The invention discloses an environmentally friendly impregnation system for fiber surface treatment and a preparation method thereof, and an impregnation treatment method. The environmentally friendly impregnation system for fiber surface treatment of the invention includes hydroxyacrylic resin, amino resin, epoxy resin, blocked isocyanate, accelerator, rubber latex, and deionized water. Depending on the type of fiber and its application, the invention allows for the selection of one-step impregnation treatment or two-step impregnation treatment. The invention can effectively replace the use of toxic raw materials and intermediates in traditional RFL impregnation system, reducing harm to human health and the environment while achieving the adhesion level of RFL treatment.

A polyalkylene glycol terminated poly-carbodiimide has formula 1:

##STR00001##

R.sub.1 is an aliphatic group from about 5 to about 12 carbon atoms, a cycloaliphatic moiety of from about 6 to about 20 carbon atoms, an isosorbide moiety, a 1,3-furan moiety, an L-lysine alkyl ester moiety, a rosin moiety, a cycloaliphatic unsaturated moiety, or a cardanol moiety; R.sub.2 is hydrogen or a methyl group; R.sub.3 is a methyl, ethyl, or propyl moeity; and n and m are integers and are each independently between 1 and about 30.

The invention relates to a curable composition including (a) a component having one or more carbonyl group-containing compounds having a number average molecular weight (Mn) of at least 500 g/mole, wherein each carbonyl group is independently a ketone group or an aldehyde group; (b) a polyamine compound having at least two primary amine groups per molecule; and (c) a polyisocyanate compound. Articles coated with the curable composition are also provided.