u00b0 c for the treated pa 6 versus 110 u00b0 c for untreated pa 6 coefficient of linear expansion clte u201c coefficient of linear thermal expansion u201d 4 u00d7 10 u2212 5 u00b0 c versus 7 u00d7 10 u2212 5 u00b0 c finally the treated pa 6 has an improvement in the tensile strength of 10 relative to the untreated pa 6 these results demonstrate that the polyamide 6 treated by ion bombardment have improved mechanical and chemical properties in particular as regards the moisture resistance the resistance to stresses and the temperature resistance the parts are prepared by injection molding from a copolycarbonate of a blend of bisphenol a bpa and bisphenol trimethylcyclohexanone bptmc denoted hereinbelow as bp tmc 180 step 1 treatment by ion bombardment of helium ions with an energy received by the parts of 5 kev step 2 glow discharge with an air pressure of 5 u00d7 10 u2212 2 to 10 u2212 1 mbar over 120 s step 3 deposition of a layer of aluminum having a thickness of from 70 to 100 nm by pvd step 4 deposition by dc or ac pecvd of a polysiloxane layer having a mean thickness of 35 nm from a precursor such as.