Butoxypolypropylene Glycol 400—sometimes listed in import and export documents under HS Code 3907.20—dropps into the category of synthetic polyethers. Chemists put it together using polypropylene glycol chains and butoxy groups. The formula reflects a repeating unit of C3H6O, with a butoxy anchor at one end. Standard grade falls near a molecular weight of 400 g/mol, and the presence of ether linkages means it blends flexibility with limited reactivity. This polymer finds friendship among materials that need a gentle touch and stable base. Rather than stemming from textiles or natural oil, production uses chemical raw materials—so manufacturers can tweak its properties by adjusting chain lengths and the butoxy content.
Look at it in a drum: Butoxypolypropylene Glycol 400 usually flows as a clear, colorless to pale yellow liquid. Relatively thick but not too sticky, viscosity changes with temperature, which often matters a lot in actual use. Specific gravity hovers around 1.01 at 25°C, just above the density of water. Pour it out, and you might catch a faint odor—not strong enough to demand respirators under normal use, yet enough to set this apart from odorless glycols. You won’t consistently find it as flakes, powder, solid, pearls, or crystals; those forms don’t take. This polyether only lands as a liquid because its structure stops molecules from lining up tightly at room temperature, so it resists freezing or crystallizing unless cooled much further. Suppliers may offer it in bulk, drums, carboys, or totes, sometimes diluted into solution depending on the downstream process.
Each molecule carries a butoxy (–O–C4H9) group at one end, the same kind that you might see in some surfactants or specialty solvents. The backbone consists of repeating propylene oxide units—(–CH2–CHOH–CH3–)—which create space and flexibility, letting the chain bend and move. Chains stop growing at around 400 units total molecular mass, which defines this grade. Unlike linear polymers, its branching pattern prevents solidification and creates that signature oily texture. Such polyether structure lends itself to compatibility with all sorts of hydrophobic and hydrophilic substances. In practice, the balance between butoxy and glycol functions lets chemists design materials tailored to diverse industrial uses.
Ask any supplier and they will probably talk through numbers. Specific gravity, as mentioned, sits close to 1.01 or just above water. Viscosity runs around 80 to 120 mPa·s (at 25°C), giving it that syrupy pour. Water solubility falls on the low side, especially compared to polyethylene glycols, meaning it tends to separate rather than dissolve. The refractive index shows modest light bending, a sign of the hydrocarbon backbone. Boiling point usually exceeds 200°C, with a flashpoint just north of 170°C, suggesting it will not ignite easily in ordinary settings. In chemical terms, it’s classed as a polyether but also as an alcohol by function due to terminal hydroxyl groups, which participate in certain reactions.
Each batch contains molecules varying slightly in size, but their close range means predictable performance. Its mild polarity helps it serve as a bridge between water-based and oil-based systems. Hydrophobic enough to resist quick breakdown, hydrophilic enough to wet surfaces, Butoxypolypropylene Glycol 400 opens doors in both formula types. Surface tension measures lower than water’s, which translates to better spreading and mixing in complex material blends. Volatility measures low, so open containers don’t evaporate much—even over several days in lab or factory conditions. Chemical resistance matches expectations for polyethers: resilient against acids and bases, but heat or strong oxidation can eventually break it down. I’ve seen it sit happily in both stainless and polyolefin tanks without color change or texture shift.
See this chemical show up in lubricant formulations that need thickening without tackiness. Its structure fits right into specialized hydraulic fluids and as a carrier for dyes or stabilizers. I’ve known factory teams to add it into polyurethane dispersions for better flow, or as a plasticizer where flexibility matters. That same backbone lets it act as a surfactant precursor, or a humectant in anti-static or anti-fog coatings. Unlike water-heavy glycols, Butoxypolypropylene Glycol 400 sticks around longer on surfaces, meaning less reapplication in practical use. Because it resists both high- and low-pH conditions, I’ve seen it play a role as a buffer material in adhesives and coatings.
Factories and labs look at the safety sheet to see: Butoxypolypropylene Glycol 400 doesn’t count as acutely hazardous or highly flammable, and the mild odor rarely triggers complaints. Skin contact on bare hands may cause dryness or mild irritation after a day’s work, yet it lacks the aggressive bite of harsher solvents. Inhalation of mists causes some coughing, but the high boiling point means vapor stays low. Wastewater concerns center on biological oxygen demand, typical of organic chemicals, so plants capture and treat runoff before discharge. Because it’s not classified as a major environmental hazard, safe disposal often aligns with local protocols for non-hazardous industrial chemicals. I have never seen a chemical emergency response triggered by a spill in regular use; a mop and detergent usually suffice. Gloves and goggles reduce exposure, and ventilation matters most in confined areas.
Despite its relative safety, overexposure or improper disposal can still create problems. Long-term skin contact or high-concentration spills might cause dermatitis in sensitive workers. No established carcinogenicity, but breakdown products under high heat or fire conditions—carbon monoxide, carbon dioxide—add risk in crowded workspaces. In confined drains or water bodies, large quantities challenge bacteria, so responsible users track volumes and direct disposal. Regulatory guidance lands below the stricter lines set for phenols or phthalates, but the best practice chooses caution: avoid open drains and limit unnecessary exposure. Safe storage uses labeled drums under a roof, away from acids or oxidizers.
Production starts from propylene oxide—a petroleum derivative—reacted with butanol and a catalyst. Plants tune the chain length by adjusting flow rates and reaction times, keeping molecular weight tightly within spec. This sort of control gives producers the chance to meet rigorous industrial or pharmaceutical standards. Raw materials feed into reactors that keep water and air away, since moisture disrupts the process. Plants then strip out residual butanol and unreacted monomer, using vacuum and heat. Quality assurance checks every batch for molecular weight, residual solvents, and clarity, since haze or off-odor means a process slip or contamination.
Anyone who works with specialty polymers knows the details make the difference. An ordinary glycol, or the wrong chain length, just wouldn’t serve the same way in many applications. Making the right choice depends on reading technical sheets, understanding the structure, and seeing where the material meets a real-world need—whether as a lubricant ingredient, a flexible additive, or a building block for surfactants. The chemical, the process, and the handling steps all blend into a single story where reliable, well-specified material lets the industry move forward—safer, steadier, and smarter.
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