ISSN:0021-8995    

DOI:10.1002/app.1959.070010101

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

年代:1959

数据来源: WILEY

摘要:

AbstractGehman cold‐flex, volume‐temperature, and stress‐temperature studies were used to investigate the low‐temperature characteristics of polysiloxane copolymers with respect to copolymer composition. A complete range of phenyl methyl‐dimethyl siloxane copolymers were examined as elastomeric compounds. Like other copolymers, the stiffening temperature was dependent upon the composition of the copolymer. Stiffening of the elastomers was due to crystallization in some cases and second‐order transition in others. Copolymers having either low or high amounts of PhMeSO stiffened because of crystallization, while copolymers of intermediate composition (7.5 to 15 mole‐% PhMeSiO) stiffened because of nearness to their respective second‐order transition temperatures. Second‐order transition temperature increased with the PhMeSiO content. For those siloxane polymers and copolymers that crystallized, the process was rapid when compared with crystallization behavior of other polymer systems. Only one minimum low‐temperature stiffening point was found in the phenyl methyl‐dimethyl siloxane copolymer system. The unique low‐temperature characteristics of polysiloxane elastomers are explainable on the basis of three factors. These are: (a) very flexible molecules, (b) low temperature coefficient of viscosity over a broad temperature range including low temperatures, and (c) copolymerizability of dimethyl siloxane with other siloxanes containing bulky pendant groups which lower the

ISSN:0021-8995    

DOI:10.1002/app.1959.070010102

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

年代:1959

数据来源: WILEY

摘要:

AbstractVinyl chloride monomer was polymerized in an emulsion system in the presence of a redox catalyst and relatively low concentrations of emulsifier. The effects of sodium bisulfite, potassium persulfate, and commercial sodium lauryl sulfate concentrations on particle initiation were determined by response‐surface experimentation. A regression equation was developed which describes the number of particles per unit volume initiated in this vinyl chloride emulsion system. At subcritical emulsifier concentrations, the number of particles initiated was dependent primarily upon the emulsifier and sodium bisulfite concentrations and to a lesser degree upon the persulfate concentration. As the critical micelle concentration was approached, an apparent change in the particle initiation mechanism was observed, in that the sodium bisulfite concentration ceased to have an effect. In this system the change occurred at a concentration of 0.005% emulsifie

ISSN:0021-8995    

DOI:10.1002/app.1959.070010103

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

年代:1959

数据来源: WILEY

摘要:

AbstractA mechanism has been devised for the purpose of introducing a sudden strain of calculable amount into a viscoelastic fluid. The principle of the apparatus relies upon the deformation caused by the rotation of an elliptical sleeve about a flexible tube containing polymer solution. An apparatus has been constructed which can produce a 90° rotation (with consequent deformation) in the period of one millisecond. The detection of the strained state is accomplished by means of strain birefringence. In this way, relaxation can be studied in concentrated solutions for a time range beyond one millisecond

ISSN:0021-8995    

DOI:10.1002/app.1959.070010104

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

年代:1959

数据来源: WILEY

摘要:

AbstractDomains, or areas of inhomogeneities and imperfections, may be made visible in polystyrene by treatments of the plastic with certain liquids and vapors. Different types of domains are revealed by different techniques, depending upon the solvent power of the liquids and vapors. One type of domain reveals itself as craze cracks when polystyrene is first soaked in a nonsolvent such as methanol, and then exposed to the vapors of a solvent such as hexane or benzene. A second type of domain may be revealed by exposing polystyrene to certain mixtures of solvents and nonsolvents which produce a rough, whitened surface on the polystyrene. For the first type of crazing, the size of the domains is influenced by the frozen‐in thermal stresses, and the shape of the domains is influenced by molecular orientation. The domains of the second type are due to heterogeneity of molecular orientation and are not found in annealed specimens. A theory has been proposed which explains crack crazing in terms of adsorbed vapors in cracks and areas of imperfections in the polystyren

ISSN:0021-8995    

DOI:10.1002/app.1959.070010105

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

年代:1959

数据来源: WILEY

摘要:

AbstractThe force as a function of temperature at constant length for cellulose model filaments swollen in water shows a maximum the temperature of which decreases with increasing orientation. At an orientation achieved by a prestretch of 80%, no more maximum exists, and the force decreases monotonically with increasing temperature. This behavior cannot be attributed to changes in the entropy and enthalpy of elongation with temperature, but is due rather to changes in the degree of swelling. When corrections are made for this, the positive force‐temperature coefficient observed for some of the curves becomes negative. The equilibrium stress‐strain curves are linear up to elongations of 5%. The‐oretical evaluation of these curves is not possible with the present state of theory. Filaments with predominantly a skin structure show a minimum in the force‐temperature curves; this is the more common b

ISSN:0021-8995    

DOI:10.1002/app.1959.070010106

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

年代:1959

数据来源: WILEY

摘要:

AbstractAbout 3% by weight of carbon black adequately protects polyethylene against photo‐oxidation and, under accelerated test conditions, slightly inhibits thermal oxidation. As a rule small amounts of organic antioxidants are also added to the polymer for optimum protection. Now many of the common phenolic and amine additives have been found to function much less effectively in polyethylene containing carbon black than in clear polymer. Loss of effectiveness is attributed to adsorption and/or decomposition of the antioxidant by both basic and acidic carbon blac

ISSN:0021-8995    

DOI:10.1002/app.1959.070010107

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

年代:1959

数据来源: WILEY

摘要:

AbstractCommon secondary aromatic amine and alkylated phenolic antioxidants lose much of their activity in polyethylene containing carbon black. In contrast their thioether derivatives provide more protection against oxidation than the sum of the separate contributions of carbon black and the sulfur compounds. Organic disulfides and some thio‐ethers without amino or phenolic hydrogen also safeguard polyethylene from oxidation but only in the presence of carbon black. Likewise thiols are excellent protectants in combination with carbon black but not in clear polymer. Aliphatic thiols, disulfides, and their polymeric derivatives and related selenium compounds exhibit similar activit

ISSN:0021-8995    

DOI:10.1002/app.1959.070010108

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

年代:1959

数据来源: WILEY

摘要:

AbstractA new method for preparing plastic membranes with very small pores is described. The method involves dissolving two or more film‐forming polymers in a common solvent. A thin layer of the resulting solution is spread on a smooth surface and the solvent is allowed to evaporate. One of the polymers is then extracted from the resulting film with a selective solvent. The selective permeability of ethyl cellulose was altered considerably using polyethylene glycol as the second polymer. The apparatus for determining the permeability of these films is described. Pictures of the membranes at different stages in their preparation are shown. Electron micrographs demonstrating the effect of this treatment on ethyl cellulose are presente

ISSN:0021-8995    

DOI:10.1002/app.1959.070010109

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

年代:1959

数据来源: WILEY

摘要:

AbstractHigh polymers of ethylene oxide have been shown to have a number of unique properties in water solution. In this study, these properties have been investigated from the view of the behavior of large neutral molecules in media of high dielectric constant. Predictably, these high polymers of ethylene oxide undergo salting‐out effects which are reflected in changes of solution viscosity with salt concentration. Salts vary in effectiveness in a manner similar to that observed in the case of small neutral solute molecules. The salting‐out and viscosity effects are paralleled by the inverse solubility‐temperature relationship in water. Above a minimum molecular weight of about 50,000, the precipitation temperature (the temperature at which polymer separates from solution as a separate phase as the temperature is raised) becomes essentially independent of molecular weight. For these very high polymers the upper temperature limit of solubility in water is independent of polymer concentration over a wide range of concentration. These effects are discussed in terms of the balance of hydrophilic and hydrophobic character in the polymer structure which can be altered by increasing the hydrocarbon content of the polymer through copolymerization of ethylene oxide with other olefin oxides such as propylene oxide. This investigation permits the development of an interpretation of the unusual rheology of high molecular weight poly(ethylene oxide) in water sol

ISSN:0021-8995    

DOI:10.1002/app.1959.070010110

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

年代:1959

数据来源: WILEY