Pergamon Radiation Me.aauremeats, Vol. 25, Nos I--4, pp. 729-732, 1995 Copyright 0 1995 Elsevier Science LU;I Printed in Or~ Britai~ All dglm rcm.v~ 13~D5 $9..50 + .00 13~.4487(95)00233-2 THE PROPERTIES AND POROUS STRUCTURE OF POLYPROPYLENE TRACK MEMBRANES L. I. KRAVETS, S. N. DM1TRIEV and P. Yu. APEL Joint Institute for Nuclear Research, Dubna, Russia ABSTRACT In this report the results of the developing polypropylene track membranes (PPTMs) fabrication method providing improved structurul and chemical membrane properties are presented. New PPTMs are characterized by high homogeneity of pore sizes, high mechanical strength, increased heat resistance and the resistance against aggresive media. KEYWORDS Track membrane, polypropylene, chemical etching, sensibilization, selectivity of etching, hyd- rophobic. INTRODUCTION At the Flerov Laboratory of Nuclear Reactions (JINR) track membranes on the basis of chemically stable material polypropylene (PP) have been developed. The method of obtaining polypropylene TMs (Apel et al., 1990, Apel et al., 1992) consists of a procedure in which a film irradiated by high energy heavy charged particles is subjected to chemical etching in chromium-VI solution. A thick oxidized polymer layer is prodused as a result of PP film irradiation and chemical etching. Such a layer contains many radicals of hydroperoxides causing destruction processes in the film. Moreover, the compounds of chromium are being adsorbed PP membrane surface which can not be able removed completely by consequent washing of the membrane in water. The adsorbed compounds as well as oxidized surface layer significantly reduces the advantages of the membrane obtained. Due to this fact the development of PPTMs improved characteristics is still a problem up to now. In this report the results of the developing polypropylene track membranes fabrication method providing improved structurul and membrane properties are presented. EXPERIMENTAL Biaxialy oriented polypropylene films "Torayfan" (Japan) thickness 10 #m was used for manufac- turing membranes. Film samples were irradiated in vacuum accelerated krypton and xenon ions with the energy 1 Mev/a.u.m. Ion fluence varied between 10 6 and 2.108 cm -2. The irradiation was performed using the U-400 cyclotron. The following methods of investigation of PPTMs were being used: the conductometry during the etching, the measurement of the air flow rate, the measurement of the pressure which breaks an unsupported membrane), the measurements of water contact angle. Samples structure has been scanned under the "JSM-840" electron microscope. Distributions on pore sizes have been measured with the help of the "Coulter II" porometer. RESULTS The procedure of the polypropylene track membranes preparation includes a few stages: ~.2s:1/*-~ 729