The use of radiation-induced graft polymerization for modification of polymer track membranes

Track membranes (TM) made of poly(ethylene terephtalate) (PET) and polyprop ylene (PP) films have a number of peculiarities as compared with other ones . They have high mechanical strength at a low thickness, narrow pore size d istribution, low content of extractables. However, TM have some disadvantag es such as low chemical resistance in alkaline media (PET TM), the low wate r flow rate due to the hydrophobic nature of their surface. The use of radi ation-induced graft polymerization makes it possible to improve the basic c haracteristics of TM. In this communication our results on the modification of PET and PP TM are presented. The modified membranes were prepared by ra diation-induced graft polymerization from the liquid phase. Three methods o f grafting were used: (a) the direct method in argon atmosphere; (b) the pr e-irradiation of TM in air followed by grafting in argon atmosphere; (c) pr e-irradiation in vacuum followed by grafting in vacuum without contacting o xygen. The aim of the work was to investigate some properties of TM modifie d by grafted poly(methylvinyl pyridine) (PMVP) and poly(N-isopropylacrylami de) (PNI-PAAM). It was shown that the modification of TM with hydrophilic p olymer results in the growth of the water flow rate, In the past few years many works have been devoted to the synthesis of new polymers - the so-call ed "intelligent" materials - such as PNIPAAM. However, it is very difficult to make thin membranes of this polymer. Recently, it has been proposed to manufacture composite membranes by grafting stimulus-responsive polymers on to TM. Following this principle, we prepared thermosensitive membranes by t he radiation-induced graft polymerization of N-isopropylacrylamide (NIPAAM) onto PET TM. PET TM with the pore size of about 1 mu m and pore density of 10(6) cm(-2) were first inserted into a solution of NIPAAM containing inhi bitor of homopolymerization (CuCl2) and then exposed to the gamma-rays from a Co-60 source. The transport properties of the grafted TM were investigat ed. The permeation of water through the TM was controlled by temperature. T he grafted TM exhibited almost the same transition temperature (about 33 de grees C) as that of PNIPAAM, (C) 1999 Elsevier Science B.V. All rights rese rved.