Propylene Glycol CAS 57‑55‑6

Frequently Asked Questions

Question 1: What are the main product characteristics of Propylene Glycol?

Propylene glycol is a clear, colorless, slightly syrupy liquid at room temperature, practically odorless and tasteless. It is a synthetic liquid substance that absorbs water, with excellent miscibility with water, acetone, and chloroform. Its molecular formula is C₃H₈O₂, MW 76.09, density approximately 1.038 g/cm³ (20 °C), boiling point 187.3 °C, melting point −60 °C, and refractive index 1.4326. It exhibits good viscosity and hygroscopicity, and is non-toxic, making it widely applicable across food, pharmaceutical, and cosmetic industries. The FDA has classified propylene glycol as an additive that is “generally recognized as safe” (GRAS) for use in food.

Question 2: What are the key features of Propylene Glycol compared with other glycols like ethylene glycol?

Propylene glycol shares similar antifreeze properties with ethylene glycol but offers significantly lower toxicity. While ethylene glycol breaks down into harmful crystals, propylene glycol does not form harmful crystals during metabolism and degrades rapidly in the body. It also degrades within several days to a week in water and soil, and about half of the propylene glycol entering the air breaks down within 24–50 hours, indicating favorable environmental compatibility. A major advantage is its FDA GRAS status, making it suitable for applications where leakage might lead to contact with food.

Question 3: What advantages does Propylene Glycol have for biological and pharmaceutical applications?

Propylene glycol has low toxicity to cells and enzymes, and is widely used as a solvent, solubilizer, and humectant in pharmaceutical formulations. It serves as an effective cryoprotectant (penetrating CPA) for cell and embryo cryopreservation, with studies showing that propylene glycol-based solutions yield high cell viability and proliferation after recovery. It is used in medicines to absorb extra water and maintain moisture, and serves as a solvent for food colors and flavors. It is also employed in cell lysis buffers and molecular biology applications.

Question 4: What should be noted when handling and storing Propylene Glycol?

Propylene glycol should be stored sealed at room temperature (2–30 °C) in a dry, dark environment, away from strong oxidizing agents and high temperatures. It is hygroscopic—keep containers tightly closed to prevent moisture absorption. When preparing aqueous solutions, dissolve in purified water with gentle mixing; no heating is required. Although generally regarded as low-toxicity, avoid prolonged skin contact and ensure proper ventilation during handling. Dispose of waste according to local environmental regulations.

Question 5: How does temperature affect the performance of Propylene Glycol?

Propylene glycol has excellent low-temperature performance with a freezing point of approximately −60 °C, making it highly effective as an antifreeze and deicing agent across a wide temperature range. Its viscosity increases at lower temperatures but remains manageable. For cryopreservation applications, propylene glycol-based solutions are typically used at concentrations of 2.5%–10% (v/v), with optimal cooling rates determined by the specific cell type. Its water solubility is complete and its solvency performance remains stable across typical storage and working temperatures.