bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses of poly(lactic acid)‐poly(ethylene glycol) serial biodegradable polymer materials via direct melt polycondensation and their characterization
Authors: Wang Zhao‐Yang , Zhao Yao‐Ming , Wang Fang 
Published: July 2006

AbstractDirectly starting from lactic acid (LA) and poly(ethylene glycol) (PEG), biodegradable material polylactic acid‐polyethylene glycol (PLEG) was synthesized via melt copolycondensation. The optimal synthetic conditions, including prepolymerization method, catalyst kinds and quantity, copolymerization temperature and time, LA stereochemical configuration, feed weight ratio mLA/mPEG and Mn of PEG, were all discussed in detail. When D,L‐LA and PEG (Mn = 1000 Da) prepolymerized together as feed weight ratio mD,l‐LA/mPEG = 90/10, 15 h copolycondensation under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave D,L‐PLEG1000 with the highest [η] of 0.40 dL/g, and the corresponding MW was 41,700 Da. Using L‐LA instead of D,L‐LA, 10 h polymerization under 165°C and 70 Pa, and 0.5 wt % SnO as catalyst, gave L‐PLEG1000 with the highest [η] of 0.21 dL/g and MW of 15,600 Da. Serial D,L‐PLEG with different feed weight ratio and Mn of PEG were synthesized via the simple and practical direct melt copolycondensation, and characterized with FTIR, 1H NMR, GPC, DSC, XRD, and contact angle testing. D,L‐PELG not only had higher MW than PDLLA, PLLA and L‐PELG, but also better hydrophilicity than PDLLA. The novel one‐step method could be an alternative route to the synthesis of hydrophilic drug delivery carrier PLEG instead of the traditional two‐step method using lactide as intermediate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 577–587, 2006
Hot compaction of polyoxymethylene, part 1: Processing and mechanical evaluation
Authors: Jebawi K. Al , Sixou B. , Séguéla R. , Vigier G. , Chervin C. 
Published: July 2006

AbstractThe hot‐compaction of polyoxymethylene powders in the solid state, otherwise pressure‐assisted sintering, is studied as an alternative way to the melt‐compression or injection molding processes. A native powder issued from suspension polymerization has been used, together with powders obtained from grinding of melt‐extruded pellets. The experimental conditions were optimized with regard to temperature, pressure, and time. Temperature is the most sensitive parameter of the process. Sintering at temperature close to the onset of the melting range turned out to be necessary for an efficient welding of the powder particles, as judged from mechanical properties. Despite a strong loss of ductility, the sintered samples have been easily machined out into strips for mechanical testing. A significant increase in crystallinity is observed for the sintered samples, as compared with the compression‐molded ones, accompanied with a nearly twofold increase of the Young's modulus. Scanning electron microscopy revealed that rupture of the sintered samples involves both inter‐ and intra‐granular fracture. Welding of the crystallites via molecular diffusion at the particle interface is suggested to be the mechanism of sintering. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1274–1284, 2006
Relationship between anisotropic orientation and curing of liquid crystalline epoxy resin
Authors: Lee Jun Yeob 
Published: July 2006

AbstractThe effect of macroscopic orientation of liquid crystalline epoxy (LCE) resin, 4,4′‐di(2,3‐epoxypropenyloxy)phenyl benzoate, on the curing and liquid crystalline phase of LCE/diaminodiphenylester (DDE) mixture was investigated. Birefringence and curing rate of uniaxially aligned LCE/DDE on rubbed PI surface was compared with those of unaligned LCE/DDE. Anisotropic orientation accelerated the curing of LCE and facilitated the formation of liquid crystalline phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1712–1716, 2006
Filtration properties of electrospinning nanofibers
Authors: Qin Xiao‐Hong , Wang Shan‐Yuan 
Published: July 2006

AbstractElectrospinning is a relatively simple method to produce submicron fibers from solutions of different polymers and polymer blends. The extensive application in future of electrospinning nanofibers is filtration. In this article, the filtration properties of electrospinning nanofibers were investigated. During the experiments, nanofibers layers with different area weight were electrospun on the spunbonded or meltblown sublayers. Fiber diameter, pore diameter, filtration efficiency as well as filtration resistance of nanofibers web and sublayers were measured, respectively, through a series of experiments. The results show that the fiber diameter of nanofibers is much smaller than that of sublayers. It is also found that the pore diameter of nanofibers web is much smaller than sublayers and coefficient variation of the pore diameter of nanofibers web is much smaller than sublayers. Moreover, the filtration efficiency and filtration resistance of sublayers are lower than nanofibers webs. The balance between efficiency and press drop is also investigated in the article. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1285–1290, 2006
Polyaniline salts and complexes: Efficient and reusable catalyst for the one‐pot synthesis of 5‐(methoxycarbonyl)‐6‐methyl‐4‐phenyl‐3,4‐dihydropyrimidin‐2(1h)‐one
Authors: Gangadasu Banda , Palaniappan Srinivasan , Amarnath Chellachamy Anbalagan , Rao Vaidya Jayathirtha 
Published: July 2006

AbstractPolyaniline salts were prepared by doping polyaniline base with different Bronsted acids (sulfuric, nitric, phosphoric, perchloric, hydrochloric acid) and organic acids (p‐toluene sulfonic acid, 5‐sulfosalicylic acid). Polyaniline complexes were also prepared using Lewis acids (aluminum chloride, ferric chloride). Polyaniline salts and polyaniline complexes were used as catalysts in Biginelli reaction for 5‐(methoxycarbonyl)‐6‐methyl‐4‐phenyl‐3,4‐dihydropyrimidin‐2(1H)‐one synthesis. Benzaldehyde and urea were reacted with methyl acetoacetate using polyaniline‐p‐toluene sulfonate salt as catalyst with different reaction time, temperature, and amount of catalyst. The use of polyaniline catalysts is feasible because of the easy preparation, easy handling, stability, easy recovery, simple work‐up procedure, reusability, excellent activity with less amount of catalyst, and eco‐friendly nature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1741–1745, 2006
Recycling of styrene polymers from shredded screen housings containing brominated flame retardants
Authors: Schlummer Martin , Mäurer Andreas 
Published: July 2006

AbstractRecycling of plastics from screen housing poly mers is considered to be helpful to fulfill the requirements of the European waste of electric and electronic equipment directive. However, brominated flame retardants (BFR) and polybrominated dioxins and furans, which are partly limited in marketable products by European and German legislation, have been identified in waste screen housings and need to be eliminated. On application to housing shredder, sink and float was investigated as sorting technology, since BFR‐equipped styrene polymers exhibit higher densities compared to corres ponding non‐BFR types. The feasibility of this concept was proven by database studies and density monitoring of waste screen housing. Laboratory and small‐technical scale trials with different mixtures of TV‐sets and PC monitor housings revealed that only 5–20% of the original bromine load remained in the target fractions, resulting in bromine levels between 0.18–1.39%. Recycled polymers from fractions rich in HIPS‐based TV‐set casings did not exceed given threshold limits for PBDD/F and octabromodiphenylether. They were recovered with yields of 52–63% and exhibited mostly virgin‐like mechanical properties. In contrast, PC monitor housing fractions were characterized by low yield, high bromine levels in recycled products and brittle recycled polymers. Furthermore, pilot application of another separation approach, the specific swell and float technology, allowed the separation of upgraded HIPS qualities from bromine‐reduced TV‐set fractions. In contrast, this success has not yet been achieved with waste PC monitors. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1262–1273, 2006
Rheological properties of ethylcellulose latex
Authors: Gallardo V. , Morales M. E. , López‐Viota J. , Durán J. D. G. , Ruiz M. A. 
Published: July 2006

AbstractBecause of their large specific surface area, aqueous‐based pseudolatex systems of ethylcellulose can absorb large amounts of drugs. In addition, the stability of polymeric particles in biological fluids delays the release of the drug as in controlled drug delivery systems. The aim of the present study was to characterize the rheological properties of latex particles as a measure of their colloidal stability. Here, we report the effect of three variables: pH, electrolyte concentration, and temperature. The rheograms clearly show that the polymer suspensions displayed Bingham plastic behavior. Internal structuring of the latex was greatest at acid and natural pH values, particularly at the highest ionic strength. In acid solutions, only temperature appeared to play a fundamental role; both the shear stress corresponding to the onset of nonlinear viscoelasticity and the elastic modulus at all frequencies were higher at 37°C than those at room temperature. This is assumed to be a consequence of deformation of the polymer particles upon heating. The effect of ionic strength was noticeable only at the natural pH (pH ≅ 6.5). At high concentrations of sodium chloride, the particles aggregated because of the decrease in double layer repulsion, and as a result, the latex became structured and its elastic modulus subsequently increased. Interestingly, when the temperature was increased further, this structure presumably broke, down, at least partially, and the storage modulus was reduced. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 847–851, 2006
Mechanical properties and crosslink density of rare earth‐modified high‐abrasion furnace‐filled powdered natural rubber
Authors: Guo Yubo , Wang Lianshi , Zhang Anqiang 
Published: July 2006

AbstractHigh‐abrasion furnace‐filled powdered natural rubber [P(NR/HAF)] has more advantages than traditional HAF‐filled bale NR (NR/HAF) because of its better environmental performance and easier processing quality, but its lower mechanical properties are disadvantageous. To improve the mechanical properties, rare earth‐modified HAF‐filled powdered NR [P(NR/HAF‐Ln)] (Ln = Sm,La,Pr) was prepared by means of coacervation–coprecipitation, using rare earth‐modified HAF as separant and filler. The effect on mechanical properties of P(NR/HAF‐Ln) vulcanizate exerted by the emulsifier/HAF ratio, powdering temperature, Ln/HAF ratio and type of Ln, and HAF content were studied. The results indicated that when optimum formulation, the mechanical properties of P(NR/HAF‐Ln) vulcanizate were better than P(NR/HAF) vulcanizate. In addition, the relationship of the apparent crosslink density and HAF content of P(NR/HAF‐Ln), P(NR/HAF), NR/HAF vulcanizates was also investigated, along with their SEM microphotographs of tensile fracture surface, which indicated that the excellent mechanical properties of P(NR/HAF‐Ln) vulcanizate was attributed to correct amount of Ln that could increase crosslink density and reinforce the interface structure of NR matrix/HAF‐Ln particle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1755–1762, 2006
RAFT synthesis of poly(N‐isopropylacrylamide) and poly(methacrylic acid) homopolymers and block copolymers: Kinetics and characterization
Authors: Yang Chiming , Cheng Yu‐Ling 
Published: July 2006

AbstractReversible addition‐fragmentation chain transfer (RAFT) polymerization was used successfully to synthesize temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAAm), poly(methacrylic acid) (PMAA), and their temperature‐responsive block copolymers. Detailed RAFT polymerization kinetics of the homopolymers was studied. PNIPAAm and PMAA homopolymerization showed living characteristics that include a linear relationship between Mn and conversion, controlled molecular weights, and relatively narrow molecular weight distribution (PDI < 1.3). Furthermore, the homopolymers can be reactivated to produce block copolymers. The RAFT agent, carboxymethyl dithiobenzoate (CMDB), proved to control molecular weight and PDI. As the RAFT agent concentration increases, molecular weight and PDI decreased. However, CMDB showed evidence of having a relatively low chain transfer constant as well as degradation during polymerization. Solution of the block copolymers in phosphate buffered saline displayed temperature reversible characteristics at a lower critical solution temperature (LCST) transition of 31°C. A 5 wt % solution of the block copolymers form thermoreversible gels by a self‐assembly mechanism above the LCST. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1191–1201, 2006
Preparation of polyamide resin‐encapsulated melamine cyanurate/melamine phosphate composite flame retardants and the fire‐resistance to glass fiber‐reinforced polyamide 6
Authors: Liu Yuan , Wang Qi , Fei Guoxia , Chen Yinghong 
Published: July 2006

AbstractIn this study, melamine cyanurate (MCA)/melamine phosphate (MP) composite flame retardants were synthesized in the solution of phosphoric acid/polyamide 6 (PA6). Phosphoric acid acted as the solvent of PA6, catalyst of melamine‐cyanurate self‐assembly reaction and reactant of melamine‐phosphoric acid reaction. With the consumption of the acid, the pH value of the system increased, and the solved PA6 precipitated on the surface of the flame retardant particles to form polymeric encapsulation. This technology realized the synthesis and surface modification of the flame retardants in one process. The catalyst and solvent, phosphoric acid, was finally converted into the product MP, and need no an additional removing process. The encapsulated MCA/MP (EMCMP) composite flame retardants were successfully applied in the fire‐resistance to glass fiber (GF)‐reinforced PA6. Because the encapsulated layer of EMCMP was also PA6, good interfacial compatibility and effective dispersion of EMCMP in PA6 resin can be obtained, and the corresponding flame retardant materials showed excellent flame retardancy and mechanical performance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1773–1779, 2006
Durable antibacterial finish on cotton fabric by using chitosan‐based polymeric core‐shell particles
Authors: Ye Weijun , Xin John H. , Li Pei , Lee Kam‐Len Daniel , Kwong Tsz‐Leung 
Published: July 2006

AbstractCotton fabric with excellent antibacterial durability was obtained when treated with chitosan‐containing core‐shell particles without any chemical binders. These amphiphilic nanosized particles with antibacterial chitosan shells covalently grafted onto polymer cores were prepared via a surfactant‐free emulsion copolymerization in aqueous chitosan. Herein, two core‐shell particles, one with poly(n‐butyl acrylate) soft core and another with crosslinked poly(N‐isopropylamide) hard core, were synthesized and applied to cotton fabric by a conventional pad‐dry‐cure process. Antimicrobial activity was evaluated quantitatively using a Shake Flask Method in which the reduction of the number of Staphylococcus aureus cells was counted. The results showed that treated fabric had an excellent antibacterial property with bacterial reduction higher than 99%. The antibacterial activity maintained at over 90% reduction level even after 50 times of home laundering. The fabric surface morphology as well as the effect of latex particles with different core flexibilities on fabric hand, air permeability, break tensile strength, and elongation was investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1787–1793, 2006
A cellulose‐based hydrogel as a potential bulking agent for hypocaloric diets: An in vitro biocompatibility study on rat intestine
Authors: Sannino A. , Madaghiele M. , Lionetto M. G. , Schettino T. , Maffezzoli A. 
Published: July 2006

AbstractA number of over‐the‐counter slimming products are currently available on the market. However, there is no scientific consensus over their effectiveness in promoting and sustaining weight loss. The need to develop an alternative dietary supplement for the treatment of obesity and overweight makes attractive a polyelectrolyte cellulose‐based hydrogel, crosslinked through a water soluble carbodiimide, as a potential bulking agent or stomach filler for hypocaloric diets. The hydrogel is envisaged to be administered orally to absorb water in the stomach, thus swelling and giving a sense of fullness, and to be finally expelled by fecal way. To this purpose, a preliminary assessment of hydrogel swelling capacity in distilled water has been performed, and the biocompatibility of the material with respect to intestinal tissues has been evaluated in vitro. The direct contact with the intestinal mucosa in vivo has been simulated by contacting the hydrogel with the jejunum tract of rat intestine, and the capacity of the material to maintain the epithelial barrier integrity has been monitored by means of transepithelial electric resistance measurements and lactate dehydrogenase release assay. The reported results evidence that the hydrogel is well tolerated by the intestinal tissue during the expected time of contact in vivo. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1524–1530, 2006
Application of degradation kinetics to the rheology of poly(hydroxyalkanoates)
Authors: Harrison Graham M. , Melik David H. 
Published: July 2006

AbstractThe time‐dependent rheological behavior of a series of 3‐hydroxybuytrate‐based semicrystalline copolymers is employed to determine the expected rheological curves that would be generated in the absence of any polymer degradation. Both dynamic frequency sweep and shear rate sweep experiments were analyzed. A model for the degradation kinetics, coupled with standard rheological relationships, was employed to extrapolate the measured sweeps to predicted curves at time zero, prior to degradation. The model is broadly applicable over a wide range of frequencies or shear rates, and generates a single degradation rate constant k for each polymer studied. A similar, although ad hoc, procedure was applied to the dynamic storage and loss moduli. The model provides a method for determining the rheological behavior of degrading polymers over a time interval, typically found in processing applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1794–1802, 2006
Preparation, characterization, and thermal properties of polystyrene‐block‐quaternized poly(4‐vinylpyridine)/Montmorillonite nanocomposites
Authors: Zhang Bao‐Qing , Chen Guang‐De , Pan Cai‐Yuan , Luan Bin , Hong Chun‐Yan 
Published: July 2006

AbstractPolystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) was synthesized by two steps of reversible addition‐fragmentation transfer (RAFT) polymerization of styrene (St) and 4‐vinylpyridine (4VP) successively. After P4VP block was quaternized with CH3I, PS‐b‐quaternized P4VP/montmorillonite (PS‐b‐QP4VP/MMT) nanocomposites were prepared by cationic exchange reactions of quaternary ammonium ion in the PS‐b‐QP4VP with ions in MMT. The results obtained from X‐ray diffraction (XRD) and transmission electron microscopy (TEM) images demonstrate that the block copolymer/MMT nanocomposites are of intercalated and exfoliated structures, and also a small amount of silicates' layers remained in the original structure; differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results show that the nanocomposites displayed higher glass transition temperature (Tg) and higher thermal stability than that of the corresponding copolymers. The blending of PS‐b‐QP4VP/MMT with commercial PS makes MMT to be further separated, and the MMT was homogeneously dispersed in the polymer matrix. The enhancement of thermal stability of PS/PS‐b‐QP4VP/MMT is about 20°C in comparison with commercial PS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1950–1958, 2006
Preparation and crystallization of poly(ethylene terephthalate)/SiO2 nanocomposites by in‐situ polymerization
Authors: Yang Yongzhe , Xu Hong , Gu Hongchen 
Published: July 2006

AbstractPoly(ethylene terephthalate) (PET)/SiO2 nanocomposites were prepared by in situ polymerization. The dispersion and crystallization behaviors of PET/SiO2 nanocomposites were characterized by means of transmission electron microscope (TEM), differential scanning calorimeter (DSC), and polarizing light microscope (PLM). TEM measurements show that SiO2 nanoparticles were well dispersed in the PET matrix at a size of 10–20 nm. The results of DSC and PLM, such as melt‐crystalline temperature, half‐time of crystallization and crystallization kinetic constant, suggest that SiO2 nanoparticles exhibited strong nucleating effects. It was found that SiO2 nanoparticles could effectively promote the nucleation and crystallization of PET, which may be due to reducing the specific surface free energy for nuclei formation during crystallization and consequently increase the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 655–662, 2006
Novel Template‐Directed Anodic Phenol‐Coupling Reaction
Authors: Malkowsky Itamar M. , Rommel Christina E. , Fröhlich Roland , Griesbach Ulrich , Pütter Hermann , Waldvogel Siegfried R. 
Published: July 2006

AbstractSubstituted phenols were anodically coupled to the corresponding 2,2′‐biphenols via tetraphenoxy borate derivatives. This electrochemical method is particularly useful for methyl‐substituted substrates, such as 2,4‐dimethyl phenol. The selective ortho‐coupling reaction can be easily performed on a multikilogram scale.
Copper(II)‐Promoted Regioselective Synthesis of 1,4‐Disubstituted 1,2,3‐Triazoles in Water.
Authors: Reddy K. Rajender , Rajgopal K. , Kantam M. Lakshmi 
Published: July 2006

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Four New Isoflavonoids from the Stem Bark of Erythrina variegata.
Authors: Li Xiaoli , Wang Naili , Wong Man Sau , Chen Albert S. C. , Yao Xinsheng 
Published: July 2006

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.