bluuebunny/crossref_metadata_2025_split huggingface dataset:
Creep failure and fracture of polyethylene in uniaxial extension
Authors: Crissman J. M. , Zapas L. J. 
Published: December 2004

AbstractIt is shown that under conditions of uniaxial creep the fracture of high density polyethylene can be categorized as one of three types, depending upon the magnitude of the applied load, molecular architecture, and environment. When subjected to relatively large loads, the specimens neck and then fracture almost immediately. At the other extreme of very small initial loadings, the specimens fracture in a brittle fashion through crack formation and growth. In the intermediate range of loadings the specimens neck and, depending upon the molecular weight and molecular weight distribution, may then elongate substantially before fracture. It is shown that the uniaxial creep behavior for the region where drawing occurs, when plotted in terms of isochrones, represents a type of phase diagram, one boundary of which describes the fracture enelope. In addition, experiments employing different constant rate of loading histories are described and an additivity of damage criterion used to predict the time to failure under constant load conditions, and visa versa.
An instability leading to failure of polyethylene in uniaxial creep
Authors: Zapas L. J. , Crissman J. M. 
Published: December 2004

AbstractBased on a continuum model, a point of instability is predicted for the uniaxial creep of high density polyethylene. From dead load experiments it has been found that the instability occurs for linear polyethylene at around 10–12 percent strain, depending upon molecular weight and molecular weight distribution. It is shown that in the range of applied stresses for which the specimens neck during uniaxial creep, the time required to reach the critical point is related by a constant factor to the time at which the neck appears. A synopsis of theoretical considerations, as well as experimental work in support of this idea, is given.
A comparison of the thermal and mechanical degradation of glassy polystyrene by Fourier transform infrared spectroscopy
Authors: D'Esposito L. , Koenig J. L. 
Published: December 2004

AbstractThe thermal and mechanical degradation of glassy polystyrene has been studied by Fourier Transform Infrared, FT‐IR, spectroscopy. Using difference spectroscopy we have found that the products formed from these two modes of degradation were significantly different. This result is in contrast with other workers who found similar products for the thermal and mechanical degradation of polystyrene by mass spectroscopy. Our result suggests a reassessment of the thermal activation mechanism for mechanically‐induced bond scission. We have also found that the distribution of oxidation products appears to depend upon the environment in which the polymer is mechanically degraded. Finally, we have demonstrated the utility of FT‐IR spectroscopy for studying the mechanical degradation of polymers.
The adhesion to hydrophilic surfaces of plasticized poly(vinyl chloride) containing novolac ‐ hexamethylenetetramine
Authors: Robertson Richard E. 
Published: December 2004

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 thickness per 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.
Studies on poly(vinyl chloride)‐copper composites. Part 1: State of segregation of filler particles, electrical and mechanical properties in presence of plasticizer and stabilizer
Authors: Bhattacharyya Swapan K. , De Sadhan K. , Basu Sanjay 
Published: December 2004

AbstractThe presence of additives influences the state of segregation of filler particles in the polymer matrix which in turn controls the electrical and mechanical properties of poly(vinyl chloride)‐copper composites. The liquid plasticizer seems to form a coating on the filler surface which introduces quasirandomness in the segregated network. In accordance with the mathematical model proposed earlier, the strength properties were found to be proportional to dm−½ where dm is the mean free path between the filler particles. Calculations of dm were based on two different models, one for segregated network (unplasticized and low plasticized composites) and the other for quasi‐random distribution of filler particles (plasticized composites). Extruded samples in general show more randomness in the filler distribution than the compression molded samples.
The selection and use of free radical initiators
Authors: Sheppard Chester S. , Kamath Vasanth R. 
Published: December 2004

AbstractThere are over 50 different organic peroxides and azo compounds (in over 100 different formulations) produced commercially as free radical initiators (curing agents) for the polymer and resin industries. Thus, the user has many initiators to choose from and has usually relied on the resin and/or initiator producer to select his initiator system. This paper will discuss these initiators in general showing the different types‐ of initiator classes; how and why the activity of each class of initiator is varied by structure changes; how different initiators and/or promoter levels affect the curing process; and present guidelines that an end user might use to choose the right initiator for his resin system.
Fracture toughness testing of dental biomaterials
Authors: Koblitz F. F. , Luna V. R. , Glenn J. F. , Devries K. L. , Draughn R. A. 
Published: December 2004

AbstractThe adaptation of a cylindrical geometry fracture toughness test specimen to testing of polymeric dental biomaterials is demonstrated. The specimen configuration facilitates the fabrication of small specimens and simplifies the experimental study of environmental effects on properties of dental biomaterials. The test method is used to measure critical stress intensity factor, KIC for poly (methyl methacrylate) (PMMA), particulate composite restorative materials, and dental polymers. Values obtained are in agreement with data reported for other specimen configurations.
Extrudate swell from slit and capillary dies: An experimental and theoretical study
Authors: Huang David C. , White James L. 
Published: December 2004

AbstractA comparative experimental study of extrudate swell from long slit and capillary dies is reported for rheologically characterized polystyrene and polypropylene melts. Generally extrudate swell from a slit is greater than that from a capillary die. At low die wall shear rates it goes to a value of about 1.2 as opposed to about 1.1 found for capillary dies. The onset and character of extrudate distortion have been studied. The experimental results are compared with theories of swell based on unconstrained recovery from Poiseuille flow in these geometries. A detailed analysis of such theories of extrudate swell based on the original work of Tanner has been carried out. The analysis is placed in a more general form which should be valid for a range of die cross‐sections.
Fluid transport in thin film polymer processors
Authors: McKelvey James M. , Sharps G. Vincent 
Published: December 2004

AbstractAn analysis of fluid transport in a polymer processor consisting of a hollow vertical cylinder with rotating blades is presented. The action of the rotating blades causes a thin film to be deposited on the inner surface of the processor and a bow wave to form in front of the blade. Fluid transport through the processor depends upon flow within the bow wave. Three types of flows are identified as contributing to the fluid transport: flow under the influence of a pressure gradient, flow due to gravitational force, and drag flow due to the action of the rotating blades. Equations describing these flows are derived as well as an equation for the bow wave profile. Experimental data in good agreement with the theoretical development are presented.
Thermoset and coatings technology: The challenge of interdisciplinary chemistry
Authors: Roller M. B. 
Published: December 2004

AbstractModem thermoset and coatings technologies provide the challenge of combining in situ polymer synthesis and processing with the task of characterizing an insoluble, intractable product. During the last dozen years several tools have been developed in J. K. Gillham's Princeton Laboratory which provide insight into this complex interrelationship. Although not necessarily conceived exclusively for thermoset characterization, these tools have been found to be uniquely suited to the task. To be discussed are the application of the torsional braid analyzer, a programmable pyrolyzer and thermal analysis to the study of coatings and thermosets in general. Also included is a discussion of a time‐temperature phase diagram for the thermoset analysis and the study of the formation of spiral and helical cracks in reinforced thermosets.
Equation of state of cis‐1,4‐polybutadiene melt
Authors: Jain R. K. , Simha Robert 
Published: December 2004

AbstractRecent equation of state data are analyzed in terms of the hole theory of polymer melts. The good agreement between experimental and theoretical volume‐temperature curves at atmospheric pressure, observed previously for a number of amorphous and crystallizable polymers, is again confirmed. Similarly, satisfactory theoretical results for the isotherms ensue, with deviations however becoming noticeable at elevated pressures and low temperatures. The linearity of the isochores observed experimentally is confirmed by the theory, however with somewhat different slopes. Departures of maximally 10 percent from the thermal pressure coefficients derived from the experimental PVT data are noted. Significant differences between theory and experiment apper only in the third derivatives of the partition function, as has also been observed with other pollymers. The characteristic scaling parameters of volume, temperature and pressure show the expected similarity with hevea rubber. Earlier correlations for scaling entropy and segmental volume with scaling temperature are found to be valid within the scatter of these relations. Finally, the applicability of the empirical Tait equation in the form applied to the equation of state in other polymer melts is confirmed. Although the resulting thermal pressure coefficient exhibits an explicit even if smal dependence on temperature, in disagreement with experiment or theory, the Tait equation remains a useful relation for the representation of PVT information.
Laser degradation of polymer coatings on reflective heat sinks
Authors: Cozzens Robert F. , Fox Robert B. , Echols William H. 
Published: December 2004

AbstractThe 10.6 μm laser‐induced degradation and volatilization of thin non‐char forming organic polymer coatings on aluminum heat sinks has been investigated. Volatilization rates were determined from coating absorptivities measured as a function of irradiation time at 110 W/cm2. First order volatilization rate constants (kJ−1) were: poly(ethylene‐co‐ethyl acrylate) 0.30, polystyrene 0.85, poly(ethyl methacrylate) 1.6, poly(methyl methacrylate) 2.1, and nitrocellulose 3.1. Residual coating thicknesses at infinite irradiation time are reported. Degradation results from exposure to the thermal environment provided by the heat sink as well as by the direct absorption of laser radiation. Relative polymer thermal stabilities measured at this laser irradiance level and by conventional heating methods are in agreement.
Simultaneous interpetrating network based on castor oil elastomers and polystyrene. III. Morphology and glass transition behavior
Authors: Devia N. , Manson J. A. , Sperling L. H. , Conde A. 
Published: December 2004

AbstractElectron microscopy and dynamic mechanical spectroscopy (DMS) techniques were used to study the morphology and glass transition behavior of simultaneous interpenetrating networks (SIN's), based on three different castor oil derived elastomers, and polystyrene (PS) plastic erosslinked with 1 percent divinyl benzene. The castor oil elastomers consisted of either the sebacic acid polyester, 2,4‐tolylene diisocyanate polyurethane, or the mixed poly(ester‐urethane). Emphasis was placed on two compositions having 10 and 40 percent elastomer contents by weight of each type, the remainder being PS. In all cases, a two‐phase morphology emerged. With the 10 percent elastomer composition, the use of vigorous stirring during the early stages of reaction resulted in materials having the crosslinked polystyrene as the continuous phase and elastomer domains (ranging from 100 to 8000 nm in size) as the discontinuous phase. The elastomer domains contained a polystyrene cellular structure, with the polystyrene cell sizes ranging from 50 to 300 nm size. Several examples showed morphologies resembling high impact polystyrene. Materials having a 40 percent elastomer content always showed a continuous phase of castor oil elastomer, with the PS displaying a bimodal size cellular structure. Domain sizes ranged from 10 to 860 nm. The DMS studies showed two well‐defined glass transitions near their respective homopolymer glass transitions, but shifted inwards to greater or lesser extents indicating some molecular mixing between the two polymers. The glass transition of the pure elastomer phase occurred at −66°C for the castor oil polyester elastomer, −4°C for the castor oil polyurethane elastomer and −50°C for the castor oil poly(ester‐urethane) elastomer. Phase separation in these materials is postulated to occur by two mechanisms: (1) multiple precipitation of polystyrene chains at progressive levels of polymerization and (2) microsyneresis processes. The thermodynamics of mixing and phase separation in polymerizing SIN's is examined in some detail.
Heat transfer in blow molding operations
Authors: Edwards M. F. , Suvanaphen P. K. , Wilkinson W. L. 
Published: December 2004

AbstractA one‐dimensional model of unsteady state heat conduction has been applied to the cooling and solidification of a polymer in a blow molding process. The approach includes a temperature‐dependent specific heat term to account for latent heat effects during the phase change. The model is used to predict temperature profiles in a thick‐walled component of high‐density polyethylene. These profiles lead to a clearer understanding of the heat transfer process. It is further shown that these temperature distributions can be used to study the influence of the major process variables upon the cooling of the molded component.
Aluminum/carbon fiber hybrid composites
Authors: Hancox N. L. , Wells H. 
Published: December 2004

AbstractAn effective, economic way of using carbon fiber is to combine it with a resin and another material, either a fiber or a metal, to produce a hybrid structure. Some of the properties of a hybrid beam made by attaching carbon composite to either side of an aluminum channel section are described here. The structure has considerable potential in the orthotics field; the aluminum core assists in the forming of, for instance, orthoses (calipers), modifies the failure characteristics of the carbon fiber composite, and eases the problem of jointing and adjustment of finished articles. Difficulties can arise when combining carbon composites and metals because of differences in thermal expansion behavior. To alleviate these effects a urethane modified epoxide resin matrix, which has very good adhesive properties, was employed. The work covers measurements of strength and modulus, evaluation of the aluminum/aluminum bond strength, and the flexural fatigue performance.
Coupling of optical and mechanical properties in crystalline polymers
Authors: Seferis James C. , Samuels Robert J. 
Published: December 2004

AbstractThe modules and birefringence of oriented polymers are known to couple through the structural and intrinsic properties of the polymer. Recent developments in both optical and mechanical theories have allowed this coupling to be expanded so that it includes predictions of modulus and refractive indices of uniaxially‐oriented polymer films at various angles to the draw direction. The validity of these theories has been tested in this study by predicting the angular dependence of the optical and mechanical properties of seven uniaxiallyoriented films of isotactic polypropylene. The present study also provides intrinsic material properties associated with the crystalline and noncrystalline components of the polymer, and consequently allows the identification of the structural parameters that control the properties of ultra‐high oriented isotactic polypropylene.
The modulus of the amorphous component in polyethylenes
Authors: Boyd Richard H. 
Published: December 2004

AbstractVarious approaches to representing the modulus of a semicrystalline polymer as a composite crystal‐amorphous material are applied to the extensive data of Illers on the shear modulus of linear and branched polyethylenes as a function of crystallinity and temperature. It is found that the modulus of linear polyethylene is fit very well over the range of 47‐96 percent crystallinity from − 180 to 100°C by the Tsai‐Halpin equation with a single value of the contiguity factor, ζ, and crystallinityindependent phase moduli. A value of ζ ≃ 1(near lower bound behavior) is found. In branched polyethylene the behavior below the β relaxation (T < Tβ) is similar to linear polyethylene, but above Tβ, the behavior indicates that the amorphous modulus is crystallinity dependent. The amorphous component modulus as a function of temperature for linear polyethylene extracted from the fitting process is discussed in terms of various interpretations of the relaxations (α, β, γ) in polyethylene.
An overview of amorphous chains in block and segmented copolymers: Their influence on bulk structure and material properties
Authors: Wilkes G. L. , Mody P. C. , Tant M. R. 
Published: December 2004

AbstractThe influence of amorphous chains on bulk structure and material properties is examined in block and segmented copolymer systems whose components are in a variety of morphological states including: rubber‐rubber; rubber‐glass; glass‐glass; rubber‐crystalline glass‐crystalline; and, crystalline‐crystalline. The effects of external variables, such as temperature, time, and internal variables, such as molecular weight and composition ratio on the magnitude of the role played by the amorphous chains in these systems are discussed.
Effects of lubricants on the second fusion behavior of rigid polyvinyl chloride
Authors: Logan Mark S. , Chung Chan I. 
Published: December 2004

AbstractRigid polyvinyl chloride (RPVC) is thermally unstable and difficult to process. The processibility of RPVC compounds markedly depends on the type and level of lubricants present. Lubricants are compounded into RPVC powder and the resulting dry blend is either directly converted into the final product requiring the resin to fuse only once, or pelletized first followed by conversion into the final product in a subsequent operation requiring the resin to fuse twice. The effects of lubricants on the first fusion have been well studied but little is known about the second fusion. We studied the effects of eleven common lubricants on the second fusion of a RPVC master, batch at three levels of concentration at several temperatures., The lubricants were compunded with the RPVC powder, the dry blends molded into one‐inch cube samples, and the molded samples fused under shearing conditions comparable to the actual processing. We found that the effects of the lubricants on the second fusion were generally the same as those on the first fusion. Apparently, the properties of the lubricants and their interactions with the RPVC resin are not altered by the first fusion history.
Polymer flow in the clearance between closely spaced candle filter elements
Authors: Trentacosta J. D. 
Published: December 2004

AbstractA mathematical model for polymer flow in the clearance between high‐resistance filter elements is developed. An analytical solution is obtained for pressure and velocity profiles for Newtonian fluids. A numerical solution is obtained for elastic fluids displaying power‐law behavior in viscosity and entrance pressure loss. Elasticity of the polymer melt or solution is shown to be a significant factor in, determining these profiles. An example of the model's application, using rheological data for a commercial polyethylene, is given, and the impact of clearance flow pressure losses on the mechanical side loading of the filter elements is discussed.
How the morphology of poly (vinyl chloride) compounds affects toughness and weatherability
Authors: Summers James W. , Isner James D. , Rabinovitch Elvira B. 
Published: December 2004

AbstractSuspension polymerized poly (vinyl chloride) (PVC) is made up of 150 μm grains. Within these grains are 2 μm primary particles which apparently become the flow units under low melt temperature (175°C) extrusion conditions. The 2 μm particles are visible by light transmission microscopy by shearing the extruded product between glass slides after swelling in acetone or by electron transmission microscopy of ultrathin microtomed samples. This product, made up of 2 μm flow units, is brittle and has poor toughness retention upon weathering. At higher melt temperatures (185–190°C), agglomeration of the 2 μm particles occurs, giving a rough surface but tougher product. At higher melt temperatures, a continuous melt occurs, leading to a smooth surface and tough product with excellent toughness retention upon weathering.
Dissolution dynamics of some polymers: Solvent‐polymer boundaries
Authors: Ouano A. C. , Carothers J. A. 
Published: December 2004

AbstractA critical angle illumination microscopy technique was used to study the in situ dissolution dynamics of polystyrene, poly (α‐methylstyrene) and the two tactic forms of poly (methyl methacrylate), (PMMA), in several solvents. The dissolution characteristics; of polymers were found to be greatly influenced by several factors: type of polymer, processing condition of the sample, type of solvent, and tacticity, Polystyrene was found to exhibit extensive swelling in several solvents while atactic PMMA exhibited extensive cracking on dissolution. Isotactic PMMA, which has a glass temperature of about 70°C lower than the atactic PMMA, showed swelling behavior similar to atactic polystyrene, while the α‐methylstyrene showed the cracking phenomena exhibited by atactic PMMA.
Preparation and properties of high modulus–tensile strength polymeric materials
Authors: Peiffer Dennis G. 
Published: December 2004

AbstractA two stage drawing procedure is described for producing highly oriented polymeric materials. The high orientation of both the crystalline and amorphous phase in the semi‐crystalline materials studied resulted in the materials possessing high mechanical properties. The ability to obtain high amorphous orientation is critical. Tensile strengths of 16 g/denier for polyethylene are determined, for example. The results suggest that the existence of a prominent crystalline dispersion mechanism (as observed in dynamical mechanical studies) is not necessary for the attainment of high mechanical properties. Thus a method was devised for the determination of the optimum drawing temperature.