摘要:

AbstractDistortion of bars injection‐molded from polystyrene, polypropylene, and glass‐fiber‐filled polypropylene and subsequently placed in a temperature gradient has been examined. Residual stress distributions have been measured both for the as‐molded state and after annealing in a temperature gradient. In the as‐molded state all moldings showed the usual residual stress distribution with compressive stresses near the surface and tensile stresses in the interior. In all three materials it was found that tensile stresses could be developed near to the warmer surface on gradient annealing and that tensile stresses still remained at this surface when the bar was cooled and permitted to bend to restore internal equilibrium. It is shown therefore that in addition to the dimensional changes which occur and which may render the molding unserviceable after temperature gradient annealing, another undesirable change takes place, leaving the molding much more susceptible to fracture from a surface flaw. Uniform annealing is found to be much less likely to cause stress reversal and the stresses remain balanced so that distortion i

ISSN:0032-3888    

DOI:10.1002/pen.760240402

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractPoly(p‐phenylene terephthalamide) (PPD‐T) films have been prepared by continuous extrusion of liquid crystalline 17 percent PPD‐T/sulphuric acid solutions through an annular die followed by coagulation, Films extruded without drawdown exhibit some polymer chain orientation in the machine direction. This is increased by uniaxially drawing down films. Films produced with a lubricated conical mandrel sitting between the die and the coagulation bath exhibit an equal biaxial orientation. The uniaxially oriented films exhibit highly anisotropic mechanical properties, while the mandrel‐produced film exhibits balanced properties. Heat treatment at 350°C results in significant enhancement of the tensile strength of the mandrel film. Void structures in the films have been investigated by mass density, scanning electron microscopy (SEM), and small‐angle X‐ray scattering (SAXS). Density measurement indicate a void content decreasing with decreasing film thickness and heat treatment. SEM locates micron‐size voids in the thickest films, apparently caused by rapid coagulation. SAXS indicates much smaller void sixes which are roughly prolate ellipsoids (long axis in machine direction) for uniaxial films and oblate ellipsoids (short axis in thickness direction) for the mandrel produced films. Various techniques are used to estimate

ISSN:0032-3888    

DOI:10.1002/pen.760240403

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe performance of liquid rubbers as low‐temperature plastcizers for bitumen was evaluated by the torsional braid technique developed by Gillham. The low‐temperature dynamic mechanical properties of bitumen‐liquid rubber mixtures were measured from ambient to −100°C and compared with the corresponding fracture behavior using a modified Fraass test. Microscopic observation of the mixture revealed that the liquid rubber was partially soluble in the bitumen at 23°C and at concentrations greater than 10 percent tended to form colloidal dispersions of rubber particles having mean diameters of approximately 10 μm. The loss tangent maxima shifted to lower temperatures and became less pronounced as the concentration of liquid polybutadiene increased. The colloidal rubber dispersion further contributed to the ductility and reduced the brittle temperature of the bitumen at −30°C at 20 percent liquid rubber concentration. The reduction in the brittle temperature of the bitumen is related to the glass‐transition temperature of the added rubber, those rubbers having, the lowest glass‐transition temperatures being most efficient. Such modifications are necessary to reduce the tendency of asphaltic paving materials to crack

ISSN:0032-3888    

DOI:10.1002/pen.760240404

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThree blown‐film‐grade low‐density‐polyethylene (LDPE) resins were studied using different rheological techniques. Eccentric rotating disks (ERD), cone‐plate viscometry, capillary rheometry, annular die extrusion, and non‐isothermal stretching of a filament were used. The viscoelasticity of the melts was found to play a dominant role in the observed behavior. Extrudate appearance in annular flow, melt strength, and extensibility are affected by melt elasticity. A correlation was found between the maximum draw ratio of a filament stretched under non‐isothermal conditions and minimum f

ISSN:0032-3888    

DOI:10.1002/pen.760240405

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe tensile behavior of low‐density polyethylene‐isotactic polypropylene blends was investigated at room temperature. Neck formation and propagation along the whole length of the samples were observed for the whole range of composition. This behavior, which is not indicated by most data available in the literature, was examined in relation to sample morphology by scanning electron microscopy. The results of this investigation indicated some differences between the morphology of these materials and the morphology of blends which do not undergo necking propagat

ISSN:0032-3888    

DOI:10.1002/pen.760240406

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThis paper investigates three aspects of linear‐low‐density polyethylene (LLDPE) rheological properties: shear viscosity variations with shear rate and temperature, tensile behavior determined with an extensiometer, and extrusion defects. The differences in shear viscosity variation with shear rate and temperature between LLDPE and LDPE (low‐density polyethylene) are shown. These differences, attributed to wider molecular weight distribution and to long chain branching (LCB) in LDPE, involve different extrusion behaviors. The lack of LCB in LLDPE can be demonstrated by comparison of the measured Newtonian viscosity with the value of the same parameter calculated from molecular weight distribution and composition law of Newtonian viscosities. The lack of LCB leads to good melt extensibility, which is shown by tensile properties of polyethylene melts determined with a non‐isothermal extensiometer. The melt fracture phenomenon is studied because it promotes surface defects on bubbles in film application. Extrudate distortions are examined at the laboratory extruder outlet. This test shows differences between LLDPE and LDPE, but also between some LLDPE

ISSN:0032-3888    

DOI:10.1002/pen.760240407

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe absorption of water vapor by propellants based on hydroxy‐terminated polybutadiene and an isocyanate from atmospheres of increasing relative humidities, and the swelling index of the propellant which had absorbed various proportions of water, were measured in an attempt to establish the extent of hydrolytic damage. The method was found incapable of assessing such damage, but it was shown that there was no measurable absorption of vapor below 92 percent relative humidity (RH). The MEK/polymer and toluene/polymer interaction parameters were determine

ISSN:0032-3888    

DOI:10.1002/pen.760240408

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractPoly(vinyl chloride) (PVC) and its blends with polybutadiene‐acrylonitrile (NBR) (containing 21.7 weight‐percent acrylonitrile (AN), a heterogeneous two‐phase system; and containing 41.6 weight‐percent of AN, a homogeneous one‐phase system) and with polyethylene‐vinyl acetate (EVA) (containing 45 weight‐percent of vinyl acetate (VA), a heterogenous two‐phase system; and containing 65 weight‐percent VA, a homogeneous one‐phase system) were UV‐irradiated (at 3500 Å UV‐light (solar spectrum)). After UV irradiation the kinetics measurements were made of the formation of hydroperoxy (OOH) and carbonyl (CO) groups and the changes of mechanical properties: tensile strength, elongation to break, and impact energy. As a result of the photooxidative degradation of PVC blends, decreases of mechanical properties were observed. The effects are more severe in PVC/NBR blends, which contain unsaturated bonds (polybutadiene segments) than in the case of PVC/EVA. The phase structure plays an evident role on the UV degradation only of PVC/NBR blends. The photostability of PVC blends can be slightly improved by introducing Tinuvin P or Ni

ISSN:0032-3888    

DOI:10.1002/pen.760240409

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractInverse gas chromatography (IGC) has been used to investigate thermodynamic miscibility of a molten poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blend. Toluene, benzene, and chloroform have been employed as probes in pure and mixed stationary phases of these polymers. Experimental measurements have been taken over a narrow range of temperatures because of the high PMMA glass transition temperature as well as the degradation of the PEO. The interaction parameter χ23determined at 150°C is slightly negative and dependent on the interacting probe, as has been also noted in previous chromatographic studies on polymer‐polymer miscibility. The last section is devoted to a model calculation, using Flory's equation of state theory. Different χ23‐concentration curves have been simulated, with the interaction energy parameterX23as an adjustable par

ISSN:0032-3888    

DOI:10.1002/pen.760240410

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760240401

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY