{"id":12471,"date":"2026-09-03T03:39:04","date_gmt":"2026-09-03T03:39:04","guid":{"rendered":"https:\/\/www.raxpower.com\/?p=12471"},"modified":"2026-09-03T03:39:04","modified_gmt":"2026-09-03T03:39:04","slug":"%d1%80%d1%83%d0%ba%d0%be%d0%b2%d0%be%d0%b4%d1%81%d1%82%d0%b2%d0%be-%d0%bf%d0%be-%d1%80%d0%b5%d1%86%d0%b5%d0%bf%d1%82%d1%83%d1%80%d0%b5-%d0%b8%d0%b7%d0%be%d0%bb%d1%8f%d1%82%d0%be%d1%80%d0%be%d0%b2","status":"publish","type":"post","link":"https:\/\/www.raxpower.com\/ru\/blog\/silicone-rubber-insulator-formulation-guide\/","title":{"rendered":"\u041f\u043e\u0447\u0435\u043c\u0443 \u0441\u0438\u043b\u0438\u043a\u043e\u043d\u043e\u0432\u0430\u044f \u0440\u0435\u0437\u0438\u043d\u0430 \u044d\u0444\u0444\u0435\u043a\u0442\u0438\u0432\u043d\u0430 \u0434\u043b\u044f \u043a\u043e\u043c\u043f\u043e\u0437\u0438\u0442\u043d\u044b\u0445 \u0438\u0437\u043e\u043b\u044f\u0442\u043e\u0440\u043e\u0432"},"content":{"rendered":"

A composite insulator earns its keep in the first millimetre of its sheds. That grey skin is a silicone rubber compound, and its recipe decides how the housing ages under pollution, sun and dry-band arcing. Base polymer, cure system and filler package are the three levers inside that recipe. Anyone comparing two silicone rubber composite insulator quotations is often comparing two formulations without realising it.<\/p>\n

The 170+ specialists at RaxPower have manufactured pole line hardware since 2003, and housing-compound questions reach the engineering desk every week. This guide consolidates the chemistry behind those answers: what the polymer is, how it cures, what the fillers do, and which tests expose the differences between compounds.<\/p>\n

A Backbone Built From Silicon and Oxygen<\/h2>\n

Most insulation polymers hang from a chain of carbon atoms. Silicone does not. Silicones are polydimethylsiloxanes, or PDMS, built from repeating silicon-oxygen units, and each silicon atom carries two methyl groups. That single structural difference sets the whole material apart from hydrocarbon-based elastomers.<\/p>\n

The backbone explains two housing behaviours at once. PDMS is hydrophobic, so water withdraws into discrete beads instead of filming across a shed. Like a car’s freshly waxed hood, the methyl-terminated surface simply refuses to wet. The siloxane chain is also unusually flexible, which keeps the elastomer mobile through decades of thermal cycling.<\/p>\n

Suppliers file the material under the abbreviation VMQ. The Q denotes a rubber with silicon and oxygen in the polymer chain. The M stands for the dominant methyl groups, and the V marks the vinyl groups that act as the curable species. A silicone rubber composite insulator housing is therefore a vinyl-functional PDMS compound, formulated and crosslinked to hold its shape outdoors.<\/p>\n

Three Cure Routes to One Housing<\/h2>\n

Curing converts the uncured compound into an elastic solid by forming covalent bonds between polymer chains. Depending on the class of silicone rubber, peroxides, silanes or SiH-containing siloxanes provide that crosslinking. The route a compounder chooses fixes the product form every silicone rubber composite insulator housing will take.<\/p>\n

Peroxide Cure for Solid Rubber<\/h3>\n

High-consistency rubber, HCR, arrives as high-viscosity logs and is the classic solid silicone of insulator housings. HCRs are typically peroxide-curing materials, although one- and two-component addition-curing systems also exist. Peroxide curing is widely used, and the reaction leaves breakdown products behind, so manufacturers treat parts in a post-cure oven that greatly reduces the residue.<\/p>\n

Platinum Addition Cure for Liquids<\/h3>\n

Liquid silicone rubber, LSR, is a two-component material with a viscosity between roughly 10,000 and 1,000,000 millipascal-seconds, and every LSR is addition-curing. Platinum-catalysed addition, known as hydrosilylation, joins Si-H-rich crosslinkers to vinyl-functionalised polysiloxanes, and the reaction produces no byproducts. Clean chemistry is the reason the route dominates liquid processing.<\/p>\n\n\n\n\n\n\n\n\n
Family<\/th>\nCure chemistry<\/th>\nProduct form<\/th>\nWhere you meet it<\/th>\n<\/tr>\n<\/thead>\n
HTV \/ HCR<\/td>\nPeroxide, or platinum addition<\/td>\nSolid logs, hot-cured<\/td>\nMoulded sheds and sheaths<\/td>\n<\/tr>\n
LSR<\/td>\nPlatinum addition, two components<\/td>\nPumpable liquid in drums<\/td>\nInjection-moulded housings<\/td>\n<\/tr>\n
RTV-1<\/td>\nMoisture condensation, one part<\/td>\nPourable coating<\/td>\nCoatings on ceramic insulators<\/td>\n<\/tr>\n
RTV-2<\/td>\nTwo-part polyaddition or polycondensation<\/td>\nRubber kit<\/td>\nJoint filling and repair<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n\"Uncured
Uncured liquid silicone rubber before crosslinking<\/figcaption><\/figure>\n

Room-Temperature Silicones Serve Different Jobs<\/h2>\n

Room-temperature materials, grouped as RTV, crosslink at comparatively low temperature by polyaddition or polycondensation. They come as two-component rubbers or as one-component coatings. Curing of RTV-1 materials relies only on exposure to ambient moisture, which is why a coating skins over in the field rather than in an oven.<\/p>\n

Thickness separates the two product roles. A moulded housing specimen needs at least three millimetres, while typical coating thicknesses average only about 300 micrometres on glass or porcelain substrates. The bulk housing and the field coating therefore play different roles in an insulation programme, and coating application belongs to maintenance decisions rather than compound selection.<\/p>\n

The same compound families also enclose other equipment. CIGRE Working Group D1.27 examined polymeric materials used as external housings for insulators, arresters, bushings and instrument transformers, so a compound proven on line insulators often reappears across the station. Silicone-housed surge arresters and cutouts<\/a> share that lineage.<\/p>\n

\n\"Grey
Silicone-housed arrester: the same compound family at work<\/figcaption><\/figure>\n

Why ATH Filler Carries the Tracking Duty<\/h2>\n

When the surface of a polluted shed dries in bands, small arcs ignite across each wet-dry boundary and concentrate their energy on a few square millimetres of rubber. Alumina trihydrate, ATH, is the compound’s answer. ATH cools that attack the way you cool your own skin: by releasing water and absorbing heat.<\/p>\n

The chemistry is precise. Aluminium hydroxide starts to decompose at around 180 to 220 degrees Celsius, depending on type, absorbing a considerable amount of heat and giving off water vapour. That endothermic response starves the dry-band arc of thermal energy, and silicone compounds use ATH to raise resistance to tracking, erosion and corona.<\/p>\n

The effect is measurable, not cosmetic. In HTV silicone formulations, a high level of tracking and erosion resistance relates directly to ATH filler content. Independent university tests compared three material families. An unfilled castable silicone and an ATH-filled HTV both lasted far longer than a structural distribution material, which failed once leakage current exceeded the 60 milliampere threshold.<\/p>\n

How Formulators Defend ATH Against Acid<\/h2>\n

Filler strength has one documented enemy. Nitric acid, generated near energised hardware, attacks and decomposes the ATH filler inside an HTV housing. In published immersion tests, ATH-filled formulations showed significant crack formation, the worst cracking belonged to a compound with non-silane-treated ATH, and the unfilled HTV showed no cracks at all.<\/p>\n

The countermeasures are formulation variables, not factory fixes. Developers can substitute an inert filler, optimise silane treatment, particle size and distribution of the ATH, or add a buffering agent for the acid. In our view, silane surface treatment is the quiet variable here: it changes how the filler bonds, cracks and ages long before any visible shed damage appears.<\/p>\n

The challenge, as one housing developer put it, is achieving acid resistance without compromising other material properties, especially a high level of tracking and erosion resistance. Formulators work from a limited set of components: base polymer, curing agent, ATH fillers with their particle size, distribution and surface treatment, plus selected additives.<\/p>\n

\n
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Specifying Housings by Compound?<\/p>\n

Sort composite insulator options by test evidence, not brochure adjectives. The compound data sheet and the tracking test report tell you what the sheds will do in year ten.<\/p>\n

Browse Overhead Line Insulators<\/a>\n<\/div>\n

\n\"Composite\n<\/div>\n<\/div>\n

How the Inclined Plane Test Rates Compounds<\/h2>\n

The inclined plane test exists to compare housing compounds at their worst. Its purpose is to evaluate the tracking and erosion performance of a polymeric housing material. The method starts by cheating: a wetting agent destroys inherent hydrophobicity, simulating the late-aged phase from the first minute.<\/p>\n

One widely used procedure follows IEC 60587, Method 1, at constant voltage with the leakage-current criterion. A published housing study states the pass conditions plainly: the test runs at 4.5 kilovolts AC and is deemed passed after six hours if none of five specimens:<\/p>\n