Effects of CFC and HFC refrigerants and ester lubricants on polyester insulation materials

Three polyester motor insulation films-"standard" poly ethylene terephthlate (PET), "low oligomer" PET, and poly ethylene naphthalate (PEN)-have been examined for compatibility with a range of ozone benign HFC refrigerants and mixed acid polyolester lubricants. The results indicate that the R134a/ester lubricant mixture is considerably more aggressive in terms of oligomer extraction than CFC 12/mineral oil standard refrigerant/lubricant mixtures. However, low oligomer PET film shows similar behavior in R12, R22 or R134a systems. In addition, specially designed low oligomer PET film is shown to give significant improvements in thermal ageing and resistance to hydrolytic degradation compared to standard PET film. High performance PEN film shows improvement in oligomer extraction, thermal stability and hydrolytic stability when compared to either PET film.