The present invention relates to an alpha-alkoxysilane-terminated prepolymer preparable by reaction of at least one polyether polyol, of a polyisocyanate and of an alpha-alkoxysilane having at least one isocyanate-reactive group, said polyether polyol having a weight average of 500 to 7000 g/mol and having ethylene oxide and propylene oxide units, the proportion of ethylene oxide units being up to 50% by weight based on the polyether polyol. The invention further provides a process for preparing an inventive alpha-alkoxysilane-terminated prepolymer, a composition, a multicomponent system and a spray can comprising an inventive alpha-alkoxysilane-terminated prepolymer, and also a moulding obtainable by polymerization from an inventive alpha-alkoxysilane-terminated prepolymer.