bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mark–Houwink equation and GPC calibration for linear short‐chain branched polyolefines, including polypropylene and ethylene–propylene copolymers
Authors: Scholte Th. G. , Meijerink N. L. J. , Schoffeleers H. M. , Brands A. M. G. 
Published: April 2003

AbstractThe reduction in molecular dimensions due to the presence of short side chains in otherwise linear polyolefins can very simply by calculated by assuming that the configuration of the main chain is not influenced by the side chains. This enables us to express the intrinsic viscosity–molar mass relationship as a function of the mass fraction of side chains (S): [η] = (1 − S)α+1KPEMνα and, with use of the universal calibration principle, to convert the GPC calibration for purely linear polymers samples into the calibration for short‐chain branched polymers: M* = (1 − S)M. Experimental data from literature on short‐chain branched poly‐ethylenes, and our own data on ethylene–propylene copolymers are used to verify the above assumption. It appears that the experimentally found relations between [η], Mw and M*w (GPC) within the usual accuracy justify this approach.
Transport and related properties of paint films. II. Dynamic mechanical properties and humidity effects
Authors: Wedgewood Alan R. , Seferis James C. , Beck Theodore R. 
Published: April 2003

AbstractA systematic four‐stage investigation of eight unpigmented coating formulations, including three vinyl, two polyurethanes, and three epoxy systems was done to provide baseline structural information upon which an improved understanding and an optimization of protective coatings can be founded. First, the results from dynamic mechanical measurements are provided and discussed for the base polymer component in each coating system. Second, the effects of humidity on the dynamic mechanical properties of these base polymers were determined at room temperature. The extent of property degradation was monitored by calculating the Tg depression with increased humidity, assuming a temperature–humidity superposition. The extent of degradation, as monitored by the Tg, was found to correlate directly with the level of hydrogen bonding in these coatings. Third, the influence of typical coating additives (a TCP plasticizer and a rosin hardener) on the properties of two of the vinyl coating systems was investigated. In the final stage, the synergistic effects of absorbed moisture and these additives on the coatings properties were investigated at room temperature. Increases in the concentration of these additives was found to magnify the degradation effect of increased humidity. This magnified degradation has been assigned to increased water absorption with increases in the concentration of either of these additives.
Mechanisms of antioxidant action: C–nitroso compounds as UV stabilizers for polypropylene
Authors: Chakroborty K. B. , Scott G. , Yaghmour H. 
Published: April 2003

AbstractIt is shown that nitroso‐tert‐alkanes are highly active UV stabilizers which become at least partially chemically attached to polypropylene during processing. The aromatic nitroso compounds are less effective as light stabilizers but are more effective than their alkyl analogues as thermal oxidative stabilizers. Mechanisms are proposed to account for the antioxidant activity of the nitroso compounds and their ability to cause crosslinking of the polymer during processing.
Kinetics of transesterification of dimethylene terephthalate with ethylene glycol
Authors: Datye Keshav V. , Raje Hemant M. 
Published: April 2003

AbstractThere is a disagreement about the order of reaction of transesterification of DMT with EG. The reactivity of the two ester groups is not compared yet. The transesterification of DMT and MHET is studied to establish the kinetics of the process. Attempts are made to treat the kinetic data on a mathematical model for third‐order reaction.
Investigation of amino acid composition in the crystalline region of silk fibroin
Authors: Nadiger G. S. , Bhat N. V. , Padhye M. R. 
Published: April 2003

AbstractAccurate estimation of amino acids composition has been carried out for hydrolysates of four varieties of Indian silks, viz., Mulberry, Tasar, Eri, and Muga. These studies have revealed that the hydrolysate (hydrofibroin or crystalline region) in the case of Mulberry consists of glycine, alanine, and serine, whereas in the case of Tasar, Eri, and Muga, it is found to be mainly alanine. Other amino acids were also found to be present in the hydrolysate of these silks. But, the quantities present in each case were found to be negligible when compared to those amino acids cited above. Furthermore, these results are in conformity with the structure elucidation made by infrared spectral studies and x‐ray diffraction.
Effect of degree of crosslinking on water transport in polymer microparticles
Authors: Robert Christian C. R. , Buri Pierre A. , Peppas Nikolaos A. 
Published: April 2003

AbstractThe water transport in microparticles of poly(2‐hydroxyethyl methacrylate) crosslinked with small amounts of ethylene glycol dimethacrylate was investigated as a function of time. Dynamic swelling curves were obtained and analyzed with a simple, empirical, exponential expression, where the exponent n indicates the mechanism of water transport. It was determined that the mechanism changed from Fickian to non‐Fickian transport as the nominal crosslinking ratio increased from X = 0.007 to X = 0.124 mol EGDMA/mol HEMA. Smaller particles attained their equilibrium swelling value faster. The velocity of the penetrant front was determined with optical microscopy, and it was found to decrease from 22.2 to 11.2 μm/min as the crosslinking ratio increased.
Double exposure stabilization of positive photoresist
Authors: Yanazawa Hiroshi , Hasegawa Norio , Douta Kikuo , Hashimoto Norikazu 
Published: April 2003

AbstractPositive photoresists appeared to be the most promising material in VLSI microfabrication for ten or more years from now. Thus, processing know‐how needs to be accumulated continuously. This work deals with thermal characteristics of positive photoresist. The following facts were declared experimentally. The quinone diazide, photosensitizer, was thermally decomposed at around 140°C to release N2. Simultaneously the surface layer of resist film was changed into innert state, called as ‘husk’, with low gas permeability and high chemical resistance. These thermal changes in resist film affect the photoresist to SiO2 adhesion. In this work a noble process, named double exposure stabilization, is developed to get sufficient chemical resistance and good adhesion simultaneously.
Stabilization of nigeria natural (havea) rubber with bound antioxidant added as masterbatch
Authors: Kolawole E. G. , Ebi Godwin 
Published: April 2003

AbstractNigeria natural rubber concentrates in a newly synthesized antioxidant were added as conventional additives for normal natural rubber. The natural weathering, thermal and photooxidative protective performance of the adduct were examined by measurement of the carbonyl index and induction periods. From the results obtained, it is concluded that the addition of this new antioxidant in the form of masterbatch appears to be a better practical way of incorporating it into natural rubber simply by dilution of natural rubber. The bound stabilizers were found to be resistant to leaching.
Synthesis of statistical networks from liquid polybutadiene. V. Synthesis and adhesive properties of 1,2‐polybutadiene networks
Authors: Friedmann G. , Brossas J. , Widmaier J. M. 
Published: April 2003

AbstractA series of 1,2‐polybutadiene networks was prepared either by endlinking reaction of telechelic liquid precursors or/and by crosslinking with disilyl compounds. Transparent materials were obtained and used as adhesives in glass assembly mainly. The shear resistance at break was found to be higher compared to conventional vulcanized elastomers.
The viscoelastic properties of rubber–resin blends. II. The effect of resin molecular weight
Authors: Class J. B. , Chu S. G. 
Published: April 2003

AbstractIn blends of rubber and low molecular weight resins, the compatibility of the system controls the viscoelastic properties and ultimately the performance of the composition as a pressure sensitive adhesive. The effect of the resin molecular weight on compatibility was examined by studying rubber–resin blends prepared from resins which represent a range of molecular weights. Viscoelastic properties were measured using a mechanical spectrometer on 1:1 blends of rubber and a series of polystyrene resins and poly(vinylcyclohexane) resins. Based on plots of G′ and tan δ vs. temperature, blends of natural rubber and polystyrene resin show incompatibility at resin Mw of about 600 and above. Blends of natural rubber and poly(vinyl cyclohexane) are incompatible at resin Mw of about 1800, but are compatible at Mw of about 650. Blends of styrene–butadiene rubber and polystyrene resins are compatible at resin Mw of about 650 but appear to contain a low volume incompatible phase at Mw of about 900. Therefore, the compatibility of a rubber–resin blend depends upon the molecular weight of the resin. Even systems expected to be compatible will show evidence of incompatibility as the molecular weight of the resin is raised above some limiting value.
Solvent permeation in plasma‐fluorinated polyethylene
Authors: Corbin G. A. , Cohen R. E. , Baddour R. F. 
Published: April 2003

AbstractLiquid‐phase sorption data are reported for the toluene–polyethylene system. The effects of fluorine plasma and inert‐gas plasma treatments of the polymer surface were investigated. The presence of a fluorinated surface layer reduces initial solvent permeation rates, but the enhanced barrier property is lost when irreversible morphological changes occur during polymer swelling. A combination of chemical and morphological factors appears to be responsible for the observed temporary reduction in permeability; crosslinking of surface macromolecules was not a significant factor for the particular cases investigated in this work.
Carbon‐13 NMR characterization of DGEBPA epoxy resins
Authors: Fleming William W. 
Published: April 2003

AbstractCarbon‐13 nuclear magnetic resonance (NMR) has been used to investigate the structure and character of diglycidyl ether of bisphenol A (DGEBPA) epoxy resins more thoroughly than previously reported in the literature. It is shown that spectra, when run under quantitative conditions, can detect the loss of epoxides at the end groups by reactions such as hydrolysis. The products of acid hydrolysis of a DGEBPA resin are observed and assigned. It is further shown that the possibility of epoxide hydrolysis and impurities or structural irregularities can lead to inaccuracies in epoxy equivalent weight (EEW) calculations using a previously reported methodolgy. A new method is employed which can take into account loss of end group epoxides. Part of this new method consists of a measure of the epoxide to end group ratio (EER) which sheds light on the final possible quality of the cured resin. The EER value is shown to be in many ways more informative than the EEW measure which has the built‐in assumption that there is an epoxide group for each end group.
Pulsed NMR study on the silica‐filled rubber systems
Authors: Ito Masayoshi , Nakamura Takehusa , Tanaka Koji 
Published: April 2003

AbstractProton spin–spin relaxation time has been measured by the pulsed NMR technique for the bound rubbers extracted from both silica‐filled polyisoprene and polybutadiene composites. Two relaxation times T2t (short) and T2l (long) are observed for all samples. They are ascribed, respectively, to the relaxation of the tightly and loosely bound rubber components. When the silica filled polybutadiene composite is heat treated at 120°C, loosely bound rubber is preferentially formed, which leads to the increase in the total bound rubber fraction in the composite. During the heat treatment of silica‐filled polyisoprene composite, a part of the loosely bound rubber phase is transformed into tightly one, and simultaneously the chain mobilities of both phases become more constrained state. These changes are accompanied by the degradation of polyisoprene molecules probably due to the strong chemical interaction of silanol group and rubber molecules. At a prolonged heat treatment, the fraction of total bound rubber in the composite decreases as a result of the degradation of the loosely bound rubber molecules.
An investigation of the kinematics of stretch blow molding poly(ethylene terephthalate) bottles
Authors: Cakmak Mukerrem , White James L. , Spruiell Joseph E. 
Published: April 2003

AbstractAn experimental study of the kinematics of inflation of poly(ethylene terephthalate) (PET) parisons in a Corpoplast stretch blow molding process is reported. LVDT displacement transducers have been placed at various positions along the length and at the top of a specially designed and built mold. A six‐channel LVDT demodular circuit was built and attached to a minicomputer. Studies were conducted at 90 and 100°C at various pressures. Kinematic models were developed for the parison inflation, and stress fields along the deforming surface of the parison were computed using membrane theory.
Engineering plastics from lignin. VII. Structure property relationships of poly(butadiene glycol)‐containing polyurethane networks
Authors: Saraf Vasudev P. , Glasser Wolfgang G. , Wilkes Garth L. 
Published: April 2003

AbstractHydroxypropyl lignin‐based thermosetting polyurethanes containing polybutadiene (PBD) glycol soft segments (Mn of 2800 g M−1) were synthesized with excess hexamethylene diisocyanate (HDI) and tolylene diisocyanate (TDI) by solution casting. Miscibility of the glycol with the lignin derivative was found to be poor as expected, and phase separation between the two polyol components in polyurethanes was detected by thermal and mechanical analysis, and by electron microscopy. This study examines the effect of concentration of polybutadiene glycol on the thermal and mechanical properties of the polyurethanes. The two‐phase network system displayed significantly different properties than either the poly(ethylene glycol)‐containing polyurethanes or their soft segment‐free counterparts described previously. Macrophase separation was observed at nearly all degrees of mixing and was found to affect thermal and mechanical properties. The glass transition temperature (Tg) of the lignin phase in the TDI‐based networks increased with poly(butadiene glycol) content rising from 3.6 to 71.4% of polyurethane, and this was attributed to the employment of a constant diisocyanate weight fraction which gave rise to a variable NCO/OH ratio and crosslink density. Distinct phase separation was evidenced by scanning electron microscopy (SEM) at above 3.6 and 7.1% glycol content for HDI‐ and TDI‐based films, respectively. The polyurethane films behaved like rubber‐toughened lignin networks when PBD was the discrete phase, and like lignin‐reinforced rubber when the lignin derivative was discrete. This behavior was evidenced by the Young's modulus decreasing from 2000 to 50 MPa and ultimate strain rising from 6 to greater than 150%, with soft segment content increasing from 0 to 71.4%.
Gas and vapor sorption in polymers just below Tg
Authors: Chiou J. S. , Maeda Y. , Paul D. R. 
Published: April 2003

AbstractGenerally, sorption isotherms for gases like CO2 in glassy polymers are concave to the pressure axis, whereas in the rubbery state these isotherms are linear for gases or sometimes convex to the pressure axis for more condensable vapors. Examples of CO2 isotherms are reported here that show at low pressure the curvature characteristic of glasses and then become linear at higher pressures. This is observed when the glass transition temperature Tg is not much greater than the observation temperature T, and plasticization of the polymer by sorbed CO2 causes Tg to become equal to T within the range of pressures employed in the isotherm measurement. For the sorption of vapors in glassy polymers, this can lead to sigmoidal isotherms, as discussed using an illustration from the literature.
Compatibilizing effect of a diblock copolymer of isotactic polystyrene and isotactic polypropylene in blends of the corresponding homopolymers
Authors: Giudice L. Del , Cohen R. E. , Attalla G. , Bertinotti F. 
Published: April 2003

AbstractA high molecular weight polymer mixture was obtained from a sequential Ziegler–Natta polymerization of styrene and propylene. After removing unwanted homopolymers from the reaction product, the remaining copolymer was subjected to extensive molecular and morphological characterization. The results of these experiments indicate that the purified material is a diblock copolymer of isotactic polystyrene and isotactic polypropylene, with each block having a molecular weight in the range of 225,000 g/mol. This block copolymer was incorporated in varying amounts into blends of isotactic polystyrene and isotactic polypropylene homopolymers. At low concentrations of copolymer (<20 wt %), the diblock functions as a dispersing agent, significantly reducing the size of domains in the heterogeneous blends. At higher copolymer concentrations, a dramatic improvement in the adhesion across the domain boundaries is also observed. The favorable effects of the copolymer on mechanical properties are demonstrated in the results of tensile impact experiments.
Effect of heat treatment on nylon‐6 tire cords
Authors: Mukherjee A. K. , Gupta B. D. , Kulkarni S. G. , Chauhan D. S. , Chakravarty S. N. 
Published: April 2003

AbstractThe behavior of nylon‐6 tire cords at elevated temperature has been evaluated. The heat treatment of cords at 200°C for 16 h was found to reduce their tensile properties considerably. This has been attributed to the decrease in average molecular weight and change in molecular weight distribution as ascertained by fractionation studies. Heat setting of cords in the temperature range of 180–210°C without any applied tension showed some decrease in tensile properties. This has been ascribed to the higher degree of shrinkage of the cords and hence increased chain folding in the molecular structure. However, irrespective of time and temperature of heat treatment, shrinkage was reduced with increasing tension on the cord. Effect of heat setting on density and crystallinity was also evaluated.
Dissolution rates of poly(methyl methacrylate) films in mixed solvents
Authors: Cooper Wendy J. , Krasicky Philip D. , Rodriguez Ferdinand 
Published: April 2003

AbstractA laser interferometer has been used to measure in situ the dissolution rates of thin films of poly(methyl methacrylate) (PMMA). The most significant finding is that addition of small amounts of a low‐molecular weight nonsolvent can increase the rate obtained with a higher molecular weight solvent. In this study, silicon wafers were coated with polymer (about 1 μm thick) and annealed at 155°C for 1 h. The dissolution rates were measured at 17.5, 22.5, and 27.5°C. All the mixtures contained methyl ethyl ketone (MEK) (2‐butanone), as the major component. The minor component was water, methanol, ethanol, 1‐propanol, 2‐propanol, or ethylene glycol. Water and methanol showed the greatest effects. Both were able to increase the dissolution rate as much as two‐fold. All the mixtures exhibit the same activation energy (25 kcal/mol) despite their wide differences in dissolution rate.
Grafting of cellulose–thiocarbamate with vinyl monomers: Antimicrobial activity
Authors: Nagieb Zenat A. , El‐Gammal Amira A. 
Published: April 2003

AbstractGrafting of vinyl monomers onto cellulose‐thiocarbamate was carried out using ceric ammonium sulfate (CAS) as an initiator. The graft yield was found to depend on the amount of thiocarbamate groups, initiator, and monomer concentrations as well as temperature. The graft yield increased with increasing (CAS) concentration. The reactivity of vinyl monomers studied followed the order ethyl acrylate>acrylonitrile. A comparison between the graft yields obtained with the modified cullulose indicated that cellulose thiocarbamates having less than 1.1% nitrogen showed lower graft yields than the unmodified cellulose. Above this, cellulose thiocarbamate was much more amenable to grafting than the unmodified cellulose. The grafted cellulose thiocarbamates exhibited high antifungal activity and had no effect on gram‐negative, gram‐positive bacteria and yeast. The maximum zone of inhibition was obtained after grafting with 2 h which resulted in 43 and 50% add‐on polymer in the cases of acrylonitrile and ethyl acrylate, respectively. Grafted cellulose thiocarbamates with acrylonitrile had higher potency for antifungal activity than that grafted with ethyl acrylate.
Effects of die temperature on extrudate swell in screw extrusion
Authors: Henderson A. M. , Rudin Alfred 
Published: April 2003

AbstractExtrusion of a hot polymer melt through a cooler die zone substantially increases the extrudate swell of some thermoplastics. This effect was examined for commercial samples of low‐density polyethylene, polypropylene, and polystyrene. Two conflicting effects come into play during extrusion of a thermoplastic. Colder melt temperatures promote increased extrudate swell, but the same conditions also facilitate molecular disentanglement and reduced melt elasticity and die swell. Since the extrusion process itself may affect the relation between die swell and melt temperature, laboratory‐scale measurements for the design of processes like blow molding are better carried out with small‐scale screw extruders than with capillary rheometers. For some applications it may be advantageous to use a polymer whose die swell is particularly responsive or unresponsive to die temperature variations. The procedure described in this article can be used effectively to monitor this characteristic.
Membrane potentials and permeation of NaCl in poly(vinyl alcohol‐co‐itaconic acid) membranes
Authors: Higuchi Akon , Iijima Toshiro 
Published: April 2003

AbstractThe membrane potential and permeability of NaCl were measured for six crosslinked poly(vinyl alcohol‐co‐itaconic acid) membranes having various water contents [0.25≤H≤0.83 H2O (g)/swollen membrane (g)] and interpreted by means of an equation derived from Schlögl′s theory. Both results of the membrane potential and the permeability of the membranes having H≥0.34 could be satisfactorily interpreted by the theory. The permeability of NaCl in the membrane of H=0.25 gave, however, an increasing tendency with the decrease of the upstream concentration lower than 0.04 mol/L. It was considered that the concentration dependence reverse to what was caused by the Donnan exclusion might be due to the concentration dependence of the thermodynamic partition coefficient in nonfreezing water of the membrane. By the equation thus derived the membrane potential and the permeability of NaCl in the membrane of H=0.25 were expained qualitatively. The mobility ratios of Na+ and Cl− and the effective charge density in the membranes were discussed.
Dielectric properties and stress–strain measurements of chloroprene rubber based on different carbon black fillers
Authors: Lawandy S. N. , Abd‐El‐Nour K. N. 
Published: April 2003

AbstractA systematic dielectric study of 1 kHz was carried out on chloroprene rubber, mixed with different types of carbon black and different concentrations. The measurements were carried out at room temperature (25°C). It was found that better dielectric properties cannot be achieved when the carbon black concentration exceeds 60% for MT, 40% for SRF, and 20% for both HAF and SAF. In addition, the relation between the dielectric constant ε and the modulus of elasticity E for the different mixes were studied. From this study it was found that, up to certain carbon black volume concentration (depending on the filler type), the modulus equation Ef = E0 (1 + 0.67φC + 1.62φ2) can be used to relate the dielectric properties εf and εo of carbon black filled and unfilled rubber compounds. The dielectric measurements were also related to the particle size and the structure of carbon black.