bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and properties of fluorinated bis‐benzocyclobutene‐terminated arylene ether monomers
Authors: Zuo Xiaobiao , Zhao Xiaojuan , Liu Biao , Yang Shiyong , Fan Lin 
Published: February 2009

AbstractFour novel bis‐benzocyclobutene‐endcapped arylene ether monomers, 1,1′‐bis[4‐(4′‐benzocyclobutenyloxy)phenyl]‐1‐phenyl‐2,2,2‐trifluoroethane (BOPP3FE), 1,1′‐bis[4‐(4′‐benzocyclobutenyloxy)phenyl]‐1‐(3′,5′‐ditrifluoromethyl)phenyl‐2,2,2‐trifluoroethane(BOPP9FE), 2,2′‐bis[4‐(4′‐benzocyclobutenyloxy)phenyl]‐1,1,1,3,3,3‐hexfluoropropane (BOP6FP), and 2,2′‐bis[4‐(4′‐benzocyclobutenyloxy)phenyl]‐propane (BOPP) were prepared and characterized. All the four monomers showed similar curing behaviors under N2 (Differential scanning calorimetry: extrapolated onset and peak temperatures at 225–229°C and 261–263°C) and demonstrated low and steady melt viscosities between 110 and 200°C, indicating their good processability. After cure, the resulting BCB resins exhibited high Tg (232–282°C) and excellent thermal stability (T5% > 433°C). The resins also showed good mechanical properties with the flexural strengths of 68–88 MPa and the flexural modulus of 2.52–3.15 GPa. Moreover, the resins also exhibited low dielectric constants (2.58–2.88), low dissipation factors (2.7 to 8.4 × 10−4) and low water absorptions in boiling water for 24 h (0.29–0.59%). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and properties of nanocomposites based on different polarities of nitrile–butadiene rubber with clay
Authors: Liang Yu‐Rong , Cao Wei‐Liang , Zhang Xiao‐Bin , Tan Ying‐Jie , He Shao‐Jian , Zhang Li‐Qun 
Published: February 2009

AbstractNanocomposites were prepared with different grades of nitrile–butadiene rubber (NBR) [with nitrile (CN) contents of 26, 35, and 42%] with organoclay (OC) by a melt‐compounding process. The rubber/clay nanocomposites were examined by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). An increase in the polarity of NBR affected the XRD results significantly. The dispersion level of the nanofiller in the nanocomposites was determined by a function of the polarity of the rubber, the structure of the clay, and their mutual interaction. The intercalated structure and unintercalated structure coexisted in the lower polar of NBR. In addition, a relatively uniformly dispersed state corresponded to a more intercalated structure, which existed in the higher polar of NBR matrix. Furthermore, high‐pressure vulcanization changed the extent of intercalation. The mechanical properties and gas barrier properties were studied for all of the compositions. As a result, an improvement in the mechanical properties was observed along with the higher polarity of NBR. This improvement was attributed to a strong interaction of hydrogen bonding between the CN of NBR and the OH of the clay. Changes in the gas barrier properties, together with changes in the polarity of the rubbers, were explained with the help of the XRD and TEM results. The higher the CN content of the rubber was, the more easily the OC approached to the nanoscale, and the higher the gas barrier properties were. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effect of an allyl pretreatment of starch on the grafting efficiency and properties of allyl starch‐g‐poly(acrylic acid)
Authors: Zhu Zhifeng , Li Manli , Jin Enqi 
Published: February 2009

AbstractStarch was pretreated with allyl etherification to enhance the grafting efficiency of the copolymerization of granular starch with acrylic acid and to improve the properties of starch‐g‐poly(acrylic acid) used as a warp sizing agent. The graft copolymerization was carried out in an aqueous dispersion with ferrous ammonium sulfate and hydrogen peroxide as initiators. Through the introduction of allyl groups into starch before the copolymerization, the grafting efficiency could evidently be enhanced, and properties such as fiber adhesion and film behaviors of the copolymer were improved. The pretreatment was capable of enhancing the grafting efficiency by about 10–20% when the degree of substitution of allyl starch ranged from 0.011 to 0.037. The adhesion and film behaviors also depended on the modification extent of the starch pretreatment and on the grafting ratio of the copolymer. The adhesion reached a maximum at a degree of substitution of 0.025, and the film behaviors were best when the degree of substitution ranged from 0.011 to 0.025. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Guided tissue regeneration with use of β‐TCP/chitosan composite membrane
Authors: Kuo Shyh Ming , Chang Shwu Jen , Cheng‐Chie Niu Gregory , Lan Cheng‐Wen , Cheng Wen Tai , Yang Chen Zen 
Published: February 2009

AbstractGuided tissue regeneration (GTR) membranes with bioabsorbable characteristics have been employed, in recent years, for periodontal procedures to deflect the growth of gingival tissues away from root surface. They provide an isolated space over regions with defective tissues and allow the relatively slow growing periodontal ligament fibroblasts to be repopulated over the root surface. In this study, we have employed chitosan and tricalcium phosphate (β‐TCP) as viable membrane materials and evaluated their roles in GTR applications. Three types of β‐TCP/chitosan membranes, weight ratio of β‐TCP/chitosan 65 : 35, 33 : 67, and 10 : 90, were prepared for three categories: the mechanical strength to create an effective space; the rapid rate to reach hydrolytic equilibrium in phosphate buffer solution; and the ease of clinical manipulations. Consequently, standardized, transosseous, and critical‐sized (cavity of 8 mm) skull defects were made in adult rabbits, and the defective regions were covered with the specifically prepared chitosan membranes. After 4 weeks of recovering, varying degrees of bone healing were observed beneath the β‐TCP/chitosan membranes in comparison to the control group. The β‐TCP/chitosan membranes covered regions showed a clear boundary space between connective tissues and bony tissues. Over all, good cell‐occlusion and beneficial osteogensis effects by these bioabsorbable materials toward the wound recovery were indicated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Plasticized properties of poly (lactic acid) and triacetine blends
Authors: Yeh Jen‐taut , Huang Chi‐yuan , Chai Wan‐lan , Chen Kan‐nan 
Published: February 2009

AbstractSystematically investigations of the plasticizing effects of triacetine (TAc) on crystallization, chain mobility, microstructure, and tensile properties of the Poly (lactic acid)/triacetine (PLA/TAc) blends are reported. A new transition hump was observed on the tan δ curve of PLAxTAcy specimens at temperatures ranging from −80 to −20°C. Thermal, wide angle X‐ray diffraction (WAXD) and dynamic mechanical analysis properties of PLA and PLAxTAcy series specimens suggest that PLA and PLAxTAcy series specimens can hardly crystallize by cooling the melt in room temperature. However, significant recrystallization of α form PLA crystals was found during the annealing processes of PLAxTAcy series specimens. Some “less perfect” β form PLA crystals were found as the TAc contents of PLAxTAcy specimens reach 30 wt %. Further morphological analysis show that the inherent brittle deformation behavior of the PLA specimen was successfully transformed into relatively ductile fracture behavior after blending sufficient but optimum amounts of TAc in PLA resins. Possible reasons accounting for this interesting recrystallization, thermal, microstructure and tensile properties of PLAxTAcy specimens are proposed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effect of clay dispersion on the rheological properties and flammability of polyurethane‐clay nanocomposite elastomers
Authors: Berta M. , Saiani A. , Lindsay C. , Gunaratne R. 
Published: February 2009

AbstractPolyurethane‐clay nanocomposite elastomers were synthesized using polyol‐clay blends with different levels of dispersion, which affected the final elastomer microstructure. A PU‐clay microcomposite elastomer containing partially dispersed clay showed poorer mechanical and similar fire properties to the unmodified polyurethane. More complete dispersion of the clay into the polyol led to an exfoliated structure in the final elastomer. This showed a higher modulus and kept a viscoelastic behavior to higher temperature than the pristine PU. The enhancement of mechanical and thermal properties in the nanocomposite elastomer can be attributed to the degree of clay exfoliation, and this also prevented dripping during the UL 94 fire test. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Cure kinetics of ternary blends of epoxy resins studied by nonisothermal DSC data
Authors: Tripathi Garima , Srivastava Deepak 
Published: February 2009

AbstractThe curing kinetics of blends of diglycidyl ether of bisphenol A (DGEBA), cycloaliphatic epoxy resins, and carboxyl‐terminated butadiene‐acrylonitrile random copolymer (CTBN) in presence of 4,4′‐diamino diphenyl sulfone (DDS) as the curing agent was studied by nonisothermal differential scanning calorimetry (DSC) technique at different heating rates. The kinetic parameters of the curing process were determined by isoconversional method given by Malek for the kinetic analysis of the data obtained by the thermal treatment. A two‐parameter (m, n) autocatalytic model (Sestak‐Berggren equation) was found to be the most adequate selected to describe the cure kinetics of the studied epoxy resins. The values of Ea were found to be 88.6 kJ mol−1 and 61.6 kJ mol−1, respectively, for the studied two sample series. Nonisothermal DSC curves obtained using the experimental data show a good agreement with that theoretically calculated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Effects of microcrystallinity and morphology on physical aging and its associated effects on tensile mechanical and environmental stress cracking properties of poly(ethylene terephthalate)
Authors: Zhou Hongxia , Lofgren Elizabeth A. , Jabarin Saleh A. 
Published: February 2009

AbstractPoly(ethylene terephthalate) samples with volume fraction levels of crystallinity up to 27% have been evaluated in terms of physical aging, tensile mechanical properties, and environmental stress cracking failures. Specific enthalpy recovery values were found to correspond with transitions from ductile to brittle modes of tensile mechanical failures, exhibited by samples with each level of crystallinity. For samples exposed to aging temperatures from 45 to 60°C, these critical enthalpies decrease linearly with increased crystallinity. The environmental stress cracking behavior of semicrystalline PET was found to depend on both crystallinity levels and physical aging. Samples with higher levels of crystallinity undergo stress cracking failures at lower critical stresses than their less crystalline counterparts. Physical aging, before environmental stress cracking exposure, further decreases these critical stress values and leads to much shorter critical times for failures. It has been shown that the interspherulitic amorphous portion of the material is primarily responsible for the differences in tensile mechanical and environmental stress cracking behaviors, observed as a result of aging and exposure. This amorphous region becomes progressively more restricted with increasing crystallinity as well as with increased aging. It, therefore, requires shorter exposure times to exhibit brittle tensile mechanical failure and environmental stress cracking rupture. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Side‐chain free aromatic polyimides containing anthracene units via Diels‐Alder precursors
Authors: Shah Saral , Tian Ruhai , Shi Zheng , Liao Yi 
Published: February 2009

AbstractSide‐chain free aromatic polyimides are expected to possess extraordinary mechanical properties and stability because of strong primary and secondary bonding forces. However, their low solubility makes it difficult to characterize, process, and obtain high molecular weight polymers. We have prepared highly stable thin films of side‐chain free aromatic polyimides from soluble Diels–Alder (DA) precursors. Heating the films of the precursors above 215°C induced retro‐DA reaction, which converted the precursors to the fully aromatic polyimides. The solid‐state retro‐DA reactions were monitored by attenuated total reflection Fourier transformed infrared (ATR‐FTIR) and UV‐Vis spectrometry. A critical issue for utilizing precursor chemistry in polymer synthesis is that it may result in porous and/or deformed materials. In this work, profilometry and atomic force microscope (AFM) were applied to study the surface and volume change. Our results showed that smooth and pin‐hole free films were obtained after the thermal treatment, while the volume decreased with a percentage close to the weight loss caused by the retro‐DA reaction. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Miscibility enhancement of PP/PBT blends with a side‐chain liquid crystalline ionomer
Authors: Sun Qiu‐ju , Zhang Bao‐Yan , Yao Dan‐Shu , Yu Li , Jiang Zhong‐Li 
Published: February 2009

AbstractSide‐chain liquid crystalline ionomer (SLCI) containing sulfonic acid groups with a polymethylhydrosiloxane main‐chain was used in the blends of polypropylene (PP) and polybutylene terephthalate (PBT) as a compatibilizer. The crystalline behavior, morphological, and mechanical properties of the blends were investigated in detail by differential scanning calorimetry (DSC), polarizing optical microscope (POM), Fourier transforms infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Revealed by the shift of Tm in DSC thermogram and the shift of the absorbed peak in FTIR spectra, specific interaction led to stronger interfacial adhesion between these phases, which resulted in much finer dispersion of the minor PBT phase in PP matrix. The SLCI containing sulfonate acid groups acted as physical crosslinking agent along the interface, which compatibilized PP/PBT blends. The mechanical property of the blends including 4 wt % SLCI contents was better than that of other SLCI contents in the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Mechanical and rheological properties of PP/SEBS/OMMT ternary composites
Authors: Su Feng‐Hua , Huang Han‐Xiong 
Published: February 2009

AbstractThe microstructure and mechanical properties of polypropylene (PP)/OMMT binary nanocomposites and PP/styrene‐6‐(ethylene‐co‐butylenes)‐6‐styrene triblock copolymer (SEBS)/OMMT ternary nanocomposites were investigated using X‐ray diffraction (XRD), transmission electron microscopy (TEM), and rheology and electromechanical testing machine. The results show that the organoclay layers are mainly intercalated and partially exfoliated in the PP‐based nanocomposites. The additions of SEBS and OMMT have no significant effect on the crystallization behavior of PP. At the same time, it can be concluded that the polymer chains of PP and SEBS have intercalated into the organoclay layers and increase the gallery distance after blending process based on the analytical results from TEM, XRD, and rheology, which result in the form of a percolated nanostructure in the PP‐based nanocomposites. The results of mechanical properties show that SEBS filler greatly improve the notched impact strength of PP, but with the sacrifice of strength and stiffness. OMMT can improve the strength and stiffness of PP and slightly enhance the notched impact strength of PP/PP‐g‐MA. In comparison with neat PP, PP/OMMT, and PP/SEBS binary composites, notched impact toughness of the PP/SEBS/OMMT ternary composites significantly increase. Moreover, the stiffness and strength of PP/SEBS/OMMT ternary nanocomposites are slightly enhanced when compared with neat PP. It is believed that the synergistic effect of both SEBS elastomer and OMMT nanoparticles account for the balanced mechanical performance of the ternary nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Autophotosensitive negative polyimide
Authors: Wang Rui , Jiang Xuesong , Yin Jie 
Published: February 2009

AbstractA novel autophotosensitive polyimide (APSPI) was synthesized through introducing benzophenone (BP) moiety into the backbone chain and acrylate group into side chain of PI. The BP moiety can generate active radicals, which can initiate acrylate group to form crosslinked network. The study of photosensitive properties revealed its good photolithographic properties, with a resolution about 12 μm and a sensitivity of 330 mJ/cm2. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of cholic acid‐containing biodegradable hydrogels by photoinduced copolymerization
Authors: Hao Jin‐Qing , Li Hong , Woo Hee‐Gweon 
Published: February 2009

AbstractA cholic acid (CA)‐containing biodegradable hydrogel (PLA‐PEG‐PLA‐co‐MACAH) was synthesized from the photoinduced copolymerization of a CA‐modified methacrylate monomer (MACAH), bearing a spacer of hexane‐1,6‐diol spacer between the methacryloyl and the cholanoate moieties, and a macromonomer (PLA‐PEG‐PLA‐DA), bearing two acryloyl end groups derived from a poly(lactic acid)‐b‐poly(ethylene glycol)‐b‐poly(lactic acid) triblock copolymer. The structure of MACAH was confirmed by FTIR, 1H‐NMR, and MS. The hydrogel PLA‐PEG‐PLA‐co‐MACAH was characterized by scanning electron microscopy and X‐ray diffraction. The experiment results showed that the swelling ratios of the hydrogels decreased with the increase of the CA fraction. The investigation on the in vitro degradation of the hydrogel showed that the CA‐containing hydrogels degraded much slower than the hydrogels without CA component. The bioactivity of the synthesized hydrogels was assessed by the simulated body fluid method. The observed formation of hydroxyapatite on the scaffold of the hydrogels indicated that the hydrogels possess good bioactivity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Polymerization of an epoxy resin modified with azobenzene groups monitored by near‐infrared spectroscopy
Authors: Fernández Raquel , Blanco Miren , Galante María J. , Oyanguren Patricia A. , Mondragon Iñaki 
Published: February 2009

AbstractNew photosensitive materials containing photochromic azobenzene moieties were synthesized. For this purpose, an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) was reacted with an azobenzene chromophore (disperse orange 3, AZ) to satisfactorily synthesize an azo‐modified prepolymer, which was then used to generate series of epoxy‐based polymers containing azo groups. Three different amines were used as hardeners, with the aim of obtaining materials with different chemical structures. Understanding the epoxy resin polymerization kinetics is essential for intelligent processing of materials. Near‐IR (NIR) spectral analysis was used to follow the polymerization kinetics. The quality of the NIR spectra enables concentrations of individual chemical species to be measured in real time. Conversion of epoxy and primary amine groups, as well as the concentration of different groups, as a function of reaction time was therefore calculated by this spectroscopic technique. Samples containing azo units were compared to the pure DGEBA/amine systems. Results showed that the azo‐prepolymer incorporation has an accelerating effect on polymerization rate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
PVC paste rheology: Study of process dependencies
Authors: Rasteiro M.G. , Tomás A. , Ferreira L. , Figueiredo S. 
Published: February 2009

AbstractA plastisol is a dispersion (suspension) of fine particles of poly(vinyl chloride) with a plasticizer that is normally applied over a substrate, by spreading or coating, before the gelification and fusion into the final product. Because of the first step, the plastisol rheology study is a very important factor which has to be taken into consideration to determine and fine tune the process conditions.This work is concerned with the study of the rheology of plastisols from selected PVC samples produced by the emulsion process, correlating it with the particle size distribution and surface characteristics from the polymer's powder and modifications during the plastisol aging process. The results obtained show a significant influence of the original polymer properties in the viscosity aging and viscoelastic behaviour of the plastisol. First, a significant decrease in viscosity can be achieved by changing a particular surfactant during the polymerization step. Second, the type of particle aggregates present in the powder, can determine the evolution of the particle size in the plastisol which, in turn, correlates directly with the observed modifications in the aging and viscoelastic behavior. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The effect of physical treatments of waste rubber powder on the mechanical properties of the revulcanizate
Authors: Lee Sung Hyo , Hwang Sung Hyuk , Kontopoulou Marianna , Sridhar V. , Zhang Zhen Xiu , Xu Deng , Kim Jin Kuk 
Published: February 2009

AbstractThe diversiform physical treatment processes of waste rubber powder were carried out using grinding process, ozone treatment, and ultrasonic treatment. The effects of these processes on hardness, specific gravity, crosslink, tensile strength, elongation, and dynamic mechanical properties were studied. Also, the morphology and the chain structure changing of waste rubber powder were studied by SEM and XPS, respectively. The ozone/ultrasonic treatment was found to be the most effective treatment to improve the mechanical properties of waste rubber powder revulcanizate. The effect of mechanism may be due to the sulfur crosslinkage network changed to a cyclic form. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Fractional contribution of major ions to the membrane potential of Drosophila melanogaster oocytes
Authors: Munley Susan M. , Kinzeler Sandra , Lizzano Rebecca , Woodruff Richard I. 
Published: February 2009

AbstractIn ovarian follicles of Drosophila melanogaster, ion substitution experiments revealed that K+ is the greatest contributor (68%) in setting oocyte steady‐state potential (Em), while Mg2+ and a metabolic component account for the rest. Because of the intense use made of Drosophila ovarian follicles in many lines of research, it is important to know how changes in the surrounding medium, particularly in major diffusible ions, may affect the physiology of the cells. The contributions made to the Drosophila oocyte membrane potential (Em) by [Na+]o, [K+]o, [Mg2+]o, [Ca2+]o, [Cl−]o, and pH (protons) were determined by substitutions made to the composition of the incubation medium. Only K+ and Mg2+ were found to participate in setting the level of Em. In follicles subjected to changes in external pH from the normal 7.3 to either pH 6 or pH 8, Em changed rapidly by about 6 mV, but within 8 min had returned to the original Em. Approximately half of all follicles exposed to reduced [Cl−]o showed no change in Em, and these all had input resistances of 330 kΩ or greater. The remaining follicles had smaller input resistances, and these first depolarized by about 5 mV. Over several minutes, their input resistances increased and they repolarized to a value more electronegative than their value prior to reduction in [Cl−]o. Together, K+ and Mg2+ accounted for up to 87% of measured steady‐state potential. Treatment with sodium azide, ammonium vanadate, or chilling revealed a metabolically driven component that could account for the remaining 13%. © 2009 Wiley Periodicals, Inc.