Abstract
The treatments of acrylic acid grafted polypropylene fabrics with metallic salts were examined in relation to the textile properties such as hygroscopic property and thermooxidative stability.
Carboxylic groups of the acrylic acid grafted polypropylene fabrics were converted to sodium salts with sodium carbonate or sodium acetate. Then, a portion of each treated fabrics was further treated with calcium acetate so that sodium carboxylates in the fabrics were altered to calcium salts.
It was found from the infrared absorption spectra and moisture regain of these four kinds of fabrics that the degree of conversion to the corresponding salt-forms and moisture regain are more increased by using sodium carbonate in the first step of the treatment than by using sodium acetate.
The thermooxidative stability of calcium and zinc salts of acrylic acid grafted polypropylene fabrics, which have already been reported to have better stability than the grafted fabrics untreated or treated with other inorganic metals, is also improved when sodium carbonate was used in the first step compared to the use of sodium acetate. These results are explained if the conversion of the carboxyl group in the fabrics to other salt-forms is considered.
When sodium carbonate was used in the first step, further attempts were made to increase the conversion with increasing concentration of the metallic salt in the treating solutions as well as longer period of reaction time. As the result, it is suggested that the thermooxidative stabilities of the grafted fabrics in the forms of calcium or zinc salts are very sensitive to small changes of conversion even in a high degree of conversion, but the moisture regains of those, including sodium salt-form, are rather insensitive to them at a higher level.
It may be concluded from this study that in the chemical modification of fibers by the graft copolymerization with acid group containing monomers such as acrylic acid and aftertreatment with metallic salts, the degree of conversion of carboxylic groups in the grafted fibers to suitable metallic salt-forms are very important.
