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Different pulp samples were irradiated by three energy sources: plasma, electron beaming, and γ radiation. The effect of increased exposure to irradiation was studied by multidetector gel permeation chromatography with fluorescence labeling of carbonyl groups to quantify changes of the cellulose. Whereas plasma treatment had no effect, for gamma and electron beam the degradation primarily affects the high molar mass area. Kinetic calculations based on DPw were performed. They show close-to-linear relations with slopes in the same order of magnitude, suggesting that wood-derived pulps degrade slower than pulps from annual plants. The rise in carbonyl group content is linear with increasing dose. In particular, in pulps from annual plants, most detected carbonyl structures originate from the new reducing end groups. Therefore, oxidative modification of cellulose molecules by means of radiation appears to be viable for pulps produced from wood. Here the increase in oxidized functionalities is partially disconnected from chain scission.

The fibrillation tendencies of various cellulosic fibers in aqueous solution containing alkali metal hydroxide and ethanol were evaluated with two specific parameters: the critical point of fibrillation (CPF conc. ), that is a concentration of swelling agent where the fibrillation begins, and the ratio of initial increase in fibril number to increase in concentration of swelling agent (I i ). The CPF conc. and the I i are defined as fibrillation stability and fibrillation sensitivity to swelling agent, respectively. Lyocell fiber (CLY1) has the smallest CPF conc. and the largest I i , representing the lowest fibrillation stability and the highest fibrillation sensitivity, leading to the highest fibrillation tendency in CLY1 among the fibers tested. Although crosslinking improved fibrillation stability in lyocell as compared to modal, the fibrillation stability remained higher owing to the high water capacity and the high affinity for alkali. In alkali solution at the same concentration CLY1 fibrillation increased in the order of LiOH > NaOH > KOH. However, the plot of fibril number against solvent retention value of CLY1 in different alkaline solutions gives a slope of 110 count Á g/cm 3 regardless of alkali type, the critical degree of swelling for CLY1 with no fibrillation was 0.62 cm 3 /g in alkali solutions and 0.45 cm 3 /g in ethanol/water mixture.Nomenclature: W w -weight of fibers after centrifugation (g); W d -weight of fibers after drying (g); D alk. -density of alkaline solution (g/cm 3 ); ARV -solvent retention value in alkaline solution (cm 3 /g); WRVsolvent retention value in water (cm 3 /g); ERV -solvent retention value in ethanol/water mixture (cm 3 /g); I i -initial increase in fibril number (count Á l/mol); V p -pore volume (cm 3 /g); CPF conc. -critical point of fibrillation (mol/l)

Abstract:In this work, a supercritical carbon dioxide assembly was successfully constructed for dyeing Nylon6 fabric. Primary experiments were carried out to confirm the possibility of bringing the dyeing up to factory scale. A series of disperse azo dyes with potential antibacterial activity were applied to dye the fabric under our study in supercritical carbon dioxide (scCO2). The factors affecting the dyeing conditions (i.e., dye concentration, time, temperature and pressure) and functional properties were discussed and compared with those in aqueous dyeing. The comparison revealed that elimination of auxiliary chemicals such as salt, carrier or dispersing agent has no diverse effect on dyeing. The color strength of the dyed fabric evaluated by using K/S measurements increased by increasing dye concentration from 2% to 6% owf. (on weight of fabric). The nylon6 fabrics dyed in supercritical carbon dioxide have good fastness properties, and especially light fastness compared with conventional exhaustion dyeing. Antibacterial activity of the dyed samples under supercritical conditions was evaluated and the results showed excellent antibacterial efficiency.