bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and properties of polypropylene/hydrotalcite nanocomposites
Authors: Ardanuy M. , Velasco J.I. , Antunes M. , Rodriguez‐Perez M.A. , de Saja J.A. 
Published: April 2009

AbstractThis article presents the study of the modification of the particle/matrix interface region and its effects on the structure and dynamic mechanical behavior of polypropylene (PP)/hydrotalcite nanocomposites prepared by melt extrusion. The interface modification was promoted by combinying the organophillization of the hydrotalcite particles with blending the PP with a maleic anhydride‐grafted‐PP (PP‐g‐MAH) or a maleic anhydride‐grafted‐poly(styrene‐co‐ethylenebutylene‐co‐styrene) (SEBS‐g‐MAH). Sodium dodecyl sulphate was used to promote the organophillization of the hydrotalcite particles. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) showed a partially exfoliated hydrotalcite structure, with an increasing exfoliation being achieved by adding a compatibilizer and organo‐modifying the particles. Values of the Young's modulus (E), storage modulus (E′), maximum tensile strength (σmax), neck propagation strength (σneck), and elongation at break (εb) were found to depend both on the nature of the particle matrix interface as well as on the type of compatibilizer. Also, nanocomposites prepared with the organophillized particles showed lower Tg and loss factor values. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Moisture absorption in foam‐cored composite sandwich structures
Authors: Avilés F. , Aguilar‐Montero M. 
Published: April 2009

AbstractThe hygroscopic behavior of sandwich structures composed of E‐glass/polyester face sheets bonded to a PVC foam core exposed to 95% relative humidity and immersed in sea‐water is examined herein. Moisture uptake was monitored for 11 months yielding absorption curves for samples of polyester resin, laminated composites, PVC foam core, and a sandwich structure. The coefficients of diffusion and moisture saturation values extracted from the curves are significantly greater for the water immersed condition than for the exposed to elevated moisture one, and point to the foam core as the most absorbing material in the sandwich structure. The measured absorption curves are compared to a diffusion model which employs the calculated coefficient of diffusion, showing good agreement. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Thermal and morphological characterization of composites prepared by solution crystallization method of high‐density polyethylene on carbon nanotubes
Authors: He Linghao , Xu Qun , Song Rui , Hua Chengwu 
Published: April 2009

AbstractThe morphology, nucleation, and crystallization of polyethylene/carbon nanotubes composites prepared by solution crystallization method of high density polyethylene on Multiwall Carbon Nanotubes (MWNTs) are studied. Transmission electron microscopy (TEM) results show that the center stems of MWNTs are decorated with lamellar crystals. The nonisothermal crystallization kinetics of pure PE and PE/MWNTs composites are investigated by differential scanning calorimetry at various cooling rates. It is found that the Avrami analysis modified by Jeziorny and Mo can describe the nonisothermal crystallization process of pure PE and PE/MWNTs very well. The difference in the value of exponent between PE and PE/MWNTs suggests that addition of the MWNTs influences the mechanism of nucleation and the growth of PE crystallites. On one hand, the increasing of temperature corresponding to the maximum rate of crystallization and the onset crystallization temperature and the study of the nucleation activity reveal that the inorganic component (MWNTs) can act as the nucleating agent to facilitate the crystallization of PE in the hybrids. On the other hand, the decreasing degree of crystallinity and the increasing of half‐crystallization time imply that the MWNTs networks confine the crystallization of PE. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Effect of multi‐walled carbon nanotubes on crystallization, thermal, and mechanical properties of poly(vinylidene fluoride)
Authors: He Linghao , Xu Qun , Hua Chengwu , Song Rui 
Published: April 2009

AbstractComposites were prepared by solution blending poly(vinylidene fluoride) (PVDF) and multi‐walled carbon nanotubes (MWNTs). Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) results showed that the crystalline structure of PVDF was changed by the addition of MWNTs and a MWNTs‐induced crystal transformation from α‐phase to β‐phase of PVDF was confirmed. With differential scanning calorimeter (DSC) and dynamic mechanic thermal analysis (DMA) techniques, thermal and mechanical properties of the composite films were examined. As the DSC results showed, addition of MWNTs would lead to the increased cooling crystallization temperature (Tc), implying that MWNTs nanoparticles could act as nucleating agents, which is further proved with the help of polarized optical microphotographs. On the other hand, the decreasing of Dd (degree of crystallinity) implied that the MWNTs networks can confine the crystallization of PVDF. Through the curve analysis of the dynamic mechanical measurements, it was found that the storage modulus (E′) is significantly enhanced, revealing that a strong interaction should exist between PVDF and MWNTs. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Prenatal features of Costello syndrome: ultrasonographic findings and atrial tachycardia
Authors: Lin Angela E. , O'Brien Barbara , Demmer Laurie A. , Almeda Kristina K. , Blanco Cynthia L. , Glasow Patrick F. , Berul Charles I. , Hamilton Robert , Micheil Innes A. , Lauzon Julie L. , Sol‐Church Katia , Gripp Karen W. 
Published: April 2009

AbstractObjectiveDelineate prenatal features of Costello syndrome (caused by HRAS mutations), which consists of mental retardation, facial, cardiovascular, skin, and musculoskeletal anomalies, and tumor predisposition.MethodsLiterature and new cases classified as Group I (pre‐HRAS), Group II (HRAS confirmed), and Group III (HRAS confirmed in natural history study, plus three contributed cases).ResultsPolyhydramnios occurred in most (mean 79%) pregnancies of cases in Groups I (98), II (107), and III (17); advanced paternal age and prematurity were noted in approximately half. Less frequent were nuchal thickening, ascites, shortened long bones, abnormal hand posture, ventriculomegaly, macrosomia, and macrocephaly. Fetal arrhythmia occurred in nine cases (six supraventricular or unspecified tachycardia, one unspecified arrhythmia, and two premature atrial contractions, PACs); excluding three new cases and two with PACs, the estimated prenatal frequency is 4/222 (2%).ConclusionCostello syndrome can be suspected prenatally when polyhydramnios is accompanied by nuchal thickening, hydrops, shortened long bones, abnormal hand posture, ventriculomegaly, large size, and macrocephaly, and especially fetal atrial tachycardia. Consideration should be given for timely prenatal diagnostic studies for confirmative HRAS gene mutations and for maternal treatment of serious fetal arrhythmia. Copyright © 2009 John Wiley & Sons, Ltd.
Morphological, thermal, and mechanical characteristics of polymer/layered silicate nanocomposites: The role of filler modification level
Authors: Marras S.I. , Tsimpliaraki A. , Zuburtikudis I. , Panayiotou C. 
Published: April 2009

AbstractComposite materials consisting of poly(L‐lactic acid) and montmorillonite modified to a different extent, using various contents of hexadecylammonium cation, were prepared by the solution intercalation method. Investigation of the composites' morphology revealed that a surfactant quantity higher than the mineral's cation exchange capacity (CEC) was necessary for the organomodified clay to be dispersed at nanoscale level into the polymer matrix. The surfactant content in organoclay was found to play a major role in controlling the composite's mechanical properties. Thus, although increase of the alkylammonium concentration initially enhanced these properties, even higher concentrations corresponding to higher modification levels had a negative impact to them causing their dramatic deterioration. Observation of the deformed surfaces showed that the deformation process mechanism of the material is directly related to the degree of clay modification. Thermal degradation studies revealed that the intermediate surfactant excess reinforces the thermal stability of the nanocomposite by increasing the onset decomposition temperature. Additionally, the alkylammonium concentration was found to affect the crystallization temperature and the glass transition temperature of the polymer. In conclusion, an ideal balance between thermal and mechanical properties can be obtained at surfactant quantity equivalent to 1.5 times the clay CEC. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Polystyrene/Sr2Ce2Ti5O15 composites with low dielectric loss for microwave substrate applications
Authors: Subodh G. , Deepu V. , Mohanan P. , Sebastian M.T. 
Published: April 2009

AbstractSr2Ce2Ti5O15 (Strontium Cerium Titanate or SCT) ceramic was prepared by solid‐state route. A composite of polystyrene/Sr2Ce2Ti5O15 was made using melt mixing technique in a Kneading machine. The microstructure of the composite was investigated using a Scanning Electron Microscope. The dielectric properties of the composites were studied at radio frequency and microwave frequencies. It is observed that relative permittivity and loss tangent increase with volume fraction of the ceramics. The mechanical properties of the composites were investigated using microhardness tester. For 50 volume percentage loading of the ceramic, the composite has relative permittivity of 13.6and dielectric loss of 4.28 × 10−4. The experimentally observed permittivity was compared with the theoretical models. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Stretching induced steric interaction between backbone and side chain in a novel polyimide fiber
Authors: Liu Xiangyang , Pan Rui , Xu Wei , Ye Guangdou , Gu Yi 
Published: April 2009

AbstractStretching induces to form electric interaction between backbone and mesogenic side chain in the bulk of a novel polyimide fiber that was synthesized from 4,4′‐oxydiphthalicanhydride (ODPA) and 6‐(4‐phenyl phenoxy) hexyl‐3,5‐diaminobenzoate (DABBE6), which results in unusual in situ self‐reinforced function, and surprisingly, zigzag undulation of mechanical properties of the annealed polyimide fibers with increasing draw ratios. X‐ray scattering and differential scanning calorimetry (DSC) results indicate that some order structures develop in the annealed fibers under tensile stress. Dynamic thermomechanical analysis (DMA) and DSC results also indicate that no phase separation is observed between backbone and side chain. Further results of experiments and computer molecular simulation prove that the biphenyl side chain can be parallel to the backbone via methylene spacers bending and together align orientationally under tensile stress to develop electronic interaction, and the molecular conformations are stabilized to form binding‐like molecular structures by the interaction to enhance strength and rigidity of backbone. Meanwhile, formation of the interaction depends on the relative position between backbone and the trail phenyl group of side chain, which contributes to the zigzag undulation of tensile strength and initial modulus of the polyimide fibers. In addition, relationship of draw ratios and formation of the interaction was established, and a corresponding backbone‐side chain‐packing model was suggested. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Simulation of phase‐change heat transfer during cooling stage of gas‐assisted injection molding of high‐density polyethylene via enthalpy transformation approach
Authors: Yang Bin , Fu Xiao‐Rong , Yang Wei , Liang Shui‐Po , Hu Shen , Yang Ming‐Bo 
Published: April 2009

AbstractGas‐assisted injection molding (GAIM) is one of the significant fabricating technologies of plastics in modern industry, mainly owing to the light weight of products, good structural rigidity and dimensional stability, as well as shorter molding cycles. The objective of this article is to explore the temperature profiles during the cooling stage of gas‐assisted injection molded high‐density polyethylene (HDPE) parts using a transient heat transfer model of the enthalpy transformation method, which could always be utilized for the numerical studies of the phase‐change heat transfer issues. The simulated results were validated by the in situ measurement of temperature decay, and good agreement has been observed. The comparison between GAIM and conventional injection molding (CIM) reveals that it is the rapid cooling rate (because of thin wall‐thickness) and the inner gas cooling effects that together lead to the shortening of molding cycles. As cooling rate plays a part in the stabilization of the crystalline structure during the GAIM process according to our previous studies, this work is of significance for the operational designs in GAIM industrial applications and further investigation on the detailed mechanisms of various crystalline structures in GAIM parts. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
A new explicit simulation for injection molding and its validation
Authors: Cheng Zhiqiang , Barriere Thierry , Liu Baosheng , Gelin Jean‐Claude 
Published: April 2009

AbstractThe simulation of injection molding involves the filling of cavities and runners in complicated shapes. The 3D elements in large numbers are generally required to satisfy the precise simulation of real processes. It results in the computation in large scales, so that the efficiency of computation becomes very important. On the basis of previous explicit software realized by the authors, the new algorithm avoids the global solution for pressure fields to improve its efficiency. Another feature of the new algorithm is the use of same order interpolation elements instead of MINI elements, which simplifies significantly the software procedures. Except for the operations at element level, neither global solution nor the construction of global matrix is required in simulation. A special feedback regulation strategy is used to meet the incompressibility in filled domain at each time step. In case of the mold filling problems, this method provides a fast way to simulate the filling processes. The computational cost is about linearly proportional to the degree of freedom number. Comparison of velocity field obtained by the previous algorithm using MINI element and analytical theoretical solution proves that the feedback regulation strategy in the new algorithm can satisfy well incompressibility. Moreover, comparison with the results of filling process and temperature field obtained by the previous algorithm proves the validity of the new algorithm. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Synthesis and characterization of a thermotropic liquid crystalline hyperbranched polyester
Authors: Cai Liming , Lu Yafei 
Published: April 2009

AbstractBACKGROUND: Hyperbranched polymers have received increasing attention in the fields of medicine, homogeneous catalysis and materials science. Hydroxyl‐functional aliphatic polyesters are one of the most widely investigated families of hyperbranched polymers. The research reported here is based on the preparation of a novel hyperbranched polyester and the modification of its terminal hydroxyl groups by biphenyl mesogenic units.RESULTS: 2,2,6,6‐Tetramethylolcyclohexanol as a core and 8‐[4′‐propoxy(1,1‐biphenyl)yloxy]octanoic acid as a mesogenic unit were synthesized. A hyperbranched polyester (HPE) was synthesized in one step and subsequently substituted by reaction of its terminal hydroxyl groups with the biphenyl mesogenic units to yield a novel liquid crystalline hyperbranched polyester (HPE‐LC). The chemical structures of all compounds were confirmed using Fourier transform infrared, 1H NMR and 13C NMR spectroscopy. The thermal behavior and the mesogenic properties of the biphenyl mesogenic unit and HPE‐LC were investigated using differential scanning calorimetry, polarized optical microscopy and wide‐angle X‐ray diffraction. The results demonstrated that the degree of branching of the HPE is ca 0.63. Both HPE‐LC and the biphenyl mesogenic unit exhibit mesomorphic properties, but HPE‐LC has a lower isotropic transition temperature and a wider transition temperature range than the biphenyl mesogenic unit.CONCLUSION: A novel liquid crystalline hyperbranched polyester was successfully synthesized, which exhibits mesomorphic properties. This polymer has good solubility in highly polar solvents and good thermal stability. Copyright © 2009 Society of Chemical Industry
Liquid crystalline conjugated polymers and their applications in organic electronics
Authors: Yang Sheng‐Hsiung , Hsu Chain‐Shu 
Published: April 2009

AbstractThis article describes the syntheses and electro‐optical applications of liquid crystalline (LC) conjugated polymers, for example, poly(p‐phenylenevinylene), polyfluorene, polythiophene, and other conjugated polymers. The polymerization involves several mechanisms: the Gilch route, Heck coupling, or Knoevenagel condensation for poly(p‐phenylenevinylene)s, the Suzuki‐ or Yamamoto‐coupling reaction for polyfluorenes, and miscellaneous coupling reactions for other conjugated polymers. These LC conjugated polymers are classified into two types: conjugated main chain polymers with long alkyl side chains, namely main‐chain type LC polymers, and conjugated polymers grafting with mesogenic side groups, namely side‐chain type LC conjugated polymers. In general, the former shows higher transition temperature and only nematic phase; the latter possesses lower transition temperature and more mesophases, for example, smectic and nematic phases, depending on the structure of mesogenic side chains. The fully conjugated main chain promises them as good candidates for polarized electroluminescent or field‐effect devices. The polarized emission can be obtained by surface rubbing or thermal annealing in liquid crystalline phase, with maximum dichroic ratio more than 20. In addition, conjugated oligomers with LC properties are also included and discussed in this article. Several oligo‐fluorene derivatives show outstanding polarized emission properties and potential use in LCD backlight application. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2713–2733, 2009
Polyisobutylene‐based polyurethanes. II. Polyureas containing mixed PIB/PTMO soft segments
Authors: Jewrajka Suresh K. , Kang Jungmee , Erdodi Gabor , Kennedy Joseph P. , Yilgor Emel , Yilgor Iskender 
Published: April 2009

AbstractThe design, synthesis, characterization, and structure–property behavior of polyureas containing novel soft segments of mixed polyisobutylene (PIB)/poly(tetramethylene oxide) (PTMO) chains and conventional hard segments is presented. Modest amounts (12%) of PTMO in the soft PIB phase significantly increase both the tensile strength and elongation of the polyureas. These polyureas exhibit not only oxidative/hydrolytic stabilities far superior to Bionate® and Elast‐Eon® considered the most oxidatively stable polyurethanes on the market but also display mechanical properties (29 MPa tensile strength and 200% elongation) approaching those of conventional thermoplastic polyurethanes. The surfaces of these polyureas are covered/protected by PIB segments, which will lead to excellent biocompatibility. Our results demonstrate that the PTMO segments facilitate stress transfer from the continuous mixed soft phase to the dispersed hard phase, which strengthens and flexibilizes PIB‐based polyureas and thus significantly improves elastomeric properties without compromising oxidative and hydrolytic stability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2787–2797, 2009
Experimentally facile controlled polymerization of N‐carboxyanhydrides (NCAs), including O‐benzyl‐L‐threonine NCA
Authors: Gibson Matthew I. , Cameron Neil R. 
Published: April 2009

AbstractIt is demonstrated here that three different α‐amino N‐carboxyanhydrides (NCAs), including for the first time O‐benzyl‐L‐threonine NCA, can be polymerized in a controlled/“living” fashion without the need for transition metal catalysts or complex custom‐made glassware. Homopolymerizations in tetrahydrofuran gave monomodal distributions, high conversions, predictable Mn values and displayed first‐order kinetics. Chain extension experiments from poly(benzyl‐L‐threonine), using N,N‐dimethylacetamide to avoid the formation of insoluble β‐sheets, was used to create a range of block copolypeptides of controlled structure. Monomodal molecular weight distributions are observed throughout and molecular weights agree well with predicted values, although polydispersities are generally higher than those observed using more experimentally challenging techniques. This method therefore represents a practical approach to the synthesis of well‐defined polypeptides without the requirement for specialized glassware or glove‐box techniques. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2882–2891, 2009
Synthesis and properties of chitosan‐based thermo‐ and pH‐responsive nanoparticles and application in drug release
Authors: Chuang Chung‐Yang , Don Trong‐Ming , Chiu Wen‐Yen 
Published: April 2009

AbstractIn this research, thermo‐ and pH‐responsive nanoparticles with an average diameter of about 50–200 nm were synthesized via the surfactant‐free emulsion polymerization. The thermal/pH dual responsive properties of these nanoparticles were designed by the addition of a pH sensitive monomer, acrylic acid (AA), to be copolymerized with N‐isopropylacrylamide (NIPAAm) in a chitosan (CS) solution. The molar ratio of CS/AA/NIPAAm in the feed was changed to investigate its effect on structure, morphology, thermal‐ and pH‐responsive properties of the nanoparticles. It was found that CS‐PAA‐PNIPAAm nanoparticles could be well dispersed in the aqueous solution and carried positive charges on the surface. The addition of thermal‐sensitive NIPAAm monomer affected the polymerization mechanism and interactions between CS and AA. The particle size of the nanoparticles was found to be varied with the composition of NIPAAm monomer in the feed. The synthesized nanoparticles exhibited stimuli‐responsive properties, and their mean diameter thus could be manipulated by changing pH value and temperature of the environment. The nanoparticles showed a continuous release of the encapsulated doxycycline hyclate up to 10 days during an in vitro release experiment. The environmentally responsive nanoparticles are expected to be used in many fields such as drug delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2798–2810, 2009