摘要:

AbstractAn experimental study has been performed to identify the controlling conditions when self‐generating flames move through and transform flame‐retardant treated and untreated cotton fabrics. The approach has been to compare the chars formed by flames with those produced by induced (nonflame) thermal decomposition under known conditions of temperature and environment. Char comparisons were made mainly through internal reflection infrared spectroscopy. Considerable variations were found among chars formed by flames moving in different directions in space, corresponding to differences in the maximum temperatures and degree of contact with oxygen experienced by the materials during burn

ISSN:0449-2994    

DOI:10.1002/polc.5070360104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractThermal analysis of a hardwood reflected the pyrolysis of its main components including xylan and cellulose. Thermal properties of these components were investigated with model compounds consisting of α‐D‐xylose, substituted phenyl β‐D‐xylopyranosides, β‐Dglucopyranosides and α‐D‐arabino‐hexopyranosides and 1,6‐anhydro‐β‐D‐glucopyranose.At the lower temperatures these molecules displayed anomerization, loss of water and phase change, which were studied with a variety of physical methods. Calorimeteric and wide line NMR measurements showed that 1,6‐anhydro‐β‐D‐glucopyranose and related anhydro sugars undergo plastic crystalline transition, involving reorientation of the molecules about their centers of gravity and self‐diffusion before melting.At more elevated temperatures the above compounds showed cleavage of the glycosidic group, polymerization of the sugar moiety, decomposition and evaporation of the pyrolysis products. This involved some heterolytic reactions, which could be catalyzed by acid or alkaline materials.Kinetics of the pyrolysis process, including the rates and energies of activation were determined by thermal analysis and ESR spectroscopy. These data indicated that cleavage of the glycosidic bond is directly influenced by variation of its electron density and constitutes the rate determining step in

ISSN:0449-2994    

DOI:10.1002/polc.5070360105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractOxidative reactions in cellulose are commonly initiated by thermal, ultraviolet, and high‐energy radiations and by chemical oxidation. Long‐lived free radicals, formed in cellulose on the localization of energy from thermal, ultraviolet, and high‐energy radiations, and short‐lived free radicals, formed in cellulose by oxidation, e.g., by ceric ion or redox reactions, were investigated by electron spin resonance spectroscopy. Dehydrogenation and oxidative depolymerization reactions of cellulose are indicated. The physical, chemical, and morphological effects of these free‐radical initiated reactions on cellulose are summarized. The formation of free radicals in cellulose also increases the chemical reactivity of cellulose, particularly for chain copolymerization reactions with vinyl monomers. Preparation of cellulose‐poly(vinyl) copolymers, using free‐radical initiation, yields paper, film, wood, and textile products with new physical and chemic

ISSN:0449-2994    

DOI:10.1002/polc.5070360106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractCertain aspects of cellulose depolymerization by oxygen in alkali were investigated with model compounds. Oxidation of hydroxyl groups was studied using low molecular weight glycols and alcohols. Hydrogen peroxide was identified as the peroxidic intermediate observed during oxygen oxidations of carbohydrates. Oxidation of glucitol by either alkaline hydrogen peroxide or oxygen is autocatalytic with a discrete induction period. When hydrogen peroxide is initially present in the oxygen oxidation, the induction period is considerably reduced. In the presence of potassium iodide, the induction period is lengthened. Potassium iodide inhibits the depolymerization of cellulose by oxygen and alkali and, in the presence of magnesium ions, provides more stabilization than either alone. A mechanism to explain these results is proposed.

ISSN:0449-2994    

DOI:10.1002/polc.5070360107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractThe major changes which occur in the DP distribution of cellulose in wood pulp owing to the refining of unbleached stocks to produce several types of finished pulp have been examined by GPC. Represented in this study are sulfite and sulfate pulping processes and paper and dissolving grade pulps. Factors which influence the definition by GPC of small differences in chain length among high DP pulps were considered. The high DP extremes of ten celluloses were compared by GPC after prefractionation by fractional precipitation. Results classify only small percentages above 3500 DP and then only in the highest average DP pulps examined. The cold alkali‐soluble fractions isolated from a high and low DP sulfite paper pulp and a prehydrolyzed sulfate pulp were compared by GPC and differences have been revealed which were not evident from viscometric DP measurement

ISSN:0449-2994    

DOI:10.1002/polc.5070360108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractGel permeation chromatography (GPC) has been used to determine the molecular weight distribution of cellulose in rayon print cloths. The fabrics were made from a regular and a high wet modulus rayon with staple length of 1 9/16 inches in an 80 × 80, 31 × 41 singles construction. The effects of various treatments of the print cloths including bleaching exposure to UV and abrading on the yarn properties and the molecular weight distribution were determined.With chemical treatments, the changes in the molecular weight distribution in both warp and fill were similar. The chemical reactions with the fabric immersed in solution were fairly uniform throughout the yarn and in the filaments. In this group, bleaching drastically reduced the average molecular weight.Degradation due to abrasion and flexing was severe. Results indicate that the larger molecules are particularly susceptible to mechanical degradation. The detritus from abrasion of the high wet modulus and the regular rayons had similar, relatively narrow molecular weight distribution.The changes in yarn properties and distribution on washing were primarily the result of mechanical damage. Heating at 400°F for 30 min substantially changed the staining characteristic of cross sections of the yarns. The molecular weight distribution width increased on heating and for these samples, the weight average molecular weight determined from GPC was significantly greater than the value determined viscosimetrical

ISSN:0449-2994    

DOI:10.1002/polc.5070360109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractSolid state light scattering patterns from single wood fibers were recorded using a laser as the light source. The scattering was recorded in the Hvmode; i.e., with the incident light beam vertically polarized, the scattered light was passed through a horizontal analyzer, thus permitting the recording of only the scattering arising from anisotropy fluctuations. The scattering pattern was confined to a narrow line consisting of regularly spaced maxima and minima. The overall scattering envelope could be accounted for by a hollow cylindrical model with helically wound dipoles, while the periodicity in the intensity is a function of fiber diameter and cell wall thickness. Comparison of relative intensities led to the conclusions that cellulose of the wood fiber behaves optically as a biaxial crystal in that the cellulose crystallites are biaxially oriented in an axial‐tangentoplanar fashion in the cell wal

ISSN:0449-2994    

DOI:10.1002/polc.5070360110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractOne of the basic reactions during pulping processes is the penetration of wood chips by the delignifying solution. For the study of the distribution of fluids within the cell walls, dry and green samples of pine wood (Pinus sylvestris L.) were treated with aqueous solutions of staining compounds, only by dipping‐in (diffusion), under vacuum, and under pressure. Best penetration was achieved by vacuum treatment in dry wood and by pressure treatment in green wood. The studies made by electron microscopy and by electron probe microanalyzer showed that the staining material is not equally distributed in the cell wall. In all samples the compound middle lamella is intensively stained. In some places there is a high concentration of staining material in the secondary wall 1 (S1), in other places there is a high concentration in a zone of the secondary wall 2 (S2) adjoined to the secondary wall 1. In most cases the tertiary wall (S3) and the adjoined part of the S2 is stained more intensively than the residual S2. Also the tori of the bordered pits are penetrated by the staining substance. The connection between the passage and the distribution of fluids within the cell wall and the ultrastructure of the cell wall is discusse

ISSN:0449-2994    

DOI:10.1002/polc.5070360111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractThe formation of ring shake, a tangential separation of xylem tissue, is being studied in selected red oaks, white oaks, and black walnut. Previous studies have indicated that it is frequently necessary to make detailed analyses throughout one tree in order to evaluate correctly possible stages of development of this defect for the sample under investigation. In the present study, anatomical and chemical analyses both along the shake zone and for a normal zone within a black walnut tree are discussed. Anatomical investigations formed the basis for selection of xylem subdivisions for subsequent chemical analyses. The ring shake was tangentially confined to a single annual increment. This increment was radially subdivided into eight consecutive portions from earlywood through latewood. Each portion was used for determinations of specific gravity, extractives (ether, alcohol, hot water), methoxyl, and certain inorganics. Similar analyses were made on a “control” increment. The possible development of ring shake within the sample tree is presented in terms of resultant chemical and anatomical d

ISSN:0449-2994    

DOI:10.1002/polc.5070360112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY

摘要:

AbstractFreely drying fibers exhibit collapse and twist behavior that is only infrequently observed in the formation of a paper web. Anisotropic fiber shrinkage models are employed that enable calculation of the twisting energy of a freely drying fiber as well as the reverse case (dry to wet). The twisting energy appears to be highly significant in relation to the fiber and bond energies associated with paper strength. Some experimental results with southern pine fibers have been obtained using specially designed testing devices.

ISSN:0449-2994    

DOI:10.1002/polc.5070360113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1971

数据来源: WILEY