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The Role of Diester and Polyol Esters in Refrigeration Oils
Classification: Company News
Apr 26,2026
The Role of Diester and Polyol Esters in Refrigeration Oils
Diesters are produced by the reaction of a dicarboxylic acid with a monohydric alcohol and have a relatively linear molecular structure.
Key advantages:
- Excellent low-temperature flow properties: extremely low pour point, ensuring smooth circulation within low-temperature evaporators.
- Good miscibility with HFCs: excellent compatibility with traditional HFC refrigerants such as R-134a.
- Cost-effectiveness: Offers a relative cost advantage amongst synthetic esters.
Limitations:
- Relatively moderate thermal/chemical stability: Long-term stability is inferior to polyol esters in environments above 100°C.
- Weaker hydrolytic stability: More sensitive to moisture.
Typical applications: Primarily used in domestic air conditioning and small-scale commercial refrigeration equipment operating under relatively mild conditions and utilising HFC refrigerants.
Polyol esters are produced by the reaction of polyols (such as pentaerythritol and trimethylolpropane) with monocarboxylic acids; their molecular structure is ‘star-shaped’, making them more compact and voluminous.
Core advantages and key functions:
- Excellent thermal and oxidative stability and chemical inertness: This is the fundamental reason for their widespread adoption. They can withstand the high temperatures at the compressor discharge end and coexist stably over the long term with refrigerants of varying chemical reactivity, such as HFCs and HFOs, without readily reacting to form acidic substances or deposits.
- Exceptional moisture absorption and hydrolytic stability: Although POE readily absorbs moisture, its molecular structure ‘locks in’ the water, slowing its corrosive effect on metals. Through refining processes and the addition of hydrolytic inhibitors, this impact can be effectively controlled.
- Outstanding lubricity and wear protection: Polar molecules provide a robust, adhesive oil film that protects bearings and scroll components, meeting the stringent reliability requirements of high-efficiency compressors.
- Excellent compatibility with new refrigerants: It is the only proven option for use with environmentally friendly HFOs (such as R-1234yf and R-1234ze) and the natural refrigerant CO₂.
Dominant applications: It dominates virtually all demanding application areas: automotive air conditioning (with R-134a and R-1234yf), commercial central air conditioning, commercial refrigeration systems using HFOs or CO₂, and industrial freezing equipment requiring long service life.
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