Disclosed is a crosslinkable mixture comprising a polyolefin, an alkoxysilane, an organopolysiloxane, a free radical initiator and a liquid polymer modifier. The organopolysiloxane contains two or more hydroxyl end groups. When the crosslinkable mixture is melt-shaped, a unique crosslinked composition is formed. The liquid polymer modifier improves flexibility of the melt-shaped article without decreasing dielectric strength.