摘要:

AbstractA new method for the determination of the activation energy for the setting of silicic acid solutions is described. Experimental results point to the conclusion that setting to a gel occurs at a definite stoichiometric point which is independent of temperature.

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010601

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractIn using the velocity ultracentrifuge in conjunction with free diffusion measurements for the determination of molecular weights of polymolecular systems, it is desirable to know what average molecular weights are obtainable. These average values are not simple moments of the molecular weight frequency curve, but depend on the methods of experimental observation, and on the hydrodynamic character of the molecules in solution. Most often, however, the average molecular weight falls between the number and weight‐average value

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010602

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractAn investigation of the copolymerization of many monomer pairs induced by benzoyl peroxide has shown that an order of monomer reactivity with radicals exists. By utilizing the data available, it was possible to make a semiquantitative arrangement of many monomers according to their relative rates of reaction with radicals. A symmetrical selectivity factor is assumed to account for deviations from the order in copolymerization reactions. This selectivity may be attributed to (1) complex formation between monomers or to (2) dipole, steric, or other factors which are independent of concentration. Copolymerization equations have been derived for each case and application of them to styrene–methyl methacrylate mixtures has indicated that selectivity due to (2) is most important in this system. The equation for case (2) has been applied to other copolymer system

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010603

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractThe kinetics of the polymerization of methyl methacrylate in emulsions has been examined. The initial rate of polymerization is independent of the amount of discontinuous monomer phase present and it is concluded that initiation occurs in the aqueous phase. Monomer is observed to disappear from the discontinuous phase more quickly than it polymerizes, and probably forms a monomer‐polymer mixture with the polymer produced. An increase in the subsequent rate of polymerization is attributed to the fact that propagation of the growing polymer chains occurs in this monomer–polymer mixture and this entails a decrease in the velocity of termination due to the high viscosity of such mixtu

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010604

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractThe relationships which exist between the solvation and shape of colloid particles, as well as between solvation and viscosity, are discussed. From the most important experiments on these subjects the following conclusions may be drawn. Solvation is dependent on the size and shape of the particles and on the chemical relationship of the dispersion medium to the dispersed portion. True or chemical solvation is generally very small and there is no reason to speak of a thick and tightly bound solvent layer. The solvation of compactly formed particles of spherocolloids is greater, the smaller the particles (all other conditions being equal). Solvation is greater, the more loosely the particles are formed (for dispersion mediums having similar chemical properties and for similar dispersed or dissolved substances). Solvation increases when a corpuscular particle is transformed into a rodlike or threadlike particle; the viscosity also increases; if the threads are further broken down into smaller fragments, then the viscosity decreases, but a further increase in the chemical solvationis supposed to occur. The stability of many lyophilic sols, especially the proteins, depends very little on the solvation; it is mainly dependent on the chemical characteristics of the atomic groups which are found on the surfaces of the particles; the least stability is found for surfaces which contain heteropolar groups—that is, surfaces which have the same number of positive and negative ion

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010605

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractBy treating potato juice with acid it was found that potato globulin is converted to albumin and an insoluble casein‐like protein. Potato albumin, salted out with ammonium sulfate and purified by dialysis, is very similar to ovalbumin; it is reconverted into a globulin‐like protein by alkali. Solutions of potato albumin in water, as well as in acids and alkali, have a very low viscosity. Alkaline solutions of globulin have a greater viscosity than those of albumin; the viscosity numbers of the difficulty soluble protein are even greater. On the basis of the viscosity data, it was concluded that the albumin particles are corpuscular, the globulin molecules are longitudinal, and that the dissymetry is greatest for the difficulty soluble protein particles. On the basis of the different solubilities of all three proteins (which apparently have approximately the same chemical composition), it was concluded that the albumin molecule was the smallest and the difficulty soluble protein molecule the largest. An aqueous solution of potato albumin is denatured when heated to 50–60°, the viscosity thereby increasing more than 100‐fold. The solutions become only slightly turbid, but do not flocculate. This unusual viscosity rise can be explained by the transformation of globular albumin molecules into fibrous, elongated particles. Only a slight viscosity increase is observed when alkaline solutions of albumin are heated. Albumin, in the presence of small amounts of salt, is precipitated at 50–60°; the salts also lower the turbidity point. However, very small concentrations of calcium chloride have a stabilizing effect. Albumin is not coagulated at room temperature by 1–2 N salt solutions. The experiments on the effect of cold on potato albumin showed that albumin, after congealing and thawing out, was more easily precipitated than the control solution. The viscosity of the cold‐damaged albumin was somewhat less than that of the control solution. It was ascertained that the deaminated product of potato albumin was very similar to deaminated ovalbumin (solutions of high viscosity;

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010606

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractA general theory is proposed to account quantitatively for the heat polymerization and gelation of the nonconjugated vegetable oils. This is based on a direct approach to polyfunctionality as developed from quantitative considerations of partial random distribution of the fatty acid components in the triglyceride molecules. The differing polymerization rates of linseed and soybean oils are accounted for on the basis of the assumed influence of certain cis‐trans geometric isomers. The theory accounts for the anomalous extensive linear polymerization and nongelation of olive oil. Calculations from the theory agree substantially with experimental results on average molecular weight, iodine value, and the percentage of insoluble, infusible cross‐linked polym

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010607

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractAn elementary theory is given for the rolling of polymeric materials, for the case in which the deformation is largely an irreversible flow of the viscous type. The theory treats the rolling process as the homogeneous deformation of volume elements over the arc of contact and neglects frictional forces that may exist at the roll surface. A numerical example is given of the calculation of roll pressure, which agrees with available data to a factor of two or better. A more complete test will require parallel measurements of viscosity and roll pressure on the same material.

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010608

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractIn the rolling of Plastic sheet the viscous work gives rise to heating of the plastic sheet. The maximum temperature reached in the interior of the sheet during shearing is of the interest, both in the theoretical calculation of roll pressure, and from the point of view of possible thermal decomposition effects. A calculation is given for a simple, some‐what artificial, model, which leads to an upper value for this maximum temperature if a measurement of the average temperature of the emergent sheet is given. The model taken is that of an infinite sheet, of thickness 2δ, in which heat is continuously liberated at the rate of 4ηϕ2cal. cc.−1sec.−1, where ϕ is the relevant value of the rate of compression (assumed constant across the sheet). The curve giving the temperature distribution across the sheet is calculated numerically for two cases; it is relatively flat, as would be expected on physical grounds, since the viscosity, η, decreases as the temperature rises. It is concluded that these thermal effects may be neglected in the calculation of roll pressure

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010609

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY

摘要:

AbstractPolyvinyl alcohol may be reacted with methoxyacetaldehyde, 2‐methoxyethoxyacetaldehyde, 2‐methoxyethoxyacetaldehyde, 2‐n‐propoxyethoxyacetaldehyde, tetrahydrofurfuryloxyacetaldehyde, or 3‐methoxypropionaldehyde, or with mixtures of these aldehydes, to yield thermoplastic resins which are soluble in cold water below specific temperatures peculiar to each resin, and which are soluble in most organic solvents except aliphatic hyd

ISSN:0022-3832    

DOI:10.1002/pol.1946.120010610

出版商:Interscience Publishers, Inc.    

年代:1946

数据来源: WILEY