Miscibility and stability of synthetic lubricants with HFC refrigerants

Wu, Weite; Thomas, Raymond H. P.

doi:10.1002/jsl.3000140202

Cited by 5 publications

(4 citation statements)

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“…In refrigeration, highly soluble lubricants are required for adequate lubricant return and to prevent fouling of the capillary tube and evaporator. 12 Very lipophilic hydrocarbon lubricants are generally highly miscible in CFCs and HCFCs. The same lubricants, however, are generally not compatible with the more polar HFAs.…”

Section: Introductionmentioning

confidence: 99%

“…However, the transition from CFCs and HCFCs to the more environmentally friendly HFAs has been somewhat problematic due in large extent to the significantly different solvent properties between these classes of fluids. In refrigeration, highly soluble lubricants are required for adequate lubricant return and to prevent fouling of the capillary tube and evaporator . Very lipophilic hydrocarbon lubricants are generally highly miscible in CFCs and HCFCs.…”

Section: Introductionmentioning

confidence: 99%

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Solvent−Solute Interactions in Hydrofluoroalkane Propellants

Peguin

Rocha

2008

J. Phys. Chem. B

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Understanding solvation in hydrofluoroalkane (HFA) propellants is of great importance for the development of novel pressurized metered-dose inhaler (pMDI) formulations. HFA-based pMDIs are not only the most widely used inhalation therapy devices for delivering small drug molecules to the respiratory tract, but they also hold promise as vehicles for the delivery of therapeutic biomolecules to and through the lungs. In this work we use binding energy calculations to determine the degree of interaction between HFA propellants and candidate HFA-philes, including a methyl-based tail (isohexane, ISO), and fragments of poly(ethylene oxide) (EO), poly(propylene oxide) (PO), and poly(lactide) (LA). The distinct nature of solvation forces of the two HFA propellants approved by the FDA for use in pMDIs, 1,1,1,2-tetrafluoroethane (HFA134a) and 1,1,1,2,3,3,3-heptafluoropropane (HFA227), is also studied. Binding energy (Ebst) calculations demonstrated that an increase in tail polarity through the addition of oxygen atoms in the fragment backbone provides for sites capable of interacting with the HFA propellant molecules, thus enhancing the stabilization energy of the complexes. The interaction energy between HFA227 and LA (EbHFA227-LA = -24.7 kJ.mol(-1)) is significantly more favorable than that between HFA227 and its hydrocarbon analog (EbHFA227-ISO = -10.0 kJ.mol(-1)). However, it was shown that not only the fragment polarity is of relevance in stabilizing the complexes. The accessibility of the oxygen atoms in the fragments of interest is also relevant. Cluster studies indicate that although both oxygen atoms in the LA fragment are available to form H-bonds with the propellant molecules, the ether oxygen in PO is accessible to only one propellant molecule, thus decreasing significantly the stabilization energy of the cluster. The results shown here serve as a guide for the design of novel HFA-philes for HFA-based pMDIs.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Solvent−Solute Interactions in Hydrofluoroalkane Propellants

Peguin

Rocha

2008

J. Phys. Chem. B

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“…In general, the stability of POEs and PAGs deteriorates with the presence of moisture (Wu, and Thomas, 1997). The POEs undergo a hydrolysis process, which is opposite to the esterification.…”

Section: Visual and Chemical Changes Are Possible Through The Chemicamentioning

confidence: 99%

“…POEs, manufactured with a higher percentage of branched acids, are more stable in the presence of water than those with a high proportion of linear acids. Wu, and Thomas (1997) reported that air as the contaminant usually has only a small effect on the stability of POEs. Contaminant metals, such as tin, must be avoided in refrigeration systems, since it is a catalyst for a chemical reaction between the refrigerant and lubricant.…”

Section: Visual and Chemical Changes Are Possible Through The Chemicamentioning

confidence: 99%

Investigation and analysis of lubricant effects on the performance of an HFC-134a refrigeration system

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This work was sponsored by the lubricant manufacturer, Henkel Corporation. Especially, I wish to thank Bruce Beimisch for his support and technical advice throughout the project. In addition, Mr. Nicholas Schnur was very cooperative and he greatly aided the completion of the project. Tecumseh Products was very generous in providing especially designed equipment. Particularly, Mr. Ronald Shimon was very helpful and supportive of the project.

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