Radioisotope testing of penetration of aggressive media in plastics under bending strain

Equipment is described for pressure tests of aggressive media penetration in plastics. Argon in a pressure cylinder with variable pressure control between 0 and 5 MPa is used for obtaining overpressure. Test chambers allow measuring the penetration of the medium under the action of pressure in the direction of penetration without deformation or with deformation of the plastics and pressure in the opposite direction. For the tests, samples of polyphenyl oxide (thickness 2 mm, overpressure 0.4 MPa), structural polyester elements (3 mm, 1 MPa) and acrylonitrile-butadiene-styrene copolymer (4 mm, 1.3 MPa) were used. The aggressive solution consisted of an aqueous solution of 35S-labelled H2SO4 of a concentration lower than 10-9% and specific activity of 2.3 MBq/ml. The samples were exposed for 6 days and layers were cut for autoradiography. The autoradiograms were evaluated photometrically. The equipment developed allows measuring the penetration of the aggressive medium in dependence on the overpressure strain of plastics. (J.C.)