Silicones: PDMS Fluids, HTV, LSR & RTV Silicone Rubber and Sealant Bases

Dimethyl silicone fluids by viscosity, solid and liquid silicone rubber, and RTV systems for sealant makers

Silicones in primary forms are one customs code, HS 3910.00, and three trades. The most common siloxane is linear polydimethylsiloxane (PDMS), a silicone oil made from dimethyldichlorosilane and sold in viscosities from a thin pourable liquid to a thick semi-solid; it is used as a lubricant, thermic and hydraulic fluid, electrical insulating fluid in wet-type transformers, damping fluid, mould release agent, antifoam and cosmetic ingredient. The second trade is silicone rubber. Solid silicone rubber, known as HTV, is peroxide-curing and is processed by extrusion, calendering and compression, transfer or injection moulding; liquid silicone rubber (LSR) is a two-part, generally platinum-curing grade injection moulded on automated machines; and room-temperature-vulcanising (RTV) systems are either one-part compounds that cure at room temperature for bonding, sealing and encapsulating, or two-part grades that are addition- or condensation-curing. Silicone rubber is made from about 10 to 100 Shore A and keeps useful properties from -55 to 300 °C, which puts it in voltage-line insulators, cable insulation, seals, moulds, electronics and medical devices. The third trade is the base for sealants: one-part building sealants cure by absorbing atmospheric moisture, and acetoxy systems, the chemistry of household bathroom caulk, release acetic acid as they cure. Finished sealants can be declared outside chapter 39 - India's anti-dumping notification on silicone sealants lists tariff items in chapters 32 and 35 - while fluids, rubber and base polymers stay in 3910.00.

End uses carry their own limits. In the USA, 21 CFR 173.340 allows dimethylpolysiloxane of 300 to 1,050 centistokes at 25 °C as a defoaming agent at up to 10 ppm in food, and 21 CFR 177.2600 lists methyl, methyl-phenyl, methyl-vinyl and fluoro silicone elastomers for rubber articles in repeated food contact. In the EU, D4 and D5 cyclic siloxanes may not be placed on the market in wash-off cosmetic products at 0.1% by weight or more since 31 January 2020, so the residual cyclic content is stated when a fluid is bought for EU personal care. India has applied anti-dumping duty on silicone sealants from China since December 2021, for five years, at USD 397 to 739 per MT by producer, with sealants for solar photovoltaic modules and thermal power applications excluded. UN Comtrade 2024 export declarations under HS 3910.00 total about USD 6.61 billion and 1.21 million MT across 110 reporters: China USD 1.45 billion and 545,600 MT, the USA USD 1.39 billion and 131,000 MT, Japan USD 738 million, France USD 386 million, the Netherlands USD 375 million, the UK USD 371 million and 91,600 MT, Korea USD 293 million, Thailand USD 239 million and 57,600 MT, Belgium USD 205 million and Italy USD 171 million. Germany declares no exports under the code in the 2024 data, but importers in 121 reporting countries declared USD 1.71 billion and about 304,500 MT from Germany. Those are declared trade values, not offers.

The buyer is a sealant or adhesive formulator, a cable, hose or profile extruder, an LSR moulder, a mould maker, a personal-care, textile or process-chemicals formulator using fluids, or a distributor. CBIL is a commodity brokerage company and brokers silicone fluids, silicone rubber and RTV systems from producers and their offtake traders in China, the USA, Germany, Japan, France, the UK, Korea and Thailand, against the producer's certificate of analysis for viscosity or hardness, the safety data sheet, a certificate of origin, a REACH statement for EU imports, where polymers are exempt from registration, and food-contact declarations where the end use needs them. Fluids and bases move in drums or IBCs and rubber in the producer's pack, in containers on FOB, CFR and CIF terms, priced per MT on grade, pack and origin; minimum quantities are confirmed per product and pack, and the duty at destination is checked for the route before an origin is fixed. Send the product, the viscosity or hardness, the cure system, the end use, pack, monthly volume and discharge port, and the enquiry is screened and worked against it.

Excluded origins are not offered, including product re-exported, blended or re-processed through a third country. Every lot moves with a certificate of origin naming the producing plant, mine or grower country, and nothing is quoted before the seller and loading point are known.