bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of morphology, crosslink density, and miscibility on interpenetrating polymer network damping effectiveness
Authors: Fay J. J. , Murphy C. J. , Thomas D. A. , Sperling L. H. 
Published: December 2004

AbstractThe areas under the linear loss modulus versus temperature curves (loss area, LA) and tan δ versus temperature curves (TA) were evaluated for a number of acrylic, methacrylic, styrenic and butadiene based copolymers and interpenetrating polymer networks, IPNs, as a function of crosslink density and comliosition, and were compared with values predicted by group contribution analysis. The LAs of the sequential IPNs, cross‐poly(n‐butyl methacrylate)‐inter‐crosspolystyrene, were found to exhibit up to 30% larger LAs than the poly(n‐butyl metacrylate‐stat‐styrene) copolymers, which had LAs slightly less than the values predicted from the group contribution analysis. At constant chemical composition (50% n‐butyl methacrylate, 50% styrene), LA equals 14.4 GPa K for the IPN, attributed to a synergistic effect resulting from the IPN's microheterogeneous morphology, as compared with 10.7 GPa K for the single phase, miscible copolymer. Increases in the LA with increased concentration of polymer, network II were also observed for cross‐poly(ethyl acrylate)‐inter‐crosspolystyrene and cross‐polybutadiene‐inter‐cross‐polystyrene IPNs. On the other hand, cross‐polybutadiene‐inter‐cross‐poly(methyl methacrylate) IPNs had LAs much lower than were predicted by the group contribution analysis, which were attributed to lower miscibility in this system relative to the other systems evaluated. In general, decreased crosslink densities and lower concentrations of network II increased TA. These findings demonstrate how the morphology of a multiphase polymeric material can affect LA and TA, with significant increases In damping capability over the average of the component polymer values.
Simultaneous acoustic wave propagation and dynamic mechanical analysis of curing of thermoset resins
Authors: Chow Andrea W. , Bellin Jack L. 
Published: December 2004

AbstractA study of simultaneous acoustic and rheometric (dynamic mechanical) measurements of the epoxy curing process is undertaken to assess the validity of using acoustic cure‐monitoring sensors for process control. Our results demonstrate that the acoustic technique provides a sensitive means for monitoring the cure of neat epoxy over the entire cure cycle. The acoustic modulus calculated from the shear velocity qualitatively tracks the mechanically measured dynamic modulus and correctly ranks the stiffness of two epoxy compositions. When the frequency difference is accounted for, using time‐temperature superposition of the dynamic mechanical measurements, quantitative agreement between the acoustic and mechanical moduli for fully cured epoxy resins is also quite good.
Determination of ejection temperature and cooling time in injection molding
Authors: Yu Chi J. , Sunderland J. E. 
Published: December 2004

AbstractEstimation of cooling time for a given injection molding part is becoming increasingly important, especially when a large number of parts are produced. In order to calculate the cooling time, the ejection temperature should be known. However, to date, there is no easy way to obtain the ejection temperature even though the material selected and part thickness are known. This study uses a combination of experimental, analytical, and statistical means to establish equations for calculating ejection temperature according to material properties, part thickness, and molding conditions such as injection and mold temperatures. Therefore the cooling time of a given injection molding part can be estimated in its early design stage.
Quantitative measurement of voids formed during liquid impregnation of nonwoven multifilament glass networks using an optical visualization technique
Authors: Mahale Anant D. , Prud'Homme Robert K. , Rebenfeld Ludwig 
Published: December 2004

AbstractA technique based on matching the refractive index of an invading liquid to that of a fiber mat has been used to study entrapment of air (“voids”) that occurs during forced in‐plane radial flow into nonwoven multifilament glass networks. The usefulness of this technique is demonstrated in quantifying and mapping the air pockets. Experiments with a series of fluids, with surface tensions varying from 28 × 10−3 to 36 × 10−3 N/m, viscosities from 45 × 10−3 to 80 × 10−3 Pa · s, and inlet flow rates from 0.15 × 10−6 to 0.75 × 10−6 m3/s, have shown that void content is a function of the capillary number characterizing the flow process. A critical value of capillary number Ca = 2.5 × 10−3 identifies a zone below which void content increases exponentially with decreasing capillary number. Above this critical value, negligible entrapment of voids is observed.
A local theory of heating in cross‐ply carbon fiber thermoplastic composites by magnetic induction
Authors: Fink Bruce K. , McCullough Roy L. , Gillespie John W. 
Published: December 2004

AbstractFor joining and repair of continuous fiber thermoplastic composites, induction heating has been viewed a strong candidate. Induction heating employs an applied alternating magnetic field, which induces a rotational emf in a grid of conductive carbon fibers, which are then used to carry resulting currents. In continuous carbon fiber crossply composites the available paths for “eddy current” loops are along the network of conductive carbon fibers. For this to occur, an electrical transfer must take place between crossing fibers in adjacent plies. Tests involving variable thicknesses of interply neat film layers have been performed to provide insight into the mechanisms taking place. These tests indicate that the primary mechanism for heating in such laminates is dielectric losses in the polymeric region between fibers in adjacent planes that form the conductive loop. Therefore, heating is not uniform in such composites despite a uniform magnetic flux. Heating patterns were viewed using liquid crystal materials and E‐type thermocouples. Several factors leading to nonhomogeneous thermal distributions have been considered, including current density effects, internal emf cancellation, and rotational field effects. Global and local considerations are addressed, a localized model is proposed, and the corresponding theory is developed qualifying the early results. Additional testing has supported the theory.
Transcrystallinity phenomena in a polypropylene/kevlar fiber system. I: Influence of crystallization conditions
Authors: Avella Maurizio , Della Volpe Gaetano , Martuscelli Ezio , Raimo Maria 
Published: December 2004

AbstractThe isothermal crystallization from the melt of isotactic polypropylene in the presence of Kevlar 49 fibers has been investigated. The nucleating ability of the fibers was demonstrated, and the presence of extensive transcrystalline regions was related to crystallization parameters, such as crystallization temperature, melt precrystallization temperature, and residence time at precrystallization temperature. The results are discussed in terms of the presence of heterogeneities in the bulk and preformed self‐seeded nuclei located in the anfractuosities of fiber surfaces.
A mixing model for multicomponent reactions in twin screw extruders applied to the polymerization of urethanes
Authors: Ganzeveld K. J. , Janssen L. P. B. M. 
Published: December 2004

AbstractTo understand the performance of multicomponent reactions in twin screw extruders the mixing mechanism in the extruder had to be understood. Therefore, two new relevant mixing parameters are defined; the mixing efficiency, which is the average number of passages of material through a high shear region; and the mixing deficiency, which is the fraction of material that does not pass through a high shear region. With these parameters an analysis can be made of the mixing circumstances in the extruder. The new model was applied to the polymerization of urethanes in a counter‐rotating twin screw extruder. The results agreed very well with the theoretical expectations.
Improving adhesion between thin chromium film and polyimide substrate by Ar+ irradiation
Authors: Koh S. K. , Pae K. D. , Caracciolo R. 
Published: December 2004

AbstractAr+ irradiation and annealing at an elevated temperature are used to improve the adhesion of deposited Cr thin films by vacuum evaporation onto polyimide (PI) substrates. The Ar+ ions of 50 and 200 keV and various Ar+ doses ranging from 1 × 1013 to 2 × 1016 ions/cm2 are chosen for the experiments, after many preliminary trials. The surface analyses are conducted employing Rutherford Backscattering Spectroscopy (RBS), Fourier transform infrared spectrometry (FTIR), X‐ray photoelectron spectroscopy (XPS), and Scanning electron microscopy (SEM). Ar+ irradiation produces an interfacial layer of about 100 Å (10 nm) thick in which Cr particles and PI molecules are physically mixed and chemically bonded. The chemical bonds of CrO and a trace of CrC are observed by XPS and FTIR. Impact‐wear tests are also conducted in order to determine the effects of the Ar+ irradiation on the wear property of a Cr/PI system. A significant increase in the property is observed and the increase appears to be a function of the degree of adhesion of the Cr film to the PI substrate.
Flow birefringence in polymer rheology
Authors: Subramanian R. , Wilson D. R. , Picot J. J. C. 
Published: December 2004

AbstractBased on a linear stress‐optical relation, off‐center and centerline velocities along with the orientation angle measurements (via the birefringence method) can be used to test constitutive equations for polymeric melts without the need to measure viscosity hood stresses directly. For polydimethylsiloxane (Dow Corning type 200 grade 300 Pa · s) melt in a 60° wedge flow cell (inward flow) at a pressure drop of 70 psi, the orientation angles computed by the Power‐Law model and Goddard‐Miller model with two terms in the Taylor Series and a single relaxation time of 0.005 s were compared with the experimentally measured values. It was found that the Goddard‐Miller model agreed quite well with the measured data. The stress‐optical coefficient (C) was evaluated from the velocity, birefringence, and orientation data. It was calculated to be 1.44 × 10−10 m2/N for combined shear and extension using the two‐term Goddard‐Miller Model. For centerline flow (purely extensional), the zero‐extension‐rate elongational viscosity (η0) was calculated to be 930 Pa · s, slightly greater than three times the zero‐shear‐rate viscosity (η0). The cell can be adapted for transient flow experiments.
CO2 laser welding of polymers
Authors: Duley W. W. , Mueller R. E. 
Published: December 2004

AbstractDeep penetration welding of polymers can be carried out at high speed with relatively low laser power. This results from an efficient coupling CO2 laser radiation to polymers that leads to volume heating. A brief review of energy coupling and heat transfer effects in polymers under CO2 laser welding conditions is given. Some examples of low power (10 to 100 watt) CO2 welding of polypropylene and polyethylene at depths of up to 1.5 cm are discussed.
Strength model of adhesive‐bonded double‐lap joints under cantilevered bending
Authors: Yang C. , Pang S. S. , Griffin S. A. 
Published: December 2004

AbstractThe objective of this study was to develop mathematical relations for predicting the strength of adhesive‐bonded double‐lap joints under cantilevered bending. Based on the strength of composite materials theory, two models were proposed to predict the stress‐strain distribution and vertical deflection of the laminates and the adhesive under this loading condition. The first model was based on the basic beam theory with the assumption that every cross section in a plane before bending remains plane after the bending load is applied. In the other model, a strain gap between each bonded surface is assumed. Based on the second model and the predicted peel failure mode, the effects of shear modulus of the adhesive, joint length, and adhesive thickness on the joint strength were evaluated. Scotchply composite laminates were used as the adherends of the double‐lap joints in the experimental investigation. An Instron machine fitted with a special apparatus was used for conducting the experiments. By the attachment of strain gages to the adherends and through the use of a dial indicator, the theoretical models were verified experimentally.
Molecular structure, morphology, and antioxidant consumption in medium density polyethylene pipes in hot‐water applications
Authors: Karlsson K. , Smith G. D. , Gedde U. W. 
Published: December 2004

AbstractChanges in polymer structure and antioxidant concentration have been systematically studied as functions of temperature, hoop stress, exposure time, and location in pipe wall on pressure tested pipes of medium density polyethylene. The pressure tests have been performed with water as the internal medium and air as the external medium at temperatures in the range 80 to 105°. Infrared spectroscopy shows that oxidation is initiated at the inner wall surface just prior to the onset of the so‐called stage III fracture. X‐ray diffraction and size exclusion chromatography show that oxidation involves only the amorphous phase and results in a significant molar mass reduction. The near‐inner‐wall material exhibits a 10% reduction in mass average molar mass before the onset of stage III fracture and thereafter a more dramatic decrease. Oxidation induction time measurements by differential scanning calorimetry show that the antioxidant concentration is almost twice as high in the center of the wall as in the near‐inner‐wall and outer‐wall material of the unexposed pipe, that the loss of antioxidant is anomalously rapid at the beginning of the high temperature exposure, and that the antioxidant concentration profile gradually becomes more skewed towards the outer wall on prolonged exposure. The data presented in this paper are used in a parallel paper for modeling purposes.
Dynamic mechanical analysis of polypropylene composites based on surface‐treated sepiolite
Authors: Morales E. , Ojeda M. C. , Linares A. , Acosta J. L. 
Published: December 2004

AbstractThe dynamic mechanical properties in terms of the storage modulus G′, loss modulus G″, and loss tangent δ have been studied for polypropylene‐sepiolite composites. The effect of surface treatment on the relaxation spectra has been elucidated, and quantitative values indicating the extent of polymer‐filler interaction have been given. Analysis of the results show that the addition of sepiolite leads to an increase in the values of the modulus, a value of the glass transition temperature lower than that of unfilled polypropylene, and displacement towards higher temperatures of the αc relaxation associated with the crystalline regions. Surface treatment of the sepiolite, by esterification with organic acids of different chain length, does not have a marked effect on the relaxation spectra of the composites, even though the polymer‐filler interaction parameter decreases with respect to untreated sepiolite.
Effects of compatibilizers on the properties of polyamide/polypropylene blends
Authors: Holsti‐Miettinen R. , Seppälä J. , Ikkala O. T. 
Published: December 2004

AbstractCompatibilization of polyamide 6/isotactic polypropylene blends was investigated by mechanical, morphological, thermal, and rheometrical methods. The primary objective was to obtain blends combining the desirable properties of the two components. Four compatibilizers including maleic anhydride, fumaric acid, or glycidyl functionalities were applied at two concentrations (5 and 10%). Maleic anhydride grafted styrene‐ethylene‐butylene‐styrene block copolymer (SEBS‐g‐MAH) was observed to give excellent mechanical properties, especially at high polyamide/polypropylene ratios. The correlation between morphology and mechanical and rheological properties is discussed, and the interesting effect of blending on the kinetics of crystallization is noted.
Morphological, thermal, and rheological properties of nylon/acrylonitrile‐butadiene‐styrene alloys
Authors: Aoki Yuji , Watanabe Makoto 
Published: December 2004

AbstractMelt blends of nylon‐6/modified ABS (acrylonitrile‐butadiene‐styrene terpolymer) have been prepared using a single screw extruder. Electron microscopic observations revealed that the rubber particles are as finely dispersed as in ABS. Both the heat of fusion and the dynamic storage modulus of the blends were linear functions of the blend composition. The melting point of nylon crystallites and glass transition temperatures of poly(acrylonitrile‐co‐styrene) (AS) and the rubber phase in ABS and the amorphous phase in nylon were almost independent of the composition. Very high Izod impact strength was achieved over a broad compositional range. These facts suggest that the nylon and the modified ABS are not mixed on a molecular level although there must be sufficient interaction between them. The melt viscosities were increased with an increase in the ABS component. In the region of less than 65% ABS, the viscosities bend off to the zero‐shear viscosity at low shear rates. Above 65% ABS, the viscosity curves were expressed by a power law fluid. The power law index decreased with an increase in the ABS content. The activation energy of flow vs. composition curve indicated a discontinuous point between 60% and 70% ABS. The phase inversion takes place at about 65% ABS, judging from the rheological point of view.
Blends of polycarbonate with poly(methyl methacrylate): Miscibility, phase continuity, and interfacial adhesion
Authors: Kolarik Jan , Lednicky Frantisek , Pukanszky Bela , Pegoraro Mario 
Published: December 2004

AbstractDynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) concurrently show that polycarbonate (PC)/poly(methyl methacrylate) (PMMA) blends have a two‐phase structure. The differences between the Tgs of parent polymers and the Tgs of conjugate phases, determined by both DMTA and DSC, indicate a limited miscibility of components and allow the approximate composition of conjugate phases to be calculated. The Flory‐Huggins interaction parameter calculated by using these data assumes values about 0.035 ± 0.010. Phase inversion occurs in an interval close to the 50/50 composition, though the molar masses and melt viscosities of the polymers were rather different. Partial miscibility of components ensures interfacial adhesion capable of sustaining the stress transfer between phases up to fracture. Yield stress of the blends is very close to values foreseen by the rule of mixtures. A specific feature of the blends studied is that the addition of 10 to 20 vol% of PMMA to PC increases the strain at break and work to fracture, which are rather low for the PC used. The enhanced capability of the blends to absorb mechanical energy is probably linked to plastic deformation of the dispersed PMMA.
Shear‐rate‐dependence modeling of polymer melt viscosity
Authors: Hieber C. A. , Chiang H. H. 
Published: December 2004

AbstractSteady‐shear‐viscosity data sets for commercial‐grade acrylonitrile‐butadiene‐styrene terpolymer, nylon, polycarbonate, poly(methylmethacrylate), and polystyrence are fitted in terms of a generalized Cross/Carreau modeling for the shear‐rate dependence. Based upon extensive data sets from the open literature as well as in‐house measurements, it is shown that the shear‐rate dependence can be more accurately described in terms of the Cross rather than Carreau model. Although the resulting viscosity fits based upon these two models might differ by 20% or more for the same well‐characterized data set, the resulting effect upon simulating the injection‐molding process is found to be much smaller since such predictions reflect a range of shear stresses (varying linearly from centerline to wall of cavity) over which the two models alternate in relative magnitude. This is demonstrated by detailed representative numerical predictions which are presented for both the filling and post‐filling stages.
Effects of polyethylene molecular structure on peroxide crosslinking of low density polyethylene
Authors: Bremner T. , Rudin A. , Haridoss S. 
Published: December 2004

AbstractThe effects of molecular structure on the dicumyl peroxide crosslinking of two low density polyethylenes have been studied. Peroxide efficiency was determined largely by the content of terminal vinyls in the two polymers. Differences in molecular weight distribution and branch content had comparatively little influence on the gel content but hot creep resistance of the vulcanized materials was affected. Scorching was affected, also, by the presence of vinyl unsaturations in the polymer.
Structure and mechanical properties of highly oriented poly(ethylene terephthalate) films
Authors: Evstatiev M. , Fakirov S. , Apostolov A. , Hristov H. , Schultz J. M. 
Published: December 2004

AbstractThe relationships between the supermolecular structure of poly(ethylene terephthalate) films subjected to cold drawing and subsequent zone annealing and their mechanical properties are investigated. The effectiveness of zone annealing is compared to that of annealing with fixed ends. Microstructural changes occurring during heat treatment and zone annealing are monitored using wide angle X‐ray scattering, small angle X‐ray scattering, infrared spectroscopy, differential scanning calorimetry, and static mechanical tests. The very high modulus and strength of the zone‐annealed films are directly attributed to the large number of the molecules connecting the crystallites.
The effect of strain rate on the deformation and relaxation behavior of 6/6 nylon at room temperature
Authors: Bordonaro C. M. , Krempl E. 
Published: December 2004

AbstractThe influence of strain rate changes in the range from 10−3 to 10−6 1/s on the zero‐to‐tension loading and unloading behavior as well as short term relaxation properties is investigated using cylindrical specimens of circular cross section. A clip‐on extensometer measures and controls the axial strain in an MTS servohydraulic, computer‐controlled mechanical testing machine. Strains do not exceed twenty percent and all deformation is macroscopically homogeneous. An increase in strain rate causes an increase in stress level. Surprisingly, the total stress drop in a 20 min relaxation period increases with prior strain rate. When the relaxation test is started in the inelastic region with low tangent modulus the total stress drop is nearly independent of the stress and strain at which relaxation commences. Unloading to zero load is not linear but curved and the strain recovery at zero stress is significant. It occurs at an ever decreasing rate and does not exceed three percent in a 12 h period. Like the relaxation behavior the recovery rate increases with prior strain rate. Repeated relaxation periods during zero‐to‐tension cycling can show a stress magnitude decrease during loading but a stress magnitude increase during unloading. The results suggest that a unified model with an overstress dependence of the inelastic rate of deformation could be useful in modeling.
Conformational changes in a polyethylene model under tension and compression
Authors: Pfeffer G. A. , Sumpter B. G. , Noid D. W. 
Published: December 2004

AbstractUsing a realistic model for polyethylene (PE), the molecular dynamics technique is used to simulate atomic motion in a crystal. The calculations reveal conformational disorder above a critical temperature. The rate of isomerization computed from molecular dynamics is compared to transition‐state theory and leads to an activation energy under stress of ∼ 30 kJ/mol, 15 kJ/mol above the single‐bond rotation value. In the unstressed case, the activation energy for the process is less.