bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rate‐effect on fracture behavior of core‐shell‐rubber (CSR)‐modified epoxies
Authors: Xiao Keqin , Ye Lin 
Published: April 2004

AbstractA bisphenol A diglycidylether (DGEBA) epoxy was modified with up to 20 wt% of a core‐shell rubber (CSR), and mechanical properties were investigated at different crosshead rates (from 0.5 mm/min to 500 mm/min). The yield strength and Young's modulus decreased almost linearly with increasing rubber content or decreasing crosshead rate. Fracture toughness, KIC, was significantly improved by the addition of CSR to the pure epoxy. The optimum rubber content was between 15% and 20% at the lowest crosshead rate (i.e. 0.5 mm/min) and shifted to higher rubber content at higher crosshead rates. KIC decreased slightly as the crosshead rate was increased from 0.5 mm/min and dropped significantly when the crosshead rate approached 500 mm/min. Rubber cavitation‐induced local plastic deformation was identified as the principal energy absorption mechanism, and it was independent of rubber content and crosshead rate. The variation of KIC with rubber content and crosshead rate correlated well with the length of the stress‐whitened zone.
Ultrasonic in‐line monitoring of polymer extrusion
Authors: Françla D. R. , Jen C.‐K. , Nguyen K. T. , Gendron R. 
Published: April 2004

AbstractIn‐line ultrasonic monitoring of polymer co‐extrusion and twin‐screw extrusion are presented. Co‐extrusion of high density polyethylene (HDPE) and a thermoplastic elastomer based on polypropylene‐EPDM (ethylene‐propylene‐diene monomer) has been investigated by ultrasonic sensors consisting of piezoelectric transducers and clad buffer rods. One extremity of the rod (probing end) was installed flush with the die surface so as not to disturb the material flow. The other end was air cooled in order to protect the transducer from excessive heating. This approach has been demonstrated to be quite convenient for monitoring and controlling industrial material processes: first, it can work at temperatures up to 1000°C; second, the clad buffer rod probing end can be machined to the same shape as those of commercial temperature and pressure sensors commonly used in the extrusion process. Therefore, no modifications are required for the installation in the original equipment. The information obtained includes the position of the interface between polymers and the stability of the process. The same ultrasonic probe has also been installed on a barrel of a twin‐screw extruder. This study was performed using polyethylene and polystyrene. It has been verified that the ultrasonic sensor can be successfully operated along the extruder screw and that the ultrasound can give access to the material properties while the polymer is being processed. This means that the technique can be exploited to monitor and control in situ the characteristics of the polymer being transformed in operations typically performed on twinscrew extruders, such as compounding, visbreaking or reactive extrusion.
Injection molding of poly(ethylene terephthalate): Differential scanning calorimetry and confocal micro‐raman spectroscopy investigations of the skin‐core morphology
Authors: Fernández M. R. , Merino J. C. , Pastor J. M. 
Published: April 2004

AbstractThe skin‐core structure of injection‐molded plates of poly(ethylene terephthalate) (PET) has been investigated using Confocal Micro‐Raman Spectroscopy (CMRS) and Differential Scanning Calorimetry (DSC). CMRS has proved to be a useful tool for finding out about quantitative conformational changes in polymeric materials. In order to obtain a complete picture of isomer distributions in the injection molded industrial PET samples, spectroscopic measurements were correlated with DSC measurements. The spectroscopic results reveal two different structural zones related to the fabrication process: a skin layer and the core. The correlation between the apparent degree of crystallinity obtained by DSC and the percentage of the trans isomer obtained by CMRS has allowed the latter parameter to be separated into crystalline and amorphous trans isomer and to follow its change along the injection molded plate.
Film casting of polyethylene terephthalate: Experiments and model comparisons
Authors: Acierno D. , Di Maio L. , Ammirati C. C. 
Published: April 2004

AbstractCast film extrusions were carried out on polyethylene terephthalate (PET), on a laboratory line. The thermal and the geometrical behavior of the film, in the region from die to chill roll, was studied in different working conditions. The experimental evaluations were performed with an Infrared Thermography (I.R.T.) apparatus. Simplified modeling, describing the non‐isothermal behavior of the web, was used to predict temperature, width and thickness of the film in machine direction (MD) as a function of the distance from the die. The above‐calculated profiles were compared to those obtained by experimental thermography maps. Measured temperatures resulted different between edge and center of film, i.e. transverse direction (TD) temperature profiles were highlighted. On the contrary, model temperatures are assumed varying only along the machine direction (MD) of web. Thus, from the comparison between experimental and theoretical results, an acceptable agreement was found only in some cases.
Model filled rubber. VI: Dynamic property dependence on filler particle size of rubber compounds during curing
Authors: Cai Jianfen J. , Salovey Ronald 
Published: April 2004

AbstractThe effect of particle size on curing kinetics and dynamic properties was examined with model filled rubber compounds containing monodisperse size crosslinked polystyrene (PS) particles synthesized from emulsifier‐free emulsion polymerization. In the process of curing, the magnitude of the dynamic moduli increased and the gelation time (GP) decreased as PS particle diameter decreased from 1.25 to 0.315 μm. GP was 5.5 hours for the pure matrix, 13 minutes for the composite containing 0.315 μ.m particles, 1.4 hours for 0.688 μm particles and more than 2 hours for 1.25 μm particles. We propose that in PS particle filled systems, the ability to form clusters was due to interparticle dispersive interactions which increase with decreasing particle size. The particle clusters function as physical crosslinks, so that the overall crosslink density was significantly enhanced. Rheologically, the dynamic moduli and gelation rate were increased with decreasing particle diameter.
Prediction of the gas permeability of heterogeneous polymer blends
Authors: Kolařík Jan , Fambri Luca , Pegoretti Alessandro , Penati Amabile 
Published: April 2004

AbstractA recently introduced predictive scheme is used to calculate the permeability of various types of heterogeneous polymer blends, which are characterized by the ratio of the permeability of constituents in the range 10–10,000. The scheme combines a two‐parameter equivalent box model and the data on the continuity of constituting phases acquired by modifying equations proposed by the percolation theory; it takes into account the permeability of components and the interval of phase duality (co‐continuity) delimited by the critical volume fractions of components v1cr and v2cr. The scheme can be used in two ways: (i) permeability of blends predicted by using the “theoretical” value of parameters v1cr = v2cr = 0.16 should be regarded as a first approximation which may not well approximate experimental data due to the fact that real v1cr and v2cr are affected by relative viscosities of the components, interfacial energy, conditions of blend mixing, phase structure coarsening, etc.; (ii) conversely, by fitting experimental data, it is possible to determine v1cr and v2cr for the studied system; thus the scheme can be alternatively viewed as an efficient tool for phase structure analysis of polymer blends.
Deformation rate dependence of work of fracture parameters in polybutylene terephthalate (PBT)
Authors: Hashemi S. 
Published: April 2004

AbstractEssential work of fracture (EWF) analysis was used to study the effect of loading rate (v = 2, 5, 25 and 50 mm/min) on fracture toughness of PBT film of thicknesses 0.175, 0.275, 0.375 and 0.5 mm. Using single edge notched tension (SENT) specimens, it was found that the specific essential work of fracture, we, increases slightly with increasing loading rate but Within the specified range of loading rate, it showed no significant variation with respect to thickness. The specific non‐essential work of fracture, βwp, decreased with increasing rate and increasing thickness.
Barrier and mechanical properties of pulp fiber/polymer laminates and blends
Authors: Krook M. , Hedenqvist M. S. , Albertsson A.‐C. , Hellman A. , Iversen T. , Gedde U. W. 
Published: April 2004

AbstractPaperboard laminates coated with two grades of poly(ε‐caprolactone) (PCL), poly(hydroxy butyrate‐co‐valerate) (PHBV) or a liquid crystalline copolyester (LCP) were prepared by compression molding, and the influence of the processing conditions and polymer content of the laminate on the laminate properties was studied. Ligno‐cellulose fiber/polymer blends were prepared from wet pulps and PCL and PHBV. The morphology, water vapor transmission rates, creasability, curl and twist and mechanical properties of the laminates and blends were studied. LCP and slowly cooled high molar mass PCL laminated paperboards showed the best creasing properties and the paperboards that were penetrated by the polymer showed the smallest degree of curl and twist. Extensive penetration occurred during compression molding of the paperboard with the low molar mass PCL at all temperatures and with PHBV and LCP at the higher molding temperatures. The water vapor transmission rates ranged from 1 to 300 times that of polyethylene depending on the polymer used and on the thermal history. In the case of blends, competitive properties were obtained only in those with a high polymer content. The laminate stiffness decreased and the strength increased in two polymer concentration regions, at ∼20 wt% due to fiber‐fiber separation and at ∼60 wt% due to phase inversion.
Modification of PET in high‐speed melt spinning by blending with PEN
Authors: Rwei Syang‐Peng 
Published: April 2004

AbstractBlends of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) were melt spun using a high‐speed winding process in a single‐screw extruder combined with a spinning setup. The filaments had a single Tm and Tg, which indicates excellent compatibility in both the amorphous and crystalline phases. Birefringence and wide angle X‐ray measurements indicated that compounding PEN into PET suppresses stress‐induced orientation and decreases the stressinduced crystallization in the filaments. Adding PEN to PET relaxes the formation of skin‐core structures for as‐spun fibers and reduces the occurrence of broken filaments. Although the addition of PEN reduced crystallinity, it did not affect the tenacity and the shrinkage of the compounded filaments. The elongation of the fibers could be reduced by 30% to 40%, eliminating the need for a further drawing. These results are attributed to PEN's rigid backbone. Adding PEN to PET improves PETs spinnability during high‐speed spinning.
Dielectric rheological measurements of molten polymers
Authors: McBrearty Michael , Perusich Stephen 
Published: April 2004

AbstractRheological characterization of polymers above their melting points is performed with dielectric spectroscopy. A new in‐line interdigitated dielectric sensor as well as a commercial off‐line sensor were used to make the measurements. The dielectric dissipation or loss factor of a molten polymer was found to be directly proportional to independently measured rheological properties of the polymer. Time‐temperature superposition was used to translate dielectric and rheological curves to master curves where the curves are comparable in form, but the activation energy of a dielectrically‐induced relaxation was found to be lower than a rheological translational motion. The more localized and homogeneous effects imparted to the polymer during the dielectric measurement may cause the polymer to undergo a viscoelastic transition at a lower energy than the flow‐induced transition in rheological measurements. The dielectric methods detailed herein provide a new noninvasive technique to measure the viscoelastic properties of molten polymers.
Dielectric spectroscopy for polymer melt composition measurements
Authors: Perusich Stephen , McBrearty Michael 
Published: April 2004

AbstractLaboratory and in‐line dielectric spectroscopy studies of molten polymers revealed the ability to make composition measurements of the comonomer concentration along the polymer chains. The dielectric permittivity or capacitance was found to be proportional to the polymer sidechain composition. The length of the polar sidegroup dictated the optimum measurement frequency; i.e., a short sidechain, such as the C‐Cl bond in chlorosulfonated polyethylene, required a high measurement frequency (short relaxation time) due to the rapid mobility of the sidechain, whereas a longer sidechain, such as the vinyl ether sidegroup in Nafion®, required a much lower frequency (longer relaxation time) to orient the sidechain to a measurable extent. For in‐line process studies, a new cylindrical, interdigitated dielectric sensor and associated electronics were developed to make measurements on molten polymers at the exit of an extruder up to 400°C and 3000 lbs/in2. In‐line studies of molten polymers revealed a direct relationship between the dielectric signal and the polymer comonomer composition. The sensor represents a non‐invasive, real‐time process composition measurement and can be integrated to provide closed‐loop process control.
Mean residence time analysis for twin screw extruders
Authors: Gao Jun , Walsh Gregory C. , Bigio David , Briber Robert M. , Wetzel Mark D. 
Published: April 2004

AbstractThis paper presents and experimentally validates a physically motivated model for predicting the mean residence time in twin screw extruders. Accurate estimation of the mean residence time and the propagation delay through a plasticating extruder is critical for implementing feedback control schemes employing sensors mounted along the extruder. Experiments were carried out on a 30 mm Krupp Werner and Pfleiderer co‐rotating twin screw extruder equipped with reflectance optical probes over the melting section and mixing section and at the die. The residence time distributions for twelve operating conditions and two screw geometries are compared. The mean residence times predicted by our model are in good agreement with the experimentally measured mean residence times.
Structural changes of gel drawn, ultra‐high molecular weight polyethylene fibers with kerosene as a solvent
Authors: Xiao C. F. , Zhang Y. F. , An S. L. , Jia G. X. 
Published: April 2004

AbstractFibers of ultra‐high molecular weight polyethylene (UHMW‐PE) were prepared with the gel fiber drawing method. The solvent and extraction solvent used were a general kerosene and gasoline, respectively. The structural changes in the fibers during the drawing process were examined by wide‐angle X‐ray diffraction (WAXD), polarizing optical microscopy (POM), and a density gradient column. During the drawing process, a folded chain structure transformed into an extended‐chain in the fiber, the density of the fibers increased, and the dimensions of the orthorhombic crystallite size tended towards a narrow distribution simultaneously with the increasing draw ratio. The orthorhombic unit cell dimensions for the fiber with a draw ratio of 40 were a = 0.732 nm, b = 0.491 nm, and c = 0.254 nm. In the fiber with a draw ratio of about 40, kink bands were observed. It is suggested they correspond with the local crystalline slip due to the effect of winding tension. Also, the smaller the winding roller diameter, the more clearly they can be observed. In this work, the effect of the existence of kink bands on the structures of orientation and crystallinity of fiber bulk was not observed.
Effect of incorporating ethylene‐ethylacrylate copolymer on the positive temperature coefficient characteristics of carbon black filled HDPE systems
Authors: Lee Gun Joo , Suh Kyung Do , Im Seung Soon 
Published: April 2004

AbstractIn order to study the effect of introducing ethylene‐ethylacrylate copolymer (EEA) in carbon black‐HDPE composite systems, two HDPE‐EEA composites prepared by pre‐blending and masterbatch‐blending processes were compared with HDPE and EEA composites in terms of positive temperature coefficient (PTC) characteristics and percolation threshold. The percolation threshold of masterbatch‐blended composites occurred at the lowest carbon black concentration among four kinds of composites. The conduction path in the masterbatch‐blended composite is effectively formed as a result of the localization of carbon black distribution predominantly in the EEA phase, resulting in an increase of conductivity. Ipeak values, the resistivity ratio of the peak to 25°C, of two blend composites were lower than those of HDPE composites. The I85 values, the resistivity ratio of 85°C to 25°C, of masterbatch‐blended composites were higher than those of pre‐blended as well as HDPE composites. It is evident that since most carbon black is dispersed in the EEA phase of the masterbatch‐blended composites, the conduction networks are mainly broken by the crystal melting of EEA before the temperature reaches the crystal melting temperature of HDPE.
Experimental investigation of the energy balance for the metering zone of a twin screw extruder
Authors: Tenge Stephan , Mewes Dieter 
Published: April 2004

AbstractThe object of this study is to investigate experimentally the mechanical power transported from the screws to the polymer melt, the heat dissipated in the polymer melt, and the heat transferred to the barrel of the metering zone of a co‐rotating twin screw extruder. For the experimental investigations, different screw elements, mixing elements, and kneading discs are used. The experimental results for the dissipation show good agreement with known calculation models. For the calculation of the heat transfer, a new equation is used to calculate the mean temperature difference under consideration of the dissipation. The Nusselt‐number can be calculated in good agreement with the experimental results as a function of the Brinkmann‐number.
Effects of gauge length and strain rate on fracture toughness of polyethylene terephthalate glycol (PETG) film using the essential work of fracture analysis
Authors: Ching Emma C. Y. , Li Robert K. Y. , Mai Yiu‐Wing 
Published: April 2004

AbstractEssential Work of Fracture (EWF) analysis was used to study the fracture toughness of a PETG film. In the study of the gauge length (Z) effect on the specific essential work (we) using Z = 50, 100, 150, 200 and 250 mm, it is observed thatweis Independent of gauge length, except that a slightly lowerwevalue was measured for Z = 50 mm. Interestingly, for specimens with long gauge lengths (Z ≥ 150 mm in this study), brittle fracture occurred. The minimum ligament length at which ductile/brittle transition took place was observed to decrease with increasing gauge length. There is a small strain rate effect onwewith loading rates less than 1 mm/min. But with higher loading rates,weshoweld no strain rate sensitivity.
Characterization of two precursor polyblends: Polyhydroxyamide and poly(amic acid)
Authors: Chang Jin‐Hae , Farris Richard J. 
Published: April 2004

AbstractBlends of two precursor polymers, polyhydroxy amide (PHA) and poly(amic acid) (PAA), were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The presence of PHA enhanced thermal and mechanical properties of the polyblends. All of the polyblended films showed large endothermic peaks that decreased monotonically with increasing heat treatment temperature. The cyclization onset temperature (T1), initial decomposition temperature (T2), and weight residue at 900°C of the polyblends were shown to be in the ranges of 144–146°C, 532–540°C, and 44–45%, respectively. Also, the thermal stabilities were enhanced consistently with increasing annealing temperature from 25 to 250°C. The ultimate strength and initial modulus of the polyblends increased from 84 to 136 MPa and from 2.93 to 5.34 GPa, respectively, with increasing PHA content. Similar to the trend of thermal stability, increasing the annealing temperature of the polyblends increased the tensile properties of the films. The observed tensile properties are discussed in terms of the morphology of the fractured films as studied by scanning electron microscopy (SEM). The degree of crystallinity of the polyblends was characterized as a function of heat treatment temperatures by wide angle X‐ray diffractometry (WAXD).
Surface structure of isotactic polypropylene by X‐ray diffraction
Authors: Nishino Takashi , Matsumoto Takayuki , Nakamae Katsuhiko 
Published: April 2004

AbstractWith the glazing angle incidence of an X‐ray beam, the surface structure of compression molded isotactic polypropylene film was investigated by X‐ray diffraction. A comparison of the crystallinities between the surface and the bulk was made for films annealed in air at different temperatures and times. The crystallinity was lower for the surface compared with the bulk irrespective of annealing conditions. A drastic change in crystallinity occurred up to depths of several micrometers from the surface, and crystallinity decreased near the surface. The apparent crystallite sizes were smaller for the surface. This showed that crystal growth was restricted near the surface because of localized defects (including chain ends), and high chain mobility. Annealing at higher temperatures induced surface oxidation, which also decreased the surface crystallinity. The residual stress near the surface, attributable to quenching from the melt, was also detected by this method.
3‐D numerical simulations of nonisothermal flow in co‐rotating twin screw extruders
Authors: Ishikawa Takeshi , Kihara Shin‐Ichi , Funatsu Kazumori 
Published: April 2004

AbstractThree‐dimensional nonisothermal flow simulations in the kneading disc regions of co‐rotating twin screw extruders were performed using a finite element method. The standard Galerkin method and penalty function scheme were applied to the flow field. The streamline‐upwind/Petrov‐Galerkin scheme was used in the temperature field to reduce numerical oscillation. The simulations were carried out under the operational conditions of The Japan Steel Works TEX30 machine for various rotational speeds. The configuration was ten 2‐lobe kneading discs with a 90° stagger angle. Experimental observations were also performed to validate the numerical simulations under the same operational conditions. The pressure in front of the tip in the rotation direction was higher than behind the tip, and the region behind the tip sometimes had a negative value. Since variation of the pressure gradient in the axial direction causes forward and backward flows in the disc gap regions, the disc gap regions play an important role for mixing. The temperature becomes higher with increasing rotation speed due to high viscous dissipation. A high temperature was observed on the disc surface, in the disc gap, and in the intermeshing regions. The numerical results of pressure profiles with the rotation and the temperature in the axial direction were in good agreement with the experimental observations.