bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the curing and thermal behaviour of DGEBA in the presence of bis(4‐carboxyphenyl) dimethyl silane
Authors: Khurana Parveen , Aggarwal S , Narula AK , Choudhary Veena 
Published: May 2003

AbstractThe curing behaviour of diglycidyl ether of bisphenol‐A (DGEBA) was investigated by differential scanning calorimetry using bis(4‐carboxyphenyl) dimethyl silane (CPA) as a crosslinking agent and imidazole as a catalyst. Two exotherms were observed in the absence of catalyst in the temperature range 166–328 °C. A significant decrease in the curing temperature was observed when 0.1% imidazole was used as catalyst. Further increase in the concentration of imidazole resulted in a decrease in the peak exotherm temperature. The effect of stoichiometry of functional groups on the curing behaviour of DGEBA was investigated by taking varying mole ratios of CPA, ranging from 1 to 2.5, keeping the concentration of imidazole as 0.1% w/w. The heat of polymerization (ΔH) was found to be maximum at a molar ratio of 1:1.75 (DGEBA:CPA). Mixtures of diaminodiphenyl sulfone (DDS and CPA or phthalic anhydride (PA) and CPA in ratios of 1:0, 0.25:0.75, 0.5:0.5, 0.75:0.25) were also used to investigate the curing behaviour of DGEBA. A significant decrease in curing temperature of DGEBA/DDS was observed on partially replacing DDS with CPA, whereas marginal change in the curing temperatures was observed on replacing phthalic anhydride with CPA. The thermal stability of epoxy resin, cured isothermally, was evaluated by recording thermogravimetry/dynamic thermogravimetry traces in nitrogen atmosphere. The percentage char yield was highest for the sample cured using 1.75 mole of CPA. Copyright © 2003 Society of Chemical Industry
Thermoreversible gelation of poly(vinylidene fluoride)/poly(methyl acrylate) blends in diethyl azelate: a thermodynamic investigation
Authors: Dikshit Asok K , Jana Tushar , Malik Sudip , Nandi Arun K 
Published: May 2003

AbstractThe thermodynamic behaviour of poly(vinylidene fluoride) (PVF2)/poly(methyl acrylate) (PMA) blend gels in diethyl azelate (DEAZ) was studied by differential scanning calorimetry at three different blend compositions (x (weight fraction of PVF2 in the blend) = 0.75, 0.5 and 0.25). Transmission electron microscopy together with optical microscopy indicate the presence of fibrillar network morphology in the gels. The quasi‐binary phase diagrams drawn from both the heating and cooling processes are almost similar, with a hysteresis of 50–60 °C. The possibility of polymer–solvent compound formation in the blend gels have been explored from the composition dependency of enthalpy of gel fusion and enthalpy of gel formation data. Extending the procedure of the pure PVF2/DEAZ gel systems to blend gels, it has been surmised that polymer–solvent compound formation also occurs in blend gels, but the stoichiometry of the complexes varies with blend composition. The shapes of the quasi‐binary phase diagrams of the blend gels are different in some cases from that of pure PVF2/DEAZ, gel indicating that the polymer–solvent compounds are incongruent or singular type depending on the blend compositions. A possible explanation for this behaviour has been offered from entropic and enthalpic viewpoints. Copyright © 2003 Society of Chemical Industry
Thermal and mechanical properties of biodegradable blends of poly(L‐lactic acid) and lignin
Authors: Li Jianchun , He Yong , Inoue Yoshio 
Published: May 2003

AbstractThe thermal and mechanical properties of the biodegradable blends of poly(L‐lactic acid) (PLLA) and lignin prepared by manual mixing have been investigated. Both the results of DSC and FTIR spectral analyses indicated the existence of intermolecular interaction between PLLA and lignin. Furthermore, FTIR elucidated the existence of an intermolecular hydrogen‐bonding interaction. Study of the mechanical properties of the blends indicated that the maximum strength and the elongation of the material decreased and the Young's modulus remained almost constant when the lignin content reached 20%. Thermogravimetry indicated that lignin would accelerate the thermal degradation of PLLA when the content of lignin was more than 20%. Compared with some other biodegradable polymers, the blend of PLLA and lignin is thought to be a promising material, because the material properties, as well as the price, are at an acceptable level when the content of lignin is less than about 20%. Copyright © 2003 Society of Chemical Industry
Synthesis of styrene–maleic anhydride random copolymer and its compatibilization to poly(2,6‐dimethyl‐1,4‐phenylene ether)/brominated epoxy resin
Authors: Liang Guozheng , Meng Jiru , Zhao Lei 
Published: May 2003

AbstractStyrene–maleic anhydride random copolymer (R‐SMA7.5), with a low content of maleic anhydride (MAH) of about 7.5 mol%, has been prepared, and the copolymer was characterized by fourier‐transform infrared (FTIR) and 13C NMR techniques showing that the product contained only random copolymer without blocks. The miscibility between poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) and R‐SMA, was investigated by differential scanning calorimetry (DSC), showing that PPE was miscible with R‐SMA synthesized in our laboratory over the entire composition with low MAH content. A blend of R‐SMA18 (MAH content is about 18 mol%) and PPE was also studied by DSC, which showed that PPE was immiscible when R‐SMA was the major component, although it was miscible with limited composition. FTIR investigation showed that R‐SMA could react with bromide epoxy (BEP) resin at high temperature (180°). The heat‐resistance and mechanical properties of R‐SMA/PPE/BEP systems were tested and analyzed, and results indicated that R‐SMA could improve the miscibility of PPE and BEP with increasing Tg of the BEP phase and decreasing the Tg of the PPE slightly, improving the breaking elongation and breaking energy, which resulted from good miscibility between PPE and BEP with R‐SMA as the compatibilizer. Finally, the properties of the composites (copper clad laminate) with R‐SMA7.5 are studied and discussed. Copyright © 2003 Society of Chemical Industry
Effect of the nature and degree of crosslinking on Rose Bengal binding by DVB‐, NNMBA‐, HDODA‐ and TTEGDA‐crosslinked poly(N‐vinylpyrrolidone)s
Authors: Gigimol MG , Mathew Beena 
Published: May 2003

AbstractPoly(N‐vinylpyrrolidone)s with 2–20 mol% DVB, NNMBA, HDODA and TTEGDA crosslinkings were prepared by suspension polymerisation. The binding of Rose Bengal by these poly(N‐vinylpyrrolidone)s was followed by a batch equilibration method. In order to optimise the conditions of dye binding, the effect of the concentration of Rose Bengal solutions, temperature and pH were followed. Kinetic studies showed that the binding of Rose Bengal by poly(N‐vinylpyrrolidone)s is a phase boundary process followed by a three‐dimensional diffusion. Copyright © 2003 Society of Chemical Industry
The influence of interphase on nylon‐6/nano‐SiO2 composite materials obtained from in situ polymerization
Authors: Li Ying , Yu Jian , Guo Zhao‐Xia 
Published: May 2003

AbstractThree commercially available silane, titanate and aluminate based coupling agents were used to pretreat nano‐SiO2 for the preparation of nylon‐6/nano–SiO2 composites via in situ polymerization. The interphases formed in different composite systems and their influence on material properties were investigated. Results indicated that the interfacial interactions differed between composite systems, whereas rigidity and toughness of composites were all improved by addition of pretreated silicas at an optimal content of 4.3 wt%. The presence of pretreated silicas did not have a distinct influence in the non‐isothermal crystallization behaviour of the nylon matrix. The composites containing pretreated silicas had slightly higher dynamic viscosities and superior storage moduli at high frequency, compared with neat nylon‐6. Copyright © 2003 Society of Chemical Industry
The influence of wax content on the physical properties of low‐density polyethylene–wax blends
Authors: Djoković V , Mtshali TN , Luyt AS 
Published: May 2003

AbstractThe influence of wax content on the thermal, mechanical and viscoelastic properties of low‐density polyethylene (LDPE)–oxidized wax miscible blends have been investigated. It was found that small concentrations of wax improved physical properties such as thermal stability, elastic modulus and yield stress. At higher concentrations, however, due to crystal phase separation, wax deteriorates the thermal as well as the mechanical properties. It was also shown that a formerly established two‐process model for the stress relaxation in semicrystalline polymers could be used for the explanation of the viscoelastic behaviour of the blends. Copyright © 2003 Society of Chemical Industry
Ring‐opening polymerization of lactones initiated by diphenylzinc–coinitiator systems
Authors: Vivas M , Mejías N , Contreras J 
Published: May 2003

AbstractDiphenylzinc, alone or in combination with water and butanone as coinitiators, was used as a polymerization initiator system for a variety of lactones at varying temperatures. The resulting data indicate that the course of the polymerization is greatly influenced by the lactone structure, as well as by the molar ratio of coinitiator to diphenylzinc. When used alone, diphenylzinc exhibited high activity as an initiator in δ‐valerolactone polymerizations, although it was less efficient when used in the β‐butyrolactone and the β‐propiolactone polymerizations. Activity in the polymerization of β‐lactones was increased by adding small amounts of butanone or water. It was also observed that the diphenylzinc–butanone combination was more effective than the diphenylzinc–water mixture in the polymerizations of β‐butyrolactone and β‐propiolactone. Copyright © 2003 Society of Chemical Industry
Thermal degradation of flame‐retarded polyethylene/magnesium hydroxide/poly(ethylene‐co‐propylene) elastomer composites
Authors: Wang Zhengzhou , Hu Keliang , Hu Yuan , Gui Zhou 
Published: May 2003

AbstractMagnesium hydroxide‐based halogen‐free flame retarded linear low‐density polyethylene (LLDPE) composites containing poly(ethylene‐co‐propylene) (EP) elastomer were prepared by a melt process and subsequently vulcanized thermally. The thermal degradation of the composites was studied using thermogravimetric (TG) analysis and real‐time Fourier transform infrared (RT‐FTIR) spectroscopy. The combustion residues from the composites were characterized by Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS). The results from TG and RT‐FTIR tests show that the incorporation of a suitable amount of the elastomer into polyethylene/magnesium hydroxide composites after vulcanization increases the thermal stability. A graphite‐like char was found for the composites with EP elastomer, from Raman spectroscopy studies. XPS results indicate that there are several forms of carbon present in the combustion residues of the composites with EP elastomer, compared with only one form of carbon in the residues of the composites without the elastomer. Copyright © 2003 Society of Chemical Industry
The chain extension of anionic prepolymers in the preparation of aqueous poly(urethane–urea) dispersions
Authors: Lahtinen Mika , Pinfield Rachel K , Price Colin 
Published: May 2003

AbstractAnionic polyurethane prepolymers end‐capped with isocyanate groups were dispersed and chain‐extended in aqueous media using three different extension agents: hydrazine, 1,2‐ethylene diamine (EDA) and 1,2‐propylene diamine (PDA). Two types of prepolymer were used. The first was prepared from isophorone diisocyanate (IPDI), α,α‐dimethylol propionic acid (DMPA) and poly(propylene oxide) diol (PPO) and the second from α,α,α′,α′‐tetramethyl‐1,3‐xylylene diisocyanate (m‐TMXDI), poly(caprolactone) diol (PCL) and DMPA. The colloidal particles which formed in the dispersion process and the constituent poly(urethane–urea) chains were characterised by a combination of dynamic and static light scattering, gel permeation chromatography and FTIR spectroscopy. Using EDA as the extender, a study was made of how the degree of extension depended on the molar ratio of amine to isocyanate groups, [NH2]/[NCO] (= RA, I). It was found that using a stoichiometric balance of isocyanate and amine groups did not lead to high degree of extension, and better chain extension was obtained at lower RA, I values. In a comparative study using stoichiometric balances of isocyanate and amine groups, the degrees of extension obtained using PDA and EDA were approximately the same, while hydrazine was the least effective. Force–extension studies were carried out on samples prepared from films cast from the aqueous poly(urethane–urea) dispersions in order to assess the influence of chain‐extender type and stoichiometry on bulk properties; values of Young's modulus, tensile strength and maximum extension are reported. Copyright © 2003 Society of Chemical Industry
The influence of layered compounds on the properties of starch/layered compound composites
Authors: Wilhelm Helena‐M , Sierakowski Maria‐R , Souza Gabriel P , Wypych Fernando 
Published: May 2003

AbstractGlycerol‐plasticized starch films were modified by addition of various layered compounds as fillers, two being of natural origin (kaolinite, a neutral mineral clay, and hectorite, a cationic exchanger mineral clay) and two synthetic (layered double hydroxide, LDH, an anionic exchanger, and brucite, having a neutral structure). The effects of the filler type and the plasticizer were analyzed by X‐ray diffraction, dynamic mechanical analysis and thermogravimetry. The storage modulus was higher for kaolinite > brucite > hectorite than for LDH starch composites. However, only the hectorite filler presented a shift of the interplanar basal distance to higher values, which represents the intercalation of glycerol molecules between the clay layers. The glycerol intercalation is minimized in plasticized–oxidized starch films where the oxidized starch chains are preferentially intercalated. Copyright © 2003 Society of Chemical Industry
Crosslinking of elastomers upon ageing: a kinetic approach based on crystallinity changes followed by DSC
Authors: Baba Mohamed , George Soney , Gardette Jean Luc , Lacoste Jacques 
Published: May 2003

AbstractIt was observed that crosslinking reactions resulting both from peroxide decomposition or photoageing at wavelengths longer than 300 nm involve a drastic decrease of the crystallinity of some dienic elastomers, such as polybutadienes (rich in cis 1,4 and 1,2 microstructures) and polycyclo‐octene. By comparing precisely the rate of decomposition of dicumyl peroxide and that of the crystallinity decrease, it was possible to show that the kinetics of crystallinity loss observed upon ageing can be identified with that of the crosslinking of elastomers. The results indicate that the crosslinking process can be followed directly by DSC measurement of the crystallization/melting cycle.© 2003 Society of Chemical Industry
Micellar solutions of amphipathic copolymers based on carboxymethyl cellulose
Authors: Cao Ya , Li Huilin 
Published: May 2003

AbstractA novel family of amphipathic copolymers based on carboxymethyl cellulose (CM‐cellulose) has been synthesized through ultrasonic irradiation. Their micellar conformation in aqueous solution was studied by dynamic laser scattering, environmental scanning electron microscopy and gel permeation chromatography. The results show that conformation of copolymer molecules is totally different from that of CM‐cellulose because of the introduction of the surface active macromonomers. Due to the influence of hydrophobic character and molecular weight, different amphipathic copolymers have different micellar conformations, such as cylindrical, spheroidal or ellipsoidal micelles. In the range of concentration tested, the normalized first‐order autocorrelation function g(1)(τ) of a copolymer of CM‐cellulose and poly(ethylene oxide) dodecyl ether acrylate does not fit a single‐exponential decay, indicating a polydisperse system and the existence of species of different shapes and size. At different concentrations, the hydrodynamic radii of micelles (R) almost distribute into two regions of smaller and larger size. With increasing copolymer concentration, the region of smaller R remains in the range 30–100 nm and is considered to represent monomolecular micelles, while the larger R region increases gradually with concentration, which means that polymolecular micelles increase in size.© 2003 Society of Chemical Industry
Synthesis of liquid crystalline–amorphous block copolymers by the combination of atom transfer and photoinduced radical polymerization mechanisms
Authors: Serhatli I. E. , Kacar T. , Önen A. 
Published: May 2003

AbstractThe synthesis of ABA‐type block copolymers, involving liquid‐crystalline 6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate (LC6) and styrene (St) monomer with copper‐based atom transfer radical polymerization (ATRP) and photoinduced radical polymerization (PIRP), was studied. First, photoactive α‐methylol benzoin methyl ether was esterified with 2‐bromopropionyl bromide, and it was subsequently used for ATRP of LC6 in diphenylether in conjunction with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalyst. The obtained photoactive functional liquid‐crystalline polymer, poly[6‐(4‐cyanobiphenyl‐4′‐oxy)hexyl acrylate] (PLC6), was used as an initiator in PIRP of St. Similarly, photoactive polystyrenes were also synthesized and employed for the block copolymerization of LC6 in the second stage. The spectral, thermal, and optical measurements confirmed a full combination of ATRP and PIRP, which resulted in the formation of ABA‐type block copolymers with very narrow polydispersities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1892–1903, 2003
Supramolecular discotic liquid crystals from wedge‐shaped diacetylenes and their polymerization
Authors: Hwang In Ho , Lee Seung Ju , Chang Ji Young 
Published: May 2003

AbstractWedge‐shaped diacetylenic compounds were synthesized by the amidation reaction between the linear diacetylenic side groups and 5‐acetamidoisophthalic acid. The compounds showed enantiotropic transitions. In the liquid‐crystalline states, they were dimerized via hydrogen bonding of acetamide groups, forming disklike supramolecules and had rectangular columnar phases. Polymerization was carried out by UV irradiation and thermal annealing at their mesophase temperatures, giving polydiacetylenes. After polymerization, the compounds became dark red, but their textures were still birefringent. The IR and ultraviolet–visible study demonstrated that the polymerization proceeded topochemically by 1,4‐addition. X‐ray analysis showed that the UV‐polymerized samples maintained rectangular columnar phases. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1881–1891, 2003
Pore size modification of macroporous crosslinked poly(dicyclopentadiene)
Authors: Della Martina Alberto , Garamszegi László , Hilborn Jöns G. 
Published: May 2003

AbstractThis article describes the pore size modification and in situ surface functionalization of macroporous crosslinked poly(dicyclopentadiene), produced by chemically induced phase separation, with norbornene‐functionalized poly(ethylene glycol) telechelic oligomers. The microstructure of the open porosity materials produced with this technique consisted of agglomerated particles. The incorporation of these telechelic oligomers allowed a substantial decrease in the pore size and a related increase in the internal surface area. These functionalized oligomers acted as stabilizers around the primary particles produced by phase separation and blocked their growth so that the materials resulting from the agglomeration of these smaller particles showed finer microstructures. The resulting porous materials were characterized by scanning electron microscopy, density measurements, nitrogen adsorption, and mercury porosimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2036–2046, 2003
Synthesis and characterization of multiblock copolymers based on L‐lactic acid, citric acid, and poly(ethylene glycol)
Authors: Yao Fanglian , Bai Yun , Zhou Yutao , Liu Chang , Wang Hao , Yao Kangde 
Published: May 2003

AbstractBecause poly(L‐lactic acid) (PLLA) is a biodegradable polyester with low immunogenicity and good biocompatibility, it is used as a biomaterial. However, hydrophobic PLLA does not have any reactive groups. Thus, its application is limited. To increase the hydrophilicity of PLLA and accelerate its degradation rate, functionalized pendant groups and blocks were introduced through copolymerization with citric acid and poly(ethylene glycol) (PEG), respectively. This article describes the synthesis and characterization of poly(L‐lactic‐co‐citric acid) (PLCA)‐PLLA and PLCA‐PEG multiblock copolymers. The results indicated that the hydrolysis rate was enhanced, and the hydrophilicity was improved because of the incorporation of carboxyl groups in PLCA‐PLLA. The joining of the PEG block led to improved hydrophilicity of PLCA, and the degradation rate of PLCA‐PEG accelerated as compared with that of PLCA‐PLLA. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2073–2081, 2003
Ring‐opening metathesis polymerization as a route to controlled copolymers of ethylene and polar monomers: Synthesis of ethylene–vinyl chloride‐like copolymers
Authors: Yang Hongli , Islam Manirul , Budde Charles , Rowan Stuart J. 
Published: May 2003

AbstractA series of ethylene–vinyl chloride‐like copolymers were prepared by ring‐opening metathesis polymerization (ROMP). The route to these materials included the bulk polymerization of 5‐chlorocyclooctene and 5,6‐dichlorocyclooctene with the first‐generation Grubbs' catalyst, followed by diimide hydrogenation of the resulting unsaturated polymers. In addition, the amount of chlorine in these materials was varied by the copolymerization of 5‐chlorocyclooctene with cyclooctene. These materials were fully characterized by NMR (1H and 13C), gel permeation chromatography, and Fourier transform infrared spectroscopy. Finally, hydroboration was carried out on the ROMP product of 5‐chlorocyclooctene to yield a polymer, which was effectively a vinyl alcohol–vinyl chloride–ethylene terpolymer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2107–2116, 2003
Kinetics of the ring‐opening metathesis polymerization of a 7‐oxanorbornene derivative by Grubbs' catalyst
Authors: Holland Marium G. , Griffith Veronica E. , France Marcia B. , Desjardins Steven G. 
Published: May 2003

AbstractThe kinetics of the initiation and propagation of the ring‐opening metathesis polymerization of exo,exo‐5,6‐bis(methoxycarbonyl)‐7‐oxabicyclo[2.2.1]hept‐2‐ene catalyzed by Grubbs' catalyst (Cl2(PCy3)2RuCHPh) were measured by ultraviolet–visible and 1H NMR spectroscopy, respectively. Activation parameters for these processes were also determined. Although the ratio of the rate constant of initiation to the rate constant of propagation was determined to be less than 1 for this system, this polymerization showed many of the characteristics of a living system, including low polydispersities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2125–2131, 2003
Subcutaneous emphysema secondary to foreign‐body aspiration
Authors: Findlay C.A. , Morrissey S. , Paton J.Y. 
Published: May 2003

AbstractPneumomediastinum is uncommon in pediatric medical practice, outside the neonatal period. While asthma or respiratory infections are the most frequent underlying causes, it is important not to forget the possibility of foreign body aspiration, particularly after the clinical presentation. Pediatr Pulmonol. 2003; 36:81–82. © 2003 Wiley‐Liss, Inc.