Attachment of sulfonic acid groups to various shapes of polyethylene, polypropylene and polytetrafluoroethylene by radiation-induced graft polymerization

Sulfonic acid (SO₃H) groups were attached to four different polymeric substrates by means of cografting sodium styrene sulfonate (SSS) with acrylic acid (AAc). The polymeric substrates were: microporous polyethylene (PE) hollow-fiber membrane, polypropylene (PP) tube, non-woven fabric made from PE and PP, and polytetrafluoroethylene (PTFE) film. The polymers were pre-irradiated by means of an electron beam source and immersed into monomer mixtures of SSS and AAc at 323 K. The molar ratio of the sulfonic acid groups to carboxyl (COOH) groups in the grafted polymers increased with reaction time. The salt-splitting capacities of the resultant ion exchangers, after 20 h of reaction, were 2.5, 1.4, 1.6 and 1.1 mol/kg for hollow fiber, tube, non-woven fabric and film, respectively. These values are in the range of salt-splitting capacities characteristic for conventional cation exchangers based on styrene-divinyl benzene copolymer beads.