摘要:

Dielectric dispersions were measured for a semiflexible polymer, poly (n‐hexyl isocyanate) (PHIC), in dilute through concentrated, isotropic solutions. Since PHIC has a dipole moment parallel to the chain contour, its dielectric dispersion reflects the fluctuation of the end‐to‐end vector of the polymer. For lower molecular weight PHIC samples with rodlike nature (the Kuhn statistical segment numberN≤0.53), the dispersion for the permittivity ε’and the loss factor ε‘almost obeyed the simple Debye relation irrespective of the polymer concentrationc, and thecdependence of the dielectric relaxation time τDwas favorably compared with the fuzzy cylinder model theory. On the other hand, for higher molecular weight PHIC samples (N≥0.69), the dispersion curves for ε’and ε‘deviated from the Debye relation and thecdependence of τDdid not agree with the prediction of the fuzzy cylinder model theory. These disagreements may ascribe to the chain flexibility effect for the higher molecular weight samples.

ISSN:0148-6055    

DOI:10.1122/1.550721

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

The isothermal crystallization of poly (phenylene sulfidesulfone) (PPSS) fromN‐methylpyrrolidone (NMP) solutions has been monitored by a viscoelastic technique. We have observed four characteristic changes which occur with increasing time in 20 wt % solution at 24 °C; (i) a decrease in η*, (ii) a steep increase inG’, (iii) a slight decrease in η*, and (iv) an increase in η* andG’. These changes indicate the crystallization process from a nucleation to an aggregation. Further, the crystallization at several temperatures and of poly (ethylene terephthalate) (PET), poly (butylene terephthalate) (PBT) melts was measured similarly. It was found that the rate of crystallization of PPSS from NMP solutions is very slow, and its temperature dependence is very small.

ISSN:0148-6055    

DOI:10.1122/1.550671

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Viscoelastic flow at a region of a circular pipe entrance was examined numerically. The numerical calculation was achieved by using I.C.E. (implicit continuous‐fluid Eulerian) technique with the K‐BKZ type constitutive equation. The transient flow characteristics with the sudden stand‐up were obtained. The resultant flow field and its associated flow parameters of the K‐BKZ integral constitutive equation were compared with the Newtonian case and the Oldroyd‐B model. It is revealed that flow is largely affected by a choice of the Deborah number. When the Deborah number is high enough for a fixed Reynolds number, there would be a circulation zone at the entrance region of the pipe by the effects of the viscoelasticity, which cannot be observed with the Newtonian flow.

ISSN:0148-6055    

DOI:10.1122/1.550673

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Heterogeneous textures due to phase separation in molten polypropylene (PP)/ethylene–propylene–rubber (EPR) blends were investigated in relation to their dynamic viscoelastic properties. As characteristic to heterogeneous liquids, slow relaxation mechanisms due to the existence of such phases were found for dynamic moduli of PP/EPR blends. These moduli were analyzed by using the linear viscoelastic constitutive equation for an emulsion model developed for the concentrated emulsion and the blending equation for dissimilar polymer system. The results show that the matrix of PP/EPR blends is not pure PP but the mixture of PP and EPR. For the same blend composition, the EPR concentration in the matrix PP phase was larger for EPR containing more propylene units. For the blends having the same EPR, the EPR concentration in the matrix was larger for higher EPR content.

ISSN:0148-6055    

DOI:10.1122/1.550675

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Heterogeneous textures in phase separated, solid polypropylene (PP)/ethylene–propylene–rubber (EPR) blends were investigated in relation to their dynamic viscoelastic properties. The glass transition temperature (Tg) of amorphous PP phase in PP/EPR blend quenched from molten state varies with propylene content of EPR as well as EPR content in blend. TheTgdepends on the concentration of EPR dissolved in the amorphous PP phase. On the other hand, theTgof EPR phase in PP/EPR blend is about the same as that of pure EPR. This fact means that PP molecules were not dissolved in EPR phase. For the same blending composition, the EPR concentration in matrix PP phase was larger for EPR having more propylene units. When the same EPR was used, the EPR concentration in the matrix was larger for blends with larger EPR content. The EPR concentration in the amorphous PP phase of PP/EPR blend in solid state is about the same as that in molten state, indicating that the EPR concentration in solid state was essentially determined by the EPR concentration in molten state.

ISSN:0148-6055    

DOI:10.1122/1.550676

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

For the past 30 years, the author has been conducting research on the mechanics of rubber elasticity and fibrous materials. This article presents a historical review of the development of the research. The author’s first research project was an investigation of thickness irregularity in fiber bundles. This irregularity is caused by the random arrangement of the short fibers that form the bundle, and increases during the drafting of the bundle in the spinning process. The author presented a theory that made it possible to predict the power spectrum of this irregularity. This research stimulated the author’s interest in the mechanics of fiber assembly bodies, also known as ‘‘fibrous materials.’’ This interest remains strong today. After completing his first research project, the author spent a year at the California Institute of Technology, in Pasadena, where he initiated research on rubber elasticity as a basis for research on the failure behavior of solid rocket propellant. He has developed a biaxial extension experiment for rubbers, and found a simple form of the strain energy density function for these rubbers. Parallel with this research on rubber elasticity, the author continued research on the deformation mechanism of fibrous materials such as yarns and woven and knitted fabric structures. On the basis of this research, the author developed an objective evaluation of fabric hand; evaluations had previously been made by a subjective method called ‘‘hand judgment.’’ There is a similarity between research on the mechanics of rubber and research on the mechanics of fibrous materials. The research deals with the assembly body of molecular chain or fiber and have been carried out with an interactive concept. The author has also introduced his recent research on the measurement of anisotropy in the mechanical property of single fibers. This measurement was conducted with a micromeasurement instrument developed by the author. Some of the results of these measurements are also presented here.

ISSN:0148-6055    

DOI:10.1122/1.550677

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

The relationship between rheological behavior and structures of styrene–butadiene (PS–PB) diblock copolymers was examined in a PB‐selective solvent,n‐tetradecane (C14). At low temperatures the behavior of concentrated PS–PB/C14 micellar solutions was dominated by plasticity due to a macrolattice of micelles. Thermodynamic confinement (balance of elastic and osmotic requirements) on corona PB blocks led to macrolattice formation. Differing from the PS–PB/C14 solutions, blends of PS–PB and homo‐PB chains did not suffer from the confinement and exhibited linear viscoelastic relaxation that was retarded by entanglements of PB blocks. In further investigation of entanglement dynamics, constraint release (CR) relaxation in PS/PS binary blends was found to be reasonably but not completely described by a Rouse‐type CR model. This model was further examined for dielectric relaxation of polyisoprene (PI) chains having dipoles parallel to the chain contour. Specifically, eigenfunctions associated with a local correlation function were evaluated from dielectric data of dipole‐inverted PI chains. Those eigenfunctions were nonsinusoidal, most clearly exhibiting non‐Rouse nature of actual CR processes.

ISSN:0148-6055    

DOI:10.1122/1.550718

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

摘要:

Measurements of pressure at representative points in a converging–diverging channel were carried out for viscoelastic liquids of aqueous solutions of poly‐ethyleneoxide (PEO) and polyacrylamide (PAA) as well as for Newtonian liquids. The pressure drop at the section of converging channel and the pressure rise at the section of diverging channel were simultaneously measured for various flow rates. The experimental results indicate that (i) magnitudes of both pressure drop and rise for the PEO solution increase with increasing PEO concentration, and the pressure characteristics are similar to those of Newtonian liquids, (ii) the pressure characteristics of the PAA solution are significantly different from those of Newtonian liquids when the PAA concentration is increased. The differences seem to be due to elasticity of the PAA solution.

ISSN:0148-6055    

DOI:10.1122/1.550727

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.550679

出版商:The Society of Rheology    

年代:1995

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.550680

出版商:The Society of Rheology    

年代:1995

数据来源: AIP