摘要:

AbstractThe classic equation1in use throughout the urethane industry to predict the compressive properties of rigid foams is(1)\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm compressive property} = K({\rm density})^a . $\end{document}The value ofKandaneed to be determined experimentally for each foam system at a given temperature. By evaluating the compressive properties of 14 different rigid urethane foams,awas defined as 1.75 for all materials at all test temperatures. General equations for predicting the foam's compressive properties over a temperature range of −65° to 325°F (−54° to 204°C) were then developed. These general equations appear to be reasonably accurate in predicting the compressive properties of any rigid urethane at any temperature up to the foam's softening point. The equations are of the form shown above withKbeing a function of temperature only. Finally, theKterm was defined as a function of temperature. The equations developed for predicting the compressive strength and modulus of the rigid urethane foams are:(2)\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm compressive strength} = (8.09 - 0.0178T){\rm density}^{1.75} $\end{document}forTequal to or greater than 77°F (25°C), and(3)\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm compressive modulus} = (191 - 0.369T){\rm density}^{1.75} $\end{document}forTequal to or greater than −65°F (−54°C), where the compressive strength and modulus are in pounds per square inch and density is pounds per cubic foot. These equations are valid up to the softening po

ISSN:0021-8995    

DOI:10.1002/app.1976.070200801

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe viscoelastic properties of aqueous solutions of amylose–iodine at ultrasonic frequencies have been investigated by a torsional method using quartz crystal resonators. The frequency dependences of the storage (G′) and loss (G″) moduli show that the hydrodynamic interaction increases with the addition of iodine. The effects of the intermolecular hydrogen bonds could be observed from the concentration dependence of viscoelastic functions. The concentration dependences ofG′ andG″ − ωηswere extremely large, but the concentration dependence decreased with the addition of 2 moles of urea since the effect of hydrogen bonds was minimized. The intramolecular hydrogen bonds seem to affect the hydrogen bonds was minimized. The intermolecular hydrogen bonds seem to affect the tightness of the helical structure of the amylose–iodine complex in water. The frequency dependences of the intrinsic moduli at infinite dilution were compared with the hybrid model theory of Ferry et al. The helical structure of the amylose–iodine complex appears to be more rigid than that of other helical polymers such as poly(γ‐benzyl‐L‐glutamate). However, the flexibility of the helix appears to become more prominent with the addition of urea. When the poor solubility of amylose in water was improved by the addition of ethanol, the conformation of amylose–iodine complex became similar to that in the noncomplex system, where amylose seems to assume a loose and ext

ISSN:0021-8995    

DOI:10.1002/app.1976.070200802

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of low‐density polyethylene, isotactic polypropylene, and polyisobutylene has been studied in helium at a heating rate of 20°C/min using an experimental system which consists of a programmable pyrolyzer, a thermal conductivity cell, and a mass chromatograph.For low‐density polyethylene, the formation of a homologous series of volatile products corresponding to alkanes and alkanes is interpreted in terms of an intramolecular radical transfer process in the primary macroradicals to the 5th, 9th, 13th, and 17th carbon atoms of the chain.For isotactic polypropylene, the formation of a homologous series of volatile products corresponding to monomer, dimers, trimers, and higher oligomers is explained also in terms of intramolecular radical transfer processes. Transfers to the 5th, 9th, and 13th carbon atoms in the secondary macroradicals (indexing from the secondary carbon atom at the chain end) and transfers to the 6th, 10th, and 12th carbon atoms in the primary macroradicals are shown to account for the major products of pyrolysis.For polyisobutylene, in addition to the depolymerization process which accounts for the extensive formation of monomer, intramolecular radical transfer processes in the primary and tertiary macroradicals (the processes proceeding predominantly in the primary macroradicals) are shown to account for the formation of the dimers, trimers, and higher oligomers that occur in the volatile products of decomposi

ISSN:0021-8995    

DOI:10.1002/app.1976.070200803

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

年代:1976

数据来源: WILEY

摘要:

AbstractSwelling of cotton in zincoxen solutions of various concentrations was performed for 1 hr at 0°C. The crystallite orientation and the crystallite dimensions of the swollen cotton fibers were determined by x‐ray techniques. The swelling in zincoxen improved the orientation and Young's modulus. The relationships between the modulus and (a) the crystallite orientation and (b) the crystallite dimensions were measured, and the correlation was found to be good with the former and poor with the latt

ISSN:0021-8995    

DOI:10.1002/app.1976.070200804

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

年代:1976

数据来源: WILEY

摘要:

AbstractFor the hydrothermal degradation of cellulosic matter, an apparatus was developed in which water is used as extraction medium. Samples, 0.15 g each, of pure cellulose (filter paper), natural straw, and14C‐labeled straw were treated at temperatures of between 200° and 275°C. Of the inserted cellulose, 65.7% was recovered at the optimum temperature as sugars and hydroxymethylfurfural. It was possible to degrade the straw selectively: at lower temperatures, the hemicellulose part of the plant matter was converted to xylose and arabinose; and then at higher temperatures, the cellulose was converted to glucose and cellobiose. At the same time, a certain amount of the sugars was transformed to furfural compounds. The growth behavior of the yeastCandida utilis(strain Weissenbach) was analyzed, using cellobiose, xylose, and glucose (standard) as carbon sources. The growth curves applying cellobiose were nearly identical to those of glucose. Xylose showed lower productivity than the hexoses. The main products of the hydrothermal degradation can, therefore, be used favorably as nutritive substances for this proteinproducing ye

ISSN:0021-8995    

DOI:10.1002/app.1976.070200805

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe combination of an extraction technique with proton magnetic resonance spectrometry (PMR) has provided an analytical method for the determination of hydrocarbon mineral oil blended into an impact polystyrene. The amount of extraction time necessary for quantitative removal of the oil has been shown to be dependent on resin particle size. A linear correlation has been found between the weight of the extract obtained from 10.00 g resin and the per cent oil found in the resin.

ISSN:0021-8995    

DOI:10.1002/app.1976.070200806

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe effects of variables on treatment of the gel permeation chromatogram are reported. Variables investigated include (1) the molecular weight distribution of polymers for preparing the calibration curve, i.e., the logarithm molecular weight–elution count relationship, (2) nonlinearity of the calibration curve, and (3) fluctuation of the baseline. The deviation of the calibration curve prepared by the polymer having broad molecular weight distribution was evaluated in detail by assuming log‐normal distribution function for the distribution. The polymer having aDvalue less than 1.3 was recommended for this purpose. Generally, the shape of the chromatogram is fairly different from that of the true molecular weight distribution curve when the calibration curve is not linear over the entire range of interest. By fitting polynomials to the calibration curve, the chromatogram was sufficiently converted to the molecular weight distribution curve. The apparent difference between them was removed. Slight deviation of the baseline from the true one gave rise to obvious error in the calculated molecular weight and its distribution, especially for the sample having a broad distribut

ISSN:0021-8995    

DOI:10.1002/app.1976.070200807

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

年代:1976

数据来源: WILEY

摘要:

AbstractNodular morphology is observed on free surfaces, fracture surfaces, and etched surfaces of epoxy resins of widely different cure and chemistry. The influence of high‐ and low‐energy substrates on nodule size is illustrated. Fine structure or “dimples” exist on several individual nodules, and various states of agglomeration of nodules are depicted. The possible relations between nodular morphology and adhesion phenomena are di

ISSN:0021-8995    

DOI:10.1002/app.1976.070200808

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe behavior of cellulose materials in aqueous solutions of polyethylenimine was investigated. Sulfite‐bleached cellulose, sulfite unbleached, sulfate unbleached, and monocarboxylcellulose were used. The adsorption kinetics of polyethylenimine by monocarboxylcellulose were studied in detail. The velocity constants of the process, the velocity temperature coefficients, and the activation energies were calculated. The reaction order was established. The physical type of polyethylenimine adsorption by cellulose was established, and it was shown that the adsorption isotherms comply with the equation of Langmuir. On the basis of the data and on the dependencies obtained, the equations of adsorption in the temperature interval of 0°C to 60°C were deri

ISSN:0021-8995    

DOI:10.1002/app.1976.070200809

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

年代:1976

数据来源: WILEY

摘要:

AbstractA novel flash thermolysis technique was developed and used to elucidate factors which control preflame phenomena in halogen‐modified impact polystyrenes. The interrelation between the flux of fuel from impact polystyrene, the flux of flame quenching agents from decabromodiphenyl oxide and metal oxides, and the formation of char was quantified in flash thermolysis experiments at>500°C. The results were correlated with the performance of materials in a standard flammability rating test. In contrast to existing theories of flame retardancy via aromatic halide–antimony trioxide systems, it was found that polymeric free radicals generated during the burning process participate in the halogen release mechanism. The temperature for the halogen release is proportional to the bond strengths of the matrix resin. The specific role of polybutadiene in halogen‐modified impact polystyrene was recognized to include impact modification, halogen release synergism, and the reduction of dripping tendencies during b

ISSN:0021-8995    

DOI:10.1002/app.1976.070200810

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

年代:1976

数据来源: WILEY