bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the time‐temperature‐viscosity behavior of curing B‐staged epoxy resin
Authors: Roller M. B.
Published: December 2004

The work described herein was initiated in order to generate resin characterization data that could describe a B‐staged epoxy material via the viscosity‐time‐temperature interactions that are inherently related to the nature of thermoset processing. The technique of chemorheology is explored as a means of characterizing the viscosity‐time‐temperature behavior of the B‐staged epoxy resins. The resins studied are typical of those available as glass‐impregnated prepreg bonding sheets used to manufacture multilayer printed wiring boards. The B‐staged resins were characterized isothermally at various curing temperatures. Their isothermal behavior was correlated via an empirical viscosity expression in the form of a dual Arrhenius model. Experiments were then conducted in a nonisothermal temperature mode, measuring viscosity as a function of both time and temperature. The viscosity model was taken into the nonisothermal temperature mode by introducing a time‐temperature integral. Good correlations between measured and predicted dynamic viscosity profiles are presented. Deviations are explained in terms of resin chemistry. The generalizations of behavior are discused. Calculations are presented which allow the comparison of the various B‐staged resins in terms of their viscosity behavior under the influence of an actual lamination thermal profile.
Reproducibility of stress‐cracking test results
Authors: Roe R. J. , Gieniewski C.
Published: December 2004

The environmental stress crack resistance of polyethylene is measured most conveniently by the bent‐strip method described in ASTM D‐1693‐70. The method has, however, suffered from poor reproducibility of test results. In this work we have carefully studied the effect of individual experimental variables that enter the test method. The effects considered are: the thermal history of test specimens; uncontrolled variations in the test procedures such as the sample holder width, the specimen thickness, and the stress relaxation occurring during the test; and the variability in the test results arising from the statistical nature of fracture process. It is concluded that each of the following four factors, when not properly controlled, could contribute an apparently random variation of a factor of two or more in the test results. These are (1) the aging of polyethylene specimens at room temperature, (2) the width of the specimen holder, (3) the dimensions of the tools employed for bending and transferring specimens, and (4) statistical fluctuations of the final results arising from the limited number of specimens tested and also from the stress relaxation occurring in the specimen during the test. By carefully controlling these and other variables, it should be possible to design a test procedure which is expected to yield results of a known precision and can serve even as a research tool.
Mechanical properties of discontinuous fiber reinforced thermoplastics. II. Random‐in‐plane fiber orientation
Authors: Blumentritt Bruce F. , Vu Ban T. , Cooper Stuart L.
Published: December 2004

The mechanical properties are presented for a series of discontinuous fiber‐reinforced thermoplastic composites made with random‐in‐plane fiber orientation. The matrix and fiber materials were chosen to provide a wide range of strength, modulus, ductility and adhesive properties. In many cases strong, rigid, yet tough composites were fabricated. Strength levels of over 20,000 psi and modulus values over 1,000,000 psi were reached in several systems reinforced with short Kevlar‐49 and graphite fibers. A strong dependence of composite strength and modulus on fiber strength and modulus was noted indicating good transfer of load from matrix to reinforcement. Fiber efficiency factors for modulus and strength were calculated for the experimental composite systems and averaged 0.19 and 0.11 respectively. Data were analyzed using basic composite theory. Properties of the experimental composites could not be predicted from constituent properties.
Residence time distribution in twin‐screw extruders
Authors: Todd David B.
Published: December 2004

Twin screw extruders are finding increased usage in reacting and devolatilizing applications. Using self‐wiping profiles, the twin screws fulfill the requirement that there be no “dead” or “unmixed” zones. Agitator design must be chosen with care so that a reasonable balance can be obtained between forwarding rate, surface‐generation rate, vapor passageway, power, and axial mixing. Techniques have been developed for measuring residence time distributions and characterizing axial flow behavior. The method also permits direct determination of the holdup in starved barrel applications. Data on residence time distribution are presented for 4‐in. diameter twin screw equipment with a variety of rotor configurations.
An experimental study of sandwich injection molding of two polymer melts using simultaneous injection
Authors: White James L. , Lee Biing‐Lin
Published: December 2004

An experimental study of two phase flow of polymer melts relating to injection molding has been carried out. The experiments specifically concern rheological phenomena which may occur when two melts are simultaneously injected through a runner system leading to a mold cavity. Injection in the form of annulus‐core configurations and simple stratified flow are investigated. A new injection molding method is proposed which is based upon the latter technique. Encapsulation of one melt by the other occurs in the runner system and formation of a sandwich structure in the cavity results. Annulus‐core injected configurations were only found to be stable when the lower‐viscosity melt is in the annular region.
Environmental effects on deformation, strength, and degradation of unidirectional glass‐fiber reinforced plastics. I. Survey
Authors: Ishai Ori
Published: December 2004

This survey covers the topic of environmental effects on the mechanical behavior of fiber‐reinforced plastics. It deals also with the separate and combined effects of temperature, hygrometry and loading on mechanical characteristics. The response of the phases of the composite‐fiber, the matrix and the interfacial region to the environmental loading history, is discussed. Conflicting hypotheses regarding the causes and mechanism of the degradation process and of the long‐range durability of the composites are examined.
Predicting toughness of impact thermoplastics from high‐speed tensile data
Authors: Fenelon Paul J.
Published: December 2004

A photographic procedure is presented for evaluating uniaxial true stress‐true strain tensile behavior of thermoplastics at strain rates typical of impact situations. The advantage of combining this information with observed macroscopic material changes which occur during tensile deformation is discussed in terms of establishing parameters which define end use abuse resistance of impact thermoplastics. In particular, test parameters are evaluated which provide a direct correlation with measured bottle drop failure resistance for selected materials. These test parameters are obtained by measuring the area under true stress‐true strain curves obtained at impact strain rates. Area is measured up to the point of ultimate uniaxile tensile strain. Ultimate uniaxial tensile strain corresponds to either (a) strain at onset of necking in materials which produce necking during deformation, or (b) strain at fracture in materials which deform without necking. Measured test parameters are discussed in terms of modern theories of strength of materials. Pitfalls associated with quantitatively defining the abuse resistance of thermoplastics based on total energy for breaking, i.e., conventional numeric criterion of impact strength, it also discussed.
Mold‐filling studies for the injection molding of thermoplastic materials. Part II: The transient flow of plastic materials in the cavities of injection‐molding dies
Authors: Lord H. A. , Williams G.
Published: December 2004

A practically‐oriented computer model which computes the temperature, pressure, and velocity fields in a cavity during the mold filling portion of the injection molding process is described. The model is structured so that it can be used for cavities having non‐simple shapes and for commonly used molding compounds with complicated viscosity, shear rate, temperature relationships. Predictions from the model are found to be in good agreement with results obtained from exact solutions to special cases. Model predictions in molding problems have been found to correctly describe trends such as an increase in the pressure required to fill molds as injection rate, shot temperature, and mold temperature decrease, and to be reasonably accurate when compared to data for plaque, disc, and telephone housing molds over a wide range of molding conditions. Some illustrative examples of the use of the model in solving real molding problems are provided.
Asymmetric loading of bonded rubber cylinders
Authors: Sims D. F.
Published: December 2004

Elastomeric bearings which consist of cylindrical rubber layers bonded on their inner and outer curved surfaces to metal cylinders are investigated theoretically and experimentally. Emphasis is placed on two asymmetic loading modes, radial loading and bending or tilting moments. An approximate theoretical treatment based on linear elastic behavior is proposed. Experimental spring constants are compared to the theoretical predictions for thin elastomer layers of various lengths. It was found that for highly confined layers, the theoretical spring constants must be modified to obtain agreement with experimental results. The importance of elastomer bulk deformation, shrinkage stresses from elastomer cure, and tension‐compression stress‐strain behavior is also evaluated.
The effect of interlayers on the transverse stresses in fiber composites
Authors: Arridge R. G. C.
Published: December 2004

Numerical results are given of calculations of the radial, transverse, and shear stresses in the matrix surrounding a cylindrical inclusion in plane strain perpendicular to the cylinder axis, this being taken as a model of a fiber composite under transverse loading. It is shown that the presence of an interlayer on the fiber at a thickness which is a small fraction of the fiber diameter can significantly affect the stress concentrations in the matrix. The interlayer‐fiber ‘composite’ can be ‘matched’ to the matrix by suitable choice of interlayer elastic moduli. In particular, if the shear modulus of the interlayer is smaller than that of the matrix and its Poisson's ratio is very small, the stress concentrations in the matrix are considerably reduced and the composite should be less subject to failure by delamination.
Thermal expansion transients of a cis‐1,4 polybutadiene elastomer at various levels of strain
Authors: Caruthers J. M. , Cohen R. E.
Published: December 2004

The length‐temperature behavior of elongated elastomeric networks of cis‐1,4 polybutadiene was observed following abrupt, nearly step‐function changes in the temperature of the specimen environment. The thermal expansion behavior is reversible, and the transient length changes are in the direction anticipated from rubber elasticity theory, i.e., dL(t)/dT is negative. The observed long‐time values of the thermal expansion coefficient are in good agreement with equilibrium length‐temperature coefficients reported for other elastomers. Results indicate that both thermal diffusion and retarded creep deformation contribute to the transient phenomenon, with the latter mechanism dominating.
Silicone‐polyethylene blends
Authors: Falender James R. , Lindsey Sarah E. , Saam John C.
Published: December 2004

Polyethylene and reactive, high molecular weight polydimethylsiloxanes have been blended under conditions of shear and elevated temperature in order to form uniform, thermoplastic blends. The materials can be extruded, coated on wire, injection molded, or compression molded. Despite the thermoplastic nature, a high gel fraction is present. A structure is proposed consisting of microgelled and grafted particles of silicone dispersed in polyethylene. When compared to pure polyethylene, the blends show lowered modulus over a temperature range of −150 to +65°C increased gas permeability, and lowered mixing energies. Electrical properties include corona resistance superior to polyethylene and a resistance to degradation under conditions simulating those experienced by buried cables superior to typical silicone rubber. Other electrical properties are intermediate between the values observed in the component polymers.
Experimental studies on the biaxial extensional viscosity of polypropylene
Authors: Hoover Kenneth C. , Tock Richard W.
Published: December 2004

For fabrication processes such as blow molding, vacuum forming, film blowing and fiber spinning, extensional flow is the dominate mode of melt deformation. Under these conditions, extensional viscosity is a significant rheological property. Thus, the biaxial extensional viscosity was measured for several samples of polypropylene. A technique based on the bubble inflation method of Denson and Gallo was used. Experimental values of biaxial extensional viscosities ranging from 1014 to 1010 poise as a function of strain rate, 10−5 to 10−2 reciprocal seconds, were obtained at 25°C. The technique used was critiqued and found to be useful in characterizing unoriented and biaxially oriented films, Uniaxially oriented films gave unsatisfactory results. It may be possible to use this testing method to assist in materials selection decisions.
The morphology of fibrous polymeric crystals formed isothermally in stationary shear fields
Authors: George Waller , Tucker Paul
Published: December 2004

A discussion is presented of the morphology of the fibrous crystals, shish kebabs, produced in an initially simple shear flow. When the crystallizable Component of the fluid is sufficiently dilute one usually finds along the stream line at the end of the large scale fibrous crystal, a continuation of that structure which consists of an extremely fine sequence of morphological entities. This fine row structure appears to have transverse dimensions comparable to and slightly greater than the resolution power of the transmission electron microscopical methods used in its observation.

Certain tentative suggestions were made regarding the nature of the shish kebab morphology. These are based upon a loose application of general results in the field of irreversible thermodynamics. This leads to the suggestion that the morphological nature of the row structure which has been generally observed in fibrous crystallizations may find its explanation in the nature of the local manner in which the associated entropy production is balanced while preserving a global state of stationary deformation with its associated lack of global entropy production.
Bubble growth in thermoplastic structural foams
Authors: Hobbs S. Y.
Published: December 2004

The inflation and growth kinetics of bubbles in thermoplastic structural foams are discussed in some detail using a model which assumes the initial existence of very small voids in the pressurized polymer melt. The effects of a drop in external pressure, the presence of a distribution of bubble sizes, and the diffusion of gas between neighboring bubbles are considered. It is shown that at a given pressure the number of growing bubbles present in the melt at any onetime depends on the ratio of the critical radius to the average radius of the microvoids assumed to be present in the melt It is also demonstrated that gas diffusion between neighboring bubbles reduces the growth rate appreciably only when the interbubble distance is reduced to a micron or less.
Some new aspects of the crystallization of bisphenol‐A polycarbonate
Authors: Gallez F. , Legras R. , Mercier J. P.
Published: December 2004

This paper concerns the action of plasticizers and nucleating agents on the crystallization of bisphenol‐A polycarbonate. The influence of plasticizers is to increase the rate of crystallization to a great extent using 10 percent of a plasticizer such as trimellitic acid, tridecyloctyl ester. The influence of nucleating substances on plasticized and undiluted polycarbonate is investigated. A large number of substances have been found capable of nucleating polycarbonate crystallization. The un‐plasticized semi‐crystalline polycarbonate is characterized by a much higher melting point (300°C) than the plasticized semi‐crystalline systems (210–245°C). The stability of bisphenol‐A polycarbonate in the presence of nucleating salts is also examined. We observe a substantial decrease in the molecular weight in the presence of a great number of nucleating substances. The modulus‐temperature curves of two semi‐crystalline polymers are reported in the last series of experiments.
Structure‐property relationships of isomeric addition polyimides containing nadimide end groups
Authors: St. Clair Anne K. , St. Clair Terry L.
Published: December 2004

Addition polyirnide oligomers with nadimide end groups (I) have been synthesized from 4,4′‐oxydiphthalic anhydride and 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride with several isomeric diamines and, nadic anhydride. The low molecular weight amic acid? and corresponding imides were isolated and characterized. Solubility and melt‐flow properties of the imide prepolymers were studied to determine the applicability of the resins as adhesives and composite matrices. Thermomechanical transitions of the polymers were obtained by torsional braid analysis. Properties were compared with a similar addition polymer, P13N. magnified image
The Halpin‐Tsai equations: A review
Authors: Affdl J. C. Halpin , Kardos J. L.
Published: December 2004

The Halpin‐Tsai equations are based upon the “self‐consistent micromechanics method” developed by Hill. Hermans employed this model to obtain a solution in terms of Hill's “reduced moduli”. Halpin and Tsai have reduced Hermans' solution to a simpler analytical form and extended its use for a variety of filament geometries. The development of these micromechanic's relationships, which form the operational bases for the coniposite analogy of Halpin and Kardos for semi‐crystalline polymers, are reviewed herein.
The elastic constants of a particulate‐filled glassy polymer: Comparison of experimental values with theoretical predictions
Authors: Smith Jack C.
Published: December 2004

Calculation of the elastic constants of a participate composite material in terms of the elastic constants of the filler and the matrix is discussed. The theories of Kerner or Hashin and Shtrikman, the equivalent theories of Budiansky and Hill, and a generalized van der Poel type theory are presented and discussed. Data from several sources are compared with the predictions of these theories. The van der Poel theory provides the best agreement and gives good values for volume fractions of filler up to 0.35.
Hot‐melt adhesive bonding of polyethylene with ethylene copolymers
Authors: Yamakawa S.
Published: December 2004

The melt bon debility of ethyl en e copolymers to a high, pressure polyethylene has been investigated by a T‐peel test consisting of polyethylene–copolymer–polyethylene. The three ethylene copolymers involved separately vinyl acetate, ethyl acrylate, and acrylic acid. The ethyl acrylate copolymers produce the highest peel strength over the test temperature range of −20 to 50°C, and also yield a high peel strength even at the bonding temperatures of 105–110°C, at which the welding of polyethylene to polyethylene does not occur. The observations of cross sections of the joints with an interference microscope show the presence of an interfacial boundary layer and a mixed layer (of the polyethylene and the copolymer). The relationship between the peel strength and these two layers is discussed. Further, the peel strength‐temperature curves are compared with the tensile properties of the copolymers.
Computer‐aided optimal melt screw design
Authors: Helmy H. A. A. , Parnaby J.
Published: December 2004

The paper describes a computer software package applying a steady‐state hill‐climbing optimization routine to the plastics melt‐extruder screw constrained‐design problem. The purpose primarily is to introduce the optimal screw‐design technique, to show how it is applied to this particular type of problem, to indicate its potential and to encourage its wider use. Screw performance criteria are defined by a theoretical model consisting of the non‐Newtonian isothermal polymer flow equations in terms of the screw‐geometric variables for particular process conditions. The design method is quite general however and a non‐isothermal model may be substituted. Use of the method offers considerable scope and potential for the design engineer to make design processes faster, more positive and logical while reducing the effort required. Interactive use is possible and empirical adjustments can be incorporated with experience. In using the method, the design engineer first specifies the required process conditions of pressure and flow rate at the die and the computer then searches for the set of screw design variables which optimizes the screw power utilization efficiency or any other specified criterion of performance. Such optimal designs are obtained within the set limits of practical constraints on machine dimensions, screw strength and product quality requirements. Some experimental evidence is given relating to the accuracy of the isothermal non‐Newtonian polymer flow model and to its use in the design of small diameter extruder screws. The optimal search technique offers considerable potential as a computer‐based design tool.
A crystalline ethylene, acenaphthylene, n‐hexene‐1 terpolymer exhibiting both high modulus and high elongation
Authors: Bailey F. E. , Walter E. R.
Published: December 2004

Polyolefins are generally known either as partially crystalline thermoplastics or as elastomers. With the finding in the ethylene‐acenaphthylene copolymer system of the unusual properties of high crystallinity, high modulus, and no independent beta thermomechanical transition at high comonomer contents, it appeared that it might be possible to prepare a block polymer system which would retain the desirable low temperature transition near −110°C and “hard” acenaphthylene copolymer segments as well. Attempts were made, and the resulting terpolymer is described. An intermediate crystallinity polymer of apparently broad composition distribution was obtained with the modulus of high density polyethylene but the elongational characteristics of low density polyethylene.
Effect of matrix ductility and interface treatment on mechanical properties of glass fiber mat composites
Authors: Gaggar S. K. , Broutman L. J.
Published: December 2004

The influence of matrix properties on randomly oriented glass fiber epoxy composites has been studied. It is shown that an increased ductility (flexibility) of the matrix does not result in greater elongation to failure of the composite under tensile and flexural loads. The tensile (and flexural) strength and the modulus of elasticity are decreased as the ductility of the resin is increased. It is concluded that since the matrix material is subjected to a triaxial state of stress when the composite specimen is subjected to uniaxial loads, the effect of matrix modulus, Poisson's ratio, and yield strength are more important than the matrix ductility measured under uniaxial stress. The effect on mechanical properties of various surface treatments applied to the fibers is also investigated. Finally, scanning electron micrographs are presented showing matrix cracks, fiber debonding, and fiber pull‐out.
Prediction of vinyl chloride monomer migration from rigid PVC pipe
Authors: Berens A. R. , Daniels C. A.
Published: December 2004

Data on the solubility and diffusion of vinyl chloride monomer (VCM) in PVC resin powders have been combined with published solutions of Fick's diffusion equation to yield predictions of the amount and rate of loss of residual VCM (RVCM) from rigid PVC pipe under storage and service conditions. The principal factors controlling VCM migration are the initial VCM content, thickness of the PVC section, temperature and the age of the PVC product. Analysis Solutions are presented for RVCM loss from freshly exturded pipe (uniform VCM concentration) into either the storage environment or the pipe contents. From these solutions, estimates are made for the real‐world situation of closed‐system service following variable storage periods. The validity of this approach for rigid PVC pipe in water‐service is supported by reasonable agreement between its predictions and experimental laboratory data on the VCM content of water stored in PVC pipes. Both the predictive model and experimental data indicate that PVC pipe containing ≤ mg/kg (1 part per million) residual VCM will result in VCM concentrations in water of less than 0.002 mg/kg ‐ under any expected service conditions.
Prediction of polyethylene melt rheological properties from molecular weight distribution data obtained by gel permeation chromatography
Authors: Shah Basit H. , Darby Ron
Published: December 2004

A method is presented for predicting rheological characteristics, such as shear dependent (non‐Newtonian) viscosity and components of linear oscillatory (complex) response functions for polyethylene melts from molecular weight distribution data obtained from gel permeation chromatographic (GPC) analysis. The results are compared with measured values of the rheological functions obtained from a variety of instruments over an extensive range of shear rates‐and frequencies. The agreement between predicted and measured rheological functions is quite good for high density resins. However, for a low density resin the agreement is not as good, although still reasonable over a considerable range of conditions. It is concluded that the quality of the GPC data is the key factor in the degree of success of the method.
Fracture of fiber reinforced composites
Authors: McGarry Frederick J. , Mandell John F. , Wang Su Su
Published: December 2004

Characteristics of the fracture of fiber reinforced plastic composites are described in terms of the elastic stress distribution at the crack tip, the mechanism of crack tip damage, and the modes and conditions of final fracture. The three‐dimensional, stress field at the tip of a sharp crack in a laminate is presented and contrasted to traditional two‐dimensional models. The response of the material in the form of inter‐ and intraply damage formation and growth under increasing load is characterized, and its effect in blunting the main crack is examined. The final fracture conditions, which may range from quasi‐brittle to notch insensitive, are discussed and related to the damage zone extension. Observed and anticipated effects of various material and geometric parameters are also discussed.
New techniques for mixing viscous reacting liquids. Part I. Mechanical means to improved laminar mixing
Authors: Rotz Christopher A. , Suh Nam P.
Published: December 2004

A discussion of the basic mechanisms and governing laws for liquid mixing is used to motivate new design concepts for more efficient mixing equipment. In this part of the paper, the use of V‐grooves in the inner cylinder of a concentric cylinder mixer is examined. The purpose of the grooves is to induce vortex‐like motions in the fluids in order to overcome the negative effects of interface orientation on mixing performance. Results show that the grooves are efficacious in increasing the effectiveness of the mixer. Descriptions of the experimental and analytical work done to characterize the design and to prove its efficacy are presented in detail. Scale‐up parameters are also discussed.
A critical examination of the prepreg resin flow experiment
Authors: Roller M. B.
Published: December 2004

This paper takes a critical look at the applicability of the currently accepted Resin Flow Method of prepreg evaluation. The Resin Flow test is generally a high pressure, small dimension lamination experiment which is used to characterize materials processed tit high pressures and large dimensions. Several simple experiments are described which support previously reported theory and provide a basis‐for more meaningful comparison of materials based on appropriate scaling via an analytical flow model.
An experimental technique for predicting foam processability and physical properties
Authors: Bigg Donald M. , Preston Joseph R. , Brenner Douglas
Published: December 2004

Thermoplastic foam properties and processing stability depend strongly on the ability to obtain the proper rheological properties for the polymer melt at temperatures where the decomposition of a chemical blowing agent may be controlled. An experimental technique has been developed which allows stable processing conditions to be determined for the continuous extrusion of foamed thermoplastics with known foam properties. The technique involves a thermal analysis of the polymer‐blowing agent formulation to determine the range of controllable extrusion temperatures. Rheological analysis was carried out using a slit die to establish a relationship between the thermal blowing characteristics of the polymer composition and rheological data which correlate with foam extrudability and the physical properties of the foam. This provides a means of predicting both processability and foam properties which aid in the scale‐up to production. The rheological‐foam property correlations were confirmed by continuous foam extrusion on a laboratory extruder.
Finite element analysis of calendering
Authors: Kiparissides C. , Vlachopoulos J.
Published: December 2004

The general equations describing the flow of Newtonian and non‐Newtonian fluids in the gap of two calender rolls were simplified by making use of the lubrication approximation. The resulting equations were solved by the finite element method. The results are in excellent agreement with existing analytical solutions for Newtonian fluids. New results were obtained for pressure, velocity profiles and sheet thickness of non‐Newtonian fluids for symmetric and asymmetric calendering (different roll diameters, different roll speeds). The solution of this problem demonstrated the great possibilities offered by the finite element method in solving Theological problems of practical significance, particularly whenever complicated wall boundaries or free surfaces are involved.
Rheological properties of incompatible blends of two elastomers
Authors: Shih C. K.
Published: December 2004

Mold flows and melt viscosities of an incompatible bi‐component EPDM and “Viton” fluoroelastormer system were examined. A marked reduction in the melt viscosities of either component was observed when a small amount of the other component was present. It was speculated that the phenomenon was a result of a slippage between the polymer and the coated capillary surface due to the presence of a minor amount of the incompatible polymer. Evidence is given to indicate that this effect cannot be accounted for using the “melt structural heterogeneity” mechanism proposed for a different system by Andtrianova.
Increase of adhesive bond strength through the mechanochemical creation of free radicals: I
Authors: Brenman M. , Lerchenthal Ch. H.
Published: December 2004

A new technique for improving the strength of bonded joints between various materials and different adhesives is described. Increased strength was obtained by mechanical Surface Activation Beneath Reactive Adhesives (SABRA). This technique results in higher bond energies due to the creation of free radicals. The surfaces were activated by abrasion with emery paper in the presence of the adhesive itself (epoxy), or of some suitable primer such as methyl methacrylate, acrylonitrile (AN) or hydrogen sulfide gas. The effects of this technique were demonstrated by four different methods: 1) Improved wetting of standard epoxy or water drops on the treated surface. 2) Achievement of bond energies between primers and polymeric surfaces exceeding the energy of solution in solvents, which were revealed by attenuated total reflectance infrared. 3) The detection of free radicals created by bond scission during abrasion by means of diphenylpicryl hydrazyl, (DPPH), a free radical scavenger, monitored by spec‐trocolorimetry, 4) Destructive testing of single lap joint test Pieces, scarfed tube joints and pee) test samples. These experiments will be described in a second paper. The theoretical base of the new approach is supported by a tentative estimate of energies set free by mechanochemical creation of free radicals and the excess heat released during abrasion.
Thermoplastic urethane elastomers V. Compatible and incompatible blends with various polymers
Authors: Seefried C. G. , Koleske J. V. , Critchfield F. E.
Published: December 2004

Various blends over extended compositional ranges have beer, prepared for combinations of a thermoplastic urethane elastomer with polystyrene, a styrene‐acrylonitrile copolymer, a polyhydroxyether (Phenoxy A), and poly(vinyl ethyl ether). The thermoplastic urethane elastomer was based on a polycaprolactone diol of approximately 2100 number average molecular weight, 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol at a molar ratio of 1/2/1, respectively. At ambient temperature, the tensile properties of the blends typically are intermediate between the values of the two separate components. Characterizations of the dynamic mechanical properties of the blends show the relative degree of compatibility for the thermoplastic urethane elastomer and the respective polymers. Two separate glass transitions are obtained for blends of polystyrene and the styrene‐acrylonitrile copolymer with the thermoplastic urethane elastomer. This behavior demonstrates that these blend systems are incompatible. The blends of Phenoxy A and the thermoplastic urethane elastomer exhibit a single glass transition for which the temperature is dependent on the respective concentration of the components. These mixtures are considered to be compatible in nature.
The stress‐strain behavior of materials exhibiting andrade creep
Authors: Berry G. C.
Published: December 2004

The stress‐strain behavior of a material exhibiting Andrade creep (for which the creep compliance is linear in the cube‐root of time) has been calculated for loading at constant strain rate \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm \varepsilon}\limits^{\rm .} $\end{document} and at constant stress rate \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sigma \limits^. $\end{document} for the limiting case of linear viscoelastic behavior and at constant \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sigma \limits^. $\end{document} for one type of nonlinear viscoelastic response. The recoverable strain after the stress has been removed has also been calculated for these three cases. The results of the calculations are compared with experiment.
An extensiometer for molten plastics
Authors: Rhi‐Sausi Jorge , Dealy John
Published: December 2004

A new rheometer has been developed to measure the extensional viscosity of molten thermoplastics at typical extrusion temperatures. It is at the same time versatile and easy to operate. One end of the test specimen is held in a fixed position by an oil‐cooled chimp mounted on the end of a force transducer. The other end of the specimen is held by, a moving, oil‐cooled chimp. The moving clamp is suspended from a carriage mounted on a ball nut which travels on a long lead screw. The lead screw is driven by an electric motor operating through a gear box, and its speed can be controlled to produce either a constant stress (creep) or a constant strain‐rate (stress growth) experiment. Experimental results have verified that in the “constant strain rate” mode the strain rate does rise rapidly to a constant level. Measurements on several polyethylene resins indicated that the extensional viscosity rises with strain rate at low strain rates.
Toughness and brittleness of plastics: A summary of an ACS/SPE symposium
Authors: Deanin Rudolph D.
Published: December 2004

A recent and joint ACS/SPE symposium featured 40 papers on the fundamental mechanism of brittle fracture, low‐speed crazing and fracture, high‐speed impact mechanisms, fatigue failure, multi‐phase polymer systems, and reinforcing fibers. A survey of these papers indicates the present state of our knowledge in this field, and the rapid progress it is making toward the development of high‐performance plastic materials.
The rheology of suspensions of titanate fibers in polymer solution
Authors: Onogi Shigeharu , Mikami Yoichi , Matsumoto Takayoshi
Published: December 2004

The, Theological properties of suspensions of relatively small amounts of titanate fibers in polystyrene solution have been measured by means of a Weissenberg rheogoniometer. The titanate fibers employed have diameters smaller than 0.5 micron and aspect ratios higher than 40. It has been found that the rheological properties of the suspensions are markedly time dependent; the steady‐flow shearing stress increases with increasing time when the rate of shear is changed abruptly from an initial high value to a considerably lower final value. This behavior can be attributed to the re‐formation of a structure formed by the dispersed fibers and broken at higher shear rates. The dynamic storage modulus G′ also depends strongly upon the re‐formation of the structure. Although the structure reformation process under shear appears too complicated to be analyzed satisfactorily, an attempt has been made to generalize the experimental data with a simple equation.
The role of intercrystalline links in the environmental stress cracking of high density polyethylene
Authors: Frayer Paul D. , Tong Paul Po‐Luk , Dreher William W.
Published: December 2004

Results of dynamic mechanical spectroscopy, infrared spectroscopy, and tensile stress‐strain data show that the non‐ionic surfactant Igepal CO‐630, often used as a stress cracking agent, and water are absorbed by high density polyethylene to cause an internal stress relaxation of the intercrystalline tie molecules. The resulting molecular rearrangements produce changes in both the crystalline and amorphous regions. Thus, a molecular mechanism is proposed for the long‐term aging process based on the results of accelerated aging in the presence of an environmental stress cracking agent.
Permeation and sorption in inhomogeneous polymer membranes
Authors: Frisch H. L.
Published: December 2004

Restricting the discussion to isothermal transport of a single penetrant in a polymer sample, we define convection and diffusion. We distinguish carefully between diffusion in homogeneous and inhomogeneous samples. In the latter case, the diffusion flux is no longer directly proportional to the gradient of the concentration, i.e., Fick's first law does not hold. We point out, unless an external force responsible for convection can be identified, that diffusion with convection in a homogeneous medium is in many instances indistinguishable mathematically from diffusion in an inhomogeneous medium with microscopic inhomogeneities. Finally, we list a number of exact results available for permeation and sorption parameters for thin slab of a dilute inhomogeneous material. These parameters all yield the same value of the diffusion coefficient if the latter is constant. On the other hand, these parameters provide different functional information about the partition coefficient and diffusion coefficient for an inhomogeneous polymer‐penetrant system.
Chemorheological changes in crosslinked epoxy resins subjected to large strains
Authors: Katz Dov , Buchman Alisa
Published: December 2004

Chemorheological changes in epoxy resins subjected to large strains while heated were observed earlier, but the subject was not treated quantitatively. This paper describes the investigation of an epoxy resin—Epon 826, of known chemical, structure, crosslinked with two different amines. By means of a simple calibrated apparatus, the epoxide samples were subjected to large strains in a non‐oxidizing atmosphere and in air. They were heated to different temperatures for various times; the results were compared with data obtained from unstrained samples kept in otherwise the same conditions. The results show a linear‐logarithmic relation between the torsion modulus, G(10) and the time of applied strain at a certain temperature and also a linear relation between G(10), and 1/T°K, both above T(10). The results obtained in swelling experiments support the data from 10 sec torsional modulus vs temperature measurements. An increase in the amount of solubles and in Mc is observed on extending the time of heating. A clear difference in properties between the strained and unstrained samples, kept in otherwise the sane conditions, is observed and the contribution of the applied strain to chemorheology has been shown. Both systems of crosslinked Epon 826 showed the same general behavior, although the specific data were different.
The deep drawing of thermoplastics
Authors: Miles M. J. , Mills N. J.
Published: December 2004

The theory of deep drawing, which has been developed for metals, is examined critically for thermoplastics. Two special characteristics of thermoplastics, the strong orientation hardening after initial yielding and the ease of crack formation and growth, are shown to vitiate the usual correlation between the drawability of the sheet and the low strain plastic behavior of the material. Attempts to improve the limiting draw ratio of thermoplastics, by biaxially rolling sheet prior to forming, are shown to be effective only if the polymer does not craze easily under tensile stresses.
The examination of poly(5‐hexene‐2‐one sulfone) as a positive‐working photoresist
Authors: Himics R. J. , Ross D. L.
Published: December 2004

A novel photoresist material is described, consisting of a copolymer of 5‐hexene‐2‐one and SO2, which performs with or without the addition of sensitizers. This photoresist forms non‐tacky films that adhere well to silicon oxide without requiring thermal treatment. They also have useful sensitivity, can be developed to form highly‐resolved images, are inert to conventional etchants, and are readily removed after etching. The synthesis, characterization, and a possible mechanism for photodegradation are presented.
A study of the photochemical reaction between poly(vinyl alcohol) and aqueous chromate ion
Authors: Lee Van Nice H. , Farlee Rodney
Published: December 2004

The photochemical reaction between poly(vinyl alcohol) (PVA) and chromate ion in aqueous solution has been studied by ultraviolet spectroscopy and electron paramagnetic resonance (EPR). The first step of the reaction appears to be formation of a PVA‐chromate ester. No further detectable chemical changes occur unless the ester is irradiated. Spectral sensitivity data indicate the reaction is initiated only by the chromate ester charge transfer absorptions at approximately 370 nm and 450 nm. EPR indicates an equilibrium concentration of Cr (V) during irradiation arid a decrease in concentration of Cr(V) following second order kinetics upon cessation of irradiation. The final reaction product is Cr (III) complexed with the hydroxyl groups of the PVA. The reaction rate is a function of pH between pH 12; however no detectable reaction occurred above pH 12. A mechanism is proposed for the PVA‐chromate photoreaction in solution.
Theoretical considerations on the sensitivities of electron beam resists
Authors: Tsuda Minoru , Oikawa Setsuko , Suzuki Akira
Published: December 2004

A theoretical study has been carried out in order to explain the sensitivities of electron beam and X‐ray resists. A preliminary investigation reveals that the behavior of these resists, on irradiation by high energy radiation, may be considered to be the electronically‐excited species in the polymer. To elucidate the chemical reactions in the excited states the adiabatic potential curves are calculated by the INDO/S procedure, which considers all the valence electrons and all the singly excited electronic configurations. Polyethylene and polyisobutylene were chosen as representative of crosslinkable and degradable polymers, respectively, since there is a parallelism between the beam sensitivity of resists and the effects of high energy radiation on polymers. Polyisobutylene has many antibonding curves favorable for the main chain scission in the excited states and polyethylene does not except for one improbable state. It was concluded that degradability is explainable by the ease of bond fission in the excited states; the crosslinkability is considered to be nondegradable property.
Studies of methyl methacrylate‐methyl α‐chloroacrylate, copolymers and poly(methyl α‐chloroactylate) as electron sensitive positive resists
Authors: Lai Juey H. , Shepherd Lloyd T. , Ulmer Robert , Griep Carl
Published: December 2004

Poly(methyl α‐chloroacrylate) (PMCA) and the copolymers of methyl methacrylate and methyl α‐chloroacrylate (poly(MMA‐co‐MCA)) have been reported recently to be more susceptible to radiation degradation than poly(methyl methacrylate) (PMMA). In this paper we report our studies of PMCA and poly(MMA‐co‐MCA) as electron‐sensitive positive resists. It has been found that both PMCA and the copolymers are more sensitive than PMMA. Using mixtures of dimethylformamide and 2‐propanol as developers, the sensitivities of PMCA and poly(MMA‐co‐MCA) (38 mole percent MCA) have been found to be 1 × 10−5 and 6 × 10−6 coulomb/cm2, respectively. It has also been found that crosslinking predominates in PMCA when the electron dose exceeds 6 × 10−4 coulomb/cm2.
Surface modification of polymers and practical adhesion
Authors: Schonhorn H. , Frisch H. L. , Gaines G. L.
Published: December 2004

The, nature of polymer surfaces has received increasing attention as the use of these materials, in a variety of forms, increases yearly. Modifications of polymer surfaces for adhesion, friction, and diffusion oriented appiications have necessitated a careful analysis of the surfade region morphology (surface physics) and chemical properties of the surface layer (surface chemistry). The behavior of composite structures has involved the discipline of classical fracture mechanics. The orientation of polymeric species or additives which migrate to the interface may modify the wetting characteristics and, most certainly, the frictional properties in addition to the diffusion of penetrant species beyond the boundary layer. The above topics are discussed within the framework of recent analytical and theoretical developments in surface science. The findings of these recent studies have facilitated many exciting technological advances.
Adhesion at polypropylene‐cellophane interfaces
Authors: Bialski A. , Manley R. St. J. , Schreiber H. P.
Published: December 2004

The shear strength of bonds between isotactic polypropylene and cellophane, formed under standard conditions, has beer studied as a function of cooling rates, following bond formation, and after ageing at temperatures up to 90°C. Rapid cooling produced cohesively failing bonds with shear strengths above 20 kg/em2. Weak, adhesively failing joints were produced under slow‐cooling conditions. Strong bonds deteriorated when joints were aged at temperatures above 50°C, but further improvement in bond strength was observed upon ageing at lower temperatures. Experimental observations were consistent with the development of smectic structure in the polypropylene upon rapid cooling; a tendency for transcrystallization in slow‐cooled joints was offset by the presence of weak boundary layers in the interface. Ageing produced further development of weak boundary layers and a transition from smectic to monoclinic crystallization in polypropylene. At higher ageing temperatures, the former effect seemed dominant; at lower temperatures, the structural change was assumed responsible for the observed improvement in bond strength.