bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incompatible ternary blends based on unsaturated polyester resins. I. Phase diagrams
Authors: Suspene L. , Pascault J. P. 
Published: April 2003

AbstractWe have determined pseudo ternary phase diagrams for blends based on unsaturated polyester resins and an elastomeric additive. Size exclusion chromatography analysis is a well‐known method for quantifying the demixed phase composition in the case of isomolecular polymers. But when some fractionation occurs, our results show that this analysis becomes inapplicable. In our systems, due to the presence of nitrogen atoms in the elastomer, elemental analysis has been used, and, with the help of the percent of styrene, this leads to the determination of the pseudo ternary phase diagrams. The major cause of this fractionation is the high polydispersity of the UP prepolymer. Lowering the molecular weight of the UP prepolymer leads to a partial miscibility with styrene. This unexpected phenomenon may be attributed to a chain‐end effect rather than a real molecular weight effect. Finally, we have defined a compatibility window between 1–3 or 1–7 phr of elastomer, where the solutions are two‐phase systems but without any sedimentation processes, even after several weeks. This compatibility window is certainly limited by binodal and spinodal curves. The higher limit, 3–7 phr of elastomer, depends strongly on the type of chain ends (hydroxyl or carboxyl) of the UP prepolymer.
The β‐crystalline form of wollastonite‐filled polypropylene
Authors: Jingjiang Liu , Xiufen Wei , Qipeng Guo 
Published: April 2003

AbstractA study has been made of the thermal, X‐ray diffraction, and dynamic mechanical characteristics of polypropylene (PP1330, a copolymer containing 22% ethylene) filled with wollastonite. Various levels of β‐form crystallinity were produced in the PP by mixing in varying amount of wollastonite. It has been found that all the wollastonite‐filled samples contain both the α‐and the β‐forms, and four melting transitions were observed instead of only two of the unfilled PP on the DSC scan. The conversion of the β‐to the β‐form on heating has been observed. The relative amount of the β‐form in the samples was measured from WAXS data by the K value. The K value obtained increases with increasing wollastonite content. Dynamic mechanical measurements showed an increase in the magnitude of the damping in the high‐temperature region for the wollastonite‐filled PP and the contribution from the filler‐matrix boundary. Wollastonite acted as both a reinforcement and a β‐nucleator for PP.
The effect of crosslinking on properties of polyurethane elastomers
Authors: Petrović Zoran S. , Ilavský Michal , Dus̆ek Karel , Vidaković Mladen , Javni Ivan , Banjanin boz̆o 
Published: April 2003

AbstractA series of segmented polyurethanes from two polyols, 4,4′‐diphenylmethane diisocyanate (MDI) and butane diol was synthesized. The degree of chemical crosslinking was controlled by varying the ratio of poly(oxypropylene) diol to poly(oxypropylene/oxyethylene) triol. The samples were prepared at the stoichiometric ratio of NCO to OH groups and at a constant concentration of hard segments (butane diol; MDI) equal 50 wt %. At low concentrations of the triol the molecular weight of the polyurethanes increases; at higher concentrations (above 9 mol %) crosslinked products are obtained. All samples show a distinct two‐phase structure and in the region of 0–150°C the dynamic mechanical behavior is affected by the hard phase. Chemical crosslinking was found to increase the tensile strength and strain at break, but did not affect appreciably the tear strength, hardness, and soft segment glass transition. The stress relaxation rate at room temperature was found to depend both on the elongation and on the degree of crosslinking. A comparison of the sol fractions ws found for crosslinked samples with the predictions of the theory of branching processes proved that the achieved conversions of reactive groups in networks are high (∼ 0.98).
Determination of the composition of common linear low density polyethylene copolymers by 13C‐NMR spectroscopy
Authors: De Pooter M. , Smith P. B. , Dohrer K. K. , Bennett K. F. , Meadows M. D. , Smith C. G. , Schouwenaars H. P. , Geerards R. A. 
Published: April 2003

AbstractA comprehensive 13C‐NMR method for the analysis of composition in the most common commercial polyethylene copolymers has been established. The method covers ethene copolymers with propene, butene‐1, hexene‐1, octene‐1, and 4‐methyl pentene‐1 in the composition range of 1–10 mol %. The chemical shift assignments and T1 values of the resonances of the copolymers are presented. Results of precision studies and interlaboratory analyses showed that the molar composition could be determined with a relative precision at 2δ of about 6%. This method is being proposed to ASTM as Method X70‐8605‐2.
Rheological properties of polypropylene/high‐density polyethylene blend melts. I. Capillary flow properties
Authors: Fujiyama Mitsuyoshi , Kawasaki Youtoku 
Published: April 2003

AbstractThree kinds of isotactic polypropylenes (PP) with different melt flow indexes (MFIs) were melt‐blended with three kinds of high‐density polyethylenes (HDPE) with different MFI using a screw extruder, and the morphologies and capillary flow properties such as flow curve, entrance effect, Barus effect, and melt fracture were studied. When HDPE contents were 70 wt % or above and PP particles formed the disperse phase, the size of the particles decreased with decreasing viscosity of PP. When HDPE contents were 30 wt % or below and HDPE particles formed the disperse phase, the size of the particles was minimum when the viscosities of PP and HDPE were similar. The die swell ratios of the blends were higher than those of the components. On the other hand, the entrance correction coefficients of the blends were intermediate between those of the components. There was no correlation between the die swell ratio and the entrance corretion coefficient. Therefore, it is not always appropriate to regard the entrance correction coefficient as a measure of melt elasticity in the case of inhomogeneous polymer systems such as PP/HDPE blend.
Dynamic mechanical analysis of fibers. II. Estimation of fiber orientation and characterization of heat set PET yarns
Authors: Khanna Y. P. , Taylor T. J. , Kumar R. 
Published: April 2003

AbstractA drawn PET yarn was heat set (annealed) at temperatures between 110°C and 245°C in an unconstrained mode and the samples characterized by dynamic mechanical analysis (DMA). A method for estimating the fiber orientation factor (α) is proposed using DMA and shown to be more sensitive than the crystalline orientation (x‐ray diffraction) or total orientation (birefringence) measurements of the heat set yarns. The extension/shrinkage behavior of the heat set yarns has been discussed in the light of morphological changes, e.g., degree of orientation and the micro‐crystallite formation. Unlike in the unconstrained mode, heat setting under constraint does not lead to the formation of micro‐crystallites as revealed by differential scanning calorimetry. As a consequence, although the modulus and degree of orientation increase upon constrained annealing, the thermal stability, i.e., loss of orientation (reflected by shrinkage) could not be improved.
Correlation of binder mechanical properties with microstructure for poly(butadiene–acrylonitrile–methacrylic acid) terpolymer: 13C‐NMR and pyrolysis‐GC studies
Authors: Rao M. Rama , Sebastian T. V. , Radhakrishnan T. S. , Ravindran P. V. 
Published: April 2003

Abstract13C‐NMR spectroscopy (22.5 MHz) was used to characterize poly(butadiene (B)–acrylonitrile (A)–methacrylic acid (M)) liquid terpolymers prepared by emulsion polymerization. The sequence distribution of the monomers in the terpolymers was described in terms of triads BBB, ABA, ABB, BBA, MBB, and AMB and was found to vary with the mode of addition of methacrylic acid monomer. The NMR data was found to be in good agreement with a mechanism of polymerization in which methacrylic acid is preferentially involved in initiation reactions by a thiyl radical arising from the reaction of the chain modifier, 1‐dodecanethiol, and cyanoisopropyl radical generated from AIBN initiator. Binders obtained by curing the liquid terpolymers with an epoxy resin showed widely varying mechanical properties with tensile strength varying from 4.3 to 0.6 kg/cm2 and elongation at break from 130 to 450%. It was found that tensile strength increases and elongation decreases with the number of acrylonitrile units between the methacrylic acid crosslinks. Good correlation was obtained between triad population ratio [ABB + BBA] [BBvB]/[ABA][MBB] and the mechanical properties of the binders. Pyrolysis‐GC data at 550 and 600°C confirmed the results obtained from 13C‐NMR, and the mole ratio of butadiene to arylonitrile in the pyrolyzates showed correlation with the properties of binders.
Hydroxypropylmethylcellulose–anionic surfactant interactions in aqueous systems
Authors: Alli Dhananjaya , Bolton Sanford , Gaylord Norman G. 
Published: April 2003

AbstractThe increase in the viscosity of an aqueous solution or gel of hydroxypropylmethylcellulose (HPMC) in the presence of an anionic surfactant is attributed to a two‐step process: (a) the surfactant undergoes ion–dipole interaction with the ethereal oxygen in HPMC, in the absence or presence of water, and (b) hydrocarbon moieties in the now pendant surfactant molecules undergo hydrophobic bonding, in the presence of water, resulting in an apparent increase in the molecular weight of the HPMC. DSC of dry blends and dried gels or films confirmed HPMC–sodium lauryl sulfate interaction. Work‐to‐break measurements on films cast from aqueous solutions of HPMC, in the absence or presence of anionic surfactants, indicated an apparent increase in the molecular weight of HPMC in the presence of surfactants.
Structure–properties relations of thermally cured epoxy–lignin polyblends
Authors: Feldman D. , Banu D. , Natansohn A. , Wang J. 
Published: April 2003

AbstractA bisphenol A based epoxy adhesive (EP) was modified by polyblending with Kraft Lignin (L). A systematic investigation of the thermally cured EP‐L polyblends with up to 40% by weight L was undertaken. Adhesive shear tests, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and solid‐state CP‐MAS NMR spectroscopy were performed to establish the effect of L on the mechanical properties of the polyblends and on the morphology of these crosslinked structures. The possibility of an enhanced degree of bonding between L and the EP network is discussed. This bonding can arise from a chemical reaction between L and some unreacted amine groups present in the hardener.
Synthesis and structure–property relationships of UV‐curable urethane prepolymers with hard–soft–hard blocks
Authors: Lai Yu‐Chin , Baccei Louis J. 
Published: April 2003

AbstractUV‐curable urethane prepolymers derived from diisocyanates, rigid diols, and polypropylene glycols of different molecular weights and end‐capped with 2‐hydroxylethyl methacrylate were prepared by stepwise addition reactions. These prepolymers have the common structure, HEMA‐hard segment‐soft segment‐hard segment‐HEMA. As the weight ratio of soft segment to hard segment and thus the rigidity varied, the cured films from these prepolymers exhibited a wide range of mechanical and other key properties such as oxygen permeability.
Characterization of cationic water‐soluble polyacrylamides
Authors: Vu Can , Cabestany Jean 
Published: April 2003

AbstractCopolymers of poly(acrylamide‐co‐acryloyloxyethyltrimethylammonium chloride or AM–CMA) and poly(acrylamide‐co‐methacryloyloxyethyltrimethylammonium chloride or AM–CMA) prepared by inverse emulsion polymerization were characterized by different analytical techniques. The chemical composition of the copolymers was estimated by elemental analysis and by nuclear magnetic resonance spectroscopy (NMR). NMR spectroscopy and computer simulation were further used for investigating the polymers' sequence distribution. The poly(AM–CMA) copolymers are chemically more homogeneous than are the poly(AM–CMA). The configurational propagation of dyads and triads for the homopolymers obeys Bernouilli's statistics. For the copolymers, the chemical sequences distribution is governed by Markov's first‐order statistics.
Synthesis of graft polyesters by ring‐opening copolymerization of epoxy‐terminated poly(ethylene glycol) with acid anhydrides
Authors: Ikeda Isao , Simazaki Yoshitomo , Suzuki Kimihiro 
Published: April 2003

AbstractThe copolymerization of epoxy‐terminated poly(ethylene glycol methyl ether) (CH3PEG–epoxide) with phthalic anhydride catalyzed by tertiary amines was performed in o‐dichlorobenzene at 100°C to prepare the PEG graft polyester. 4‐Dimethylaminopyridine was the most favorable catalyst to give the graft polyester with relatively high molecular weight. The acidity of the reaction solution decreased and Mn of the graft polyesters increased with reaction time. The CH3PEG/phthalic acid ratio of the products was little affected by the kind of solvent and the reaction temperature above 100°C, but Mn increased with lowering the polarity of solvents and with raising the temperature. Other acid anhydrides, including maleic, succinic, tetrahydrophthalic, and pyromellitic anhydride, could be copolymerized with CH3PEG–epoxide. The number of branched CH3PEG chains was controlled by the mixing of low molecular weight epoxide such as n‐butyl glycidyl ether. CH3PEG component of the graft copolymers melted and crystallized at lower temperature than the raw CH3PEG because of the restriction on the trunk polyester chain.
On the stability and in situ epoxidation of natural rubber in latex by performic acid
Authors: Bac Nguyen Viet , Terlemezyan Levon , Mihailov Marin 
Published: April 2003

AbstractThe aggregative stability of natural rubber (NR) latex stabilized by nonionic, fatty alcohol ethylene oxide condensate surfactant (Verol S‐15) was studied in the presence of formic acid. Natural rubber latex having an additional 3–5 phr surfactant is stable at pH 2 when acidified by formic acid and can be successfully subjected to the subsequent in situ epoxidation. Using a large ratio of H2O2 to isoprene unit (0.4–4.0 M/M) and large excess of H2O2 to HCOOH (3–13 M/M) in reaction, the in situ epoxidation can be performed with reaction mixture having dry rubber content up to 35–37% at room temperature or up to 28% at 50°C. This reaction leads to products of large range of epoxide contents and characterized by absence of side‐ring opening groups, proved by IR and 1H‐NMR analysis. By infrared spectroscopy it was demonstrated a good correlation between the absorbances of the residual double bonds and of the epoxide groups versus the epoxide content in the range from 0 to approx. 60 mol % level. The solubility and gel content were studied in various solvents, demonstrating that epoxidation leads to increasing gel content at high epoxide levels and to enhancing sensitivity of the product toward polar solvents. By GPC, it was shown for the soluble fraction that epoxidation was accompanied by reducing the molecular weight and by change of the MWD compared with the original NR.
Separation of water–ethanol by pervaporation through polyion complex composite membrane
Authors: Karakane H. , Tsuyumoto M. , Maeda Y. , Honda Z. 
Published: April 2003

AbstractFor the purpose of separating alcohol–water mixtures by the use of the pervaporation technique, new composite membranes composed of polyion complexes (PIC) as a separating layer were developed. The polyion complex structure, consisting of polyacrylic acid (PAA) and polycation, provided excellent permeation rate and selectivity. Among the polycations, ionenes, which have quaternary ammonium groups in the backbone chain, were effective in giving membranes of higher permselectivities. High selectivity of PIC membranes was observed at high ethanol concentration regions in the feed mixture. For the azeotropic mixture of water/ethanol (95 wt % EtOH) at 60°C, the PAA‐based PIC membrane had the following separation properties: separation factor ∼ 3,500 and permeation rate ∼ 1.6 kg/m2 h.
Dynamic mechanical and calorimetric analysis of compression‐molded PLLA of different molecular weights: Effect of thermal treatments
Authors: Migliaresi C. , Cohn D. , De Lollis A. , Fambri L. 
Published: April 2003

AbstractThe effect of thermal treatment on compression‐molded poly(L‐lactic acid) (PLLA) has been investigated by means of viscosimetric molecular weight (\documentclass{article}\pagestyle{empty}\begin{document}$$M_{w_v}$$\end{document}) determination, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). Starting from two initial molecular weight PLLAs, amorphous samples with different \documentclass{article}\pagestyle{empty}\begin{document}$$M_{w_v}$$\end{document} have been obtained due to degradation occurring during the molding. The crystallization capability of the materials after different thermal treatments has been determined as a function of the molecular weight, and their dynamic mechanical properties have been measured. Initially fully amorphous PLLA matrices attained very high degrees of crystallinity (up to 90%) following different annealing processes. Concomitantly, PLLA degrades due to thermal cleavage of the chains. This is an unavoidable effect that must be taken into consideration when defining the material processing and annealing conditions. Crystallization phenomena occurring in the material during the treatment are clearly documented by DMTA.
Investigation of structural and mechanical properties of copper‐chloride‐doped nylon‐6 films. II. Elastic and viscoelastic studies
Authors: Kelkar D. S. , Bhat N. V. 
Published: April 2003

AbstractThe article reports the effect of variation in the concentration of copper chloride on the elastic and viscoelastic properties of nylon‐6 films. The elastic modulus for the film is determined using sonic velocity measurement technique. The glass transition temperatures are determined from dynamic mechanical studies with the Rheovibron. It is observed that the glass transition temperature of the doped films increases with increase in the dopant concentration. It is also observed that at low concentrations of doping (up to 1.25%) the salt acts as a plasticizer, whereas for higher concentration of doping (up to 12.5%) it acts as an antiplasticizer.
Synthesis and thermal stability of bitumen–polymer ionomers
Authors: Engel R. , Vidal A. , Papirer E. , Grosmangin J. 
Published: April 2003

AbstractRoad bitumens, when combined with polymers such as styrene‐butadiene‐styrene (SBS) block copolymers, show improved mechanical properties. The corresponding blends, however, are thermodynamically unstable, and phase separation quickly occurs at higher temperatures. A solution is proposed for improving the thermal stability of these blends: It is based on the formation of reversible, ionic interactions between the bitumen and the SBS, thereby leading to a mixed, ionomeric network. Both compounds are first chemically modified by the grafting of carboxylic acid groups, then mixed, and, finally, the available acid groups are partially or totally neutralized by adding zinc acetate dihydrate to the blends. Comparison of the thermal stability of the resulting ionomeric blends with that of the untreated blends is discussed. The use of ion‐ion interactions to enhance miscibility, which, for the first time, has been extended to bitumen–polymer systems, is shown to be a means of obtaining stable blends.
Phase separation and morphology in ethylcellulose/cellulose acetate phthalate blends
Authors: Sakellariou P. , Rowe R. C. 
Published: April 2003

AbstractThis article discusses the phase separation and morphology of ethylcellulose/cellulose acetate phthalate blended films cast from methanol/methylene chloride (50/50 v/v) solvent mixture. The solvent system has been shown to be a cosolvent for CAP and a solvent/nonsolvent for EC. The two polymers have been shown to phase separate for all blend compositions via nucleation and growth. The morphology of these systems consists of a dispersion of broad size distribution of the minor component in a matrix of the major one. The formation of two layers due to coalescence of the dispersed phases and their eventual precipitation has been observed for the middle blend compositions. Finally, the phase separation in this system is discussed in terms of the Flory–Huggins theory and changes in the solvency mechanism during film casting. Enrichment of the solvent system in methanol at relatively early stages of film casting leads to changes in the system viscosity, relative chain conformation in solution, and chain diffusion. The effect of these parameters on the final morphology are discussed in terms of deviations from the equilibrium binodal decomposition.
Permeation behavior of dextrans by charged ultrafiltration membranes of polyacrylonitrile photografted with ionic monomers
Authors: Kobayashi Takaomi , Kumagai Kazuyasu , Nosaka Yoshio , Miyama Hajime , Fujii Nobuyuki , Tanzawa Hiroshi 
Published: April 2003

AbstractCharged copolymers, polyacrylonitrile, having grafts of quaternized poly(N,N‐dimethylaminoethylmethacrylate) and poly(sodium p‐styrenesulfonate), were synthesized by photograft‐polymerization. The charged ultrafiltration membranes, which had heterogeneous porous structures, were prepared by casting graft polymer solution containing poly(vinyl alcohol) into water.The permeation of nonionic dextran and anionic dextransulfate through the charged membranes was studied by ultrafiltration in aqueous solution. The molecular weight cutoff characteristics of the charged membrances were obtained using dextrans of various molecular sizes. The permeation behavior was discussed in terms of the charge effect of the graft polymers and electrostatic interaction between the polymers and the solute molecules.
Effect of moisture on the crystallization behavior of PET from the quenched amorphous phase
Authors: Bianchi Riccardo , Chiavacci Paolo , Vosa Renato , Guerra Gaetano 
Published: April 2003

AbstractThe dependence on the moisture content of the glass transition temperature (Tg) and of the crystallization temperature from the quenched amorphous phase (Tc) for poly(ethylene terephthalate) (PET) samples is studied by differential scanning calorimetry.For low moisture contents, very large and reversible decreases of Tc but small decreases of Tg are observed. This indicates that the strong increase of nucleation rate observed for PET in the presence of moisture is not related to the plasticizing effect that produces significant Tg changes.
1H‐NMR studies on water in methacrylate hydrogels. II
Authors: Yamada‐Nosaka Atsuko , Tanzawa Hiroshi 
Published: April 2003

AbstractProperties of water in the wet membranes of a random copolymer of methyl methacrylate and methoxy poly(ethylene glycol)–monomethacrylate P(MMA‐co‐M100G) and of a graft copolymer of vinyl chloride and methoxy poly(ethylene glycol)–monomethacrylate P(VC‐g‐M100G) membranes were studied by proton NMR spectroscopy. Both polymers contain flexible polyoxyethylene side chains. Temperature and frequency dependences of relaxation times, changes of signal intensity of water protons on freezing and thawing, and saturation transfer were measured for both copolymers. These experimental results revealed that most of the bound water in these copolymers does not exist in a rigid state as suggested for the other hydrogels. The introduction of flexible hydrophilic side chains resulted in high mobility of the water molecules bound to the side chains (the apparent correlation time Tc ∼ 10−10 s). For the graft copolymer P(VC‐g‐M100G), hydrophilic polyoxyethylene side chains are contiguous to each other. Because of the interaction between the side chains, the mobility became more complex than that for the random copolymer P(MMA‐co‐M100G). The difference in the mode of mobility of water on the membrane surface may be related to the difference of the membrane characteristics of these copolymers.