摘要:

AbstractEquations are derived that relate the orientation of “pseudo‐affine” reoriented structural units after a biaxial deformation to the degrees and the directions of the effective drawings. The connection between these drawing parameters and those externally applied is analyzed in detail. It is shown how a comparison of these two sets of drawing parameters allows conclusions regarding the distribution throughout the material of the stresses that cause the deformation, the inhomogeneity of the deformation, and the role of non‐orienting flow during deformation. In particular, the orientation of biaxially drawn poly(ethylene terephthalate) films is investigated, and it is shown what general information can be obtained on the deformation behavior of this material on the basis of these conside

ISSN:0032-3888    

DOI:10.1002/pen.760271402

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractIn order to elucidate the flow behavior of electrophotographic toner systems, shear stress was measured as a function of shear rate in a cone and plate rheometer for polymer melts containing carbon blacks of surface area 24 and 625 m2/g at several concentrations and temperatures. Polymers included high and low molecular weight polystyrene and poly(butyl methacrylate). The addition of carbon black to the polymers caused a large increase in viscosity, especially at low shear rates and shear stresses. As the concentration of carbon black was increased, the viscosity at low shear rates became unbounded below a value of the shear stress designated the yield stress. The absolute magnitude of the yield stress depended primarily on the concentration and surface area of the carbon black and was independent of the polymer and temperature. Apparently, carbon black forms an independent network within the polymer at low shear rates which precludes flow. In some cases, the viscosity of polymers filled with carbon black was lower than that of the pure polymer. This effect was favored for polystyrene compared to poly(butyl methacrylate) and was facilitated by increasing the molecular weight of polystyrene, reducing the surface area and concentration of carbon black, and by increasing the temperature and shear rate.

ISSN:0032-3888    

DOI:10.1002/pen.760271403

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe rheological response of random copolymers of styrene and butyl methacrylate containing carbon black simulates the behavior of toner in the electrophotographic process. Both the relative viscosity and the dependence of viscosity on shear rate were increased by raising the temperature and raising the concentration and surface area of carbon black. For high concentrations and surface areas of carbon black and at elevated temperatures, a well‐defined yield stress varied from 2.5 × 102to 1.6 × 104Pa, depending on the concentration and nature of the carbon black but independent of the type of polymer and temperature, implying the formation of a carbon black network. Plasticization by carbon black was favored at low surface area and concentration of carbon black and at elevated temperatu

ISSN:0032-3888    

DOI:10.1002/pen.760271404

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractAn approach for modeling and simulation of multifilament melt spinning of poly(ethylene terephthalate) fibers is presented. It is shown that the quench conditions seen by the filaments within a bundle are not identical but differ for different rows of filaments. This, in turn, affects the spun fiber properties and introduces a degree of variability in the properties. The proposed approach allows determination of both the average properties and their variability for a given set of spinning conditions, spinneret geometry, and quench details.

ISSN:0032-3888    

DOI:10.1002/pen.760271405

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractScale‐up from small laboratory size extruders to large production size extruders is a procedure of great practical importance. Many scale‐up rules and theories have been proposed in the past, however it is not always clear how the different scale‐up methods will affect extruder performance. A basic analysis of scale‐up in plasticating single screw extruders is developed from which the effect of a certain scale‐up strategy on extrusion performance can be evaluated in terms of solids conveying, melting, melt conveying, mixing, residence time, heat transfer, power consumption, and specific energy consumption. Various existing scale‐up theories are evaluated and compared using the basic analysis. A number of existing scale‐up theories have some significant drawbacks, in particular with non‐constant specific energy consumption and imbalance between melting rate and pumping rate. Conditions that are desirable to achieve in scale‐up are enumerated and ranked in terms of importance. This leads to two new scale‐up methods that result in constant mechanical specific energy consumption and high throughput rates. The first scale‐up method keeps the specific surface area constant. This scale‐up should work well for high values of the Brinkman number. However, at low values of the Brinkman number, the melting rate may be insufficient. The second scale‐up method keeps the melting rate at low Brinkman number equal to the pumping rate and, thus, should be useful in cases where the first scale

ISSN:0032-3888    

DOI:10.1002/pen.760271406

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractNonisothermal flow of a polymer melt into a cold cavity and its rapid cooling give rise to the buildup of flow and thermal stresses in the molded article. In the present investigation the resultant residual stresses (RS) induced by these two sources were studied in two stages. First, the flow‐induced stresses were relaxed by proper heat treatment followed by quenching, resulting in only thermal stresses. The experimentally determined RS profiles in polysulfone and amorphous polyamide showed a parabolic shape and were correlated with the initial and final quenching temperatures, the glass transition temperature, and Biot Number. In the second stage, the combined effect of thermal‐ and flow‐induced stresses was studied using injection‐molded specimens prepared under a wide speptrum of molding conditions including melt and mold temperatures and injection rate and pressure. Results here indicated that the basic thermal‐induced parabolic RS profiles are altered by the flow‐induced stresses resulting in complicated profiles including local maxima and unbalanced RS. Finally, the tensile mechanical properties obatained for plaques molded under the various injection‐molding conditions were studied and correlated in part with the previously determined RS profiles. Results have shown that a property gradient exists as a function of distance from both the gate and surface of the

ISSN:0032-3888    

DOI:10.1002/pen.760271407

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe effect of die wall temperature on the flow of polymer melts in circular capillary dies was studied. At constant flow rates, it was found that die wall temperature had a greater effect on the pressure drop than melt temperature. A capillary die with two circular channels with different diameters was designed to simulate the profile extrusion. Changes of wall temperature varied the flow rate ratio between the two channels. An implicit finite difference method was used to simulate the velocity and temperature profiles inside the die. Values predicted by this model matched well with experimental data for both dies.

ISSN:0032-3888    

DOI:10.1002/pen.760271408

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe effect of die wall temperature on the extrudate swell of polymer melts flowing through dies with single and dual circular channels was studied. Extrudate swell was measured at constant flow rates using an Instron capillary rheometer with a modified die section. It was found that under isothermal conditions, extrudate swell plotted against the average wall shear stress gave rise to a temperature independent correlation for polystyrene. Under non‐isothermal conditions, such a correlation did not exist, which might be due to the change of wall shear stress in the axial direction. The extrudate swell in the non‐isothermal cases can be better correlated with the wall shear stress at die exit. For the two‐hole die, changes of die wall temperature varied both the flow rate ratio and the extru date swell ratio. The latter is, however, much less sensitive to the die wall temperature than the f

ISSN:0032-3888    

DOI:10.1002/pen.760271409

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe shear yielding processes in the deformation of biaxially oriented styrene‐acrylonitrile (SAN) copolymer films (machine oriented with draw ratio = 6.9 in the machine direction and 2.9 in the transverse direction) were studied. In the transverse direction, two sets of shear bands with an intersection angle of about 123.6 degrees (61.8 degrees with the tensile axis) were developed. When necking occurred, the bands in the necked region were thin and discontinuous with an intersection angle of about 81 degrees. In the machine direction, shear bands appeared to be short and diffused with an intersection angle of about 119.2 degrees. Only a slight necking effect was observed. The Luders strain in the transverse direction was about 0.56 and in the machine direction, about 0.16. The shearstrain‐volume of activation obtained from the strain rate dependence of shear stress was about 3440 ± 400 Å3in the machine direction and 2700 ± 500 Å3in the transverse direction. The work hardening behavior in both directions seemed to follow a linear relationship between 1n (tensile stress) and tensile strain at large strains. From a consideration of localized shearing toward tensile axis, the fraction of deformed materials was calculated. These observations indicated that (1) a strong orientation hardening effect existed in unbalanced biaxially oriented films, resulting from the difference of the amount of deformable materials between individual directions; and (2) deformation proceeded by shear banding with the high orientation direction involved more correlated molecular segments than the low orientation direction during the activation

ISSN:0032-3888    

DOI:10.1002/pen.760271410

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractPolymer‐filler redistribution is the process whereby a polymer melt with an initially homogeneous distribution of filler obtains an inhomogeneous distribution upon injection molding. The purpose of this paper is to develop a set of rules for predicting polymer‐filler redistribution. The predictions are based upon experiments on lateral particle migration in pseudoplastic fluids and theoretical calculations on lateral particle migration in second‐order fluids. Predictions are made concerning the existence of a “surface of accumulation,” the dependence of filler concentration on distance from the gate, and the effects of injection time and barrel temperature. The predictions compare favorably with experiments in a dumbbell specimen using polymers Luran 378P and Ultraniid B3, both containing gl

ISSN:0032-3888    

DOI:10.1002/pen.760271411

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY