bluuebunny/crossref_metadata_2025_split huggingface dataset:
Process‐resolved morphology of bismaleimide matrix composites
Authors: Viot Jean‐François , Seferis James C. 
Published: April 2003

AbstractA series of silicone‐modified bismaleimide resins have been examined as matrices for high performance continuous fiber‐reinforced composite materials. Detailed studies of the interrelation between processing, structure, and properties of both the neat resin and corresponding carbon‐fiber‐reinforced composite have identified that the silicone additive provides important morphological modification to the bismaleimide matrix for toughness improvements while, at the same time, retaining the elevated temperature performance. Micrographs of fracture surfaces of cured samples demonstrate remarkable similarities to fracture surfaces of rubber‐modified epoxy matrices. Specifically, a fracture surface covered with noncommunicating microcavities of 1.5 μm in diameter was observed. However, unlike rubber‐modified epoxies where the observed features are assumed to be created during fracture of the specimen, this study demonstrates that the microcavities are created during the cure process and, thus, exist in the bulk of the material before fracture. In simulated cures of the material either while obsered directly in a polarizing microscope or indirectly inside thermal analysis cells (DSC, TGA) and with examination of fractured surfaces of samples cured according to different temperature profiles, it is established that the silicone modifier, in conjunction with the processing conditions, is responsible for the morphological developments. Accordingly, a mechanism describing the observed morphology was proposed based on physical changes that the silicone additive experiences in relation to specific volatile products emitted during the cure process.
Effect of fillers on thermoplastic 1,2‐polybutadiene rubber: Mechanical and viscoelastic properties
Authors: Bhagawan S. S. , Tripathy D. K. , De S. K. 
Published: April 2003

AbstractThe effects of silica, carbon black, and china clay on the mechanical properties of 1,2‐polybutadiene have been investigated. They include stress–strain behavior, tensile strength, elongation, tear strength, tension set, impact strength, and hysteresis. The effect of silane coupling agent on these properties has also been studied. The stress–relaxation behavior of the filled and unfilled systems has also been compared. The rate of relaxation increases with temperature. The dynamic mechanical properties have been determined using a Rheovibron viscoelastometer at 35 Hz at different temperatures. The storage and loss moduli are enhanced by addition of fillers. Silane coupling agent increases storage modulus as well as tan δmax of the clay‐filled polymer. The suitability of Voigt and Reuss models in predicting the composite moduli is examined.
Pyrolysis‐evolved gas‐infrared spectroscopic characterization of poly(methyl methacrylate) copolymer glazing materials
Authors: Davidson R. G. 
Published: April 2003

AbstractThe linear temperature programmed pyrolysis of some commercial crosslinked poly(methyl methacrylate) copolymers has been examined by the technique of pyrolysis‐evolved gas‐infrared analysis. Methyl methacrylate monomer, methanol, and carbon dioxide were detected in the pyrolysis gases. The profiles of rate of evolution against temperature were used to identify the presence of occluded monomer and thermally unstable and groups such as unsaturation. The evolution profiles for methyl methacrylate and methanol were found to be characteristic for each type of crosslink. Evolution of methanol between 250°C and 300°C, and between 300°C and 350°C has been attributed to condensation reactions of carboxylic acid and primary amide groups, respectively, with adjacent ester groups. The evolution profiles were used to distinguish between samples from different manufacturers, and to identify material in aircraft canopies.
Cement mortar impregnated with poly(methyl methacrylate‐co‐styrene)
Authors: Bhattacharya Vijay K. , Maiti Mrinal M. , Maiti Sukumar 
Published: April 2003

AbstractPolymer‐impregnated mortars were prepared by copolymerization of a monomer mixture of methyl methacrylate and styrene in the ratios of 13:87 and 40:60 using Co‐60 gamma radiation. The copolymerization characteristics viz. the rate of polymerization, the extent of monomer loss, polymer loading, etc., were studied. The nature and molecular weight of the extractable polymer from the composite were determined. The flexural strength of the copolymer‐impregnated composites was found to be better than that of the composites impregnated with component homopolymers.
High performance size exclusion chromatography of starch with dimethyl sulfoxide as the mobile phase
Authors: Chuang Jau‐Yi , Sydor Robert J. 
Published: April 2003

AbstractTwo types of high performance size exclusion chromatographic (SEC) columns were tested for the characterization of starch samples: μ Bondagel and Aquapore. The mobile phase was dimethyl sulfoxide (DMSO) containing 0.03 M sodium nitrate maintained at 80°C. The results indicated that both μ Bondagel and Aquapore can be used to determine the relative molecular weight of starch. The exclusion limits for these columns exceed ten million. Preliminary results using μ Styragel are also reported. Examples of SEC analysis of starch, including starch with anionic groups, are given.
Phase behavior for blends of styrene containing triblock copolymers with poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Tucker P. S. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractThe extent to which the styrene end‐blocks of three commercially available triblock copolymers can mix with a particular poly(2,6‐dimethyl‐1,4‐phenylene oxide) (Mn = 22,600 and Mw = 34,000) or PPO has been examined by investigation of the glass transition behavior of the PPO and polystyrene (PS) portions of the blends using differential scanning calorimetry. Each block copolymer has a butadiene‐based mid‐block which was hydrogenated for two of these materials, but not the third. The three copolymers differ substantially in overall molecular weight and in molecula weight of the blocks. However, in analogy with the literature on blends of homopolymer polystyrene with styrene‐based block copolymers, the molecular weight of the PS block should be the principal factor affecting the phase behavior in the present blends. Mixtures of the PPO with the block copolymers having PS blocks with M = 14,500 (nonhydrogenated midblock) and with M = 29,000 (hydrogenated mid‐block) exhibited single composition‐dependent Tgs for the hard phase, indicating complete mixing of PS segments with the PPO, for all proportions. On the other hand, the block copolymer having a PS block with M = 7,500 and a hydrogenated mid‐block exhibited two separate hard phase Tgs corresponding to an essentially pure PPO phase and a PS‐rich phase. For blends of homopolymer PS with styrene‐based block copolymers, the similar two‐phase behavior of the glassy portion can be readily explained by entropic considerations. For the present case, the favorable enthalpic contribution for mixing PPO and PS is an additional factor which seems to influence the restrictions on molecular weight for complete mixing; however, additional work is needed to develop a more quantitative assessment of this new issue.
Preparation and surface activity of water‐soluble polyesters
Authors: Chen K. M. , Liu H. J. 
Published: April 2003

AbstractA novel series of water‐soluble polyester surfactants has been prepared by the polymerization of SIPM, PA, and PEG. The unique structural features of these surfactants have been confirmed by IR and NMR analyses. These water‐soluble polyester surfactants have been found to exhibit excellent surface active properties including surface tension, low‐foaming, solubilization, and dispersant properties for disperse dyes.
Permeation and separation of aqueous alcohol solutions through grafted poly(vinyl alcohol) latex membranes
Authors: Hsiue Ging‐Ho , Yang Yung‐Song , Kuo Jen‐Feng 
Published: April 2003

AbstractThe poly(vinyl alcohol)–acrylonitrile–2‐hydroxy ethyl methacrylate (PVA–AN–HEMA) grafted latex membrane was synthesized by grafting AN and HEMA mixture on PVA in aqueous solution. The ceric ammonium nitric in nitric acid was was used as a catalyst. This membrane has well‐balanced composition of hydrophilic and hydrophobic components and was proved by transition electron microscopy to process microstructure between continuous and disperse phases. The permeability of alcohol–water solution and separativity of phenol–water solution through this PVA–AN–HEMA membrane were studied. It was found that the permeation rate for aqueous solution as as alcohol–water was greater than that for pure water, and the separativity of phenol–water solution by pervaporation increased as the amount of PHEMA increased.
Characterization of solutions and aqueous dispersions of epoxy/amidoamine resins
Authors: Qaderi S. B. A. , Peck M. C. Paputa , Bauer D. R. 
Published: April 2003

AbstractMolecular weight advancement and epoxy conversion in epoxy‐amidoamine resins have been characterized in solutions and in aqueous dispersions using viscosity, light scattering, and near‐infrared spectroscopy. By measuring the intensity of the 4532 cm−1 band in the near infrared, it is possible to determine the concentration of epoxy groups in these resins at low levels in the presence of amine and acid groups as well as solvents and other species. The epoxy‐amine reaction in these resins is found to be second order with an activation energy of around 13 kcal/mole. The addition of one mole of carboxylic acid per mole of amine functionality was sufficient to quench the epoxy‐amine reaction. Preparation of aqueous dispersions suitable for electrocoat formulation required that the extent of epoxy reaction be within a given range. Although the addition of acid completely quenched the epoxy‐amine reaction, a slow side reaction was discovered which consumes epoxy groups and ultimately changes the physical properties of coatings made from these dispersions.
Chain extenders for polyesters. VI. Properties of the polyesters chain‐extended by 2,2′‐bis(4H‐3,1‐benzoxazin‐4‐one)
Authors: Inata Hiroo , Matsumura Shunichi 
Published: April 2003

AbstractSome properties of polymers derived by treating poly(ethylene terephthalate) (PET) with such hydroxyl‐addition‐type chain extenders as 2,2′‐bis(4H‐3,1‐benzoxazin‐4‐one) (BNZ) were investigated. Compared with ordinary PET, the chain‐extended PET has a slightly lower melting point and nearly equal molecular size distribution, which indicate that BNZ reacts to form linear chain‐extended polymers without branching. Oxalyl bis(anthranilate) unit copolymerized in the polyester chain showed little influence on thermal and hydrolytic stabilities. In addition, benzoxazinone groups remaining unreacted can act as a heat stabilizer to prevent the decrease in the molecular weight by the chain‐extending reaction in the solid phase. But they showed adverse effect on the hydrolytic stability by promoting hydrolysis of the polymer as much as the carboxyl groups.
The non‐Fickian diffusion of deterrents into a nitrocellulose‐based propellant
Authors: Winkler David A. , Starks Alan 
Published: April 2003

AbstractThe diffusion of solutions of ethyl centralite (EC), dibutylphthalate (DBP), and dinitrotoluene (DNT) into a nitrocellulose (NC) propellant is investigated. DBP and EC penetrate the propellant in a way consistent with Case II diffusion. The diffusion of DNT solutions is Fickian. The apparent activation energy for Case II diffusion is 62 kJ/mol for DBP and 66 kJ/mol for EC. Changes to coating solvent polarity have little effect on DNT and DBP penetration and merely alter the rate, not the mechanism, of EC diffusion into the propellant.
Grafting of poly(α‐chloroacrylonitrile) (α‐PCIAN) on carbon black and electrical properties of α‐PCIAN‐grafted carbon black compositions
Authors: Miyauchi Shin'Nosuke , Mino Nobuhiro , Balard Henri , Papirer Eugène , Donnet Jean Baptiste 
Published: April 2003

AbstractThe electrical properties of poly(α‐chloroacrylonitrile) (PCIAN) carbon black compositions were determined. These materials were prepared by polymerizing α‐chloroacrylonitrile in the presence of carbon black (GC resistors). Resistivities measurement of GC resistors shows a semiconductor‐like behavior. Moreover, the resistance change of GC resistors with electrical field strength is very large. It is concluded that the conduction of GC resistors is controlled by the thin polymer layer present at the surface of the carbon black particles. Heat degradation of such compositions was also investigated: A significant weight loss above 150°C is observed in all cases which can be attributed to thermal dehydrochlorination of PCIAN. After heat treatment at 300°C, during 1 h, the resistivities decrease of about 1 order of magnitude because of the formation of a semiconducting polyconjugated polymer by dehydrochlorination of PCIAN.
Micromechanisms of high‐energy peel failure in polyester–aluminum–polyester laminates
Authors: Brown D. J. , Lamb P. , Windle A. H. 
Published: April 2003

AbstractSymmetrical polyester‐aluminum‐polyester laminates are prepared using poly(ethylene terephthalate) film subjected to a glow discharge pretreatment. Extremely high peel energies (several hundred J m−2) are achieved, and the fracture path is principally cohesive: the laminate performance thus fully exploits the bulk mechanical properties of the PET. The peel surface exhibits extensive plasticity on a scale of tens of microns, with finer ductile tearing on a scale of order 1 μm. The mechanism of peel propagation and energy dissipation is discussed with regard to the optimisation of peel strength.
Van der Waals model for filled rubbers with modified interfacial contacts
Authors: Kilian H. G. , Schenk H. 
Published: April 2003

AbstractIt is shown how the global deformation mechanism in filler‐loaded vulcanizates were modified by additional filler‐to‐matrix bonds. A quantitative description is given in terms of an extended van der Waals treatment including the formulation of a reduced mechanical equation of state. An interpretation of the Mullins softening is presented.
A generalized criterion for rubber toughening: The critical matrix ligament thickness
Authors: Wu Souheng 
Published: April 2003

AbstractThe thickness of matrix ligament is shown to be the single parameter determining whether a polymer/rubber blend will be tough or brittle. The matrix ligament is defined as the region of the matrix between two neighboring rubber particles. Specifically, the ligament thickness is the surface‐to‐surface interparticle distance. When the average ligament thickness is smaller than a critical value, a blend will be tough; when greater, it will be brittle. In other words, a sharp brittle–tough transition occurs at the critical ligament thickness. This critical parameter is independent of rubber volume fraction and particle size, and is characteristic of the matrix for a given mode, temperature and rate of deformation. What is important is the matrix ligament, not rubber particles. The single matrix parameter explains the effects of phase morphology, rubber volume fraction, particle size, particle‐size polydispersity, and particle flocculation on toughness.
The mechanical properties of rubber‐modified vinyl esters
Authors: Liao Fu‐Hua , Chu Ning‐Jo , Tong Shen‐Nan 
Published: April 2003

Abstract“Vinyl esters” were prepared by reacting an epoxy resin (DGEBA) with acrylic and methacrylic acids, modified with Hycar VTBN, and cured at 90°C for 4 h with t‐butyl perbenzoate. The resultant materials showed a two‐phase structure in electron micrographs and dynamic mechanical spectra. The domain of the dispersed phase was estimated to be on the order of 10 nm in size. Infrared spectroscopy indicated extensive copolymerization of the internal double bonds or pendant vinyl groups in VTBN during the cure of the resin. The mechanical properties of the modified materials were measured, and the differences in mechanical behavior between the acrylic and methacrylic vinyl esters were discussed.
Die swell from capillary die and slit die: A theoretical study
Authors: Chiu Wen‐Yen , Shyu Goang‐Ding 
Published: April 2003

AbstractAssuming polymer fluids obey the CEF equation, equations concerning die swell from capillary die and slit die were derived. The die swell of polymer increased with increasing shear rate and recoverable shear. Our theoretical predictions conformed well with the experimental data of die swell for PP and PS.
The preparation and properties of zinc coordination complexes of poly(4‐vinylpyridine‐co‐n‐butyl methacrylate) copolymers
Authors: Jacovic Mihailo S. , Perovic Ivan , MacKnight William J. , Lenz Robert W. 
Published: April 2003

AbstractTwo poly(4‐vinylpyridine‐co‐n‐butyl methacrylate) copolymers containing 14.2 and 30.0 mol% of 4‐vinylpyridine residues were prepared by free radical copolymerization reactions. Insoluble complexes were obtained for each copolymer by reaction with zinc chloride. The coordination complexes obtained had a molar ratio of 4‐vinylpyridine residues to zinc atoms close to 2 in both cases. The rheological behavior of each of these complexes has been compared to that of the corresponding metal‐free copolymers, which were recovered by decomplexation. The metal complexed polymers exhibited much higher glass transition temperatures and much longer high temperature relaxation times than the corresponding uncomplexed copolymers.
Reactive extrusion of polypropylene II: Degradation kinetic modeling
Authors: Suwanda D. , Lew R. , Balke S. T. 
Published: April 2003

AbstractA kinetic model for the free‐radical‐initiated molecular weight degradation of polypropylene was further developed. The model has a single variable parameter, the initiator efficiency, f. Assumptions were detailed, new comparisons with experimental data presented, and model sensitivity to the value of f evaluated. The model was found to provide a good description of both molecular weight distribution and molecular weight average data from degradations carried out in a single‐screw extruder at 200 and 220°C. Data at 0.04 wt% initiator feed concentration were fit and the resulting f value used to predict results at 0.01 wt% and 0.02 wt%. In accordance with observation, the model predicted that temperature would have no effect on the molecular weight of the extrudate because the comparatively long (≥ 2.8 min) residence time in the extruder permitted degradation reactions to go to completion. The model predictions were found to depend upon the change in molecular weight distribution rather than the absolute value of the distribution data. Predictions were therefore unaffected by concentration correction in size exclusion chromatography interpretation. The model was determined to have a low sensitivity to the value of f. Hence, f was estimated to only ± 25% and it is anticipated that attempts to use the model for comparing different initiators would be limited by this characteristic. Also, because the minimum residence time in the extruder was 2.8 min, the model has yet to be tested against data at times less than this value.
Quantitative size exclusion chromatography of polypropylene II: Analysis systems
Authors: Lew R. , Cheung P. , Suwanda D. , Balke S. T. 
Published: April 2003

AbstractQuantitative size exclusion chromatography (SEC) was considered a system with the following components: sample preparation, fractionation, detection, calibration, and resolution correction. Four systems were evaluated: I was 3 columns with “conventional single detector interpretation”; II was 4 columns with concentration correction and detector assessment; III was concentration correction applied to the data of I; IV was two development “mixed bed” columns. Analysis of polystyrene standards included calculation of their molecular weight averages and use of the Glöckner “T” measure of resolution as well as “specific resolution index.” Systems I and III provided the best high molecular weight results. System IV allowed 12–20 min analysis times and provided a highly linear calibration curve with very good reproducibility; however, it showed significantly worse resolution at high molecular weights. Plots of molecular weight averages determined from SEC versus their known true values were particularly useful. Concentration correction using the Rudin model moved different concentration data toward a common universal calibration curve and generally lowered molecular weight averages. Narrow polystyrene standards required relatively high concentrations for precise molecular weight averages and therefore, their averages were not good indicators of the need for concentration correction. Analysis of polypropylene samples corroborated the lower high molecular weight resolution of System III. Concentration correction did significantly change the polypropylene molecular weight distribution but did not affect the result of the kinetic model fitting.
Thermal properties of liquid crystalline aromatic random copolyesters containing two different mesogenic modifications within a polymer backbone
Authors: Yoo Young Deuk , Kim Sung Chul 
Published: April 2003

AbstractTwo types of semiflexible mesogenic random copolyesters which contained both nematic and smectic type repeating units within the main chain were prepared and the thermal properties as well as the mesomorphic structures were characterized by differential scanning calorimetry and by polarizing microscope. The first type of copolymer (copolymer I) contained two repeating units which differed in the rigid mesogenic groups and the second (copolymer II) contained repeating units which differed in the length of flexible segment. Copolymerization disrupted the structural regularity of the crystal, lowered the crystal–mesophase transition temperature, and destabilized the molecular order of the smectic phase. These effects were more pronounced for copolymer II. However, the isotropization temperature was changed only slightly with the incorporation of the other mesogenic component. The crystal melting temperatures of both copolymers exhibited a eutectic behavior. A smectic to nematic transition, which was not observed for the homopolymers, occurred in the range of 0.4‐0.6 mole fractions of the smectic units for copolymer I and 0.5–0.85 for copolymer II. The molecular order of the nematic phase was slightly increased as the smectic units were incorporated, while those of the smectic phase became more disordered upon addition of the nematic units.
Chemically induced graft copolymerization of acrylic acid onto polyester fabrics. I. Kinetic investigation of grafting
Authors: Okoniewski M. , Sójka‐Ledakowicz J. , Ledakowicz S. 
Published: April 2003

AbstractThe kinetics of grafting of acrylic acid onto poly(ethylene terephthalate) fabrics initiated by benzoyl peroxide has been studied. Extent of grafting depended upon time, concentration of the initiator and the monomer, as well as the presence of the activator used. From the temperature dependence of the initial rate of grafting the overall activation energy for grafting was found to be 90 kJ/mol. The results of the monomer and temperature dependence found in this study are consistent with the rate expression derived from a normal kinetic scheme for grafting.
Liquid diffusion into epoxy resin composites
Authors: Aminabhavi Tejraj M. 
Published: April 2003

AbstractDynamic sorption behavior of four epoxy resin matrix composites derived from fly ash, jute, mica, or vermiculite was studied in water and salt solution at 24°, 35°, and 45°C. The mass of water uptake per mass of sample was determined as a function of time. Diffusion coefficients were higher for distilled water than those for salt solution. The diffusion parameters were computed from the Arrhenius plots and the results analyzed in terms of a Fickian model. The results as obtained from weight gain assays are consistent with the view that the activation energy of diffusion is associated with the energy required to produce a space of sufficient cross‐section for the diffusing molecule to pass.