摘要:

AbstractThe solid‐state properties of a highly crosslinked amorphous resole‐type phenolic polymer have been studied by compressibility and torsional braid analysis measurements. Three secondary transitions were found over the temperature range of 123° to 623° K the largest of which occurs at about 393°K. These results confirm previously made electrical resistivity and specific heat measurements. These transitions are discussed in relation to the structure of this p

ISSN:0021-8995    

DOI:10.1002/app.1977.070210111

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe yield, composition, and molecular weight of homopolymers and copolymers of β‐pinene and styrene are described as a function of the feed, temperature, and solvent. Fractionation, gel permeation chromatography, and nuclear magnetic resonance spectroscopy of GPC fractions are used as analytical tools to present evidence for copolymerization in methylene dichloride. Additional support for copolymerization is obtained from the relation of polymer composition to percent conversion. The reduction of molecular weights of homopolymers by aromatic solvents was investigat

ISSN:0021-8995    

DOI:10.1002/app.1977.070210112

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

年代:1977

数据来源: WILEY

摘要:

AbstractStress–strain behavior of some starch xanthide‐ and carbon black‐reinforced styrene–butadiene elastomers was investigated as a function of filler particle size and structure. In starch xanthide systems, low strain behavior is sensitive to particle structure; high strain behavior, to particle size. Electron photomicrographs of the several starch xanthide‐reinforced vulcanizates were analyzed with reference to filler particle size and structure. These parameters were then correlated with Mooney plots of [load/λ − λ−2] versus λ−1, where λ is the strain ratio. Plots of samples containing highly structured filler particles were highly nonlinear, rising steeply as λ−1approached unity. Samples containing nonstructured filler particles were also highly nonlinear, rising steeply as λ−1decreased to approximately 0.4. A preliminary study of the dynamic properties of these samples, as determined in an eccentric rotating‐disk rheometer, provided li

ISSN:0021-8995    

DOI:10.1002/app.1977.070210113

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

年代:1977

数据来源: WILEY

摘要:

AbstractAn explicit reduced equation of state is developed by combining results of the hole'theory with a semitheoretical expression for the temperature dependence of the reduced Tait parameterB̃which is found to be in good agreement with experiment. This approach circumvents the implicit character of the theoretical equations.Two procedures are explored to derive for a given system the PVT surface and the compressional energy and entropy changes from the corresponding reduced functions. One rests on the usual superposition of experimental and analytical isotherms and isobars. The other, and more approximate method, utilizes a correlation between the scaling temperatures, pressures, and volumes obtained previously, and requires only experimental data at atmospheric pressure and a single temperature above the glass transition (Tg) or the melting temperature (Tm). The good agreement between experiment and theory noted previously is shown to extend to the semiempirical relationships. Finally, internal pressure data for oligomers and polymers at atmospheric pressure and encompasing a wide range of reduced temperatures are examined. The ensemble of data can be described by simple power relationships between the internal energy and the density. The exponents, however, depart significantly from the van der Waal's value of unity

ISSN:0021-8995    

DOI:10.1002/app.1977.070210114

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe morphology of porous polysulfone hollow fibers which were spun by the dry–wet spinning process is discussed. It was demonstrated that a relatively moderate quenching medium should be employed in the bore of the nascent fiber in order to produce an isotropic fiber free of macrovoids and intrusion cells. A rather delicate quantitative balance between the internal precipitant and the spinning solution has to be maintained, especially when low‐viscosity polymeric solutions are employed. Scanning electron micrographs of fiber cross sections display highly porous, spongestructured walls which in some instances exhibit a rather dense interface skin. However, control of the extrusion/coagulation procedure allows the formation of skinned, porous skinned, and nonskinned fib

ISSN:0021-8995    

DOI:10.1002/app.1977.070210115

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

年代:1977

数据来源: WILEY

摘要:

AbstractUnlike most crystallizable polymers, some polyalkylbenzimidazoles do not crystallize when pure but do crystallize with ionized solvent molecules to produce solid stoichiometrical, solvated crystals. The polymer–solvent interaction is strongly exothermic, and a crosslinked polymer swells in the solvent over hundredfold. This leads to a negative χ1 value for the system. The cocrystallization with stoichiometric amounts of ionized solvent cannot be examined on the assumption that it is a polyelectrolyte gel since ion mobility is precluded. It also cannot be treated according to the corresponding states theory since the latter does not allow for negative χ1. A theoritical derivation, originating from Flory's semiflexible chain treatment, apparently predicts and explains the behavior of the polyalkylbenzimidazole–solvent s

ISSN:0021-8995    

DOI:10.1002/app.1977.070210116

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

年代:1977

数据来源: WILEY

摘要:

AbstractTwo methods of calibrating gel permeation chromatography columns are given. The first method uses polymer standards that may have broad molecular weight distributions. Either the weight‐, number‐, or viscosity‐average molecular weight of each standard must be known. This method neglects column peak spreading. The second method requires polymer standards of moderately narrow molecular weight distributions for which both the weight‐ and number‐average molecular weights are known. However, the second method determines both the column peak spreading and calibration of the column. The second method is applied to calibration of a column using polystyrene standards. The column peak spreading is found to be small and independent of molecular weight for th

ISSN:0021-8995    

DOI:10.1002/app.1977.070210117

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe formation of membranes from two systems has been studied. In the system polyurethane–dimethylformamide–water, the mechanism for the formation of the sponge‐like structure proves to be a liquid–liquid phase separation with nucleation and growth of the diluted phase. This mechanism has been confirmed for the system modified polystyrene–polyisoprene–polystyrene/o‐dichlorobenzene/(methanol–water). Crystallization and gelation is discussed. The membranes prepared showed hyperfiltration activity. The mechanism proposed here is believed to be valid for oth

ISSN:0021-8995    

DOI:10.1002/app.1977.070210118

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

年代:1977

数据来源: WILEY

摘要:

AbstractA Chemical research on the flame retardancy effect of halogenated phosphates on poly(ethylene terephathalate) fabric was carried out by thermogravimetry, infrared spectral analysis, and mass spectrometry. The following conclusions were drawn: (1) The flame retardancy effect of halogenated phosphates such as tris(2,3‐dibromopropyl) phosphate is due to altering the pyrolysis reaction of polyester by aldol condensation. (2) The probability that liberated halogen compounds from the phosphates act as radical acceptors in a flame zone may be low. (3) Incorporation of halogen elements into phosphates appear to depress evaporation of phosphates, which act as acidic catalysts in aldol condensation from the condensed phas

ISSN:0021-8995    

DOI:10.1002/app.1977.070210119

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe Hildebrand and the Hansen solubility parameters of the aromatic and the aliphatic ester residues of poly(ethylene terephthalate), PET, are evaluated and compared to those determined experimentally. The interactions of nonaqueous solvents with the aromatic and aliphatic ester residues of PET are also described in terms of their relative basicity and acidity in the Lewis sense, where the aromatic residue may be taken as a Lewis acid and the aliphatic ester residue may be taken as a Lewis base.

ISSN:0021-8995    

DOI:10.1002/app.1977.070210120

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

年代:1977

数据来源: WILEY