bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological and thermal properties of blends of low‐density polyethylene and its ionomers
Authors: Horrion J. , Agarwal P. K. 
Published: April 2004

AbstractMelt rheology and DSC studies of blends of two ionomers′ ethylene‐acrylic acid copolymers are reported, EAA (4.6 mole % AA) and EAA (6.5), as a function of their concentration and counter ion types with their precursor, a low‐density polyethylene. Various isothermal dynamic measurements in the frequency range of 0.01 to 10 rad/sec, from 120 to 200°C, were made; and partial master curves of G′ and G″ were generated. Although the melts appeared to follow the conventional superposition principle, the Cole‐Cole plots were found to be unsatisfactory in describing the miscibility of such blends. The analysis based on the calculations of activation energies and other supporting measurements such as Vicat softening and DSC thermal analysis indicate that such blends are immiscible and perhaps do not have LCST. The blends failed to follow the additivity rule. The Vicat softening measurements indicated variations in the morphology of blends. The DSC studies performed on various 50/50 blends clearly demonstrated phase immiscibility.
Parison formation and inflation behavior of polyamide‐6 during extrusion blow molding
Authors: Wagner Alan H. , Kalyon Dilhan M. 
Published: April 2004

AbstractParison formation and inflation behavior of three polyamide 6 resins during extrusion blow molding were investigated using cinematography, a transparent mold, a pinch‐off mold and a modified blow pin, which allowed the pressure inside the parison to be determined during inflation. The glass fiber filled polyamide exhibited negligible extrudate swell and significant drawdown, whereas polyolefin modified polyamide exhibited appreciable extrudate swell and relatively small drawdown effects. The inflation behavior of the polyolefin modified polyamide was similar to the behavior of conventional blow molding grade polyolefins, whereas the unmodified and glass filled polyamides exhibited different inflation characteristics. Their inflation behavior at different internal pressures was characterized by decreasing and increasing Hencky strain rates with inflation time at high and low internal blow pressures, respectively. The characterized parison formation and inflation behavior of the polyamides emphasize the importance of rigorous blow moldability experiments and the difficulties associated with linking various rheological material functions to the blow moldability of modified polyamides.
Radiation processing of polymer insulators: A method for improving their properties and performance
Authors: Ivanov V. S. , Migunova I. I. , Kalinina N. A. , Aleksandrov G. N. 
Published: April 2004

AbstractPolymer insulators for electric apparatus and high‐voltage overhead lines are promising for replacing porcelain and glass insulators. The possibility of this application is shown by radiation‐chemical technology for the manufacture of rodshaped polymer insulators. An ethylene and vinyl acetate copolymer (EVA) was used as the basis for polymer insulators. The composition also contains aluminium hydroxide as a filler and N,N′‐m‐phenylene dimaleimide as a sensitizer. The investigation of γ‐radiation‐induced crosslinking of this composition made it possible to establish the following optimum conditions of radiation processing of insulators: the absorbed dose of up to 200 kGy at a dose rate of 10 kGy/h in air. By forming a three‐dimensional network in the polymer bulk by radiation, the service properties of the insulators are improved: Shape and heat stability is >200°C and the stability to tracking and erosion >200 h. Differential scanning calorimetry (DSC) and a method of stress relaxation were used in evaluation. In the Saint Petersburg region (Russia), several types of high‐voltage (10–110 kV) polymer insulators are manufactured with the application of such radiation‐chemical technology.
Numerical simulation of blow molding—prediction of parison diameter and thickness distributions in the parison formation process
Authors: Tanoue Shuichi , Kajiwara Toshihisa , Funatsu Kazumori , Terada Kousuke , Yamabe Masashi 
Published: April 2004

AbstractIn our previous study, we calculated the time course of parison length in the parison formation stage, but it could predict only the parison area swell. The next target in our study is to calculate the parison diameter and thickness swell. Annular extrudate swell simulation is necessary for the understanding of various kinds of swelling ratios in blow molding. We have examined three kinds of swells (outer diameter, thickness, and area swells) obtained from simulation results of annular extrudate swell, using the Giesekus model, and have developed a method of predicting parison outer diameter and thickness swell values. The predicted values of parison outer diameters are discussed in comparison with experimental data, and reasonable results are obtained by the proposed method. This prediction method could also be applied to the parison formation process using a parison controller. As a result, it is possible to predict approximately the whole process of parison formation by numerical simulation.
The glass transition temperature of nitrated polystyrene/poly(acrylic acid) blends
Authors: Al‐Najjar Mohammed M. , Hamid S. Halim , Hamad Esam Z. 
Published: April 2004

AbstractLow‐molecular‐weight polystyrene was nitrated to different levels. The nitrated polystyrene was blended with different molecular weights of poly(acrylic acid), PAA. The glass transition temperatures (Tg) for the mixtures were investigated by differential scanning calorimetry. A single Tg was observed for all blends, indicating single‐phase blends. In general, it was found that the Tg increases with molecular weight of PAA. The Tg values of the blends showed a positive deviation from the linear average Tg as a result of strong hydrogen bonding between the segments of the component polymers. The observed Tg values were not adequately represented by simple predictive equations or by single‐parameter fitting equations. However, two‐parameter fitting equations gave a reasonable representation of the data.
Non‐fickian diffusion with reaction in glassy polymers with swelling induced by the penetrant—effects of consecutive and parallel reactions
Authors: Kuipers Norbert J. M. , Beenackers Antonie A. C. M. 
Published: April 2004

AbstractA mathematical model is presented for non‐Fickian diffusion of a penetrant A into a granular glassy polymer containing a reactive group B, resulting in the desired product P. Further, both a consecutive reaction between A and P (producing X) and a parallel reaction between A and C (producing Y) are incorporated, with C initially present in the particle. The swelling of the polymer, induced by the penetrant, is described by power‐law kinetics for the velocity of the swelling front. Kinetics are considered to be first order in each of the two reactants. Concentration profiles in the particle and selectivity to desired product are calculated as function of the swelling behavior of the polymer grain. In case of a consecutive reaction the local concentration of P reaches a maximum value independent of the swelling rate. However, the position of the maximal concentration of P moves towards the center of the grain with a rate depending on the kinetics of swelling. For Case II diffusion this velocity equals the velocity of the advancing front between glassy and rubbery polymer. The selectivity of the desired reaction decreases with decreasing swelling rate. A low swelling rate also results in an inhomogeneous product distribution within the granule. A criterion is derived predicting under what conditions the consecutive reaction can be neglected and a pure product is obtained. The analysis further reveals that both a more homogeneous product and a higher selectivity toward a desired product can be obtained by realizing preswelling of the polymer with an inert swelling agent. For Case II diffusion the concentration profiles of the side product of the parallel reaction, Y, are flat in the rubbery part of the polymer. This is caused by the relatively low swelling rate allowing Y to redistribute in the swollen polymer. If additional C is continuously supplied from the gas phase, then the selectivity decreases continuously with increasing conversion of B.
Bubble dissolution in molten polymers and its role in rotational molding
Authors: Kontopoulou M. , Vlachopoulos J. 
Published: April 2004

AbstractThe presence of bubbles is inherent in the rotational molding process and can often cause poor quality in rotomolded parts. In an effort to gain a fundamental understanding of bubble removal in polymer melts, a model that includes diffusion, surface tension, and viscosity effects has been implemented. This work has been complemented with experiments performed in a heated chamber, which enabled the visualization of the bubble formation and removal process. It was concluded that bubble removal is mainly diffusion controlled and is not influenced significantly by melt viscosity when the latter lies within ranges typical for rotational molding resins. Air concentration in the bulk of the polymer melt and initial bubble size were found to be of great importance. The application of pressure after the polymer has melted accelerates the dissolution rate, owing to an increased driving force for diffusion.
Analysis of an LDPE compact autoclave reactor by two‐cell model with backflow
Authors: Lee Jinsuk , Ham Jae Yong , Rhee Hyun‐Ku , Chang Kil Sang , Kim Jae Youn 
Published: April 2004

AbstractA two‐cell model with backflow and heat exchange is developed to analyze the dynamics of an LDPE compact autoclave reactor. The backflow exists between the two mixing cells and represents the degree of mixing within the reactor. The performance of the reactor and the physical properties of the product polymer such as the number average molecular weight and the polydispersity are investigated under various operating conditions, especially when the initiator feed concentration is varied. Bifurcation diagrams are constructed by taking the initiator feed concentration as the bifuracation parameter and the dynamic feature in the feasible parameter ranges for operation are carefully examined. Indeed, various dynamic characteristics are observed by performing numerical analysis of the nonadiabatic system with the internal cooling device. As the rate of heat transfer increases, various multiplicity patterns and oscillatory behavior such as the limit cycle and the focus are found. The reactor behavior even undergoes period doubling and gradually gives rise to a chaotic behavior in certain ranges of the initiator feed concentration when the coolant temperature becomes low. The existence of chaos is examined by the phase plane plot and Poincaré map. Apparently, the monomer concentration can be substantially increased with proper heat removal and initiator supplement scheme. For this, however, the complex dynamic features must be taken into account in the reactor design.
Processing and properties of high‐temperature creep‐resistant PVC plastisols
Authors: Tai Horng‐Jer 
Published: April 2004

AbstractThe effect of the use of an unsaturated reactive plasticizer trimethylopropane trimethacrylate, TMPTMA, on the structure and the creep behavior of poly(vinyl chloride), PVC, plastisols has been investigated as part of a program to develop a high‐temperature creep‐resistant liner material. The crosslinking reaction was initiated with a peroxide. The effect on the network structure of using a free radical scavenger in the formulation has also been studied. Gel yield and grafted PVC content in the gel increase with increased TMPTMA content in the plastisol. However, the residual unsaturation of TMPTMA decreases with increase of TMPTMA content. Introduction of TMPTMA into the plastisol promotes the creep resistance at high temperatures, and the effectiveness increases when there are PVC molecules grafted onto TMPTMA networks.
Effect of molecular structure on the rotational molding characteristics of ultra‐low‐density ethylene‐α‐olefin copolymers
Authors: Wang W. Q. , Kontopoulou M. 
Published: April 2004

AbstractThe rotational molding characteristics of two ultra‐low‐density ethylene‐α‐olefin copolymers with elastomeric properties (polyolefin plastomers), made by metallocene catalysts, were investigated with the purpose of examining the effect of molecular structure on their processability. Particle coalescence and densification experiments revealed that higher comonomer content resulted in slower rates of coalescence and densification, thus affecting bubble content. Based on detailed material characterization, slower densification was attributed to the presence of broad melting endotherms, higher viscosity immediately after the melting transition, and higher melt elasticity. Investigation of the effect of particulate form revealed that use of powders instead of micropellets resulted in the formation of fewer bubbles on the outer surface, because of the broader particle size distribution, leading to improved appearance, better mechanical properties, and reduced overall processing time. Rotomolded parts displayed excellent impact properties and a high degree of flexibility. Polym. Eng. Sci. 44:496–508, 2004. © 2004 Society of Plastics Engineers.
Microstructural modifications in uniaxially hot‐drawn polycyclohexylene terephthalate films
Authors: Kattan M. , Dargent E. , Grenet J. 
Published: April 2004

AbstractSemi‐aromatic thermoplastic polycyclohexylene terephthalate (PCT), initially wholly amorphous, was uniaxially drawn to study microstructural modifications as the appearance of the strain‐induced (S.I.) crystalline phase. Polyethylene terephthalate (PET) and poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG) are considered as reference materials in this work. In polycyclohexylene terephthalate (PCT) the presence of a saturated ring (which is not quite as rigid as the aromatic ring) modifies the characteristics of both thermal and S.I. crystallization. Samples with various draw ratios (drawing of PCT films is performed at T > Tg) were analyzed by Modulated Differential Scanning Calorimetry, wide angle X‐ray scattering, and birefringence measurements. In drawn PCT films, an S.I. crystalline phase appears continuously with the draw ratio and reaches 35%. For this polymer and for the highest draw ratio, the “true” amorphous fraction practically disappears. The material is composed only of the S.I. crystalline phase and the “rigid” amorphous phase. Polym. Eng. Sci. 44:509–517, 2004. © 2004 Society of Plastics Engineers.
Uniaxial tensile behavior and thermoforming characteristics of high barrier EVOH‐based blends of interest in food packaging
Authors: Giménez E. , Lagarón J. M. , Maspoch Ma. L. , Cabedo L. , Saura J. J. 
Published: April 2004

AbstractThe uniaxial tensile characteristics of blends of an ethylene‐vinyl alcohol copolymer (EVOH‐32 mol% ethylene) with an amorphous PA and/or a nylon‐containing ionomer, used as barrier layer in multilayer food packaging structures, was assessed in this paper. The stress‐strain behavior of these materials at elevated temperatures and at different strain rates was examined. The stress‐strain curves obtained were used to understand the influence of temperature and strain rate on the uniaxial deformation process of the materials, these being of general importance during typical processing steps including thermoforming. A male mold for deep‐draw was used to assess the thermoforming (biaxial deformation in nature) behavior of extruded sheets at 100, 120, 140 and 150°C, and the results were broadly found to be in agreement with results from simple uniaxial tensile tests. From the preliminary thermoforming results, it was found that EVOH/aPA extruded blends did not improve the poor formability of EVOH alone. In contrast, significant improvement in thermoformability was achieved by blending EVOH with a compatibilized ionomer. Optimum forming capacity was achieved in a ternary blend by addition of a compatibilized ionomer to an EVOH/aPA blend in the range of 140°C–150°C. The ternary blend showed a lower reduction of thickness in the sidewalls, as well as a higher dimensional uniformity in the thermoformed part. Polym. Eng. Sci. 44:598–608, 2004. © 2004 Society of Plastics Engineers.
Molecular parameters governing the yield response of epoxy‐based glassy networks
Authors: Lesser Alan J. , Calzia Kevin J. 
Published: April 2004

AbstractThis contribution considers to what extent two molecular parameters, the glass transition temperature and the cohesive energy density, relate to the yield behavior of epoxy‐based glassy thermosets. Eight different formulations consisting of four aliphatic and four aromatic resins with varying molecular weights between crosslinks were investigated over a broad range of test temperatures. Additionally, one aromatic formulation is studied over a range of stress states and test temperatures. The results indicate that both the glass transition and cohesive energy density are governing parameters that relate to the yield response of these systems. A model is proposed to incorporate these parameters and to predict the yield response as a function of strain rate, temperature, and stress state. The functional form of the results also indicate that the activation energy density (i.e., the activation energy divided by the activation volume) may be the material characteristic that relates to yield of these systems rather than each term individually. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2050–2056, 2004
Gas trapping in normal infants and in infants with cystic fibrosis
Authors: Castile Robert G. , Iram Durdana , McCoy Karen S. 
Published: April 2004

AbstractTwo different methods for estimating trapped gas volume have been described in the literature. The purpose of this study was to use both of these methods to estimate and compare trapped gas volumes in normal infants and infants with cystic fibrosis (CF). Thirty normal infants and 29 infants with CF, ages 1 month to 3 years, were studied. Pulmonary function tests, including raised volume forced expiratory flows, plethysmographic functional residual capacity (FRCpleth), and fractional lung volumes, were measured. Then functional residual capacity was measured by nitrogen washout (FRCnitrogen). Following nitrogen washout, lungs were then inflated three times to 30 cm H2O, using 100% oxygen. This process was repeated until no further nitrogen could be washed from the lungs. The volume of trapped gas (tg) was calculated from the total additional amounts of nitrogen expired following lung inflations. The difference between FRCpleth and FRCnitrogen provided a second estimate of trapped gas volume (delta V). Mean tg and delta V values for normal infants were 2.5 ± 3.5 ml and 15.6 ± 30.4 ml, respectively. Mean tg and delta V values for infants with CF were 5.8 ± 7.7 ml and 33.2 ± 43.8 ml, respectively. Both tg and delta V did not differ significantly between normal infants and infants with CF. Measured following raised volume forced expiratory maneuvers, delta V and tg do not distinguish infants with CF from normal infants as well as do other currently available tests of infant lung function. Pediatr Pulmonol. 2004; 37:461–469. © 2004 Wiely‐Liss, Inc.
Facemasks and facial deposition of aerosols
Authors: Sangwan Sanjay , Gurses Burak K. , Smaldone Gerald C. 
Published: April 2004

AbstractPassage of aerosol around or through a facemask can result in deposition on the face and in the eyes. The present study quantified facial and eye deposition in a model simulating drug delivery to a young child. Aerosol delivery and facial deposition of radiolabeled saline test aerosols were studied in vitro with filters and a gamma camera. A child's face facsimile, attached to a piston pump, was used to simulate the patient receiving aerosol therapy. A filter placed in the oropharynx of the face facsimile measured aerosol delivery (inhaled mass). Seven commercially available facemasks in combination with three jet nebulizers were studied for aerosol delivery to the “patient” as well as for deposition on the face and in the eyes. Inhaled mass varied from 2.24–5.96% of nebulizer charge (drug placed in the nebulizer). Facial deposition varied from 0.44–2.34% of nebulizer charge, with eye deposition at 0.09–1.78%. All facemasks leaked aerosol, with significant facial and eye deposition approaching in magnitude delivery to the lung. Factors affecting facial and eye deposition include the interactive design characteristics of the facemask and nebulizer, as well as the aerodynamic properties of the aerosol. Pediatr Pulmonol. 2004; 37:447–452. © 2004 Wiely‐Liss, Inc.
Disease severity in siblings with cystic fibrosis
Authors: Katz Sherri L. , Strug Lisa J. , Coates Allan L. , Corey Mary 
Published: April 2004

AbstractSince cross‐infection occurs between cystic fibrosis (CF) siblings, we hypothesized that subsequent siblings may acquire respiratory pathogens at an earlier age and have a more severe course of pulmonary disease. We studied a retrospective cohort of 31 sibling pairs from the CF database at the Hospital for Sick Children. Kaplan‐Meier curves and modified log‐rank tests were used to test sibling differences in age of acquisition of Pseudomonas aeruginosa (PA), Staphylococcus aureus (SA), or any positive culture. Differences in disease severity outcomes were explored. Older siblings were more likely to have both SA and any CF pathogen first isolated from respiratory culture at an older age than younger siblings (P = 0.0050 and P = 0.0008, respectively, by modified log‐rank tests). However, more of the older siblings were positive on first culture at time of diagnosis, introducing an age‐of‐diagnosis bias. Hospitalization rates, courses of oral antibiotics, FEV1 % predicted, and weight and height measurements were not better in the older children. No differences in clinical parameters were found between older and younger siblings. The apparent finding of younger age at first isolation of pathogens from respiratory cultures in younger siblings is likely because many older siblings were already infected with these organisms at time of diagnosis. Pediatr Pulmonol. 2004; 37:407–412. © 2004 Wiely‐Liss, Inc.
Quantitative cytokine gene expression in CF airway
Authors: Muhlebach Marianne S. , Reed William , Noah Terry L. 
Published: April 2004

AbstractBronchoalveolar lavage fluid (BALF) in cystic fibrosis (CF) shows increased inflammation, which could be due to abnormal cytokine regulation. Bronchial epithelial cells and migratory inflammatory cells produce these cytokines, but few quantitative in vivo data are available comparing young CF patients with controls. We hypothesized that IL‐8 mRNA abundance was higher in young CF vs. non‐CF disease control patients in lung epithelium and inflammatory cells. Bronchial epithelial cells (BEC) were obtained by brush biopsy, and airway inflammatory cells (BALFC) by bronchoalveolar lavage, in 17 CF and 21 non‐CF patients <5 years old undergoing clinically indicated bronchoscopy. Cellular mRNA expression was quantified by real‐time PCR and normalized to glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH). Abundance of IL‐8/GAPDH in BEC was significantly higher in CF (14.8 ± 3.3) than non‐CF (4.2 ± 0.6) samples, and this difference was also significant when patients were stratified according to infection. In BALFC, the difference in IL‐8 expression did not reach statistical significance: CF (17.1 ± 6.5) vs. non‐CF (6.8 ± 1.9), but BALF cell number/ml was significantly higher in CF. IL‐10 mRNA was very low in all samples, without showing a decrease in CF vs. non‐CF patients. We conclude that early in the disease, IL‐8 mRNA expression in BEC is increased in CF in vivo. Although IL‐8 mRNA in migratory cells was not significantly higher in CF, these cells may still contribute to elevated IL‐8 in airway secretions, secondary to increased cell density in BALF. Pediatr Pulmonol. 2004; 37:393–399. © 2004 Wiely‐Liss, Inc.