bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chain extension and degradation during reactive processing of PET in the presence of triphenyl phosphite
Authors: Cavalcanti F.N. , Teófilo E.T. , Rabello M.S. , Silva S.M.L. 
Published: November 2007

AbstractPoly(ethylene terephthalate) (PET) is chemically degraded during processing and/or using by a number of sources including temperature, humidity, and ultraviolet radiation. As a consequence, a large loss in engineering properties is observed when PET products are recycled. To overcome this problem, various types of chain extenders were developed in an attempt to recover the polymer molecular sizes by chemical reactions during processing. This work investigates the use of triphenyl phosphite (TPP) as a chain extender of virgin and recycled PET. Compounds with 1 and 3% of TPP were prepared and processed under various conditions using a torque rheometer. An increase in torque during mixing was associated with chain extension reactions whereas the observed decrease in torque afterwards was due to chemical degradation. The optimum processing conditions were reached (260°C, 1% chain extender), with a maximum in chain extension and a minimum in subsequent degradation. An important finding of this work was that the chemical degradation of chain extended PET occurs very easily during storage and it was considered to be a result of the influence of by‐products of TPP reaction with PET. The extraction of these products with acetone was shown to be quite effective, with a considerable stability during storage. This work also showed that the recycled PET is much less able to react with TPP in comparison with the virgin polymer. POLYM. ENG. SCI., 47:2155–2163, 2007. © 2007 Society of Plastics Engineers
Ultraporous 3D polymer meshes by low‐temperature electrospinning: Use of ice crystals as a removable void template
Authors: Simonet Marc , Schneider Oliver D. , Neuenschwander Peter , Stark Wendelin J. 
Published: November 2007

AbstractWhile electrospinning provides an excellent preparation method for the manufacturing of polymer fibers with defined diameter, controlling the overall porosity of the resulting fiber assemblies has remained elusive, particularly at higher porosities. In this study, the use of a low‐temperature fiber collection device in air with controlled humidity allowed the simultaneous deposition of polymer fibers and ice particles from condensing humidity. The ice particles were intimately embedded within the polymer fibers and served as a pore template thus defining the mesh porosity after drying of the collected fiber assemblies. The amount of water condensation therefore contributes to the control of the mean interfiber distance and the resulting porosity. This simple and well accessible use of ice crystals as void templates gives access to the preparation of biodegradable tissue engineering scaffolds with an up to four times higher porosity if compared to conventional fiber electrospinning. The successful application of low‐temperature electrospinning using polyesters or polyurethanes suggests a broad, material independent applicability of the process for the preparation of highly porous polymer structures. POLYM. ENG. SCI., 47:2020–2026, 2007. © 2007 Society of Plastics Engineers
Study on epoxy/thermoplastic blends based on the addition of a novel aromatic block copolymer
Authors: Cicala Gianluca , Mamo Antonino , Recca Giuseppe , Restuccia Carmelo Luca 
Published: November 2007

AbstractIn this article we present a study of the properties of some epoxy/thermoplastic blends based on the addition of a novel block copolymer of an ABA type. The block A was a commercial poly(2,6‐dimethyl‐1,4‐phenylene ether or oxide) (PPE or PPO) while block B was a random copolyethersulphone synthesized in our laboratory. The comparison with the epoxy blends modified only with the homopolymers A or B is also reported. The homopolymers were also mixed via solution blending and the resulting physical mixture was used as modifier for comparison purposes. The blends have been thoroughly characterized by parallel plate rheometry, dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy. Upon curing, the epoxy blends containing the physical mixture underwent phase separation showing a morphology which resembled the combination of those found for the blends modified with each of the homopolymers. On the contrary, the addition of the block copolymer resulted in a unique morphology. The viscoelastic properties of the blends both in the unreacted and cured state varied significantly when the block copolymer was added rather than the homopolymers or their physical mixture. POLYM. ENG. SCI., 47:2027–2033, 2007. © 2007 Society of Plastics Engineers
The effect of epoxy‐polyester hybrid resin on mechanical properties, rheological behavior, and water absorption of polypropylene wood flour composites
Authors: Jahani Yousef 
Published: November 2007

AbstractThe effect of epoxy resin on mechanical and Rheological properties, and moisture absorption of wood flour polypropylene composites (WPCs) were investigated. The reactive mixing of epoxy resin with 30, and 40 wt% wood flour and polypropylene (PP) was carried out in twin screw extruder with a special screw elements arrangement. PP grafted maleic anhydrides (MPP) were used as coupling agent to improve the interfacial interactions of wood flour, epoxy resin, and PP. The tensile strength of composites decreased, and elastic modulus and moisture absorption increased with increasing epoxy resin content. The complex viscosity η* increased with increasing epoxy resin content of composites, and a synergistic effect in increasing the η* was observed at 3 wt% resin. The epoxy resin modified wood‐PP composites that chemically coupled by MPP showed minimum water absorption with highest elastic modulus. The experimental oscillation rheologyical data were used to drive a model to predict the flow behavior of WPCs, in a wide range of frequencies. POLYM. ENG. SCI., 47:2041–2048, 2007. © 2007 Society of Plastics Engineers
Transport characteristics of carboxylic acids based chain extended PU membranes with n‐alkane penetrants
Authors: Siddaramaiah  , Manjula K.S. 
Published: November 2007

AbstractCastor oil based chain extended polyurethanes (PUs) have been prepared using citric acid and maleic acid as chain extenders. Molecular transport of n‐alkanes into prepared carboxylic acid chain extended PUs has been studied at different temperatures, viz., 25, 40, and 60°C using a gravimetric sorption method. The sorption (S), the diffusion (D), and the permeation (P) coefficients for n‐alkane penetrants have been calculated. Transport data are affected by the nature of the interacting solvent molecules, molar volume, solubility parameters, temperature, and the structural variation of the chain extended PUs. The temperature dependence of the transport coefficient has been used to estimate the kinetic parameters for the processes of diffusion (ED) and permeation (EP) from the Arrhenius plots. The van't Hoff relation was used to obtain enthalpy (ΔH) and entropy (ΔS) of sorption process. POLYM. ENG. SCI., 47:2057–2064, 2007. © 2007 Society of Plastics Engineers
Through‐thickness embossing process for fabrication of three‐dimensional thermoplastic parts
Authors: Nagarajan Pratapkumar , Yao Donggang , Ellis Thomas S. , Azadegan Reza 
Published: November 2007

AbstractThe standard embossing process is limited to the fabrication of surface structures on relatively large polymer substrates. To overcome this limitation, a hybrid punching and embossing process was investigated for through‐thickness embossing of three‐dimensional parts. The embossing tool included a punching head and to‐be‐ replicated features in the socket behind the punching head. The built‐in punching head facilitated a through‐thickness action and provided a closed‐die environment for embossing pressure buildup. The method was used to emboss multichannel millimeter waveguides which requires uniform edges and accurate dimensions. With a tool temperature of 140°C, an embossing time of 3 min and a total cycle time of 7 min, discrete 4‐channel waveguides were successfully embossed from a room‐temperature ABS substrate. A computer model was established to study the flow behavior during through‐thickness embossing. It was found that nonisothermal embossing conditions help confine the polymer in the cavity and reduce the outflow into the surrounding region, thus achieving complete fill of the cavity. POLYM. ENG. SCI., 47:2075–2084, 2007. © 2007 Society of Plastics Engineers
Modeling of dynamic mechanical properties of vulcanized fluoroelastomer
Authors: Likozar Blaž , Šebenik Urška , Krajnc Matjaž 
Published: November 2007

AbstractThe dynamic mechanical properties of a vulcanized fluoroelastomer (FKM) were studied over a range of temperatures and shear frequencies. Dynamic mechanical analysis and differential scanning calorimetry were used for the purpose of the study. A model was developed in order to describe FKM's viscoelastic behavior at various temperatures. The model was fitted to experimental data using an algorithm, which was developed for this purpose. As a result the FKM discrete relaxation spectrum at two reference temperatures was obtained, as well as the Williams‐Landel‐Ferry (WLF) equation parameters or the activation energy equivalent. Further on, the model was applied on storage modulus and loss tangent values obtained from the experiments, during which the temperature increased linearly. It was observed that the WLF equation fits well with the results during the glass transition, while the Arrhenius‐type relationship predicted too rapid decrease of the storage modulus during the glass transition. The master curves were constructed using the previously calculated WLF parameters and the activation energy equivalent. The developed model may be readily applied for the prediction of the numerous FKM compounds' frequency–temperature behavior using the dynamic mechanical properties obtained from either isothermal or low linear heating rate program measurements. POLYM. ENG. SCI., 47:2085–2094, 2007. © 2007 Society of Plastics Engineers
Preparation and characterization of bis‐ortho‐diynylarene (BODA)‐derived submicrogratings
Authors: Zengin Huseyin , Zengin Gulay , Zhou Wensheng , Topping Chris M. , Smith Dennis W. , Foulger Stephen H. 
Published: November 2007

AbstractThe objective of this study was to illustrate how submicrogratings can be prepared from bis‐ortho‐diynylarene (BODA)‐derived polymers. BODA monomers undergo thermal step‐growth polymerization and careful control of this conversion, with respect to molecular weight and viscosity, can be used to produce reactive, processable branched polyarlyene intermediates. “Soft‐lithography” techniques were used to prepare submicrogratings from these intermediates, which were subsequently stabilized by further polymerization. The surface morphology and dimensions of the submicrogratings were examined using scanning electron microscopy techniques and crystallinity was studied. Reflectivity data was also obtained from linear submicrogratings. These BODA‐derived microstructures can be carbonized at 1000°C, or above, to obtain carbonized microstructures with potential for application in optical and electronic microdevices. POLYM. ENG. SCI., 47:2095–2099, 2007. © 2007 Society of Plastics Engineers
Influence of screw profile and extrusion conditions on the microstructure of polypropylene/organoclay nanocomposites
Authors: Lertwimolnun W. , Vergnes B. 
Published: November 2007

AbstractDirect melt mixing in a twin screw extruder is a simple and classical technique for preparing nanocomposites by dispersing organoclay in a thermoplastic matrix. In this paper, we focus on organoclay/polypropylene nanocomposites, using maleated polypropylene as compatibilizer. The objective of the work is to characterize the influence of screw profile and processing conditions on the microstructure of the nanocomposite (intercalation and exfoliation). Different screw profiles, more or less severe in terms of mixing elements, have been investigated. For each profile, different processing conditions (feed rate, screw speed) have been tested. Samples were collected both at die exit and all along the screw profiles and analyzed (X‐ray diffraction and rheometry). Numerical simulations have been performed to quantify the thermomechanical treatment experienced by the material inside the extruder. For all profiles and operating conditions, a mixed intercalated/exfoliated structure has been observed. Exfoliation increases linearly with the ratio of screw speed to feed rate, but is more important for the less severe profile. Except at low feed rate, intercalation and exfoliation do not change a lot along the screw profile. In many cases, the final microstructure is already obtained after the melting zone of the extruder. POLYM. ENG. SCI., 47:2100–2109, 2007. © 2007 Society of Plastics Engineers
Stress–strain behavior as related to surface topography and thickness uniformity in uni‐ and biaxially stretched PVDF/PMMA blends
Authors: Zhou Xixian , Cakmak M. 
Published: November 2007

AbstractThe influence of blend composition and processing conditions on the surface roughness and thickness uniformity of PVDF/PMMA blends were investigated in uniaxial and biaxial deformation mode for PVDV and PVDF/PMMA blends 70/30, 55/45, and 40/60 wt%. The addition of PMMA retards the thermal crystallizability of the blends and this allows rapid solidification into films with little or no crystallinities. Such precursors with lowered crystallinity were found to be easily uni‐ and biaxially stretched into uniform and transparent films in the temperature range between the glass transition temperature and cold crystallization temperature where they exhibit strain hardening. Thus, these blends are suitable for processes such as tenter frame biaxial stretching, double bubble film blowing, and stretch blow molding where they will exhibit good transparency and thickness uniformity. POLYM. ENG. SCI., 47:2110–2117, 2007. © 2007 Society of Plastics Engineers
Nitroxide‐mediated controlled degradation of polypropylene
Authors: Psarreas Alexandros , Tzoganakis Costas , McManus Neil , Penlidis Alexander 
Published: November 2007

AbstractThe purpose of this work is to evaluate a new polypropylene (PP)‐based nitroxyl radical generator (NOR) and offer comparisons with a commonly used peroxide in the production of controlled‐rheology polypropylene (CRPP) resins. CRPP resins are produced by reactive processing in a batch mixer by using different amounts of either the NOR or a peroxide initiator at different temperatures. Molecular weight and rheological properties are determined for all CRPP produced and a comparison between the effectiveness of the NOR and the peroxide initiator is provided. POLYM. ENG. SCI., 47:2118–2123, 2007. © 2007 Society of Plastics Engineers
Nonisothermal finite‐element analysis of thermoforming of polyethylene terephthalate sheet: Incomplete effect of the forming stage
Authors: Erchiqui F. , Souli M. , Yedder R. Ben 
Published: November 2007

AbstractIn this work, we consider a nonisothermal finite‐element analysis approach using an explicit dynamic procedure for the forming of a polyethylene terephthalate (PET) sheet subjected to air‐flow loading. The dynamic pressure load is thus deduced from the van der Waals equation of state. The effect of the radiative‐conduction heat transfer during the reheating stage, the stress‐deformation behavior during the incomplete forming stage, and the solidification during the cooling stage are simulated. The viscohyperelastic behavior of the Christensen–Yang‐like model is considered. The Lagrangian formulation, together with the assumption of the membrane shell theory, is used. The viscohyperelastic model is validated with the equibiaxial stretching tests. Also, temperature validation is performed by comparing the computed, the theoretical, and the experimental temperature profiles obtained from measuring the inside and outside PET sheet surface. An example of thermoforming a PET part is presented. In this example, the influence of the air‐flow on the thickness and the stress distribution is presented. POLYM. ENG. SCI., 47:2129–2144, 2007. © 2007 Society of Plastics Engineers
Effects of interfacial morphology on the welding strength of injection‐molded polyamide
Authors: Qiu Jianhui , Tsuboi Atsushi , Izumi Kazuo , Wu Hong , Guo Shaoyun , Huang Yudong 
Published: November 2007

AbstractThe effect of interfacial morphology controlled by injection‐molding conditions on the welding strength of injection‐molded polyamide was investigated in this article. The experimental results showed that the first injection‐molding conditions had distinct influence on the welding strength at the low secondary injection‐molding temperature T2 (≤265°C), but the influence vanishes at T2 ≥ 285°C. On the other hand, no matter what the first injection‐molding conditions are, the welding strength increases with increasing T2, and when T2 ≥ 285°C, the highest welding strength reaches 45 MPa, due to the formation of trans‐crystals at the interface. Morphology studies showed that trans‐crystals grow along the perpendicular direction of the interface, and their nuclei are formed at the surface of the first injection‐molded specimens. For the specimens with high‐welding strength, the welding strength relies on the skin layer of the first injection‐molded specimens in which the fracture induced by shear stress happens. POLYM. ENG. SCI., 47:2164–2171, 2007. © 2007 Society of Plastics Engineers
Liver proteome analysis of adaptive response in rat immediately after partial hepatectomy
Authors: Sun Yanwei , Deng Xinyu , Li Wenrui , Yan Yujuan , Wei Handong , Jiang Ying , He Fuchu 
Published: November 2007

AbstractThe extraordinary ability of the liver to regenerate after resection continues to be an important fascination to mammalian liver researchers. However, at present, there are still several central questions regarding the process of liver regeneration that are not clear. In our study, we try to clarify how the liver is able to maintain its functions as well as to initiate liver regeneration after a significant loss of two‐thirds. Here differentially expressed proteins in rat livers at 1 h after partial hepatectomy (PHx) and sham operation were analyzed using 2‐DE combined with MALDI‐TOF/TOF MS. After the analysis, 24 significantly changed spots (ratio≥2, p<0.05) were identified. Those proteins are involved in important liver functions such as metabolism, detoxification, and inflammation. Based on the changes in the protein levels found in our data, we identified two aspects of remnant liver immediately after PHx, which focused on the hepatic adaptation and the inflammatory response associated with the initiation of liver regeneration after PHx. For the first time, the differential expression of pyruvate dehydrogenase complex (PDHX), paraoxonase 1 (PON1), thyroid hormone receptor β, GAP43 (where GAP stands for growth‐associated protein), and interleukin‐2 (IL2), after PHx, were validated by Western blot.
Analysis of DIGE data using a linear mixed model allowing for protein‐specific dye effects
Authors: Krogh Morten , Liu Yingchun , Waldemarson Sofia , Valastro Barbara , James Peter 
Published: November 2007

AbstractDifferential in‐gel electrophoresis (DIGE) experiments allow three protein samples to be run per gel. The three samples are labeled with the spectrally resolvable fluorescent dyes, Cy2, Cy3, and Cy5, respectively. Here, we show that protein‐specific dye effects exist, and we present a linear mixed model for analysis of DIGE data which takes dye effects into account. A Java implementation of the model, called DIGEanalyzer, is freely available at http://bioinfo.thep.lu.se/digeanalyzer.html. Three DIGE experiments from our laboratory, with 173, 64, and 24 gels, respectively, were used to quantify and verify the dye effects. DeCyder 5.0 and 6.5 were used for spot detection and matching. The fractions of proteins with a statistically significant (0.001 level) dye effect were 19, 34, and 23%, respectively. The fractions of proteins with a dye effect above 1.4‐fold change were 1, 4, and 6%, respectively. The median magnitude of the dye effect was 1.07‐fold change for Cy5 versus Cy3 and 1.16‐fold change for Cy3 versus Cy2. The maximal dye effect was a seven‐fold change. The dye effects of spots corresponding to the same protein tend to be similar within each of the three experiments, and to a smaller degree across experiments.
Quantitative proteomics of intracellular Porphyromonas gingivalis
Authors: Xia Qiangwei , Wang Tiansong , Taub Fred , Park Yoonsuk , Capestany Cindy A. , Lamont Richard J. , Hackett Murray 
Published: November 2007

AbstractWhole‐cell quantitative proteomic analyses were conducted to investigate the change from an extracellular to intracellular lifestyle for Porphyromonas gingivalis, a Gram‐negative intracellular pathogen associated with periodontal disease. Global protein abundance data for P. gingivalis strain ATCC 33277 internalized for 18 h within human gingival epithelial cells and controls exposed to gingival cell culture medium were obtained at sufficient coverage to provide strong evidence that these changes are profound. A total of 385 proteins were overexpressed in internalized P. gingivalis relative to controls; 240 proteins were shown to be underexpressed. This represented in total about 28% of the protein encoding ORFs annotated for this organism, and slightly less than half of the proteins that were observed experimentally. Production of several proteases, including the classical virulence factors RgpA, RgpB, and Kgp, was decreased. A separate validation study was carried out in which a 16‐fold dilution of the P. gingivalis proteome was compared to the undiluted sample in order to assess the quantitative false negative rate (all ratios truly alternative). Truly null (no change) abundance ratios from technical replicates were used to assess the rate of quantitative false positives over the entire proteome. A global comparison between the direction of abundance change observed and previously published bioinformatic gene pair predictions for P. gingivalis will assist with future studies of P. gingivalis gene regulation and operon prediction.
Synthesis and characterization of arborescent (hyperbranched) polyisobutylenes from the 4‐(1,2‐oxirane‐isopropyl)styrene inimer
Authors: Foreman Elizabeth A. , Puskas Judit E. , Kaszas Gabor 
Published: November 2007

AbstractThe synthesis of the novel inimer (initiator‐monomer) 4‐(1,2‐oxirane‐isopropyl)styrene EPOIM and the copolymerization of this inimer with isobutylene (IB) to form arborescent polyisobutylene (PIB) is described. Polymerizations were accomplished by use of TiCl4 coinitiator and the effect of reaction conditions was investigated. Size exclusion chromatography (SEC) was used demonstrate EPOIM incorporation across the whole molecular weight distribution. The average number of branch points (B) per chain measured by use of selective link destruction increased with increasing EPOIM/IB ratio and decreased with [TiCl4]. Large scale polymerizations were carried out based on results from small scale polymerizations. Architecture analysis carried out through use of branching parameters based on the radii of gyration Rg and hydrodynamic radii Rh measured by multidetector SEC corroborated the proposed arborescent architecture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5847–5856, 2007