The failures (brittle fracture) occurs at very low nominal operational mechanical service loads. The outer features of the fracture areas are characterized by a razor cut fracture surface running perpendicular to the axis of FRP rods. After the fist brittle fractures occurred it was thought that the effect was initiated by ingress of chemicals such as dilute acids into the composite structure. Investigations at our plant evaluated that nitric acids are the main initiator for this effect. For more information, please visit our Download Center and read our Technical Paper entitled: “FRP RODS for Brittle Fracture Resistant Composite Insulators”.

The only possibility to eliminate brittle fracture of composite insulators at all was considered by using a brittle fracture resistant FRP rod as part of the composite structure. The result of our study has led to such a rod. It was introduced in the manufacturing of RODURFLEX® Insulators in 1983. The number of brittle fractures from RODURFLEX® Insulators installed since 1983 is zero.

A mechanical failure of an overhead transmission insulator will cause line dropping which results in an outage of the transmission line.

If the line is crossing a street or other serious locations the damage besides the line drop himself will be much bigger (safety aspects).

· Usage of boron free ECR glass fibre for the pultrusion of the FRP rod
· Permanent elastic, permanent sticking sealing of the end fitting area

For more information, please visit our Download Center and read our Technical Paper entitled: “FRP RODS for Brittle Fracture Resistant Composite Insulators”.

Yes they are. Since 1983.

Epoxy resins are impregnating compounds with the highest available quality of all comparable polymers for the pultrusion of FRP rod materials. Hot curing epoxy resin in combination with anhydride hardener gives an aging/hydrolysis resistant high strength matrix component. Polyester resins are not hydrolysis resistant and have lower mechanical and electrical properties.

To avoid deterioration due to penetration of moisture into the epoxy resin matrix. This effect may causes hydrolysis inside the rod, which leads to particial discharges and may end in failure. Hydrolysis means that the epoxy matrix system is partially or completely dissolved in water during time. The matrix structure disappears leaving naked glass fibres back.

The major advantages of RODURFLEX® Insulators are associated with their light weight (up to minus 90% compared to ceramics), their flexibility and the hydrophobicity effect of silicone rubber.

Due to the light weight RODURFLEX® Insulators are easy to transport, handle and install. By taking this into consideration during line construction, the towers can be designed according to the lower loads applied to them under service conditions.

The advantage of hydrophobicity is that RODURFLEX® Insulators do not require cleaning under any environmental conditions. Additionally, the leakage current is drastically suppressed.

Besides hydrophobicity, the advantages of SiR are: High flexibility even at low temperatures, high mechanical strength, resistance to weathering; e.g. UV radiation, ozone and heat. Due to these properties, silicone rubber is superior to any other polymeric material.

This saves handling, transportation, installation as well as maintenance costs and line losses.

The light weight, excellent UV resistance and the hydrophobicity/hydrophobicity transfer effect.

Yes, they are. It is a benefit of the used HTV silicone filled with ATH (Alumina trihydrate). The silicone compound is a unique tailormade formulation exclusively used for RODURFLEX® Insulators.

The bulk of RODURFLEX® Insulators contains different materials. The material responsible for T&E resistance is Aluminum trihydrate (ATH). The inorganic filler is also responsible for high tensile strength and high tear resistance.

The filler content is between 40-50% by weigth.

Tracking and Erosion Test specified in IEC 60 587. According to this test silicone rubber used for RODURFLEX® Insulators can be classified as Class 1A4.5 which is the highest class for this test procedure.

Yes, they are. The absorption maximum of SiR is at 290nm. To crack an Si-O-Si bonding 9 – 10eV are necessary. The atmospheric layers are permeable for wavelengths greater than 300nm (UV-B radiation). Due to this situation, UV radiation SiR housing of RODURFLEX® Insulators is exposed to can not deteriorate performance and properties. Because mentioned energy necessary to deteriorate housing or sheds doesn’t exist under service conditions.

HTV silicones possess the highest mechanical strength of all silicones used as housing materials. This is important for the handling and transportation of insulators because high tensile strength, high tear strength and high Shore A hardness avoid damages due to transportation and handling. Furtheron, high Shore A hardness avoids distortion of the sheds.

The excellent insulation performance even under heavy pollution conditions can be explained by the hydrophobicity of the HTV silicone rubber housing and the hydrophobicity transfer to even thick pollution layers. Pollution layers become also hydrophobic when deposited on HTV silicone rubber housings. By this means, conductive surface layers that reduce the flashover performance drastically cannot build up. For more information, please visit our Download Center and read our Technical Paper entitled: "Hydrophobicity effect of silicone housed composite insulators and its transfer to pollution layers".

Silicones are the only housing materials that are able to transfer their intrinsic hydrophobic behaviour to pollution layers. Some other polymers such as EPDM or some special Cycloaliphatics are also hydrophobic but not able to coat the pollution layers deposited on the housing surface. For more information on hydrophobility, please visit our Download Center and read our Technical Paper entitled: "Hydrophobicity effect of silicone housed composite insulators and its transfer to pollution layers".

The hydrophobicity effect and its transfer to pollution layers can be explained by the diffusion of low molecular weight compounds (LMWs) from the bulk to the surface and into the surface pollution layers. Only silicones are able to generate LMWs from its backbone structure and due to this can maintain this effect with no limitation in time. For more information, please visit our Download Center and read our Technical Paper entitled: "Hydrophobicity effect of silicone housed composite insulators and its transfer to pollution layers".

The mechanism of hydrophobicity/hydrophobicity transfer and its life time is under investigation in many research institutes wordwide. At the moment there are more than 100 papers published each year that report of work on this subject. Recent research activity in the field of “hydrophobicity of silicone rubbers” shows that a generation mechanism of LMWs was found to be responsible for maintaining hydrophobicity transfer for the full insulator life time (>30years): Experience with HTV and RTV silicone rubber housings of RODURFLEX® Insulators confirm these findings: after more than 35 years the silicones maintained their hydrophobicity and their ability for hydrophobicity transfer. For more information, please visit our Download Center and read our Technical Paper entitled: "Hydrophobicity effect of silicone housed composite insulators and its transfer to pollution layers".