摘要:

AbstractThe rheological behavior of aqueous solutions of Separan AP‐30®, polymethylcellulose, and polyvinylpyrrolidone was studied experimentally. These solutions exhibit non‐Newtonian flow behavior in simple shear, and are characterized by one of several 2, 3, or 4 parameter rheological equations. The equations used included the power law, the Ellis model, Spriggs equation, the Herschel‐Bulkley equation, and Meter's model. The power law model fits the data for each of the solutions over a limited range of shear rates, whereas the other models, which include either a lower shear rate limiting Newtonian viscosity, and/or an upper shear rate limiting Newtonian viscosity, or a yield stress, fit the data well over a wide range of shear rates from 0.00675 to 1076 sec−1. The pressure drop‐flow rate data for the same aqueous solutions flowing through packed beds were correlated well by the Ergun equation using the various rheological models applied in this work to evaluate a modified fluid viscosity. In each case it was found that the rheological model which best fit the viscometric data also gave the best packed bed friction factor correlation, and that no one model, such as the powerlaw, or the Ellis model, is the best one to use in all cases for all solutions. For polyvinylpyrrolidone solutions large deviations between experimental values of friction factor and those from the Ergun equation occurred for modified Reynolds numbers greater than one. A pseudo viscoelastic parameter was used to improve the friction factor correlation empirically at high Reynol

ISSN:0032-3888    

DOI:10.1002/pen.760151102

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractIn response to increasing ecological and economic pressures, a two‐shot molding process has been developed to recycle molding plastics. This process buries scrap plastic under a skin of virgin plastic in the molded part, resulting in a laminate that has the appearance of and similar mechanical properties to the skin material only. Two injection units and a special nozzle design are used to achieve the desired lamination. Theoretical and experimental studies have been conducted to determine the effects of parameters on the amount of scrap material that can be buried and its effect on impact strength. With conventional production molding dies, scrap plastic comprising approximately 40 percent of the total shot has been molded beneath virgin plastic in parts having stringent appearance requirement

ISSN:0032-3888    

DOI:10.1002/pen.760151103

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe use of fiber‐reinforced composites in structures is discussed with emphasis on the need for a method to obtain long time properties from short time tests. Results of vibration, constant strain‐rate and creep tests are presented for boron epoxy laminates. The data is statistically conditioned and a time‐temperature shifting procedure is used to obtain master curves for response at an individual temperature. Three analytical linear viscoelastic characterization techniques are used to obtain long term creep response from dynamic data. Comparisons between analytical predictions are given for vibration and constant strain‐rate data. Creep predictions are also compared to experimental obser

ISSN:0032-3888    

DOI:10.1002/pen.760151104

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe various materials used in biomedical applications, viz., metals and alloys, polymers, ceramics, and composites, are reviewed, and their respective areas of application discussed. Problems of compatibility with tissue and body fluids are reviewed and the performance of the various materials systems examined. Some examples of failure of implanted devices are shown, and the need for careful control of quality as well as of material specification is emphasized. Finally, the importance of close cooperation between medical, engineering and metallurgical specialists in this area is noted, together with the requirement of a better knowledge of materials on the part of the surgical personnel involved.

ISSN:0032-3888    

DOI:10.1002/pen.760151105

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe performance of cellulose acetate reverse osmosis membranes for desalination or purification is greatly affected by the microstructure of the membrane. It is, therefore, highly desirable to characterize the microstructure and its dependence on preparation conditions and past history. In this study, various types of cellulose acetate powders, flakes, and solvent cast films have been characterized by differential scanning calorimetry and thermo‐optical analysis. It is shown that ordered microstructures exist in many of these samples and that this ordering can be intensified or diminished by suitable treatments. It is conjectured that a similar microordering occurs in the dense layer of asymmetric cast membranes as a result of solvent evaporation, gelation and annealing and that the extent of orientation and chain packing in the ordered regions greatly affects the performance of reverse osmosis membrane

ISSN:0032-3888    

DOI:10.1002/pen.760151106

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe dynamic properties of a fiber‐reinforced composite under uniaxial sinusoidal stresses have been studied and the dynamic modulus and loss coefficients have been evaluated. Effects of fiber orientation to applied stress, the magnitude of static biaxial stresses, frequencies of fluctuating stresses and the temperature on the dynamic properties have been studied. The paper describes a dynamic biaxial testing machine specially developed for the measurement of dynamic properties of fiber‐reinforced materials for a low frequency range. Results indicate that the single laminate material displays very little damping. However, the multilaminate material reveals an appreciable damping that is dependent on the frequency of fluctuation of applied stress. The loss coefficient for the multilaminate material was found to decrease with frequency and was appreciably affected by fiber orientation, magnitudes of mean biaxial stresses, and temperature. Finally, an examination of data indicated that the time‐temperature equivalence hypothesis can be applied. Using this principle, master loss coefficient curves for an extended frequency range have been obt

ISSN:0032-3888    

DOI:10.1002/pen.760151107

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe non‐linear creep of polymeric materials under super‐imposed static and dynamic stress is considered theoretically. The equation of state due to Green, Rivlin, and Spencer to‐gether with the power law of time dependence for the kernel functions as suggested by Nakada is assumed to characterize the non‐linear materials. Expressions for creep strain under constant static, oscillatory dynamic and superimposed static and dynamic stress are obtained in terms of the material constants and time dependent functions, called dynamic creep functions. It is shown that the creep strain due to dynamic stressing is damped as the number of stress cycles is increased. Damping is faster if the power law of time dependence is high. Expressions for the cumulative creep strain after multiple stress cycles are also obtained in terms of cumulative strain functions. All these functions are evaluated numerically at one thousand stress cycles. Finally, a special case of stress history is considered where the stress periodically reaches zero. It is shown that the ratio of the strains due to dynamic and static stressing can be characterized by the power law parameter when the mean stress is either very high or very low. Due to the slow damping when the power law parameter is small, the decrease of the strain ratio with number of cycles is slow compared to higher power law par

ISSN:0032-3888    

DOI:10.1002/pen.760151108

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThree sets of data for the deformation of crystalline poly‐propylene in uniaxial tensile tests and uniaxial creep, in equal biaxial creep and in planar shear are examined. The methods of analysis used in the original papers, all based on variants of linear elasticity, are critically evaluated, and a constitutive equation based on the theory of a simple fluid with memory is propose

ISSN:0032-3888    

DOI:10.1002/pen.760151109

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760151101

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY