, the better the performance. Physically, the higher the epoxy value, the lower the monomer viscosity, so you can see that E- 15 is solid, E-20 is solid, and E-35 is liquid. They just have the same crosslinking mechanism and different epoxy equivalents, so curing agents such as 65 1, aliphatic amine, aromatic amine or enamine can be used interchangeably.