bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propylene polymerization in a semibatch slurry reactor over supported TiCl4/MgCl2/ethyl benzoate/triethyl aluminum catalyst. II. A kinetic study based on a multisite model
Authors: Dumas Constantine , Hsu Cheng C. 
Published: April 2003

AbstractIn propylene polymerization over TiCl4/MgCl2/ethyl benzoate (EB)/triethyl aluminum (TEA) catalysts, experimental evidence strongly suggests that active sites have differing propagation and termination rate constants. Although the chemical structure of these sites may be quite similar, their location on the support may affect their polymerization activity, and this results in a distribution of the propagation and deactivation rate constants. To model this type of system, we developed a kinetic model accounting for multiple active sites. The model was fitted to simulated polymerization data to investigate the validity of mathematical approximations used in the derivation of the model equation. Using experimental data, the adequacy of the model was tested, and the statistical inference of parameter estimation was also discussed. The effects of experimental operating variables and additives on the kinetic model parameters revealed an important insight into the fundamentals of this system. The optimum productivity commonly observed has been shown to be the result of differing rates of increase of both propagation and termination rates with Al/Ti ratio and temperature. Kinetic evidence also suggests that the additive selectively poisons atactic‐specific sites.
Dielectric relaxation study of low‐density polyethylene by thermally stimulated depolarization currents and thermal sampling
Authors: Dueñas J. M. Meseguer , Ribelles J. L. Gomez , Calleja R. Diaz 
Published: April 2003

AbstractThe dielectric relaxation zone of a low‐density polyethylene has been studied by thermally stimulated depolarization currents (TSDC) and thermal sampling (TS). Three relaxations have been found in this zone, which have been labeled γI, γII, and γIII in decreasing order of temperature. Samples of different crystallinities were subjected to several thermal treatments in order to study the molecular origin of each relaxation. The γI relaxation intensity changes with the thermal treatment, while the intensity of the γI relaxation is only slightly modified. Using TS it has been proved that the γI relaxation fulfils the compensation law with a high level of significance. Nevertheless, the experimental data are not enough to verity the γI and γIII relaxation.
Preparation and properties of UV‐autocurable BTDA‐based polyurethane methacrylates
Authors: Chiang Wen‐Yen , Chan Shao‐Ching 
Published: April 2003

AbstractSyntheses of several UV‐autocurable methacrylourethanes and the effects of polyol type on their properties are investigated. Autocurable benzophenone tetracarboxylic dianhydride (BTDA)‐based polyurethane methacrylates are prepared by addition reaction from benzophenone tetracarboxylic dianhydride (BTDA), 2,4‐toluene diisocyanate (TDI), 2‐hydroxyethyl methacrylate (HEMA), and polyol (polyethylene glycol, polydiethylene succinate, polydiethylene maleate, or polydiethylene hexamethylene‐dicarbamate). Autocurable oligomers possess good pot life and are cured rapidly when exposed to ultraviolet (UV) radiation without the addition of photoinitiator. The different polyols are used to obtain wide range properties of cured films with a glass transition temperature (Tg) range of ‐10.5‐5.5°C. Increasing the Tg of polyol shifts the dynamic mechanical storage modulus and loss factor of the cured film to high temperature. For practical application, oligomer is mixed with reactive monomers to bring the systems to a workable viscosity at room temperature. Among the monomers, the higher the composition of hydroxyethyl acrylate in the oligomer‐monomer system, the higher the curing rate of the system as compared with neat oligomer. Moreover, increasing the chain length of dimethacrylate monomers results in a decrease in breaking strength from 160 to 140 kg/cm2, in Young's modulus from 771 to 400 kg/cm2, and in glass transition temperature from 18 to 6.5°C, while the elongation at breaking increases from 70 to 130%.
A zeolite/polymer membrane for separation of ethanol‐water azeotrope
Authors: Goldman Mariana , Fraenkel Dan , Levin Gideon 
Published: April 2003

AbstractA novel membrane effective in the separation of ethanol‐water mixtures by pervaporation was made by combining zeolite NaA and poly(vinyl chloride) modified by 2‐(2′‐butoxyethoxy)ethyl thiolate. Under ambient conditions, a separation factor (α) of 29 and pervaporability (P) of 4 × 10−4 g m−1 h−1 were obtained for the azeotropic mixture whereas, in the absence of zeolite, the respective values were 7 and 7 × 10−5. A mechanism was proposed relating the preferential water transport at ≈︁ 50% zeolite content to an interfacial “phase” between the zeolite and the modified polymer.
Effect of diantimony trioxide on direct esterification between terephthalic acid and ethylene glycol
Authors: Yamada Toshiro 
Published: April 2003

AbstractExperiments at various Sb2O3 concentrations were made in a pilot plant and the effect of Sb2O3 on continuous esterification between terephthalic acid (TPA) and ethylene glycol (EG) was obtained. Reaction rate constants of the previously reported reaction scheme were determined to fit with the experimental data obtained. It was found that the effect of Sb2O3 on reaction rate constant (ki) can be expressed as follows.

k1 = (3.75 × 10−4Sb + 1.0) × 1.5657 × 109exp(−19,640/RT)
k2 = (4.75 × 10−4Sb + 1.0) × 1.5515 × 108exp(−18,140/RT)
k3 = (6.25 × 10−4Sb + 1.0) × 3.5165 × 109exp(−22,310/RT)
k4 = (4.50 × 10−4Sb + 1.0) × 6.7640 × 107exp(−18,380/RT)
k5 = (3.50 × 10−4Sb + 1.0) × 7.7069 × exp(−2810/RT)
k6 = (1.75 × 10−4Sb + 1.0) × 6.2595 × 106exp(−14.960/RT)
k7 = (3.75 × 10−4Sb + 1.0) × 2.0583 × 1015exp(−42,520/RT)

Simulation of esterification with these reaction rate constants at various Sb2O3 concentrations was made and the following results were obtained.

Sb2O3 accelerates the esterification reaction between TPA and EG.
Sb2O3 accelerates the main reaction and its effects on side reactions are minor. The higher the addition rate of Sb2O3, the lower the carboxyl end‐group concentration (AV) and diethylene glycol content (DEG).
The comparison between simulation with potassium titanium oxyoxalate (PTO) in the previous report and with Sb2O3 in the present report shows that the acceleration of polycondensation reaction by Sb2O3 is higher. DEG formation rate is lower with PTO than Sb2O3.
Rheological behavior of SAN/PC blends under extremely high shear rate
Authors: Takahashi Hideroh , Matsuoka Takaaki , Ohta Takashi , Fukumori Kenzo , Kurauchi Toshio , Kamigaito Osami 
Published: April 2003

AbstractExtremely high shear rate processing was applied to the compound system of acrylonitrilestyrene copolymer/polycarbonate (SAN/PC). The viscosity was measured against the shear rate up to 107 s−1.The first non‐Newtonian region, the second Newtonian region and second non‐Newtonian region were observed in the compound system. The occurrence of these regions are very similar to those in the parent polymers, SAN and PC. For the calculation of the viscosity‐shear rate curve, a concentric multilayer model was proposed. It gives good agreement between the calculated value and the measured one. A new mechanism for the occurrence of the non‐Newtonian, second Newtonian, and second non‐Newtonian regions was proposed. Nuclear spin–spin relaxation time measured on SAN, T2, seems to be consistent with the consideration that the occurrence of non‐Newtonian region, second Newtonian region, and second non‐Newtonian region are caused, respectively, by the disentanglement, near saturation of disentanglement associated with snapping of macromolecules, and reentanglement through recoiling of snapped macromolecules, and further snapping of the macromolecules, which is inconsistent with the proposed explanation.
A processable prepolymer for the preparation of a stable conductive polymer
Authors: Walton Theodore R. 
Published: April 2003

AbstractWe recently reported1 the synthesis and polymerization of a completely conjugated acetylene terminated prepolymer into an intrinsically conducting organic polymer. Although this polymer exhibited high thermal and environmental stability, its processing window, i.e., the temperature at which it melted vs. the temperature of the highly exothermic cure, was narrow. We now report the synthesis and polymerization of an isomer of this acetylene terminated material. This change in structure resulted in a 63°C decrease in the melting point (87 vs. 150°C) that provides a more than adequate liquid range between melting and the on‐set of curing. Along with the greatly improved processing, this isomer results in an intrinsically conducting, thermally and oxidatively stable polymer equivalent to the original material.
Studies on graft copolymerization of cyclohexyl methacrylate onto 1,2‐polybutadiene
Authors: Liaw Der‐Jang , Lin Lei‐Li 
Published: April 2003

AbstractThe free radical grafting of cyclohexyl methacrylate (CMA) onto 1,2‐polybutadiene (1,2‐PBD) in benzene solution at 60°C was studied. The graft copolymer was characterized by IR, NMR, DSC, and intrinsic viscosity measurements. The polymerization of CMA shows normal kinetic behavior when the PBD concentration is kept below 1.0 monomer mol/L. The rate of grafting was determined at different reaction times, monomer concentrations, initiator concentrations, backbone concentrations, temperatures, and concentrations of the zinc chloride additive. The performance of the graft copolymer used as adhesive was also investigated for bonding of PVC/PVC film.
Simple dilatometer for polymer density and thermal expansivity measurements
Authors: Tyagi O. S. , Deshpande D. D. 
Published: April 2003

AbstractA dilatometer is described to study the temperature dependence of density (ρ) of solid and semiliquid polymers and the following linear relations have been established. Atactic poly(vinylisobutyl ether) (25–90°C): ρ = 0.9166 − 7.15 × 10−4 × T. Isotactic poly(vinylisobutyl ether) (25–70°C): ρ = 0.9184 − 7.13 × 10−4 × T. Poly(n‐butyl methacrylate) (90–150°C): ρ = 1.0622 − 8.41 × 10−4 × T. Poly(dimethyl siloxane) (30–51°C, using Lipkins pycnometer): ρ = 0.9846 − 8.81 × 10−4 × T; where ρ is in g.cm−3, temperature T is in Celsius, and the linearity correlation coefficient r is better than 0.9998. Their volume–temperature plots are also linear. As the plots of polyn‐butyl methacrylate curved slightly near its glass transition (20°C), the quadratic equation ρ = 1.0402 − 4.79 × 10−4 × T − 1.46 × 10−6 × T2 (standard deviation = 1.57 × 10−3) has been suggested for the entire range of 30–150°C scrutinized in this study. The data have been utilized to derive thermal expansivity and some equation‐of‐state parameters of the polymers at the reference temperature (ca. 20°C).
Design and applications of a solid‐phase oxidizing reagent consisting of a crosslinked polystyrene matrix and a t‐butyl hypochlorite function separated by a trimethylene spacer
Authors: Sreekumar K. , Pillai V. N. Rajasekharan 
Published: April 2003

AbstractA crosslinked polystyrene–supported solid‐phase analogue of t‐butyl hypochlorite containing a trimethylene spacer group between the polymer matrix and the t‐butyl hypochlorite function was prepared and used as a recyclable oxidizing reagent for alcohols. The synthetic route to this new polymeric reagent involved a seven‐step polymer‐analogous reaction starting from styrene‐divinyl benzene 2%‐crosslinked polymer. A β‐ketopropionic acid function was introduced into the polystyrene matrix by Friedel–Crafts reaction with succinic anhydride. The keto function in the resulting polymer (2) (capacity, 3.57 meq of COCH2CH2COOH/g) was converted to the methylene group by Clemmensen reduction using zinc amalgam and HCl. The carboxyl function in the product polymer (3) was converted to the acylmalonic ester function by malonic ester synthesis through the reaction of the polymeric acid chloride (4) with ethoxymagnesium diethylmalonate. The polymeric acyl malonic ester (5) was decarboxylated to yield the 2‐oxopentyl polystyrene resin (6). This on Grignard reaction with methyl magnesium iodide followed by hydrolysis afforded the polystyrene derivative with the t‐butyl alcohol function separated by three methylene groups (7). The t‐butyl alcohol resin (7) was converted to the corresponding hypochlorite resin (8) by reaction with sodium hypochlorite. The resin was found to have a capacity of 2.84 mmol Cl/g by iodometric analysis. The capacities of the resins 2–8 were determined from the weight changes in the corresponding conversions and verified by quantitative determination of the functional groups. This new hypochlorite was found to oxidize alcohols to carbonyl compounds in 85–98% yield. The oxidizing efficiency of this new reagent was found to be significantly greater than those of the reagents containing only one spacer and no spacer between the reagent function and the polymer support. The presence of a 3‐methylene spacer also facilitated the hypochlorite formation step significantly.
Studies on swelling of cotton fibers in alkali metal hydroxides. I. Influence of variations in fine structure on tensile behavior
Authors: Sreenivasan S. , Iyer P. Bhama , Patel G. S. , Chidambareswaran P. K. 
Published: April 2003

AbstractA study on cotton fibers swollen slack at ambient temperature in different concentrations of LiOH and KOH indicates that fibers swollen in KOH have higher disorder. Conversion to cellulose II results from swelling in both the reagents, although, with KOH swelling, it begins at a lower concentration. Further, retention of tenacity is higher at all gauge lengths after KOH swelling. Analysis of the influence of fine structure on tensile properties showed some specificity, mainly attributable to cationic size differences of the swelling agents.
Large scale preparation of melamine‐based superplasticizing admixtures. I. Process optimization
Authors: Dairanieh I. S. , Absi‐Halabi M. , Lahalih S. , Al‐Khalid T. 
Published: April 2003

AbstractThe process for preparing novel sulfonated melamine–formaldehyde resins was studied in detail with the objective of optimizing the production cycle time. The effects of minimizing temperature differences between consecutive reaction steps and reducing reaction time of selected steps of the process were assessed. Experimental work focused on increasing the polymerization step temperature and decreasing its time, resulting in considerable savings in the process time and energy consumption. The resin of the optimized cycle was found to have excellent superplasticizing properties when added to concrete mixes.
Synthesis of functional polymers by radiation‐induced grafting of acrolein onto polyethylene film
Authors: Omichi H. , Katakai A. , Okamoto J. 
Published: April 2003

AbstractAcrolein was grafted onto polyethylene film with radiation energy in order to make functional polymers containing hydrazone, oxime, and oxyacid. The kinetic analysis of the grafting reaction revealed that the irradiation dose affected not only the initiation but also the propagation and termination steps. The activation energies were 12.5 kcal/mol for propagation and 23.3 kcal/mol for termination, respectively. All the introduced aldehyde groups, free, hydrolyzed, and used for ring formation, participated in the reaction with phenylhydrazine. The conversions of aldehyde group to hydrazone, oxime, and oxyacid were small when the grafting yield of acrolein was high.
Heat‐resistant adhesive resins derived from bismaleimides and bisnadimides containing amide linkages
Authors: Mikroyannidis John A. , Melissaris Anastasios P. 
Published: April 2003

AbstractA novel class of bismaleimides and bisnadimides containing amide linkages in their backbones were synthesized and characterized. The synthesis of these polymer precursors was carried out by reacting a diamine containing amide linkages with maleic/nadic anhydride. They were alternatively prepared by reacting the monomaleamic/monoadiamic acid of an aromatic diamine (1 mol) with terephthaloyl chloride (0.5 mol) and subsequent cyclodehydration. The latter new preparation method circumvented the hydrogeneration necessary in the first method of synthesis. The monomers were characterized by infrared (IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopy. Differential thermal analysis (DTA) of monomers showed that bisnadimide and bismethylnadimide were polymerized at lower temperatures than the corresponding bismaleimide. Thermogravimetric analysis (TGA) in nitrogen and air atmosphere revealed that all polymers were stable up to 321–363°C. Their char yield at 800°C under anaerobic conditions was 49–67%.
Viscosity–temperature relationships for linear and 12‐arm star polystyrenes in dilute solution
Authors: Liouni Maria , Touloupis Costas , Hadjichristidis Nikos , Mays Jimmy W. 
Published: April 2003

AbstractThe actual viscosities (cP) of dilute solutions of linear and 12‐arm star polystyrenes were measured in benzene, a good solvent, and cyclohexane, a poor to moderate solvent, as a function of temperature. The equations of Moore, previously established for solutions of linear polymers, were also found to be valid for star polystyrenes. A branching parameter b was defined which is essentially the same as g′ = [η]br/[η]1. The values of b found in benzene are close to the value of g′ for 12‐arm star polystyrene in toluene, another thermodynamically good solvent. It thus appears that Moore's relationships have at least limited utility in studying branching in polymers.
Polystyrene–polyisobutylene network composites from in situ polymerizations
Authors: Fu F.‐S. , Mark J. E. 
Published: April 2003

AbstractCrosslinked networks of butyl rubber [polyisobutylene (PIB) with 2 mol % unsaturation] were swelled with various amounts of styrene containing 0.25–4.6 wt % benzoyl peroxide as initiator. Polymerization of the styrene in situ, by increase in temperature, gave novel elastomeric composites. Scanning electron micrographs suggest phase separation which is locked in at the microscopic level, with no evidence for the particulate domains seen in the similarly prepared polystyrene‐polydimethylsiloxane system. The wt % polystyrene (PS) extractible increased with increase in initiator concentration, which is consistent with decrease in the lengths of the PS chains being formed and grafted onto the PIB. Mechanical properties obtained in continuous extension showed maxima in their dependence on composition. Specifically, the ultimate strength (f/A*)m, maximum extensibility εr, energy Er required for rupture, and permanent set ΔL/L0 generally showed maxima in the vicinity of 50 wt % PS. The shortest‐chain PS samples generally showed the largest values of (f/A*)m, εr, and Er, and the smallest values of ΔL/L0.
Sulfonated polyisobutylene telechelic ionomers. XIII. Viscosity behavior in nonpolar solvents and nonpolar–polar solvent mixtures
Authors: Tant Martin R. , Wilkes Garth L. , Kennedy Joseph P. 
Published: April 2003

AbstractThe effect of molecular variables upon the dilute solution viscosity of sulfonated polyisobutylene telechelic ionomers has been studied in both nonpolar solvents and nonpolar–polar solvent mixtures. In nonpolar solvents, association of the terminal salt groups results in an increase in viscosity and gelation at very low concentrations. The concentration at which gelation occurs was found to be dependent upon molecular variables such as architecture, molecular weight, neutralizing cation, extent of neutralization, and the type of solvent. Addition of a small amount of a more polar cosolvent tends to break up ionic associations between polymer chains and thus reduces viscosity. Finally, such solutions with a small amount of polar cosolvent may display dramatic increases in viscosity with increasing temperature due to a dynamic equilibrium between the ionic groups on the polymer chain, the nonpolar solvent, and the polar cosolvent. The results of this work suggest that these ionomers may potentially be useful as viscosity modifiers or “thermal thickeners” in some applications.
Surface morphology and crystalline orientation of uniaxially drawn polytetrafluoroethylene films
Authors: Hashida Shigesou , Namio Hitoshi , Hirakawa Susumu 
Published: April 2003

AbstractFor polytetrafluoroethylene (PTFE) films drawn uniaxially at 100, 150, 250, and 350°C, the morphology and degree of crystalline orientation were investigated by electron scanning microscopy and wide‐angle X‐ray diffraction, respectively. On the surface of the PTFE films which were heat‐treated at 350°C for 2 h before the drawing, granules with a diameter of about 2 μm and bands with a width of about 0.3 μm were observed. By the drawing below the melting point, the bands are transformed into fibrils and a porous structure is formed by the drawing above the draw ratio (λ) of about 1.3. By drawing above the melting point, striations appear perpendicularly to the draw direction, and the collapse of the granules is observed. The orientation of the crystallites increases rapidly with increasing the draw ratio and approaches a plateau at λ ≈ 1.5 for the films drawn above the melting point and at λ ≈ 2.0 for that below it.
Synthesis, characterization, and utilization of methacrylic esters of polyhydric alcohols
Authors: Shantha K. L. , Krishnamurti N. 
Published: April 2003

AbstractDimethacrylic esters of di‐, tri‐, and tetraethylene glycols; trimethacrylic ester of trimethylolpropane and tetramethacrylic ester of pentaerythritol were prepared by a commercially viable process in high yields and purity. These methacrylic esters were systematically characterized by infrared, 1H and 13C nuclear magnetic resonance and mass spectroscopic methods. Anaerobic adhesive compositions were made based on each monomer, and their torque strengths were compared.
Theory of tack of pressure‐sensitive adhesive. II
Authors: Mizumachi Hiroshi , Hatano Yasunori 
Published: April 2003

AbstractWhen a cylinder is pulled on a pressure‐sensitive adhesive, the bonding and debonding processes proceed simultaneously within the surface of contact. In the previous paper, the theory of rolling friction coefficient of pressure‐sensitive adhesives was proposed for the case where bonding occurs instantaneously. The theory is modified in this paper so as to include both the time‐dependent bonding process and debonding process at the same time. Effect of fiber‐forming on rolling friction is also examined. It is ascertained that the modified theory reproduces quite well the experimentally observed features of the curves of rolling friction coefficient against velocity.
Polyethylene adhesion: Pretreatment with potassium permanganate
Authors: Costa Ricardo Aurélio Da , Gonçalves Maria Do Carmo , Oliveira Marcelo Ganzarolli De , Rubira Adley Forti , Galembeck Fernando 
Published: April 2003

AbstractTwo major events occur in the modification of polyethylene (PE) surfaces by treatment with acidic KMnO4 solutions: The polymer surface is coated with a porous MnO2 layer and corroded, by oxidation. In both cases the resulting surfaces may be bonded with epoxy; the average peeling force for LDPE/epoxy/LDPE adhesive joints thus obtained may reach > 1.6 kN m−1 and is limited by adherend cohesive failure. Modified LDPE surfaces and disassembled joints were examined by transmission and ATR‐IR spectrophotometry, to show that corroded, nonwettable LDPE contains appreciable amounts of polar groups, reactive towards epoxy amine components.