Differences in Chemical Properties and Environmental Performance
- Toxicity Comparison: Ethylene glycol (C₂H₆O₂) exhibits significant toxicity, with ingestion of 5mL/kg sufficient to cause poisoning in adults (referencing WHO data), necessitating stringent protective measures. Propylene glycol (C₃H₈O₂) is a low-toxicity substance classified by the FDA as Generally Recognised as Safe (GRAS), suitable for use in the food and pharmaceutical industries.
- Biodegradability: Propylene glycol exhibits over 80% degradation rates in natural environments (EPA research), whereas ethylene glycol degrades slowly and may cause persistent aquatic pollution.
Physical Properties and Performance
- Thermal Conductivity: Ethylene glycol exhibits a thermal conductivity of 0.25 W/(m·K), outperforming propylene glycol's 0.20 W/(m·K), making it more suitable for high-power engine cooling.
- Freezing Point and Boiling Point:
50% ethylene glycol aqueous solution: Freezing point -37°C, boiling point 107°C;
A 50% propylene glycol aqueous solution has a freezing point of -34°C and a boiling point of 106°C (Source: SAE Standard J814). Propylene glycol tends to thicken and exhibit reduced flowability in extremely cold environments (e.g., below -40°C).
Application
- Ethylene glycol: Cost-sensitive applications with high cooling demands, such as conventional fuel vehicles and heavy-duty machinery;
- Propylene glycol: Fields with stringent environmental requirements, such as new energy vehicles and food processing equipment.
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