Abstract: The invention relates to a method for determining a composite material constitutive of moving parts in a hermetically sealed refrigerating compressor, wherein a composite material, of which the initial mechanical and thermal properties fulfull the conditions corresponding to the mechanical and thermal stresses in compressors, is placed during a first determined test period T1 in an environment containing the chemical products that are present in a compressor, at a test temperature equivalent to the maximal operating temperature of a compressor, and wherein at the end of this period, its chemical and mechanical properties are measured, and compared with the initial mechanical or chemical properties, and it is assessed by calculation what such properties would become once the material would have been used in an environment of a compressor during a second period T2, longer than the first test period T1, and wherein this material is thus utilized for producing parts provided the assessed properties satisfy the re