Physical Properties of Dibutyl Phthalate
The physical properties of dibutyl phthalate (DBP) exhibit distinct and stable characteristics, providing a clear reference basis for its application and storage. At room temperature and pressure, DBP is a colorless to light yellow transparent oily liquid with no obvious irritating odor, uniform color, no turbidity, no precipitation, no mechanical impurities, and good fluidity. Its boiling point and melting point are important physical parameters. The boiling point of pure DBP is 340℃. When heated to boiling point at standard atmospheric pressure, it will slowly evaporate without obvious decomposition phenomenon. The melting point is -35℃, and it is not easy to solidify at low temperatures. Even at low temperatures of -20℃, it can still maintain an oily liquid state. This characteristic makes it suitable for low-temperature processing scenarios, and it will not cause system solidification or decreased fluidity due to low temperatures.
In terms of density and viscosity, DBP has a density of 1.045-1.050g/cm³ (25℃), slightly higher than water and similar to the density of most organic solvents, making it easy to mix evenly with polymers and solvents. The viscosity is 16-20mPa·s (25℃), which is moderate and can ensure rapid diffusion into the polymer molecular chain during processing, without causing rapid volatilization loss due to low viscosity. As the temperature increases, its viscosity significantly decreases. For example, at 80°C, the viscosity drops to 5-8 mPa·s, a property that facilitates mixing and dispersion during high-temperature processing. The viscosity increases as the temperature decreases, reaching over 100 mPa·s at 0°C, yet it remains in a flow state without solidification.
In terms of solubility, dibutyl phthalate exhibits typical ester compound characteristics, with solubility closely related to the polarity of solvents, and it possesses both hydrophobicity and a certain degree of polar compatibility. It is easily soluble in the vast majority of organic solvents. In these solvents, they can be mixed in any proportion to form a uniform and transparent solution without layering or precipitation. For example, at 25 ℃, the solubility of DBP in toluene is infinitely miscible. Its solubility in ethanol can reach over 50g/100mL, and its solubility in n-hexane is about 30g/100mL. On the contrary, DBP is difficult to dissolve in water, with only 0.001-0.002 grams dissolved per 100 grams of water at room temperature, making it almost insoluble in water. This characteristic limits its application in water-based systems and also avoids performance loss caused by dissolution in humid environments. In addition, its solubility is less affected by temperature, and the effect of increasing temperature on solubility is not significant. This characteristic ensures that its mixing stability with solvents and polymers remains consistent at different processing temperatures.