摘要:

Cotton linter pulp and paper pulp were subjected to hot refining with potassium and sodium hydroxide in the presence of sodium sulfide at concentrations of 5% and 20%. The resulting changes in their chemical, physical, and submicroscopic properties as well as their mercerization depth were studied. The addition of sodium sulfide during hot sodium or potassium hydroxide refining of the pulps resulted in a small increase in α-cellulose content of the cotton linters. Remarkable increase was observed in the case of the paper pulp as well as in the resulting decrystallization, and it increased the heterogeneity of the macromolecular structure of both pulps. This led to an increase in the swelling ability of the fibers as revealed from the results of water retention value (WRV), liquor retention value (LRV), and sodium hydroxide retention value (NaOH RV). The addition of sodium sulfide to sodium or potassium hydroxide during hot refining of the cotton linters or to sodium hydroxide during refining of the paper pulp led to the reduction in the degree of polymerization and to improvement in the reactivity towards xanthation. This was in contrast to the results of the alkali refining of the paper pulp with a mixture of potassium hydroxide-sodium sulfide in which the degree of polymerization was increased and the reactivity towards xanthation was decreased. The mercerization depth of the hot refined pulps was also investigated using FUR 1650 spectrophotometer absorption method. The cotton linters refined with a mixture of 5% sodium hydroxide-sodium sulfide possessed a higher degree of chemical purity and a good open and accessible fine structure and at the same time were characterized with a higher degree of polymerization suitable for use as a starting refined pulp for the manufacture of paper documents.

ISSN:0360-2559    

DOI:10.1080/03602559608000598

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this study, the flow equations of non-Newtonian fluids through pipes and annuli have been derived using the Robertson-Stiff rheological model. From this, new and simple nomographs have been constructed to estimate the pressure-loss gradient directly for both flow-through pipes and annuli. Results from these nomographs gave excellent agreement with the results calculated from the flow equations.

ISSN:0360-2559    

DOI:10.1080/03602559608000599

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A number of phenolic antioxidants were prepared using the reaction between acridly chloride ando-, m-, andp-amino phenols. These antioxidants were used in acrylonitrile-butadiene rubber compounds to achieve better products for various sealing applications. Several techniques were used to evaluate the prepared antioxidants and the processed rubber compounds.

ISSN:0360-2559    

DOI:10.1080/03602559608000600

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A mathematical model was developed to predict the performance of the oil displaced by water foam in porous media. In this model, the diffusivity equations of both water foam (the displacing phase) and oil (the displaced phase) were combined in a single equation, which was solved numerically by a finite difference method, using the implicit-explicit method. The proposed model was compared with Poiseueille's model which represents the porous media by straight capillary tubes. It was found that the proposed model is superior to that of Poiseueille, because the Poiseueille model does not take into account the variations in foam properties along the sand pack. The production data used for the proposed model were obtained experimentally from the displacement of oil by water foam of different qualities (externally generated foam). The plastic viscosity of the water foam was measured experimentally for four foam quality ranges using capillary tubes of different sizes. The effective viscosity of the water foam determined from the plastic viscosity was used in the proposed model. Foam viscosity was found to increase as the quality increases, and the water foam obeys a Bingham plastic fluid model. The porous medium was represented by a sand pack whose length was 36 cm and diameter was 6.3 cm. Its absolute permeability was 341 md and porosity was 22.8%. The foam consisted of tap water, surfactant, and nitrogen gas.

ISSN:0360-2559    

DOI:10.1080/03602559608000601

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The fundamental approach to the description of the kinetics of chemical reactions has been considered, and principle of chemical reaction independence and active mass law have been taken into account. Models for rate constants of elementary reaction have been discussed on the basis of the collision theory, the theory of activated complex, and the theory which takes into account the movement of intermediate particles to the reaction barrier. The collision theory is suggested for use at high temperatures, the theory of activated complex is recommended for application at moderate temperatures, and the theory which takes into account the movement of intermediate particle to the reaction barrier is relevant to low temperatures. It is emphasized that the principle of maximal change of free energy, which was suggested earlier, may be applied for analysis of the mechanism of chemical processes.

ISSN:0360-2559    

DOI:10.1080/03602559608000602

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Waste ethylene polymer film was chlorinated by suspension chlo-rination in water. The chlorinated product was used to modify the impact property of PVC. It improved the processing Theological performance, and the impact strength was increased two times more.

ISSN:0360-2559    

DOI:10.1080/03602559608000603

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Photoinduced graft copolymerization of acrylamide (AM) onto two types of acrylonitrile-butadiene-styrene (ABS) copolymers was extensively investigated in homogeneous media. The grafting process was conducted in chloroform in presence of 4-acetyldi-phenyl (4-AD). Ultraviolet (UV) irradiation was used in the range of 310 to 460 nm. The UV spectrum of 4-AD has sλmaxat 285 nm and shows n-π*transitions. The grafting parameters, such as weight conversion, grafting percentage, and grafting efficiency, were determined as a function of the irradiation time and the concentrations of monomer, initiator, and substrate. A reverse effect was observed between the grafting percentage and the butadiene content in ABS copolymers. The rates of graft copolymerization of AM onto the two types of ABS copolymers were determined. A Trommsdorf effect was observed in certain systems. The IR spectrum of ABS-g-AM graft copolymer shows the appearance of a new peak at 1685 cm-1that declares the presence of poly-acrylamide-grafted chains onto the ABS copolymer backbone. A probable copolymerization mechanism was proposed.

ISSN:0360-2559    

DOI:10.1080/03602559608000604

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Dominant commercial treatments currently used for wood preservation are pentachlorophenols (PCPs), creosote, and chromium copper arsenicals (CCAs). These wood preservatives present many studied and documented environmental and toxicological problems both with use of the products themselves and with the production of secondary reaction contaminants. Furthermore, several of these preservatives are considered priority pollutants according to the U.S. Environmental Protection Agency (EPA) and are heavily regulated. The need for an environmentally benign combined fire/rot retardant treatment for wood that will effectively reduce both fire and decay is clearly evident. Guayule resin, a co product during rubber extraction from the guayule shrub, is being explored by us as a natural, biodegradable wood rot and fire retardant with potential commercial applications. Wood impregnated with guayule resin has survived over 8 years in a tropical rain forest environment, free of rot, decay, and insect infestations. This study qualitatively analyzed treated and untreated wood samples For ignitability, flame spread, toxic fumes, and smoke generation. Ignitability of the wood sample of fixed geometry was quantified by measuring the time required for ignition of treated samples versus untreated samples. Flame spread was measured after ignition with a propane flame by a simple stopwatch-ruler technique. Smoke mass was determined in an Arapa-hoe Smoke Chamber as per ASTM D-4100. Analysis of the fumes involved continuous CO, C02, NOx, SOx, and O2analyses using a Bacharach Instrument Model NSX 300. An Andersen Inc. Model 2000 cascade impactor was used to determine the particlesize distribution of the smoke and for smoke mass. Most of the differences in the test data measurements between guayule-impregnated pine and untreated pine were found to be minor. However, the ignition data indicated that guayule-impregnated pine did not ignite as quickly as untreated pine. Based on the favorable data presented herein, further research of wood preservation with guayule resin is recommended.

ISSN:0360-2559    

DOI:10.1080/03602559608000605

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Polypropylene (PP) was grafted with acrylamide using benzoyl peroxide (BP) as an initiator by melt mixture. Effects of various parameters such as monomer and initiator concentration, reaction time, and reaction temperature on degree of grafting were studied. The graft copolymers were characterized by irradiation (IR), electron spectroscopy for chemical analysis (ESCA), wide-angle x- ray diffraction (WAXD), DSC, and contact angle studies.

ISSN:0360-2559    

DOI:10.1080/03602559608000606

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The extent of dissolution of wood in phenol was lower in the presence of water compared to those of aqueous alkali. The amounts of residue, combined phenol, and nonreacted phenol, as well as weight loss in liquefied mixture due to release of gaseous substances, changed widely with the change in composition of wood: phenol as well as with the concentration of alkali. In the presence of alkali, pH changed roughly four to five units during liquefaction reaction, while without alkali the change in pH was only about 2.0 to 2.5. The resulting pH was always acidic whether the starting pH was alkaline or acidic (e.g., noncatalytic system). However, after the liquefaction reactions, there was a large amount of uncombined phenol which could be removed by distillation method to a large extent. The molecular weight and melt flow properties of the wood-based phenolated resins, as well as flexural mechanical properties of wood flour-filled molded materials, were evaluated. All these properties vary with the variation of liquefaction conditions of wood in phenol. Generally, wood-based phenolated resins with higher amount of combined phenol were lower in both molecular weight and melt-flow properties, but were higher in mechanical properties.

ISSN:0360-2559    

DOI:10.1080/03602559608000607

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor