摘要:

AbstractThe transverse NMR relaxation times of hydrogen nuclei of water absorbed in white spruce sapwood [Picea glauca(Meunch) Voss] were measured for moisture contents in the range from 5 to 176%. The spin echo amplitudes resulting from the Carr–Purcell sequence decay nonexponentially suggesting the possibility of at least two different relaxation times for water in wood. A simplified structural model of the wood–water mixture is used to estimate the rates of chemical exchange at room temperature of hydrogen nuclei between various sites in the system. The high‐resolution NMR line shape is discussed briefly in terms of this proposed

ISSN:0021-8995    

DOI:10.1002/app.1979.070231101

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

年代:1979

数据来源: WILEY

摘要:

AbstractA new method is developed to estimate the reactivity ratios from composition–conversion data based on nonlinear regression. Previously published experimental data for the copolymerization of acrylic acid and acrylamide are analyzed by the new method and the results compared to those reported by the original investigators. Composition–conversion data were collected for this copolymerization system at intermediate conversion levels and over a limited range of compositions. Values for the reactivity ratios at 40°C were obtained from these data by the new algorithm and compared to the literature va

ISSN:0021-8995    

DOI:10.1002/app.1979.070231102

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

年代:1979

数据来源: WILEY

摘要:

AbstractProcedures were developed for the analysis of copolyesters and copolyamides by saponification or hydrolysis of the copolymers to their component dicarboxylic acids, glycols, amino acids, or diamines and quantitatively identifying these by gas chromatography. The alcohols, amines and acids were converted to volatile trimethylsilyl derivatives for the analysis, and linear correlations were observed between carbon atom contents of these derivatives and retention times in the chromatograph.

ISSN:0021-8995    

DOI:10.1002/app.1979.070231103

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe feasibility of using a copolymer composed of styrene, acrylonitrile, and acrylamide or methacrylamide in the formation of a high‐strength thermally and chemically stable polymer concrete for use in geothermal environments has been demonstrated. Specimens produced with the copolymer in conjunction with an aggregate containing sand and portland cement had compressive strengths in the range of 25,000 to 30,000 psi at 20°C and were thermally stable up to ∼240°C. A study of the effect of monomer concentration on the properties of the polymer concrete indicated that the optimum concentration is in the range of 12 to 13 wt. %. Increased monomer concentrations lead to a nonuniform polymer distribution within the composite, resulting in a deterioration of the properties. The optimum properties are obtained when the monomer is used in conjunction with an aggregate containing 70 to 80 wt. % silica sand and 20 to 30 wt. % portland cement. The results from laboratory and field evaluations in progress indicate that the materials can be used for pipe or as protective liners on pipe and vessels in electric generating and direct utilization geothermal proc

ISSN:0021-8995    

DOI:10.1002/app.1979.070231104

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

年代:1979

数据来源: WILEY

摘要:

AbstractFormation of membranes from a binary system, poly(vinyl chloride) and dimethylformamide, was studied. Phase separation during membrane formation was caused by absorption of aqueous vapor from the atmosphere. The membrane structure was closely related to the degree of phase separation. The membrane formation process was divided into three stages, i.e., an early stage, a transitional stage, and a late stage. By leaching the solution at the early stage, where the casting solution was still transparent, a membrane with a finger‐like structure was obtained. On the other hand, a network structure was obtained by leaching at the late stage which was dependent on the molecular weight and the concentration of poly(vinyl chloride). The membrane structure was predominantly controlled by the mobility of polymer molecules in the casting solutio

ISSN:0021-8995    

DOI:10.1002/app.1979.070231105

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

年代:1979

数据来源: WILEY

摘要:

AbstractAnisotropy in mechanical properties, expansion coefficients, and long‐term shrinkage of PET films was determined. The films ranged in thickness from 0.92 to 14 mils. Young's modulus, ultimate strength, ultimate elongation, and coefficient of thermal expansion were strongly anisotropic. This anisotropy was related to orientation in the films. Yield stress and coefficient of hygroscopic expansion were more nearly isotropic. In general, the thin films showed more anistropy than the thick films due to better in‐plane orientation in the thin fi

ISSN:0021-8995    

DOI:10.1002/app.1979.070231106

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe role of hydroxyl ion concentration in the endwise depolymerization of hydrocellulose has been investigated in sodium hydroxide solution (0.05–18.6N) at 120°C, by determining the amount of degradation and the changes of carboxyl content and degree of polymerization in the solid phase. The extent of degradation increases with the base concentration up to about 6Nand then sharply decreases thereafter. These data are discussed in terms of altering the accessibility and the relative rates of peeling and stopping reactions in varying concentrations of alka

ISSN:0021-8995    

DOI:10.1002/app.1979.070231107

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

年代:1979

数据来源: WILEY

摘要:

AbstractMechanical properties of electron beam‐cured films were studied as a function of oligomer structure and monomer diluent. In films cast from polyester acrylourethane oligomers, increasing the chain length between the two acrylate groups on each end resulted in a decrease in breaking strength from 7000 psi to 1000 psi in Young's modulus from 200,000 psi to 700 psi, and in glass transition temperature from 50 to −25°C, while the ultimate elongation increased from 20% to 210%. These properties were virtually independent of dose above 1 Mrad. The elongations were compared with literature values at equivalent degrees of crosslinking and found to fall within the range, but on the low elongation side of the distribution. It was speculated that the crosslinks' functionality would equal the average degree of polymerization of the double bond at each end of the oligomer, resulting in multirayed, star‐shaped crosslinks with less flexibility than those with the usual functionality of 3 or 4, and methods for reducing this functionality were investigated. Addition of active monomers effected only minor change, but diethylaminoethyl acrylate was found to be very helpful in increasing the extensibility of these films considerably. This behavior can be explained by assuming that this monomer has a significant chain transfer constant, which should reduce the degree of polymerization of acrylic endgroups, producing a looser str

ISSN:0021-8995    

DOI:10.1002/app.1979.070231108

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

年代:1979

数据来源: WILEY

摘要:

AbstractProperties of electron beam‐cured film from 100% reactive mixtures consisting of polyester diacrylourethane oligomer, copolymerizing monomer, and chain transfer agents were investigated. The inclusion of chain transfer agent in such polymerization reaction was aimed to reducing the degree of polymerization of the double at each end of the oligomer, which is believed to be responsible for the low extensibility of these films. In general, these agents were found to result in some retardation in the polymerization reaction, but none of them influenced the mechanical properties of the cured films except mercapto‐functional agents, which were found to drastically affect these properties. By the addition of a mere 2% to 3% of these agents it was possible to toughen the EB‐cured films by increasing both the extensibility and breaking strength. This confirms the above speculation and brings the properties of these films to a level almost comparable to those of linear polyuret

ISSN:0021-8995    

DOI:10.1002/app.1979.070231109

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

年代:1979

数据来源: WILEY

摘要:

AbstractPMR spectroscopy and lanthanide shift reagents were used to determine sequence distribution of units of poly(dimethyldian‐phenolphtalein)terephthalate. The calculated values of degree of randomness confirm the theory that the copolyester obtained at the isokinetic temperature (200°C) has random distribution of comonomer units and copolyesters obtained at temperatures above and below this temperature have a tendency to form block units along the macromolecular cha

ISSN:0021-8995    

DOI:10.1002/app.1979.070231110

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

年代:1979

数据来源: WILEY