摘要:

AbstractThe swelling of vulcanized natural rubber, Buna S, neoprene, Perbunan, and Perbunan Extra was measured in various organic liquids. The essential influence of polarizability and polarity on the swelling equilibrium is illustrated by comparing series of solvents and polymers with gradually changing geometrical and chemical structure. Experiments on the influence of temperature and of strain on the swelling equilibrium are reported. The swelling properties of ebonites and similar derivatives allow some conclusions on the amount of cross linking in these polymers.

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020401

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractPractical, theoretical, and experimental aspects, including sources of error and methods of control, of the water and water vapor permeability of organic membranes are discussed. Determinations of the permeability have been made at two different temperatures. Data are given on: polyethylene (alkathene, Imperial Chemical Industries), polystyrene (Styroflex, D. Seekabelwerke), chlorinated polyvinyl chloride (Vinifol, I. G. farbenindustrie), cellulose acetates (Triacetat, Schering, and Triafol, I. G. Farbenindustrie), a plasticized polyvinyl chloride (Welvic, Imperial Chemical Industries), and a copolymer of vinylidene chloride and vinyl chloride (Saran, Dow).

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020402

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe permeability of vulcanized gutta‐percha membranes to gases was determined in relation to the rate of diffusion and solubility. The measurements, as functions of temperature, with four gases were taken below and above the melting point of gutta‐percha. The evidence is that the rates of permeation and diffusion increase sharply at approximately 45°C., due to melting of the gutta‐percha. In the same way, although to a lesser degree, the solubility of the gas likewise increases at the melting point. The activation energies of permeation and diffusion with the heat of solution were computed from the temperature function of those quantities. It follows from the results that crystallization of the elastomer reduces the gas‐solubility, the diffusivity, and the permeability—and increases the activation energy of diffusion. The interpretation of this high activation energy of diffusion is that, because of the crystallization, the macromolecules of the membrane adhere so firmly that greater energy is required to admit the gas

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020403

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe heats of polymerization of acrylic acid, methyl acrylate, methacrylic acid, and methyl methacrylate have been measured. Values for the heat of polymerization of unstrained polymer molecules have been calculated, and the low heat of polymerization of methyl methacrylate has been attributed to the presence of steric hindrance in the polymer molecule.

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020404

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractA description is given of the preparation, birefringence, and swelling capacity of a series of microscopically homogeneous, partially acetylated cellulose model filaments with an acetyl content varying from 0 to 2.3 acetyl groups per glucose residue, and obtained either by acetylation or by deacetylation. A higher degree of acetylation of these artificial fibers could not be attained without destruction of the fiber. The same holds true for native ramie fibers. The swelling was studied in water, acetone, and methanol. The degree of swelling of the filaments plotted against acetyl content yields entirely different curves for the acetylation and the deacetylation series. These curves can be readily explained by the hypothesis that the intercrystalline (so‐called amorphous) portion of the fiber substance is more accessible to the esterification and saponification reactions and is affected earlier than the crystalline portion. The birefringence of the acetylation series shows but a small—although apparently real—difference from that of the saponification s

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020405

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractA discussion is offered of the x‐ray patterns of partially acetylated and saponified cellulose model filaments with varying acetyl contents. They are substantially in conformity with the swelling experiments previously described in Part I (page 397) of this paper. (1) In nonrecrystallized filaments, chemical reaction takes place in the crystallites and the intercrystalline regions from the very beginning of the experiment. The rate of chemical conversion, however, is larger in the latter. (2) Acetylation of the hydrate cellulose crystallites results in a gradual increase in the (101) spacing, A0; the A3and A4reflections [corresponding to (101) and (002), respectively] remain unimpaired up to a gross acetyl content of at least 1.5 acetyl groups per glucose residue. (3) Maximally acetylated filaments containing 2.3 acetyl groups per glucose residue may be recrystallized by heating in methanol or ethanol. The diagram of the recrystallized product is identical with the pattern of cellulose triacetate II. With about halfway acetylated or saponified products, recrystallization is not realizable by means of a heating process in water or methanol. (4) Enhanced degree of local order as the result of previous recrystallization of maximally acetylated products produces a more pronounced difference in rate of saponification between the “crystalline” and “amorphous” fiber

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020406

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractMulti‐ingredient polymeric amides have been prepared by the condensation, under amide‐forming conditions of various combinations and ratios of components comprising hexamethylenediammonium adipate, hexamethylenediammonium sebacate, and ϵ‐aminocaproic acid or ϵ‐caprolactam. The physical properties of the investigated linear polymeric amides range, depending upon the polymer components and the proportions employed, from high‐softening, stiff, and difficulty soluble compositions to relatively low‐softening, pliable, and easily sol

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020407

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractBomb calorimetric measurements have yielded for the heats of combustion (—ΔHoc) at 25°C. of liquid styrene and solid polystyrene to form gaseous carbon dioxide and liquid water the values 4394.88 ± 0.67 int. kjoule per mole (1050.58 ± 0.14 kcal. per mole), and 4325.09 ± 0.42 int. kjoule per C8H8unit (1033.89 ± 0.10 kcal. per C8H8unit), respectively, and for the heat of polymerization of liquid styrene to solid polystyrene at 25°C. the value 69.79 ± 0.66 int. kjoule per mole (16.68 ± 0.16 kcal. per mole). The results obtained on two samples of polystyrene of different molecular weight were in agreement within the precision of the measurements. Measurements of the heat of solution of solid polystyrene in liquid monomeric styrene gave the value 3.59 ± 0.21 int. kjoule (0.86 ± 0.05 kcal.) evolved per C8H8unit of polystyrene at 25°C. Addition of this to the value for the heat of polymerization of liquid styrene to solid polystyrene gives the value 73.38 ± 0.69 int. kjoule (17.54 ± 0.16 kcal.) per mole of styrene for the heat of polymerization of liquid styrene at 25°C., when the final product is a solution of polystyrene in styrene containing 6.9% by weigh

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020408

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractPotentiometric titrations of polymethacrylic acid were performed at different concentrations, different molecular weights, and in the presence of neutral salts, as well as in dioxane‐water mixtures. It was shown that the pH of the solutions fulfills the relation, pH = pK — n log [(1 — α)/α]. pK and n are independent of the molecular weight and concentration if a suitable activity factor is introduced. The equation is applicable to free acid solutions as well as acid mixtures. Copolymers of the type, polyallyl acetate‐maleic acid, show a more complicated curve. The curve is of the “polydibasic” type. Each branch of it fits equation (2) well. The formula is analyzed and is proposed to be the result of the action of the Maxwell‐Partington statistical factor, as well as of the decrease in entropy accompanying the stretch of the randomly kinked molecule. This stretch is caused by the repulsive forces between the ionized carboxyl groups. The distribution curves of the various degrees of ionization present, for any pH, are given. The activity correction implies small units of the size of one or two carboxyl groups. The behavior in salt solutions is dependent not only on the activity correction, but also on the salting‐out factor. This factor is high in polyvalent salts. The titration curves in dioxane‐water mixtures are satisfactorily accounted for by the change in the activity factor with the

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020409

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020410

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY