摘要:

AbstractSamples of methyl methacrylate were irradiated with 2‐m.e.v. electrons. Stopping and trapping of the incident electrons in the dielectric leads to the formation of a negative space charge. Under proper conditions the electric field of this charge can produce breakdown accompanied by the appearance of a characteristic discharge pattern. The nature of this effect is discussed. It is shown that the bulk of the space charge is concentrated in a narrow layer at a depth corresponding to the effective range of the electron beam. The quantity of charge released during breakdown is measured for various doses and compared with the value of the intercepted charg

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711511

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractA film, prepared from the copolymer of vinylidene cyanide/vinyl acetate, was stretched at 145°C. in a silicone oil bath using a draw ratio of one to three. The x‐ray diffraction data indicated that some orientation had occurred during the stretching process. In the stretched film the copolymer chains are separated by a distance of 5.86 A. This lateral chain spacing lies between those values reported for Orlon and polyvinyl acetate. Along the fiber axis of the vinylidene cyanide/vinyl acetate copolymer film, a high degree of disorder exists. As the temperature of stretching decreased from 165 to 145°C., the degree of orientation increased slightly. Amorphous patterns were observed for the films which were stretched in air immediately after being removed from oil baths at 187 and 22

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711512

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe fractionation of polystyrene by adsorption column chromatography has been investigated at room temperature. The adsorbent used was activated carbon suspended on Celite. The experiments were carried out on mixtures of characterized polystyrene fractions using MEK (a poor solvent), toluene (a better solvent), and tetralin (a good solvent) as eluents. It was found that; (1) the better the solvent, the higher the molecular weight portion which can be eluted out; (2) the better the solvent, the greater the total amount of the polymer which can be recovered from the column; (3) the lower molecular weight homologs are eluted out before the higher molecular weight homologs; (4) by controlling certain factors,e.g., the moisture, the chromatograms obtained were satisfactorily reproducible in detail. By using successively MEK, toluene, and Tetralin, polystyrene can be fractionated in a single passage through a column with about 80% total recovery of the polymer on the column. Optimum fractionation in a single passage is obtained by eluting with appropriate mixtures of the above solvents in order of increasing solvent power of the mixture to the polymer. These results correlate with existing information on the adsorption of polystyrene from solution.

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711513

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractPolyvinylbromide prepared by photopolymerization was fractionated. The molecular weights of the fractions were determined by a method which takes into account the fluorescent light for any polarization of fluorescence and anisotropy of the scattering molecule. The second virial coefficient‐molecular weight relation, the intrinsic viscosity‐molecular weight relation, and the values of the end‐to‐end distance indicate that P.V.B. follows the classical laws for a molecular coil. The molecular distribution curve was determined. The ratioMw/

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711514

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractSorption and diffusion of C4and C5hydrocarbons have been studied in thin films of ethyl cellulose in the temperature range 30 to 80°C. Only regions of low penetrant concentration were chosen in order to minimize hysteresis effects associated with slow relaxation of polymer chains. The data have been quantitatively compared with those for the same penetrants in rubber, since ethyl cellulose and rubber are examples of stiff and flexible chain polymers, respectively. In both solution and diffusion some major differences were found between the two types of medium. In rubber the heats of dilution were small and the corresponding positive entropies close to those predicted by the lattice theory of solutions. On the other hand, in ethyl cellulose at low penetrant concentrations the heats of dilution were strongly exothermal and the entropies negative. For both polymers diffusion coefficients of penetrants were dependent upon concentration, but whereas in rubber this concentration dependent decreased rapidly with rising temperature, in ethyl cellulose it was largely independent of temperature. Energy barriers involved in each unit diffusion process were comparable for a given hydrocarbon in rubber and in ethyl cellulose, while the molecular shape of the penetrant molecule substantially influenced the diffusion coefficients in each polymer. Further interpretation of the diffusion coefficients suggested that the involvement of polymer chains in each unit diffusion is much less for ethyl cellulose than for rubber. Explanations are offered, based upon the nature of the chains composing the two media and upon the existence of holes in the ethyl cellulose network, for the essential differences indicated above. The relative efficiency of ethyl cellulose and rubber membranes for gas separation is discussed

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711515

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractEpoxy, polyester, and styrene isothermal polymerizations have been monitored electrically. Sample resistivity—time records at different temperatures are reported for each class of polymer. These plots suggest that relative rates of reaction could be conveniently obtained if a correlation between extent of polymerization and electrical resistivity were known for the particular resins studied. Qualitative agreement between changes in infrared absorption and changes in volume resistivity as a measure of the extent of polymerization has been obtaine

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711516

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe thermal coloration which occurs in copolymers of methacrylonitrile with small amounts of methacrylic acid has been studied at 140°C. The infrared spectra of colored polymers show a decrease in nitrile absorption (which has been followed quantitatively) and new absorption appears, mainly at 1693–1490 cm.−1No volatile material is lost during coloration and molecular weight measurements show that neither chain scission nor crosslinking is involved. Copolymers of different compositions have been used to control the length of sequences of adjacent methacrylonitrile units, and it has been found that coloration is inhibited by larger concentrations of methacrylic acid. Colored polymer slowly reverts to the original material in solution, and rapid decoloration is effected by addition of aqueous solutions of acids, alkalis, and salts. A structure has been deduced for colored polymethacrylonitrile analogous to those proposed previously for paracyanogen and colored polyacrylonitrile. Essentially this is the results of the linking up of adjacent nitrile groups to form conjugated carbon‐nitrogen sequences of considerable length. It is suggested that this structure is formed in a nonradical chain process initiated at methacrylic acid units and propagated through adjacent nitrile units. The changes in solubility properties are not the result of crosslinking but of the rigidity of the modified polymer str

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711517

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe intermolecular contribution to light scattering by polymer solutions has been treated according to the smoothed Gaussian sphere model. Combining the results with the usual term for the individual molecule scattering we obtain for the reciprocal turbidity:\documentclass{article}\pagestyle{empty}\begin{document}$$ {{Kc} \mathord{\left/ {\vphantom {{Kc} I}} \right. \kern‐\nulldelimiterspace} I} = {1 \mathord{\left/ {\vphantom {1 {MP}}} \right. \kern‐\nulldelimiterspace} {MP}}\left( \theta \right) + 2Q\left( \theta \right)A_2 c + \ldots $$\end{document}The third virial term is also formulated. The angle dependent factorQ(θ) falls appreciably below unity at higher angles for large molecules in good solvents. Calculation ofQ(θ) according to the theory is illustrated. Its replacement by unity may under some circumstances invite appreciable erro

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711518

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractIntrinsic viscosities of cellulose acetates of degrees of substitution 2.86 and 3.00 and of cellulose trinitrate have been investigated as functions of temperature, solvent, and molecular weight. Large negative temperature coefficients (ca.−0.6% per degree) of [η] appear to be characteristic of cellulosic chains. These observed decreases in [η]with temperature are due to increases in chain flexibility, which are reflected in decreases in the characteristic ratior 02/M. The rather large variations in [η] with the solvent are shown also to be manifestations of altered chain flexibilities brought about in some manner, as yet unexplained, by specific solvent interaction. This behavior stands in marked contrast to that of other polymers for whichr 02/Mis independent of the solvent and varies only slightly with temperature, and for which solvent effects on [η] are wholly attributable to changes in the molecular expansion (α3) brought about by solv

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711519

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe infrared spectrum of polystyrene has been obtained in the region of 70 cm.−1to 3200 cm.−1. These data, plus Raman scattering data from the literature, are used to make a complete assignment of the normal modes of the polystyrene molecule. The benzene ring modes have been analyzed in detail in terms ofC2vsymmetry, and a set of normal vibrations has been proposed. On the basis of previous analyses of the benzene and monosubstituted benzenes, and a study of the combination bands, it has been possible to make a fairly satisfactory assignment of all of the benzene ring fundamentals. Assignments of the CH2, CH, and skeletal modes are made on the basis of previous studies of spectra of high polymers. The interpretation of the spectrum is in agreement with other evidence that the chain configuration is a random one,i.e., that the polymer is amorph

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202711520

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY