An electrical crimp connector comprises a metallic crimp barrel adapted to receive the bared end portion of an electrical conductor and a heat-shrinkable polymeric sleeve in which the crimp barrel is received. The insulating sleeve is comprised of an ionic polymer derived from the polymerization of an α-olefin and an ethylenically unsaturated carboxylic acid , a proportion of whose acid groups have been reacted to create ionic carboxylates of metal ions. The ionic polymer sleeve has high impact toughness, high abrasion and chemical resistance, high resistance to splitting by crimping tools, high degrees of flexibility and transparency, and a relatively low heat shrink temperature, making it more suitable for use in such connectors than sleeves comprised of other materials such as polyamides or polyolefins.