bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methyl ketone‐photosensitized polymerization of N‐methylolacrylamide with cotton
Authors: Reinhardt Robert M. , Arthur Jett C. , Hinojosa Oscar 
Published: April 2003

AbstractPhotoinitiated, free‐radical reactions of cotton cellulose with N‐methylolacrylamide (NMA) from aqueous solution through direct excitation of cellulose are reported. Also reactions initiated by energy transfer from excited methyl ketone compounds to cellulose are reported. Dimethyl ketone, dimethyl ketoneformaldehyde, dimethyl diketone, dimethyl diketoneformaldehyde, methyl ethyl ketoneformaldehyde, and methyl phenyl ketoneformaldehyde were used in the sensitized reactions. When methyl ketone products were in solution during photoirradiation, they acted as sensitizers to increase the rate and extent of the reaction of NMA with cotton cellulose. When products that contained formaldehyde were covalently reacted with cotton before photoirradiation, the rate and extent of the reaction of NMA with cellulose were generally decreased. These effects can be at least partially explained by intramolecular energy transfer, as determined by chemiluminescence, electron spin resonance, and excitation fluorescence measurements. When methyl phenyl ketoneformaldehyde was covalently linked to cellulose before photoirradiation, energy localization that initiated free‐radical polymerization of NMA was minimized. When cellulose that was padded with a monomer solution was dried before photoirradiation, the extent of the reaction of NMA with cellulose was decreased.
Photoinitiated polymerization of N‐methylolacrylamide with crosslinked cotton cellulose
Authors: Reinhardt Robert M. , Arthur Jett C. , Muller Linda L. 
Published: April 2003

AbstractThe effects of crosslinking both unswollen and swollen cotton cellulose on the photoinitiated reactions of N‐methylolacrylamide (NMA) with cotton are reported. Formaldehyde and dimethylolethyleneurea were used as crosslinking agents. Crosslinked cellulose had a decreased efficiency of photoconversion of NMA to poly(N‐methylolacrylamide) (pNMA) with cotton. If the cellulose was crosslinked in the swollen state, increased dosages of ultraviolet radiation gave complete conversion of NMA to pNMA with cotton. Cotton that was crosslinked in the unswollen state probably restricted movement of the aqueous solution of NMA within the fiber and fabric structures and decreased chain propagation within the structures. This restriction resulted in decreased photoconversion of NMA to pNMA with cotton. Transmission and scanning electron microscopy of cotton cellulose that was crosslinked in the swollen state and of cotton cellulose that was crosslinked in the unswollen state showed that swollen cotton was less compacted than unswollen cotton.
Irradiation of poly(vinyl chloride) with H2 plasma. II
Authors: Zahran A. H. , Nofal E. , El‐Azmirly M. A. , Elsabee M. Z. 
Published: April 2003

AbstractPoly(vinyl chloride) films blended with plasticizers, stabilizers, and fillers are irradiated with a beam of H2 plasma. The polymer partially loses its solubility in cyclohexanone. The viscosity of the soluble part decreases in the initial stages and then increases on further irradiation. Crosslinking was followed by dehydrochlorination and discoloration of the polymer. The electrical conductivity was measured as a function of the irradiation dose and time. The plasticizers enhanced the action of plasma while the stabilizers and fillers reduced it.
Emulsion copolymers of alpha‐methylstyrene and styrene
Authors: Rudin Alfred , Samanta M. C. 
Published: April 2003

AbstractThis article reports molecular weights and mechanical and processing properties of a series of styrene/alpha‐methylstyrene copolymers produced by emulsion polymerization at various temperatures. Molecular weights were measured by solution viscosity, membrane osmometry, light scattering, and gel‐permeation chromatography. Molecular weight development is controlled by chain transfer to monomer, but the molecular weight distributions are broader than would be expected for such reactions. This is attributed to polymer branching resulting from chain‐transfer events. Molecular weight distributions of copolymers were multimodal. Thermal stability of the copolymers is somewhat lower than that of polystyrene, but addition of conventional antioxidants produces compositions with good stability in thermoplastic processing operations. Copolymers containing 25 wt. % of alpha‐methylstyrene have usage temperatures about 12°C higher than that of polystyrene.
Surface tension measurements on film‐forming polymers: Thermal aging effects
Authors: Schreiber H. P. , Marineau Y. 
Published: April 2003

AbstractThe surface property changes caused by exposure to specific time/temperature regimes have been followed by critical surface tension data (γc) in a series of styrene–acrylic polymers frequently used as film‐formers. A simple, experimental method for γc evaluation, previously described proved useful for present purposes. Surface tensions change more rapidly when polymers age above their characteristic Tg. In the polymers studied, increases in γc indicate an apparent enrichment in the acrylic content of the surface, the rates apparently dominated by diffusion‐controlled processes. The importance of the effect increases with overall acrylic content in the polymer and with molecular weight.
Effect of washing on the photo‐oxidation resistance of stabilized polypropylene fibers
Authors: Lustoň J. , Maňásek Z. , Samuhelová Z. 
Published: April 2003

AbstractThe effect of aqueous detergent and benzine washing on the photo‐oxidation stability of stabilized polypropylene fibers was studied. The fibers were stabilized by higher molecular weight light stabilizers based on 2‐hydroxybenzophenones and by thermo‐oxidative stabilizers. The content of the light stabilizers in washed fibers was determined, and photo‐oxidation curves of the original and washed fibers were measured. The effectiveness of stabilization of the original and the washed fibers was compared with that of 2‐hydroxy‐4‐n‐octyloxybenzophenone at identical content of 2‐hydroxybenzophenone structural units. Another criterion was comparison of washed and unwashed fibers. Photo‐oxidation curves of accelerated aging and induction periods showed that washing with either aqueous detergent or benzine decreases the resistance of fibers to photo‐oxidation, i.e., washing lowers the content of stabilizers in fibers. Extraction with benzine exerts a more pronounced effect than washing with water. Extractability by benzine of higher molecular weight stabilizers is considerably lower than with low molecular weight stabilizer. On the basis of experimental results it is assumed that washing of fibers leads to leaching not only of thermo‐oxidative stabilizers but also to a decrease in the content of light stabilizers. Derivatives alkylated by tert‐butyl are more extractable by benzine, while the nonalkylated derivatives are more extractable by washing with water.
Benzoates as deterrents for small arms propellants
Authors: Brodman B. W. , Schwartz S. , Devine M. P. 
Published: April 2003

AbstractThe depth of penetration of a homologous series of benzoic acid esters into a spherical nitrocellulose matrix was studied. It was found that the depth of penetration was related to the shift in infrared hydroxyl stretching frequency when the individual esters were incorporated into cast films of nitrocellulose. Further, these findings are discussed in terms of Taft's σ* values for the individual esters. Conclusions regarding the use of benzoic acid esters as deterrents for small arms propellants were made.
Crystalline/crystalline polymer blends: Some structure–property relationships
Authors: Siegmann A. 
Published: April 2003

AbstractMechanical properties, morphology, and compatibility of polybutene‐1 blended with polypropylene, both crystallizable polymers, are described in the present study. Blends of various compositions were studied using tensile tests, differential scanning calorimetry, wide‐angle x‐ray diffractometry, and optical microscopy. A discussion on the state of compatibility and structure–property relationships for such blends in presented.
Polyester–polycarbonate blends. VI. Branched aliphatic polyesters
Authors: Cruz C. A. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractPolycarbonate blends with poly(pivalolactone) were found to be completely immiscible based on the glass transitional behavior observed by thermal analysis. Crystallinity of the poly(pivalolactone) was unaffected by blending with polycarbonate. The heat of mixing of low molecular weight analogs of this system, ethyl pivalate and diphenyl carbonate, were found to be endothermic, in contrast to exothermic mixing observed for similar linear esters. Methyl branching adjacent to the ester carbonyl is believed to shield the specific interaction of this unit with the aromatic carbonate structure which leads to exothermic mixing and miscibility of similar unbranched esters with polycarbonate. Blends of poly(2,2‐dimethyl‐1,3‐propylene succinate) were found to be partially miscible with polycarbonate because the shielding is not so great since the methyl groups are further removed from the ester group.
Comparison of the instantaneous and conversion chemical heterogeneity of random copolymers
Authors: Stejskal Jaroslav , Kratochvíl Pavel 
Published: April 2003

AbstractThe calculation of a general distribution function of chemical composition of random copolymers involving the instantaneous and conversion chemical heterogeneity is demonstrated. Typical examples offer a semiquantitative view about the effect of the two types of chemical heterogeneity on the shape and width of the distribution of chemical composition.
Relationship between modulus and density for high‐density closed‐cell thermoplastic foams
Authors: Iremonger M. J. , Lawler J. P. 
Published: April 2003

AbstractIt is necessary to establish a relationship between Young's modulus and density for a closed‐cell plastic foam in order to predict the flexural stiffness properties of integral skinned foamed thermoplastics. It has been shown experimentally that there exists a square‐power relationship between modulus and density for high‐density closed‐cell thermoplastic foams, but this has not been confirmed by existing theoretical models for foams. These models are reviewed and finite element analyses of “circular hole in square plate” and “spherical hole in solid cube” models are presented which give close agreement with the empirical results.
Condensation polymerizations in ideal continuous‐flow‐stirred tank reactors of monomers violating the equal reactivity hypothesis
Authors: Gupta Santosh K. , Kumar Anil , Saraf R. 
Published: April 2003

AbstractMolecular weight distributions, moments and the polydispersity indices were computed for AB‐type condensation polymerization in an ideal continuous‐flow‐stirred tank reactor for monomers not following the equal reactivity hypothesis. The model considers the rate of reaction between monomer and monomer to be R times that characterizing the reaction between any other species in the reaction mass. It is found that the polydispersity indices in these reactors are substantially larger than values obtained in batch reactors. Also, the molecular weight distribution splits into two curves—one for odd‐order homologs and the other for even‐order ones for R >1. For R < 1, substantial amounts of unreacted monomer are present in the exit stream, and curve splitting does not occur.
Graft copolymerzation of poly(vinyl chloride) with styrene. I. Synthesis and characterization
Authors: Sharma K. K. , Varma J. K. 
Published: April 2003

AbstractGraft copolymerization of poly(vinyl chloride) (PVC) partially dehydrochlorinated by heating in nitrobenzene was investigated using styrene as monomer and anhydrous AlCl3 as cationic initiator in the temperature range of 0–35°C. Effect of monomer, catalyst, and PVC concentration on % graft‐on was also evaluated. Introduction of labile sites in PVC by partial dehydrochlorination in nitrobenzene resulted in an increase in % graft‐on. Intrinsic viscosity of PVC–g–polystyrene in THF initially increased with an increase in % graft‐on. At higher % graft‐on a decrease in [η] was observed.
Grafting vinyl monomers onto silk fibers. VIII. Graft copolymerization of methyl methacrylate onto silk using tetravalent manganese–oxalic acid redox system
Authors: Panda Gadadhar , Pati Nrusingha C. , Nayak Padma L. 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate onto silk fibers was investigated in aqueous solution using the Mn(IV)–oxalic acid redox system. The copolymerization reaction was carried out under a variety of conditions such as different monomer, initiator, oxalic acid, acid concentrations, and temperatures. The graft yield increases with increasing initiator concentration up to 5 × 10−2M, and with further increase of the initiator concentration it decreases. The graft yield also increases with increasing sulfuric acid concentration up to 15 × 10−2M, and decreases thereafter. The rate of grafting also increases with increase in oxalic acid concentration up to 1.5 × 10−2M and 84.592 × 10−2M, respectively, and thereafter the rate of grafting shows down. The effect of temperature, solvents, and salts on graft yield has also been investigated and a plausible rate expression has been derived.
Investigation of phase behavior and water binding in poly(alkylene oxide) solutions
Authors: Hager S. L. , Macrury T. B. 
Published: April 2003

AbstractThe aqueous solution properties of alkylene oxide polymers and copolymers are related to their interaction with water. In an attempt to better understand this behavior, differential scanning calorimetry has been employed to measure phase changes and water binding in solutions of polyethylene glycol (PEG), polypropylene glycol (PPG), and a 50/50 random copolymer of ethylene oxide and propylene oxide. PEG (Mn = 3510) forms a crystalline eutectic with water at 0.48 weight fraction of polymer. The liquidus curve for water can be fit accurately using the Flory–Huggins expression for solute activity with an interaction parameter of 0.05. PPG and the random copolymer do not crystallize and thus do not form a crystalline eutectic. Based on decreases in the heat of fusion of free water with added polymer, PEG binds more water than the copolymer which binds more water than PPG. The estimated hydration numbers per polymer segment are 1.5 for PPG, 2.3 for the copolymer, and 2.7 for PEG.
Microbial and oxidative effects in degradation of polyethene
Authors: Albertsson A.‐C. , Bánhidi Z. G. 
Published: April 2003

AbstractBiodegradative conversion of 14C present in high‐density (linear) polyethene (HDPE) film to respiratory 14CO2 during a two‐year aerated cultivation with soil or with Fusarium redolens dropped from 0.36% by weight to less than 0.16% by weight when the HDPE film was deprived from most of its low molecular components by extraction with cyclohexane. Decrease of 14CO2 production after extraction could be observed in different abiotic aging cultures. This is direct evidence for a primary utilization of the short‐chain oligomeric fraction of the main crystalline materials. The extractable oligomeric fraction of HDPE was analyzed by gel permeation chromatography (GPC), and Mn 1049, 1088, and 1297 were found in untreated, aged, and biodegraded materials, respectively, indicating that microbes can oxidize somewhat longer polyolefin chains than aboitic forces do during aging. The limited degradation of HDPE confined to extractable material is comparable to the degradation of straight‐chain n‐alkanes and presumably proceeds according to similar mechanism. Such material (n‐alkanes) can exit in the interstitial spaces between the crystalline lamellae as fringed micelles which infiltrate these cavities as amorphous clusters but are also produced to some extent during aging and weathering. Protection of HDPE by antioxidant (a sterically hindered phenol) resulted in an inhibition of microbiological catabolism of 14C to 14CO2. Aging was also suppressed in this way, indicating that although remnants of the supported CrCO3 polymerization catalyst are responsible for a slight but cumulative abiotic oxidation of the unprotected polymer, this effect will be counteracted too by the antioxidative additive. As biological degradation is superimposed on the chemistry of aging, a mutual synergism between the two effects is feasible.
Physicochemical processes occurring during the formation of cellulose diacetate membranes. Research of criteria for optimizing membrane performance. V. Cellulose diacetate–acetone–water–inorganic salt casting solutions
Authors: Lemoyne C. , Friedrich C. , Halary J. L. , Noël C. , Monnerie L. 
Published: April 2003

AbstractConsideration was given to the effects of casting conditions upon the performance and structure of membranes prepared from CA–acetone–water–inorganic salt solutions. Treating casting solutions as polymer–solvent–nonsolvent ternary systems, the data on equilibrium phase separation conditions were plotted in a triangular diagram for solutions containing Al(NO3)3, KSCN, Mg(ClO4)2 or no additive. Measurements of casting solution viscosity, membrane thickness, freezing and nonfreezing water contents were used to supplement flux and retention data of membranes made by varying the inorganic salt and holding time in a systematic way. With the aid of scanning and transmission electron microscopy, it was concluded that membranes may consist of one, two, three, or four layers. The data and correlations obtained allow us to propose a mechanism of formation for each of these layers.
Fibrillar size in native cellulose
Authors: Boylston E. K. , Hebert J. J. 
Published: April 2003

AbstractFibrillar size of native cellulose was studied in detail by electron microscopic and x‐ray techniques. Samples included natural fibers of cotton and ramie as well as algal and bacterial celluloses. Results indicated smaller sizes for cotton and ramie than was previously reported in the literature and a possible difference in fibrillar sizes among celluloses.
Effect of copolyether‐ester additives on the melt rheology of polyoxymethylene
Authors: Gale David M. 
Published: April 2003

AbstractSmall amounts of low‐molecular‐weight copolyether‐ester additives were shown to augment shear thinning in polyoxymethylene melts. Non‐Newtonian flow increased with the decreasing molecular weight of the additive. Mechanistic implications are discussed.
Thioetherglycidyl resins. I. Products of condensation of 1‐mercaptomethylnaphthalene and 1,4‐, 1,5‐di‐(mercaptomethyl) naphthalene and their mixtures with epichlorohydrin
Authors: Charmas Władyslaw , Podkościelny Wawrzyniec 
Published: April 2003

AbstractNew thioetherglycidyl resins produced by condensation of 1‐mercaptomethylnaphthalene, 1,4‐di(mercaptomethyl)naphthalene, 1,5‐di(mercaptomethyl)naphthalene, and their mixture of 1,4‐ and 1,5‐di(mercaptomethyl)naphthalene with epichlorohydrin were obtained. The condensation was carried out in two ways. In the first way, potassium salt of mercaptans and epichlorohydrin were used. In the second, epichlorohydrin was added to mercaptans and then the obtained chlorohydrin thioether was dehydrohalogenated by the alkaline hydroxide in water and n‐butanol or isopropyl alcohol solution. The method of heterogeneous condensation of dithiol with epichlorohydrin in water and isopropyl alcohol solution proved to be the most effective. Yield, the epoxide content, and the total chlorine content for all resins were found. The structure of thioetherglycidyl resins with the highest epoxide content was determined by elementary analysis, and infrared (IR) and NMR spectra. Thermal stability of resins was studied during long controlled heating at unchanged temperature and short heating carrying the thermal gravimetric analysis (TGA) mainly in air. As follows from the studies, thioetherglycidyl resins can be cured both chemically and thermally.
Grafting vinyl monomers onto silk fibers. X. Graft copolymerization of methyl methacrylate onto silk using hydrogen peroxide–thiourea redox system
Authors: Panda Gadadhar , Pati Nrusingha C. , Nayak Padma L. 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate onto silk fibers initiated by a hydrogen peroxide–thiourea redox system was investigated under various conditions. The effects of monomer, initiator, temperature, acidity of the medium, and solvent on the rate of grafting were studied. The graft yield increases with the increase of monomer and initiator concentration. The graft yield also increases with the increase of acid concentration upto 22.50 × 10−2M and thereafter it decreases. The effect of some inorganic salts on the rate of grafting has also been investigated, and a suitable mechanism has been suggested.
Laminar dispersion of polymer solutions in helical coils
Authors: Singh Diwakar , Nigam K. D. P. 
Published: April 2003

AbstractIn the present study the step response experiments were carried out with power law fluids in two helical coils to examine the suitability of axial dispersed plug flow model in describing the laminar dispersion of non‐Newtonian fluids in helical coils. The ranges of variables covered are 10 ≤ λ ≤ 100,0.01 ≤ NRegen ≤ 2.5,0.001 ≤ NDe ≤ 0.77 and 0.035 ≤ τ ≤ 1.33. It is found that coiling results in reduced dispersion to that in a straight tube.
Water‐soluble copolymers. I. Synthesis of model dextran‐g‐polyacrylamides by Fe(II)/H2O2 initiation and characterization by aqueous size exclusion chromatography
Authors: McCormick Charles L. , Park Lee Soon 
Published: April 2003

AbstractModel graft copolymers were synthesized by grafting acrylamide onto dextran (M̄w = 500,000) utilizing the Fe(II)/H2O2 initiation system. Aqueous size exclusion chromatography (SEC) was used to determine the effects of changing reaction parameters on hydrodynamic dimensions of the resulting graft copolymers. It was also possible to optimize reaction conditions yielding the highest viscosity graft copolymer with the least amount of homopolyacrylamide and unreacted substrate. The molecular structures of the graft copolymers were determined by elemental analysis, SEC, and solution viscometry. Selective hydrolysis of the dextran backbone allowed determination of average molecular weight of acrylamide grafts, number of grafting sites, and average molecular weight of the graft copolymers. Rheological studies indicated viscosity and pseudoplastic behavior were largely related to the graft length of the polyacrylamide side chains.
The effects of orientation and crystallinity on the solvent‐induced crystallization of poly(ethylene terephthalate). I. Sorption‐ and diffusion‐related phenomena
Authors: Jameel Hasan , Waldman Joshua , Rebenfeld Ludwig 
Published: April 2003

AbstractThis series of reports summarizes the results of an experimental research program designed to establish the effects of preexisting orientation and crystallinity on solvent‐induced crystallization of poly(ethylene terephthalate) films. Dimethylformamide was used as a model for a strongly interacting solvent. Special emphasis has been given to the kinetics of crystallization and diffusion, the morphological and structural modifications, and the accompanying changes in physical properties. This article deals with solvent sorption and desorption. Solvent diffusion and the extent of crystallization decreased with increasing orientation and crystallinity in the starting films, with crystallinity being more important. Despite the semicrystalline morphology, the overall diffusion behavior was found to be Fickian, allowing the calculation of pseudodiffusion coefficients which were dependent on both the draw ratio and the treatment temperature. Solvent treatments at elevated temperatures involved a dual input of thermal and chemical energy, which caused the films to behave differently above and below the glass transition temperature. Solvent desorption and reversible swelling were also found to be dependent on preexisting structure and treatment conditions.