bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ambient temperature compaction of polycarbonate powder
Authors: Vick Linda W. , Kander Ronald G. 
Published: April 2004

AbstractSolid‐state processing of polymer powders through compaction and sintering has potential advantages over conventional polymer processing methods; however, pressureless sintering of compacted polymer powders has often been unsuccessful. Room temperature compaction of polycarbonate (PC) powder was studied in an effort to better understand the fundamental mechanisms that control polymer compaction and sintering. It was found that differences in the degree of physical aging affect the compaction behavior of PC powder. The results presented in this paper show that the degree of physical aging of thermoplastic polymer powders, which can be influenced by commonly used powder handling operations such as drying and long term storage, can ultimately affect the ability of the powder to be successfully compacted at room temperature.
Reversible optical data storage on poly(ethylene terephthalate)
Authors: Buckley G. S. , Roland C. M. 
Published: April 2004

AbstractA desirable feature of optical data storage processes is that they provide high contrast between the image and background. Thermal marking techniques are inherently advantageous in this regard, because of the nonlinearity of the response. A thermal method for lithography on polymer films has been developed based on selective exposure of the films to infrared laser radiation passing through a mask. Radiation induced crystallization, melting and ablation have been demonstrated with the processes prevailing at different levels of radiation intensity. These methods are capable of producing high resolution images with excellent edge acuity and minimal interference from diffraction. The absence of diffraction effects is due to the nonlinear response of the polymer film to the radiation. The best resolution obtained to date (submicron) is limited by the size of the smallest features present on the masks used to create the pattern. The ultimate resolution achievable by these methods is presently unknown.
Chemorheology of poly(urethane/isocyanurate) formation
Authors: Sun Xiudong , Toth James , James Lee L. 
Published: April 2004

AbstractPoly(urethane/isocyanurate) is a major resin used in the structural reaction injection molding (SRIM) process. In this study, the kinetics and viscosity changes of a poly(urethane/isocyanurate) resin were investigated by the adiabatic temperature/viscosity rise method and differential scanning calorimetry. The effect of the catalyst concentration and the volume ratio of isocyanate to polyol was investigated. It is found that isocyanate trimerization depends on the diffusion effect resulted from the urethane formation. A kinetic model including the diffusion effect is developed, which is able to predict the experimental results. The reaction induced viscosity rise depends on the concentration and the molecular weight of the formed polymer. The measured adiabatic viscosity rise correlates well with the calculated molecular weight growth using the recursive method.
The structure and morphology of syndiotactic polystyrene injection molded coupons
Authors: Evans A. M. , Kellar E. J. C. , Knowles J. , Galiotis C. , Carriere C. J. , Andrews E. H. 
Published: April 2004

AbstractThe structure and morphology of syndiotactic polystyrene (sPS) injection molded coupons have been investigated using wide angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), light microscopy, and laser Raman spectroscopy (LRS). By sectioning the samples at approximately 200 μm increments, profiles across “hot molded” (oil heated to 140°C) and “cold molded” (water heated to 104°C) coupons, could be built up. Using DSC and WAXS, variations in crystallinity and polymorphic phases were observed. The crystallinity was found to remain fairly constant in the “hot molded” samples, whereas the cold molded samples had a pronounced “amorphous” skin, before becoming more uniform towards the center of the specimen. Characterization of the polymers' microstructure, in the molded plaques, was achieved by optical birefringence. The surface of the plaques were successfully etched with an acid/permanganate solution, prior to SEM studies, to reveal their morphology. Overall, the coupons showed very little orientation effects and the structure appeared to be consistent with that of a semicrystalline polymer, crystallized under relaxed conditions.
Synthesis and characterization of epoxy resins containing arsenic acrylate
Authors: Anand M. , Srivastava A. K. 
Published: April 2004

AbstractThe properties of epoxy resins containing arsenic acrylate have been compared with that of a blank epoxy resin (DGEBA). The values of epoxide equivalent, hydroxyl content, hydrolyzable chlorine content, and specific gravity increased, whereas refractive index decreased in the epoxy resins containing arsenic acrylate (AsA3). This is attributed to a complex formation between an As and an oxygen atom in the resin, as evidenced from IR spectroscopy. The reaction is first order (ER3) with an activation energy of 53 kJ/mole. The epoxy resin with As cured with polyamide at 30°C, showed chemical resistance and excellent thermal stability compared with blank epoxy resin (epoxy resin without As).
Effect of processing on weld line strength in five thermoplastics
Authors: Seldén R. 
Published: April 2004

AbstractWeld line strength has been measured in five engineering thermoplastics. The effect of processing parameters was studied using experimental design. Four parameters–holding pressure, injection velocity, melt temperature, and mold temperature–were varied in two levels. For each parameter setting the weld line strength was measured and compared with the bulk strength via a weld line factor (WL‐factor), defined as: strength of specimens with weld line/strength of specimens without weld line. Results from flexural tests on both filled and unfilled materials showed that the weld line factors for cold weld lines varied between 0.25 and 0.98 depending on material and parameter setting. Highest WL‐factors were obtained for unfilled materials and using high melt temperature, high holding pressure, and low mold temperature. Results from instrumented falling weight impact tests on weld lines sometimes showed a WL‐factor higher than 1.0. There was generally a poor correlation between results from impact tests and results from flexural tests.
Use of surface modified recycled rubber particles for toughening of epoxy polymers
Authors: Bagheri R. , Williams M. A. , Pearson R. A. 
Published: April 2004

AbstractThe objective of this research is to investigate the feasibility of using surface treated recycled rubber particles for toughening of epoxy polymers. These particles are obtained through grinding of scrap tires followed by oxidizing the surface of the particles in a reactive gas atmosphere. Surface treated recycled rubber particles with a nominal particle size of approximately 75 μm and a commonly used reactive liquid elastomer, CTBN, have been incorporated in a DGEBA epoxy resin. It has been shown that the recycled rubber particles are not as effective as CTBN in toughening of the epoxy matrix. However, blending of the two modifiers results in a synergistic toughening. Microscopy reveals that, when used alone, recycled rubber particles simply act as large stress concentrators and modestly contribute to toughening via crack deflection and microcracking. In the presence of micron size CTBN particles, which cavitate and induce massive shear yielding in the matrix, however, the recycled particles “stretch” the plastic deformation to distances far from the crack tip. This mechanism causes plastic zone branching and provides an unexpectedly high fracture toughness value. This study, therefore, provides a practical approach for manufacturing engineering polymer blends utilizing the surface modified recycled rubber particles.
Biaxial orientation of linear polyethylenes using the compressive deformation process
Authors: Prins A. J. , Kortschot M. T. , Woodhams R. T. 
Published: April 2004

AbstractThe tensile properties of three grades of linear polyethylene were enhanced by a factor of as much as 15 using a melt/solid phase compressive deformation process that produced equi‐biaxial planar orientation in the sheet. Ultra high molecular weight polyethylene with planar isotropy and an in‐plane modulus of 10 GPa and a tensile strength of 330 MPa was produced using this method. It was found that the molecular weight had a significant influence on the optimum processing temperature, the ultimate biaxial deformation ratio and hence the ultimate tensile properties. High density polyethylene processed under ideal conditions had a tensile modulus of 2.3 GPa and a tensile strength of 250 MPa. The tensile strength increased linearly with increasing biaxial deformation ratio and the tensile modulus increased non‐linearly with increasing biaxial deformation ratio. The deformation rate and the dwell time did not have a significant effect on the tensile properties. Shrinkage tests showed that biaxial deformation was less effective than uniaxial deformation in inducing orientation of the polymer chains, however differential scanning calorimetry results were consistent with the presence of extended chain crystals in very highly oriented ultra high molecular weight polyethylene sheets.
Flow analysis of natural rubber in a capillary rheometer. 1: Rheological behavior and flow visualization in the barrel
Authors: Sombatsompop N. , Tan M. C. , Wood A. K. 
Published: April 2004

AbstractCapillary rheometers have been widely used in the study of the rheological behavior of thermoplastics but their application to rubber has so far been limited. An investigation was therefore carried out to determine the effect of mastication and temperature on the rheological properties of natural rubber using a capillary rheometer. The flow of the rubber in the barrel of the capillary rheometer was observed at various test conditions such as die geometry, piston speed, and test temperature using layers of pigmented rubber compound, this involving the use of a split barrel system. It was found that the flow patterns in the barrel of the capillary rheometer used were very complex and were a function of piston displacement.
Flow analysis of natural rubber in a capillary rheometer. 2: Flow patterns and entrance velocity profiles in the die
Authors: Sombatsompop N. , Wood A. K. 
Published: April 2004

AbstractAn investigation was carried out to determine the effect of variations in test conditions, such as die geometry, for example die entry angles, on the flow patterns observed in the die of a Davenport Extrusion Rheometer. In addition, the velocity profile near the die entrance was determined for different piston displacements. The results indicate that the velocity profile generated in the capillary near the die entrance was parabolic in form. However, there appeared to be a non‐zero velocity at the capillary wall. Melt fracture was observed, this being linked with the appearance of a disturbance in the flow along the capillary, the disturbance being of a converging helical form.
A three‐dimensional analysis of coextrusion
Authors: Gifford W. A. 
Published: April 2004

AbstractThe coextrusion of two polymers in a square channel is presented in this paper. Fluids are fed into the channel through different passages with a plane separating them partway through the channel. Downstream of the separation plane, the streams merge forming an interface between them, which is normally distorted before reaching the exit of the channel. These results show that the degree of distortion depends upon factors in addition to the ratio of the viscosity of the two fluids. The ratio of the flow rates in addition to the shape and location of the separation plane are also important.
Mechanical properties of hand‐cast and reaction injection molded polyurethane and vinyl ester resin interpenetrating polymer networks
Authors: Fan Lian Hua , Hu Chun Pu , Ying Sheng Kang 
Published: April 2004

AbstractA series of simultaneous interpenetrating polymer networks (SINs) composed of polyurethane (PU) and vinyl ester resin (VER) was prepared from different rigid phase components, where the pendent hydroxyl groups of VER were retained or capped, and through different molding processes, i.e., hand‐casting or reaction injection molding (RIM). It was recognized that the occurrence of chemical binding between PU and VER networks through the reaction of the diisocyanate and the pendent hydroxyl groups of VER played an important role in determining the mechanical properties of these SINs. The hand‐cast SINs, with VER containing pendent hydroxyl groups as the rigid phase component and with these pendent hydroxyl groups counted for the metering of diisocyanate besides that due to polyether polyol and chain extender of PU phase, behaved like the hybrid polyester matrix. For the RIM‐molded SIN samples, an obvious reinforcing effect of VER network, whose pendent hydroxyl groups were capped with acetyl groups, upon PU network was observed. These results correlated well with the knowledge of polymerization kinetics and morphology development of these PU/VER SINs.
Structure and strength of a polyethylene pipe grade containing glass spheres and low‐molar‐mass linear polyethylene
Authors: Tränkner T. , Hedenqvist M. , Gedde U. W. 
Published: April 2004

AbstractThe resistance to slow crack growth and to internal over‐pressure of pipes based on a commercial polyethylene gas pipe grade (BPE; 0.6 mol% butyl branches and M̄W = 197,000 g/Mol) blended with both an injection molding grade linear polyethylene (LPE;M̄W = 42,000 g/mol) and 0.5 ± 0.1 mm glass spheres was studied. The blends and the pure polymer components were characterized by density measurements, differential scanning calorimetry, small‐angle X‐ray scattering, and transmission electron microscopy. The fracture properties of extruded pipes were measured using hydrostatic pressure testing and notched uniaxial testing on samples cut from the pipe wall. The polymer components were macroscopically uniformly blended and differential scanning calorimetry indicated the occurrence of partial co‐crystallization between the branched and linear components. Transmission electron microscopy showed molar mass segregation on a 100 nm level. Notched uniaxial testing showed that the slow crack growth resistance of pure BPE was considerably higher than that of the LPE/BPE blend with 30% LPE. Fractography indicated that the fracture‐initiating particles were larger in pipes failing after shorter period of time in the hydrostatic pressure testing. The lifetimes of hydrostatic pressure tested pipes based on the BPE grade containing glass spheres were similar to those of pipes based on the LPE/BPE blend with 30% LPE.
On‐line ultrasonic monitoring of the injection molding process
Authors: Wang H. , Cao B. , Jen C. K. , Nguyen K. T. , Viens M. 
Published: April 2004

AbstractOn‐line ultrasonic monitoring of injection molding of a simple polymer box is studied using pulse‐echo techniques. The flow front of molten polymers inside the mold has been probed by a multiple‐channel probing system with a time resolution of 2 ms. This information can be used to control the plunger movements. The gap development, because of the shrinkage of the part in the mold, is also monitored. This information, which is important for the understanding of the part's cooling process, has been found to be superior than that measured by a conventional pressure probe. The relation between the gap formation time and the packing pressure has been investigated at various part locations characterized by different thicknesses. The velocity and the amplitude variations of ultrasonic waves, in a reflection as well as in a transmission configuration, have also been measured in the part's material during its solidification. The behavior of these ultrasonic parameters contributes to the interpretation of the solidification process.
Injection and compression molding of polystyrene/high‐density polyethylene blends—phase morphology and tensile behavior
Authors: Bureau M. N. , El Kadi H. , Denault J. , Dickson J. I. 
Published: April 2004

AbstractProcessing and compatibilization effects on the phase morphology and the tensile behavior of blends of polystyrene and high‐density polyethylene (PS/HDPE) were investigated. As predicted by theory, high shear rates encountered during extrusion blending led to efficient minor phase emulsification in immiscible PS/HDPE blends for which the viscosity ratio approaches unity. Consequently, the emulsifying effect of a styrene/ethylene‐butylene/styrene (SEBS) compatibilizer was found to be negligible. In the subsequent molding process, disintegration, shape relaxation and coarsening of the minor phase domains were found to be responsible for the morphological evolution. In the compression molding process, morphological observations showed that the rate of minor phase coarsening followed the predictions of the Ostwald ripening theory, in agreement with the rheological analysis. In the injection molding process, minor phase coarsening was attributed to shear coalescence. Tensile tests performed on compression molded and injection molded blends showed that the mechanical behavior of PS/HDPE blends depend strongly upon the matrix orientation as well as the dispersed phase morphology and orientation. In both postforming operations, compatibilization effects on the morphological stability and the tensile behavior of PS/HDPE blends were found to be dependent upon the composition and the rheological behavior of the blend. Evidence of adhesion between the PS and HDPE phases was observed in the presence of SEBS in HDPE‐rich blends.
Predicting the migration of endocrine disrupters from rigid plastics
Authors: Berens Alan R. 
Published: April 2004

AbstractPrevious studies of the diffusion of gases and organic vapors at low concentrations in glassy polymers have established the applicability of Fickian kinetics, the correlation of diffusion coefficients with the dimensions of the diffusing molecules, and the impracticality of experimentally measuring the diffusivities of molecules larger than C6 hydrocarbons. The diffusivities of the suspected endocrine disrupters, p‐nonyl phenol, bisphenol‐A, and tetrachlorodioxin, have been estimated by extrapolation of the established correlations of diffusivity with mean molecular diameter. Estimated diffusivities of these substances in glassy polystyrene, poly(vinyl chloride), and poly(methyl methacrylate) at 30°C range from 10−17 to 10−26 cm2/sec. Calculations of desorption rates, based on Fick's law, show that it would take from several hundred to millions of years for even 1% of the initial content of an endocrine disrupter to migrate from a glassy polymer sheet 1 mm thick. It therefore seems that migration from rigid polymer products should not be considered a significant source of endocrine disrupters in the environment.
Nonlinear mechanical response of high density polyethylene. Part II: Uniaxial constitutive modeling
Authors: Zhang Chuntao , Moore Ian D. 
Published: April 2004

AbstractBased on the experimental data presented in Part I, two uniaxial constitutive models are constructed. The first, a nonlinear viscoelastic (NVE) model, is formulated using the mechanical analogy consisting of one independent spring and six Kelvin elements in series. Creep data are used to determine the model parameters. The second model, a viscoplastic (VP) formulation, is developed using the viscoplastic theory proposed by Bodner to characterize the uniaxial viscoplastic behavior of metals. Inelastic strain rate is introduced into the state variable in addition to inelastic work to depict the strong rate dependent behavior of HDPE. Experimental data from constant strain rate tests are employed to construct the material functions of the model. Limitations in the application of each model are discussed in conjunction with possibilities for future work.
Processing parameters of the diethylenetriamine and unsaturated aldehyde resin
Authors: S̆ebenik Anton 
Published: April 2004

AbstractThe dependence of processing parameters of the reaction between diethylenetriamine (DETA) and crotonaldehyde (CR) or cinnamaldehyde (CA) on reaction time were followed by calorimetric and viscosity measurements. Resins with molecular weights up to 800 g/mol and content of unreacted monomers under 1% were formed. The most reactive were the amino and aldehyde groups. The aldehyde groups are five times more reactive than double bonds. NHCHOH, CH2NH, CHNH, and NCH groups were formed. The rates of the reactions and the rate constants decrease with increasing molar ratio between DETA and unsaturated aldehydes. The heat of the addition of DETA to CR was up to 54 KJ/mol and the total heat of reaction was up to 71 KJ/mol. The heat of addition of DETA to CA was up to 32 KJ/mol and the total heat of reaction was up to 61 KJ/mol. For DETA and CR the activation energy of condensation were 57.3 KJ/mol, and 42.0 KJ/mol for DETA and CA. The viscosity of the final products increased up to hard resins.
Prediction of the stress distribution in an elastic pancake using a neo‐hookean strain energy function
Authors: Kakavas P. A. 
Published: April 2004

AbstractThe aim of this article is to evaluate the axial stress of a thin cylindrical rubber specimen bonded between two steel cylindrical plates. The thickness of the rubber with respect to its diameter is small. It was assumed that the rubber is described by a Neo‐Hookean strain energy function. A theoretical equation was developed to correlate the diametral contraction η with respect to strain ε within the sample. The equilibrium equations of motion and the incompressibility constraint with the free stress condition of R = A were used to determined the axial stress state.
In‐process control of epoxy composite by microdielectrometric analysis
Authors: Stéphan F. , Fit A. , Duteurtre X. 
Published: April 2004

AbstractThe curing of an epoxy prepolymer based on the diglycidyl ether of bisphenol A (DGEBA) with dicyandiamide (DDA) as the hardener and imidazole as the catalyst agent was analyzed using microdielectrometry, differential scanning calorimetry, viscosity measurements, and insolubles in THF for gel‐point detection. Interpreting dielectric data with respect to chemorheology continues to be the subject of scientific discussion. The focus of this issue is to give an industrial point of view on the collected on‐line dielectric measurements during an epoxy/fiber glass composite cure. Hence, isothermal polymerizations of DGEBA/DDA/imidazole resin were examined and dielectric properties such as ionic conductivity were related to the cure kinetics by conversion through an experimentally established equation. This mathematical model was used to predict reaction advancement of epoxy processing under nonisothermal cure conditions. This model is shown to be able to forecast both isothermal and nonisothermal cure data of unaged resin. According to these results, cure monitoring was carried out on prepregs. Whereas some deviations of the law were observed at the time of the last stage of the cure, good correlation was obtained for the reaction rate during the in‐mold process curing time.