bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid crystal polymer‐based blends: “Universal grade” polymers?
Authors: La Mantia F. P. , Valenza A. , Magagnini P. L. 
Published: April 2003

AbstractPolymeric materials can be easily processed with different processing operations thanks to suitable rheological properties. Melt flow index, or grade, which is a measure of the fluidity of the polymers, is the most commonly parameter used to characterize the polymers from the point of view of their melt viscosity. Injection molding requires high grade materials, whereas low grade values are best suited for extrusion. Of course, it would be no doubt of interest if single “universal grade” materials could be used for all processing operations. In this paper it is demonstrated that the blends of low grade polymers with small amounts of liquid crystal polymers can be conveniently used for all processing operations. Mechanical and thermal properties of the polymer matrix are in general retained or, in some cases, improved.
Synthetic resins. XIII. Synthesis and characterization of the resins derived from quinacetophenone/substituted benzoic acid/furfuraldehyde
Authors: Burma S. P. N. S. , Lenka S. , Nayak P. L. 
Published: April 2003

AbstractSome resins have been synthesized by reacting quinacetophenone with substituted benzoic acids and furfuraldehyde in the presence of basic catalysts. The resins have been characterized by IR spectra of the characteristic groups. The number average molecular weights of the resins have been evaluated by the conductance method. The solubility and viscosity behaviors of the resin copolymers have been determined. Cu+2, Ni+2, Co+2, Mn+2, and Mg+2 chelates have been prepared. The resins were shown to be selective ion‐exchange resins for certain metal ions. A batch equilibrium method was used for studying the selectivity of the metal ions. The thermal behavior of the resins has been determined and the values of energy of activation of the resins were computed by using the Freeman–Anderson and Broido methods. The biological assays of some of the resin copolymers were found to be highly sensitive.
Rheology, composition, and peel‐mechanism of block copolymer–tackifier‐based pressure sensitive adhesives
Authors: Nakajima N. , Babrowicz R. , Harrell E. R. 
Published: April 2003

AbstractThree samples of styrene–isoprene–styrene (S–I–S) block copolymers were chosen; copolymer A had 25% styrene, and copolymers B and C had 14% styrene. Copolymers A and B contained 20% diblock polymer and copolymer C contained 40% diblock polymer. All copolymers were mixed with a terpene type tackifier to make 56% and 48% weight tackifier concentration. These represent our model samples of pressure sensitive adhesives. The determination of tack, room‐temperature peel‐strength, and failure temperature under static shear were performed. The above results have been interpreted with the basic rheological data. The dynamic viscoelastic measurements and tensile stress–strain measurements were used. The effects of tackifier on the rubbery plateau moduli were treated with the Guth–Gold‐type equation. The implications of the deviation from the equation are discussed in terms of the connectivity between polystyrene domains and the stability of the hard domains affected by inclusion of rubber segments.
Differential scanning calorimetric study of the interaction of 2,2′‐dibenzothiazole, sulfur, zinc oxide, and stearic acid in the presence of polyisoprene
Authors: Luyt Adriaan S. 
Published: April 2003

AbstractThe interactions between mixtures of 2,2'‐dibenzothiazole (MBTS), sulfur, ZnO, and stearic acid were studied by DSC in the presence of polyisoprene (IR). In the absence of ZnO, the onset of vulcanization was at a lower temperature than in its presnece, and the crosslink densities were relatively low. ZnO as well as stearic acid did not influence the consumption of MBTS, but the amount of MBT in the sample after vulcanization increased in the presence of ZnO and still more when ZnO and stearic acid were present—the same applied for the crosslink densities. In view of these results, interaction mechanisms are proposed for the different systems.
Morphology and mechanical properties of fibers from blends of a liquid crystalline polymer and poly(ethylene terephthalate)
Authors: Li J. X. , Silverstein M. S. , Hiltner A. , Baer E. 
Published: April 2003

AbstractThe domain morphology and mechanical properties of fibers spun from blends of a thermotropic liquid crystalline polymer, Vectra A‐900, and poly(ethylene terephthalate) (PET) have been studied across the entire composition range. The PET phase was removed by etching to reveal fibrillar LCP domains in the blends of all compositions. The 0.5μm fibril appeared to be the basic structural entity of the LCP domains. A primary effect of composition was the change from discontinuous fibrils when the composition was 35 and 60% by weight LCP to continuous fibrils when the composition was 85 and 96% LCP. This transition had major ramifications on the mechanical properties: the modulus increased abruptly between 60 and 85% LCP, and a change in the fracture mode from brittle fracture to a splitting mode was accompanied by an increase in fracture strength. Different models were required to describe the mechanical properties of the discontinuous and continuous fibril morphologies. Analytic models for short aligned fibers of Nielsen, and Kelly and Tyson were applicable when the LCP fibrils were discontinuous, while modulus and strength of blend fibers with continuous LCP fibrils were discribed by the rule of mixtures.
Ultra‐high modulus isotactic polypropylene. I. The influence of orientation drawing and initial morphology on the structure and properties of oriented samples
Authors: Baranov A. O. , Prut E. V. 
Published: April 2003

AbstractThe influence of a number of factors (temperature–speed regime and the quantity of draw stages, molecular weight of a polymer, etc.) on the deformability of initial isotropic IPP and on mechanical characteristics of highly‐oriented samples, obtained in the process of a two‐stages isothermal orientation drawing, was studied. It was shown that the maximum achievable values of elastic modulus and draw ratio depended not only on the molecular weight of a polymer and the sizes of spherulites, constituting initial IPP, but on the structural organization of inner‐and interspherulite regions. Upon physical aging of initial isotropic films, irreversible structural changes take place, which result in the formation of microvoids while being drawn and in the reduction of mechanical properties of obtained material. An extremal dependence of elastic modulus and draw ratio of maximum drawn IPP samples on draw speed was discovered. A structural model, which is supposed to possesstie molecules with various degrees of tautness in amorphous layers, was proposed. Higher effectiveness of two‐stage drawing in comparison with one‐stage drawing was established. The optimum temperature–speed regime of orientation drawing, which permits the reception of highly oriented, ultra‐high modulus IPP with maximum high mechanical characteristics (elastic modulus ∼ 30–35 GPa and tensile strength ∼ 1,1 GPa), was determined.
Determination of diffusion coefficient of oxygen into polymers by using electron spin resonance spectroscopy. II. Poly(vinyl acetate)
Authors: Kaptan Yilmaz , Pekcan Önder , Güven Olgun 
Published: April 2003

AbstractElectron spin resonance spectroscopy has been used to follow the kinetics of radical decay during postirradiation oxidation of poly(vinyl acetate). The oxygen uptake of γ‐irradiated spherical poly(vinyl acetate) has been determined from changes in the intensity of the ESR signal. The diffusion coefficient (D) of oxygen determined by this technique showed an inverse relation with dose. The value of the diffusion coefficient of oxygen obtained in this study, after correcting for dose and size effects is 4.5 × 10−8 cm2/s, and is in very good agreement with the literature value of D = 5.1 × 10−8 cm2/s.
Co‐existence of ductile, semi‐ductile, and brittle fractures of polycarbonate
Authors: Chang Feng‐Chih , Chu Line‐Hwa 
Published: April 2003

AbstractThe ductile–brittle transition behavior of polycarbonate and methylmethacrylate–butadiene–styrene (MBS) elastomer modified polycarbonate has been investigated in terms of notch radius and temperature. At−40°C and 21‐mil notch radius, polycarbonate fractures in three possible modes, ductile (25%), semi‐ductile (50%), and brittle (25%). This semiductile mode fracture has never been reported previously with brittle characterization, but to a greater extent in localized shear yielding on the fracture surface and intermediate toughness. A two‐dimensional fracture mode diagram in terms of temperature and notch radius has been constructed to interpret the observed phenomena. This diagram can also predict the existence of other conditions under which the triplet fracture modes may also occur. Another unstable zone has also been identified where the fracture occurs in either ductile mode or brittle mode over a broad temperature range, instead of the narrow temperature range typically observed for polycarbonate. A model based on the excessive precrack strain just below yielding due to the greater notch radius is proposed to explain such observed semi‐ductile mode fracture.
Dielectric analysis of cellulose and its vinylic copolymers
Authors: Flaqué C. , Montserrat S. 
Published: April 2003

AbstractThe real and imaginary parts of the complex dielectric permittivity, ε′ and ε″, for some vinylic copolymers of cellulose [prepared with vinyl acetate (VA) and methyl acrylate (MA) and Ce (IV) ions as initiator ] and for cellulose were measured over a frequency band of 0.1–102 kHz and a temperature range from −40 to 100°C. In vinylic copolymers of cellulose, we observed one dielectric relaxation attributed to the α‐relaxation of the vinylic side chain grafted on cellulose. In cellulose dielectric spectra, this relaxation did not appear, but we detected one relaxation that may correspond to the β‐relaxation. For these vinylic copolymers of cellulose, the ε″ against ε′ plot gives a skewed are that closely resembles that of the Davidson–Cole model, with a broader distribution for high frequencies that shows the overlap of several relaxations in the process considered. Some differences observed between the vinylic copolymers of cellulose may be due to the composition and the length of the vinylic side chains and to the frequency of grafting on the cellulose.
Prostaglandin E1‐immobilized poly(vinyl alcohol)‐blended chitosan membranes: Blood compatibility and permeability properties
Authors: Chandy Thomas , Sharma Chandra P. 
Published: April 2003

AbstractA series of membranes are prepared by air drying thin films, which were composed of poly(vinyl alcohol) blended with chitosan [a (1 → 4)2‐amino‐2‐deoxy‐β‐D‐glucan] (PVA–Chit) in different ratios. The PVA‐blended chitosan membranes showed improved strength properties and permeability functions for low‐molecular‐weight compounds. Nonthrombogenic PVA–Chit (4 : 6) membranes were derived by immobilizing bioactive molecules like PGE1 on heparin‐modified membranes, via free radical mechanisms, by N2 plasma. This novel membrane demonstrated good permeability properties for small molecules and showed a dramatic reduction in platelet attachment. The prostaglandin E1‐immobilized substrate also indicated an increase in albumin surface attachment and a reduction in fibrinogen binding. This may be one of the parameters for a reduced platelet‐surface attachment, which may also improve the blood compatibility of the substrate. It is also postulated that the total water content of membranes need not be the prime factor governing the permeability of solutes through water‐swollen membranes. However, many other parameters govern the solute permeability, like the amount of solutes dissolved in bound water and the status of water in the polymer matrix.
Chemical and mechanical properties of methyl methacrylate‐grafted wool fiber
Authors: Elangovan V. J. , Saccubai S. 
Published: April 2003

AbstractSince it has been reported in the literature that polymer‐grafted wool fibers have better acid and alkali resistances and dye uptake, the present study was carried out using KBrO3 and substrates such as Fe (II), Co (II), cysteine, cystine, tyrosine, and urea for graft copolymerization of methyl methacrylate (MMA) onto wool. Acid and alkali resistances, dye uptake, and dry tensile strength of the resulting graft copolymers were studied.
Development of a dilatometer and its application to low‐shrink unsaturated polyester resins
Authors: Kinkelaar Mark , Lee L. James 
Published: April 2003

AbstractTwo dilatometers are presented here that were developed for the use with, but not limited to, low‐shrink unsaturated polyester resins. One of the dilatometers, made from a glass syringe and two aluminum plates, was limited to lower pressures. The other dilatometer, similar in design to the first, was made from a hydraulic cylinder and was capable of pressures to 500 psi. The dilatometers were calibrated and tested by the polymerization of styrene. Several low‐shrink unsaturated polyester resins were cured in the dilatometers and the results of these experiments are given. The interactions of volume change, rheology change, conversion, and microstructure formation were also measured. Finally, the effect of pressure was considered.
Graft copolymerization of methyl methacrylate on stone ground wood using the H2O2Fe2+ method
Authors: Huang Yifang , Zhao Bianan , Zheng Guozhen , He Shujie , Gao Jie 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate on stone ground wood (SGW) of masson pine was investigated. The effect of lignin on grafting was carefully examined The phenolic hydroxyl groups of lignin were found to accelerate the decomposition of hydrogen peroxide and graft copolymerization of lignocellulose when minor ferrous ions were added to the system. Nevertheless, the α‐hydroxyl groups of lignin had no great influence on grafting. Also, the graft copolymerization could be initiated with low ferrous ions to the hydrogen peroxide molar ratio, and, additionally, the lignin was observed to be more suitable for grafting than was the hollocellulose.
Studies on mechanical properties of polyethylene–organic fiber composites. I. Nut shell flour
Authors: Raj R. G. , Kokta B. V. , Nizio J. D. 
Published: April 2003

AbstractComposites were made from polyethylene and an organic fiber (pecan shell and peanut hull flour) using a compression‐molding technique. Studies of variations in molding temperature (145–180°C), fiber concentration (0–40% by weight), and fiber mesh size (100, 200, and 325) were correlated to the mechanical properties of the composites (tensile strength, elongation, fracture energy, modulus, and impact strength). In untreated nut shell composites, tensile strength decreased steadily as the fiber concentration increased. This was due to poor bonding between the untreated fiber and polymer. Polyisocyanate was used as a coupling agent and its effect on mechanical properties of the composites was studied. Significant improvement in tensile strength was achieved with an isocyanate coupling agent, but it had no effect on modulus of the composites. Both untreated and isocyanate‐treated composites had lower impact strength values; further composite matrix modifications would be necessary to maintain or improve impact strength.
Determination of Mark–Houwink constants for polystyrene and polyacrylonitrile terpolymers
Authors: Dayal Umendra 
Published: April 2003

AbstractMark–Houwink constants of polystyrene and polyacrylonitrile terpolymers containing acrylonitrile, methyl acrylate, and styrene sulfonic acid or methallyl sulfonic acid as the third comonomer have been calculated from gel permeation chromatography (GPC) and viscosity data. The data have been used to determine molecular weights of polyacrylonitrile terpolymers.
Studies of physico–mechanical properties of wood and wood plastic composite (WPC)
Authors: Khan Mubarak Ahmad , Ali K. M. Idriss 
Published: April 2003

AbstractAn attempt has been made to improve the quality of low grade wood through radiation induced wood plastic composite (WPC) formation in order to use these low grade woods as substitutes for high grade wood. Six kinds of local woods of Bangladesh (simul, korai, mango, jack fruit, teak, and garjon) were investigated. Both soft and hard wood varieties of these were selected. Ten vinyl monomers were used for the WPC. Improvement in the quality of wood was ascertained by determining change in physico—mechanical properties of wood. These properties were tensile strength, Young's modulus, and dimensional stability. Among all the woods investigated, simuls exhibited the best performance for WPC formation. It was found that the tensile strength and Young's modulus of WPC increased about 1.6 and 1.5 times, respectively, as compared with the strength and modulus those of untreated wood.
Preferential adsorption of bovine fibrinogen dimer onto polymer microspheres having heterogeneous surfaces consisting of hydrophobic and hydrophilic parts
Authors: Okubo Masayoshi , Azuma Ichiro , Hattori Hideshi 
Published: April 2003

AbstractThe adsorption onto polymer microspheres of bovine fibrinogen (BFb) containing both dimeric and monomeric species was examined using various homopolymer, copolymer, and poly(2‐hydroxyethyl methacrylate)/polystyrene composite microspheres which were produced by the emulsifier‐free (seeded) emulsion polymerization technique. The preferential adsorption of the BFb dimer was clearly observed in an optimum region of the surface hydrophilicities of the polymer microspheres. The preferential adsorption of the BFb dimer onto the composite polymer microspheres having heterogeneous surfaces with both hydrophilic and hydrophobic parts was more remarkable than that onto the homopolymer and copolymer microspheres having homogeneous surfaces. The behavior is discussed in comparison with those for bovine serum albumin and human γ‐globulin.
Preparation of aminoalkyl celluloses and their adsorption and desorption of heavy metal ions
Authors: Nakamura Shigeo , Amano Masato , Saegusa Yasuo , Sato Toshihiko 
Published: April 2003

AbstractAminoalkyl celluloses (AmACs) were prepared from 6‐chlorodeoxycellulose and aliphatic diamines H2N(CH2)mNH2 (m = 2, 4, 6, 8). Their adsorption and desorption of divalent heavy metal ions such as Cu2+, Mn2+, Co2+, Ni2+ and their mixtures were also investigated in detail.Adsorption of metal ions on AmACs was remarkably affected by the pH of the solution, the metal ion and its initial concentration, and also the number of methylene units in the diamines. No adsorption of metal ions occurred on AmACs in strongly acidic solutions. However, metal ions were adsorbed rapidly on AmACs from weakly acidic solutions and the amount of adsorption increased with increasing pH. The effectiveness of AmACs as adsorbents decreased with increasing length of the methylene moiety, and AmACs from ethylenediamine (m = 2) was most effective. The adsorption of metal ions on AmACs was in the order Cu2+ > Ni2+ > Co2+ > Mn2+. Accordingly, their behavior followed the Irving‐Williams series and Cu2+ ions were preferentially adsorbed from solutions containing metal ion mixtures. The adsorbed ions were easily desorbed from the AmACs by stirring in 0.1 M HCl.
Ethylene–methacrylic acid copolymers as stress whitening suppressants in polypropylenes
Authors: Rengarajan R. , Kesavan S. K. , Fullerton K. L. , Lee S. 
Published: April 2003

AbstractImpact‐modified polypropylenes were prepared by incorporating copolymers of ethylenemethacrylic acid (E‐MAA) with different cations (zinc or sodium) and varying degrees of neutralization. These blends gave low stress whitening on impact. This phenomenon was due to the unique morphology of the blend. It was found that unneutralized acid copolymer and the zinc ionomer formed chainlike structures in the polypropylene matrix. These uniform chains crisscrossed the polypropylene matrix providing impact strength to the matrix. The matrix deformed on impact by the shear yielding mechanism, thus suppressing stress whitening. The impact modifier in the matrix did not form micro crazes in the matrix but formed several layers of crisscrossing chains. On the other hand, the sodium ionomer did not form chainlike structures. The impact modifier was dispersed evenly in the matrix. This type of morphology resulted in a higher degree of stress whitening. The failure on impact was due to crazing and not by shear yielding. This size of the impact modifier in the polypropylene matrix varied significantly depending on the melt processing equipment used. The dependence of polymer alloy mechanical properties on the composition has been studied to help in ionomer comparison.
Medical‐grade acrylic adhesives for skin contact
Authors: Kenney J. F. , Haddock T. H. , Sun R. L. , Parreira H. C. 
Published: April 2003

AbstractPressure‐sensitive acrylic adhesives for application to skin are made from 2‐ethylhexyl acrylate, isooctyl acrylate or n‐butyl acrylate copolymerized with polar functional monomers such as acrylic acid, methacrylic acid, vinyl acetate, methyl acrylate, N‐vinylcaprolactam, or hydroxyethyl methacrylate. Functional comonomers increase cohesive strength, provide surface polarity, and enhance wear performance. Tack, adhesion to skin, adhesive transfer to skin, and wear performance of the adhesive are governed by the molecular weight, glass transition temperature, and the viscoelastic behavior of the adhesive. Viscoelastic properties of the adhesive as measured by the Williams plasticity number (WPN), dynamic storage modulus (G′), dynamic loss modulus (G″), and tan δ are important polymer properties for good wear performance. Sweating skin, a moist environment, and physical activity are the most important factors influencing the failure of an adhesive tape during wear. A medicalgrade adhesive for application to human skin should be hypoallergenic. Medical‐grade adhesives are utilized in making surgical tapes for holding dressings in place, adhesive bandages, adhesive dressings to cover wounds, and surgical operating drapes.
Generation of porous polymer surfaces by solvent–nonsolvent treatment
Authors: Chen Jyh‐Herng , Ruckenstein Eli 
Published: April 2003

AbstractA method to generate a porous region near the surface of a polymer is suggested. In this method the region near the surface is swollen by immersing the polymer for a short time in a solvent. Subsequently, the polymer is introduced in a nonsolvent (for the polymer) that is, however, miscible with the solvent. The formation of the porous region is a result of (1) the swelling accompanied by the disentanglement of the surface molecular chains, and the dissolution of some of them during the immersion in the solvent, and (2) the rapid extraction of the solvent from the swollen region by the nonsolvent. The porous surface provides a matrix into which a second incompatible monomer can be polymerized so that the two otherwise incompatible polymers can adhere to one another.
Liquid crystalline phase‐formation behavior of cellulose cinnamate
Authors: Arai Kenichiro , Satoh Hidetoshi 
Published: April 2003

AbstractCellulose cinnamates with degrees of substitution (DS) of up to 2.3 were prepared by a reaction of cellulose with cinnamoyl chloride in pyridine. The cellulose cinnamate was found to form a cholesteric liquid crystalline phase at the concentrations higher than a critical concentration in some organic solvents. The critical concentration showed tendencies to be higher for the cellulose cinnamate with higher DS and with higher degree of polymerization (DP). Influences of formation of liquid crystalline phase and of irradiation with UV light on the physical strength of the cellulose cinnamate film were investigated and both were found to make the breaking strength and modulus of elastisity of the film higher.