bluuebunny/crossref_metadata_2025_split huggingface dataset:
Key indicators for plastics performance in consumer products
Authors: Hagan Ralph S. , Thomas James R. 
Published: December 2004

AbstractTwo overriding characteristics for major applications of plastics in consumer products are:
—the need for high volume production and
—their exposure to hostile environments.Successful application and continued growth for plastics in these products requires knowledgeable prediction of performance in the process to produce the plastic part and in the environments to which it will be exposed during the product's lifetime. Progress on establishing relationships between material properties and structure are described with emphasis on response to melt process conditions and behavior when exposed to hostile environments.Commercial plastics and the processes by which they are converted into useful applications are complex systems. A multitude of interacting variables must be dealt with in order to achieve successful implementation in commercial products. Specific examples are discussed in the area of processing for non‐Newtonian flow characteristics and overt effects in injection molding and extrusion, tailoring of polymers within established rheological limits and the influence of melt processing on physical and mechanical properties. The influence of application environments is discussed and specific examples are given for environmental stress cracking, stress‐environment embrittlement and the effects of hot water solutions on polymer systems.
Tensile crazing and shear banding of styrene A: Temperature and rate effects
Authors: Sultan J. N. , McGarry F. J. 
Published: December 2004

AbstractTensile yield, flow, and fracture mechanisms in styrene A (SA), a styrene‐acrylonitrile copolymer rubber‐modified styrene A (RMSA) have been studied and characterized into two basic types: tensile crazing and shear banding. Each can be represented by a master curve and equation over ranges of temperature and deformation rates. Each exhibits distinctive activation energy and volume values. Tensile crazing predominates in unoriented SA below 70°C, and in RMSA. Shear yielding predominates in oriented SA.
Polyvinyl chloride insoluble gels: Their structure and effect on properties of cast films
Authors: Filisko F. E. 
Published: December 2004

AbstractThe effect of insoluble gel material, crystalline aggregates, and suspension particle membranes on the physical and mechanical properties of solution cast films of suspension PVC has been studied. The chemical structure and morphology of the insoluble gel material was also studied. The suspension particle membranes are found to contain significant amounts of hydroxyl and carbonyl groups but are still predominately PVC. These particles affect the transparency of cast films as well as the surface topography by forming discrete clusters upon drying which are uniformly distributed throughout the films. Finally, insoluble gel material is found to have no significant effect on the low and high speed mechanical properties of the films.
A theoretical study of the effect of an interfacial layer on the properties of composites
Authors: Broutman Lawrence J. , Agarwal Bhagwan Das 
Published: December 2004

AbstractA theoretical analysis using finite element methods has been applied to oriented short‐fiber composites and spherical particle composites in order to predict the influence of a finite layer at the interface on mechanical properties. In this study the interfacial layer has been modeled by assuming that a layer surrounds the interface and that this layer has a modulus of elasticity different than both the fiber and the matrix. The stress distribution near the interface has been determined as a function of the elastic constants of the interface layer and the interface layer volume fraction. This analysis has also been performed for two volume fractions of fibers and two fiber length to diameter ratios. From this stress distribution, the composite modulus and toughness have been determined as a function of interface modulus. It is theoretically shown that the toughness, measured by amount of strain energy absorbed, can be maximized by controlling the interface modulus. Furthermore, recent experimental results appear to verify the theory.
Stability of polymer composites as positive‐temperature‐coefficient resistors
Authors: Meyer J. 
Published: December 2004

AbstractThis is a study of materials which are positive‐temperature‐coefficient resistors. Such materials, composed of conductive particles dispersed in a crystalline polymeric matrix, have been found to be of limited stability. An example is carbon black in high‐density polyethylene. On repeated cycling through the anomaly temperature or on extensive heating at or above the anomaly temperature, the room temperature resistivity rises and the anomaly height falls to zero. This phenomenon has been shown to be caused by the absorption of oxygen by the polymer matrix which alters the structure, reduces the crystallinity, and induces an unusual form of crosslinking of a reversible nature.
A special mold and tracer technique for studying shear and extensional flows in a mold cavity during injection molding
Authors: Schmidt L. R. 
Published: December 2004

AbstractA specially‐designed mold with interchangeable cavity plates was built and used with an Instron capillary rheometer, type MCR, to investigate the injection molding process. Flow patterns in the mold cavity were illustrated with a visual tracer technique. The complete deformation history of the tracers was recorded on a motion picture for several runs. The flow patterns provide data for computing the components of the rate‐of‐deformation tensor which is used to identify specific shear and extensional flows. The tracer marks in the cross section of a molding offer information on the skin thickness and the dimensions of the core channel.
Molding polycarbonate: Moisture degradation effect on physical and chemical properties
Authors: Long T. S. , Sokol R. J. 
Published: December 2004

AbstractProper drying techniques prior to molding can eliminate the overall effects of moisture on the physicochemical properties of polycarbonate. Problems associated with moisture in polycarbonate during molding are described in detail. Moisture absorption is very rapid with the maximum allowable moisture content of 0.03 percent reached within 30 minutes at 49 percent RH and 75°F. Molding with excess moisture content causes a chemical and physical degradation resulting in reduction in tensile impact strength, tensile elongation, ultimate tensile strength, proportional limit and molecular weight. New and existing techniques and procedures for degradation detection were investigated, such as intrinsic viscosity, infrared spectrometry, and thermal methods of analysis. Gel permeation chromatography (GPC) proved the most satisfactory. GPC provided information on the average molecular weight and polydispersity.
Cold‐rolling of polymer: 4. Toughness enhancement in amorphous polymers
Authors: Broutman L. J. , Krishnakumar S. 
Published: December 2004

AbstractSeveral types of amorphous polymers have been cold‐rolled to various thickness reductions and the notched Izod impact behavior has then been studied. It has been determined that whereas some polymers exhibit large increases in impact strength with modest reductions in thickness other polymers only exhibit small increases in impact strength. For example, PVC, ABS, poly (phenylene oxide), and polysulfones show large increases in impact strength whereas rubber‐toughened acrylics show only a small increase in impact strength.
Segmented polyether ester copolymers—A new generation of high performance thermoplastic elastomers
Authors: Hoeschele G. K. 
Published: December 2004

AbstractThis paper reviews a series of high‐melting thermoplastic polyether esters prepared by transesterification from dimethyl terephthalate, polytetramethylene ether glycol (MW 600–2000), and 1,4‐butanediol. The resulting copolyesters exhibit a two‐phase domain structure consisting of amorphous polyether ester soft segments and crystalline tetramethylene terephthalate hard segments. By proper selection of the relative amounts of soft and hard segments, polymers ranging from relatively soft elastomers to impact resistant elastoplastics may be obtained. The preparation, polymer structure as well as the physical and environmental properties of polyether esters are discussed. The combination of good melt flow properties, excellent melt stability, and rapid hardening rates permits the processing of these polymers by a wide variety of methods. The excellent processing characteristics in conjunction with the unusual physical and mechanical properties of segmented polyether esters has led to their wide acceptance.
Nondestructive testing of plastics by means of holographic interferometry
Authors: Grünewald K. , Fritzsch W. , Harnier A. v. , Roth E. 
Published: December 2004

AbstractHolographic interferometry was investigated as a method for nondestructive testing of flat sheets of glass‐fiber reinforced plastics. Initially, the deformation behavior of faultless sheets was examined by means of holographic interferometry. The interferograms which resulted from various loading conditions (i.e., tensile load, bending) were compared to results obtained mathematically. The interferograms of faultless sheets were then compared to those of defective laminates. By suitable loading of the smaples a range of laminate faults could be readily and qualitatively detected. The influence of these faults on the tensile strength was examined. Not only the mechanical loading of the laminates, but also an acoustic stimulation of the sheets proved suitable for interferometric detection of laminate faults.
Dynamic mechanical response of polymer‐impregnated mortars
Authors: Whiting David , Blankenhorn Paul R. , Kline Donald E. 
Published: December 2004

AbstractDynamic elastic modulus and internal friction of a Portland cement (Type I) mortar system impregnated with an epoxy resin system and with methyl methacrylate were measured in the temperature range of 100 to 450°K by use of a free‐free resonance technique. Dynamic modulus values were found to increase greatly compared to controls, especially at lower (<300°K) temperatures. Above 320°K the dynamic moduli of polymer‐impregnated mortars exhibited a sharp decrease toward control values. Low temperature damping maxima of the composites differed significantly from those of the constituent phases.
High‐strength/high‐modulus organic fibers
Authors: Preston J. 
Published: December 2004

AbstractCurrent trends and developments taken from the literature are reviewed and some new work from the laboratories of Monsanto Company is presented concerning the use of aromatic polymers for high‐strength/high‐modulus fibers. In the area of aromatic polymer synthesis, pertinent information concerning the factors necessary for the attainment of high molecular weight for the heat‐resistant type polymers and for the ultra‐rigid type polymers is discussed. Some new polymers and new routes of synthesis for rod‐like polymers are described along with the tensile properties of fibers from these novel polymers.
Frequency sensitivity of fatigue processes in polymeric solids
Authors: Hertzberg R. W. , Manson J. A. , Skibo M. 
Published: December 2004

AbstractOne is faced with an interesting challenge when trying to explain the effect of test frequency on polymer fatigue performance. While hysteretic heating arguments appear sufficient to explain adiminutionof fatigue resistance with increasing cyclic frequency inunnotchedtest samples, theenhancementof fatigue resistance in many polymers with increasing cyclic frequency innotchedsamples is still not clearly understood. In large measure, this is due to contradictory trends in fre‐quency‐sensitive material properties which affect the fatigue process. In this paper, a number of proposed fatigue models dealing with the time and strain rate dependence of elastic modulus, yield strength, creep and localized crack tip heating are examined and confronted with available data from the literature. Additional fatigue crack propagation data for poly(methyl methacrylate), poly (vinyl chloride), polystyrene, poly‐carbonate, nylon 66, poly(vinylidene fluoride) and poly(2,6‐dimethylphenylene oxide) were obtained and are reported herein. These data were obtained over a maximum frequency range of 0.1 to 100 Hz and, for selected polymers, with various waveforms. Frequency sensitivity is shown to be greatest in those polymers that show a high tendency for crazing. Relative fatigue behavior is found to reflect a competition between strain rate and creep effects. Where creep effects dominate, the total crack growth rate may be viewed as consisting of the summation of pure fatigue and creep components, respectively. Finally, the β transition appears to have a role, with frequency sensitivity being at a maximum for polymers where the β transition at room temperature occurs in the range of the experimental test frequency.
The measurement of toughness of ABS and high‐impact polystyrene by the falling dart impact test
Authors: Bibeau Alexander A. 
Published: December 2004

AbstractFalling Dart Impact, FDI, toughness is used extensively to characterize the response of plastics to potential abuse. A critical study shows FDI toughness is highly variable with only 68 percent of the test pieces of a typical material failing within ±35 percent of the mean break energy, MBE. If no adjustment for this variability is made, the ASTM accepted “up/down” testing procedure leads to erroneous MBE values. A statistical analysis was carried out which defines the confidence which can be placed in measured MBE's as a function of the number of pieces tested. This analysis shows, for example, that 60 pieces must be tested so that a measured 20 percent difference in MBE's will be significant 90 percent of the time; while if 20 pieces are tested, as is suggested by ASTM, a 35 percent difference is needed before the same level of significance is reached.
Mechanical and optical properties of polyurethane‐polystyrene two‐phase polymers
Authors: Kaplan D. , Tschoegl N. W. 
Published: December 2004

AbstractThe mechanical and optical properties have been examined of a series of polyurethane‐polystyrene two‐phase systems produced by simultaneous polymerization. Torsion pendulum data show two separate glass transitions which are essentially those of the constituent homopolymers. Thus these systems do not from true interpenetrating networks. Phase inversion from a continuous polyurethane to a continuous polystyrene phase occurred at the relatively low styrene concentration of 20 to 25%. Measurements of the stress‐optical coefficients supported this finding. When polystyrene formed the continuous phase, straining produced softening at strains below about 15 percent. Birefringence measurements indicated that the rubbery polyurethane domains did not orient in these compositions. The stress‐optical coefficients showed no time dependence. The strain‐optical coefficients decreased with increasing temperature.
Thermal analysis as an aid to monomer plant design
Authors: Riga Alan T. 
Published: December 2004

AbstractThe thermal data needed for the design of heat transfer equipment and distillation columns for the manufacture of a new vinyl monomer, diacetone acrylamide, were rapidly and effectively provided by differential scanning calorimetry. A method has been developed for determining the effects of inhibitors and metals on the polymerization of the vinyl monomer. The latter was an aid in the selection of materials of construction. DSC was used to determine the total inhibitor concentration in the monomer. Selection of inhibitors was facilitated by information derived from thermal analysis.
Heat conduction in metal‐filled polymers: The role of particle size, shape, and orientation
Authors: Hansen David , Tomkiewicz Robert 
Published: December 2004

AbstractElongated metal or other conductive particles can be added to a polymer or other poor conductor to produce a composite of enhanced conductivity. Elongated particles are generally more effective than spherical or irregular particles but very slender particles can be dramatically more effective. For example, cylindrical copper particles with length/diameter (L/D) = 20, randomly dispersed in epoxy resin at a loading of 5 percent copper by volume yield a composite with a thermal conductivity about 1.5 times that of the base resin. However, the same volume of copper particles with L/D = 50 can increase the conductivity by a factor of 5 or more.This paper presents a new type of analysis for predicting the thermal conductivity of disperse composites from the properties of the component phases and elementary characterizations of particle shapes and orientation. This analysis successfully predicted the sensitivity to particle shape which was confirmed by experiments also reported in this paper. These results suggest that highly elongated particles may be used to achieve dramatic modifications of thermal conductivity and the analysis presented here may be a useful tool in the design or development of disperse composites of specific thermal conductivity. The analysis may also apply to other properties such as electrical conductivity or magnetic permeability.
Effect of processing variables on the thermophysical properties of polybenzimidazole foams
Authors: Kourtides Demetrius A. , Parker John A. 
Published: December 2004

AbstractPolybenzimidazole foams in the density range of 24 to 80 kg/m3 have excellent thermophysical properties, fire resistance, and low smoke evolution when exposed to heat or flame; they also retain their mechanical properties up to 200°C without any significant degradation. In addition to superior thermal properties, the foams maintain a high degree of flexibility and a good modulus‐to‐weight ratio, as well as high strength‐to‐weight relationship at high temperatures. These properties make this foam an attractive candidate as a low‐weight, high‐temperature insulation for aerospace applications. This paper describes the relationship between prepolymer purity, processing parameters, and additives to the thermophysical and chemical properties of these foams. Foam properties are shown to be affected by differences in prepolymer purity, curing schedule, and the presence of additives in the foam. High‐temperature compressive properties were imporved by postcuring at 527°C. Surfactant additives were found to improve uniformity of cell size. Foams were characterized according to high‐temperature mechanical properties, density, porosity, thermal diffusivity, thermal conductivity, and specific heat.
Oriented short glass‐fiber composites. I. Preparation and statistical analysis of aligned fiber mats
Authors: Kacir L. , Narkis M. , Ishai O. 
Published: December 2004

AbstractOriented short fiberglass mats were prepared by a converging flow technique of fiber/glycerine dispersions. The fiberglass contained 3 percent of identical colored fibers which were counted from enlarged photographs in regard to their deviation from the alignment axis. Representative accumulative data of fiber alignment are shown for optimal and inadequate preparation conditions. In successful experiments over 90 percent of the fibers were found in the angular range of ±15 deg and 57 percent within the range of ±5 deg. Statistical analysis has shown that the experimental accumulative curves can be best described by a single parameter exponential equation Y = 1 − e−λα where Y is the accumulative fraction of fibers, α is the orientation angle and λ is a single empirical parameter.
Prediction of the creep behavior of reinforced plastics
Authors: Menges G. , Roskothen H. J. 
Published: December 2004

AbstractThe time‐dependent deformation of orthotropic and transversely isotropic viscoelastic materials under biaxial constant load is given in the range of linear and reversible stress‐strain behavior for isothermal processes. This allows one to calculate the deformation of plastics on the basis of isochronous stress‐strain diagrams. In addition, a method is presented which allows a calculation of the creep moduli of mat‐reinforced unsaturated polyesters and their dependence on glass content, temperature, and time. This calculation requires only specific creep data of matrix material and the elastic modulus of the reinforcement.
Mold‐filling studies for the injection molding of thermoplastic materials. Part I: The flow of plastic materials in hot‐ and cold‐walled circular channels
Authors: Williams G. , Lord H. A. 
Published: December 2004

AbstractA finite difference analysis has been developed which predicts the temperature, pressure, and velocity distributions for the flow of thermoplastic materials in straight and tapered, hot and cold walled circular flow channels. This analysis when combined with the cavity filling analysis described in Part II, gives the molding engineer the capability of modeling the injection molding process from the shot to the cavity during injection. The information that is obtained from these analyses is useful in equipment design and modification since it allows numerical experiments to be performed so that one may ascertain the effects on moldability of flow channel and cavity geometry, material properties, and operating conditions. In addition, the information is useful in problem diagnosis and analysis to ascertain causes of and evaluate potential solutions to molding problems.
Stampable nylon sheets: Reinforcing with long glass fibers
Authors: Segal L. , Steinberg A. H. 
Published: December 2004

AbstractGlass fiber reinforced thermoplastics have been utilized for many years in automotive and other high‐performance applications. One of the newest processing methods for these materials is “stamping”, a process in which a reinforced thermoplastics sheet is heated and rapidly formed into a shaped object between matched metal dies. Advantages of products produced by this method include the following: parts consolidation, excellent strength, low cycle times even for very large objects, low finishing and tooling costs, and utilization of existing metal forming equipment. An extremely broad range of physical properties can be provided by tailoring both composition and construction of the composite sheets to the end‐use requirements. The purpose of this paper is to discuss the material properties which can be achieved in stampable nylon‐6 sheets as compared to corresponding injection molded compositions. The prime differences in composition between glass fiber reinforced stampable sheets and reinforced injection molded parts is the length and distribution of the glass fiber reinforcement utilized in each process. After injection molding, glass fibers are on the order of 0.015 to 0.030 in. in length, while after stamping the fibers may be of infinite length. This difference in length, in combination with the uniform fiber distribution obtained during stamping, leads to important improvements in heat and impact resistance and uniformity of properties.