Glycol Ethers, High-Purity Solvents

Propylene Glycol N-Butyl Ether (PNB)

Propylene Glycol n-Butyl Ether (PnB), identified by CAS number 5131-66-8, is a versatile, high-performance solvent belonging to the P-series glycol ether family. Chemically known as 1-butoxy-2-propanol (C₇H₁₆O₂), it is a clear, colorless liquid characterized by a mild, ethereal odor. PnB is highly valued in the chemical industry for its unique amphiphilic nature, which provides an exceptional balance between hydrophilic (water-loving) and lipophilic (oil-loving) properties. This makes it an outstanding coupling agent and solvent for both aqueous and organic systems.

Compared to traditional E-series (ethylene-based) glycol ethers, PnB offers a significantly more favorable toxicological profile, leading to its widespread adoption in consumer and industrial formulations where safety and environmental impact are prioritized. It is known for its excellent ability to reduce surface tension and its high solvency for a variety of resins, including acrylics, epoxies, and alkyds. Its moderate evaporation rate and chemical stability make it a cornerstone in modern coatings, cleaners, and specialty chemical applications.

Attributes

Key Features and Benefits

Superior Solvency: Demonstrates high solvency power for greases, oils, and numerous resin types, ensuring high-efficiency cleaning and uniform film formation.
Effective Coupling: Acts as a robust coupling agent, stabilizing mixtures of water and organic solvents that would otherwise remain immiscible.
Enhanced Wetting: Significantly reduces the surface tension of water-based formulations, improving the wetting and leveling capabilities on various substrates.
Low Toxicity: Provides a safer alternative to ethylene glycol ethers, featuring lower volatile organic compound (VOC) concerns and reduced health risks.
Evaporation Control: Offers a medium evaporation rate that optimizes the “open time” in coatings while ensuring timely drying.
Biodegradability: Readily biodegradable, supporting environmentally responsible and “green” formulation goals.

Specifications

Technical Highlights

Molecular Weight: 132.20 g/mol.
Boiling Point: 171°C (340°F) at 760 mmHg, providing stability under moderate thermal processing.
Flash Point: 63°C (145°F) (Pensky-Martens Closed Cup), categorizing it as a combustible liquid rather than highly flammable.
Vapor Pressure: Approximately 0.8 mmHg at 20°C, indicating low volatility and reduced inhalation exposure risk at ambient temperatures.
Solubility: Partially soluble in water (approx. 6.4% by weight at 20°C); completely miscible with a wide range of organic solvents including alcohols, ketones, and esters.
Specific Gravity: 0.880 at 20/20°C.
Viscosity: 3.1 cP at 25°C, contributing to low formulation viscosity.