Octamethylcyclotetrasiloxane, simply known as D4, belongs to the group of cyclic siloxanes. Industry often looks to this clear, colorless liquid as a fundamental ingredient for producing silicone-based products. People in the lab recognize D4 by its ring structure, which carries the molecular formula C8H24O4Si4. When poured into a beaker, D4 moves smoothly, showing low viscosity characteristics. Some might know it from its mild, sweet odor, which sets it apart from many harsh industrial chemicals. The molecular weight lands at about 296.62 g/mol, while the measured density typically hovers near 0.956 g/cm³ at 25°C. This silicon-based compound stands as a chemical building block for a variety of everyday materials, including personal care products, lubricants, and certain types of coatings.
D4 usually reaches warehouses and factories as a crystal-clear liquid, though producers occasionally supply it in flakes or even as small pearls. Seeing D4 in a solid or powder format doesn’t happen often because the substance stays liquid under normal conditions. The boiling point sits around 175°C, and it carries a melting point close to 17°C – so in cooler rooms it’s not unheard of for D4 to look semi-solid or waxy. For high-volume transport and storage, drums and IBC tanks provide a familiar sight, supporting easy handling and measured dispensing for large-scale manufacturing. Each shipment ought to come with specifications on purity, which typically reaches 99% or higher for industrial and pharmaceutical applications.
At its core, D4 features a four-membered ring made up of alternating silicon and oxygen atoms, with eight methyl groups tucked along the sides. This structure gives the molecule distinct thermal stability, a low tendency to oxidize, and a strong resistance to acids and bases. Its hydrophobic nature means water cannot dissolve it—an asset for anyone designing waterproof coatings or antifoam agents. Since D4 evaporates quickly at room temperature, those working in labs notice how quickly the liquid disappears from open flasks. This high volatility also means users need to keep workspaces ventilated. The chemical keeps its structure across a broad range of environments, helping manufacturers create products that last and perform well in heat, cold, or constant sun.
Density gives manufacturers a clear idea about storage, transport, and blending with other ingredients. D4’s density stands slightly less than most common solvents, so it will float on water. This property limits its mixing with heavier fluids but supports designs for lightweight emulsions and dispersions. In practice, this attribute fits especially well into cosmetics and personal hygiene formulas meant to give a non-greasy feel. Chemists appreciate D4’s consistent performance, which comes from its precise molecular weight and stable crystal lattice, even though most product uses focus on its liquid state. Bulk suppliers sometimes offer it by the liter, and customers familiar with flammable chemicals handle D4 using grounded drums and anti-static tools, reducing risks posed by its low flash point.
D4’s international commerce often runs under HS Code 2931.90, which the global regulatory community recognizes for a variety of organosilicon compounds. That number helps customs officials, freight forwarders, and logistics professionals track and tax D4 shipments properly. It also signals to safety officers that these cargoes require labeling for both chemical hazards and environmental risks. Moving D4 across borders involves compliance paperwork, so buyers and sellers both need accurate documentation about purity, batch number, container safety, and hazard classification. Mistakes here cost time and money, and regulators frequently update rules in response to environmental health research.
Anyone working with D4 needs to keep safety top of mind. While D4 doesn’t burn skin or corrode metal like strong acids, it still poses important health and environmental challenges. Recent studies link D4 to respiratory irritation after inhalation and possible liver changes if exposure runs high. Eco-concerns stem from D4’s persistence in the environment and its reported toxicity to aquatic life. High volatility means spills lead to quick evaporation, and any D4 vapors in a closed lab could hit flammable levels. Respirators, chemical splash goggles, and gloves stand as basic personal protective gear for people handling concentrated D4. If a spill occurs, absorbents like sand, clay, or commercial spill pads limit spread while keeping fumes low. Exhaust fans and fume hoods remain great investments in any setting where D4 gets used regularly. Storage away from direct sunlight and ignition sources keeps warehouse risks manageable. Long-haul trucking or shipping regulations often demand special labeling and documentation on external crates.
D4 serves as a raw material for many downstream products, especially in the silicone industry. When processed with special catalysts, those four siloxane rings open up and create long, flexible polymer chains that become sealants, medical tubes, insulating materials, and specialty lubricants. Cosmetic chemists value D4 for lending a silky texture to hair conditioners, deodorants, and skin lotions, though concerns about environmental impact push researchers to hunt for safer alternatives. Polymeric silicones made from D4 play a role in electronics as well, protecting delicate parts from heat and water. D4’s role as a starter molecule means that developments in its use and regulation ripple across multiple sectors: from manufacturers looking for pure and stable batches, to warehouse staff ensuring workplace safety, to consumers reading increasingly detailed labels on household products.
The world’s relationship with D4 highlights an ongoing push-and-pull between industry needs and environmental health. Rules across North America, Europe, and Asia shift constantly, creating a complex landscape for big producers. Efforts to curb exposure and release less D4 into rivers and lakes have led to investment in recycling systems and closed-loop manufacturing. Deploying efficient scrubbers and vapor recovery units helps limit fumes and reduce waste, protecting both workers and the environment. Product designers look for alternative ingredients where possible, but the unique properties of D4—like temperature resistance and lubricity—remain hard to replace. Continued investment in greener chemistry, smarter packaging, and transparent consumer communication stands as the real path to making D4 part of a responsible future supply chain.
