bluuebunny/crossref_metadata_2025_split huggingface dataset:
Notch tip damage zone in biaxially oriented polypropylene at low temperature
Authors: Snyder J. , Hiltner A. , Baer E. 
Published: April 2003

AbstractIt is well established that biaxial orientation produces large improvements in the mechanical properties of polypropylene; this study further shows that the large improvements in mechanical behavior are magnified especially below the glass transition temperature. In this study, the irreversible deformation behavior of polypropylene during sharp single‐edge notch tension testing has been studied at two levels of biadial orientation at −40°C. Unoriented polypropylene formed a narrow wedge‐shaped damage zone that grows with increasing stress until catastrophic fracture occurs in a brittle manor. The damage zone consisted of many crazes that mainly grew perpendicular to the loading direction. The 50% oriented material initially developed a wedge‐shaped damage zone that grew wider as loading increased. This resulted in a drop of the length‐to‐width ratio at high sample extensions. The specimen fractured with stable crack growth in a ductile manner, showing a large resistance to crack growth. The 80% oriented material had a circular damage zone that consisted of many delamination crases. These crases grew by splitting the specimen in the thickness direction. Stable crack growth dominated the final failure process with the 80% oriented material showing nearly three times the toughness of the unoriented material. © 1994 John Wiley & Sons, Inc.
Mechanical properties of commingled plastic from recycled polyethylene and polystyrene
Authors: Li T. , Silverstein M. S. , Hiltner A. , Baer E. 
Published: April 2003

AbstractThe mechanical properties of commingled plastic in the form of thick beams prepared by the ET‐1 process have been examined in flexure and compression. The mechanical properties were evaluated in relationship to the hierarchical morphology described in a previous study. It was found that the flexural modulus was dominated by the properties of the skin and was satisfactorily modeled by approaches based on the observed micro‐morphology, such as the Nielsen and Davis models. It was not necessary to consider the skin–core macromorphology because the flexural modulus was dominated by the void‐free skin. The compressive modulus was lower than the flexural modulus and was strongly affected by the skin–core macro‐morphology. From the differences between the flexural and compressive moduli, it was determined that the core was essentially nonload‐bearing in compression. Flexural fracture initiated on the tension side of the beam and propagated rapidly through the thickness, whereas compressive failure occurred by longitudinal splitting of the skin. © 1994 John Wiley & Sons, Inc.
Crop resides as lon‐exchange materials. Treatment of soybean hull and sugar beet fiber (pulp) with epichlorohydrin to improve cation‐exchange capacity and physical stability
Authors: Laszlo Joseph A. , Dintzis Frederick R. 
Published: April 2003

AbstractIon exchange systems for the treatment of process water or wastewater may benefit by the use of inexpensive, disposable exchange materials before, or in place of, conventional regenerable exchange resins. Various agricultural by‐products have been proposed as suitable exchangers for this role, but they generally fail to have adequate capacity and physical stability for most applications. Two by‐products, soybean hull and sugar beet fiber, were found to have enhanced cation‐exchange capacity and stability upon treatment with epichlorophydrin and base. Exchange capacity was determined by measuring calcium binding. Physical stability was judged by three different aqueous extraction regimens. The most efficacious and economical reaction conditions found were: soybean hull and sugar beet fiber hydrated with water at a water‐to‐solids ratio of 6.4 : 1 and 8 : 1 (v/w), respectively, and epichlorohydrin applied at a 0.3 : 1 (v/w) ratio, for 6 h at room temperature. The resultant cross‐linked materials had cation‐exchange capacities of approximately 0.9 (soybean hull) and 1.3 (sugar beet fiber) meq/g dry weight. These epichlorohydrin‐treated agricultural by‐products may serve as cost‐effective, multivalent‐cation exchanges. © 1994 John Wiley & Sons, Inc.
Crystallinity in the polypropylene/cellulose system. II. Crystallization kinetics
Authors: Quillin Daniel T. , Yin Mengping , Koutsky James A. , Caulfield Daniel F. 
Published: April 2003

AbstractNonisothermal differential scanning calorimetry data for neat polypropylene and polypropylene with variously treated cellulose fillers has been used to solve for the Avrami exponent, n. Results show neat polypropylene to have an Avrami exponent value very close to the theoretically excepted value of 4.0. The addition of untreated cellulose fibers to polypropylene, which has been shown to produce a transcrystalline region, results in an exponent value of 2.7–2.9 for the initiation stage, followed by a value of 3.9 for the bulk stage. Treatment of the cellulose with alkyl ketene dimer, alkenyl succinic anhydride, or stearic acid results in intermediate exponent values from 2.7 to 3.9. These results verify the effectiveness of surface treatments in reducing the natural nucleating ability of cellulose. Sample mixing and filler content were also shown to play a role in the crystallization process. © 1994 John Wiley & Sons, Inc.
Morphology–property relationship in oriented PET films: Microstructural reorganization during heat treatment
Authors: Gohil Ramesh M. 
Published: April 2003

AbstractMorphology–property relationships for simultaneously biaxially stretched films and heatset with fixed dimensions in the temperature range of 100–240°C have been studied. The observed transition in various properties at 180°C can be explained on the basis of microstructural changes caused by competition among several processes, such as crystallization, solid‐state thickening, melting, and molecular relaxation as well as by melting and recrystallization. The resulting structures and, thereby, the properties are different in temperature Regime‐II (Tg to Tmax) and Regime‐III (Tmax to Tm). In Regime‐II, the high rate of crystallization compared to the rate of molecular relaxation develops a constrained amorphous phase, whereas the predominant melting and recrystallization process in Regime‐III generates the relaxed amorphous phase. The structural reorganization during heat treatment is almost the same for uniaxially oriented film, fibers, and biaxially oriented films prepared under similar processing conditions. © 1994 John Wiley & Sons, Inc.
Continuous carbonization of polyacrylonitrile‐based oxidized fibers: Aspects on mechanical properties and morphological structure
Authors: Liu J. , Wang P. H. , Li R. Y. 
Published: April 2003

AbstractBy following the progression of continuous carbonization (300–1250°C) of polyacrylonitrile (PAN)‐based oxidized fibers, variations in tensile mechanical properties and morphological structure are reported in detail along the carbonization line. The tensile strength and Young's modulus of the fibers generally increase throughout the carbonization stage. Meanwhile, the fiber diameter displays a significant decrease. The preferred orientation of carbon layer planes is observed to increase remarkably for temperatures over 400°C. In a similar manner, the stacking size increases significantly but reaches saturation around 600°C, a changing point corresponding to that observed for the variation of the Young's modulus. However, beyond about 1200°C, the stacking size again displays a marked increase. Results thus obtained are interpreted in relation to each other. Possible implications are also discussed. © 1994 John Wiley & Sons, Inc.
Thermal characteristics of silver powder‐filled polypropylene composites
Authors: Maiti S. N. , Ghosh K. 
Published: April 2003

AbstractThe thermal properties of silver powder‐filled polypropylene composites were studied as a function of filler concentration. Thermal conductivities of the composites increased with filler content. Comparison of the data with theoretical predictive models for two‐phase systems showed that the Nielson equation agreed reasonably well with the measured values. A TGA study showed that presence of silver powder increased the thermal stability of polypropylene through an increase in activation energy. The thermal expansion coefficient of the composites exhibited a decreased in the presence of Ag powder. Surface treatment of Ag powder with a titanate coupling agent marginally increased thermal conductivity and decreased thermal expansion coefficient values, implying a degree of enhance adhesion of the filler with the polymer. © 1994 John Wiley & Sons, Inc.
Mechanical property and fracture morphology of fiber‐reinforced polysulfone plasticized with acetylene‐terminated sulfone
Authors: Mai Kancheng , Li Jiaju , Zeng Hanmin 
Published: April 2003

AbstractThe mechanical property and fracture morphology of glass fiber‐ (GF) and carbon fiber‐ (CF) reinforced polysulfone (PSF) blends with bis (4‐(4‐ethynyl phenoxy) phenyl) sulfone (ATS‐C) have been investigated. Experimental results show that the tensile and flexural properties and impact strength of GF‐reinforced ATS‐C/PSF composites decrease as the processing temperature or/and the processing time increase, but CF‐reinforced ATS‐C/PSF composites exhibit better mechanical properties. Although interlaminar shear strenght (ILSS) for fiber‐reinforced ATS‐C/PSF composites decreases, scanning electron microscopy (SEM) observation of fracture surface indicates that the fractural model of fiber‐reinforced PSF composites changes from the interfacial debonding fracture to the matrix fracture at the interfacial region with addition of ATS‐C and the increase of the processing temperature. The end‐use temperature of polysulfone can be retained and solvent resistance of polysulfone can be improved due to the formation of a semi‐interpenetrating polymer network. © 1994 John Wiley & Sons, Inc.
Copolymers of 1,5‐dioxepan‐2‐one and L‐ or D,L‐dilactide: Hydrolytic degradation behavior
Authors: Löfgren A. , Albertsson A.‐C. 
Published: April 2003

AbstractThe degradation of two series of copolymers made of 1,5‐dioxepan‐2‐one (DXO) and L‐or D,L‐dilactide has been investigated. In vitro degradation of the six copolymers with different ratios of the ingoing components was followed using size exlusion chromatography (SEC), nuclear magnetic resonance (NMR) spectrometry, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The copolymers with a high content of lactic acid units showed a higher rate of hydrolysis than the DXO‐rich copolymers. The copolymer morphology also affects the rate of degradation as seen in the differences between amorphous and semicrystalline samples. The effect of electron beam sterilization was studied as well as the degradation products formed using the gas chromatography‐mass spectrometry (GC–MS) technique. The major degradation products resulted from ester bond cleavage. Kinetics of the in vitro degradation indicate a complex hydrolysis, probably a mixture of an uncatalyzed and catalyzed mechanism. © 1994 John Wiley & Sons, Inc.
Structure and properties of maleated high‐density polyethylene
Authors: Wang Yilong , Ji Deqiang , Yang Changlai , Zhang Hongjin , Qin Chuan , Huang Baotong 
Published: April 2003

AbstractPossible changes in the structure and properties of maleated polyethylene (HDPE–MA) at different degrees of grafting (D.G.) were examined. At the level of 1.6 maleic anhydride (MA)/100 ethylene units E, 70–80% of crystallinity of the parent PE was retained (DSC and WAXD). Both melting temperature and crystallization temperature decreased only slightly with increase in D. G. The lattice constantsaandbof the orthorhombic PE crystallites remained constant, althoughcwas constantly at a larger value. The presence of MA groups hampered the packing of PE chains, leading to an increase in PE crystallite sizes ofL̄110andL̄200with maleation. Of the viscoelastic relaxations, dynamic mechanical analysis showed easier segmental motions and thus lowering in γ‐, α‐ and β‐relaxation temperatures with maleation. The breaking strength (σb) increased slightly with maleation, whereas the elongation at break (εb) lowered due to interaction between the MA groups. In all, in HDPE‐MA up to a D. G. of 1.6 MA/100 E, PE properties were maintained to be used per se or as a compatibilizer for blends involving PE or in any other usage where retention of PE properties is desired. © 1994 John Wiley & Sons, Inc.
Characterization of flexible slabstock foams containing lithium chloride
Authors: Moreland J. C. , Wilkes G. L. , Turner R. B. , Rightor E. G. 
Published: April 2003

AbstractCharacterization of a series of flexible polyurethane foams that contain LiCl in their formulation is discussed. These foams were developed in order to provide an alternative method to produce foams without physical blowing agents and still attempt to maintain specific important physical properties. Three high water content foams of varying LiCl content have been characterized by utilizing several morphological techniques as well as by their viscoelastic behavior. From a morphological standpoint, it appears that by adding LiCl to the formulation, there is less formation of urea‐rich aggregates that occur when LiCl is absent. Also, the hard segments are more dispersed as single units within the network. The cellular texture of the LiCl‐containing foams also shows a greater amount of cellular window material than the same foam without LiCl. Both of these changes due to LiCl addition are believed to bring about a significant increase in the amount of viscoelastic decay. This decay has been observed in tensile stress relaxation, compression load relaxation, and compressive creep studies. Temperature also has a more significant effect on the compression load relaxation behavior of foams with LiCl in their formulation than when absent. These differences in viscoelastic behavior between foams with and without LiCl in their formulation are attributed to the greater mobility of the hard segments in the presence of the LiCl additive serving as a localized “hard segment” plasticizer that also promotes more phase mixing in the foams. © 1994 John Wiley & Sons, Inc.
Polyacrylonitrile ultrafiltration membranes containing negatively charged groups for permeation and separation of dextran and dextransulfate
Authors: Kobayashi Takaomi , Miyamoto Takuro , Nagai Toshihiko , Fujii Nobuyuki 
Published: April 2003

AbstractUltrafiltration membranes of poly(acrylonitrile‐co‐sodium styrenesulfonate) [P(AN‐co‐SSS)] were prepared by casting the copolymer solution into water. The ultrafiltration rate of P(AN‐co‐SSS) membranes was controlled by adding poly(ethylene glycol) (PEG) of various molecular weights to the casting solution. The effect of the PEG addition on the membrane properties was examined. By using the P(AN‐co‐SSS) membranes, which possess various molecular weight cutoff (MWCO) properties, the permeation behaviors of dextran (D) and dextransulfate (DS) were compared. The P(AN‐co‐SSS) membranes markedly restricted the permeation of DS, owing to electrostatic barrier of the negatively charged groups in the membrane. The electrostatic sieve separation of DS and D, each having similar molecular size, with the membranes was also investigated. The membrane having negatively charged groups effectively rejected to DS with a high permselectivity. © 1994 John Wiley & Sons, Inc.
The deformation behavior of poly(dimethyl siloxane) networks. II. Equilibrium swelling
Authors: Venkatraman S. , Nixon A. , Highe A. 
Published: April 2003

AbstractThe equilibrium swelling behavior of end‐linked silicone networks has been studied, using low molecular weight silicone oils as diluents. Using the phantom and affine versions of the Flory–Rehner elasticity theory, the predictability of the equilibrium swelling has been examined. It was found that a modified version of the Flory–Rehner equation can be used to predict the equilibrium swelling behavior, provided the interaction parameter is known or measured. The modification is the use of the measured elastic shear modulus of the network prior to swelling, to calculate the density of network chains needed in the equation for swelling. This implies that both entangled and chemically linked chains contribute to the swelling behavior, since the modulus itself is predicted by the use of an equation that incorporates the contribution of entanglements. © 1994 John Wiley & Sons, Inc.
Liquefaction of wood in the presence of phenol using phosphoric acid as a catalyst and the flow properties of the liquefied wood
Authors: Lin Lianzhen , Yoshioka Mariko , Yao Yaoguang , Shiraishi Nobuo 
Published: April 2003

AbstractThe liquefaction of wood in the presence of phenol using phosphoric acid as a catalyst and the flow properties of the obtained liquefied wood were investigated. It was found that phosphoric acid is a satisfactory catalyst for liquefying wood. The amount of phenol that reacts with the liquefied wood components (i.e., combined phenol) increases with an increase in liquefaction temperature, liquefaction time, catalyst content, or liquid ratio. By removing the free phenol, the resulting liquefied woods become novolaclike resins. The measurements of the flow properties of these liquefied woods reveal that the melts of liquefied woods behave as pseudoplastics and their flows obey the Ostwald de Waele power law equation. The amount of combined phenol within the liquefied wood and the presence of filler in the liquefied wood have great influence on their flow properties. The flowing temperature, activation energy, and zero shear viscosity of the liquefied woods show tendencies to increase with an increase in combined phenol. © 1994 John Wiley & Sons, Inc.
X‐ray study of crystallinity and disorder in ramie fiber
Authors: Sao K. P. , Samantaray B. K. , Bhattacherjee S. 
Published: April 2003

AbstractThe degree of crystallinity and the disorder parameter in ramie fibers treated with various concentrations of aqueous NaOH solutions at room temperature (∼ 30°C) and at 0°C, respectively, have been analyzed by the wide‐angle x‐ray diffraction method of Ruland and Vonk.9–11 The results appear to suggest the presence of highly distorted crystalline regions that are first affected by lower concentrations of alkali. At higher concentrations of mercerizing strength it is observed that the lattice conversion to cellulose II is accompanied by a decrease in the degree of crystallinity and an increase in the disorder parameter values. The tensile properties of the fibers corroborate the results. © 1994 John Wiley & Sons, Inc.
Synthesis of nonionic and anionic hydrogels bearing a monosaccharide residue and their properties
Authors: Fukudome Norihiro , Suzuki Kazuya , Yashima Eiji , Akashi Mitsuru 
Published: April 2003

AbstractNonionic hydrogels bearing glucoside residues were synthesized by free‐radical copolymerization of glucosylethyl methacrylate (GEMA) and N,N′‐methylenebisacrylamide (BisA) at 0°C for 2 h using ammonium peroxodisulfate and N,N,N′,N′‐tetramethylethylenediamine as the initiator. The cross‐linked polymer gel was obtained quantitatively. The nonionic gels absorbed 30 times as much water as their own weight. Copolymerization of GEMA, sodium acrylate, and BisA gave anionic hydrogels, which absorbed ca. 100 times as much water as their own weight at pH 6.5. The swelling behavior of the nonionic and the anionic hydrogels bearing glucose residues was studied in detail. © 1994 John Wiley & Sons, Inc.
Rubber‐ and thermoplastic‐toughened epoxy adhesive films
Authors: Romano A. M. , Garbassi F. , Braglia R. 
Published: April 2003

AbstractEpoxy resins have been toughened using together two components: a liquid rubber (Hycar CTBN 1300 × 13) and a thermoplastic polymer (Phenoxy PKHH). Unsupported adhesive films have been obtained from blends. The effect of different curing cycles on morphology, fracture behavior, and adhesive strength has been studied, monitoring phase separation by dynamic mechanical analysis. The combination of the two moieties was found the most efficient toughening agent when a slow curing cycle was adopted. © 1994 John Wiley & Sons, Inc.
Controlled release of proteins from poly(L‐lactic acid) coated polyisobutylcyanoacrylate microcapsules
Authors: Park Tae Gwan , Alonso Maria J. , Langer Robert 
Published: April 2003

AbstractPoly(L‐lactic acid)‐coated polyisobutylcyanoacrylate microcapsules containing protein molecules were prepared by a single‐step procedure based on either a double‐emulsion‐solvent evaporation method or a spray‐drying method. First, an aqueous protein solution was emulsified in an organic phase of methylene chloride containing a wall‐forming monomer (isobutylcyanoacrylate), various kinds of poly(L‐lactic acid), and a surfactant. An immediate polymerization process of isobutylcyanoacrylate takes place at the W/O interface upon contact with hydroxide ion in the aqueous phase, leading to the formation of a polyisobutylcyanoacrylate wall around the aqueous droplets. This W/O emulsion was reemulsified in an aqueous solution to promote the solvent removal and, consequently, the precipitation of poly(L‐lactic acid) onto polyisobutylcyanoacrylate microcapsules or was spraydried to directly deposit the poly(L‐lactic acid) on the wall. Three proteins, bovine serum albumin, horseradish peroxidase, and tetanus toxoid, were encapsulated in these poly(L‐lactic acid)‐coated polyisobutylcyanoacrylate microcapsules, and then their release profiles were examinedin vitroas a function of molecular weight of poly(L‐lactic acid) and its copolymers with glycolic acid. These formulations exhibited a low “burst” effect at initial incubation stages and released the proteins for extended periods of time. Subcutaneous injections of the tetanus toxoid‐loaded microparticles into rats showed that the time course of immunization (antibody titer) can be controlled by the type of polymer matrices used. © 1994 John Wiley & Sons, Inc.
Physical, thermomechanical, and rheological properties of bisphenol A–tetrabromobisphenol a copolycarbonates
Authors: Marks M. J. , Brewster S. L. , Sekinger J. K. 
Published: April 2003

AbstractThe physical, thermomechanical, and rheological properties of bisphenol A–tetrabromobisphenol A copolycarbonates (BA–TBBA coPCs) were studied as a function of copolymer composition. TBBA carbonate segments in the copolymer induce proportionally increased glass transition temperatures, heat distortion temperatures, ignition resistance, tensile and flexural moduli, and density. Properties that do not change proportionately with copolymer composition are coefficient of linear thermal expansion, ambient notched Izod and dart puncture impact strengths, and refractive index. Many properties of BA‐TBBA coPCs, including glass transition temperature, heat distortion temperature under load, and modulus, approach those of amorphous high‐performance thermoplastics such as polyetherimide and polyethersulfone. However, these copolymers have the possible advantage of melt blending with bisphenol A polycarbonate to form homogeneous alloys with variable and controllable properties. © 1994 John Wiley & Sons, Inc.