bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracture of fiber glass laminates
Authors: Hamilton R. , Berg C. A. 
Published: December 2004

AbstractThe applicability of fracture mechanics to the description of initial notch extension under tension in quasi‐isotropic fiberglass laminates is tested experimentally. It is found that classical elastic fracture mechanics, without modifications of couple stress effects, as represented in the theory of Muki and Sternberg, is sufficient to describe initial notch extension in prenotched specimens which are sufficiently thick to avoid transplanar bucklings of the specimen under tension. The fracture toughness (KIC) is found to be 15 ksi √in. However, it is noted that in these specimens (0.035 in. thick) transplanar postbuckling deformation becomes pronounced well before fracture, and that different modes of buckling seen in externally notched and internally notched specimens have opposite effects on the apparent fracture toughness of the specimen. It is pointed out that the effect of transplanar buckling on fracture of fiber glass, with its high compliance and high strength, is a potential source of serious problems in design with this material.
Rheology of network forming systems
Authors: Mussatti Francis G. , Macosko Christopher W. 
Published: December 2004

AbstractViscosity and dynamic shear measurements are reported on several network forming systems as a function of reaction time and temperature. Phenolic, epoxy and EPDM rubber systems are examined. Rheological data are related to the reaction kinetics of the systems. With these relations overall activation energies, reaction orders and rate constants are interpreted from the data. These compare favorably with results in the literature.Applications of rheological techniques to processing problems of several network forming systems are described, specifically thermoset injection molding and SBR rubber vulcanization.
Measurement of oxidation stability of polyolefins by thermal analysis
Authors: Marshall D. I. , George E. J. , Turnipseed J. M. , Glenn J. L. 
Published: December 2004

AbstractDifferential thermal analysis (DTA) is well known for measuring temperatures and heats of physical and chemical transitions in materials. Recent development work on improved stabilization systems for polyolefin wire insulations has required fast procedures for measuring the performance of stabilization systems. Isothermal DTA procedures have been developed into routine tools for measuring stability of polyolefins by determining the oxidative induction time at elevated temperatures.Oxidative induction time has been used to study the stability of polyethylene and polypropylene in raw material form and on wire. The dependence on temperature and antioxidant concentration have been measured. Effects of oxidation catalysts, catalyst deactivators and various environmental exposures are readily observed. Techniques and apparatus have been developed for simultaneous testing of a multiplicity of samples, providing for economical large scale use of the method.
Infrared reflection studies of metal‐polymer interfaces
Authors: Chan M. G. , Allara D. L. 
Published: December 2004

AbstractBy incorporating the spectroscopic techniques of reflection‐absorption and internal reflection in the infrared region, we have been able to define and characterize overall chemical changes occurring at a metal‐polymer interface. Our initial studies have concentrated on the oxidative degradation of metal‐polymer systems. These systems are of particular importance because of the common need to retard the metal‐catalyzed degradation of the polymer. Preliminary results for copper‐polyethylene interfaces, models for polyolefin‐insulated cable, have shown the copper surface to be the site of the initial catalysis in the oxidation of the polyethylene. When copper deactivators are added to inhibit the oxidation, initial reactions between the copper surface and the inhibitor can be seen. The importance of these surface reactions highlights the necessity for studying the interface.
Time‐temperature superpositioning of viscosity‐time profiles of three high temperature epoxy resins
Authors: White R. P. 
Published: December 2004

AbstractThe chemo‐rheological behavior has been elucidated for three high temperature epoxy resins. Constant temperature and shear stress measurements were made on a modified Weissenberg Rheogoniometer. Curing behavior of various temperatures is unified by a time‐temperature superposition method. The curing rate of one resin, Ferro E‐293, is limited by the chemical reaction. The other resins, 3M PR‐286 and PR‐288, each have consecutively occurring reactions, both of which are diffusion limited. The chemo‐rheological information obtained for these materials is used to model viscosity for compression molding of hand‐laidup composites.
Flow visualization for injection molding of polyethylene and polystyrene melts
Authors: White James L. , Dee Henry B. 
Published: December 2004

AbstractFlow patterns have been observed during the injection molding of rheologically characterized low‐density polyethylene and polystyrene melts under various molding conditions. Some studies of high‐density polyethylene were also carried out. Various mold designs were included in the study and the flow patterns investigated under both isothermal and cold cavity wall conditions. In addition to investigating injection molding of single polymer melts, flow patterns in the sandwich molding of polyethylene and polystyrene were studied.
Polymerization of methyl methacrylate with Ziegler‐Natta catalysts
Authors: Kapur S. L. , Deshpande A. B. 
Published: December 2004

AbstractThe polymerization of methyl methacrylate with Ziegler‐Natta catalyst, anionic catalyst and gamma radiation has been shown possible at temperatures below 0°C. A free radical mechanism is suggested in the case of Ziegler‐Natta catalyst which is known for a coordinate anionic polymerization mechanism. In view of this, the Ziegler‐Natta catalysts based on vanadium compounds were investigated for the polymerization of methyl methacrylate. They were found effective for polymerization of methyl methacrylate at, and around, room temperature. The structure of the polymer was stereoblock. This apparently leads to the conclusion that the mechanism of polymerization of methyl methacrylate was not free radical but coordinate anionic. Similarly, the catalyst system of chromium acetyl acetonate and aluminium triethyl polymerized methyl methacrylate at and around room temperature into an highly stereoblock structure containing high isotacticity.
High‐frequency alpha transition response of some plasticized poly(vinyl chloride) compositions
Authors: Paddison Gary W. 
Published: December 2004

AbstractA high‐frequency alpha transition of some plasticized poly (vinyl chloride) compositions was measured at 4 MHz employing an ultrasonic pulse technique. The material property used to determine the transition region was the intrinsic loss, which is indicative of changes in both the storage and loss moduli. Four dicarboxylic esters were used as plasticizing agents. These were (1) butyl benzyl phthalate, (2) di‐(2‐ethylhexyl) phthalate, (3) dibenzyl sebacate, and (4) di‐(2‐ethylhexyl) sebacate. Compositions were prepared using 10, 20, and 30 parts by weight of plasticizer per hundred of polymer. A small quantity of thermal stabilizer was added to prevent degradation. Samples were produced by an extrusion process to promote a high degree of fusion and consolidation. Comparison of the data showed the usual decrease in the transition temperature with increasing concentration of the plasticizing agent. However, it was shown that the controlling factor of the transition response was the molecular structure of the plasticizer. Both the structure of the parent dicarboxylic acid and the ester side groups were controlling factors. This relationship was supported when a high‐frequency storage and loss modulus (dilatational) was compared at 25°C to the molecular weight of the side chain. The dimethyl ester was included for both series for comparative purposes. These data showed that the storage modulus increased and the loss modulus decreased with increasing chain length and complexity. However, the factor contributing most was the complexity (steric hindrance) of the plasticizing molecule.
A design approach for thermoplastic flexure components subjected to cyclic loading
Authors: McCammond D. , Nakatsumi F. 
Published: December 2004

AbstractA recently proposed method for predicting the strains resulting from the application of uniaxial cyclic stresses is developed for application to polymer systems. Experimental results obtained from rectangular cyclic loading tests on prismatic beams and circular plates are compared with theoretical predictions using two sources of basic data, (a) uniaxial isochronous and creep data and (b) deformation data resulting from constant load creep tests conducted on the components. It is concluded that the method would require considerably less computation, to obtain satisfactory accuracy, than the alternative integral superposition methods even for rectangular cyclic loading and would prove much more tractable when applied to other forms of cyclic loading.
A step toward molecular‐level understanding of the toughness of glassy plastics
Authors: Knight A. C. 
Published: December 2004

AbstractRigid, glassy plastics differ over a wide range in the amount of energy they can absorb before fracturing under the influence of an applied stress. It is here proposed that molecular structure influences energy absorption more significantly by determining the onset of fracture than by its effect on the energy‐dissipating processes themselves. Emphasis has been placed, therefore, on finding a relationship between molecular structure and the onset of fracture. Since many relationships between molecular structure and bulk mechanical response have already been established, it should be a useful step to relate the onset of fracture to bulk mechanical responses. The hypothesis is developed that the appropriate bulk property is the stress‐deformation function of the material. The observed stress‐deformation function is of such a nature that a highly non‐homogeneous deformation is produced at any point of stress concentration. Typically, this is a narrow region in which the material is highly deformed while the deformation in adjacent material is still slight. Fracture initiation is postulated to occur in such a region of high deformation. Differences among polymers in the shape of the stress‐deformation function are demonstrated experimentally. These differences correlate with tough‐brittle behavior. An explanation is proposed in terms of the probability of fracture initiation.
Polymeric catenanes
Authors: Callahan D. , Frisch H. L. , Klempner D. 
Published: December 2004

AbstractA crosslinked polybutadiene containing a cyclic depsipeptide (Valinomycin) has been synthesized in which there is some possibility of threading to produce a catenated structure (polymeric catenane). Unthreaded rings were removed by extraction with toluene. An elemental analysis indicated the yield of threaded rings to be greater than the calculated expected yield. The total amount of threaded Valinomycin present was 0.37 percent. The rings showed no effect on the calorimetric glass transition temperature, but did result in an increase in the tensile modulus.
Creep of carbonated plastic beverage bottles
Authors: Thiruvillakkat K. , Mahajan G. K. 
Published: December 2004

AbstractLong‐term performance of carbonated plastic beverage bottles depends on a number of critical factors. Testing to predict the effects of these factors is expensive and time‐consuming. Many of these factors are interdependent. The presence of more than one critical factor in a given test makes the analysis of data difficult. The separation and prediction of the contribution of any one factor to long‐term performance is complex even for the single composition studied, a rubber‐modified high acrylonitrile resin. In addition to superior gas barrier properties, the container should exhibit a high degree of creep resistance. Visible manifestations of creep are reflected in gross dimensional changes of the bottle and consequent loss in carbonation. The purpose of this paper is to examine creep deformation of the bottle and its implications on bottle performance. Various factors contributing to the creep are also briefly analyzed. Since the ultimate goal is to predict creep, the merits of relevant short‐term tests in this context are discussed. Finally, the data from short‐term tests are compared with creep data obtained on bottles that were subjected to long‐term tests.
Degradation of chlorinated polyethylene—III: Effect of additives on dehydrochlorination and oxygen absorption
Authors: Abu‐Isa Ismat A. 
Published: December 2004

AbstractDegradation of chlorinated polymers takes place via two simultaneous reactions; namely, dehydrochlorination and oxygen absorption. The dehydrochlorination and oxygen absorption of five grades of chlorinated polyenthylenes were studied at temperatures varying between 120 and 180°C. The chlorinated polyethylene grades varied in both molecular weight and chlorine content, the latter being in the range of 24.0 to 45.2 percent chlorine. Dehydrochlorination measurements on the pure polymers in both nitrogen and oxygen atmospheres showed that the rate of dehydrochlorination increases with an increase in the degree of chlorination of the polymer. The oxygen absorption rate, however, showed a decrease with higher chlorine content of the polymer.Dehydrochlorination and oxygen absorption studies were also carried out on chlorinated polyethylene containing dehydrochlorination stabilizers, antioxidants, antimony oxide, and other metal salts and metal oxides. Retardation of both oxygen absorption and dehydrochlorination was observed in the presence of antioxidants. More significant, however, was the observed action of some dehydrochlorination stabilizers as efficient antioxidants in the polymer.
Analysis of a cross head die with the flow analysis network (FAN) method
Authors: Gutfinger C. , Broyer E. , Tadmor Z. 
Published: December 2004

AbstractThe Flow Analysis Network (FAN) method was adapted for solving the isothermal flow problem in a cross head die. Given the polymer rheology and the die geometry, the flow streamlines in the die and the flow rate uniformity at the exit can be calculated for any given head pressure. The optimum geometrical configuration of the die can be computed by repeated simulations. Results of the computations with the present method are shown to be in good agreement with previously published computations.
Oriented short glass‐fiber composites. II. Analysis of parameters controlling the fiber/glycerine orientation process
Authors: Kacir L. , Narkis M. , Ishai O. 
Published: December 2004

AbstractNine parameters related to the fiber/glycerine orientation process are analyzed. These parameters can be divided into machine, material and processing variables. The effect of each parameter on the cumulative percent of oriented fibers within specified angle limits (±10 deg) is discussed. Similar effects were found on an accumulative exponential function which is represented by a single empirical constant. Five parameters are shown to have major effects on the alignment which can be achieved in the mats. These parameters include: temperature of the fiber/glycerine dispersion, pressure head on the dispersion and three geometrical variables of the orientation machine.
Structure development during polymer processing: Studies of the melt spinning of polyethylene and polypropylene fibers
Authors: Spruiell Joseph E. , White James L. 
Published: December 2004

AbstractExperimental studies of structure development in melt spinning of polyethylene and polypropylene fibers are described. Emphasis is given to the influence of applied stresses on the rates of crystallization and on the development of crystalline morphology. The relationship of fiber morphology to mechanical properties, especially “hard elastic fibers” is considered. The relevance of such studies to other polymer processing operations such as film extrusion is discussed.
Non‐isothermal curing of reactive plastics
Authors: Progelhof R. C. , Throne J. L. 
Published: December 2004

AbstractOne dimensional transient heat conduction analysis of reactive, unfilled polyesters and epoxies shows that care must be taken during curing to minimize large temperature excursions due to internal heat generation. Isothermal heat generation rates have been shown to underestimate the non‐isothermal values by more than an order of magnitude.
Dynamic mechanical and thermal properties of fire‐retardant polypropylene
Authors: Chang Eng Pi , Kirsten Rudy , Salovey Ronald 
Published: December 2004

AbstractA study of the effect of a series of fire retardants and antimony oxide upon the dynamic mechanical and thermal properties of polypropylene suggests three categories. (1) “Inert Fillers”—These raise the elastis modulus and the heat distortion temperature of polypropylene without shifting its glass transition temperature. The melting point of polypropylene is only depressed by 1–3°C, the heat of fusion and the percentage of crystallinity of polypropylene in these composites is ∼10 percent lower at additive concentrations of ∼30 percent. Very poor interaction exists between the additive and the thermo‐plastic which apparently exist in two separate phases. (2) “Chain Stiffener”—These raise the elastic modulus (∼25 percent) and the glass transition (∼11°C) for polypropylene; the melting point of polypropylene in the composite is lowered by ∼6°C indicative of good interaction between the additive and polypropylene. (3) “Plasticizer”—These lower the room temperature elastic modulus (∼20 percent) and the glass transition temperature (∼11°C) of polypropylene; the melting point of polypropylene in the composite is depressed by ∼10°C indicating good interaction. The efficacy of the “plasticizer” and “chain stiffener” are attributed partially to melting of polypropylene at the processing temperature.
Structural thermoplastic foam—A low energy processed material
Authors: Throne James L. , Griskey Richard G. 
Published: December 2004

AbstractShortages of both energy and materials make it imperative that low cost substances, processed with low energy requirements, be developed as soon as possible. One promising type of materials are the structural thermoplastic foams since they further enhance the favorable strength to weight ratio of plastics while reducing overall material needs. In addition, foam processing also capitalizes on the generally lower energy consumption and manpower‐hour requirements for plastics. Finally, the possibility of forming larger and more complex shapes opens up new application areas. The largest deterrent to the use of structural foams is the lack of appropriate basic engineering and scientific knowledge. This paper not only summarizes and extends such understanding, but also shows how appropriate design procedures can be developed.
Low velocity surface fracture patterns and energies in poly(methyl methacrylate)
Authors: Osborne P. W. 
Published: December 2004

AbstractSteady‐state fracture techniques were used to investigate the surface fracture patterns and surface fracture energies of poly(methyl methacrylate) at low velocities (10 cm/sec to 10−5 cm/sec). Several anomalies were discovered: (1) Small surface cracks, running parallel to the crack front, which were initiated by imperfections; (2) a “zero velocity” transition from the normal surface fracture patterns to a “laminar” pattern; and (3) a subsequent transition from the laminar pattern to a “turbulent” pattern. The velocities at which these anomalous fracture patterns occurred were of the order of 10−4 to 10−6 cm/sec. The corresponding surface fracture energies were as low as 105 erg/cm2.
The injection molding of thermosets
Authors: Fleischmann J. J. 
Published: December 2004

AbstractCurrent industry trends toward increasing automation, as well as increased flexibility in material selection have focused a strong spot light on thermoset injection molding. The growth of thermoset injection molding is reviewed comparatively with the technical history and growth of thermoplastic injection. The progress we see to date and the promise for the future in material characteristics and properties, mold design features, equipment features, changing concepts and new thoughts are discussed.
The modeling of molecular motions in crystalline polymers
Authors: Boyd Richard H. 
Published: December 2004

AbstractRegions in which the mechanical and dielectric properties of polymers change rapidly with temperature (transitions or relaxations) are supposed to be due to the onset of certain types of molecular motions. A precise description of these various molecular motions would be invaluable in the areas, of structure vs property relationships and the tailoring of polymers to end‐uses. However, our knowledge concerning these motions is quite limited and qualitative at best. The biggest stumbling block has been an inability to test the consequences of proposed mechanisms in terms of experimentally observed quantities. The problem in many cases has not been a lack of adequate theory but rather an insufficiency of knowledge, appropriate for input into the theory, concerning the energetics of chain motions. However, in the past few years there has been considerable progress in studying chain energetics by means of conformational energy calculations (molecular mechanics). In the present paper, this work on crystalline polymers will be reviewed and some recent calculations which illustrate the present state of the art are discussed.
Predictions of limiting mechanical performance for anisotropic crystalline polymers
Authors: McCullough R. L. , Wu C. T. , Seferis J. C. , Lindenmeyer P. H. 
Published: December 2004

AbstractA four‐stage synthesis of molecular, micromechanical, and macromechanical models is used to predict the dependence of the longitudinal and transverse Young's moduli and the axial and transverse shear moduli of anisotropic polyethylene on percent crystallinity and the state of molecular orientation. Variational methods are employed to establish the upper and lower limits for anisotropic elastic response. The difference between lower and upper bound limits is interpreted as the potential for improving mechanical performance. A modified form of the Tsai‐Halpin equation is used to examine parametric ranging (via a contiguity factor, ξ) between the lower and Tupper bound limits. In this application, the contiguity factor is interpreted as a characteristic of the internal stress‐strain distribution which is dependent upon the size, shape, packing geometry, and elastic properties of the crystalline and amorphous regions. The potential for achieving high modulus polymeric materials is illustrated by treating percent crystallinity, molecular orientation, and contiguity as materials design variables subject to control by processing conditions. Optimum property trade‐offs, necessary for balancing the over all mechanical behavior of anisotropic materials, are illustrated through the control of orientation and contiguity, The theoretical predictions for the moduli of anisotropic polyethylene are in good agreement with values reported for material processed by traditional procedures as well as ultra‐oriented polyethylene.