bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of crystalline and orientational memory phenomena on the isothermal bulk crystallization and subsequent melting behavior of poly(trimethylene terephthalate)
Authors: Supaphol Pitt , Srimoaon Phornphon , Sirivat Anuvat 
Published: June 2004

AbstractThe effects of crystalline and orientational memory phenomena on the subsequent isothermal crystallization and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) were investigated by studying the effect of prior melt‐annealing temperature, Tf, on the subsequent isothermal crystallization kinetics, crystalline structure and subsequent melting behavior of neat and sheared PTT samples. On partial melting, choices of the Tf used to melt the samples played an important role in determining their bulk crystallization rates, in which the bulk crystallization rate parameters studied were all found to decrease monotonically with increasing Tf. The decrease in the values of these rate parameters with Tf continued up to a critical Tf value (ie ca 275 °C for neat PTT samples and ca 280 °C for PTT samples which were sheared at shear rates of 92.1 and 245.6 s−1). Choices of the Tf used to melt neat PTT samples had no effect on the crystal structure formed. The subsequent melting behavior suggested that the Tf used to melt both neat and sheared samples had no effect on the peak positions of the melting endotherms observed and that the observed peak values of these endotherms for all sample types studied were almost identical. Copyright © 2004 Society of Chemical Industry
Impact response of epoxy systems containing short fibres and/or oxide particles as reinforcements
Authors: Kishore  , Harimkar SP , Desai DS 
Published: June 2004

AbstractThis work looks at the role played by constant levels of fibre and/or particles in epoxy matrices on impact responses during dynamic loading. In order to delineate the differing roles of reinforcements, hybrid composites containing different amounts of fibres and particles were prepared. Maximum loads and energies were used to distinguish the responses during and following impact. Scanning electron microscopy (SEM) was used to characterize the surface features before and after failure. Furthermore, such microscopic analyses were also employed to substantiate the deductions arrived at based on mechanical data analysis, which included the deduced parameter in the form of energy for propagation. The experimental results pointed to the fact that the total energy and load generally rise as the fibre content in the epoxy system increases. The hybrids, on the other hand, displayed a trend where the normalized load and the total energy increased as the fibre content in the hybrid was raised from 1 to 5 vol%. This was most evident when the differing levels of fillers and fibres were fixed at a total of 7 vol%. In addition, comparison was made between two sets of compositions of fibres and particles in the composites. The results showed that the higher fibre content in the hybrid allowed greater load bearing and energy absorption and the difference in recorded levels increased with higher fibre content in one hybrid set. Fractography studies indicated flatter surface features for systems with only particles added, whereas the ‘all‐fibre’ bearing systems displayed ‘fast‐fracture’ features resembling ‘river patterns’. Copyright © 2004 Society of Chemical Industry
Crystallization and melting behavior of polyester/clay nanocomposites
Authors: Phang In Yee , Pramoda KP , Liu Tianxi , He Chaobin 
Published: June 2004

AbstractPolyester/clay nanocomposites were prepared by melt compounding with different clay loadings. Comparing against neat polyester resins, the crystallization and multiple melting behavior of the nanocomposites was investigated by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). Nanoclay filler is an effective heterogeneous nucleating agent, as evidenced by a decrease and an increase in the crystallization temperature for both cold and melt crystallization of polyesters, respectively. The degree of crystallinity was found to increase with increasing clay content, due to heterogeneous nucleation effects by the addition of a nanofiller. For the annealed samples, multiple melting peaks were always observed for both neat polyester and its nanocomposites. The origins of the multiple melting behavior are discussed, based on the DSC and XRD results. Interestingly, an ‘abnormal’ high‐temperature endothermic peak (Tm, 3) at about 260 °C was observed when the nanocomposite samples were annealed at higher temperatures (eg ≥240 °C). The constrained polyester crystals formed within intercalated clay platelets due to confinement effects were probably responsible for this melting event at these higher temperatures. Copyright © 2004 Society of Chemical Industry
Intraply and interply hybrid composites based on E‐glass and poly(vinyl alcohol) woven fabrics: tensile and impact properties
Authors: Pegoretti Alessandro , Fabbri Elena , Migliaresi Claudio , Pilati Francesco 
Published: June 2004

AbstractE‐glass and poly(vinyl alcohol) (PVA) fibres were used to produce both homogeneous and hybrid composites with an orthophthalic unsatured polyester resin. Results are presented regarding the tensile and impact behaviour of both intraply and interply hybrid composites, with particular regard to the effects of the plies stacking sequence and the loading direction. With a proper choice of composition and stacking sequence, E‐glass/PVA hybrid composites were proved to achieve a property profile superior to those of homogeneous E‐glass laminates in terms of specific properties. In particular, hybridization with PVA fibres resulted in improving the specific impact energy of E‐glass laminates. Resistance to impact crack propagation was higher for intraply with respect to interply hybrid composites, as evidenced by their ductility index values. Copyright © 2004 Society of Chemical Industry
Formation of a soluble hyperbranched polymer via initiator–fragment incorporation radical copolymerization of divinyl adipate and isobutyl vinyl ether
Authors: Sato Tsuneyuki , Arima Yukiko , Seno Makiko , Hirano Tomohiro 
Published: June 2004

AbstractThe copolymerization of divinyl adipate (DVA) with isobutyl vinyl ether (IBVE) was conducted at 70 and 80 °C in benzene using azobisisobutyronitrile (AIBN), at a concentration as high as 0.50 mol l−1 as the initiator, where the concentrations of DVA and IBVE were 0.40 and 0.60 mol l−1, respectively. The copolymerization proceeded homogeneously, without any gelation, to yield soluble copolymers in spite of the high molar ratio of DVA as an excellent cross‐linker for IBVE. The copolymer yield increased with time, and the number‐average molecular weight (Mn = 0.9–2.4 × 104 g mol−1) from gel permeation chromatography (GPC) and molecular weight distribution (Mw/Mn = 1.5–7.6) of the resulting copolymer increased with copolymer yield. The cyanopropyl group, as a fragment of AIBN, was incorporated as a main constituent in the copolymer, the fraction of which increased from ca 10 to ca 20 % with copolymer yield, hence indicating that the copolymerization is an initiator–fragment incorporation radical polymerization. The copolymers also contained IBVE units (10–30 %) and DVA units with intact double bond (8–36 %) and without double bond (45 %). The intrinsic viscosity of the copolymer was very low (0.1 dl g−1) at 30 °C in tetrahydrofuran. The results from GPC–multi‐angle laser light scattering (MALLS), transmission electron microscopy (TEM) and MALLS revealed that individual copolymer molecules were formed as hyperbranched nanoparticles. Copyright © 2004 Society of Chemical Industry
Polyurethane ionomer dispersions from a blocked aromatic‐diisocyanate prepolymer
Authors: Subramani S , Park Young‐Jun , Cheong In‐Woo , Kim Jung‐Hyun 
Published: June 2004

AbstractAqueous anionic blocked aromatic polyurethane prepolymers were synthesized by a prepolymer mixing process and their dispersions were obtained by adding water to the blocked prepolymer solutions. A series of prepolymers were prepared by using toluene 2,4‐diisocyanate, 4,4′‐diphenylmethane diisocyanate, polytetramethylene glycol, dimethylol propionic acid, methyl ethyl ketoxime and ε‐caprolactam. The aqueous dispersions were characterized by Fourier‐transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. The particle sizes, viscosities, pH and storage stabilities of the dispersions were studied and compared. Some mechanical properties of the cast films obtained from the aqueous dispersions and the adhesive properties of the dispersions were also evaluated. Copyright © 2004 Society of Chemical Industry
Identification of rheological and structural characteristics of foamable poly(ethylene terephthalate) by reactive extrusion
Authors: Xanthos M , Wan C , Dhavalikar R , Karayannidis GP , Bikiaris DN 
Published: June 2004

AbstractThe reactivity and efficiency of five low molecular weight multifunctional anhydride and epoxy compounds as chemical modifiers of a bottle grade poly(ethylene terephthalate) (PET) resin were evaluated by reactive extrusion under controlled conditions. The two dianhydrides and the three epoxy compounds were used at concentrations based on stoichiometry derived from the measured carboxyl and hydroxyl end group contents of the base resin. Measures of melt viscosity, melt strength, intrinsic viscosity and carboxyl group content were used as criteria of the extent of the modification. Correlations of die pressure with extrudate swell during extrusion, and melt flow index (MFI) with melt strength by off‐line testing of the extrudates permitted the ranking of the modifiers according to their chain‐extending/branching efficiency. For some systems molecular weight increases (related to die pressure/MFI/intrinsic viscosity) accompanied by broadening of the molecular weight distribution (related to die swell/melt strength) were considered excessive. Extrusion foaming experiments with one particular dianhydride modifier that increased the intrinsic viscosity of the resin from 0.71 to 0.9 dl g−1 indicate that production of low‐density foams by a process involving one‐step reactive modification/gas injection foaming is feasible, at conditions not significantly different from those employed in the simple reactive modification of the PET resin. The rheological and structural parameters determined in this work may be used as criteria to specify PET foamable compositions in terms of types and concentrations of modifiers. Copyright © 2004 Society of Chemical Industry
Chain structure of polyethylene/polypropylene in‐reactor alloy synthesized in gas phase with spherical Ziegler–Natta catalyst
Authors: Fu Zhisheng , Fan Zhiqiang , Zhang Yanzhong , Xu Junting 
Published: June 2004

AbstractTwo polyethylene/polypropylene (PE/PP) in‐reactor alloy samples were synthesized by multi‐stage gas‐phase polymerization using a spherical Ziegler–Natta catalyst. The alloys show excellent toughness and stiffness. FTIR, 13C‐NMR and thermal analysis proved that the alloys are mainly composed of polyethylene, PE‐block‐PP copolymer and polypropylene. There are also a few percent of ethylene‐propylene segmented copolymer with very low crystallinity. The block copolymer fraction accounts for more than 25 % of the alloy. The role of the block copolymer as compatibilizer between PE and PP is believed to be the key factor that results in the excellent toughness–stiffness balance of the material. Copyright © 2004 Society of Chemical Industry
Implications of melt compatibility/incompatibility on thermal and mechanical properties of metallocene and Ziegler–Natta linear low density polyethylene (LLDPE) blends with high density polyethylene (HDPE): influence of composition distribution and branch content of LLDPE
Authors: Hussein Ibnelwaleed A 
Published: June 2004

AbstractIn this paper, the implications of melt compatibility on thermal and solid‐state properties of linear low density polyethylene/high density polyethylene (LLDPE/HDPE) blends were assessed with respect to the effect of composition distribution (CD) and branch content (BC). The effect of CD was studied by melt blending a metallocene (m‐LLDPE) and a Ziegler‐Natta (ZN) LLDPE with the same HDPE at 190 °C. Similarly, the effect of BC was examined. In both cases, resins were paired to study one molecular variable at a time. Thermal and solid‐state properties were measured in a differential scanning calorimeter and in an Instron mechanical testing instrument, respectively. The low‐BC m‐LLDPE (BC = 14.5 CH3/1000 C) blends with HDPE were compatible at all compositions: rheological, thermal and some mechanical properties followed additivity rules. For incompatible high‐BC (42.0 CH3/1000 C) m‐LLDPE‐rich blends, elongation at break and work of rupture showed synergistic effects, while modulus was lower than predictions of linear additivity. The CD of LLDPE showed no significant effect on thermal properties, elongation at break or work of rupture; however, it resulted in low moduli for ZN‐LLDPE blends with HDPE. For miscible blends, no effect for BC or CD of LLDPE was observed. The BC of LLDPE has, in general, a stronger influence on melt and solid‐state properties of blends than the CD. Copyright © 2004 Society of Chemical Industry
A study of the products and mechanism of the thermal oxidative degradation of poly(ethylene oxide) using 1H and 13C 1‐D and 2‐D NMR
Authors: Mkhatresh Omar A , Heatley Frank 
Published: June 2004

AbstractThe products and mechanism of the thermal oxidative degradation of poly(ethylene oxide) at 150 °C have been analysed using 1H and 13C 1‐D and 2‐D NMR spectroscopy, including COSY, HMQC, HMBC and DOSY techniques. Peaks from methanoate ester chain ends (in the majority), in‐chain esters, peroxy groups, acetal links and ethanoyl chain ends have been assigned. Two small molecule degradation products, 2‐hydroxyethyl methanoate and ethylene glycol dimethanoate have been identified. Copyright © 2004 Society of Chemical Industry
Effect of acids on in situ polyaniline film formation
Authors: Ayad MM , Sheneshin MA 
Published: June 2004

AbstractThe chemical oxidation of aniline with ammonium persulfate (APS) to form polyaniline (PANI) films has been studied in different aqueous acid media such as sulfuric, nitric, phosphoric and acetic acids. A comparison was made between the yields of PANI film deposition during the polymerization from these media with the corresponding one obtained previously from aqueous HCl solution. The degradation of the formed PANI films at the beginning of polymerization obtained at the higher concentrations of HCl is absent when the other acids under consideration were used. The effect of acid concentration on the yield and growth rate of the PANI film was studied. The variation in the yield and growth rate of the polymer films at different acid concentrations was explained on the basis of the electrostatic repulsion and the screening effects. Copyright © 2004 Society of Chemical Industry
Effects of epoxy content on dynamic mechanical behaviour of PEI‐toughened dicyanate–novolac epoxy blends
Authors: Guo Baochun , Jia Demin 
Published: June 2004

AbstractBy varying the cyanate/epoxy ratio, three polyetherimide(PEI)‐modified bisphenol A dicyanate–novolac epoxy resin blends with different epoxy contents were prepared. The effects of epoxy content on the dynamic mechanical behaviour of those blends were investigated by dynamic mechanical thermal analysis. The results showed that the glass transition temperature of the cyanate–epoxy network (Tg1) in the modified blend decreases with epoxy content. When the epoxy content increases, both the width of the glass transition of the cyanate–epoxy network and its peak density are depressed substantially. Although the tangent delta peak value of PEI is basically independent of epoxy content, the Tg of PEI (Tg2) decreases with epoxy content. Tg1 is independent of the PEI loading. When Tg1 is lower than Tg2, however, the Tg1 in the blend with revised phase structure is substantially lower than other blends. Copyright © 2004 Society of Chemical Industry
pH and salt effects on interpolymer complexation via hydrogen bonding in aqueous solutions
Authors: Khutoryanskiy Vitaliy V , Mun Grigoriy A , Nurkeeva Zauresh S , Dubolazov Artem V 
Published: June 2004

AbstractThe effect of inorganic salts addition on the complex formation of poly(acrylic acid) with various non‐ionic polymers such as poly(vinyl pyrrolidone), poly(acrylamide), poly(ethylene oxide), pol(vinyl methyl ether), poly(vinyl alcohol), poly(N‐isopropylacrylamide), poly(2‐hydroxyethyl vinyl ether), hydroxypropylcellulose and hydroxyethylcellulose has been studied in aqueous solutions. It was found that, depending on the nature of the polymers and pH medium, addition of inorganic salts could increase or decrease the critical pH values of complexation. A new classification of interpolymer complexes based on critical pH values and ionic strength effects is suggested. Copyright © 2004 Society of Chemical Industry
Synthesis and characterization of poly(p‐phenylene)‐graft‐poly(ε‐caprolactone) copolymers by combined ring‐opening polymerization and cross‐coupling processes
Authors: Yurteri Seda , Cianga Ioan , Degirmenci Mustafa , Yagci Yusuf 
Published: June 2004

Abstract2,5‐Dibromo‐1,4‐(dihydroxymethyl)benzene was used as initiator in ring‐opening polymerization of ε‐caprolactone in the presence of stannous octoate (Sn(Oct)2) catalyst. The resulting poly(ε‐caprolactone) (PCL) macromonomer, with a central 2,5‐dibromo‐1,4‐diphenylene group, was used in combination with 1,4‐dibromo‐2,5‐dimethylbenzene for a Suzuki coupling in the presence of Pd(PPh3)4 as catalyst or using the system NiCl2/bpy/PPh3/Zn for a Yamamoto‐type polymerization. The poly(p‐phenylenes) (PPP) obtained, with PCL side chains, have solubility properties similar to those of the starting macromonomer, ie soluble in common organic solvents at room temperature. The new polymers were characterized by 1H and 13C NMR and UV spectroscopy and also by GPC measurements. The thermal behaviour of the precursor PCL macromonomer and the final poly(p‐phenylene)‐graft‐poly(ε‐caprolactone) copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry analyses and compared. Copyright © 2004 Society of Chemical Industry
Preparation and properties of new thermally stable poly(ether imide amide)s
Authors: Mehdipour‐Ataei Shahram , Amirshaghaghi Ahmad 
Published: June 2004

Abstract2,6‐Bis(4‐aminophenoxy)pyridine was prepared via reaction of 4‐aminophenol with 2,6‐dichloropyridine in the presence of potassium carbonate. Reaction of the diamine with two mol of trimellitic anhydride afforded a diacid with preformed imide structures. Poly(ether imide amide)s were prepared by polycondensation reactions of the diacid with different diamines in the presence of triphenyl phosphite. All the monomers and polymers were fully characterized and the physical properties of the polymers including solution viscosity, thermal stability, thermal behavior and solubility were studied. Thermal analysis data showed the polymers to have high thermal stability. Copyright © 2004 Society of Chemical Industry
Characteristics of ethylene propylene diene monomer rubber/organoclay nanocomposites resulting from different processing conditions and formulations
Authors: Gatos Konstantinos G , Thomann Ralf , Karger‐Kocsis József 
Published: June 2004

AbstractSeveral parameters which affect the nanocomposite formation in a sulfur‐cured ethylene propylene diene rubber (EPDM) containing 10 phr organoclay (montmorillonite modified with octadecylamine; MMT–ODA), were investigated. The parameters varied were linked to processing (mixer type, temperature) and rubber recipe (compatibilizer, accelerator). Increasing temperature and high shear mixing (internal mixer instead of open mill) improved the mechanical performance of the rubber nanocomposites. A more pronounced effect was achieved by using polar EPDM rubbers (maleic anhydride and glycidyl methacrylate grafted version) as compatibilizer. Among the accelerators, zinc diethyldithiocarbamate proved to be most suitable. The microstructure of the rubber/organoclay systems was studied by X‐ray diffraction, transmission electron microscopy and scanning electron microscopy. Organoclay intercalation/exfoliation was accompanied by its more or less severe confinement (reaggregation, deintercalation). This was traced to a partial or full removal of the ODA intercalant from the clay galleries via the formation of a zinc complex in which amine groups of the ODA and sulfur participated. Copyright © 2004 Society of Chemical Industry
Preparation and properties of a novel high‐performance resin system with low injection temperature for resin transfer moulding
Authors: Gu Aijuan , Liang Guozheng 
Published: June 2004

AbstractA novel high‐performance resin system with low injection temperature for resin transfer moulding, M4506, was developed, which was made of 4,4′‐bismaleimidodiphenylmethane, o,o′‐diallyl bisphenol A, o,o′‐diallyl bisphenol A ether, and 1,1′‐bis(4‐cyanatophenyl)ethane. The processing characteristics, thermal and mechanical properties of the system were studied, and the effect of differing stoichiometries of each component on the processing and performance parameters was discussed. Investigations show that the processing properties of the M4506 system are greatly dependent on the stoichiometries of each component in the formulations, while all the three formulations developed in this paper have good processing characteristics, their suitable injection temperature are between 40 and 50 °C, depending on their respective formulation. The three formulations exhibited outstanding heat resistance (Tg = 294–300 °C) and thermal stability, good toughness and high strength, evidence that the M4506 system is a potential candidate as a high‐performance RTM matrix for advance composites as well as high‐performance paints with no solvents. Copyright © 2004 Society of Chemical Industry
Grafting of dodecyl methacrylate onto hydroxylated polybutadiene by miniemulsion polymerization
Authors: Pham Thi Thuy Binh , Fellows Christopher M. , Gilbert Robert G. 
Published: June 2004

AbstractHomogeneous copolymer latex particles of dodecyl methacrylate (DMA) and low‐molecular‐weight hydroxy‐terminated polybutadiene (HTPB) oligomers were prepared by free‐radical polymerization using miniemulsion methods. Rate data and latex characteristics were consistent with the classical miniemulsion mechanism where nucleation of monomer droplets is the predominant pathway of particle formation. There is essentially no particle formation by secondary nucleation in the water phase. Characterization of the copolymer latex particles using transmission electron microscopy and modulated differential scanning calorimetry suggested that there is a significant amount of grafted poly(DMA)/HTPB polymer contributing to the miscibility of the HTPB and poly(DMA) phases. Particles were more homogeneous at increased HTPB composition, of relatively narrow polydispersity, and could be prepared reproducibly using a number of different initiation systems. The observed trends can all be rationalized in terms of conventional understanding of miniemulsion polymerization systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3404–3416, 2004
Stereospecific polymerization of methacrylates by metallocene and related catalysts
Authors: Chen Eugene Y.‐X. 
Published: June 2004

AbstractStereospecific—isospecific, syndiospecific, and diastereospecific—polymerizations of methacrylates using group 4 metallocene and related catalysts produce polymethacrylates with controlled stereo‐microstructures. The versatility and stereospecificity of these cat‐ alysts for methyl methacrylate polymerization were demonstrated not only in solution‐phase polymerization, but also in polymerizations on silica surfaces and inside silicate nanogalleries. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3395–3403, 2004