Abstract
The grafting of acrylic acid (AA) and methacrylic acid (MAA) made poly (ethylene terephthalate) (PET) hydrophilic. The alkali-treatment of the grafted PET enhanced the hydrophilicity, transforming carboxyl groups into their Na-salt form. However, the use of natural water, which contained multi-valent metal ions, in the alkali-treatment of the grafted PET did not bring as high a hydrophilicity as expected. From model reactions in which aqueous CaCl2 solutions was used as media of the alkali-treatment, it became clear that the presence of Ca ions in the alkali-treatment suppressed transforming reaction of carboxyl groups of the grafted PET into the Na-salt form. It was suggested that gel formation of the grafted poly (AA/MAA) shut up the reactive sites, thus preventing transformation of carboxyl groups. The addition of a sequestering agent to the alkali-treating solution was useful in preventing multi-valent metal ion's effect and in bringing about smooth transformation of carboxyl groups into the Na-salt form.
