摘要:

AbstractConsiderable effort has been expended recently by a number of researchers to develop methods of simulating the flow of polymers in injection molding dies. The computer models developed by these researchers provide the mold designer with useful quantitative information concerning the predicted effect of design parameters on mold, filling characteristics. This paper will describe some recent work which is aimed at increasing the usefulness of these models by more accurately describing the flow behavior of those polymers, such as polycarbonate resins, which exhibit a strong effect of pressure on viscosity.

ISSN:0032-3888    

DOI:10.1002/pen.760190702

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractIn the last ten years, a considerable amount of work has been conducted on many different processes distinct from common plastics processing methods such as injection molding, extrusion, and compression molding. Perhaps the most common feature of these new techniques is that they resemble more the methods used for fabricating metallic materials in solid phase. However, there is a lack of uniform terminology. More importantly, the commercial acceptance and applicability of these processes have been slow. This review attempts to summarize the important findings of various publications and, whenever possible, to give information about potential or actual industrial applications. The purpose is to provide a brief overview of the state‐of‐the‐art of the whole technology. Advantages, disadvantages, and the need for more work are pointed out as they relate to different processes and to crystalline and amorphous materials. A few instances where material was heated beyond the melting temperature by a small amount are included in the review when the processing method was similar to solid‐phase

ISSN:0032-3888    

DOI:10.1002/pen.760190703

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThis paper examines the important dimensionless numbers that control emulsion polymerization in a tubular reactor. It was found that the activation energy of polymerization was of major importance, while the role of monomer diffusion was not very significant. By selecting certain combinations of the dimensionless numbers, changes occurring during scaleup from a small tubular diameter to a larger diameter can be approximated.

ISSN:0032-3888    

DOI:10.1002/pen.760190704

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe addition of relatively small amounts of novolachexamethylenetetramine phenolic to poly(vinyl chloride) plastisols has been used to increase the adhesion of the fused plastisol to hydrophilic surfaces like those of glass and steel. The principal mechanism by which this occurs has been studied and found to be, first, the dissolution of the novolachexamethylenetetramine complex in the plasticizer; second, the interaction of the nearby phenolic groups with the hydrophilic surface; and, third, the chain extension and crosslinking of the phenolic to form perhaps a very open cell foam structure through the plasticized vinyl that is attached to the substrate. Additional adhesion may arise from the adsorption of particles of the undissolved novolac complex on the surface and from viscoelastic effects from the cured vinyl composition. The problem with the decreased adhesion of thin plastisol coatings was also studied. It was found to be unrelated to the thicknessper se. Rather, it seems to arise from the loss of hexamethylenetetramine at the air interface. Though hexamethylenetetramine is lost also from thicker coatings, the concentration near the adherend interface is less affected.

ISSN:0032-3888    

DOI:10.1002/pen.760190705

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA comparison of experimental data for zero strain Young's modulus of uniform density thermoplastic foam for short times has been made with several theoretical and empirical correlations. An analysis of the variance of the data with the predicted values from the many models indicated that the simplistic density squared relationship adequately described the modulus of the foam for basic engineering calculations.

ISSN:0032-3888    

DOI:10.1002/pen.760190706

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe manufacture of pellets from extruded plastic strands is modeled as a constrained nonlinear programming problem. The objective is to maximize the production rate by choice of pellet dimensions and pelletizing machine operating parameters. A general solution strategy leading to identification of a globally maximum production rate for any numerical case is given. It is shown that increases in the maximum production rate can be obtained by selective relaxation of the constraints. A numerical example is presented and discussed.

ISSN:0032-3888    

DOI:10.1002/pen.760190707

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractA theoretical and experimental investigation has been conducted of the transverse tensile properties of flexible‐resin/ glass‐fiber composite lamina. The objective is to increase the elongation at failure of a lamina in a state of transverse tension so that when a lamina is used in a laminate configuration, it does not suffer premature failure (e.g., failure at a lower strain level than that for a lamina in fiber direction tension). We show that the mode of failure in the transverse tensile lamina differs greatly from that in the neat resin. The failure mode in the lamina form is found to be brittle fracture. From this, it follows that the controlling neat resin property is the low elongation modulus rather than the elongation at failure. Significant improvements in the transverse tensile strain at failure were obtained for the flexible‐resin/glass‐fiber systems

ISSN:0032-3888    

DOI:10.1002/pen.760190708

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe rate of fatigue crack propagation in graphite fiber reinforced nylon 66 was measured. A model of the form å = β [Kmax1‐γΔKγ]rwas used to correlate the rate of crack propagation å with the maximum stress intensityKmaxand the amplitude of the stress intensity ΔKexperienced by the notched specimen during the fatigue test. The quantities β, γ andrwere constant at fixed temperature and frequency of the test. It was also found that there exists both an upper and a lower threshold of stress intensity for the slow ropagation of damage during fatigue. The mechanism of crack propagation in the short graphite fiber reinforced nylon was found to be similar to the growth and fracture of crazes in thermoplastics. The propagation of damage at the crack tip is controlled by matrix deformation, cavitation, fiber breakage and fiber pullout. Damage can propagate in the absence of crack growth until a critical point is reached at which time the material fractures catast

ISSN:0032-3888    

DOI:10.1002/pen.760190709

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe mechanical behavior of compatible glassy polyblends based upon poly(2.6‐dimethyl‐ 1,4‐phe nylene oxide) (PPO) was investigated. In particular, the influence of composition, molecular weight, and molecular weight distribution upon the tensile modulus of the blend was assessed. Various possible correlations between the experimentally determined moduli and theory are considered. Included are correlations with density, packing density, composite theory, and lattice fluid theory. The modeling of the properties of mixtures via Simplex lattice design is also presented. Finally, attention is given to the development of compatibility criteria based upon tensile modulus and density measure

ISSN:0032-3888    

DOI:10.1002/pen.760190710

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThis paper arose from a study of the use of polymeric materials to protect humidity‐sensitive items from damp ambient conditions. A one‐dimensional model for the Fickian diffusion of moisture through a permeable wall into a volume of air is considered. The humidity in the airspace asymptotically approaches equilibrium with the exterior, and the time constant is defined as the time to reach 1–1/eof its ultimate value. Exact and approximate solutions are considered. Depending on the system geometry and properties, the time constant is either permeability‐controlled or diffusivity‐controlled, or somewhere in between. Under certain conditions, there exists an optimum combination of airspace depth and wall thickness that maximizes the time

ISSN:0032-3888    

DOI:10.1002/pen.760190711

出版商:Society of Plastics Engineers, Inc.    

年代:1979

数据来源: WILEY