A method for forming a piston seal of a hydraulic pump includes forming a reaction mixture that includes a prepolymer component, a polyol additive, a diol component, and a curative component, forming a sealing element with the reaction mixture and a mold, and curing the sealing element to form a piston seal of a hydraulic pump. The prepolymer component includes a polycarbonate-isocyanate prepolymer that is a reaction product of at least an isocyanate component and a polycarbonate polyol component.