Copolymerization of acrylic acid to nylon-6 by trapped radicals—II: Liquid phase grafting and properties of copolymers

Initial rates of grafting, R_g, have been determined for film of nylon-6, which had been -,,-irradiated in vacuo and subsequently immersed in outgassed, aqueous, acrylic acid at 50'. Equilibrium swellings due to water and to monomer are attained rapidly by nylon-6 and give rise to a high R_g. During grafting a constant swelling due to water occurs immediately but the rate of uptake of monomer is less than R_g, These effects are discussed on the basis of compatibility. At a fixed equilibrium monomer concentration, [AA], in the film, R_g ∝ D^β where D is the dose and β = 0.94. At a fixed dose, R_g ∝ [AA]^α where α = 1.04. The value of β indicates mainly monomolecular termination by radical burial. This is postulated to occur by trapping of growing grafts in crystalline regions and/or transfer from them to such regions. By selectively dyeing and sectioning films of different degrees of grafting (DG), the progress of the grafting front inwards has been shown to follow closely the corresponding grafting curve of DG vs time. Grafting does not alter the moisture regain of nylon. Surface resistance and swelling in water change with DG, the effect being enhanced markedly by converting the grafts to their sodium salts.