David M. Cates

A spectrophotometric investigation of the yellow color that accompanies the formation of furan derivatives in degraded-sugar solutions

Abstract The nature of the yellow color that accompanies the degradation of sugars was investigated by studying the spectral characteristics of the tail-end absorption of yellow samples of 5-(hydroxymethyl)-2-furaldehyde (HMF) and 2-furaldehyde. The spectra of these furan derivatives were compared to those of the parent furan and of colorless benzaldehyde. The results obtained led to the conclusion that the yellow color is due to the formation of y -unsaturated, dicarbonyl compounds during decomposition; the yellow color associated with these dicarbonyl compounds comes from the extension of their minor, broad absorption bands into the violet region of the visible spectrum. These broad bands are hidden under the intense absorption of the carbonyl groups of the unreacted, parent compounds. Thus, the tail-end absorption at the long-wavelength end of the spectra of HMF and 2-furaldehyde belongs to the hidden band.

2,2î-Bipyridine Catalyzed Bleaching of Cotton Fibers with Peracetic Acid Part I: Kinetics and Mechanism of Peracetic Acid Decomposition in the Bleach Solution

Peracetic acid can be catalyzed to bleach cotton fibers at temperatures as low as 30°C by incorporating 2,2î-bipyridine in the bleach solution if the appropriate concentration of ferrous ions is present in the cotton fibers. The tris-2,2î-bipyridine ferrous ion complex (trischelate) is the catalytically active species, and sodium lauryl sulfate functions as a stabilizer for the peracid in the presence of the trischelate. The effects of pH, temperature, and concentrations of 2,2î-bipyridine, sodium lauryl sulfate, and ferrous ions on the kinetics and mechanism of peracetic acid decomposition have been investigated. Peracetic acid decomposition in the bleach solution is due mainly to alkaline hydrolysis without added ferrous ions and catalysis by the trischelate complex in solutions containing added ferrous ions. Overall decomposition follows the rate expression where k 1 is the specific rate constant for alkaline hydrolysis and k 3 is the specific rate constant for catalytic decomposition by the trischelate in the presence of sodium lauryl sulfate.

Sorption and Transport Properties of Solvent-Treated Poly(ethylene Terephthalate) Fibers Using Disperse Dyes as Molecular Probes

PET can be prepared by solvent and heat treatment in widely differing structures as shown by the sorption and transport properties. The order of elution of a pair of solutes on poly(ethylene terephthalate) fibers as chromatographic substrate can be reversed, and the dominant mechanism of solute dispersion changed, through struc tural changes brought about by solvent and heat treatment.

2,2î-Bipyridine Catalyzed Bleaching of Cotton Fibers with Peracetic Acid Part II: Bleaching Mechanism

Peracetic acid can be catalyzed to bleach cotton fibers at temperatures as low as 30°C by incorporating 2,2î-bipyridine in the bleach solution. Treatment of the fibers with HCl prior to bleaching reduces bleaching effectiveness by removing trace transition metal ions from the fibers. Sorption of individual ions (Cr+3 Mn+2, Fe+2, Fe+3 Co+2, Ni+2, Cu+2, and Zn+2) by HCl treated cotton fibers prior to bleaching indicates that the ferrous ion produces the greatest catalytic effect, and it is only effective when the metal ion is in the fiber as opposed to in solution. Ferrous ions in the fibers sorb 2,2î-bipyridine from solution to form the tris-2,2î-bipyridine ferrous ion complex that is associated with the fibers, and it is the trischelate associated with the fibers that catalyzes bleaching. The effects of pH, temperature, and concentrations of 2,2î-bipyridine, sodium lauryl sulfate, and transition metal ions (in the fibers and in solution) on bleaching effectiveness and peracetic acid decomposition have been studied, and a bleaching mechanism is proposed.

Abnormal Densities Obtained by Liquid Crystallization of Thin Poly(Ethylene Terephthalate) Films

Whén poly(ethylene terephthalate) films arc crystallized by certain liquids, thin films exhibit abnormally low densities, in contrast to thick films which have the densities of semicrystalline polymer. Cavitation produced by the crystallizing liquid is considered responsible. Although thick films also undergo cavitation, any lasting effect is confined to the surface; the influence on density is not detected because the cavitated structure represents a relatively small fraction of the total film.

The Effect of Certain Variables in Warp Sizing on Weavability

The effect of certain variables (size add-on, degree of polymerization of size, and temperature of application) in sizing was determined in relation to simulated weaving for a cotton yarn sized with poly(ethylene oxide). Increasing the size add-on decreased the tendency of the sized yarns to shed fibers and size. The effect of resin DP varied with size add-on. At low add-ons an increase in DP was accompanied by an improvement in weavability which was attributed to the concomitant increase in toughness of the resin; after very high values of DP were reached, however, weaving became unsatisfactory, apparently because of poor anchoring of resin to yarn. At high add-ons an increase in resin DP resulted in improved weaving performance for all ranges of DP, and this effect was attributed both to the increase in toughness of the resin film and to the increase in film coverage of the yarn surface and in film thickness achieved at high add-ons. As the temperature of application was raised, penetration of size through yarn increased. This resulted in poor weavability at low DPs; at high DPs, however, weavability was improved, apparently because the increase in temperature permitted better anchoring of size to yarn.

The Stabilizer in Hydrogen Peroxide Bleaching

Stabilize drogen peroxide decomposed at a slower rate than unstabilized peroxide and, for a given amount of decomposition in the presence of cellulose fabric, was more effective in raising reflectance and causing chemical damage. The ratio of reflectance to reduction of viscosity, however, was the same, suggesting that damage to cellulose is unavoidable and related to the amount of colored impurities destroyed. This ratio is dependent on the history of the fiber.

Evaluation of Annealed Poly(ethylene Terephthalate) Structures by Gas Chromatography

Solvent-crystallized, ground PET fibers were used in a gas chromatographic column as the stationary phase and subjected in situ to increasingly severe thermal treatment. After each treatment, an homologous series of hydrocarbons was passed through the column as molecular probes. After an initial reduction in surface sonption that was produced by heat treatment at 145°C, no further change was effected by heat, up to 175°C. Above 175°C, surface sorption decreased, while internal bulk partitioning increased, indicating marked internal changes of structure.

Nonaqueous Bleaching of Cellulose by Perchloroethylene-Hydrogen Peroxide-Water

Cellulosic fibers were bleached in perchloroethylene using small quantities of a solubilized mixture of peroxide and water. The diffusion coefficient of solubilized peroxide into cellulose was about equal to that of solubilized water. In contrast to bleaching in aqueous solutions, the peroxide was an effective oxidant even at room temperature. Vis cosity data, tensile strength loss, and change in blue reflectance demonstrated the interdependence of the sorption characteristics and the bleaching efficiency.

Nonsilicate Stabilization of Hydrogen Peroxide Bleach Solutions

Alkaline solutions of hydrogen peroxide are stabilized by addition of calcium chloride and disodium phosphate. Evidence is given that stabilization may be due to the forma tion of CaHPO4 as precipitate.