Polyoxyethylene (50) Stearate BP EP USP Pharma Grade — Properties, Structure, and Material Insights

What is Polyoxyethylene (50) Stearate BP EP USP Pharma Grade?

Polyoxyethylene (50) Stearate BP EP USP pharma grade brings together high purity standards and strict compliance with pharmacopeial requirements, making it a key material in pharmaceutical processes. As a non-ionic surfactant and emulsifier, it blends stearic acid with an average of 50 oxyethylene units. This compound appears as white to off-white solid flakes or pearly powder and delivers reliable results across various pharmaceutical applications. Its smooth solubility in water, alcohol, and many organic solvents sets it apart, enabling its use as a solubilizer, stabilizer, or emulsifier. The average molecular structure, with a backbone of ethylene oxide chains connected to a C18 fatty acid tail, supports its amphiphilic nature and performance as a surface-active agent in creams, ointments, tablets, and oral liquids.

Structure and Molecular Formula

The molecular composition can be represented by C₁₈H₃₅O₂(C₂H₄O)₅₀, holding a molecular weight around 2,700–3,000 g/mol. Each unit of polyoxyethylene features repeating -CH₂CH₂O- subunits, tethered to stearic acid through ester linkage. The structure keeps hydrophilic polyoxyethylene chains exposed, while the hydrophobic stearic acid part anchors itself in oil phases during emulsification. This dual behavior offers vital emulsification capacity and versatility, which accounts for its steady inclusion in pharmaceutical, cosmetic, and food formulations.

Specifications and Physical Properties

Polyoxyethylene (50) Stearate comes in multiple solid forms: waxy flakes, fine powder, crystalline pearls, and sometimes semi-solid or paste, according to storage and temperature. The typical melting point falls between 45°C and 53°C, confirming its adaptability for both room-temperature and warm-processing needs. Its density ranges from 1.06 to 1.11 g/cm³. Water solubility remains high, leading to clear, slightly viscous solutions in most applications. The compound usually lacks odor and offers a bland or neutral taste, which matters in oral dosage forms. Its refractive index, at 20°C, sits near 1.45, a number that reflects its capability for stable emulsification and transparency in final formulations. Specifications for BP, EP, and USP reflect upper limits on heavy metal content, acid value, saponification value, and moisture, confirming its suitability for essential medical uses.

HS Code and Raw Material

International trade for polyoxyethylene stearates most commonly uses HS Code 34021300, which captures non-ionic organic surface-active agents. The raw materials, mainly stearic acid sourced from either vegetable oils or animal fats, and ethylene oxide from petrochemical processes, determine the final material’s purity and reproducibility. This matters in the tightly regulated pharmaceutical sphere, where controlled synthesis and rigorous purification protect patient safety and product quality.

Density, State, and Solution Characteristics

As a solid at room temperature, polyoxyethylene (50) stearate holds its shape in flakes, grains, or fine powder, without hygroscopicity if stored dry. When poured into distilled water or compatible solvents, it produces stable colloidal solutions ready for further processing. The specific gravity stays just above 1, making it denser than water but easy to handle in bulk. When heated, the compound becomes a clear, viscous liquid—useful for rapid mixing, tablet granulation, or high-speed emulsification in creams and topical gels. For oral solutions, this material supports the even dispersion of active ingredients, and helps prevent sedimentation or creaming over shelf life.

Compatibility, Safety, and Chemical Nature

Structurally stable, polyoxyethylene (50) stearate remains inert and non-reactive under non-extreme conditions, without hazardous byproducts. No acute toxicity appears at common use levels, and the pharma grade version passes residue and heavy metals testing. Direct skin or eye contact may occasionally cause irritation in highly sensitive individuals, emphasizing care in powder handling with gloves and eyewear. The compound does not count as hazardous under normal transportation or storage regulations. During synthesis, ethylene oxide poses safety considerations, but these risks never carry over to the finished, purified end product. In pharmaceutical settings, it aligns with excipient standards for oral, dermal, and parenteral applications. The breakdown products—polyethylene glycol chains and stearic acid metabolites—hold a long track record of safe use worldwide.

Harmful Effects, Handling, and Environmental Impact

Polyoxyethylene (50) stearate poses low risk to human health and the wider environment when managed by recommended protocols. Chronic or high-dose exposure has not been linked to carcinogenic or mutagenic effects to date. For workers, proper industrial hygiene such as dust extraction and PPE prevents respiratory irritation or nuisance. Its raw material supply chain remains under ongoing scrutiny to support sustainability: plant-sourced stearic acid and advanced purification for ethylene oxide lead to a cleaner, more responsible final product. Disposal protocols ask for dilution and integration into municipal waste streams, with low aquatic toxicity reported in environmental fate studies conducted over the past decade. Fire risk is negligible in storage and shipment, with no self-sustaining combustion potential. The shelf life generally extends from 24 to 36 months in sealed, light-protected containers, provided moisture and heat extremes are avoided.

Possible Solutions and Improvements for Pharmaceutical Use

Based on field experience, improving traceability for stearic acid and ethylene oxide input helps enhance overall excipient quality. Suppliers who certify origin and production pathways can better assure compliance for global pharma manufacturing. End users often want granular testing data on residual ethylene oxide, dioxane, and other contaminants, which can be addressed by setting up partnerships with accredited analytical labs. In formulation, ongoing research into particle size distribution of the material may uncover new benefits for faster dissolving oral dosage forms or easier blending in low-shear industrial mixers. Green chemistry advances, such as biobased ethylene oxide and circular-economy stearic acid sourcing, could help reduce the environmental load, making Polyoxyethylene (50) Stearate an even cleaner excipient choice in the future.