摘要:

Neutralization of carboxyl-terminated polybutadienes with tri-or tetravalent metal was carried out with different ratios of the corresponding neutralizing agents. The network structures of the prepared materials were investigated through their molecular, thermal, dynamic mechanical, and dielectric properties. The nature, the density, and the efficiency of the ionic interactions influence the solubility, the formation, and the thermal stability of the three-dimensional cross-linked ion-containing polymers.

ISSN:0022-2348    

DOI:10.1080/00222348708223944

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The use of concentrated polymer solutions is one of the basic techniques in the application of polymers. They may be coating materials, plasticized polymers, and oil-extended rubber. In these applications the solubility relation is one of the key requirements. The polymer-solvent interaction is expected to influence the mechanical property of the mixture. It is the intent of this study to explore how the dynamic mechanical property is affected by the change of thermodynamic interaction parameter in concentrated polymer solutions. The theoretical development is based on several assumptions: (1) a polymer chain in the amorphous state and in its own environment assumes unperturbed configuration; (2) a polymer chain in a good solvent (poor) is expanded (contracted) relative to the unperturbed dimension; (3) the expanded (contracted) chain configuration results in the higher (lower) entanglement density; (4) both expanded and contracted chains store an elastic energy, the magnitude of which may be estimated; (5) the elastic energy of the deformed chain is balanced by the thermodynamic energy of interaction. The paper focuses on the development of a theory. Also, limited examples of the application of the theory are presented.

ISSN:0022-2348    

DOI:10.1080/00222348708223945

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Changes in the structure of nylon 6 fibers annealed in dry and wet atmospheres were studied by small-and wide-angle x-ray diffraction. In the presence of water or saturated steam, fibers can be annealed to the same strucutral state at temperatures 70°C lower than in dry atmosphere. This is due to the enhanced mobility of the molecular segments in the amorphous region, a mechanism which is also known to lower the Tgby the same amount. Upon annealing under unconstrained conditions, lamellar spacing, crystallite size in the equatorial plane, crystalline as well as fiber density, and the chain-axis repeat increase with annealing-temperature; whereas crystalline orientation and the Van der Waals separation of the hydrogen-bonded sheets decrease. The monoclinic angle 8 remains constant at 66.7° (σ = 0.3°) and might depend on the starting fiber rather than on the treatment of the fiber. Most of these changes occur above a critical temperature of 170°C if dry, or 100°C if wet; rate of crystallization is also the highest under these conditions in nylon. The effect of these changes on such fiber properties as dyeing and the role of micro voids in dye diffusion and in dye uptake are discussed. Surface premelting and the accompanying changes in the surface structure of the lamellae, selective melting, and more importantly, the longitudinal motion of the nylon 6 chains and the resulting folding of interfibrillar extended amorphous chains are invoked to explain the shrinkage of the fiber, disorientation of the crystallites, increase in crystalline perfection, and the increase in lamellar spacing.

ISSN:0022-2348    

DOI:10.1080/00222348708223946

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Viscosity measurements of polyurethane anionomers were made in a number of solvents and mixed solvent systems at 25°C. At very low polymer concentration polyelectrolyte behavior was observed while at higher concentration ion-pair aggregation was noted in all cases. The metal ion, type of solvent and of polyol, and charge group concentration were varied to observe the effect on solution properties. These results show that the degree of dissociation of ion pairs depends on the polarity of the solvent and its solubility parameters. Conductivity measurements of alkali metal salts of polyurethane carboxylates were made in dimethylformamide at 25°C. For a given polymer the experimental specific conductance increases as the size of the metal ion increases. This is the same order that is observed for the ionic equivalent conductance of the metal ions.

ISSN:0022-2348    

DOI:10.1080/00222348708223947

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

By means of conoscopic and WAXS methods, the type of lamellar orientation in a LDPE blown film has been investigated. The WAXS diffractograms establish the existence of plane-axial texture, the crystallographic a axis of the unit cell being predominantly parallel to the machine-processing direction (the M axis) of the film. The conoscopic data indicate that the film as a whole behaves like an optically positive biaxial monocrystal, the plane of the film being a section perpendicular to the obtuse bisectrix. Comparison of the experimental data of both methods leads to the conclusion that the b and c axes of the unit cell may occupy any arbitrary position in a plane perpendicular to M.

ISSN:0022-2348    

DOI:10.1080/00222348708223948

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Flake-like fillers with various particle sizes (talc: 0.8, 3.3, 10.0, 25.5 μm; mica: 15, 32, 98, 320, 730 μm) were mixed with polypropylene (PP). The effect of flake-like filler properties such as filler aspect ratio, filler size, and filler content on the modulus of oriented PP composites was investigated. The relative modulus (Ecd/Erd, where Ecdand Erdare the modulus of oriented PP composites and the modulus of oriented PP, respectively) is shown to be determined by the following factors: (1) orientation factor of the PP matrix, (2) filler properties (filler content, aspect ratio, modulus), and (3) void properties (void volume, void length). The filler size dependence can be clearly recognized, showing an increase in Ecd/Erdas filler size decreased for PP/talc and PP/mica systems. In addition Ecd/Erdis dependent primarily on void volume, irrespective of filler size, aspect ratio, filler content, or orientation of PP matrix for PP filled with flake-like fillers.

ISSN:0022-2348    

DOI:10.1080/00222348708223949

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A formalism of computational chemistry methods is presented to estimate the stability of vinyl polymers. This approach takes into account changes in electronic energy upon polymerization using quantum mechanical methods and contributions of the conformational energetics of the polymerized state using a molecular mechanics force field. A work term, ΔV, based upon the molecular volume difference between the monomer and the reactant, is shown to be negligible. For 10 structurally diverse vinyl polymers, the sum of the electronic and conformational energy differences between reactant and monomer states, AEp, has a high linear correlation with corresponding measured enthalpies of polymerization, ΔHp. The linear regression least square fit is ΔHp = 0.89 AEp-13.39. Errors due to possible contributions to AHp not included in the formalism reported here are probably small and/or relatively constant over the set of polymers studied. If this were not the case, a linear correlation between AHp and AEp, with a slope near 1, would not be observed. Most likely the intercept of-13.39 kcal/mol is due to the choice of the quantum mechanical method used, MNDO. Overall, the formalism presented here seems a reliable means of predicting relative polymerization stability, in advance of synthesis, for a structurallycongenericset of polymers.

ISSN:0022-2348    

DOI:10.1080/00222348708223950

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In this paper a method proposed recently by Miller and Macosko is used for calculation of the network structure of a polyfunctional amine polymerizing with a bifunctional epoxy resin. Finite chain probabilities are derived for amine functionalities, taking the values of 5 and 6. The values of vcderived by this method are tested with those obtained from the equation for rubber elasticity. Some further assumptions for networks with short chains are made for both this method and the classical theory of rubber elasticity. A satisfactory approximation between theoretical and experimental values of vcis then obtained.

ISSN:0022-2348    

DOI:10.1080/00222348708223951

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor