Judit Borsa

Swelling of carboxymethylated cellulose fibres

Swelling of cotton cellulose fibres having different proportions of carboxyl groups in the H-form was studied. The carboxyl groups were introduced by carboxymethylation under different reaction conditions. By studying the swelling of modified cellulose samples (water retention value of non-dried fibre) it was shown that the concentration of sodium hydroxide was the dominant factor among the investigated reaction parameters. The number of acidic groups was found to play a significant but not determinative role in the level of improvement in swelling caused by carboxymethylation. A linear correlation was observed between swelling and iodine sorption capacity. The degree of collapse of the highly accessible structure of cellulose during drying (hornification) was larger in the case of more accessible carboxymethylated fibres than for the alkali treated sample. The degree of hornification increased with growing swellability and with growing number of carboxyl groups in the investigated interval (40–120 mmol carboxyl/mol cellulose). This type of modified cellulosic fibre could be used for enhanced entrapping and release of chemicals.

The effect of tetramethylammonium hydroxide in comparison with the effect of sodium hydroxide on the slow pyrolysis of cellulose

Abstract The effect of two bases, tetramethylammonium hydroxide (TMAH) used in thermally assisted hydrolysis and methylation (THM) analysis of biopolymers and NaOH generally used in cellulose and textile industry, was compared in the pyrolysis of cotton cellulose at very low concentrations using differential thermal analysis, data obtained from thermogravimetry/mass spectrometry and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) to get more information about the reactive decomposition of cellulose. Highly purified cotton cellulose was impregnated with NaOH or TMAH to various weight levels up to 5%, immediately dried and pyrolysed in He atmosphere. The interaction with cellulose has a stabilizing effect on TMAH. Both bases decrease the temperature of the decomposition with increasing concentration, however, the decomposition patterns are different. The differences in the pyrolysis are enhanced by the methylating effect of TMAH.

Radiation activation of cotton-cellulose prior to alkali treatment

The effect of alkali treatment on preirradiated cotton-cellulose was investigated using diffuse reflectance Fourier transformed infrared spectroscopy (DRIFT) and X-ray diffraction (XRD). The effect of two kinds of alkali solutions (NaOH and TMAH, tetramethyl ammonium hydroxide) on the crystalline structure of irradiated cotton-cellulose was compared. The transformation of cellulose I to cellulose II was observed applying DRIFT technique by the increase of the absorbance at 896 cm-1 and XRD. The results obtained by the two methods were in good correlation. An increase in carbonyl content (as detected by FTIR by measuring the absorbance at 1740 cm-1) was found in the samples due to oxidative degradation.

Crystallinity and accessibility of fibrous carboxymethylcellulose by pad-roll technology

Statistically designed experiments have been made on partially carboxymethylated cotton fabric. The effect of the reaction parameters (concentration of sodium hydroxide and mono-chioroacetic acid and period of time) on the crystallinity (measured by x-ray diffraction), on the iodine sorption and on the disorder of amorphous fraction (calculated from iodine sorption capacity) are presented by polynomial models.

Fibrous carboxymethylcellulose by pad roll technology

Statistically designed experiments have been made using partial carboxymethylated cotton fabric. The effects of three reaction parameters (concentrations of sodium hy droxide and monochloroacetic acid and time period) on wet pickup and carboxyl content are presented using polynomial models. Monochloroacetic acid concentration seems to be the leading factor among the parameters investigated. Poor reproducibility of the drying process could be one possible barrier to industrial applications of car boxymethylation.

Effect of tetramethylammonium hydroxide on cotton cellulose compared to sodium hydroxide

Cotton fabric was treated with aqueous solutions of tetramethylammonium hydroxide (TMAH) and sodium hydroxide of various concentrations. The sorption of both chemicals, the specific weight of the fabric, the cellulose I - cellulose II transition, the BET surface area, the iodine sorption capacity, and the water retention value were measured and compared. Although less TMAH was adsorbed by cellulose than NaOH, the TMAH proved to be a more effective swelling agent for cellulose. The difference between their swelling effect starts to be significant at a concentration of about 2 mol.dm -3 .

Carboxymethylated cotton fabric for pesticide-protective work clothing

Cotton shirt weight print cloth is carboxymethylated using a pad-roll technology. Chemical accessibility is characterized by iodine sorption capacity and water retention; the values obtained for the modified cotton are significantly higher than those of the untreated and mercerized control samples. Layered clothing systems are made from combinations of treated and control fabrics, and pesticide penetration and retention are studied using radiolabeled methyl parathion. When the outer layer of the clothing sys tem is carboxymethylated, 30 to 45% more pesticide is trapped by that layer than when the outer layer is the untreated or the mercerized control fabric. Carboxymethylation reduces residual pesticide on the cotton fabric after laundering to less than half that observed for the control fabrics. Contamination of other clothes by redeposition during laundering is similar for the treated and untreated fabrics. The results of this study indicate that carboxymethylated fabrics may offer some protective advantages in re usable work clothing for pesticide handlers.

Effect of mild alkali/ultrasound treatment on flax and hemp fibres: the different responses of the two substrates

Flax and hemp fibres were treated by various combinations of water/diluted alkaline solution and stirring/ultrasound, respectively. Changes in the microstructure (scanning electron microscopy) and porous structure (low-temperature nitrogen adsorption), removal of non-cellulosic materials (weight loss, FTIR), mean fibre diameter, and adhesion of the polypropylene matrix to the fibres (micro-bond test) were investigated. For both types of fibres, removal of (FTIR) was observed. The fibre diameter of hemp was decreased by several treatments, most of all by stirring in alkali and subsequent sonication in water, while the ultrasound applied in alkali solution did not change the fibre fineness. This can be attributed to the dual effect of ultra-sonication: the swelling effect of alkali combined with ultrasound energy probably served the sticking of inter-fibrillar material rather than their dissolution. Fibre diameter of flax did not change in any circumstances. The porosity of hemp in the mesopore range increased, while that of flax decreased by alkali treatment and subsequent sonication. The reason for this difference might be the dissimilar cell wall structures of the two bast fibres, the high arabinose content of the hemp, and/or the cottonisation of hemp. No treatments altered the fibre-matrix adhesion measured by pulling out the fibre from a micro-droplet of polypropylene.