bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanisms of antioxidant action: Time‐controlled photoantioxidants for polyethylene based on soluble iron compounds
Authors: Al‐Malaika S. , Marogi A. M. , Scott G. 
Published: April 2003

AbstractThe effects of two component combinations of soluble iron compounds on the rate of photooxidation and associated embrittlement times of low density polyethylene (LDPE) are examined. It is found that photoantioxidants retard the photo prooxidant effects of iron compounds giving controllable induction periods. In the case of the combination of a nickel dithiocarbamate (photoantioxidant) and an iron dithiocarbamate (photo prooxidant) a very wide range of embrittlement times can be obtained in which the induction period is controlled by the nickel complex and the post‐induction period rate by the iron complex.
Thermal degradation of stabilized rigid poly(vinyl chloride) monitored by microhardness measurements
Authors: Gonzalez Ana , Martin‐Gil Jesus , Saja Jose Antionio De , Rodriguez Ramiro 
Published: April 2003

AbstractMicrohardness testing is shown to be a simple and useful complementary technique in the study of thermal degradation of rigid PVC stabilized with different amounts of an organotin compound. An interpretation of the microhardness observation is made in terms of reactions between the polymer and the stabilizer.
Removal of polyethylene glycol mono‐p‐nonylphenyl ether and dodecylbenzenesulfonate by chloromethylated polystyrene–polyethylenepolyamines and –polyethyleneimines
Authors: Tashiro Tatsuo 
Published: April 2003

AbstractThe reactions of chloromethylated divinylbenzene crosslinked polystyrene (CMPS) with polyethylenepolyamines (PEPA), polyethyleneimines (PEI), 2‐methyl‐2‐oxazoline (MeOZO), and the hydrolysis of CMPS–MeOZO reaction products were carried out. The abilities of these products for removing a nonionic surfactant, polyethylene glycol mono‐p‐nonylphenyl ether (NP, n=10), solutes in water were investigated. Removal rates of NP by and the amounts of NP removed by CMPS–PEPA, –PEI, –MeOZO, and hydrolyzate of CMPS–MeOZO were compared. The adaptability of removal behavior of the products to the Freundlich's adsorption isotherm and the amounts of NP removed by unit masses of the products were investigated. The products also removed an anionic surfactant, sodium dodecylbenzene sulfonate (DBS), solutes in water. The mechanisms for removing NP and DBS were discussed.
On loci of acrylonitrile polymerization with bisulfite‐persulfate initiators under the conditions of low water/monomer ratio
Authors: Ito Seiichi , Plant Otake 
Published: April 2003

AbstractIn the preparation of acrylonitrile–vinylacetate copolymer (93:7 in weight) by continuous polymerization in aqueous medium using the complete mixing type reactor, the author and co‐workers studied the effects of the water/monomer ratio on polymer properties and polymerization. They reported that the structure of a polymer particle becomes more compact with decreasing water/monomer ratio. This was noted in studying the physical properties of the polymer and the formation of polymer particles in this system. 1,2 Here the author has performed kinetic studies based on the results of polymerization to determine the loci of the polymerization in the range of water/monomer ratio roughly from 1.75 to 4.0. Most of the primary radicals from the initiators attack the monomers in the aqueous phase to form monomer radicals attached to initiator fragments, and most of the monomer radicals grow to form polymer radicals until termination occurs in the aqueous phase. Hence, the loci of polymerization in this system are not the surfaces and inner parts of the polymer particles, the diameters of which are roughly from 20 to 60 μm observed by a microscope, but the aqueous phase excluding these particles.
Morphology of composite polymer emulsion particles consisting of two kinds of polymers between which ionic bonding intermolecular interaction operates
Authors: Okubo Masayoshi , Yamaguchi Seitaro , Matsumoto Tsunetaka 
Published: April 2003

AbstractThe morphology of particles (I) produced by seeded emulsion copolymerization of styrene (S) and sodium p‐styrene sulfonate (NaSS) with butyl acrylate (BA)‐methacryloyloxyethyl‐trimethylammonium chloride (QDM) copolymer particles as seed was examined in comparison with poly(butyl acrylate) (PBA)‐polystyrene (PS) composite polymer emulsion particles (II). In an electron microscopic observation, it was observed that II particles had an anomalous shape and the electron densities at different points in the particle were heterogeneous, whereas I particles had an almost spherical shape and the electron densities were homogeneous. The maximum tensile strength and toughnes were much larger in II than I. The dynamic mechanical studies indicate that II film had a macroheterogeneous structure consisting of PS‐rich and PBA‐rich phases, whereas I film had a microheterogeneous structure. These ressults suggest that there is an effect of intermolecular interaction between polymers of different kinds on the formation of heterogeneous structure in particles consisting of two kinds of polymers.
N‐phenyl piprazine‐polyester derivative as curing activator of unsaturated resins
Authors: Tanzi M. C. , Pornaro F. , Miuccio A. , Grassi L. , Danusso F. 
Published: April 2003

AbstractAn oligomeric compound (Pol‐2A) has been synthesized by a Michael‐type addition of N‐phenyl piperazine to double bonds of the maleic units of a polyester resin. This compound was used as activator (with benzoyl peroxide) in the curing of unsaturated polyester resins and compared in its efficiency with N,N‐dimethylaniline (DMA). Pol‐2A showed actiator characteristics comparable to those of DMA, with a wider range of gel times, and similar mechanical properties of the end products, with the advantage of a severe lowering of diffusibility and related environmental toxicity.
A dielectric study of the glass transition region in urethane elastomers modified by ionic bonds
Authors: Zieliński R. , Rutkowska M. 
Published: April 2003

AbstractThe uretane elastomers cross‐linked by the varying content of triethanolamine and 3‐bromine‐1,2‐propanediol have been investigated by means of dielectric spectroscopy. The complex character of the glass‐rubber transition has been determined. It results from different mechanisms of cross‐linking (urethane and ionic bonds). The influence of content of cross‐linking mixture on the microphase separation has been observed.
Cure kinetics of neat versus reinforced epoxies
Authors: Mijović Jovan 
Published: April 2003

AbstractAn investigation was carried out into the cure kinetics of neat vs reinforced epoxy systems. The formulations were composed of tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM) epoxy resin and diaminodiphenyl sulfone (DDS). Glass was used as reinforcement. A series of isothermal differential scanning calorimetry (DSC) thermograms were run and analyzed by the proposed autocatalytic kinetic model. An increase in reaction rate was observed at higher temperature and higher DDS concentration in both neat and reinforced formulations. The presence of reinforcement had an effect on the cure kinetics. The observed effect, however, was not very pronounced. Slightly lower values of the reaction rate constant and longer times needed to reach the maximum reaction rate were recorded in reinforced systems. After reaching the peak value, the rate of reaction dropped off faster in reinforced formulations, resulting in lower average value of Hult, the ultimate heat of reaction. It was suggested that the reinforcement imposes restrictions on the molecular mobility of reactive species.
Time lag in diffusion
Authors: Ash Richard , Barrie James A. 
Published: April 2003

AbstractAdsorption and desorption diffusion time lags are given for some homogeneous hollow cylinder and spherical shell membrane systems. The treatment relates to a constant diffusion coefficient with solution or sorption obeying Henry's law. Time lags for both “forward” and “reverse” flow have been determined and identities between them derived. For the hollow cylinder and spherical shell membrane systems considered here, there are only three distinguishable time lags.
Thermal cis‐trans isomerization and photofading of some azo dyes in poly(ethylene terephthalate) matrices: A kinetic study
Authors: Dubini‐Paglia Ernestina , Beltrame Pier Luigi , Marcandalli Bruno , Carniti Paolo , Seves Alberto , Vicini Loredana 
Published: April 2003

AbstractThe thermal cis‐trans isomerization of azo dyes XC6H4N=NC6H4N(C2H5)2 (where X is H, OCH3, CN, and NO2) in poly(ethylene terephthalate) matrices, below the glass transition temperature, and in dibutylphthalate solutions has been studied kinetically in the temperature range 20–60°C. Kinetic behavior in the polymer is characterized by two or three simultaneous first‐order processes with similar activation enthalpies. These processes reflect an unequal distribution of “tie‐molecules,” “folds,” and “cilia” in the amorphous region of the polymer. Lightfastness of the dyes in poly(ethylene terephthalate) films has been investigated. Polymer morphology strongly affected the photofading, but no significant influence was observed in the kinetic experiments.
Lignosulfonate polymerization: Effect of cross‐linking agents
Authors: Bialski A. M. , Bradford H. , Lewis N. G. , Luthe C. E. 
Published: April 2003

AbstractFactors affecting the thermosetting properties of spray‐ or freeze‐dried, ammonium‐based spent sulfite liquor, a material rich in lignosulfonates, were investigated. It was found that purified lignosulfonates did not thermoset readily, unless either monomeric wood sugars or formaldehyde were present. Under the conditions employed, the monosaccharides were more effective than formaldehyde as thermoset accelerators. This may be due to the greater functionality of the intermediate decomposition products of the carbohydrates, which would create more reactive sites for intermolecular bonding with lignin. In contrast to previous findings, it was found that lignosulfonates (of mol wt ≥ 10,000) underwent polymerization, and subsequent thermosetting, more rapidly than their lower molecular weight counterparts. This was established by HPLC size exclusion elution chromatography of each sample following thermal treatment. It was also observed that wood did not affect the rate of thermosetting.
Effect of modified calcium phosphate surface on the aqueous polymerization of methyl methacrylate
Authors: Moustafa A. B. , Abd El‐Hakim A. A. , Badran A. S. , Abd El‐Ghaffar M. A. , Sakr M. A. I. E. 
Published: April 2003

AbstractThe aqueous polymerization of methyl methacrylate was carried out in the absence and in the presence of unmodified and modified calcium phosphate surface with adsorbed stearic acid from stearic acid benzene solution; this was found to accelerate the polymerization process. The acceleration was found to depend on the extent of modification. The apparent activation energy was also found to decrease with surface modification. It was also found that the calcium phosphate surface modified with stearic acid has an effect on the sedimentation rate and sediment volume in organic medium.
Copolymerization kinetics for 2‐isopropenyl‐2‐oxazoline (methods and results)
Authors: Dibona D. M. , Fibiger R. F. , Gurnee E. F. , Shuetz J. E. 
Published: April 2003

AbstractThe reactivity ratios for 2‐isopropenyl‐2‐oxazoline (IPO), a dual functional monomer, have been determined using a combination of gas chromatography, with an internal standard, and a new form of the integrated copolymerization equation. The results indicate a parallel trend with the reactivity ratios of styrene in spite of the large disparity in polarity between IPO and styrene.
Estimation of the inherent friction factor per main‐chain friction unit of liquid low‐molecular‐weight unsaturated polyesters
Authors: Kaštánek Alois , Balcr Miroslav , Bohdanecký Miloslav , Lešek František , Kitzler Jaroslav 
Published: April 2003

AbstractThe temperature dependence (at 323–443 K) of the zero‐shear viscosity η of about 30 nonfractionated samples of an unsaturated polyester (300 < Mn < 1500) was analyzed and the parameters of the Vogel equation describing the η(T) dependence were estimated. Their dependence on the molecular weight is discussed. The inherent friction factor per main‐chain friction unit, ξo, has been evaluated for 15 < Zn < 70 (where Zn is the number‐average number of main‐chain friction units) and compared with the values available for other polymers.
Thermal degradation of butadiene–styrene‐based rubber
Authors: Abu‐Zeid M. E. , Youssef Y. A. , Abdul‐Rasoul F. A. 
Published: April 2003

AbstractThermal degradation of some commerically available rubber based on butadiene–styrene copolymers are studies as a function of composition, temperature, and heating periods using photoacoustic spectroscopy (PAS) technique. It was found that random copolymers are more degradable than block copolymers and that the latter is more degradable than alternate copolymers. Mechanistic schemes leading to the thermal degradation of these synthetic rubbers are given together with a qualitative explanation of the relation between their composition and their thermal stabilites.
Molecular weight distribution of the graft copolymer comprising mixtures of styrene and acrylamiae on cellulose acetate film by means of gel permeation chromatography
Authors: Bhattacharyya S. N. , Maldas D. 
Published: April 2003

AbstractStyrene portion of the radiation‐induced graft copolymer comprising styrene and acrylamide was separated by acid hydrolysis and the effects of various grafting parameters (e.g., reaction time, reaction temperature, solvents, monomer composition, etc.) on molecular weight distribution were evaluated by means of gel permeation chromatography. When a single monomer or mixture of two monomers are grafted, the molecular weights is found to increase, but polymer dispersity decreases with the increase of reaction time or reaction temperature except at a higher reaction time due to the continuous enlargment of the growing chain through increased swelling and molecular motion of the trapped radicals. At higher reaction time the degradation of the graft chains lead to lower molecular weight and higher polymer dispersity. Effects of solvents (e.g., methanol, ethanol, and t‐butanol) on the molecular weight and molecular weight distribution were discussed on the basis of swelling property and chain transfer constants of the solvents. Styrene‐type graft radical being long lived compared to acrylamide type, gave long‐chain styrene graft with the increase of styrene content in the reaction mixture. A comparison of the effect of one‐and two‐component systems on a molecular weight distribution is also discussed.
Polymers from renewable sources. III. Hydroxy‐terminated myrcene polymers
Authors: Cawse J. L. , Stanford J. L. , Still R. H. 
Published: April 2003

AbstractA range of hydroxy‐terminated polymyrcenes has been prepared using hydrogen peroxide initiated polymerization of pyroysate grade, β‐myrcene in n‐butanol solution at 100°C. An oligomeric fraction, containing a large proportion of dimeric material formed via the Diels–Alder reaction, always accompanies the major polymeric fraction. Procedures are described for the removal of this oligomeric material. Polyols so prepared and purified had number average molecular weights (Mn) between 4000 and 2000 g mol−1 at low and high initiator concentrations, respectively, with corresponding number average functionalities (fn) between 1.3 and 2.3 and polydispersities (Mw/Mn) of ∼1.3. The microstructure of the polyols was investigated using NMR spectroscopy from which the main mode of propagation during polymerization of myrcene was deduced to be 1,4 addition across the conjugated double bonds. Glass transition temperatures of the polymyrcenes measured by differential scanning calorimetry were in the range −50–60°C.
Grafting of 2‐hydroxyethyl methacrylate and methyl methacrylate onto chrome tanned collagen fibers
Authors: Klásek A. , Kaszonyiová A. , Pavelka F. 
Published: April 2003

AbstractGrafting of 2‐hydroxyethyl methacrylate and methyl methacrylate onto chrome tanned collagen fibers, initiated by the bisulfite/pesulfate redox system, has been investigated. Using the method of statistical planning of experiments, regression equations have been obtained describing the effects of the monomers concentration and the composition of the initiating system on the monomers conversion, degree of grafting and on physical properties of grafted collagen. The relationship between the polyacrylate content in the composites prepared and their swelling ability, water absorption capacity, and the tensile strength is discussed.
Miscible blends of poly(styrene‐co‐acrylonitrile) and poly(α‐methyl styrene‐co‐acrylonitrile) with poly(methyl methacrylate) containing sterically hindered amine group
Authors: Goh S. H. , Lee S. Y. , Siow K. S. 
Published: April 2003

AbstractPoly(methyl methacrylate) containing a small amount of pendant 2,2,6,6‐tetramethylpiperidinyl group was found to be miscible with poly(styrene‐co‐acrylonitrile) and with poly(α‐methyl styrene‐co‐acrylonitrile). The poly(α‐methyl styrene‐co‐acrylonitrile) blends exhibited lower critical solution temperatures. Phase separation of the poly(styrene‐co‐acrylonitrile) blends could not be induced by heating up to 270°C.
Morphological, structural, and interfacial changes produced in composites on the basis of polypropylene and surface‐treated sepiolite with organic acids I. Surface treatment and characterization of the sepiolites
Authors: Acosta J. L. , Ojeda M. C. , Morales E. , Linares A. 
Published: April 2003

AbstractThis research was conducted in order to gain a better knowledge of the possibilities deriving from sepiolite as a polypropylene filler. Special stress has been laid on the study of morphological, structural, and interfacial changes produced by the simple incorporation of sepiolite in the polymeric matrix, as well as on the effects of these changes on all the properties of the resulting composites. In the light of the relevance of filler surface activity with regard to the physical behavior of these materials, we modified this activity through chemical reaction of the superfacial silanol groups in the sepiolite with different aliphatic organic acids. This paper includes a description of the esterfication procedures and a characterization of the different sepiolites obtained.
Structure and properties of talc‐filled polyethylene and nylon 6 films
Authors: Murthy N. S. , Kotliar A. M. , Sibilia J. P. , Sacks W. 
Published: April 2003

AbstractWater vapor transmission rates can be reduced by as much as 50% in polyethylene by using talc as a filler. The oxygen permeability as well as water vapor transmission rates are similarly reduced by talc in nylon 6 films. The films show low elongation at break and reduced breaking strenth in the presence of talc. The yield strength and the modulus increase with the amount of talc, whereas the elongation at yield decreases. The mechanical and the barrier properties change with the size of the filler, the smaller size being more favorable. Talc probably acts as a nucleating agent and increases the crystallinity in polyethylene and nylon. Polyethylene unit cells in talc‐filled films are oriented with the (110) planes parallel to the (001) planes of talc. Nylon 6 crystals, which are in the α form in the presence of talc, are oriented with the hydrogen bonded sheets, the (002) planes, parallel to the (001) planes of talc. In both polyethylene and nylon 6, talc is oriented with the c‐axis normal to the plane of the film, i.e., with the broad faces of talc flakes in the plane of the film. Lattice matching between the polymer and talc suggests epitaxy to be a contributing factor for the observed orientation of polyethylene and nylon 6 crystals.
Orientation suppression in fibers spun from polymer melt blends
Authors: Brody H. 
Published: April 2003

AbstractThe addition of very small amounts of carefully selected polymers by melt blending has been found to radically change the flow properties at spinning of conventional polymers such as polyethylene terephthalate, nylon 66, and polypropylene. This has a large effect on spun properties, especially at high wind‐up speeds. The additive polymers used have included liquid crystal polymers, polyethlene, polyethylene glycol, and nylon 66. A major phenomen is a considerable lowering of spun orientation, or wind‐up speed suppression. In order to activate the non‐liquid crystal polymers to achieve this effect special spinning conditions are necessary. The mechanism is viewed as being nonuniform extensional flow in a two‐phase system and not molecular interaction.
Effect of mode of agent removal on pore structure of liquid ammonia treated cotton cellulose
Authors: Bertoniere N. R. , King Walter D. , Rowland Stanley P. 
Published: April 2003

AbstractThe pore structures of three liquid‐ammonia‐treated cottons were compared via a reverse gel permeation chromatographic technique. Cotton battings were treated with liquid ammonia which was removed by volatilization at ambient temperature or at elevated temperature and by water exchange. Three series of water‐soluble solutes were used to study the elution characteristics of whole fiber columns prepared from these battings. The solutes were oligomeric sugars, ethylene glycols, and glymes (ethylene glycol dimethyl ethers) having molecular dimensions in the range of conventional finishing agents for cotton. All three liquid ammonia treatments increased the internal pore volumes accessible to small molecules. The greatest increase was noted when the ammonia was removed by water exchange and the least when volatilization at elevated temperature was employed. Ambient temperature volatilization had an intermediate effect. Decreases in the volumes of large pores were effected by ammonia treatments followed by volatilization at ambient or elevated temperature. Water exchange of the ammonia resulted in an increase in the volume of large pores as well as of the small pores.
Wood processing variables and adhesive joint performance
Authors: Ebewele Robert O. , River Bryan H. , Koutsky James A. 
Published: April 2003

AbstractIn order to obtain a bonded wood product from the tree, wood must be subjected to a series of processes. These include, among others, vital processes like drying of the green wood and machining of the surfaces of the dried wood in preparation for bonding. However, when wood is machined with dull blades, thermal degradation of the wood frequently occurs. The effects of kiln drying and thermal degradation of wood on the performance of the adhesive joints subsequently formed from such wood were investigated. Tapered double cantilever beam (TDCB) test specimens obtained from hard maple and phenol–resorcinol–formaldehyde (PRF) adhesives were used in the investigations. The enhancement of fracture energy due to the reduction in the moisture content of wood, the improved performance of adhesive joints due to rejointing of wood surfaces before bonding, and the reduction of adhesive joint strength resulting from thermal degradation of wood are presented and discussed.