摘要:

AbstractThe melting phenomena of aqueous polymer solutions and gels have been investigated by differential scanning calorimetry (DSC). The polymers used were synthetic polyacrylamide and poly(vinyl alcohol) samples as well as guar and xanthan gums. By using an empirical relation, the energy measured from the area under the melting peak yielded heats of mixing and sorption, when fitted by an association factor computed from the data. This factor (independent of the concentration) is a measure of the water fraction associated with the polymer and has a definite and characteristic value for a given polymer in water. When a crosslinking agent (potassium pyroantimoniate or chromic nitrate) was added to the water–polymer system, the association factor varied with the polymer concentration; the macromolecular chains thus become less accessible to penetrating water. If a branched gel was obtained owing to the formation of chemical crosslinks, a hump appeared on the melting pea

ISSN:0021-8995    

DOI:10.1002/app.1974.070180601

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe applicability of a model after Talamini for the bulk polymerization of vinyl chloride with several commercial initiators has been examined. The model agrees well with experimental rate data for the initiators: diisopropyl peroxydicarbonate, disecbutyl peroxydicarbonate,t‐butyl peroxypivalate, lauroyl peroxide and benzoyl peroxid

ISSN:0021-8995    

DOI:10.1002/app.1974.070180602

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

年代:1974

数据来源: WILEY

摘要:

AbstractAn experimental study of the inflation of a thin rectangular polymer sheet has been conducted to determine whether this technique can be used to measure the planar extensional viscosity of bulk polymers. Viscosities were determined at various extensional strain rates using an undiluted polyisobutylene of high molecular weight. Measurements were also made on the dynamic shear viscosity using orthogonal geometry and compared with “normalized” values of the planar extensional viscosity assuming equivalency of$\sqrt {\Pi _e} $the second invariant of the extensional strain rate tensor, and the frequency of rotation ω. Industrial fabrication operations where the planar extensional viscosity is expected to play a role include vacuum forming of large rectangular sheets whose length‐to‐width ratio is large and in injection molds having a center‐ga

ISSN:0021-8995    

DOI:10.1002/app.1974.070180603

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe idea that, with filled polymers, length fraction, area fraction, and volume fraction of filler are different appears to have gained wide acceptance. The fallacy of this, except for special directions in ordered arrangements, is demonstrated. This misunderstanding has led to widespread misinterpretation of experimental results in this field.

ISSN:0021-8995    

DOI:10.1002/app.1974.070180604

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe strain rate dependence on dynamic crack propagation in viscoelastic solids was experimentally verified for PMMA by the velocity gauge method and fracture surface observation. It was found that the dependence was mainly due to the viscous term effect, and this was supported by the observation of deviation of the stress‐strain curve from an elastic case. The elastic brittle crack propagation can be realized only in the high‐strain rate case for P

ISSN:0021-8995    

DOI:10.1002/app.1974.070180605

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

年代:1974

数据来源: WILEY

摘要:

AbstractA theoretical relationship has been developed which relates the ultimate strength of a composite containing spherical fillers to the size, volume fraction, and surface adhesion of the dispersed phase. The theoretical predictions are compared to experimental data using glass beads of known diameters in polyester resin matrix. Results were compared for the case of poor adhesion between the glass beads and the matrix and for the case of good adhesion. The derived relationships should be useful in helping to optimize the strength properties of particulate reinforced systems.

ISSN:0021-8995    

DOI:10.1002/app.1974.070180606

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

年代:1974

数据来源: WILEY

摘要:

AbstractHeat transfer measurements made when cyclohexane condenses on poly(tetrafluoroethylene) provide further support to the theory that absorption can occur on this surface.

ISSN:0021-8995    

DOI:10.1002/app.1974.070180607

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe permeation characteristics and the selectivity of four nitrile rubber films with respect to 1,3‐butadiene and isobutene were studied as a function of experimental conditions and the nature of membrane material. A specific research apparatus was developed, allowing the determination of both permeation rate and selectivity, at a temperature varying between 0° and 30°C and under a pressure of from 1 to 3 bars. The inverse proportion of permeation rate to membrane thickness was verified for a thickness of from 12 to 500 microns. An increase in temperature promotes liquid permeation and is detrimental to gas permeation, the latter being facilitated by an increase in pressure. The introduction of an inert gas pressure on the liquid did not bring about an increase in the liquid permeation rate. The permeation rate decreases as a result of an increase in the proportion of acrylonitrile in the rubber, which also affects selectivity; the latter reaches a maximum value when said proportion is about 23%. The effect of the composition of the feed mixture was also studied and curves were determined relating, simultaneously, selectivity and permeation rate to the 1,3‐butadiene content. Selectivity is maximal with mixtures having a very high 1,3‐butadiene content. The solubilities of 1,3‐butadiene and of isobutene in the four types of nitrile rubber were measured at 0°C and at 20°C (68°F). Selectivity can be interpreted in terms of the solubilities of the two

ISSN:0021-8995    

DOI:10.1002/app.1974.070180608

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe glass transition temperatures of linear and four‐ and six‐branched regular star polystyrenes are measured by penetration, differential scanning calorimetry, and a density gradient technique. The results of the three methods show that the glass transition temperature depends on the concentration of chain ends in the polymer sample. An attempt is made to assess the influence of the presence of the branch point on the glass transition temperature using a series of four‐branched polystyrenes containing varying amounts of isoprene near the branch point. However, any effect of the central branch point on the glass transition temperature is obscured by plastification of polystyrene by polyiso

ISSN:0021-8995    

DOI:10.1002/app.1974.070180609

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

年代:1974

数据来源: WILEY

摘要:

AbstractThis paper describes an interfacial viscometer. Rheological data of polymeric surfactants were obtained with the use of the instrument for liquid–liquid and liquid–gas interfaces. The surfactants studied were methylcellulose, poly(vinyl alcohol), polymer of diethylene glycoln‐butyl ether acrylate, and sulfonated poly(vinyltoluene). Investigations were conducted over a wide range of temperatures and concentrations of the surfactants in the liquid phase. The instrument was used to obtain surface area coverage data for the surfactants studied. The experimental data were compared with theoretical calculations. The data indicated that the absorbed film at the interface was an irregular film, i.e., not an ordered packing of the molecules at the interface. Significance of interfacial viscosity on droplet break‐up in a simple shear field was investigated. Droplet breakup studies substantiate the hypothesis that an absorbed polymeric film at an interface forms a complex visco

ISSN:0021-8995    

DOI:10.1002/app.1974.070180610

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

年代:1974

数据来源: WILEY