The role of certain cations as homopolymer inhibitors in the direct radiation grafting of acrylic acid to nylon-6 fabric was investigated. The grafting solution was methanol and water at a ratio of 30 : 70 ~01%. The maximum graft yield was obtained at 0.08 wt% when using Fez+ and at 0.7% for Fe3+. In addition, the graft yield obtained with the latter ion was higher than that for the former. Moreover, the presence of Na+ and K' salts in concentrations as low as 0.1 wt% caused an increase in the graft yield. The hydrophilic properties investigated indicated that the water absorption of nylon-6 fabric after 9 days increased by 44 times after grafting with poly(acry1ic acid) at 166% graft yield. This ratio became 123 times, when this graft copolymer was transformed to the sodium salt. These ratios became 105 and 490 times for the corresponding recrystallized forms, respectively. A study was made to gain a better understanding of the observed super water absorption using SEM and DSC analysis. SEM micrographs of the recrystallized copolymer indicated the formation of large pores with a dendritic structure. Moreover, DSC showed a decrease in both the heat of fusion and melting point. The grafted nylon-6 fabric showed a noticeable affinity for different dyestuffs.
A. M. El-Naggar et al.The morphological structure of the graft copolymer of nylon-6 and its recrystallized form was also investigated. Some hydrophilic properties such as moisture and water regain, as well as super water absorption, were evaluated.
EXPERIMENTAL
MaterialsNylon-6 fabric. This was a knit weave type (84g/cm2) obtained from Middetex Company, Cairo, Egypt. It was scoured, hydrogen peroxide bleached and was not subjected to a finishing process. Before use, it was washed with a solution containing 5 g/litre Na,CO, and 1% of a non-ionic wetting agent (Sandopan) to remove any undesired materials, which may affect the grafting reaction.Dyestufs. Solar Orange (direct dye), Sandocryl Red B6B (basic dye), Levafix Brilliant Red E-4BA (reactive dye) and Samaron Blue FBL (disperse dye); the first two dyes were kindly supplied by Sandoz, Switzerland, while the third and fourth were from Bayer and Hoechst, Germany, respectively.
Monomer and chemicals.Acrylic acid was of purity 99% (Merck, Germany) and was used as received. The other solvents and chemicals were of pure grade and were used without further purification.
MethodsGrafting procedure. The direct radiation grafting method was used in the presence of air; the nylon-6 substrates were placed in contact with the grafting solution. The different additives, such as metal salts, were added to the grafting solution, which was then exposed to gamma radiation. Irradiation was carried out at a dose rate of 0.5-0.45 Mrad/h in the cobalt-60 gamma source (made in India) of the National Center for Radiation Research and Technology, Cairo, Egypt. The grafted nylon-6 substrates were washed thoroughly with hot distilled water to remove unreacted monomer and surface homopolymer. Then the grafted substrates were extracted in...
