摘要:

Variations in viscosity, extrudate swell, and end correction were determined for natural Guayule rubber, natural Hevea rubber, and synthetic polyisoprene as a function of shear rate(10–104 s−1),temperature (120, 140, 160 °C), mastication time in a two‐roll mill (0, 5, 15 min), and carbon black load (30, 50, 70 phr). Viscosity decreases with shear rate, temperature, and mastication time and increases with carbon black load. Extrudate swell increases with shear rate and decreases with temperature, mastication time, and carbon black loading. End correction (for gums) increases with shear rate and decreases with temperature and mastication time. End correction (for blacks) increases with shear rate but the effect of temperature and carbon black loading are interrelated, as the effect of one depends on the magnitude of the other. Also, at constant shear rate and temperature, end correction for blacks is lower than for gums. Finally, viscosities for natural Guayule rubber are similar in magnitude to those of natural Hevea rubber and synthetic polyisoprene, whereas extrudate swell and end correction are somewhat higher for Guayule rubber than for Hevea and synthetic polyisoprene rubbers.

ISSN:0148-6055    

DOI:10.1122/1.549622

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

摘要:

The nonlinear behavior in simple shear of polyisobutylene solutions in cetane was studied for three concentrations in various shear histories. The concentrations of the solutions were 10, 15.1, and 19.3% by weight. Measurements of the shear stress and the first normal stress difference were obtained as a function of time at shear strain histories involving suddenly applied shear and stress relaxation after steady shear. Steady state values were also obtained for the shear stress and first normal stress difference as a function of shear rate, and the dynamic viscosity,η′(ω),and rigidity,G′(ω)were obtained as a function of frequency. Some isochronal data is also presented from single step stress relaxation experiments. It is shown that a simple superposition principle can be applied at concentrations where the intermolecular forces are predominant for the systems and for which the potential function in the Bernstein, Kearsley , and Zapas elastic fluid theory can be expressed as a product of a function of time and a function of strain. An excellent agreement was obtained with the experimental data, even for transient experiments where the shearing and normal stresses depend on time.

ISSN:0148-6055    

DOI:10.1122/1.549623

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

摘要:

Linear stability analysis is applied to the cylinder‐plate and wedge‐plate problems. Necessary conditions for the solution to exist are obtained. These conditions give bounds on the number of ribbing lines at given capillary number and spacing. The results are compared with previous numerical work for the cylinder‐plate problem. It is shown that a simple theory accurately predicts the distance at which the meniscus is formed for the wedge and plate problem. The technique can be generalized to other coating processes such as roll coating.

ISSN:0148-6055    

DOI:10.1122/1.549624

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

摘要:

Squeezing flow between two disks with lubricated surfaces was found to generate a homogeneous compression or equal biaxial extension in a high viscosity polydimethylsiloxane sample. The apparatus is extremely simple: two steel disks with a central rod to provide alignment and prevent sample slip, an LVDT to measure displacement, and a silicone oil bath. The mass and area of the upper disk provide for a constant force boundary condition. The biaxial viscosity was found to be approximately six times the shear viscosity over biaxial extension ratesε̇rfrom 0.003 to1.0 s−1.Lubrication could be achieved up to Hencky strains of about 2.5. Some data were also taken on the same polyisobutylene sample used by Stephenson and Meissner in their biaxial stretching study. Agreement was very good.

ISSN:0148-6055    

DOI:10.1122/1.549648

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549649

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549625

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549656

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549655

出版商:The Society of Rheology    

年代:1981

数据来源: AIP