bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical prediction of pressure loss in pressurized plastic containers
Authors: Fenelon Paul J.
Published: December 2004

Relations describing the time dependence of pressure loss in pressurized plastic containers are presented and discussed. These relations are expected to be useful in predicting the shelf life performance of pressurized plastic containers in applications such as aerosol and carbonated beverage containers. The time dependence of pressure loss in pressurized plastic containers is shown to be dependent on at least three independently contributing factors, namely gas absorption, gas permeation, and material viscoelastic characteristics. The influence of these three qualities is shown to be time dependent and expressions are presented which allow the relative importance of each to be assessed in terms of quantities that are conveniently measured in the laboratory. The pitfalls associated with defining quantitatively the effectiveness of a plastic barrier material as predicted by a steady state analysis is discussed. It is shown that such steady state analysis may be extremely misleading and may not necessarily be a measure of a material's time dependent qualities.
Polyimides: Effect of molecular structure and cure on thermomechanical behavior
Authors: Gillham J. K. , Gillham H. C.
Published: December 2004

The thermomechanical spectra (∼0.5 → 1 cps) of systematically related polyimides synthesized from four aromatic dianhydrides and eleven aromatic diamines are discussed with respect to structure‐property relationships and cure. In displaying two main transitions, Tg and Tβ, most of the polymers behave as amorphous materials such as polymethylmethacrylate. A different mechanism for the relaxations is invoked which involves more intermolecular interaction for those polymers (from pyromellitic dianhydride) which give more complex behavior. Difficulties in obtaining structure‐property relationships in the field of high temperature rigid polymers are discussed in terms of defects in molecular structure, the effect of vitrification in freezing out reactions during cure, different chemical reactivities of the reactive precursor polyamic acids, and the effects of thermal reactions which occur in the vicinity of the glass transition regions.
The SPE international award address—1973 the development of impact polystyrene–a review
Authors: Amos J. Lawrence
Published: December 2004

The development of impact polystyrene and types of processes used is traced from its inception. Our accidental discovery of the process has resulted in the process being termed unique in that no other commercial polymerization has a like phenomenon that occurs in the shearing agitation step. The prior art and patent picture, before and after the issue of the Dow basic patent, is discussed. The litigation that has centered around the patent is reviewed. Information presented shows that this basic process for impact polystyrene has experienced an unusual degree of commercial success and has led to this family of plastics becoming of major commercial importance. These impact plastics have been accepted and used on a global basis.
Free radical formation in oriented polybutadiene during mechanical deformation below Tg
Authors: Mead W. T. , Reed P. E.
Published: December 2004

The tensile behavior of oriented polybutadiene at 83°K is systematically studied as a function of strain rate and pre‐test orientation. Electron spin resonance studies of radical formation are made in conjunction with the mechanical tests. Three different modes of mechanical behavior are observed (brittle, crazing and a second ductile behavior without crazing), depending on test conditions. Radical formation is observed in association with the two ductile modes of behavior. The ESR spectra obtained are attributed to a combination of allyl radicals formed by chain scission between the α‐methylene groups and peroxy radicals. The relative quantity of the two radical species present is thought to be related to the ratio of cis/trans‐isomerism. Stability of the radicals observed with time and with an increase in temperature is studied. Further studies are made of the quantity of environmental test gases absorbed during crazing.
Theoretical model for non‐intermeshing twin screw extruders
Authors: Kaplan Aharon , Tadmor Zehev
Published: December 2004

A simple theoretical model for flow in nonintermeshing twin screw extruders has been derived. The assumptions which in single screw extruders result in the “two parallel plates” model, in twin screw extruders result in the “three parallel plates” model. The flow rate equation can be expressed, for Newtonian fluids, in terms of drag and pressure flow terms, as in single screw extrusion theory, but each term is multiplied by a geometrical factor. This factor incorporates the effect of one screw on the drag and pressure flow terms of the other. The theoretical model was experimentally verified on a 1 inch diameter Bausano twin screw extruder.
The mechanical properties of high‐density rigid polyurethane foams in compression: II. Yield behavior
Authors: Waterman N. R. , Phillips P. J.
Published: December 2004

A series of rigid polyurethane foams of densities varying from 65 kg/m−3 to 400 kg/m−3 have been tested in compression as a function of rate and temperature. Two yield points are observed, the lower one being associated with the surface layers, the higher with the bulk of the material. The yield points may be predicted to a first approximation for the higher density foam using a model based on the buckling of a thinwalled cylinder.
Protein structures and protein fibers—a review
Authors: Huang Frank F. , Rha Chokyun
Published: December 2004

The biochemistry and stereochemistry of proteins are reviewed and related to molecular structure and specifically to the properties governing fiber formation. The conformation of amino acids, polypeptides and proteins are discussed. The amino acid composition of protein is considered in relation to structure, chain length and molecular weight. General descriptions are also given for typical synthetic polypeptides as well as for non‐fibrous natural proteins used in fiber manufacture. Mechanisms and modes are presented for fiber formation including a discussion of molecular criteria involving intermolecular cohesive and crystalline configurational forces which are involved in the fiber forming process. These effects are related to treatments and processes, including thermal, mechanical and chemical modifications, which can be applied to protein for the purpose of forming fibers.
The electret effect in cellulose acetate reverse osmosis membranes
Authors: Wallace Richard A. , Gable Richard J.
Published: December 2004

The electret potentials developed by reverse osmosis electret membranes help control the undesirable deposition of charged colloidal particles on the membrane surfaces during membrane desalination. These antifouling electret membranes should help prevent the costly flux declines normally associated with deposition of colloidal iron oxides on the reverse osmosis membrane surfaces.

Homocharge and heterocharge behavior of cellulose acetate membrane electrets have been studied. Asymmetric reverse osmosis membranes and dense membrane films were studied. The homocharge and heterocharge of cellulose acetate reverse osmosis electret membranes have been explained.
Dynamic model of a plasticating extruder
Authors: Tadmor Z. , Lipshitz S. D. , Lavie R.
Published: December 2004

A theoretical model for the simulation of dynamic operation of a plasticating extruder is proposed. The model can be recommended as a tool to study various dynamic situations of interest in the operation of an extruder. Several responses to changes in operating conditions are discussed. They indicate the occurrence of transient maximas and occasional oscillations. The controlling of flow rate by adjusting a valve at the die seems to cause temporary local high peaks in pressure, whereas its control through screw speed seems to be satisfactory.
Key indicators for plastics performance in consumer products
Authors: Hagan Ralph S. , Thomas James R.
Published: December 2004

Two 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.
The processing and aging of boron/epoxy composite materials
Authors: Jones Joe F. , Bartels Terry T. , Fountain Roger
Published: December 2004

Batch‐to‐batch variations with boron/epoxy prepreg tape are described in terms of uncured and cured matrix chemistry. The effects of thermal and humidity aging on both the chemistry and tensile modulus characteristics of the epoxy matrix are also shown.
Tensile crazing and shear banding of styrene A: Temperature and rate effects
Authors: Sultan J. N. , McGarry F. J.
Published: December 2004

Tensile 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

The 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

A 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

This 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

A 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

Proper 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

Several 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

This 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

Holographic 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

Dynamic 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

Current 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

One 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

Falling 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

The 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

The 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

Elongated 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

Polybenzimidazole 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

Oriented 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

The 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

A 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

Glass 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.
The mechanical behavior of springy polypropylene
Authors: Cannon S. L. , Statton W. O. , Hearle J. W. S.
Published: December 2004

To obtain further details of the unusual behavior of the “hard elastic,” “springy” form of polypropylene (SPP), various loading conditions were studied with an Instron model 1130. Specifically, the variation of the elongation at rupture with change in gauge length and strain rate has been determined. The nature and degree of the specimen hysteresis resulting from various loading cycles have been characterized. The ability of this material to recover from large extensions customarily expected to be permanent deformation has been identified and the time dependency of this recovery has been determined for strain levels of 10, 25, 50, and 100 percent of the original sample length. The effects of submitting the material to conditioning treatments, e.g., immersing in saline solutions of various electrolyte concentrations and autoclaving for 30 min at 250°F and 15 psig have been studied. Characterization of the stress relaxation behavior of the polymer has been made. Fatigue behavior has been identified utilizing a novel testing apparatus which permits load‐cycling of the fiber. Rheovibron work has facilitated calculation of the activation energy of the second order relaxation of SPP from tan δ vs temperature data. Stoll abrasion testing results on SPP tubular knit fabric and multifilament yarn have been compared to normal polypropylene and Dacron®.
Thermoplastic urethane elastomers IV. Effects of cycloaliphatic chain extender on dynamic mechanical properties
Authors: Seefried C. G. , Koleske J. V. , Critchfield F. E. , Dodd J. L.
Published: December 2004

The dynamic mechanical properties of a series of thermoplastic urethane elastomers have been studied as a function of molecular composition and temperature. Polymers based on polycaprolactone diol, an isomeric mixture of tolylene diisocyanate and hydrogenated Bisphenol‐A as the chain extender were prepared at various relative concentrations of hard and soft segments. The glass transition temperatures of these polymers progressively shifted to higher temperatures as the relative hard segment content was increased. This variation was accurately described by the Fox relationship for amorphous copolymers. These results can be interpreted in terms of the relative degree of segregation between the segment of the block copolymers.
Fiber reinforced rubber modified polypropylene
Authors: Speri William M. , Patrick George R.
Published: December 2004

Reinforcement can improve the modulus, heat distortion temperature and thermal expansion coefficient of rubber modified polypropylene. These improvements canbe obtained with a minimum sacrifice in resin ductility and impact toughness. Our studies have shown that reinforcement with small discontinuous fibers can provide a material with a good balance of stiffness and impact strength. The combination of small potassium titanate fiber reinforcement, polypropylene homopolymer and an impact modifier can produce a material with a tensile modulus of 470,000 psi, a notched Izod impact strength of 4.6 ft‐lb/in. and a Gardner imact strength of 320 in‐lb. Glass fiber reinforcement produces similar improvements in stiffness and retains Izod impact strength but drastically reduces Gardner impact strength. Polypropylene resin viscosity has a profound effect on composite impact strength. Transmission electron microscopy showed that a correlation exists between EPDM rubber particle size and impact strength: as rubber particle size is reduced, impact strength is increased. A 5 melt flow rate polypropylene was found to have the viscosity required to adequately shear and disperse the impact modifier. The paper describes an approach to broadening the utility of polypropylene homopolymers. The properties and flow of these materials compare very favorably with medium impact ABS.
Power for multi‐section melt screw extruders
Authors: Kraybill Richard R.
Published: December 2004

Theoretical equations for power dissipation and torque for single and multi‐section screw extruders for Newtonian or slightly non‐Newtonian melts are derived from improved theoretical velocity distributions. Verification of the equations is indicated by experimental data for four single‐section screws of constant channel depth. The power equations can be easily programmed on a digital computer for design or evaluation.
Basic aspects of structure‐property relationships for composites
Authors: Charrier J.‐M.
Published: December 2004

A composite normally consists of a material forming a continuous matrix and a different material in the form of discrete particles. The composite structure is characterized by the proportions of each component, the shape of the particles and their arrangement in space. A generalized way to characterize a particle shape and its position relative to adjacent particles is shown to describe the various geometrical arrangements of two components in space. The components of a composite often have different transport or related properties, i.e., thermal or electrical conductivity, gas permeability, modulus of elasticity, etc. A given property of a composite is a function of the structure of the composite and the corresponding property of each component. Structure‐property analytical relationships are presented and compared. A generalized relationship corresponding to a generalized particle is discussed and shown to be practical and realistic.
Environmental effects on fiber‐reinforced composites
Authors: Heller R. A. , Brinson H. F. , Thakker A. B.
Published: December 2004

The use of fiber‐reinforced composites in structures is discussed with emphasis on the need for a method to obtain long time properties from short time tests. Results of vibration, constant strain‐rate and creep tests are presented for boron epoxy laminates. The data is statistically conditioned and a time‐temperature shifting procedure is used to obtain master curves for response at an individual temperature. Three analytical linear viscoelastic characterization techniques are used to obtain long term creep response from dynamic data. Comparisons between analytical predictions are given for vibration and constant strain‐rate data. Creep predictions are also compared to experimental observations.
Co‐extrusion of unfilled and TiO2‐filled polyethylene: Influence of viscosity and die cross‐section on interface shape
Authors: Minagawa Nobuhiko , White James L.
Published: December 2004

An experimental study of the co‐extrusion of polyethylene and TiO2‐filled polyethylene through capillary and rectangular cross‐section dies has been carried out. The influence of viscosity ratio, cross‐section type, die length and duration of flow has been studied. Low viscosity melts will encapsulate high viscosity melts during flow through cylindrical and rectangular dies. Low viscosity unfilled melts can encapsulate higher viscosity filled melts and low vicosity filled melts can encapsulate higher viscosity unfilled melts. However, the rate and extent of encapsulation seems to be greater for the former case. This may be due to differences in the viscosity‐shear stress behavior of the filled and unfilled melts. In rectangular dies, the extent of encapsulation for any pair is greater when the interface is initially perpendicular to the shorter cross‐section dimension. The results are consistent with the idea that encapsulation primarily depends upon the ratio of die length to initial interface length.
High speed molecular weight distribution
Authors: Dark William A. , Limpert Robert J. , Carter Jordan D.
Published: December 2004

It is now possible to do molecular weight distribution of polymeric material almost as fast as you can put them in solution. μSYRAGEL® has opened a new era in the determination of molecular weight distribution of polymers. With operational efficiencies of 800 plates/min., one can obtain a molecular weight distribution in 15 mins. Combining three of the newest advances in liquid chromatography—solvent delivery, septumless injection, and μSYRAGEL—now makes it possible to use molecular weight distribution as a quality control tool in polymerization and fabrication. The reproducibility of the molecular weight distribution is now good enough that overlays can be done from the raw data. The chromatograms can be used right off the recorder. The reproducibility of the weight average and number average molecular weight is 2–3 percent.
The dry spinning process: Comparison of theory with experiment
Authors: Brazinsky Irving , Williams Albert G. , LaNieve H. Leslie
Published: December 2004

Theoretical calculations based on a mathematical model of cellulose acetate dry spinning were compared with experimental data. Both experiment and theory indicate that the velocity in the spin line becomes essentially constant and equal to the take‐up speed at relatively short distances from the jet. Spin line diameter, however, continues to decrease with increasing axial position. Theory predicts that the filament diameter decreases rapidly at very short distances from the jet, but that the rate of this decrease tends to level off at greater distances. The experimental data exhibit similar trends. In addition, the theoretical and photographically observed spin line die swells are in good agreement. For a typical set of cellulose acetate extrusion conditions, computations show that within relatively short distances from the jet neither the diffusional resistance within the spin line nor the gas side mass transfer resistance in controlling. Both are significant. Calculations also indicate that both the filament and the gas side thermal resistances are important.
The SPE international award address—1975 polymerization by oxidative coupling—an historical review
Authors: Hay Allan S.
Published: December 2004

The history of PPO®, polymers of 2,6‐dimethylphenol, and Noryl® resins is described from the initial discovery through commercialization. The scope of oxidative polymerization as applied principally to phenols and acetylenes is outlined as well as the chemical reactions which can be performed on the resulting polymers.
A Comparison of Gel Permeation Chromatography and Liquid Chromatography for Epoxy Resin Analysis
Authors: Zucconi Theodore D. , Humphrey John S.
Published: December 2004

Gel permeation chromatography and liquid Chromatography are used for analyzing various epoxy resins. The chromatograms are compared with related information available from each. Because the separation is based on different principles, each method gives unique and different information about the same sample. For a complete analysis of epoxy resins, both techniques seem to be required.
High pressure non‐isothermal processing, of linear polyethylenes
Authors: Kulkarni K. M. , Broutman L. J. , Kalpakjian S. , Emery D. B.
Published: December 2004

Articles with increased rigidity can be obtained by compression molding at high pressures as shown by experiments with five types of linear polyethylene. The materials, with weight average molecular weight ranging up to 1,000,000 were molded at pressures as high as 80,000 psi. The material temperature was 149–204°C, and the tooling was at 38°C. The duration of load was typically 3 mins, and the thickness of the molded disks was 12.7 mm. The results show that at high molding pressure the tensile modulus of the material is nearly twice that of materials molded conventionally at low pressures. This increase in modulus occurs for all the materials studied and even for a duration of load of only one min. The causes for this large increase in modulus were investigated with the help of density and melting point measurements and optical and electron microscopy. It was observed that the spherulites showed a distinctive and systematic change with the forming pressure. A hypothesis is proposed to explain the high modulus phenomenon on the basis of the kinetics of spherulite formation.
Extrusion of highly oriented polyolefin fibers
Authors: Collier John R. , Tam Thomas Yiu Tai , Newcome Jonathan , Dinos Nicholas
Published: December 2004

This study demonstrates that it is possible to extrude highly oriented polyethylene fibers using only a plasticating single screw extruder, specially designed and operated dies, and a simple take up mechanism. The degree of orientation achieved is as high as that achieved in solid state extrusion studies but accomplished at a fraction of the pressure. The degree of orientation is significantly greater than that of commercial grade fibers. The orientation is developed in the elongational flow of the “wine glass stem” region preceding the die entrance and is retained by crystallization in the die. Crystallization is inhibited in the pre‐die region by maintaining a temperature above the effective melting point of the flowing, oriented (hence lowered entropy) melt.
New aromatic silicon‐containing polyamides
Authors: Pratt J. R. , Johnston N. J.
Published: December 2004

As part of an ongoing program to prepare and evaluate thermally‐stable, processable materials, 18 aromatic, silicon containing polyamides (structures shown below) have been synthesized via interfacial polymerization of six silicon‐containing diacid chlorides with 3,3′‐diaminodiphenyl‐nethane, 3,3′‐diaminobenzophenone, and l‐(3′‐amino‐benzy)‐4‐(3″aminobenzoyl)benzene. All polyamides were soluble in m‐cresol and N,N‐dimethylacetamide and had glass transition temperatures between 178 and 254°C, Thermogravimetric analyses conducted in static air on film specimens were‐1 used to show 5 and 10 percent weight losses between 331–400°C and 354–440°C, respectively. magnified image

3,3′‐ and 4,4′‐silane isomers

R = R′ = Me; R = Me; R′ = Ph; R = R′ = Ph
Tris‐benzil crosslinked polyphenylquinoxalines
Authors: Rafter R. T. , Harrison E. S.
Published: December 2004

Polyphenylquinoxalines (PPQ) were crosslinked with a tris‐benzil comonomer, to alleviate the inherenthigh temperature thermoplasticity, and evaluated as matrices in graphite reinforced composites. The room temperature flexural strength/modulus of Modmor IJ laminates were as high as 245,000 psi/16,6 × 106 psi. Essentially 100 percent retention of ambient mechanical properties was obtained at 371°C using a PPQ matrix from the fully‐crosslinked polymer prepared from 4,4′‐bis(4″‐oxybenzilyl) benzil (BOBB) and 3,3′‐diaminQbenzrdine. The degree of high temperature thermoplasticity in the composite was found to be more closely related to the final postcure temperature than to the BOBB crosslink density. The thermoplasticity essentially disappeared when the BOBB comonomer‐PPQ laminates were postcured at 482–510°C in nitrogen. Substitution of DMAC for the commonly used m‐cresol solvent system allowed facile preparation of prepreg to fabricate low‐void laminates and NOL rings.
Investigation of the Tll (>Tg) transition in polystyrene by torsional braid analysis
Authors: Gillham J. K. , Benci J. A. , Bover R. F.
Published: December 2004

Investigation of the Tll (>Tg) transition in amorphous poly‐styrene by the technique of torsional braid analysis is reviewed. For the most part, the relaxation behaves like the glass transition (Tg) in its dependence on molecular weight, on average molecular weight in binary polystyrene blends, and on composition in a compatible plasticized system.
The development of an instrumented projectile impact test: Data glass‐reinforced and impact‐modified polypropylene
Authors: Cessna L. C. , Lehane J. P. , Ralston R. H. , Prindle T.
Published: December 2004

Characteristics of several impact test methods in current use are discussed. The construction, operation and performance of an instrumented plate‐projectile (IFF) impact tester is described. Force‐strain curves, energies to any point in the test and failure modes may be inferred from the test data. Also, by inspection of the tested plate, one can see if there are cracks, blanching (development of microvoids) or ductile deformation. This inspection distinguishes between local and catastrophic failure—an important distinction in selection of materials for specific uses. There is reasonable correlation between values from notched Izod and IPP tests, with the latter somewhat more sensitive. Data illustrate the distinction between good and poor fiber‐to‐matrix coupling in reinforced polypropylene. Although there is some sacrifice of impact strength with improved fiber‐matrix coupling, this is more than counteracted by the improvement in static strength and creep resistance. The data show that coupled glass‐reinforced impact grade polypropylene exhibits an interesting balance of static to impact properties.