SynopsisPermeant degradation affects the brittleness, flexural fatigue, and .ultimate tensile properties of polyester fibers more drastically than topochemical degradation. Topochemical degradation was obtained by hydrolysis with aqueous NaOH and permeant degradation by aminolysis with aqueous ethylamine. Treatment with aqueous sodium hydroxide appears to leave the polyester fiber surfaces more resistant to abrasion damage.
SYNOPSISBoth sodium hydroxide solution of mercerizing strength and anhydrous methylamine are suitable pretreatments for enhancing the reactivity of cotton cellulose. Favorable results are achieved by maintaining the fiber material in the never-dried state after the swelling treatment. Extraction by organic solvents is to be preferred over water-washing in order to remove the swelling agent. When cotton is swollen with either aqueous sodium hydroxide or anhydrous methylamine and then washed and dried, its crystallinity, as determined by X-ray diffraction is not lowered as much as it is if it is acetylated to an acetyl content of about 9% before drying. The greatest modifications of the crystal structure of cotton were found on methylamine treatment followed by chloroform and pyridine washing and acetylation in the never-dried state (MeCP product), as well as by alcoholic mercerization followed by ethanol and pyridine washing and acetylation in the never-dried state (AMEP) .As determined by moisture regains, no significant differences are apparent between the accessibility of samples of low acetyl content (ca. 9% ) prepared by either the AMEP or by the MeCP treatment. The DTA curves of methylamine-treated cotton with an acetyl content close to that of commercial diacetate and the commercial product are dissimilar. It can be concluded from the DTA curve of the deacetylated product prepared from this MeCP sample that it has a highly disordered structure. The tensile properties of the acetylated products of low acetyl content are considerably improved if acetylation is preceded by mercerization with subsequent solvent exchange, and less so if it is preceded by methylamine followed by solvent exchange. Incorporation of acetyl groups significantly enhances the breaking strength and extensibility of mercerized solvent-washed materials.
Cotton, linen, ramie, and viscose rayon fabrics along with a cotton / linen blend were hydrolyzed with cellulase from Trichoderma viride. Surface fibrils were eliminated by a 6 hour treatment in all cases. The loss of fibrillar matter appeared to be the primary cause of weight loss at this stage. On prolonged treatment, cotton, linen, and viscose rayon lost weight at a faster rate than ramie and the cotton / linen blend. The fall in yam strength was progressive with increasing weight loss for cotton and viscose, while for linen and ramie it was slight initially and then increased sharply. Retention of strength after 48 hours' incubation time increased in the order viscose rayon << cotton < ramie < linen, whereas weight loss increased in the order ramie < linen < cotton < viscose rayon. X-ray crystallinity and moisture sorption of the samples did not change after the treatment, indicating that the mechanism of endwise attack of the cellulase at accessiblc cellulose chains on crystallite surfaces appeared to apply to all four fibers. The location of enzymatic attack could be monitored with a light microscope using Congo red staining in the case of cotton and linen, but not ramie or rayon. Changes in surface morphology could be followed for all the enzyme-treated fibers by scanning electron microscopy. Additionally, mechanical tests demonstrated the changes in stretchability and stiffness of the fabrics and the mobility of yams within the samples.
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