RAFT mediated grafting of poly(acrylic acid) (PAA) from polyethylene/polypropylene (PE/PP) nonwoven fabric via preirradiation

Nonwoven fabrics are porous materials with great potential for use in separation and purification of a large range of materials from metal ions to biomolecules after proper surface activation and modification. This work describes an activation process for polyethylene/polypropylene (PE/PP) nonwoven fabric by RAFT-mediated grafting of poly(acrylic acid) (PAA). The grafting mechanism relies on growing of PAA chains in a controlled manner after pretreatment of the PE/PP substrate by gamma irradiation under inert atmosphere. It was found that this process results in highly conformal and uniform PAA grafts on the surface and inside the matrix of PE/PP nonwoven fibers. The synthesized PE/PP-g-PAA copolymers were characterized by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, contact angle measurements and thermal analysis. The results of various techniques confirmed the existence of well-defined PAA chains in copolymer composition. The flowing behavior of water droplets through the fibers and measured contact angles revealed that surface features change significantly even at very low degree of PAA grafting.