bluuebunny/crossref_metadata_2025 huggingface dataset:
Low‐pressure reverse osmosis desalination with improved cellulose acetate membranes
Authors: Ghosh Ajit K. , Sirkar Kamalesh K.
Published: April 2003

The advantages of carrying out reverse osmosis desalination with improved membranes at low pressures have been pointed out. Cellulose acetate (CA) semipermeable membranes developed with low air‐exposure periods by Sirkar et al. from novel Manjikian‐type casting solutions having high CA content, partial replacement of acetone by dioxane, and small amounts of ZnCl2 (or none) have been tested for the following combinations of operating pressure (lb/in.2)/feed brine concentration (in ppm): 250/5000; 300/7500; 400/10,000; 600/30,000; 700/40,000; 750/50,000; 800/60,000. In the pressure range of 250‐600 lb/in.2 (psig), the pure water permeability (PWP) constants of membranes for a given salt transport parameter are greater than those of similar membranes tested earlier by Sirkar et al. at 600 psig with a 5000‐ppm brine feed. The PWP constants decrease faster with pressure as the casting solution CA concentration is reduced from 32% to 30% and the dioxane content of the solvent is raised from 40% to 60%. The intrinsic performances of membranes from a 32% CA casting solution with 40% dioxane improve as the pressure is increased from 250 to 600 psig. The solution structure‐rate of evaporation concept along with the phenomenon of fingerlike cavities and protrusions in membranes from high dioxane casting solutions explain most of the observations of this work. The superior low‐pressure performance of these CA membranes provide a basis for systematically lowering the operating pressure in reverse osmosis desalination.
1‐chlorobutadiene–butadiene rubber. IV. Increasing the hydroxyl group content in the rubber
Authors: Yamashita Shinzo , Sando Katsumi , Kohjiya Shinzo
Published: April 2003

The hydroxyl group content in 1‐chlorobutadiene–butadiene rubber (CB–BR) was increased by the following two methods: (1) heating of the CB–BR latex to hydrolyze the unstable chlorine in CB–BR and (2) introduction of hydroxyl by the Menschutkin‐type reaction between 2‐dimethylaminoethanol (DMAE) and the chlorine in CB–BR. By heating the latex at 70°C for 12 hr, 55% chlorine was hydrolyzed to result in a marked increase in hydroxyl group content in CB–BR, i.e., at least 55% chlorine is situated in the CB units of the 1,4‐configuration. Heat‐treated CB–BR was found to contain a small amount of conjugated triene structure by UV spectroscopy, which indicates that elimination of some unstable chlorine as hydrogen chloride occurs during latex heating. By reaction with DMAE, 44% chlorine was converted into hydroxyl in toluene at 27°C. CB–BR compounded with DMAE does not suffer from gelation by milling on an open roll. Thus, by these methods, high molecular weight butadiene rubber having various concentrations of hydroxyl groups is obtained.
High‐strength, high‐modulus fibers from hydrazide polymers and copolymers
Authors: Dobinson Frank , Pelezo C. A. , Black W. B. , Lea K. R. , Saunders J. H.
Published: April 2003

A polyhydrazide was prepared from terephthaldihydrazide (TDH) and terephthaloyl chloride (TCl) and copolyhydrazides from oxalicdihydrazide (ODH) and from TCl with a 50:50 molar mixture of ODH and TDH. The 50:50 copolymer gave superior spinning performance and fiber properties and was studied extensively as a candidate for tire cords. The best yarn tensile properties were 21.6 gpd (grams/denier) tenacity, 6% elongation, and 443 gpd modulus. Temperature resistance and creep resistance were good, while the resistance to uv light was only fair. Stability in rubber and adhesion to rubber were good. In radial tires built with equal‐strength belts, mileage from tires having the copolymer cord in the belts was equal to that of steel‐belted tires.
Adhesives from divalent metal salts of mono(hydroxyethyl)phthalate, anhydrides, and bisepoxides
Authors: Matsuda Hideaki
Published: April 2003

Systems of divalent metal salts of mono(ydroxyethyl)phthalate‐anhydride‐bisepoxide were evaluated as adhesives. The bisepoxides, bisphenol A diglycidyl ether (BADG) and hexahydrophthalic acid diglycidyl ester and the anhydrides, maleic anhydride and hexahydrophthalic anhydride (HPA) were used. The adhesive properties of the above metal‐containing systems were generally superior to those of the systems not containing metal, due to the polarity effect of metal carboxylate groups. The effect of introducing metal (ionic links) on tensile shear and peel strenghths clearly appeared, especially in the metal salt‐HPA‐BADG systems.
Diffusion of hydrocarbons in rubber, measured by the pulsed gradient NMR method
Authors: Von Meerwall E. , Ferguson R. D.
Published: April 2003

The pulsed field gradient spin echo method was used to measure the diffusion of ten paraffin hydrocarbons in several uncrosslinked rubbers at 51°C. We obtain various free volume parameters from the concentration dependences, establish the approximate proportionality of the translational friction coefficient to paraffin molecular weight, and confirm the equal intrinsic efficiency of the diffusion mechanism of decane and hexadecane in rubbers.
Graft copolymerization of styrene onto poly(p‐nitrophenyl acrylate) by chain transfer reaction
Authors: Nakamura Shigeo , Kasatani Hideo , Matsuzaki Kei
Published: April 2003

Styrene (St) was polymerized in the presence of poly(p‐nitrophenyl acrylate) (PNPA) with azobisisobutyronitrile as an initiator to prepare graft copolymers through the chain transfer reaction of growing polystyrene (PSt) radicals to the aromatic nitro groups on PNPA. The maximum number of branches attained was 16.4 (Pn of PNPA was 1780), which corresponds to 108 monomer units per PSt branch. This is far less than the value of 43, previously obtained for poly(vinyl p‐nitrobenzoate) as a trunk polymer. Therefore, several model compounds for trunk polymers were prepared, and the chain transfer constants of PSt radicals to these model compounds were determined. As a result of the Hammett plot, it is concluded that higher electron attracting property of the substituents increases the reactivity of nitro groups to the growing PSt radicals, resulting in more highly branched graft copolymers.
Water and solute transport across cellulose acetate membranes in the treatment of soybean whey by reverse osmosis
Authors: Baker E. C. , Mustakas G. C. , Moosemiller M. D. , Bagley E. B.
Published: April 2003

In processing full‐fat soy flour to produce an acid‐precipitated lipid protein concentrate, there results a by‐product whey fraction which, because of its high biological oxygen demand, represents a serious disposal problem. Processing of food waste streams by reverse osmosis has received considerable attention because of its low theoretical energy requirement, since no phase change is involved. A series of statistically designed and analyzed experiments were conducted on a pilot‐plant reverse osmosis unit to study the effect of the operating parameters on solute and solvent transport in cellulose acetate membranes. Sucrose and sodium chloride solutions were tested in addition to soybean whey to relate the mixed solute system in whey to that of single‐solute organic and inorganic feed solutions. Water flux was shown to have an Arrhenius dependency on temperature, and some membrane compaction was observed with the more porous membrane. Concentration polarization for sucrose and sodium chloride solutions increased linearly with water flux. Solute flux for soybean whey solutions decreased with molarity and was independent of pressure, whereas solute rejection increased with temperature and pressure and was independent of molarity. Good agreement was obtained using the derived parameters A, B, and τ for soy whey in the diffusion transport model when compared to the observed experimental values.
Silicone‐toughened poly(styrene‐co‐acrylonitrile)
Authors: Saam John C. , Mettler Claudia M. , Falender James R. , Dill Timothy J.
Published: April 2003

Uniform dispersions of high‐molecular‐weight poly(dimethylsiloxane) (PDMS) in a matrix of poly(styrene‐co‐acrylonitrile) (SAN) are prepared where the degree of crosslinking in the elastomer and its extent of grafting to the SAN matrix are controlled. This gives an impact resistant plastic at ambient and low temperatures which is resistant to outdoor exposure. The Tg of PDMS is shown to be greatly reduced when grafted to the SAN matrix. Plots of impact resistance versus shift factor aT of the elastomer added for toughening coincide for PDMS and polybutadiene over a 150°C temperature range.
Photocrosslinkable unsaturated polyesters
Authors: Sadafule D. S. , Panda S. P.
Published: April 2003

Nine photocrosslinkable unsaturated polyesters containing pendent chalconyl and cinnamylidenemalonyl moieties have been synthesized by a route involving no water elimination. The resins are insolubilized by visible and UV irradiation. They can also be cured with styrene, MEK peroxide, and cobalt naphthenate. A study of the photoreactions reveals that the resins containing 4′‐chalconyl groups crosslink and isomerize simultaneously, whereas those containing 4‐chalconyl groups undergo crosslinking only, due to the steric suppression of isomerization. Photoinsolubility is also achieved by introducing the cinnamylidenemalonyl group into the resin structure. It is found that the resins containing both the chalconyl and cinnamylidenemalonyl groups in the repeat units do not exhibit any pronounced photofastness.
Classification of properties of elastomers using the “optimum property concept.” I. Introduction
Authors: Lautenschlaeger F. K. , Myhre M.
Published: April 2003

An attempt is made to distinguish properties of elastomers by types. “Basic properties of materials” or “network properties” in elastomers are properties which either increase or decrease from the liquid to the solid state of materials or over the range of the “elastomeric plateau” of elastomers. From these are distinguished properties that exhibit characteristic maxima and are therefore “maximum properties” or bivalued properties. Mechanical failure properties show the characteristics of “maximum properties.” The maxima in “maximum properties” generally do not coincide. This noncoincidence of the maxima with a change in a “basic property of a material” has major theoretical and practical implications, for example, it is the cause of the crossovers in the relative performance rating of materials under different test conditions. The implications of this noncoincidence of the failure property maxima on the relevance of correlations between these properties are discussed. A change in the testing conditions is reflected in a shift of the optimum value in a “basic property of a material” with respect to a specific “maximum property.” Data and certain conclusions in the literature are interpreted on the basis of this concept. Examples of the limitations of the validity of mathematical relationships are presented. Also, a definition of the term “state of cure” is proposed and a suggestion for the rating of severities of test equipment and applications of elastomeric materials recommended. The effect of increased degrees of crosslinking for a series of polymers and crosslinking agents is assessed. It is suggested that the “mechanisms” of failure properties will remain elusive if their rationalization is attempted on the basis of other failure properties, e.g., the mechanism of abrasion on that of tear strength or cut growth. The main purpose of this proposal is to provide support for a drastic reduction in laboratory testing by identifying those properties which can lead to different relative ratings in routine evaluations and actual applications. A more empirical approach to materials evaluations is recommended based on the calibration of laboratory instrumentation with respect to specific applications. A de‐emphasis of routine evaluations of materials on the basis of their “maximum properties” seems to be justified.
Measurement of the absolute molecular weight and molecular weight distribution of polyolefins using low‐angle laser light scattering
Authors: MacRury T. B. , McConnell M. L.
Published: April 2003

By connecting a low‐angle laser light scattering photometer (LALLSP) on line with a high‐temperature gel permeation chromatograph (GPC), molecular weight distributions were determined for three polyethylene standards (two high density and one low density) without resorting to column calibration procedures. In addition, the absolute weight‐average molecular weight and second virial coefficients of four polyethylene standards (three high density and one low density) were obtained using low‐angle laser light scattering. The molecular weights measured were in excellent agreement with those specified by the National Bureau of Standards. For the low density material, a microgel fraction was detected by the on‐line LALLSP but not by the conventional GPC detector. This resulted in a z‐average molecular weight of over 3 × 106 daltons, an order of magnitude greater than that determined by conventional GPC techniques.
Preferential wetting phenomenon in bicomponent polymer melt flow
Authors: Southern John H. , Ballman Richard L.
Published: April 2003

For two polymer melts spun in a side‐by‐side configuration through a capillary, interface shape and spinneret exit angle data are presented as a function of viscosity ratio, spinneret dimensions, and relative polymer‐steel wettability. Nylon‐nylon versus nylon‐polyurethane bicomponent flow systems are compared. A surface tension phenomenon is postulated to be significant in controlling the bicomponent fiber interface shape for capillary length‐to‐diameter ratios of the order of unity.
Kinetics of the emulsion polymerization of vinyl acetate
Authors: Zollars R. L.
Published: April 2003

Recent investigations of the emulsion polymerization of vinyl acetate report a variable behavior. The reaction has been reported to exhibit a half‐order rate dependence and no particle number dependence on the initiator level, or a first‐order dependence for both the reaction rate and particle number on the initiator concentration, or some behavior between these two extremes. While two recent models have attempted to account for the changes in the reaction rate dependence by postulating either an aqueous phase or a polymer phase termination, no adequate explanation of the particle number behavior has been given, nor has a single model been suggested that agrees with all of the experimental data. This investigation confirms the results of previous investigators and develops an empirical model for the particle number, taking into account the effects of the initiator level, emulsifier level and alkyl chain length, temperature, and ionic strength on the particle number. This particle number model, used with a polymer phase termination reaction model, yields a polymerization rate expression which agrees with all previous data.
DRY‐RO membranes from cellulose acetate carbamates
Authors: Kesting R. E. , Ditter J. F. , Jackson K. F. , Murray A. S. , Newman J. M.
Published: April 2003

Cellulose acetate carbamates (CACs) are the polymers which result when organic isocyanates are reacted with the free hydroxyl groups of cellulose acetate (CA). CACs are more hydrolytically stable and exhibit physical properties which are superior to those of their CA mixed ester analogs. Two synthetic approaches to CACs have been utilized in this study: (1) preformation, i.e., separate synthesis of such polymers prior to their inclusion in solutions for membrane casting; and (2) in situ formation, i.e., the inclusion of blocked isocyanates in standard dry process casting solutions of CA followed by thermal activation of the resultant dry membranes leading to regeneration of free isocyanate and subsequent CAC formation. Preformed CAC polymers have been prepared utilizing phenyl‐, 3‐chloropropyl‐, 3‐bromopropyl‐, and 3‐bromopropyl‐(isothio)‐, isocyanates. Polymers containing omega‐halocarbamate moieties were quaternized with dimethylbenzylamine to produce ionogenic (QCAC) polymers containing quaternary ammonium groups. DRY‐RO membranes from the QCACs exhibit flux/rejection values varying between 6–8 gfd at 98% rejection and 20 gfd at 90% rejection (0.5% NaCl feed at 400 psi and 25°C). In situ formation of CAC membranes has been effected with tolylene‐ and hexamethylene‐diisocyantes, with quaternized isocyanate monomers employed for the preformed CAC polymers, and with specially tailored diisocyanates containing ionogenic groups. Crosslinking rendered all of the membranes acetone insoluble. Inasmuch as in situ formation substitutes the easy synthesis of blocked isocyanate monomers for the more difficult separate synthesis of preformed CAC polymers, it is anticipated that the former will replace the latter.
Analysis of amino resins by carbon/nitrogen analyzer. I. Mole ratios of components
Authors: Rybicky J. , Kambanis S. M.
Published: April 2003

Techniques for the determination of the formaldehyde to urea and the formaldehyde to melamine ratios by means of an elemental carbon‐nitrogen analyzer are described. Etherified resins require additionally an NMR spectrum of the analyzed sample. Mathematical equations are presented which relate the experimentally determined carbon and nitrogen contents to the compositional characteristics of amino resins. For etherified resins, the ratio of alkoxy groups to the total formaldehyde is also determined. The techniques are assessed by analyzing model samples and by the propagation‐of‐error treatment of the equations. It is shown that the F/U and F/M ratios can be determined with a good accuracy whether or not the resin is etherified.
Grafting onto wool. VI. Effect of amines in ceric ion‐initiated grafting of poly(vinyl acetate)
Authors: Misra B. N. , Kaur Inderjeet , Dogra Ramesh
Published: April 2003

Poly(vinyl acetate) has been graft copolymerized onto Himachali wool in the presence of ceric ammonium nitrate alone and in presence of amines in aqueous medium under a wide variety of reaction conditions. Nitric acid was found to catalyze the graft copolymerization. Maximum grafting under optimum conditions has been determined. Several grafting experiments were carried out in presence of triethylamine and triethanolamine. Both amines were found to reduce the extent of grafting. The decrease in the percent grafting in presence of amines has been explained in terms of a chain‐transfer mechanism.
Methyl ketone‐photosensitized polymerization of N‐methylolacrylamide with cotton
Authors: Reinhardt Robert M. , Arthur Jett C. , Hinojosa Oscar
Published: April 2003

Photoinitiated, 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

The 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

Poly(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

This 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

The 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

The 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

The 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

Mechanical 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

Polycarbonate 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

The 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

It 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

Molecular 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

Graft 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

The 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

The 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

Biodegradative 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

Consideration 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

Fibrillar 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

Small 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

New 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

The 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

In 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

Model 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

This 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.
The effect of heat setting on the structure and mechanical properties of poly(ethylene terephthalate) fiber. I. Structural changes
Authors: Gupta V. B. , Kumar Satish
Published: April 2003

We report structural changes in commercial multifilament poly(ethylene terephthalate) (PET) yarn when it is heat set in silicone oil over a range of temperatures between 100 and 220°C for times ranging from 1 min to 1 hr, while the yarn was (1) free to relax, and (2) held taut at constant length. In one case, viz., a sample heat treated for 1 hr, the cooling time was also varied to study the effect of rate of cooling. The free‐annealed and taut‐annealed samples showed considerable differences. The predominant role of the temperature of heat setting on structure is discussed in detail. There are considerable changes in the amount and orientation of the amorphous phase, and these will be shown to have important influence on mechanical properties in subsequent reports.
Mechanical properties and superstructure of high‐modulus and high‐strength PET fiber prepared by zone annealing
Authors: Kunugi Toshio , Suzuki Akihiro , Hashimoto Minoru
Published: April 2003

The relationships between mechanical properties and superstructure of the poly(ethylene terephthalate) fiber prepared by a new annealing method called zone annealing method were investigated. The effectiveness of zone annealing was compared with three other annealing methods, namely, annealing under release, annealing at constant length, and annealing under tension. The very high modulus and strength of the zone‐annealed fiber were directly attributed to the large number of tie molecules connecting the crystallites and to the high orientation of the amorphous region.
Some theoretical aspects of bromine‐containing triazine flame retardants
Authors: Chance Leon H.
Published: April 2003

We studied flame retardancy of cotton fabric treated with five diaminotriazines containing bromine—three compounds with the bromine on aliphatic groups and two with the bromine on phenyl groups. Flame retardancy, as measured by oxygen index and FF3‐71 flammability standards, was better on the fabrics containing aliphatic bromine than on the fabrics containing aromatic bromine. Thermogravimetric analyses (TGA) and differential thermogravimetric analyses (DTG) were obtained on the fabrics, results of which supported the theory that HBr liberated during burning lowers the ignition temperature and decomposition point of the cellulose causing a reduction in flammable gases and an increase in residual char. Since CH and CBr bond strengths are stronger on aromatic groups than on aliphatic groups, our results agree with the theory that flame retardancy increases as the CBr bond strength decreases. In other words, since bromine inhibits oxidation reactions in the gas phases, the heat evolved is expected to become less as the CBr bond strength decreases.
Diffusion and induced crystallization in polycarbonate
Authors: Ware Robert A. , Tirtowidjojo Steven , Cohen Claude
Published: April 2003

The study of the effect of thickness on the mass uptake is shown to be quite helpful in the understanding of the complexities of polymer/organic penetrant sorption behavior. Isothermal diffusion results for methanol, acetone, and carbon tetrachloride in polycarbonate plates and films of various thicknesses ranging from 12 mils (0.030 cm) to 1/4 in. (0.633 cm) are presented. The diffusion is purely Fickian only in the case of methanol, which is a poor solvent for polycarbonate and has a low level of saturation in it (0.06 g/g). Methanol does not lead to a detectable swelling or any appreciable crystallization of the polymer during the diffusion process. Acetone and carbon tetrachloride are much better solvents and lead to much higher saturation levels; they crystallize polycarbonate, and their mass uptake is anomalous. The diffusion of carbon tetrachloride exhibits initially a case II diffusion behavior followed for thicker plates by an intermediate behavior between case II and Fickian diffusion. The anomalous diffusion in the case of acetone appears to be associated primarily with surface effects.
H2O2‐induced graft polymerization of acrylic acid on poly(ethylene terephthalate) fibers
Authors: Hebeish A. , Shalaby S. E. , Bayazeed A. M.
Published: April 2003

Graft polymerization of acrylic acid to poly(ethylene terephthalate) fibers using H2O2 as initiator was only possible in benzyl alcohol as reaction medium. The effect of initiator and monomer concentrations, reaction time, and temperature as well as addition of metallic salts to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing H2O2 concentrations up to 100 mequiv/L and then decreased upon further increase in initiator concentration. The same held true for acrylic acid concentration of up to 10%, but above this concentration grafting leveled off. Raising the polymerization temperature from 85 to 115°C favored grafting at lower H2O2concentration. The reverse was the case at higher H2O2 concentration (more than 25 mequiv/L). Addition of copper sulfate to the polymerization medium decreased the rate of grafting, and no leveling off of grafting could be achieved even after 5 h. The ferrous ammonium sulfate functioned similarly but to lesser degree, and leveling off of grafting occurred after 4 h. This contrasted with grafting in the absence of metallic salts where grafting leveled off after 1 h. Action of initial graft formation as diffusion barrier is believed to account for this.