bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic Investigation into the Non‐Thermal Microwave Effect on the Ring‐Opening Polymerization of ε‐Caprolactone
Authors: Li Hao , Liao Liqiong , Liu Lijian 
Published: February 2007

AbstractRate constants of the ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) by microwave heating (MH) and flash conventional heating (FCH) have been measured. The reaction is catalyzed by stannous octanoate (Sn(Oct)2). With a microwave power level of 400, 500, 600, 700 and 800 W, the equilibrium temperature of the polymerization mixture increases from 165 to 180, 197, 213 and 228 °C. However, the rate constant does not continuously increase with the observed increase in temperature. Instead it abruptly increases at 180 °C (500 W), and the increase does not fit Arrhenius' law which, however, is followed by the polymerization under FCH conditions with an increase of the equilibrium temperature from 108 to 135, 151, 189 and 213 °C. The initiation time of the ROP by MH varies anomalistically with temperature and is not related to the rate constant, which is in contrast to that by FCH, which reduces exponentially from 127.5 to 36.40, 8.63, 1.22, and 0.579 min with the increase in polymerization temperature and rate constant. Based on the divergences it is reasonable to deduce that the acceleration of the ROP of ε‐CL by microwaves is induced not only by thermal conditions (the thermal microwave effect) but also by the non‐thermal microwave effect.magnified image
Microwave‐Assisted Synthesis under Continuous‐Flow Conditions
Authors: Glasnov Toma N. , Kappe C. Oliver 
Published: February 2007

AbstractMicrowave‐assisted chemistry is about to change the art and practice of synthesis performed in many academic and industrial laboratories. One of the major drawbacks of this enabling technology is the difficulty associated with scale‐up. Because of the limited penetration depth of microwaves into absorbing media, the solution to scale‐up lies in continuous‐flow processing. In this review we summarize the current state of the art in this field and present an overview on published examples of microwave‐assisted synthesis using continuous‐flow and stop‐flow processing in custom‐built or commercially available microwave reactors.magnified image
Microwave Irradiation: A Novel Method for Rapid Synthesis of D,L‐Lactide
Authors: Zhang Ying Min , Wang Peng , Han Ning , Lei Hai Fen 
Published: February 2007

AbstractD,L‐Lactide with a yield of about 36% was synthesized from D,L‐lactic acid by the addition of SnCl2 and Cat‐A as catalyst under continuous microwave irradiation in less than 1 h. In order to gain a higher yield, the viscosity‐average molecular weight of the oligomer was preferably over 3 000 g · mol−1, and the microwave power in the depolymerization process was chosen for 200 W with 100 g of D,L‐lactic acid. On comparison with conventional heating in the same experimental conditions, no non‐thermal effect of microwave irradiation was revealed.magnified image
Microwave‐Assisted Synthesis of PLLA‐PEG‐PLLA Triblock Copolymers
Authors: Zhang Chao , Liao Liqiong , Gong Shaoqin (Sarah) 
Published: February 2007

AbstractPoly(L‐lactide)‐block‐poly(ethylene glycol)‐block‐poly(L‐lactide) (PLLA‐PEG‐PLLA) triblock copolymers were synthesized effectively by poly(ethylene glycol) initiated ring‐opening polymerization (ROP) of L‐lactide under microwave irradiation. The products were characterized by 1H NMR, GPC, and DSC. The experimental results have demonstrated that PLLA‐PEG‐PLLA triblock copolymer with a number‐average molar mass of 28 230 g · mol−1 and an L‐lactide conversion of 92.4% could be synthesized after the L‐lactide/PEG2000 reaction mixture was irradiated for 3 min at 100 °C. The L‐lactide/PEG feed ratio had a strong influence on the microwave‐assisted ring‐opening polymerization, in which higher L‐lactide/PEG feed ratios led to copolymers with higher molar masses and lower L‐lactide conversions. Prolonged microwave irradiation at 100 °C did not change the molar mass of the copolymers significantly. The DSC study indicated that higher glass transition and melting temperatures were obtained for PLLA‐PEG‐PLLA triblock copolymers with longer PLLA segment length. The synthesis of the triblock copolymers via microwave heating was much faster than via conventional heating.magnified image
Microwave‐Accelerated RAFT Polymerization of Polar Monomers
Authors: Brown Steven L. , Rayner Christopher M. , Perrier Sébastien 
Published: February 2007

AbstractA monomodal microwave reactor has been employed, for the first time, for the RAFT‐mediated polymerization of methyl acrylate (MA), methyl methacrylate (MMA) and styrene. At comparable temperatures, and a uniform power output of between 1 and 3 Watts, the microwave outperformed the oil bath in terms of polymerization rate for both MA and MMA, showing rate enhancements of up to 152% and 254% for the two monomers respectively, when compared to conventional heating. Furthermore, the control appears unaffected by the rate increase, yielding low polydispersities (PDIs) (as low as 1.05) and molecular‐weight values close to predicted values. Interestingly, however, the polymerization rate of styrene ‐ a nonpolar monomer ‐ does not seem to be enhanced by the use of microwave heating.magnified image
Comprehensive Modelling of the Experimental Temperature and Stress Response of Time‐Dependent Materials
Authors: André José R. S. , Pinto José J. Cruz 
Published: February 2007

AbstractThe stress‐ and temperature‐dependent non‐linear creep behaviour of polymers and other materials is quantitatively modelled as a superposition of a wide range of activated motions at the molecular scale, covering wide but well‐defined space and time scales. The resulting time, temperature and stress dependences are coupled (not fully separable) except at low stress values, where linear viscoelastic behaviour is directly obtained, improving on previous (approximate or questionable) time‐temperature and time‐stress superposition or equivalence relationships. The behaviour has been shown to have a strong cooperative nature, which may be interpreted in terms of varying clusters of identifiable structural elements within the material. Reasonably good descriptions of the experimental creep behaviour of both amorphous and semicrystalline polymers have already been achieved, but this work concentrates on the behaviour of an amorphous polycarbonate (PC), including the physical characterization and modelling of its retardation time spectrum.
An Electric Criterion to Evaluate Glass Transition Temperature: Dielectric Relaxation Measurements
Authors: D'Angelo P. , Barra M. , Cassinese A. , Guido S. , Tomaiuolo G. 
Published: February 2007

AbstractIn this contribution, a dielectric measurement technique for the evaluation of phase transition temperature and the study of physical aging on polymeric thin films is considered. This kind of measurement provides the possibility of displaying phase transitions with a high degree of precision. Furthermore, it can be considered alternatively to techniques not applicable in the case of thin films, such as Differential Scanning Calorimetry (DSC). In this work, owing to the high sensitivity of the utilized experimental set‐up, a glass transition TG of 156 K, with a precision equal to 0.3%, and a melting TM = 220 K have been assessed for 4 µm thick Polydimethylsiloxane (PDMS) films. Performing measurement as a function of time, it was possible to monitor physical aging phenomena, mainly consisting in a change of dielectric properties. As expected, the time evolution of the aging phenomena can be described by a simple logarithmic law.
Rheological Aspects of PP‐TiO2 Micro and Nanocomposites: A Preliminary Investigation
Authors: Acierno D. , Filippone G. , Romeo G. , Russo P. 
Published: February 2007

AbstractThe linear rheology of PP‐TiO2 composites was investigated as a function of the filler particle size. Small amounts (ϕ = 4.5%) of micron and nano‐sized TiO2 spherical particles were added to the polymer by melt compounding. In spite of the low particle volume fractions and the weak polymer‐filler interactions, relevant changes have been observed in the linear viscoelastic behaviour of the nanostructured formulations. Microstructural analyses performed through electron microscopy have shown a good degree of dispersion of micron‐sized particles. Conversely, the presence of a relevant number of TiO2 nanoparticle clusters has been detected for the nanocomposite. The structure of these aggregates seems to be strongly responsible for the rheological behaviour of these last materials in comparison with microstructured ones. Relevant similarities between the viscoelastic properties of nanocomposite and the flow feature of many soft glassy materials have been noticed, and a simple physical picture has been proposed in order to interpret the rheological response of studied nanocomposites.
Organic‐Inorganic Hybrid Fillers for The Controlled Release of Antioxidants
Authors: Mascia Leno , Capra Carlo , Lavorgna Marino 
Published: February 2007

Abstractthe barrier provided by the inorganic domains of organic‐inorganic hybrids towards the absorption of low molecular weight penetrants was used in this study as a basis for the development of systems capable of desorbing antioxidants at a slow rate. Polyethyleneoxide‐silica hybrids, compatibilized with glycidoxylpropyltrimethoxysilane, were used as carriers of conventional stabilizers for polymers, respectively two phenolic antioxidants and one hindered aromatic diamine system. Ternary phase diagrams were produced in order to determine the “compatibile compositions” using DSC to measure changes in melting point and enthalpy of the antioxidant and polyethylene oxide (PEO). A compatible composition of PEO‐silica‐BHT (tert. butyl hydroxyl toluene) was used to produce a filler, which was pressed on the form of a fine powder between two polyamide‐6 films and subsequently sandwiched with further seven layers of fresh films. The multiple‐film stack was aged first in an air circulated oven at 60 °C for 360 days and then for further 475 days at ambient atmospheric conditions. The concentration of carbonyl groups in the aged films was monitored by ATR‐IR spectroscopy. A sigmoidal increase was found for the amount of new carbonyl groups formed, starting from the inside layer nearest to the source of antioxidant. This confirms that the antioxidant has diffused from the filler into the surrounding polymer matrix and has reduced the rate of evolution of carbonyl groups resulting from oxidative degradation reactions.
Dynamic‐mechanical Investigation of Melt Compounded Poly(butylenterephtalate)/organoclay Nanocomposites
Authors: Acierno Domenico , Amendola Eugenio , Russo Pietro 
Published: February 2007

AbstractNanocomposites constituted by neat or opportunely toughened polybuthylene terephtalate filled with a commercial organoclay (Somasif™MEE) were analysed to asses their potential use in the automotive field. In particular, hybrid systems including 3–6% by weight of MEE, in presence or not of a toughening agent such as an engineering thermoplastic elastomer (Pibiflex), and obtained by melt intercalation were considered. All materials were characterised in terms of dynamic‐ mechanical properties. Results clearly proved that the optimization of the formulation composition allows to achieve a considerable improvement of the ultimate damping performances.
In Situ Formation of a Uniform Distribution of Silver Nanoparticles in PVDF: Kinetics of Formation and Resulting Properties
Authors: Compton J. , Kranbuehl D. , Martin G. , Espuche E. , David L. 
Published: February 2007

AbstractHybrid organic/silver nanoparticle thermoplastic films have been prepared using a single step process where the silver nanoparticles were formed during a cure cycle applied to the film. Figure 1 is a TEM demonstrating the ability of our technique to produce silver nanoparticles in the semi‐crystalline polymer Poly(vinylidene fluoride) (PVDF). The current laboratory focus is on characterizing kinetics and particularly the diameter growth and inter‐particle distance as a function of time and temperature using the techniques of small‐angle X‐ray scattering (SAXS), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD). Using the Beaucage model, the SAXS data demonstrates that the particle size reaches equilibrium after approximately 70 minutes of curing at 240 °C. This result is also observed in the XRD results where the half width of the diffraction peaks becomes smaller quickly during the initial hour. In a parallel experiment using DSC, the exothermic heat flow increases rapidly during the first hour but does not reach completion until almost 150 minutes.
The Twist‐Bending Behavior of Forward Swept Wings: A Case Study of a Glass/Carbon Hybrid Composite Structure
Authors: Blasi L. , Caputo F. , D'Amore A. , Golia C. , Grassia L. , Iuspa L. , Scaramuzzino F. , Soprano A. 
Published: February 2007

AbstractThe behavior of the wing of an aircraft is characterized by the complex interaction among dynamic (distribution of the masses), elastic (ownership of the materials) and aerodynamic (shapes, forces and moments) phenomena. As a rule it is expected from us that the aerodynamic actions damp the oscillations (natural or forced) of the wing. However, above given speeds a lot of undesired aero‐elastic phenomena, among which the divergence of the wings, occur and became of considerable importance in view of safety. To potentially prevent dangerous situations, generally the speed of the aircraft is limited; a possible alternative is to endow the “system wing” of proper devices (passive or active, i.e. controls) in order to prevent that the energy transfer of aerodynamic actions amplifies its instability. The forward swept wings are extremely efficient in terms of aerodynamics performance (stall and supersonic behavior) and therefore of maneuverability of the aircraft, even if, unfortunately, they are extremely critic under the profile of the aero‐elastic stability. The solution of the technical‐scientific and technological problems associated with the use of innovative configurations of wings prefigures a meaningful breakthrough in the international aerospace sector. Within this work the authors aim to determine a particular configuration of composite material for the realization of a forward swept wing in such a way that, under the action of the effective aerodynamic loads, the wings structural response provides a coupled bending‐torsion deformations with stability effects. It will be shown that by using a recursive analysis of the composite lay‐up one can tailor the overall bending/torsion deformation ratio value.
Numerical Investigation of the Optimum Placement Locations of Optical Fiber Bragg Grating Sensors for the Health Monitoring of Bonded Composite Repairs
Authors: Tsamasphyros G. , Kanderakis G. N. , Vrettos C. , Kalkanis K. 
Published: February 2007

Abstractthe use of optical Fiber Bragg Grating sensors (FBG) embedded into composite laminates has proven to be an efficient way for the monitoring of the strain field inside composite laminates. The current work focuses on the use of such sensors for structural health monitoring of bonded composite repairs, often used in the aerospace as well as in the maritime industry. In such applications, the embedding location of the FBG sensors is of great importance, since apart from general strain measurements of the composite, they provide the ability of detecting whether a crack has propagated in the metal or a debonding has occurred between the metal and the composite. Within the current work, a representative case of bonded composite repair of a cracked metallic structure is examined and a series of 3D elasticity linear static finite element models are developed. Various crack lengths and patch disbond sizes have been studied while varying strain distributions were recorded along numerous paths inside the structure. Having recorded and analyzed these strain distributions, certain guidelines have been derived concerning the optimum FBG placement inside the patch, in order to ensure efficient structural health monitoring.
Morphology of Compatibilized Ternary Blends
Authors: de Freitas Cássia Alves , Valera Ticiane Sanches , Catelli de Souza Adriana Martinelli , Demarquette Nicole Raymonde 
Published: February 2007

AbstractIn this work, the evolution of the morphology of polypropylene/polystyrene/poly(methyl metacrylate) (PP/PS/PMMA) blends to which graft copolymers polypropylene‐graft‐polystyrene (PP‐g‐PS) of 2 compositions (55/45 and 70/30), polypropylene‐graft‐poly(methyl metacrylate) (PP‐g‐PMMA), or styrene‐block‐(ethylene‐ co‐butadiene)‐block‐styrene (SEBS) was added has been studied. The ternary blends morphologies were predicted using phenomenological models that predict the morphology of ternary blends as a function of the interfacial tension between the blend components (spreading coefficient and free energy minimization). All blends studied presented a core‐shell morphology with PS as shell and PMMA as core. The addition of PP‐g‐PS or SEBS resulted in a reduction of the size of the PS shell phase and, the addition of PP‐g‐PMMA did not seem to have any effect on the diameter of PMMA. The difference observed between the different morphologies relied on the number of droplets of core within the shell. All the phenomenological models predictions corroborated the experimental results, except when PP‐g‐PMMA was added to the blend.
Essential Work of Fracture of photo‐oxidized LDPE/EVA Films
Authors: Fasce L. , Chiaverano G. , Lach R. , Frontini P. 
Published: February 2007

AbstractThe Essential Work of Fracture approach (EWF) was used to determine how UV‐C irradiation alters the fracture behaviour of LDPE/EVA films. Complementary characterization was performed by FTIR, DSC, TOM, and uniaxial tensile testing. The crosslinking reactions that govern photo‐oxidation process at initial stage of exposure stiffened the amorphous phase of the polymer, leading to films with enhanced elastic modulus, yield stress and ultimate strength, but impaired strain at break. In the fracture experiments carried out on films irradiated within 0 and 5 days, EWF methodology requirements were met and the corresponding fracture toughness parameters (we and βwp ) turned out to be sensitive to UV‐C irradiation. Longer irradiation time triggered the development of microcracks, which not allowed further stable crack growth and invalidated the application of EWF approach.
Spectromechanical Properties of Polymeric Gel Electrolytes and Blends
Authors: Nicotera I. , Coppola L. , Oliviero C. , Ranieri G. A. 
Published: February 2007

AbstractIn this paper we studied the spectro‐mechanical properties of polymer gel electrolytes and blends by means of shear rheology. These electrolytes were obtained by immobilizing EC/PC/LiClO4 solutions in a polymeric matrix of PEO, PAN and PMMA, respectively. Two structural and thermoreversible transitions, a strong‐to‐weak gel and a gel‐to‐sol, were revealed and discussed. Moreover, PMMA‐PVdF blends have been studied as a function of the different polymeric ratios in order to obtain the best compromise between ionic conduction and mechanical properties. Interesting mechanical properties were observed at some intermediate blend compositions.
Smart hydrogels for Novel Optical Functions
Authors: Dispenza Clelia , Leone Maurizio , Lo Presti Caterina , Librizzi Fabio , Vetri Valeria , Spadaro Giuseppe 
Published: February 2007

AbstractNanocomposites of inherently conductive polyaniline (PANI) within a highly hydrophilic polyvinyl alcohol (PVA) based hydrogel have been produced by coupling a conventional dispersion chemical oxidative polymerization to a subsequent high energy irradiation step, in order to convert the polymer stabilizing the aqueous dispersion, namely the PVA, into a highly water swollen hydrogel incorporating the PANI particles. The incorporation of the electroactive and “pH‐sensitive” polymer into a transparent and highly permeable hydrogel matrix has been pursued as a route to the development of a novel class of potentially biocompatible, smart hydrogels that can respond to changes of the surrounding environment with measurable changes in their optical properties. Absorption spectra show that the optical absorption bands typical of PANI, known to be reversibly affected by changes of the polymer oxidation state or pH or both, are well preserved in the PVA hydrogels. Even more interestingly, fluorescence is observed from the nanoparticles of PANI in its inherently conductive form, whose intensity is strongly affected by changes of pH. This has enhanced the importance of this material to a large extent from both a scientific and a practical point of view.
Synthesis of Biodegradable Polycaprolactone/Montmorillonite Nanocomposites by Direct In‐situ Polymerization Catalysed by Exchanged Clay
Authors: Harrane A. , Belbachir M. 
Published: February 2007

AbstractPoly (e‐caprolactone) (PCL) layered silicate nanocomposites have the advantage adding biocompatibility and biodegradability to the traditional properties of nanocomposites. They can be prepared by in situ ring‐opening polymerization of e‐caprolactone using conventional initiator to induce polymerization in the presence of an organophilic clay, such as organomodified montmorillonite. In this work, we have used an alternative method to prepare poly(e‐caproilactone)/montmorillonite nanocomposites. The cationic polymerization of e ‐caprolactone was initiated directly by Maghnite‐TOA, organomodified montmorillonite clay, to produce nanocomposites. Resulted nanocomposites were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), force atomic microscopy (AFM) and thermogravimetry. The evolution of mechanical properties was also studied.Corrected by:Correction: Synthesis of Biodegradable Polycaprolactone/Montmorillonite Nanocomposites by Direct In‐situ Polymerization Catalysed by Exchanged ClayVol. 247, Issue 1, page n/a, Article first publshed online: 1 AUG 20111; DOI 10.1002/masy.200750150
Synthesis of New Methylsiloxane Oligomers with Pendant Trialkoxysilylethyl Groups for Preparation of Silicon hard Coatings
Authors: Mukbaniani O. , Zaikov G. E. , Tatrishvili T. , Titvinidze G. , Phatsatsia S. 
Published: February 2007

AbstractFor the purpose to prepare precursor materials for the silicon hard coatings, the hydrosilylation reactions of α, ω–bis(trimethylsiloxy)methylhydridesiloxane to trialkoxyvinylsilanes in the presence of platinum hydrochloric acid (0.1 M solution in THF), Karstedt's catalyst (Pt2[(VinSiMe2)2O]3) and platinum on the carbon (5%) were investigated. Hydrosilylation reactions at different ratios of initial compounds and at various temperatures (40–60 °C) were investigated and methylsiloxane oligomers with pendant trialkoxy fragments have been obtained. It was shown that completely hydrosilylation of all active SiH groups do not take place. The hydrosilylation reaction order, activation energy and rate constants were determined. The synthesized oligomers were characterized by 1H, 13C NMR and FTIR spectra data. Gel‐permeation chromatography, differential scanning calorimetric, thermogravimetric and wide‐angle X‐ray investigations of synthesized oligomers were carried out. Synthesized oligomers together with tetraethoxysilane were used for preparation of silicon hard coatings via sol‐gel processes.