bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular structure and morphology of crosslinked polyethylene in an aged hot‐water pipe
Authors: Gedde U. W. , Ifwarson M. 
Published: May 2005

AbstractInternally pressurized crosslinked polyethylene (XLPE) pipes fail according to one of the three following mechanisms: (a) stage I fracture occurs at the highest stresses and is ductile when large defects are absent; (b) stage II fracture is brittle and occurs at intermediate stress levels; (c) stage III fracture occurs at the lowest stress levels and is brittle. It has been assumed that the material in a pipe which fails according to the last mechanism is chemically degraded. This paper presents data obtained by thermal analysis, X‐ray diffraction, infrared spectroscopy, and gel permeation chromatography on samples taken at different radial positions from a pipe of XLPE (crosslinked by peroxide) which failed according to the stage III mechanism after 17,136 h when subjected to 2.62 MPa hoop stress at 110°C (internal water/external air). These data are compared with data from samples of an unexposed reference pipe. Highly degraded brown spots, referred to as “oxidation spots”, are visible in the aged pipe. The puncture fracture occurred in one of these oxidation spots. The increase in melting point and crystallinity, the decrease in fold surface free energy, the almost invariant crystal unit cell, the decrease in gel content, the decrease in molecular weight of the soluble fraction and the formation of carbonyl arid hydroxyl groups at the inner wall in the aged pipe compared with the properties of the unexposed pipe are consistent with an oxidative degradation of the amorphous chain segments including scission of entangled chains and interlamellar tie chains. The latter is the main reason for the major reduction in strength of the aged pipe leading to stage III failure. The thickness of the inner wall layer of highly oxidized material was about 5 mm in the oxidation spots and only 0.5 mm elsewhere in the aged 10 mm thick pipe.
The plane‐strain essential work of fracture as a measure of the fracture toughness of ductile polymers
Authors: Saleemi A. S. , Nairn J. A. 
Published: May 2005

AbstractWe have extended the essential work of fracture technique to allow for the determination of the plane‐strain essential work of fracture. The new technique is to measure the specific work of fracture as a function of ligament length in deeply double edge notched samples. This type of data is then experimentally corrected to remove the plastic work of fracture and leave only the essential work of fracture as a function of ligament length. By extrapolating the essential work of fracture to zero‐ligament length, we claim to be measuring the plane‐strain essential work of fracture. This new technique was applied to two rubber toughened nylons and to a series of polyethylenes. The plane‐strain essential work of fracture was found to be independent of thickness. Where comparison can be made to J‐integral testing, the plane‐strain essential work of fracture was similar to the critical J‐integral, JIc.
Dielectric behavior of epoxy resin during cure: A vector voltage study
Authors: Lee Sung‐Nung , Liao Yunn‐Hsin , Huang Pieng‐Tsung , Lee Jun‐Lung 
Published: May 2005

AbstractVector voltage (Vc), measured across a plate electrode filled with resin, is a function of the resin matrix structure. The variation of Vc during the cure process at various frequencies was studied. A peak with minimum Vc value was observed. It was found that the initial stage of heating is mainly a temperature equilibrating step, where the viscosity decreased to a minimum owing to the rapid alignment of the dipole (and ion) species. Vc then ascended as the major cure reaction took place, as the mobilities of the electrical species were lowered in the rather tight matrix structure of the partially cured resin. The quantity of bound charge is an indicator of dipolar and ionic movements within the resin matrix, and was employed to describe the trajectory of the Vc curve. Bound charge conductance was also found to be the dominating factor in the Vc variation when tests were carried out in a low frequency AC field; whereas free charge conductance became more important for tests at high frequency. It was also observed that the cure phenomenon was not detectable from the Vc variation when monitored with an AC frequency of 38 kHz or higher.
Nonisothermal annual die swelling analysis
Authors: Seo Yongsok 
Published: May 2005

AbstractThe effects of thermal properties of Newtonian liquids on annular die swelling were studied numerically using a finite element method. Fluid viscosity was assumed to be a decreasing exponential in temperature, with a proportionality constant, β, which was assumed to be a material property. Three swelling ratios were found as functions of constant β, Peclet number (Pe), Nusselt number (Nu), and a viscous heat dissipation. The fluid behavior was remarkably different when the viscous heat dissipation was involved or excluded. Explanations are presented for these differences.
Dynamic mechanical response of adhesively bonded beams: Effect of environmental exposure and interfacial zone properties
Authors: Li C. , Dickie R. A. , Morman K. N. 
Published: May 2005

AbstractThe dynamic mechanical response of adhesively bonded metal beams has been examined over a broad temperature range using a dynamic mechanical thermal analyzer (DMTA). The measured dynamic mechanical response of the bonded beam contains rich information about the viscoelastic properties of the adhesive resin such as glass transition temperatures. The measured storage moduli and loss factors of the bonded beams are very sensitive to changes in the properties of adhesive induced by exposing the beam specimens to environmental attack. Dynamic mechanical responses associated with dry adhesive resin, water plasticized resin, and aggregated water were observed for an electro‐galvanized steel/epoxy beam exposed to water. The effect of the presence of an interfacial accommodation zone (IAZ) between adhesive resin and metal substrate was also examined; measured properties were very sensitive to the presence of a low modulus IAZ. It was successfully demonstrated in this study that the DMTA testing of bonded beams is a potentially useful tool for studying dynamic performance and durability of automotive adhesive joints.
Evaluation of poly(1,4‐cyclohexylene dimethylene terephthalate) blends for improved processability
Authors: Auerbach Andrew B. , Sell Joseph W. 
Published: May 2005

AbstractPoly(l,4‐cyclohexylene dimethylene terephthalate) (PCT) exhibits superior heat deflection temperature when compared to conventional polyesters such as poly(butylene terephthalate) or poly(ethylene terephthalate). It is subject to degradation, however, at the processing temperatures normally employed to extrude or mold this material. Several approaches were taken to broaden the processing window of this material including: blending PCT with other crystalline and amorphous polymers to allow for lower processing temperatures, addition of conventional stabilizers, addition of crosslinking agents to maintain viscosity during processing and the addition of lubricants to improve processing. Key parameters included physical properties, rate of degradation, extruder torque measurements vs. time, and Differential Scanning Calorimetry (DSC) analysis (melting point and glass transition). All systems tested produced significant reduction of the intrinsic viscosity (molecular weight) for PCT during processing. The most successful approach was the blending of various polymers with PCT to lower extruder processing temperatures. Reductions in processing temperature may have resulted from improved heat transfer due to the presence of a lower melting polymer, reduction in melting point of the blend, or changes in the frictional characteristics of the PCT in the extruder. Transesterification may have played a role in compatibilizing some polyester mixtures. As expected, certain polymers had major'effects on the flow behavior of the blend. Tradeoffs were obtained in physical and thermal properties. A combined approach of polymer blending and the use of lubricants, stabilizers or crosslinking agent may hold the most promise for future development work. Thermal resistance under vapor phase soldering conditions was best for LCP/PCT blends and worst for PBT/PCT blends. Additional evaluations of the blend materials will include solvent resistance, processability, thermal resistance, dimensional stability, heat aging resistance, flammability, and specific end use tests.
Polymeric stannous dicarboxylates: Synthesis, properties, and structure
Authors: Ibidapo T. Adesanya 
Published: May 2005

AbstractA series of polymeric stannous dicarboxylates (i.e., suberate, sebacate, do‐decanedioate, terephthalate, propoxyterephthalate, and isophthalate) has been synthesized from aqueous solution using various conditions of temperature (20, 50, and 98°C) and pH (6.4, 8.0, and 11.6). These were obtained as highly viscous adhesive‐like emulsion phases when synthesized at 50 and 98°C. Polymeric stannous suberate when synthesized at pH 11.6 and temperature of 50°C crystallized to spherulites. When molten they behaved like hot‐melt adhesives. They could be spun into fibers. On the other hand, melt‐synthesized stannous dicarboxylates exhibit simple non‐polymeric salt structures.
Conduction melting of polymer pellets
Authors: Chung C. I. , Wang N. 
Published: May 2005

AbstractA study of melting a polymer pellet immersed in a hot silicone oil bath was conducted. The temperature rise at the center of the pellet was recorded. This experiment simulates the conduction melting mechanism of polymer solid pieces mixed in the hot melt inside an extruder screw channel. The pellets immersed in the silicone oil melted quite slowly, taking around one minute to melt a spherical pellet of about 4.5 mm diameter. The heating time could be greatly decreased by stirring the silicone oil to increase the heat transfer from the silicone oil to the pellet. Analysis of the conduction melting mechanism showed that the size reduction of the solid would be most effective in decreasing the heating time.
Mechanics of neck formation in the cold drawing of elastic films
Authors: Coleman Bernard D. , Newman Daniel C. 
Published: May 2005

AbstractA discussion is given of the unidirectional, but nonuniform stretch of long, wide strips of film. It is observed that each of the material functions, τ, β, γ, in a recently proposed unidimensional theory of neck formation and cold drawing for bars of small but not zero thickness is determined, in the case of a strip of film, by the strain‐dependent shear modulus μ of the three‐dimensional material of which the bar is composed. The dependence of the shear modulus μ on shear strain and of τ, β,and γ on axial stretch is evaluated for a model of an elastic material susceptible to cold drawing, and the calculated values of τ, β,and γ, are used to draw film profiles for various stages of neck formation.
Comments on “fracture toughness of impact modified polymers based on the J‐integral”
Authors: Huang D. D. , Williams J. G. 
Published: May 2005

AbstractIn (1), Narisawa and Takemori examined the physical interpretations and some experimental techniques of the J‐Integral (ASTM E813‐81) as applied to toughened polymers. Their results and conclusions are reexamined and discussed in terms of recent developments in J testing.
3‐D flow analysis of non‐newtonian viscous fluids using “enriched” finite elements
Authors: Gupta Mahesh , Kwon Tai H. 
Published: May 2005

Abstract‘Enriched’ element, Q1+Po, and ‘standard’ element, Q1Po, are compared for the simulation of 3‐dimensional flow of non‐Newtonian fluids. Several 3‐dimensional polymer flow problems are analyzed. The pressure field obtained by using Q1Po elements suffers from spurious pressure modes. For complex flows, depending upon the flow geometry and the boundary conditions used, Q1+Po elements may fall to simulate even the velocity field. Q1Po elements, which satisfy the Babuska‐Brezzi condition, give accurate velocity and pressure distributions for all the problems analyzed here.
How molecular weight distribution and drawing temperature affect polypropylene physical properties and morphology
Authors: Flood John E. , Nulf Steven A. 
Published: May 2005

AbstractThree polypropylene polymer samples possessing three different molecular weight distributions (MWD) ranging from narrow to broad, but having the same melt flow, were studied. The three resins were used to produce uniaxially oriented stretched tapes, which were evaluated for physical properties and morphological characteristics. In addition, five different drawing temperatures were used to investigate the effect of temperature on the physical properties and molecular morphology of the tape. As the MWD became broader, the tape modulus and tenacity increased slightly and the percent elongation and shrinkage decreased slightly. These effects were attributed to decreases in molecular mobility and increases in the number of tie molecules present in broad MWD resins. Morphological studies determined that the crystalline orientation was not affected by MWD. However, the amorphous orientation, at higher draw temperatures, demonstrated a small increase as the MWD became broader. MWD did not have a large effect on the percent crystallinity but the long period spacing (LPS) did exhibit a small decrease as the MWD broadened.
Mold pressurization as a method to reduce warpage in rotational molding of polyethylene
Authors: Chen Chih Hung , White James L. , Ohta Yasuhiko 
Published: May 2005

AbstractWarpage and global shrinkage of rotationally molded polyethylene parts can be a serious problem with resins of higher densities with rapid quenches and high mold wall thicknesses. It is shown that relatively low pressurization of molds substantially reduces the warpage of molded polyethylene parts. Samples cut out of parts produced in pressurized molds have the same density distributions, Izod Impact, and uniaxial stress‐strain characteristics as parts fabricated in unpressurized molds.
Blow molding die design for non‐axisymmetric parison extrusion
Authors: Nguyen K. T. , Kamal M. R. 
Published: May 2005

AbstractThe flow distribution in a coat‐hanger die is predicted using a three‐dimensional finite element technique. An iterative procedure is proposed for designing blow molding dies for a non‐axisymmetric parison to provide uniform outflow at the exit. A similar procedure is applicable to dies for film, sheet, or profile extrusion. Comparison with one‐dimensional models show significant differences. The effect of nonlinearity on the multiplicity of solutions and the effect of power law index have been considered.
An experimental study on plasticating single‐screw extrusion
Authors: Han Chang Dae , Lee Kee Yoon , Wheeler Norton C. 
Published: May 2005

AbstractAn experimental study was conducted with a plasticating single‐screw extruder, which had the following screw dimensions: (a) the diameter (D) of 6.35 cm; (b) the total extruder length of 24 D; (c) the length of the feed section of 3 D; (d) the length of the tapered section of 4 D; and (e) the length of the metering section of 17 D. The extruder had nine pressure transducers which were mounted, almost equally spaced along the extruder axis, on the wall of the extruder barrel, so that we could measure axial pressure profiles during extrusion. Also measured in our study were the solid‐bed width profiles in the screw channel by conducting tracer experiments (i.e., screw ‘pushout’ experiments). For the study, a high‐pressure low‐density polyethylene and a high‐density polyethylene were used. Experimental results were analyzed using the reported Lee‐Han melting model. Theoretical predictions of axial pressure profiles were found to be in good agreement with results. Of particular note are the theoretical predictions that for the particular screw configurations used, which has short feed and tapered sections, and extrusion conditions employed, there was considerable solid‐bed acceleration in the tapered section of the screw.
Thermal contact resistance in injection molding
Authors: Yu Chi J. , Sunderland J. E. , Poli C. 
Published: May 2005

AbstractThis paper describes a method for obtaining the thermal contact resistance (TCR) between an injection molded part and its mold. Due to the absence of TCR the simulated cooling times obtained from Polycool II, a computer aided engineering (CAE) package for cooling simulation of injection molding, have compared poorly with both field and experimental data. This paper shows that an improvement in the accuracy of the simulated data results from making TCR an Input to Polycool II. TCR was obtained through a combination of experimental and analytical procedures. Experimental work was performed to obtain the part surface temperature distribution and the inside cavity pressure gradient. The part surface temperature distribution was then used as a boundary condition in the thermal analysis. The inside cavity pressure gradient was utilized as a basis for determining the inside cavity shrinkage. The results show that due to the thermal expansion of thermoplastics, the compressibility of the plastic melt, and the mold deformation, the inside cavity shrinkage is reduced as the thickness of the part is increased. Therefore, the TCR value of a thicker part is lower than that of a thinner part. The effects of both part thickness and process parameters, such as temperature and pressure, on TCR are also discussed.
An improved flow analysis network (fan) method for irregular geometries
Authors: Lee Ching‐Chih 
Published: May 2005

AbstractThe flow analysis network (FAN) method developed in earlier work, for simulating the isothermal flow of a generalized Newtonian fluid in a narrow‐gap region has been refined to better account for irregularly shaped flow boundaries. The resulting equation, which involves only pressure as an unknown, is solved by successive relaxation; the velocity distribution is then back calculated from pressure values. For Newtonian fluids, overrelaxation with a relaxation factor of 1.75 gives the fastest numerical convergence. For power‐law fluids, it is suggested that one start with the associated Newtonian solution and then use under‐relaxation with a relaxation factor equal to the power‐law index. The FAN solutions for two test problems compared very well with analytical and finite element solutions. The rubber flow in a cavity was analyzed using the FAN program. Compared to a Newtonian fluid, a shear‐thinning fluid gave a larger velocity variation across the flow channel exit due to a stronger dependence of velocity on pressure gradient. Through iterations, the output ratio and velocity uniformity were improved without causing too long residence time.
The design and manufacture of a graphite fiber reinforced poly(ether ether ketone) (PEEK) tetrahedron truss array
Authors: Duthie A. C. , Damon J. 
Published: May 2005

AbstractOrbital space structures are required to be lightweight, have high specific stiffness, have near‐zero coefficient of thermal expansion, exhibit low outgassing, and be cost‐effective. Graphite‐reinforced thermoplastics have the potential to satisfy the criteria noted. However, prior to committing the materials to specific projects, technology demonstration and risk reduction is necessary. In order to demonstrate the application of fiber‐reinforced thermoplastic composites for truss structure applications, a graphite‐reinforced poly(ether ether ketone) (PEEK) composite tetrahedron truss array was designed and manufactured. The resulting structure clearly demonstrated that fiber‐reinforced thermoplastic composites are a viable alternative to epoxy composites for orbital structures.
Photothermal methods for the measurement of thermal properties of thin polymer films
Authors: Coufal H. 
Published: May 2005

AbstractThe absorption of radiation in a sample gives rise to local heating. With a suitable modulated or pulsed source of radiation, a spatially well defined instantaneous heat source can be readily implemented. Radiation induced thermal transients are, therefore, the ideal heat sources for studies of thermal processes in thin films. Application of this method for measurements of thermal diffusivity and temperature dependent properties of thin polymer films are discussed. Imaging of inhomogeneities and depth profiling are another important area of application for these techniques. A number of applications emphasizing the various photoacoustic and photothermal techniques, their advantages and drawbacks are covered in detail.
Tensile yield in poly(chlorotrifluoroethylene) and poly(vinylidene fluoride)
Authors: Hartmann Bruce , Lee Gilbert F. 
Published: May 2005

AbstractUniaxial tension tests to the yield point were performed on poly(chlorotrifluoroethylene) (PCTFE) and poly(vinylidene fluoride) (PVF2) from room temperature to near the melting point at a strain rate of 2 min−1. At room temperature and at least two elevated temperatures, measurements were also made at strain rates from 0.02 to 8 min−1. The properties of these polymers were found to be similar to those of other semicrystalline polymers. In the absence of other transitions, yield energy was found to be a linear function of temperature extrapolating to zero near the melting temperature. The ratio of thermal to mechanical energy to produce yielding is smaller than for glassy polymers. Yield stress is a linear function of log strain rate. The ratio of yield stress to (initial) Young's modulus is about 0.03 at room temperature for both polymers. Yield stress is a linear function of unstrained volume. Yield strain, elastic, and plastic strain all initially increase with temperature, but PCTFE shows a decrease with temperature starting at about 100°C, thus behaving like a glassy amorphous polymer in this region.
Effect of rubber/matrix interfacial modifications on the properties of a rubber‐toughened epoxy resin
Authors: Chen Teng Ko , Jan Yi Hung 
Published: May 2005

AbstractThe interface of a rubber‐toughened epoxy resin was modified by using epoxide end‐capped carboxyl‐terminated butadiene and acrylonitrile random copolymer (CTBN). The end‐capping epoxides were formulated with different ratios of flexible diglycidyl ether of propylene glycol (DER732) and rigid diglycidyl ether of bisphenol‐A (Epon 828). The microstructure and the fracture behavior of these rubber‐modified epoxy resins were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The thermal and mechanical properties were also investigated. With an increase in the amount of end‐capping DER732, the interfacial zone of an undeformed rubber particle and the degree of cavitation of the rubber cavity on the fracture surface were greatly increased. At the maximal addition of DER732, fracture energy (GIc) for this toughened epoxy resin containing 10phr CTBN rubber increases up to 2.4 fold compared to that of a conventional CTBN‐toughened epoxy resin, but the thermal and the mechanical properties remained quite unaffected. The modification on the interfacial property provides a new technique in the improvement of fracture toughness of a rubber‐toughened epoxy resin.
Orientation and properties of acrylonitrile copolymers
Authors: Jabarin Saleh A. 
Published: May 2005

AbstractThe orientation characteristics and the physical properties of acrylonitrile copolymers are studied as a function of orientation temperature, stretch ratio, and rubber modification content. The mechanical, barrier, and thermal properties are evaluated and discussed with respect to the influence of rubber content on these properties. The data indicate unique differences in the orientation behavior of rigid and rubber‐modified copolymers. An explanation of these differences is offered on the basis of microscopy and dynamic mechanical analysis.