bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tensile retraction measurements. IV. Determination of loose end pullout in gum vulcanizates
Authors: Hergenrother William L. , Doshak John M. 
Published: April 2003

AbstractTensile retraction measurements have been made on unfilled rubbers cured with either sulfur or dicumyl peroxide to different levels of crosslink density. The rubbers chosen were emulsion and solution polymerized anionic SBRs, cis‐polybutadiene, natural rubber, and anionic 1,4‐polybutadienes of different molecular weight. The measured molecular weight between crosslinks (Mc) at each extension gave a smooth curve when plotted against the maximum extension (Λmax) used for the measurement. This curve was separated into three linear regions that characterize the cured rubber. The first region, above about 30% elongation, gave a Λmax = 1 intercept that decreased with either increased polymer Mn or increased level of curatives. Subtracting this calculated crosslink density from the measured crosslink density below about 30% elongation gave another smooth curve when plotted against Λmax. A second linear relationship was described in the general range of 5‐30% elongation. Below about 5% elongation, a third linear relationship was found. This line was determined from the differences between the calculated and the observed crosslink densities in the lowest strain region of the intermediate strain plot. Possible explanations of these three linear regions have been made. Supporting evidence was gained from temperature‐dependent experiments as well as from correlation of experimental results with polymers of different values of Tg.
Internal stress, lattice deformation, and modulus of polymers
Authors: Zhang Anqiu , Jiang Hao , Wu Zongquan , Wu Chenxun , Qian Baojun 
Published: April 2003

AbstractThe relationships among internal stress, lattice deformation, and the moduli of polymers, such as poly(ethylene terephthalate) (PET), polypropylene (PP), polyethylene (PE), polyacryonitrile (PAN), and poly(p‐phenylene terephthalamide) (PPTA), have been studied systematically. Compared to small molecule crystals, polymer crystals have many more defects and their parameters of the crystal unit cells and the density of the crystalline region are easy to vary to a certain extent. During the processing, external stresses were put on the polymer fibers and polymer molecules were drastically deformed, which induced polymer crystallization and preferred orientation. After processing, there are many macromolecules frozen in the nonequilibrium status, which is the cause of internal stress. Heat treatment could give energy to the macromolecules to release the internal stress and to approach thermodynamic equilibrium. For polymer crystals, the higher the annealing temperature, the shorter the lengths of the unit cell axes, the more integral and regular the crystal lattice, and the smaller the unit cell volume. Crystalline modulus changes not only with different kinds of polymer materials, but also with measurement temperature and processing history. Polymer processing, mainly drawing, causes orientation and internal stress which causes lattice deformation and raises tensile modulus of polymer materials.
Synthesis and thermal stability, dielectric and conductivity characteristics of some aromatic anhydride‐modified carbazole polymers
Authors: Biswas Mukul , Mitra Pradyot 
Published: April 2003

AbstractCopolycondensates have been prepared from carbazole, poly(N‐vinylcarbazole) and various aromatic anhydrides, e.g., phthalic anhydride, trimellitic acid anhydride, pyromellitic dianhydride, naphthalene tetracarboxylic dianhydride, and benzophenone tetracarboxylic dianhydride in presence of the Friedel–Crafts catalyst anhydrous zinc chloride at high temperature. The polymers have been characterized by elemental analyses and IR spectroscopy. Thermal stabilities, dielectric, and conductivity behaviors of these polymers have also been evaluated and it has been observed that these properties show interesting differences depending upon the nature of the anhydride.
Seeded emulsion polymerization of n‐butyl acrylate utilizing miniemulsions
Authors: Tang P. L. , Sudol E. D. , Adams M. , El‐Aasser M. S. , Asua J. M. 
Published: April 2003

AbstractNucleation of polymer particles in the seeded emulsion polymerization of n‐butyl acrylate (BuA) was studied through experiments designed to control the amount of new particles formed. The results show that for the batch and semicontinuous seeded polymerization of BuA, a small amount of new particles was formed in the system in which the monomer was added neat, whereas a singificant amount of new particles was formed when the monomer was added as a miniemulsion. This suggests that new particles formed in the miniemulsion process were from nucleation of the monomer droplets. These experiments also showed that monomer‐droplet nucleation decreased with increasing seed concentration in the reactor. For the seeded semicontinuous polymerizations, monomer‐droplet nucleation decreases with decreasing BuA miniemulsion feed rate. The results also show that monomerdroplet nucleation takes place whenever miniemulsion droplets exist in the reactor. This study suggests that miniemulsions can be used to control the particle size distribution of a polymer latex system.
Quinone amine polymers. IX. Attempts to synthesize polyamine–benzoquinone polymers using air and oxygen as oxidizing agents
Authors: Nithianandam V. S. , Erhan S. 
Published: April 2003

AbstractAttempts to synthesize Jeffamine D‐400 : p‐benzoquinone = 1 : 1 and later Jeffamine D‐400 : hydroquinone = 1 : 1 oligomers, using air or oxygen as the oxidizing agent, have been only partially successful. Although oligomers that yield nontacky coatings are completely precipitable in water, only about 25% of these products are precipitable in water while 75% remains in suspension. These polymers yield tacky coatings, which suggests that neither air nor oxygen is capable of oxidizing hydroquinone to benzoquinone, which is necessary for the formation of the polymer. Hence, most of the oligomer chains are too short to precipitate in water.
Studies on renewable polyphenol‐based cation exchange resins of moderately high capacity
Authors: Mitra N. C. , Banerjee R. S. , Sarkar A. 
Published: April 2003

AbstractMost of the commercially available ion exchange resins at present are either styrene–DVB‐based or phenol‐based and these are dependent on petroleum products. In view of the ever increasing demand for ion exchange resins and the petroleum crisis, the cost of these resins is going up in leaps and bounds. Although work on ion exchange resins based on naturally occurring tannins and similar materials have been reported in the literature, their low stability, insufficiently low exchange capacity, and similar other disadvantages come in the way of commercial exploitation of these products. In the present communication, studies on preparation and properties, viz., exchange capacity, hydration, swelling, stability, etc. of some effective cation exchange resins which have been obtained from a renewable natural resource of polyphenolic nature and some small proportion of phenol have been reported. The resins studied are stable and of moderately high exchange capacity (2–3 meq/g). Substituting phenol with low‐priced renewable polyphenolic material, the resultant copolymer matrix after sulfonation gives ion exchange resins which are quite economic. Their properties are comparable with the commercial resins available in the market.
Photoinitiated crosslinking of hydroxypropyl cellulose in the isotropic and liquid crystal states
Authors: Song Cheng Qian , Litt Morton H. , Manas‐Zloczower Ica 
Published: April 2003

AbstractThe influence of temperature, concentration, and shear rate on the formation of liquid crystal solutions of hydroxypropyl cellulose (HPC) in DMAc and the preservation of the structure by photoinitiated crosslinking were investigated. The rate of changes in the relaxation pattern for the characteristic band texture of HPC liquid crystals after cessation of shear is inversely proportional to the extent of the crosslinking. This shows that the liquid crystalline structure is preserved upon crosslinking. The molecular orientation of the crosslinked films as a function of mesophase organization and concentration during crosslinking was studied.
Interfacial polyfunctional condensation: Curing reaction
Authors: Chern Yaw‐Terng , Chen Leo‐Wang 
Published: April 2003

AbstractHeat treatment of films obtained by interfacial condensation of 4,4′‐methylene dianiline (MDA) or ethylene diamine (EDA) in water and 1,2,4,5‐benzenetetra acyl chloride (BTAC) in dichloromethane were studied by Fourier transform infrared spectroscopy (FTIR), 1H‐and 13C‐nuclear magnetic resonance (NMR), fast atom bombardment mass spectrometry (FABMS), an elemental analyzer, and differential scanning calorimetry (DSC). The reaction scheme for forming the polyimide is presented. Films were synthesized from the aromatic diamine and from the aliphatic diamine system. Both must go through two‐stage thermal treatment to form the structure of the imide. The first stage of this reaction is the imidization of the polyamic acid, and the second is the reaction to imidization of the functional amide group linked to the neighboring carbon on the benzene ring. After thermal treatment, the films will maintain good heat resistance. The difference between the mentioned interfacial synthetic polyimide and the conventional synthetic polyimide is that no isoimide and anhydride groups are found in the former. But the thickness of the film is limited by the nature of interfacial polymerization. In our reaction system, the maximum thickness of the film did not exceed 20 μm.
A new model for the shear viscosity of carbon black–polybutadiene, styrene suspensions
Authors: Chen Chao‐Cheng , Chiu Wen‐Yen 
Published: April 2003

AbstractThe shear viscosity of carbon black–polybutadiene, styrene suspensions is studied. The suspensions show strong shear thinning behavior. At very low shear rate, an extrapolated constant shear stress that is designated as the apparent yield stress can be obtained. A model is developed based on the kinetics and energy dissipation of the flocculation process in suspensions of Newtonian liquid. With a mixing rule, the model can also predict the viscosity of suspensions with particle‐size distribution. The applicability of the model can be extended to suspensions of non‐Newtonian liquid if the parameters in the model are regarded as functions of the viscosity of suspending liquid.
Atomic oxygen effects on the prefailure damage processes in highly filled glass/mica/epoxy composites
Authors: Regola M. , Baer E. , Hiltner A. 
Published: April 2003

AbstractIn the present study, the effect of atomic oxygen (AO) exposure, as a simulation of low earth orbit, on the flexural properties and prefailure damage mechanisms of a series of short glass fiber/mica/epoxy composites under three‐point bending were elucidated using acoustic emission (AE) techniques. The incorporation of mica in the composites was shown to increase the resistance to AO as measured by the weight loss, ashing rate, and reaction efficiency. Furthermore, as the mica content increased, the resistance increased such that the all‐mica composite had over one order of magnitude lower ashing rate and reaction efficiency than did the all‐glass‐fiber composite. This increased resistance was caused by the mica particles preferentially orienting parallel to the surface of the composites, creating an inorganic barrier to attack. The AO‐induced erosion was found to have an insignificant effect on both the flexural properties and prefailure damage mechanisms because the erosion was confined to the epoxy surface only and did not affect the bulk.
A DSC study of curative interactions. II. The interaction of 2,2′‐dibenzothiazole with ZnO, sulfur, and stearic acid
Authors: Kruger F. W. H. , McGill W. J. 
Published: April 2003

AbstractThe interaction of combinations of sulfur, 2,2′‐dibenzothiazole (MBTS), ZnO, and stearic acid were studied by differential scanning calorimetry. A MBTS/stearic acid interaction was indicated as evidenced by the effect the MBTS/stearic acid combination had on the melting of sulfur, the Sα → Sβ transition being suppressed in favor of a Sα → Sγ transition. The dissolution/interaction of MBTS in molten sulfur was also delayed by the MBTS/stearic acid interaction, which, it is proposed, involved protonation of the N atom in MBTS by stearic acid. MBTS did not affect the formation of zinc stearate from ZnO and stearic acid, but when sulfure was added to the mixture, the ZnO/stearic acid reaction did not go to completion. No direct evidence for the formation of 2,2′‐dibenzothiazole polysulphides was found, but the absence of the Sγ → Sμ transition in sulfur/MBTS mixes was interpreted as indirect evidence of a reaction between these curatives. There was no evidence for the formation of a sulfur/MBTS/ZnO compound of the type generally attributed the role of an active sulfurating agent in accelerated sulfur vulcanization.
Effect of chemical structure of allyl ethers on polymerization and properties of multifunctional acrylate systems
Authors: Jensen Eirik S. , Gatenholm Paul , Nanguneri Srikanth R. , Mathias Lon J. 
Published: April 2003

AbstractAllyl ether resins with various chemical structures and degrees of functionality were used as promoters and cross‐linkers for polymerization of acrylic oligomers at room temperature in air. Thin films were prepared to allow monitoring of polymerization via disappearance of acrylate and allylic unsaturation by FTIR. The effect of air upon curing of films was investigated; excluding air from the surface of the film had a much greater effect than did addition of allyl ether. In air, the curing rate and extent of cure were found to be dependent upon molecular weight Mn and degree of functionality of the allyl compounds. At high allyl monomer concentrations, homopolymerization of the allyl groups occurred. The mechanical properties (tensile strength, Young's modulus, and elongation at break) of films were evaluated on an Instron, whereas viscoelastic properties, transition temperatures, and cross‐link densities of polymer bars were studied by dynamic mechanical analysis and relaxation measurements. The study showed that addition of highly functional allyl ethers combines the advantages of an air‐curable system with those of highly cross‐linked materials, allowing ultimate properties to be tailored.
Polycyclic aromatic hydrocarbons (PAHs) in soot produced by combustion of polystyrene, polypropylene, and wood
Authors: Elomaa Matti , Saharinen Erkki 
Published: April 2003

AbstractThe smoke and soot produced by the combustion of plastics or wood in a domestic stove or fireplace contain many poisonous compounds, including the polycyclic aromatic hydrocarbons (PAHs), many of which are carcinogenic. PAHs were selected as the subject of our study to gain a better sense of the hazards of burning plastics. Small samples of polystyrene, polypropylene, and wood underwent combustion in a tubular oven at 700°C; in addition, polystyrene and wood were combusted at room temperature. After their extraction and purification, the PAHs were analyzed by gas chromatography and mass spectrometry. Conditions in the hot oven promoted soot production, whereas combustion at room temperature led to somewhat more complete combustion. The PAH profiles of the examined materials resembled each other to some extent, though the original chemical structure of the polymeric materials varied a great deal. However, clear differences between the materials could be detected from the soot extracts, the soot of polystyrene being especially rich in compounds containing remnants of the polymer structure. Carcinogenic activity caused by the PAHs can be assumed to be of the same order of magnitude as soot from the combustion of wood.
Acid–base surface properties of modified poly(ethylene terephthalate) films and gelatin: Relationship to adhesion
Authors: Lavielle L. , Schultz J. , Nakajima K. 
Published: April 2003

AbstractCharacterization of poly(ethylene terephthalate) (PET) films surfaces through wettability measurements and inverse gas chromatography techniques leads to a better knowledge of the potential interactions with a coating. An important case is the one relative to gelatin coatings for photographic films. In order to favor adhesion on PET, it is of interest to examine the problem in terms of acid–base interactions. PET is found amphoteric and gelatin rather basic. Several surface treatments on PET like orientation on water and flame or plasma treatment in air lead to an increase in surface acidity. Adhesion with gelatin as determined by the peel test is increased through a flame treatment, because of the higher acidity of PET and subsequent chemical bonding at the interface. Determination of acid‐base surface properties of PET and gelatin appears to be an excellent tool for adhesion prediction.
Quinone–amine polymers. VI. Syntheses and solubilities of several cooligomers (paqs) produced by reacting two diamines with p‐benzoquinone
Authors: Nithianandam V. S. , Chertok F. , Erhan S. 
Published: April 2003

AbstractThe solubilities of some polyamine–;quinone oligomers (PAQs) derived from various diamines were found to be incredibly low. Ethylene‐diamine–p‐benzoquinone products were insoluble in all 34 solvents used in assessing solubilities of polymers. Syntheses of copolymers/cooligomers of an amine yielding insoluble product with another that produces highly soluble amine were attempted. The increase in the solubilities of these copolymers/cooligomers as well as their appearances suggest that it is possible to produce PAQs from two different diamines.
Dynamic mechanical properties of quinazolone–imide block copolymer
Authors: Fukami Akira , Iisaka Katsuyoshi , Kubota Shigeru , Etoh Shouhei 
Published: April 2003

AbstractDynamic mechanical properties have been investigated over the temperature range of−150–360°C for the quinazolone–imide copolymers, prepared by condensation of the amine‐terminated quinazolone prepolymer with a stoichiometric quantity of pyromellitic dianhydride or 3,3′,4,4′‐benzophenone‐tetracarboxilic dianhydride. Both copolymers have, respectively, the low‐temperature β‐relaxation and the β*‐relaxation, as well as the case of poly(4,4′‐oxydiphenylene–pyromellite‐imide) (Kapton) examined for comparison. These relaxations seem to contribute to toughness of the copolymers. The α‐relaxations for both copolymers occurred at much the same temperature of 320°C, which can be assigned to a large scale segmental motion of the quinazolone chain sequence. The α‐peak temperatures shifted into higher temperatures by heat aging. This can be explained in terms of crosslinking in the copolymers, supported by swelling test in hot m‐cresol and IR spectroscopy.
Phase separation in carboxylated polysulfone/solvent/water systems
Authors: Lau Wayne W. Y. , Guiver Michael D. , Matsuura T. 
Published: April 2003

AbstractThe cloud point curves for the ternary systems carboxylated polysulfones/solvent/water were determined by a titration method. Membrane‐forming solvents used were NMP, DMAc, DMF, DMSO, TMU, and DMPU. Four modified polysulfones containing 0.43, 0.93, 1.38, and 1.93 carboxyl groups per repeat unit were synthesized for this study. Water/solvent theta‐compositions and solubility parameters for these polymers were also estimated.
Plasma graft polymerization of N,N‐dimethylaminoethyl methacrylate and water–ethanol separation by pervaporation through the grafted membranes
Authors: Hirotsu Toshihiro , Arita Akito 
Published: April 2003

AbstractN,N‐dimethylaminoethyl methacrylate was graft‐polymerized onto the porous polypropylene films of Celgard 2400 and 2500 which have been previously surface‐activated by glow discharge plasmas. The grafting was dependent on various factors both in the plasma pretreatment and the post‐polymerization with the monomer. The reaction was discussed from the aspects of the dependences of graft polymerization on discharge power, plasma pretreatment period, etc. When the grafting exceeded a critical amount depending on the size of pores on the substrate film, pervaporation of water‐ethanol separation functioned through these grafted membranes. The water permselectivity was improved by the ammonium ionization of the pendant N,N‐dimethylamino group using dimethyl sulfate or chloroacetic acid, although the increase of prevaporation performance was not so high as those previously obtained by the grafted poly(sodium acrylate) ‐type membranes. Pervaporation characteristics of these membranes were discussed from the ionized states of the permselective layers analyzed by IR and ESCA.
Hierarchical structure in LCP/PET blends
Authors: Silverstein M. S. , Hiltner A. , Baer E. 
Published: April 2003

AbstractThe structural hierarchy in injection molded blends of poly(ethylene terephthalate) (PET) and a commercial liquid crystal polymer (LCP), two immiscible polymers, was characterized at various blend compositions. The macroscopic core and skin have a gradient structure and are subdivided into ordered and disordered layers. The sublayers consist of rodlike domains at 25% LCP. The domains become thinner, longer, and more fibril‐like with increasing LCP concentration. The interconnection between the LCP domains also becomes more significant at higher LCP concentrations. The highest degree of orientation in the injection direction is at the mold surface and the lowest at the sample center. The LCP orientation reflects the elongational and fountain flow in the mold and increases with increasing LCP concentration. Schematic structural models were used to illustrate the levels of structure in these blends. A minimum exists in the tensile strength, elongation at break, and impact strength with varying blend composition at approximately 50% LCP. The tensile strength of the LCP‐rich blends is significantly lowered by the presence of a weldline or an angle between the stress and orientation directions. The unique mechanical properties of the LCP depend on the formation of a highly oriented and highly connected hierarchical structure that does not exist in blends with 75% or less LCP.
Thermal stability in air of acrylonitrile‐grafted polyethylene by electron beam prior irradiation
Authors: Mori K. , Koshiishi K. , Masuhara K. 
Published: April 2003

AbstractStudies were made of the thermal softening and degradation behavior in air of low‐ and high‐density polyethylene (PE) grafted with acrylonitrile (AN) by electron beam prior irradiation in nitrogen. It was found that both LDPE and HDPE were made to exhibit higher softening points by grafting and that this tendency increased with increasing percent graft. The starting temperatures of the thermal degradation and thermogravimetric curves were also found to shift to higher temperatures. On the other hand, in marked contrast to the thermal softening and degradation behavior of grafted PE in air, its behavior in nitrogen showed substantial dependance on oxidative degradation, suggesting that the oxidation of PE was inhibited by polyacrylonitrile (PAN), which forms graft chains. It was considered that the oxidation‐inhibiting mechanism of PAN produced in the amorphous regions prevents oxygen from dissolving and diffusing into the amorphous phase, thus inhibiting the oxidative degradation of PE, and that, when heated, PAN undergoes nitrile oligomerization and the nitrile oligomer end radicals act to trap those radicals which participate in PE oxidative degradation.