bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermomechanical properties of arylamine‐based benzoxazine resins alloyed with epoxy resin
Authors: Rimdusit Sarawut , Kunopast Pathomkorn , Dueramae Isala 
Published: April 2011

AbstractEffects of epoxy resin on various arylamine‐based benzoxazine resins, i.e., aniline (BA‐a), m‐toluidine (BA‐mt), and 3,5‐xylidine (BA‐35x), have been investigated. Processing windows of BA‐35x, BA‐mt, and BA‐a were found to be widened with the amount of the epoxy. Gel points of benzoxazine‐epoxy resin mixtures can be predicted by an Arrhenius equation, e.g., gel time of BA‐35x and epoxy mixture at 70:30 mass ratio can be estimated by tgel = 0.7012 × 10−7 exp (10.563/T). Glass transition temperature (Tg) of BA‐a and BA‐mt alloyed with epoxy exhibited a synergistic behavior with the maximum Tg value at the benzoxazine‐epoxy composition of 80:20 mass ratio. However, in the BA‐35x and epoxy mixture, the decreasing trend in Tg from 241°C to 223°C with an addition of epoxy was observed. Furthermore, flexural strength and strain‐at‐break of those alloys were found to increase with increasing amount of the epoxy while modulus increased with the polybenzoxazine mass fraction. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Method to characterization of the overmolded polymer penetration into the fabric
Authors: Martinez Arantza , Castany Javier , Serraller Francisco 
Published: April 2011

AbstractA penetration into the fabric is a typical defect which appears when plastic is injected over textile and it is able to pass through the fabric to reach the aesthetic side of the part. Once that penetration takes place, the faulty piece is rejected and a possible solution to eliminate the defect is the trial and error process, changing successively the injection parameters, and therefore increasing the production costs. For that reason, it is very important to characterize these penetrations in order to anticipate the injection conditions that cause the defect and consequently, to optimize the overmolded injection process, reducing to the maximum the number of rejected pieces. In this article, the work consists of designing a methodology to combine injection parameters and fabric tension that causes the penetration that appears to characterize them. The combination of minimum tension, minimum injection temperature, and minimum injection pressure in the exact point in which defect appears will characterize the penetration. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Development of a multiple‐hole die for the production of single large blocks of low‐density polystyrene using carbon dioxide as a blowing agent
Authors: van Spronsen Jaap , van Luijtelaer Jeroen P.H. , Stoop Albert , Scheper J. Christian , de Vries Tjerk J. , Kroon Maaike C. 
Published: April 2011

AbstractA multiple‐hole die for the production of single large blocks of polystyrene foam with carbon dioxide as blowing agent was developed. First, single‐hole die experiments were carried out with different hole sizes (2.0, 1.0, and 0.50 mm). Using these single‐hole dies dimensionally‐stable foam was produced with a density of 31 kg m−3 and an open cell structure. Next, the hole diameter and hole distances for a newly constructed multiple‐hole die were chosen on basis of the radial expansion in the single‐hole die experiments. Tests with the multiple‐hole die showed that the seven strings could melt together forming one large string with a diameter of about 20 mm and a density of 50 kg m−3. Therefore, the concept of using a multiple‐hole die for producing single large blocks of polystyrene was proven. However, larger block sizes were not possible because of the limited capabilities of the extruder. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Effects of thermo‐oxidative aging on chain mobility, phase composition, and mechanical behavior of high‐density polyethylene
Authors: Shi Xiaomei , Wang Jingdai , Stapf Siegfried , Mattea Carlos , Li Wei , Yang Yongrong 
Published: April 2011

AbstractThe thermo‐oxidative degradation behavior of high‐density polyethylene (HDPE) was investigated during oven aging at 100°C. 1H low‐field solid‐state nuclear magnetic resonance (NMR) was used to characterize the behaviors of molecular chains and the changes in phase content of HDPE during aging. NMR free induction decays (FIDs) were fitted by three components corresponding to the crystalline phase, interphase, and amorphous phase, respectively. The prolongation of aging led to a progressive increase in the crystalline phase at the expense of the other two phases. A slight decrease in chain mobility of the crystalline phase and interphase was observed simultaneously. The results obtained from other traditional technical approaches are also discussed in the context of the molecular dynamics properties revealed by NMR. The reduction in molecular weight, in chain mobility and the increase in crystallinity during thermo‐oxidation were the main factors, which caused the loss of mechanical performance of HDPE. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Novel hyperbranched polyphenylsilsesquioxane‐modified cyanate ester resins with improved toughness and stiffness
Authors: Zhuo Dongxian , Gu Aijuan , Liang Guozheng , Hu Jiang‐tao , Yuan Li , Ji Lifu 
Published: April 2011

AbstractHigh‐performance thermosetting resins should have good toughness and stiffness, so simultaneously toughening and stiffening is the main target in developing high‐performance resins. A novel modified cyanate ester resin with improved toughness and stiffness was developed by copolymerizing 2,2′‐bis(4‐cyanatophenyl)isopropylidene (CE) with hyperbranched polyphenylsilsesquioxane (HBPPSi). The mechanical properties and their nature were systematically investigated from the viewpoint of structure‐property relations using positron annihilation lifetime spectroscopy and spectral analyses. It is found that a suitable content of HBPPSi in CE resin can effectively improve toughness and stiffness. In the case of the CE resin modified with 10 wt% HBPPSi, its impact and flexural strengths are 21 kJ m−2 and 148 MPa, respectively, about 2.6 and 1.4 times of those of neat CE resin. The flexural modulus increases from 3.0 (for neat CE resin) to 3.4 GPa. The results of dynamic mechanical analyses also corroborate the static mechanical properties. The improved toughness and stiffness of CE resin can be attributed to the synergistic effect resulting from changes of both polymer chain structure and aggregation state structure. These attractive features of HBPPSi/CE resins suggest that the method proposed herein may be a new approach for the development of high‐performance resins for cutting‐edge industries. Copyright © 2011 Society of Chemical Industry
Supramolecular fuzzy recognition leads to effective differentiation of similar molecules
Authors: Wan Decheng , Pu Hongting , Jin Ming , Wang Guowei , Huang Junlian 
Published: April 2011

AbstractThe separation of structurally similar molecules remains a general challenge; here, we report that a roughly defined macromolecular nanocapsule can efficiently separate a variety of structurally similar mixtures. The nanocapsule is a core−shell amphiphilic macromolecule (CAM) hydrophobically derived from hyperbranched polyethylenimine with 2‐hexadecyloxymethyloxirane. It is found that with further chemical core engineering of the CAM, its guest selectivity can be radically enhanced, although specific host−guest interaction is absent or ignorable in the system. As a result, two groups of structurally similar guests such as fluorescein/tetrachlorofluorescein, and rose bengal/erythrosine B/eosin Y, can be well recognized by the CAMs. It is known that a complex (fuzzy) system is generally characterized by complexity and nonlinearity; thus core engineering of a CAM is possible to amplify the difference of the competitive guests and lead to effective guest differentiation, such a mechanism is called supramolecular fuzzy recognition (SFR). Our results demonstrate that with appropriate combination of various elementary interaction styles, SFR can lead to effective recognition of a wide spectrum of mixtures. Moreover, a SFR host can be roughly defined in structure and thus readily available. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Rendering polyureas melt processible
Authors: Kang Jungmee , Erdodi Gabor , Kennedy Joseph P. 
Published: April 2011

AbstractBecause of the presence of extensive H‐bonding in the hard segments, polyureas are processed by solution techniques (e.g., dry spinning) by the use of relatively costly and environmentally unfriendly solvents. Thus, the objective of this research was to render polyureas melt processible, (i.e., to reduce their flow temperature, Tflow) without compromising their excellent mechanical properties. We hypothesized and herein demonstrate that by using conventional chain extenders (CEs) in combination with small amounts of H‐bond acceptor chain extenders (HACEs), the Tflow of polyureas can be significantly reduced from ∼230 to ∼180 °C, and thus melt processible products with excellent mechanical properties can be obtained. We document the synthesis of conventional polytetramethylene oxide‐based and novel polyisobutylene (PIB)‐based polyureas with Tflows ∼ 180 °C and excellent mechanicals by the addition of few percents of commercially available HACEs. Products were characterized by various techniques, including Instron (tensile strengths, elongations), durometer (Shore A Hardness), dynamic mechanical thermal analysis (Tflow), and thermal gravimetric analysis (TGA) (thermal weight loss). According to TGA, a polyurea with Tflow of ∼180 °C did not degrade up to ∼234 °C in air. A micromorphology for melt processible polyureas is proposed that emphasizes flexibilized hard segments in the presence of HACEs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Comparative study on polyimides from isomeric 3,3′‐, 3,4′‐, and 4,4′‐linked bis(thioether anhydride)s
Authors: Wei Haibing , Pei Xueliang , Fang Xingzhong 
Published: April 2011

AbstractThree isomeric bis(thioether anhydride) monomers, 4,4′‐bis(2,3‐dicarboxyphenylthio) diphenyl ketone dianhydride (3,3′‐PTPKDA), 4,4′‐bis(3,4‐dicarboxyphenylthio) diphenyl ketone dianhydride (4,4′‐PTPKDA), and 4‐(2,3‐dicarboxyphenylthio)‐4′‐(3,4‐dicarboxyphenylthio) diphenyl ketone dianhydride (3,4′‐PTPKDA), were prepared through multistep reactions. Their structures were determined via Fourier transform infrared, NMR, and elemental analysis. Three series of polyimides (PIs) were prepared from the obtained isomeric dianhydrides and aromatic diamines in N‐methyl‐2‐pyrrolidone (NMP) via the conventional two‐step method. The PIs showed excellent solubility in common organic solvents such as chloroform, N,N‐dimethylacetamide, and NMP. Their glass‐transition temperatures decreased according to the order of PIs on the basis of 3,3′‐PTPKDA, 3,4′‐PTPKDA, and 4,4′‐PTPKDA. The 5% weight loss temperatures (T5%) of all PIs in nitrogen were observed at 504–519 °C. The rheological properties of isomeric PI resins based on 3,3′‐PTPKDA/4,4′‐oxydianiline/phthalic anhydride showed lower complex viscosity and better melt stability compared with the corresponding isomers from 4,4′‐ and 3,4′‐PTPKDA. In addition, the PI films based on three isomeric dianhydrides and 2,2′‐bis(trifluoromethyl)benzidine had a low moisture absorption of 0.27–0.35%. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Chemical modification of chain end in nylon 4 and improvement of its thermal stability
Authors: Tachibana Koichiro , Hashimoto Kazuhiko , Tansho Noriyuki , Okawa Haruki 
Published: April 2011

AbstractTwo kinds of nylon 4 having an acyllactam group at one or both chain ends were synthesized by the anionic ring‐opening polymerization of 2‐pyrrolidone using N‐benzoyl‐2‐pyrrolidone (BP) or N,N′‐isophthaloylbis‐2‐pyrrolidone (IPP) and potassium tert‐butoxide as an initiator and a catalyst, respectively, and carefully isolated with the suppression of moisture adsorption. The acyllactam at one chain end in the low molecular weight of nylon 4 was quantitatively converted to other functional groups such as carboxy, amine and so on, which were confirmed by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI TOF) mass spectroscopy. Terminal acyllactam groups telechelating in the nylon 4 at both chain ends were also modified to carboxy and amino groups. From the thermogravimetric analysis (TGA), thermal decomposition point of the modified nylon 4 was increased in comparison with that of the original acyllactam‐type nylon 4, although the acyllactam chain end caused the backbiting depolymerization accompanied with the generation of 2‐pyrrolidone monomer. The direct heating of the acyllactam‐telechelic low molecular weight of nylon 4 mixed with the diamine in bulk also led to improve its thermal stability significantly by the chain extension through the polyaddition reaction. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Polymerization mechanism of trimethylene carbonate carried out with zinc(II) acetylacetonate monohydrate
Authors: Pastusiak Malgorzata , Dobrzynski Piotr , Kaczmarczyk Bozena , Kasperczyk Janusz 
Published: April 2011

AbstractThe proposed mechanism of initiation and course of ring‐opening polymerization of cyclic trimethylene carbonate (TMC) involving zinc(II) acetylacetonate is in accordance with the mechanism of monomer activation. At the first stage of the process, coordination of carbonate to Zn(Acac)2·H2O complex occurs with the release of weakly coordinated water molecules. This free water molecule reacts with active TMC–Zn(Acac)2 complex. The reaction results in the formation of propanediol and CO2 emission. During further stages of the investigated process, the formed propanediols, or later the oligomeric diols produced with polymerization, are cocatalysts of the chain propagation reaction. The chain propagation occurs because of repeating activation of the TMC monomer through the creation of an active structure resulting in the exchange/transfer reaction between the zinc complex and the monomer, with its following attachment to the hydroxyl groups, carbonate ring opening, and formation of the carbonic unit of polymer chain. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Challenges due to aging plants
Authors: Ramírez Pedro A. Pérez , Utne Ingrid Bouwer 
Published: April 2011

AbstractThe management of aging of plants has become an important issue for oil and gas (O&G) companies that intend to extend the lifetime of their facilities. Important requirements are that the installations must be safe and economical to remain in operation. This can be achieved by implementing aging plant management programs to control and mitigate the degradation of the facilities. Aging plants have been a crucial topic for several years within the nuclear power industry, but it is a relatively novel area for the offshore O&G industry. To develop a successful aging plant management program for an existing offshore O&G installation, it is necessary not only to learn from the experience of other industries but also to understand and address the specific challenges for managing the aging of these facilities. The objective of this article is to outline these issues and to highlight future challenges. © 2011 American Institute of Chemical Engineers Process Saf Prog 2011
Time‐resolved ultrafast carrier dynamics in CdTe quantum dots under high pressure
Authors: Liu Bingguo , He Chunyuan , Jin Mingxing , Ding Dajun , Gao Chunxiao 
Published: April 2011

AbstractUltrafast carrier relaxation in CdTe quantum dots (QDs) was studied under high pressure by using femtosecond transient absorption spectroscopy. The pressure effects on the carrier relaxation time are obtained for surface trapped electron‐hole recombination and electronic Auger recombination processes. The decrease of the transient absorption signals and the change of sample colour with pressure are assigned to the shift of the energy levels. This shift of the energy levels can lead to an electron transition for materials. And the abrupt changes of the relaxation time at 0.5 and 1.5 GPa are attributed to the electron transition in CdTe QDs under high pressure. Therefore, the high‐pressure ultrafast carrier dynamics research provides a new approach for studying the electron transition in condensed matter.
Study on phase transition of SrTiO3 by in situ impedance measurement under high pressure
Authors: Wang Qinglin , Yang Jie , Liu Bao , Liu Cailong , Hu Tingjing , Li Yan , Su Ningning , Sang Dandan , Han Yonghao , Gao Chunxiao 
Published: April 2011

AbstractThe pressure dependence of electrical resistance of perovskite SrTiO3 has been studied by in situ impedance measurement in diamond anvil cell up to 31 GPa at room temperature. Two discontinuous changes in resistance were observed at about 9.8 and 21 GPa, which are coincident with the pressure‐induced phase transitions from cubic phase to tetragonal phase and then to orthorhombic phase, respectively. High‐pressure angle dispersive X‐ray diffraction experiments on SrTiO3 powders have also been performed up to 35 GPa. It was found that a structure phase transition from cubic to tetragonal phase begins to take place at about 6.49 GPa but clear indication for a further transition to an orthorhombic phase at higher pressure up to 35 GPa is hardly seen in our X‐ray diffraction data.
The phase transition of Zn0.854Cu0.146O under high pressure
Authors: Jin Yunxia , Zhang Jian , Zhu Pinwen , Gao Wei , Cui Qiliang 
Published: April 2011

AbstractPressure induced phase transition of hexagonal Zn0.854Cu0.146O is studied by using synchrotron angle dispersive X‐ray diffraction (ADXRD) up to 43.1 GPa at room temperature. A structural transformation from a hexagonal phase to a cubic phase is observed, which starts at 10.2 GPa and finishes at about 16.5 GPa. The phase transition leads to a volume collapse of 17% at 10.2 GPa. The cubic phase of Zn0.854Cu0.146O remains stable up to the highest experiment pressure. The pressure–volume data are fitted with the Birch–Murnaghan equation of state. The bulk modulus obtained upon compression from the fitting are 175(2) and 259(6) GPa for the hexagonal and cubic phases, respectively.
Influence of high electron concentration on band gap and effective electron mass of InN
Authors: Donmez O. , Yilmaz M. , Erol A. , Ulug B. , Arikan M. C. , Ulug A. , Ajagunna A. O. , Iliopoulos E. , Georgakilas A. 
Published: April 2011

AbstractEffects of high electron concentration on the band gap energy of InN films having different layer thicknesses as 600 and 800 nm are investigated experimentally and theoretically. Electron concentrations of the samples are obtained through the Hall measurements accomplished between 77 K and room temperature. Optical characterization of the samples is carried out using the photoluminescence (PL) measurements and the observed PL spectra are explained considering the high electron concentration related effects, i.e. Burstein–Moss shift, band renormalization and band tailing in non‐parabolic k · p model. Extracted PL results indicate that the samples have approximately 0.685 eV band gap energy at 77 K. Effective mass of the carriers, which is calculated as 0.097 m0 for electron concentration of ∼1019 cm−3, are also observed to be influenced by the high carrier concentration.
Wavelength selective switching in dilute nitrides multi quantum well photonic band gap waveguides
Authors: Calò Giovanna , Alexandropoulos Dimitris , D'Orazio Antonella , Petruzzelli Vincenzo 
Published: April 2011

AbstractThe analysis of the gain behaviour in active GaInNAs–GaInAs Photonic Band Gap (PBG) ridge waveguides is reported. The analysis is performed using proprietary codes, based on the Bidirectional Beam Propagation Method with the Method of Lines, introducing the rate equations. The bandstructure of the active material is modelled using the k · p theory for the valence band mixing effects and the band anticrossing model for the conduction band. A wavelength selective switch configuration is proposed exploiting a periodic grating patterned on a ridge waveguide in which an active defect is inserted. The presence of the active defect allows the localization of states and the transmission of the optical signal within the PBG. The wavelength selective switching mechanism stems from the possibility of shifting the wavelength of the localized state by properly choosing the defect length and the injected current density. From the numerical analysis, the proposed device exhibits, at the switching wavelength λB = 1.289 µm, good values of the crosstalk CT = −11.55 dB, the contrast ratio CR = 14.29 dB, the modulation depth MD = 0.93, and the bandwidth Δλ = 0.8 nm.
Investigation of the In composition in InGaN/GaN quantum wells deposited by MOVPE and/or MBE with emission from violet to green
Authors: Mutta G. R. , Ruterana P. , Doualan J. L. , Chauvat M. P. , Ivaldi F. , Kret S. , Kaufmann N. A. K. , Dussaigne A. , Martin D. , Grandjean N. 
Published: April 2011

AbstractTransmission electron microscopy and photoluminescence investigations have been carried out on a series of quantum wells grown by molecular beam epitaxy and metal organic vapour phase epitaxy. In both cases, the emission wavelength and the peak width agree with the indium local composition as extracted from strain measurements and with the well width. As could be expected, the data is at small variance with the nominal values as set during growth, but the general trends are similar.
High pressure Raman study of LiBC
Authors: Zhu Pinwen , Han Dandan , Tang Ruilian , Li Nana , Gao Wei , Wang Xin 
Published: April 2011

AbstractThe effects of pressure on the zone‐center optical phonon modes of LiBC, which is structurally and electronically similar to the superconductor MgB2, have been investigated by Raman spectroscopy. At ambient pressure, four main lattice modes have been revealed with frequencies at 1173, 831, 552, and 174 cm−1, respectively, while only lines at 1173 and 174 cm−1 correspond to the expected Raman active E2g modes. The longitudinal‐optical phonon modes involving the Li sheets which can provide a coupling between neighboring B–C planes are expected to couple with the plasmon mode and are suggested to be related with the appearance of the forbidden lines. With increasing pressures, it is found that LiBC remains stable up to 15.5 GPa. All the observed modes harden and exhibit broadening effects under high pressure, especially for the B–C bond stretching mode (at 1173 cm−1) which shows a nonlinear pressure dependence. It indicates that the broadening may be caused by complex coupling interactions, and the pressure‐enhanced coupling should give rise to a strongly anharmonic behavior of these modes.
Phase transition of ZnxMn1‐xS dilute magnetic semiconductor nanoparticles under ultra‐high pressure
Authors: Zong Zhaocun , Ma Yanmei , Hu Tingting , Cui Qiliang , Zhang Mingzhe , Zou Guangtian 
Published: April 2011

AbstractThe high‐pressure behavior of different doping content of ZnS nanocrystals has been investigated using angle‐dispersive synchrotron X‐ray powder diffraction up to 45.1 GPa. A phase transformation from the zinc‐blende(ZB) to the rock‐salt (RS) structure is observed at pressures of about 17.7 and 18.3 GPa at room temperature, corresponding to the Mn2+ ion mole percent content solutions 0.85% and 1.26%, respectively. The obtained results indicate that the Mn2+ doping could obviously enhance the phase transition pressure of ZnS nanocrystal. The elevation of phase transition pressure could origin from the higher surface energy induced by ion doping (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)