bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of urea–formaldehyde polymer cure by infrared
Authors: Myers George E. 
Published: April 2003

AbstractAn examination has been made of the capability of conventional infrared analysis to define the structure of urea–formaldehyde (UF) polymers in the cured, crosslinked state. Proton NMR and infrared measurements of model compounds and uncured UF polymers were combined with infrared observations during polymer cure. The existing interpretation of UF polymer infrared spectra was clarified and a partial confirmation of the UF polymer cure mechanism obtained. However, it was concluded that conventional infrared possesses distinct limitations for defining the UF cure process in great detail, and it is hoped that the new solid‐sample NMR methods will prove capable of the desired structural determination in the cured state.
Limiting oxygen indices of silicone block polymer
Authors: Kambour R. P. , Klopfer H. J. , Smith S. A. 
Published: April 2003

AbstractThe limiting oxygen index (LOI) has been determined for each of a large number of silicone‐containing resins, principally dimethylsiloxane (DMS) block polymers varying widely in DMS content and hard block type. A synergistic enhancement in LOI of varying strength is seen in several families of resins. For the major families explored, the synergism varies with hard block type in roughly the following order: bisphenol‐A carbonate and bisphenol fluorenone carbonate > styrene and 2,6‐diphenyl‐1,4‐phenylene oxide > bisphenol chloral polycarbonate > methyl methacrylate and phenolphthalein carbonate, the enhancement being nil in the last case. Strength of the synergism is discussed in terms of DMS degree of dispersion, char‐forming tendencies, melt viscosity, and other factors.
High‐performance column adsorption chromatography of random copolymers styrene–acrylics
Authors: Danielewicz M. , Kubín M. 
Published: April 2003

AbstractRandom copolymers of styrene with acrylics can be separated according to their chemical composition by gradient column adsorption chromatography on silica. The composition of the mobile phase that can displace a given copolymer from the silica surface is independent of the shape of the solvent strength gradient and also above the sample molecular weight of ca. M = 100,000.
Synthesis and properties of polyesterimides and their isomers
Authors: Maiti Sukumar , Das Sajal 
Published: April 2003

AbstractA new type of polyesterimide has been synthesized by polycondensation of a dicarboxylic acid containing an internal imide group with ethylene glycol. The dicarboxylic acid was synthesized by reacting aminobenzoic acid with trimellitic acid anhydride in N, N‐dimethylformamide solution. Three isomeric (ortho, meta, and para) polyesterimides were prepared from the respective isomer of the dicarboxylic acid. The solubility characteristics, solubility parameters, solution viscosity behavior, density, crystallinity, and thermal properties of these three isomeric polyesterimides were discussed. Some generalizations about structure–property relationship in polyesterimides were also made. It was found that while the ortho and meta isomers of the polyesterimide are amorphous, the para isomer tends to be somewhat crystalline and consequently less soluble, even in polar solvents. The thermal behavior of the meta isomer resembles closely that of the para isomer. The thermal stability of these isomers follows the order para ≥ meta > ortho.
Wet poly(vinyl chloride) membrane
Authors: Hirose Sachio , Yasukawa Eiki , Nose Takuhei 
Published: April 2003

AbstractWet, porous, and semipermeable poly(vinyl chloride) (PVC) membrane prepared from a binary system, PVC and dimethylformamide, by immersing in alcohols or ethers was studied. The pore dimensions of the wet PVC membrane were from 0.01 to 0.05 μm, calculated from hydrodynamic permeability by using experimental values such as water flux and water content. They agreed reasonably well with the dimension of the pores which prevented the protein passing through the membrane, observed by SEM photographs. Formation of the wet PVC membrane can be explained by slow phase separation and slow leaching of the casting solution immersed in alcohols and ethers such as methanol and ethylene glycol monomethyl ether.
Simulation model for the emulsion copolymerization of acrylonitrile and styrene in azeotropic composition
Authors: Lin Chen‐Chong , Ku Hwar‐Ching , Chiu Wen‐Yen 
Published: April 2003

AbstractA simulation model based on the “unit segment” concept which provides prediction of conversion and molecular weight of product, is proposed for the emulsion polymerization of AN and St in azeotropic composition. Effects of initiator concentration and emulsifier concentration on conversion and molecular weight were studied experimentally and theoretically. It is found that the desorption of AN radicals should be taken into account, and the number of radicals per particle is always less than 0.5. The concentration of polymer particles is proportional to the 0.58 power in respect of the emulsifier concentration and to the 0.35 power in respect of the initiator concentration. The auto‐acceleration effect becomes significant when both initial emulsifier concentration and initiator concentration decrease, which influences the average molecular weight of the products. The azeotropic composition of AN–St is 28.5:71.5 by weight for this system at 60°C reaction temperature.
Gradient interpenetrating polymer networks. I. Poly(ether urethane) and polyacrylamide IPN
Authors: Dror M. , Elsabee M. Z. , Berry G. C. 
Published: April 2003

AbstractThe swelling properties of poly(ether urethane)s and the preparation of interpenetrating polymer networks (IPNs) from a poly(ether urethane) thermoplastic elastomer and hydrogel forming polyacrylamide have been studied. The acrylamide monomer was polymerized with simultaneous crosslink formation, in the presence of the swollen thermoplastic elastomer. Upon removal of the swelling solvent, an IPN was obtained which absorbed water in the manner of a hydrogel but had mechanical properties superior to a hydrogel.
Hydrolysis of polycarbonate to yield BPA
Authors: Bair H. E. , Falcone D. R. , Hellman M. Y. , Johnson G. E. , Kelleher P. G. 
Published: April 2003

AbstractElevated temperatures and high humidity decrease the molecular weight and impact strength of polycarbonate. Hydrolysis of injection molded polycarbonate (PC) bars stored in glass containers at 85°C and 96% relative humidity (RH) produced brown surface crystals within 30 days. Aging of PC bars at 96% RH and temperatures of 70°C and lower for longer periods of time formed a brown liquid coating on the PC. X‐ray, DSC, and GPC measurements indicated that about 70 wt% of the surface crystals were bisphenol A (BPA). The remaining portion of hydrolysis products appeared to be higher molecular weight oligomers of BPA. The brown liquid was composed of supercooled liquid BPA, BPA oligomers, and water. Initial growth of BPA on the surface of a PC bar took place at the interface between the PC and the glass wall of the container. Apparently a water soluble extract from the glass container accelerated the hydrolytic degradation of PC; nevertheless, hydrolysis of PC occurred in the absence of glass—although at a slower rate. Hydrolysis studies were carried out on several commercial PC formulations. The PC resin containing only a heat stabilizer was least affected. Of the fiame retardant grades, the brominated PC hydrolyzed less rapidly than these particular compositions containing alkali metal sulfonic acid salts. A glass fiber reinforced PC was less stable than its unfilled parent compound. A hydrolytic stabilizer was ineffective against the attack of water under these conditions.
The effect of heat setting on the structure and mechanical properties of poly(ethylene terephthalate) fiber. IV. Tensile properties other than modulus and their dependence on structure
Authors: Gupta V. B. , Kumar Satish 
Published: April 2003

AbstractThe stress‐strain characteristics of poly(ethylene terephthalate) fibers, heat set under different conditions have been studied under tension, and mechanical properties such as tenacity, yield point, elongation at break, and work of rupture are presented and discussed. An attempt has been made to correlate these mechanical properties with structural parameters. The orientation of the molecules in the fiber and the size and distribution of the crystallites emerge as important factors controlling the tensile properties.
Plasma etching durability of poly(methyl methacrylate)
Authors: Harada Katsuhiro 
Published: April 2003

AbstractThe decomposition of poly(methyl methacrylate) (PMMA), as a positive resist, in CF4/O2 plasma etching has been studied in the thin film state in order to clarify the factors influencing the dry etching durability of resists. It becomes clear that the major PMMA decomposition in CF4/O2 plasma etching proceeds by the mechanism of random chain scission because very small kinetic chain lengths are estimated from the gel permeation chromatography data. The Arrhenius plots for the plasma etching rate of PMMA bend above about the glass transition temperature (Tg), where rapid increase of the etching rate and remarkable pattern deformation are observed. Activation energy of the PMMA etching rate which is changed by oxygen concentration and rf power indicates various values from 3.1 to 6.5 kcal/mol below about Tg. The result of molecular weight variation in the cross section of the film suggests that the active species permeate into the film with fairly large speed and the PMMA decomposition occurs not only at the film surface but also at deep layer of the film.
Surface property modification of aromatic polyamides by microwave plasmas
Authors: Wertheimer M. R. , Schreiber H. P. 
Published: April 2003

AbstractVarious microwave plasma treatments were applied to Kevlar in the form of multifilament fabric and single fiber. Plasma‐modified fabrics were used to construct two‐ply laminates using a triazine resin adhesive. Very significant increases in the bond strength of laminates may be attributed to the plasma treatments; the effectiveness of plasma treatment is best utilized by reducing to a minimum the time interval between plasma exposure and contact of treated substrate with impregnating (adhesive) fluid. Mechanical properties of single Kevlar fibers seem to deteriorate somewhat on plasma exposure, but the cohesive strength of multifilament cloth is enhanced by the same treatments.
Simultaneous diffusion of benzyl alcohol into plasticized poly(vinyl chloride) and of plasticizer from polymer into liquid
Authors: Messadi D. , Vergnaud J. M. 
Published: April 2003

AbstractThe diffusion of benzyl alcohol and plasticizer in compression‐molded sheets of plasticized poly(vinyl chloride) was studied over the temperature range 30–55°C. A simultaneous diffusion occurred for benzyl alcohol into polymer and for dioctyl phthalate as plasticizer from polymer into liquid when the polymer was soaked in benzyl alcohol. The concentration of benzyl alcohol in polymer increased, rose to a maximum, and then decreased. Diffusion coefficients were measured by considering a nonsteady‐state phenomenon for plasticizer concentration of 25, 38, and 50 wt %, both for dioctyl phthalate and benzyl alcohol. Plasticizer concentration and temperature were found to play an important role.
Physical aging studies of semicrystalline poly(ethylene terephthalate)
Authors: Tant Martin R. , Wilkes Garth L. 
Published: April 2003

AbstractPhysical aging of semicrystalline poly(ethylene terephthalate) has been investigated as a function of crystalline content. Stress–strain, stress relaxation, and differential scanning calorimetry experiments were used to monitor the physical aging process. Both the overall extent and the rate of physical aging in this material decrease with increasing crystallinity. Several possible reasons for this behavior are advanced and discussed. It was also found that the drawing behavior of amorphous PET changes significantly as physical aging progresses. Specifically, for samples aged and then elongated, the extent of localized deformation (necking) and associated strain‐induced crystallization was greater for samples aged for longer periods of time.
Structure–property relationships of a new series of segmented polyether–polyester copolymers
Authors: Mody P. C. , Wilkes G. L. , Wagener K. B. 
Published: April 2003

AbstractThe work reported focuses on the structure–property relationships of a new series of segmented polyether–polyester copolymers. Poly(ethylene oxide‐hydantoin) is the soft segment, while poly(tetramethylene terephthalate) is the hard block and is suceptible to crystallization. The structure–property relationships have been addressed under three different subdivisions: (1) mechanical properties, (2) orientation effects and phase separation, and (3) morphology and superstructure. Where possible, a correlation has been made between these three categories.
Characterization by tin‐specific size exclusion chromatography of the free radical copolymerization of tributyltin methacrylate and methyl methacrylate
Authors: Parks E. J. , Brinckman F. E. , Mullin C. E. , Andersen D. M. , Castelli V. J. 
Published: April 2003

AbstractCopolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) comprise an important class of biocidal slow‐release organometallic polymers (OMPs). Little is known of the kinetics and mechanism of copolymerization. TBTM and MMA were copolymerized in the presence of a free radical initiator (benzoyl peroxide) at 80.1°C. Aliquots, taken at preselected intervals from 0 to 1440 min, were fractionated by size exclusion chromatography (SEC) coupled with ultraviolet (UV) and tin‐specific graphite furnace atomic absorption (GFAA) detectors. A UV absorbance observed at 254 nm was associated with low‐molecular‐weight species, decreasing in concentration continuously with time of reaction. Tin‐specific GFAA indicated a decrease in low‐molecular‐weight species (ca. 350 daltons) with concurrent increases in high‐molecular‐weight species (ca. 40,000 daltons). The fraction of high molecular‐weight increased as a linear function of the logarithm of the time of reaction. SEC–UV–GFAA thus provides a tool of major importance for characterizing the time dependence and continuity of the process by which monomers of TBTM are converted to a useful bioactive slow‐release coating material.
Radiation grafting of acrylic acid onto fluorine‐containing polymers. I. Kinetic study of preirradiation grafting onto poly(tetrafluoroethylene)
Authors: Hegazy El‐Sayed A. , Ishigaki Isao , Okamoto Jiro 
Published: April 2003

AbstractPreirradiation grafting of acrylic acid onto poly(tetrafluoroethylene) film was studied. The trapped radicals formed upon irradiation are able to induce graft polymerization under appropriate conditions. The influence of the grafting conditions were analyzed kinetically. The grafting reaction begins close to the film surface and proceeds into the center with progressive monomer diffusion through the grafted layer. The dependences of the grafting rate on preirradiation dose and monomer concentration were found to be 0.2 and 1.1 order, respectively. The overall activation energies for this grafting were calculated to be 15.2 and 4.8 kcal/mol below and above 35°C, respectively. The relationship between the grafting rate and film thickness gave a negative first‐order dependence.
Flows of dilute hydrolyzed polyacrylamide solutions in porous media under various solvent conditions
Authors: Durst F. , Haas R. , Kaczmar B. U. 
Published: April 2003

AbstractExperimental results on pressure losses of flows of dilute polymer solutions through porous media are summarized. The polymer products employed in this study consisted of partially hydrolyzed polyacrylamides (HPAM) with different degrees of hydrolysis. The effect of the hydrolysis on the pressure drop is investigated in a porous media test section designed to minimize polymer degradation. The investigations were carried out for various solvent conditions, and it is shown that the maximum increase in pressure drop is mainly dependent on the molecular weight of the polymers. The onset of the polymer action is measured for various fluid and solvent properties. Particular attention is given to measurements near θ‐conditions. The results stress the importance of the solvent properties on the actions of the polymers and on the resultant pressure drop for porous media flows. The addition of salt ions to solutions of partially hydrolyzed polyacrylamides yields onset behavior previously observed for nonionic polymers. The differences measured between various solvent properties can be explained by the actual hydrodynamic molecule dimensions for a given molecular weight and polymer concentration. To quantify the influences of the solvent properties on the polymers, measurements were carried out in aqueous solutions for various pH values and therefore at various degrees of dissociation. The importance of separating polymer effects caused by their linear dimension in the solution from those that are introduced by and increase in solvent viscosity is shown. Measurements were performed to quantify the effects of solvent viscosity on the polymer action and to separate these effects from those due to changes in molecule dimensions. The implications of the present results are stressed in connection with applications of polymer solutions in tertiary oil recovery, and the positive features of the molecule actions on flow in such applications are described.
Reactive polymers. XXXIII. The influence of the suspension stabilizer on the morphology of a suspension polymer
Authors: Horák D. , Pelzbauer Z. , Ŝvec F. , Kálal J. 
Published: April 2003

AbstractSorbents based on glycidyl methacrylate were used in an investigation of the effect of the type of the suspension stabilizer and of its concentration on the shape, size, and morphology of beads consisting of submicroscopic particles (globules). Of many stabilizers used, only poly(vinyl pyrro‐lidone) and poly(vinyl alcohol) led to the formation of regular spherical beads with a surface shell. As expected, beads obtained using a stabilizer producing higher interfacial tension poly(vinyl pyrrolidone)‐K 90 were much larger. A similar effect may be reached by lowering the concentration of poly(vinyl alcohol), if this lowering is accompanied by a rise in the interfacial tension. Despite this, however, the surface shell was not compact in this relatively narrow range of interfacial ten‐sions.
Binary and ternary blends of poly(vinyl chloride), hytrel, and a polyurethane
Authors: Hourston D. J. , Hughes I. D. 
Published: April 2003

AbstractBinary blends of poly(vinyl chloride) and a poly(ether urethane) containing 20 and 40 weight percent, respectively, of poly(vinyl chloride) have been prepared by solution blending from tetrahydrofuran and their degree of mixing investigated using dynamic mechanical analysis. In the polyurethane, transitions were found at −19°C and −119°C. The former was attributed to the glass transition and the latter to a Schatzki type of motion of the polyether sequences. This latter transition occurred at a temperature which is higher than the literature value for the low temperature transition in poly(tetrahydrofuran), which is equivalent to the polyether sequence in the polyurethane. This discrepancy is attributed to the influence of neighboring hard segments present because of incomplete segmental phase separation of the polyurethane. For the blends only one very broad transition was observed, indicating that there was substantial mixing of these two polymers. Three ternary blends were prepared, also by solution blending, containing poly(vinyl chloride), Hytrel, and the polyurethane in the ratios 1:1:1, 1:2:1, and 2:1:1, respectively. In the first two blends there was clear evidence of phase separation. It was only in the 2:1:1 blend that an apparently significantly compatible material resulted.
Axial dispersion in laminar flow of polymer solutions through coiled tubes
Authors: Saxena Alok K. , Nigam K. D. P. 
Published: April 2003

AbstractThe results of an experimental study on axial dispersion in laminar flow of non‐Newtonian fluids through helical coils are reported. The ranges of variables covered are 10.5 ≤ λ ≤ 220, 0.6 ≤ n ≤ 1.0, 0.1 < NRegn < 140, and 0.04 < τ > 2.2. The condition for the applicability of Taylor's dispersion model is also reported. It is found that coiling results in a dispersion reduced over that in a straight tube.
Natural and accelerated weathering of some polyblends
Authors: Feldman D. 
Published: April 2003

AbstractA weathering study has been carried out on a polyurethane elastomeric adhesive and its polyblends with the following vinyl polymers: poly(vinyl chloride), poly(vinyl alcohol), poly(vinyl acetate), and vinyl acetate—vinyl chloride copolymer. Stress‐strain measurements were done on an Instron model 1125 testing machine after aging at normal room conditions, outside, and in an artificial weathering chamber. The observed modifications of the mechanical properties can be attributed to a decrease of the molecular weight of the polymers involved during the cryolysis process; this process is less significant for natural weathering than for artificial weathering. Results are discussed and conclusions drawn.
Catalyzed polymerization of cycloolefins
Authors: Tsonis C. P. 
Published: April 2003

AbstractThe catalyzed polymerization of cycloolefins may lead to a ring retention polymer product or to a polyalkenamer. The homogeneous catalysts, derived from V, W, Mo, and Re transition metal complexes, normally require the synergistic use of an alkylaluminum cocatalyst. Trans‐1, 5‐poly‐alkenamers exhibit elastomeric properties and might be suitable for tire manufacture.
A new epoxy resin/hardener system with variable processing and end properties
Authors: Eldin Sameer H. , Stockinger Friedrich , Lohse Friedrich , Rihs Grety 
Published: April 2003

AbstractA combination of a standard bisphenol‐A liquid epoxy resin and a zinc–pyrrolidone–carboxylate complex with a long chain poly(oxypropylene diamine) (Jeffamine D 2000) has been found to give variable processing and end properties over a very wide range, e.g., pot life < 1–70 days, Martens Heat‐Distortion Temperature < 25–124°C and elongation at break 35–1%. The variation in properties is achieved simply by changing the epoxy/complex ratio. The very reactive high elongation formulation is thought to be the result of a very fast zinc catalyzed amine/epoxy polyaddition reaction and the low reactivity rigid formulation to be due to zinc‐complex initiated anionic homopolymerization of the epoxy resin. The borderline concentrations are approximately 200 and 10 phr of the complex, respectively.
Impact testing of a thermosetting polymer (allyl diglyol carbonate–CR39)®
Authors: Howes V. R. , Goldsmid J. M. , Silk R. K. , Were A. V. 
Published: April 2003

AbstractAllyl diglycol carbonate (CR39)® is a thermosetting polymer of interest both as an ophthalmic material and as a material intermediate between brittle and ductile solids. The response to impact in the crack‐threshold range has been studied and compared to that of glass. The energy absorbed upon impact, the plastic deformation, and the crack resistance are all found to be greater for CR39, and the relationships between these factors are discussed. The developments of impact response for CR39 with increasing temperature and increasing impact energy beyond the crack‐threshold range have also been studied.