bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of recycling on LDPE foamability: Elongational rheology
Authors: Kabamba Eddy Twite , Rodrigue Denis 
Published: December 2007

AbstractThe purpose of this work was to investigate changes in the elongational rheology of low density polyethylene (LDPE) when recycled. Both foamed and unfoamed LDPE were submitted up to 10 generations in a closed loop using constant extrusion conditions and azodicarbonamide as a chemical blowing agent. For both foamed and unfoamed polymers, decreasing elongational properties in terms of strain hardening was observed, indicating progressive loss of foamability with the number of time the polymer is recycled. It was also found that the elongational properties of the foamed polymer decreased more rapidly than its unfoamed counterpart. It is believed that higher mechanical degradation of polymer may be the result of higher deformation rates (biaxial) associated with foaming and the accumulation of blowing agent residues limiting polymer chain mobility and entanglement. POLYM. ENG. SCI., 48:11–18, 2008. © 2007 Society of Plastics Engineers
Local residence time, residence revolution, and residence volume distributions in twin‐screw extruders
Authors: Zhang Xian‐Ming , Feng Lian‐Fang , Hoppe Sandrine , Hu Guo‐Hua 
Published: December 2007

AbstractThis work was aimed at studying the overall, partial, and local residence time distributions (RTD); overall, partial and local residence revolution distributions (RRD) and overall, partial and local residence volume distributions (RVD) in a co‐rotating twin screw extruder, on the one hand; and establishing the relationships among them, on the other hand. Emphasis was placed on the effects of the type and geometry of mixing elements (a gear block and various types of kneading elements differing in staggering angle) and process parameters on the RTD, RRD and RVD. The overall and partial RTD were directly measured in‐line during the extrusion process and the local ones were calculated by deconvolution based on a statistical theory. The local RTD allowed comparing the mixing performance of mixing elements. Also it was confirmed both experimentally and theoretically that specific throughput, defined as a ratio of throughput (Q) over screw speed (N), controlled all the above three types of residence distributions, be they local, partial or overall. The RRD and RVD do not provide more information on an extrusion process than the corresponding RTD. Rather they are different ways of representing the same phenomena. POLYM. ENG. SCI., 48:19–28, 2008. © 2007 Society of Plastics Engineers
Temperature, conversion, and phase separation profiles during mold cure of a modified vinyl‐ester resin
Authors: Schroeder Walter F. , Auad María L. , Soulé Ezequiel R. 
Published: December 2007

AbstractIn this work, morphological differences over the thickness of modified vinyl‐ester (VE) samples are studied. A thermodynamic analysis based in the Flory–Rehner theory is proposed to evaluate the spinodal decomposition temperature evolution during the reaction. This model takes into account changes in (styrene‐co‐VE) copolymer composition and binary interaction parameters with conversion. Then, from the energy and mass balance equations, temperature and conversion profiles over the thickness as a function of reaction time are calculated. Combining these profiles with the proposed thermodynamic model, spinodal decomposition conversion graphs are constructed. To verify model predictions, a synthesized VE resin was modified with 7.5 wt% of poly(butadiene‐co‐acrylonitrile) vinyl terminated (VTBN) elastomer and then cured in molds of 3, 7, 12, and 20 mm thickness at 80°C. Fracture surfaces were observed by scanning electron microscopy showing morphological differences over thickness, which can be explained from the results obtained from the simulation. POLYM. ENG. SCI., 48:52–61, 2008. © 2007 Society of Plastics Engineers
Reinforcement of polydimethylsiloxane through formation of inorganic–organic hybrid network
Authors: Jia Liya , Du Zhongjie , Zhang Chen , Li Congju , Li Hangquan 
Published: December 2007

AbstractCrude silica was modified with silsisquioxane (SSO), which was originated from vinyltriethoxysilane, leading to modified silica. The modified silica with vinyl groups was employed to reinforce polydimethylsiloxane (PDMS) through participating in the hydrosilation reaction. Inorganic–organic hybrid network was formed to obtain higher mechanical properties. Fourier transformation infrared spectroscopy (FTIR) confirmed that the vinyl groups were bonded to the surface of silica. Transmission electron microscopy (TEM) showed that the diameter of the modified silica increased and the shape became irregular. The effects of the amount of SSO, the loading of modified silica, and the vinyl/hydrogen mole ratio on the mechanical properties of the cured PDMS system were investigated. It was found that 40 parts of SSO could result in a sufficient surface modification of the silica. The tensile strength and the modulus (reflected by the stress at 100% elongation) kept increasing with increasing loading of silica. When the vinyl/hydrogen mole ratio was 1:1, the most effective reinforcement was obtained. POLYM. ENG. SCI., 48:74–79, 2008. © 2007 Society of Plastics Engineers
Prediction of the influence of flow‐enhanced crystallization on the dynamics of fiber spinning
Authors: Kohler William H. , McHugh Anthony J. 
Published: December 2007

AbstractA linearized sensitivity and stability analysis of fiber spinning of semi‐crystalline polymers has been carried out for both low‐ and high‐speed spinning conditions to investigate the relative roles of flow‐enhanced crystallization (FEC) and thermal‐induced crystallization (TIC) on the process dynamics. The analysis is based on an earlier‐developed two‐phase constitutive model for FEC that utilizes either the Giesekus or the Extended Pom‐Pom constitutive equations for the amorphous phase and a rigid‐rod model for the semi‐crystalline phase, combined with the transport balances for the 1‐D fiber spinning model. Model parameters from fits of the steady‐state low‐ and high‐speed spinning of Nylon and L‐polylactic acid are used to illustrate the effects of changes in various process variables (principally air cooling rate and temperature) on the system sensitivity. Results show that higher crystallization, whether from TIC or FEC, generally equates to lower spinline sensitivity. However, factors such as high‐speed necking induced by FEC, viscoelastic stresses, and thermal transport properties are also shown to impact trends in the sensitivity. Because of the specific nature of the FEC model and lack of a general theory for determining model parameters from first principles, calculations and conclusions are necessarily system specific. POLYM. ENG. SCI., 48:88–96, 2008. © 2007 Society of Plastics Engineers
Prediction of molecular weight scale and molecular weight distribution of cellulose using a rheology‐based method
Authors: Zhang Huiru , Tong Mingwei , Li Rongxian 
Published: December 2007

AbstractPrediction of MW scale and MWD of cellulose by means of a rheology‐based method is developed. In this method, for the cellulose/NMMO·H2O solution, it is assumed that the cellulose MW values calculated by the Rouse terminal relaxation time can be regarded as the peak MW on the MWD curves of cellulose. Consequently, it is realized that the reciprocal of the frequency is converted to the MW scale, obtaining MWD scale curves of cellulose. Meanwhile, the obtained results are compared with those measured by the GPC method. The comparison shows that the calculated peak MW values are approximately equal, the calculated PDI values and MWD curves have the same trends. Consequently, it may be feasible to compare the MW scale and MWD of cellulose by using the rheology‐based method. In addition, the rheology‐based method is simple and fast. Therefore, it is a useful and easy way to analyze the MW scale and MWD of cellulose in the fiber industry. POLYM. ENG. SCI., 48:102–106, 2008. © 2007 Society of Plastics Engineers
Thermal behaviors of a novel UV cured flame retardant coatings containing phosphorus, nitrogen and silicon
Authors: Chen Xilei , Hu Yuan , Song Lei 
Published: December 2007

AbstractPhosphorus‐containing trimethoxysilane (DGTH) was blended with Star polyurethane acrylate (SPUA) in different ratios to obtain a series of UV curable intumescent flame retardant resins. The fire properties were characterized by limiting oxygen index (LOI) and cone calorimetry. A distinct synergistic effect was found between SPUA and DGTH. The thermal degradation was characterized by thermogravimetric analysis and real time Fourier‐transform infrared spectroscopy. The TG results have been found to correlate well with the LOI results. A degradation mechanism has been suggested that the 9,10‐dihydro‐oxa‐10‐phosphaphenantrene‐10‐oxide (DOPO) group in DGTH first degraded to form poly(phosphoric acid)s, which further catalyzed the degradation of the material to form char with emission of nitrogen volatiles from SPUA, leading to the formation of expanding char. The morphologic structures of crusts of the formed chars were observed by scanning electron microscopy, confirming the synergistic effect between SPUA and DGTH. POLYM. ENG. SCI., 48:116–123, 2008. © 2007 Society of Plastics Engineers
Organic–inorganic hybrid materials derived from epoxy resin and polysiloxanes: Synthesis and characterization
Authors: Canto C.F. , Prado L.A.S. de A. , Radovanovic E. , Yoshida I.V.P. 
Published: December 2007

AbstractIn this study, hybrid materials based on epoxy resin were prepared as transparent self‐supported films by a sol–gel process. 4,4′‐Diaminodiphenylmethane or oligomeric epoxy resin were used as precursors, which were conveniently functionalized with trialkoxysilanes as end‐groups. The effect of the introduction of poly (dimethylsiloxane) was also investigated. The hybrid films showed good thermal stability, a nondefined glass transition temperature, and a dense morphology without phase segregation. The tendency to a flat surface could be observed by atomic force microscopy. The hybrid films also showed good performance as coatings for glass plates, with an improved hydrophobic character in comparison to neat epoxy resin. POLYM. ENG. SCI., 48:141–148, 2008. © 2007 Society of Plastics Engineers
A practical approach to modeling time‐dependent nonlinear creep behavior of polyethylene for structural applications
Authors: Liu Hongtao , Polak Maria Anna , Penlidis Alexander 
Published: December 2007

AbstractThe purpose of this work is to develop a practical method for constitutive modeling of polyethylene, based on a phenomenological approach, which can be applied for structural analysis. Polyethylene is increasingly used as a structural material, for example, in pipes installed by trenchless methods, where the relatively low stiffness of polyethylene reduces the required installation forces, chemical inertness makes it applicable for corrosive environments, and adequate strength allows its use in sewer, gas, and water lines. Polyethylene exhibits time‐dependent constitutive behavior which is also dependent on the applied stress level resulting in nonlinear stress–strain relationships. Nonlinear viscoelastic theory has been well established and a variety of modeling approaches have been derived from it. To realistically utilize the nonlinear modeling approaches in design, a simple method is needed for finding a constitutive formulation for a specific polyethylene type. This paper presents such a practical approach to nonlinear viscoelastic modeling utilizing both the multi‐Kelvin element theory and the power law functions to model creep compliance. Creep tests are used to determine material parameters and models are generated for four different polyethylene materials. The corroboration of the models is completed by comparisons with results from different tensile creep, step‐loading creep, and load‐rate tests. POLYM. ENG. SCI., 48:159–167, 2008. © 2007 Society of Plastics Engineers
Effects of crystallization on dispersion of carbon nanofibers and electrical properties of polymer nanocomposites
Authors: Tjong S.C. , Liang G.D. , Bao S.P. 
Published: December 2007

AbstractPolymer nanocomposites filled with low volume fractions of carbon nanofibers (CNFs) were prepared by melt‐compounding. Three types of polymers with different crystallization behavior, i.e., weakly‐crystallized low density polyethylene (LDPE), strongly crystallized high density polyethylene (HDPE) and amorphous polystyrene (PS), were selected as matrices for the nanocomposites. The effects of polymer crystallization on the dispersion of CNFs were examined. Optical and electron microscopic examinations revealed that the dispersion of CNFs in the nanocomposite matrices was strongly depended on the crystallization behavior of polymer matrices. The CNFs were found to disperse uniformly in weakly crystallized LDPE and amorphous PS matrices, but agglomerated in HDPE due to its strong crystallization tendency. Such a distinct dispersion behavior of CNFs in polymers had a profound effect on the electrical properties of the nanocomposites investigated. The PS/CNF nanocomposites exhibited the lowest percolation threshold. The HDPE/CNF nanocomposites showed the largest percolation threshold due to the CNF agglomeration within the amorphous phase of HDPE. POLYM. ENG. SCI., 48:177–183, 2008. © 2007 Society of Plastics Engineers
The friction and wear properties of clay filled PA66
Authors: Mu Bo , Wang Qihua , Wang Tingmei , Wang Honggang , Jian Lingqi 
Published: December 2007

AbstractPolyamide 66(PA66)/clay nanocomposites were prepared by direct melt compounding. The mechanical and tribological properties were evaluated. It was found that addition of clay into PA66 increased the bending strength and microhardness of PA66. And also, the incorporation of clay can reduce the friction coefficient of PA66. The nanocomposites which have the mass fraction less than 5% show less wear rate compared with neat PA66. High fraction of clay can cause severe agglomerated abrasives. The differences in the friction and wear behaviors of PA66 and PA66/clay nanocomposites are attributed to the differences in their surface morphologies, transfer film characteristic. The agglomerated abrasives on the worn surface contribute to the increase of wear rate of nanocomposites of higher mass fraction clay. The friction and wear behaviors of PA66 and its nanocomposites under high temperature exhibit similar tendency with those under 25°C. POLYM. ENG. SCI., 48:203–209, 2008. © 2007 Society of Plastics Engineers
Synthesis and supramolecular self‐assembly of thermosensitive amphiphilic star copolymers based on a hyperbranched polyether core
Authors: Hong Haiyan , Mai Yiyong , Zhou Yongfeng , Yan Deyue , Chen Yan 
Published: December 2007

AbstractA novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3‐ethyl‐3‐(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2‐(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self‐assembly. All the copolymers directly aggregated into core–shell unimolecular micelles (around 10 nm) and size‐controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and 1H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature‐dependent release properties of HBPO‐star‐PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin‐loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668–681, 2008
Poly(methyl methacrylate)/multiwalled carbon nanotube microspheres fabricated via in‐situ dispersion polymerization
Authors: Kwon Soon‐Min , Kim Hun‐Sik , Myung Seung Jun , Jin Hyoung‐Joon 
Published: December 2007

AbstractPoly(methyl methacrylate)/multiwalled carbon nanotube (PMMA/MWCNT) microspheres were successfully prepared by in situ dispersion polymerization in an alcohol phase in which the acid‐treated MWCNTs were dispersed before polymerization. The PMMA and PMMA/MWCNT microspheres were monodisperse. The diameters of the microspheres decreased from about 11.6–6.0 μm as the MWCNT content was increased from 0 to 0.03 wt %. The morphology of the PMMA/MWCNT microspheres was investigated by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy, and the experimental results showed that the MWCNTs were present both in the interior and on the surface of the microspheres. The synthesized PMMA/MWCNT microspheres were also characterized by electrical resistance measurements to analyze their electrical conductivity. They showed electrorheological (ER) fluid characteristics when they were dispersed in silicone oil. Their ER properties were confirmed by using optical microscopy to examine a suspension of the PMMA/MWCNT microspheres dispersed in insulating silicone oil to which an electric field of 2.5 kV/cm was applied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 182–189, 2008
Effect of beam stiffness–column reinforcement on creep and shrinkage behaviour of R.C frames
Authors: Sharma R. K. , Maru Savita , Nagpal A. K. 
Published: December 2007

AbstractVertical deflections and load transfer among columns of R.C frames depend on the percentage of reinforcement in columns and stiffness of beams. No systematic studies are available in the literature on the effect of these parameters. Such systematic studies are reported in this paper. The beam stiffness is expressed in terms of a non‐dimensional parameter, designated as stiffness factor, which is the ratio of shear stiffness of beams to axial stiffness of columns. It is shown that depending on stiffness factor and column reinforcement, a column may receive the load from the adjacent columns or transfer the load to the adjacent columns, or may receive the load from one of the adjacent columns and at the same time transfer the load to the other adjacent column. Further, the effect of the creep and shrinkage on column axial forces can be of design significance in the lower and middle portions of buildings. The effect becomes greater with the increase in stiffness factor and difference in percentage reinforcement of the adjacent columns. Copyright © 2007 John Wiley & Sons, Ltd.
Parathyroidectomy for Renal Hyperparathyroidism in Children and Adolescents
Authors: Schlosser Katja , Schmitt Claus P. , Bartholomaeus Johanna E. , Suchan Katrin L. , Buchler Markus W. , Rothmund Matthias , Weber Theresia 
Published: December 2007

AbstractBackgroundRenal hyperparathyroidism (rHPT) almost inevitably develops in pediatric patients with end‐stage chronic kidney disease (CKD) and may require parathyroidectomy (PTX) despite intensified conservative therapy. Long‐term duration of uncontrolled rHPT may result in disabling osteodystrophy and vascular calcifications. Only a few reports on children undergoing PTX for rHPT are available and mainly consist of case reports with short follow‐up periods. To study this entity, we analyzed the course of 23 pediatic patients who underwent PTX for rHPT.MethodsTwenty‐three patients with a mean age of 15 years and who underwent PTX for rHPT between 1986 and 2006 were evaluated. Surgical indications and techniques, specific postoperative management, and follow‐up courses are described.ResultsPreoperative mean serum (s‐) calcium was 2.7 ± 0.05 mmol/L (normal range = 2.2–2.7 mmol/L); s‐phosphate was 1.8 ± 0.1 mmol/L (normal range = 0.8–1.6 mmol/L), and mean intact parathyroid hormone (PTH) level was 1240.1 ± 160.1 pg/ml (normal range = 11–65 pg/ml). Twenty‐one patients underwent initial PTX and two patients underwent reoperative PTX. Total PTX with parathyroid autotransplantation (AT) was performed in 18 patients. In three patients less than four parathyroid glands were identified and no AT was performed consecutively. Postoperatively, no complications with respect to bleeding or vocal cord damage were recorded. The postoperative values of s‐calcium, s‐phosphate, and PTH decreased to or below normal range (s‐calcium = 2.0 ± 0.1 mmol/L, s‐phosphate = 1.2 ± 0.1 mmol/L, PTH = 50.1 ± 11.2 pg/ml). All 15 children below the age of 15 years required calcium intravenously. Follow‐up was obtained in all patients 69.6 ± 11.4 months after PTX. Bone pain resolved in all previously symptomatic patients. S‐calcium was 2.2 ± 0.2 mmol/L, s‐phosphate was 1.4 ± 0.3 mmol/L, and PTH was 90.2 ± 21.5 pg/ml. No patient required repeated parathyroid autografting, and only one underwent an explantation of his AT six years after initial PTX.ConclusionTotal PTX with AT in pediatric patients with rHPT is a safe and effective procedure. It should be considered if rHPT is refractory to conservative treatment, in view of the risk of potentially lethal vascular calcifications developing in the majority of adults with childhood onset of CKD.
Effect of Dopant on the Nanostructured Morphology of Poly (1-naphthylamine) Synthesized by Template Free Method
Authors: Riaz Ufana , Ahmad Sharif , Ashraf S Marghoob 
Published: December 2007

Abstract
The study reports some preliminary investigations on the template free synthesis of ascantly investigated polyaniline (PANI) derivative—poly (1-naphthylamine) (PNA) by template free method in presence as well as absence of hydrochloric acid (HCl) (dopant), using ferric chloride as oxidant. The polymerization was carried out in alcoholic medium. Polymerization of 1-naphthylamine (NPA) was confirmed by the FT-IR as well as UV–visible studies. The morphology and size of PNA particles was strongly influenced by the presence and absence of acid which was confirmed by transmission electron microscopy (TEM) studies.
Lycopene attenuates thermal hyperalgesia in a diabetic mouse model of neuropathic pain
Authors: Kuhad Anurag , Sharma Sameer , Chopra Kanwaljit 
Published: December 2007

AbstractDiabetic neuropathic pain, an important microvascular complication of diabetes mellitus is recognized as one of the most difficult types of pain to treat. The development of tolerance, inadequate relief and potential toxicity of classical antinociceptives warrant the investigation of the newer agents to relieve this pain. The aim of the present study was to explore the antinociceptive effect of lycopene and its effect on tumour necrosis factor‐α (TNF‐α) and nitric oxide (NO) release in streptozotocin induced diabetic mice. Four weeks after a single intraperitoneal injection of streptozotocin (200mg/kg), mice were tested in the tail immersion and hot‐plate assays. Diabetic mice exhibited significant hyperalgesia alongwith increased plasma glucose and decreased body weights as compared with control mice. Lycopene (1, 2 and 4mg/kg body weight; per oral) treatment, from the 4th to 8th week after streptozotocin injection, significantly attenuated thermal hyperalgesia and the hot‐plate latencies. Lycopene also inhibited the TNF‐α and NO release in a dose dependent manner. These results indicate an antinociceptive activity of lycopene possibly through its inhibitory action on NO and TNF‐α release and point towards its potential to attenuate diabetic neuropathic pain.