Polymer insulation for outdoor use has become increasingly more important and is expected to dominate the future HV-outdoor applications. Polymeric insulators were reported to have performed better than porcelain and glass in laboratories and outdoor test sites. This paper reports an experimental investigation concerned with electrical and surface properties of a silicone-modified polymer in comparison with silicone rubber (SIR), ethylene-propylene-diene monomer (EPDM), and alloys of SIR-EPDM. The loss of hydrophobicity of polymeric materials induced by UV, salt spray, and water salinity aging was examined in this work. An ATR-FTIR technique was used to study the surface degradation of polymers occurring during UV aging. Tracking and erosion induced by high-electrical stresses reduce the lifetime of polymeric materials used for outdoor insulation. The results of standard tests showed that silicone rubber suffers from a deterioration of tracking resistance, caused by the loss of hydrophobicity from the action of water salinity stresses. The silicone-modified polymer shows good hydrophobicity behavior in environmental conditions and excellent tracking and erosion resistance, as compared to SIR, EPDM, and alloy of SIR-EPDM. (C) 2005 Wiley Periodicals, Inc.