THE USE OF ALKALINE-BUFFERING AGENTS TO RETARD THE DEGRADATION OF COTTON TEXTILES.

摘要

When cotton textiles deteriorate with age they become acidic, yellowed and weakened. Although the lifetime of paper can be extended by deacidification, the response of cotton fabrics to such treatments in unknown. The main objective of this research was to determine whether three alkaline buffers, useful in paper conservation, would reduce the degradation of cotton fabric during accelerated aging. Two of the alkaline buffers selected, calcium hydroxide and magnesium bicarbonate, are prepared as aqueous solutions; the third buffer, methoxy magnesium methyl carbonate (MMMC) (trade name, Wei T'o('(REGTM))) is applied from a fluorocarbon solvent. Desized scoured cotton fabrics treated with each buffer were aged at 100(DEGREES)C and 100% R.H. in a closed atmosphere of oxygen or nitrogren for 25 days. Degradation was assessed at intervals by measuring the change in fabric color and tensile strength, aqueous-extract pH, intrinsic viscosity, degree of polymerization (D.P.), carbonyl, carboxyl, aldehyde and ketone content.;The pH of unbuffered cotton fell to 4.8 after 15 days of aging, however, that of the alkaline-buffered specimens did not fall below 7.0. Acidity in aged cotton is related to the formation of carboxyl groups in the cellulose. The carboxyl content decreased rather than increased with time, likely due to the decomposition of carboxyls by heat and moisture in the aging chamber.;Loss in fabric tensile strength and decrease in D.P. were evidence of hydrolytic degradation. Unbuffered cotton lost strength at a rate of 4.5%/day, compared to a decrease of 1.5 to 2.1%/day for buffered cottons. The D.P. of unbuffered cotton fell to 15% of its original value while buffered cottons had D.P.'s of 40 to 60% of the original value.;All three buffers provide cotton fabric with protection against the conditions encountered during accelerated aging. The unbuffered control fabric exhibited a color change twice as great as the buffered specimens. Color change is generally associated with the formation of aldehyde and ketone groups. The buffered cottons which showed the least color change also had the lowest carbonyl content, the most effective buffer (MMMC) reducing the rate of oxidation by a factor of 4.