bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of molecular weight distribution and branching on rheological properties of polyolefin melts
Authors: Combs R. L. , Slonaker D. F. , Coover H. W.
Published: April 2003

The objective of this work was to determine the relationships among molecular and melt parameters of polyolefins. The polyolefins studied are polypropylene, poly‐1‐butene, poly‐1‐hexene, poly‐1‐dodecene, these have regularly spaced short‐chain branches. Conclusions from previous work, as well as some new data, on polyethylene are given. As the molecular weight increases, the critical shear rate decreases but the melt viscosity and non‐Newtonian ratio increase. As the molecular weight distribution broadens, the critical shear rate decreases, whereas the normal forces and the non‐Newtonian ratio increase. Increasing the number of short‐chain branches increases the energy of activation and the melt viscosity but decreases the non‐Newtonian ratio. As the length of the short‐chain branches increases, the non‐Newtonian ratio increases, but the melt viscosity, critical shear rate, and energy of activation decrease. Increasing the number of long‐chain branches decreases the non‐Newtonian ratio, but the normal forces and the melt viscosity increase. Such information allows the polymer chemist to design a polyolefin molecule having the critical melt properties required for a given production technique.
Tensile testing device for measurements on polymeric materials between −100 and +150°C. Mechanical behavior of cellulose in liquid media
Authors: Brunnberg Ingemar , Kubát Josef , Söderlund Gunnar
Published: April 2003

A tensile testing device for measurements on polymer samples while immersed in a liquid is described. The temperature range is approximately −100 to +150°C. The sample older containing the immersion liquid is an all‐glass container attached to a modified tensile testing device. The thermostatting and recording equipment is also described. Stress–strain curves obtained with monofilaments of regenerated cellulose immersed in n‐pentane and liquid ammonia are shown. For filaments in n‐pentane the variation of the modulus of elasticity with temperature down to −40°C is also reported as a further example of the applicability of the new device.
Reactions of cotton or diethylaminoethyl cotton with 1‐chloro‐2,3‐epithiopropane
Authors: Ward Truman L. , Benerito Ruth R. , McKelvey John B.
Published: April 2003

Sulfhydryl groups have been introduced into cotton and into diethylaminoethyl (DEAE)‐cotton by reaction with neat 1‐chloro‐2,3‐epithiopropane or alcoholic solutions of the thiirane. Reactions at room temperature have been compared with those at higher temperatures, and fabric properties obtained with various S/Cl ratios have been compared. The effects of additional external base catalysis on these reactions have been studied. Fabric properties resulting from cotton–1‐chloro‐2,3‐epithiopropane or DEAE‐cotton–1‐chloro‐2,3‐epithiopropane reactions have been compared with properties obtained with the corresponding reactions of cotton or DEAE‐cotton with epichlorohydrin. Sulfhydryl groups have also been introduced into cotton and DEAE‐cotton by the in situ formation of 1‐chloro‐2,3‐epithiopropane in the fabric as a result of the reaction of the oxygen analog with a thiourea or a thiocyanate. These in situ reactions have been carried out in the absence and presence of solvent and external base catalysts. Attempts to vary the wet and conditioned (dry) recovery angles by oxidation of sulfhydryl groups and by reduction of disulfide groups met with little success. Smaller improvement in wrinkle recovery properties imparted by the thiirane than by epichlorohydrin at a given add‐on has been explained on the basis of greater tendency of the thiirane to open abnormally in neutral or slightly acidic conditions and thus the greater tendency of the thiirane to form polymers rather than to crosslink cotton. Tendency of the oxirane to open normally and therefore act difunctionally results in finished fabrics with low chlorine contents, a high degree of crosslinking, and little polymer formation.
Structure of porous cellulose acetate membranes and a method for improving their performance in reverse osmosis
Authors: Kopeček J. , Sourirajan S.
Published: April 2003

Experimental data support the hypothesis that the surface layer of the asymmetric Loeb‐Sourirajan type porous cellulose acetate membranes has a heterogeneous microporous structure. A general method is proposed for improving the performance of the above membranes in reverse osmosis, by which product rates are increased without decreasing solute separation. The method consists in pumping pure water past the back side of the membrane under just enough pressure for a sufficiently prolonged period of time; after such pretreatment, the membrane is used in the reverse osmosis experiments in the normal manner with the surface layer facing the feed solution. Back‐pressure treatment at 400 psig for 85 hr on preshrunk and normally pressure‐treated membranes increases the product rate by over 20% without decreasing solute separation in reverse osmosis experiments at 600 psig with the use of 0.5 wt‐% NaCl–H2O feed solutions; with a different sequence of back‐pressure treatment, similar results have been obtained in reverse osmosis experiments at 1500 psig also. The compaction effect of a normal membrane and that of a back pressure treated membrane are the same during continuous reverse osmosis operation under 600 psig; the effects of back‐pressure treatment on a normal membrane and a compacted membrane are also the same. The pure water permeability data obtained in cyclic experiments show that the smaller pores on the surface layer are opened more than the bigger ones during the back side operation. The probable structural changes taking place in the film during back‐pressure treatment are discussed.
Chemically crosslinked high‐density polyethylene
Authors: Narkis Moshe , Miltz Joseph
Published: April 2003

Chemical crosslinking of high‐density polyethylene was studied. The amount of gel produced by a given peroxide concentration depends on the molecular weight of the polymer. More scission reactions, during the crosslinking process, occur in low‐density than in high‐density polyethylene crosslinked with Varox and Luperox 130 peroxides. The rheological behavior of partially crosslinked polyethylene is useful and convenient for quality control, for characterization, and for studies on the various mechanisms associated with the crosslinking process.
Sulfonium polymers derived from Ar‐vinylbenzyl chloride. I. Exploratory study of the preparation and properties of the monomers and polymers
Authors: Hatch Melvin J. , Meyer Fred J. , Lloyd Winston D.
Published: April 2003

Although sulfonium salts are well known, polymeric sulfonium salts seldom have been mentioned in the chemical literature. This paper describes exploratory work in the preparation of various sulfonium monomers and polymers from ar‐vinylbenzyl chlorides (ortho and para isomers). These chlorides—particularly the para isomer—reacted readily with 2,2′‐thiodiethanol and water to yield the corresponding ar‐vinylbenzyl sulfonium chloride monomers in aqueous solution.
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The odorless, reactive monomer mixture polymerized readily with persulfate or hydroperoxide catalysts; however, polymerization could be inhibited with cupric salts. Copolymerization with trimethyl(ar‐vinylbenzyl)ammonium chloride was random. In copolymerization with acrylamide or acrylonitrile, the sulfonium monomer was more reactive. Analogous sulfonium monomers were made by reaction of ar‐vinylbenzyl chlorides with various sulfides. In general, all the sulfonium monomers yielded homopolymers which were fairly stable in aqueous solution in the absence of strongly nucleophilic agents which would attack the sulfonium groups. However, when dried at room temperature the polymers would crosslink; and when heated, the polymers became hydrophobic also. Scrambling of the sulfonium group substituents during drying, and nucleophilic displacement reactions by chloride ion during heating were likely explanations. The high cationic charge on the polymers made them substantive to cellulose fibers. This property, when coupled with high nucleophilic reactivity of the sulfonium groups with the carboxylate sites of the pulp or other anionic counterious during drying and heating, made the polymers very effective as beater additives for imparting wet strength to paper.
Embrittlement and stress cracking of polyethylene by fuming nitric acid
Authors: Hinton T. , Keller A.
Published: April 2003

Oxidative embrittlement and stress cracking of high‐density polyethylene has been studied by using fuming nitric acid at 60°C as the oxidative agent. Oxidative stress cracking was found to be insensitive to changes in molecular weight in contrast to environmental stress cracking in a surface‐active medium. The oxidative attack was found to be influenced by the surface crystalline texture of the polyethylene. Oriented polyethylene showed an increased resistance to oxidative embrittlement and stress cracking, the mode of failure being dependent upon the prior annealing treatment.
Correction of instrument spreading in gel‐permeation chromatography
Authors: Tung L. H.
Published: April 2003

Present methods of correcting instrument spreading (resolution correction) in GPC are either too cumbersome to use or inaccurate when the correction is large. Two new methods which are both accurate and simple to use are presented in this work. The first method using the technique of Fourier analysis is more general and can be used to correct non‐Gaussian instrument spreading. The second method using a fourth‐degree polynomial requires a Gaussian instrument spreading function. The instrument spreading function may vary with respect to the elution volume in both methods.
Disorder in cellulosic fibers
Authors: Viswanathan A. , Venkatakrishnan V.
Published: April 2003

Ruland's concept of an isotropic disorder function is applied to estimate the disorder parameter and the degree of crystallinity in a few cellulosic fibers: two cottons, native ramie, and a high‐tenacity rayon. The results indicate an increase in disorder without any change in crystallinity on mercerization of native celluloses. On hydrolysis, with or without a pretreatment of mercerization, the samples exhibit a higher crystallinity, disorder remaining the same as for native celluloses. A ball‐milled sample of “amorphous” cellulose is still found to be fairly crystalline with the lowest disorder. On being wetted in water and oven‐dried, a distorted form of cellulose II with higher crystallinity and disorder was obtained. The polynosic fiber, Tufcel, has low values for the degree of crystallinity, disorder parameter, as well as crystallite dimension. A strong dependence of the degree of crystallinity on the crystallite size, particularly the lateral, is observed.
Attachment of amino groups to polymer surfaces by radiofrequency plasmas
Authors: Hollahan J. R. , Stafford B. B. , Falb R. D. , Payne S. T.
Published: April 2003

Low temperature gaseous plasmas of ammonia or nitrogen–hydrogen mixtures contain NH2 groups, or precursors thereof, formed in the plasma, which experimental evidence strongly suggests, can add to various polymer surfaces. The plasmas were established in the 0.3–1.5 torr range by radiofrequency (13.56 MHz) electrodeless excitation at powers ranging from 50 to 500 W. Samples of polypropylene, poly(vinyl chloride), polytetrafluorethylene, polycarbonate, polyurethane, and poly(methl methacrylate) were investigated. All these polymers added amino groups to varying degrees of amino site densities depending on the choice of plasma parameters and the reactivity of the polymer itself. In every instance the polymer was rendered more wettable, although no quantitative wettability measurements were made. Following the plasma treatment, degrees of amino attachment to the polymer were followed radiometrically and reported in terms of “heparin thicknesses” resulting from ionic heparin 35S attachment to quaternary sites produced from the amino groups. Two implications of such a surface modification are to adhesion and blood compatible materials preparation.
Spin orientation during acrylic fiber formation by wet‐spinning
Authors: Paul D. R.
Published: April 2003

The molecular orientation acquired during fiber formation of acrylic fibers by wetspinning has been studied. Orientation was detected by measurements of sonic modulus which were converted into an orientation factor. The orientation correlates very well with the ratio of take‐up velocity to the freely extreuded velocity. Several mechanisms for the origin of spin orientation are discussed.
Efficiency of nucleating additives in polypropylene
Authors: Rybnikář F.
Published: April 2003

Investigation of the nucleating ability of selected nucleating agents in various commercial types of isolactic polypropylene revealed that the efficiency of individual additives is not equal for all types of polypropylene. As to the nucleation mechanism, it can be supposed that in most cases the added nucleating agents act mainly secondarily, activating the heterogeneities originally present in the polymer.
Study of the reaction of resorcinol, formaldehyde, and ammonia
Authors: Van Gils G. E.
Published: April 2003

Latex dip adhesives for nylon and rayon tire cords are prepared by reacting resorcinol and formaldehyde in aqueous solution in the presence of a catalyst for a specified time and then adding a butadience–styrene–vinylpyridine latex. Ammonia improves the stability of the latex and increases the adhesion of rubber to cord. However, a white precipitate forms if ammonia is added before the resorcinol and formaldehyde have reacted sufficiently. This paper is study of the nature of this precipitate and the conditions for its formation. By measuring the heat of reaction of formaldehyde and ammonia and, subsequently, of mixtures of formaldehyde and resorcinol to which varying amounts of ammonia were added, information on the reaction mechanism has been obtained. Ammonia reacts rapidly with formaldehyde to form an unstable intermediate, presumably trimethylolamine, which then reacts further with resorcinol to form trisdihydroxybenzylamine. This compound is also very reactive and condenses withmore ammonia and formaldehyde to give a polymer of low solubility, the composition depending on the amounts of ammonia and formaldehyde available for reaction. Elemental analyses support this concept. Primary and secondary amines react in a maner similar to ammonia.
Isothermal pyrolysis of cellulose: Kinetics and gas chromatographic mass spectrometric analysis of the degradation products
Authors: Lipska Anne E. , Wodley Frank A.
Published: April 2003

Untreated and fire‐retardant‐treated white α‐cellulose samples were isothermally pyrolyzed in a fluidized bath in a nitrogen environment at 298–360°C. Results were reported in terms of volatilization (based on weight loss‐time measurements) and the degradation products (based on gas chromatographic–mass spectrometric analysis). The findings products (based on gas chromatographic–mass spectrometric analysis). The findings on untreated cellulose indicate that: (1) pyrolysis occurs in three distinct phases in the temperature range 276–360°C; (2) there is a single activation energy of 42 kcal/mole over this temperature range; (3) the initial rapid weight loss is not due to the desoprtion of water, but primarily to decomposition of the cellulose; molecules: (4) there is little difference in either the quality or relative quantity of the volatiles generated during the three different phases of pyrolysis. The findings on treated cellulose show that the fire retardant, KHCO3, does not markedly change the types of degradation products having molecular weights below about 110, althought it does change their relative concentrations. Furthermore, the rate of product generation and the quantity of residual char are increased.
Studies on selenium–organic polymer interfaces
Authors: Chiang Y. S. , Ing S. W.
Published: April 2003

Interfaces of evaporated viterous selenium and various organic polymeric resins of both the thermosetting and thermoplastic type have been studied by ultra‐thin sectioning and transmission electron microscopy techniques. Epoxy, phenoxy, polyamide, butadien–styrene copolymer, vinyl‐toluene–butadiene copolymer, resins as well as polyethylene are among those organic polymers studied. Interfaces prepared by vaccum evaporation of selenium onto the various substrates and under varying processing conditions were examined. Intermixing and interdiffusion of the inorganic and organic polymers in the interfacial region were observed in certain cases when selenium was evaporated onto incompletely curved epoxy or lower viscosity polymers. These occurrences were found to contribute significantly to the mechanical strength of the assembly. Electrical properties of certain specific systems have also been investigated.
Liquid‐induced crystallization of poly(ethylene terephthalate)
Authors: Lawton E. L. , Cates D. M.
Published: April 2003

Amorphous unoriented poly(ethylene terephthalate) was crystallized at 25°C by various organic liquids. The crystalliznity induced in the amorphous polymer was measured by differential scanning calorimetry and infrared spectroscopy. The ability of liquids to interact with and induced crystallinity in the amorphous polymer was classified on the basis of their solubility parameters. Measurements of the density of liquid‐crystallized 0.8‐mil films of poly(ethylene terephthalate) indicated the presence of extensive internal voids in the semicrystalline polymer matrix. Comparison of differential scanning calorimetric thermograms and infared spectra of heat‐crystalized and liquid‐crystallized polymer indicated significant differences in the polymer morphologies induced by the two crystallization processes.
Greffages mecanochimiques sur le polychlorure de vinyle. I. Polyméarisations amorcéaes par le malaxage
Authors: Guyot Alain , Michel Alain
Published: April 2003

The grafting of methyl methacrylate and of methacrylic esters on poly(vinyl chloride) by mechanicochemical synthesis can be performed in the Brabender Plastograph. These monomers possess sufficient intermolecular plasticizing power to bring the poly(vinyl chloride)‐monomer system into the viscoelastic state required for the formation of free radicals by homolytic scission of polymeric chains. Nevertheless several other monomers (among them the styrene) have interstructural plasticizing ability and can be grafted by mechanicochemical synthesis by addition of an intermolecular plasticizer or a monomer of the first class (methyl methacrylate). Also, except for basic monomers, the monomers stabilize poly(Vinyl chloride) during the mastication, probably because they act as free‐radical scavengers.
Greffages mecanochimiques sur le polychlorure de vinyle. II. Éatude des copolymègres grefféas
Authors: Michel Alain , Galin Monique , Guyot Alain
Published: April 2003

The copolymers obtained by mastication of poly(vinyl chloride) (PVC) in presence of methyl methacrylate and styrene monomers, and their fractions, were studied by using infrared spectroscopy, NMR, and flash pyrolysis. The degree of alternation between vinyl chloride and methyl methacrylate or styrene units is very low, and the copolymers are heterogeneous in composition. The results suggest that the mastication medium involves three kinds of domains: the inner part of the elementary grains of PVC is very slightly penetrated by the monomers. The polymerization initiated by the polymeric free radicals created by the rupture of bonds, begins in the surface layers of the grains and cause the formation of a true copolymer which accounts for 5–10% of the material. Light radicals arising from transfer reaction migrate into the third external domain which consists practically entirely of pure monomers and initiate polymerization.
Greffages mecanochimiques sur le polychlorure de vinyle. III. Stabilitéa thermique des polymègeres modifiéas
Authors: Michel Alain , Bert Michel , Guyot Alain
Published: April 2003

The mastication of poly(vinyl chloride) (PVC) in presence of monomers causes important changes of the thermal stability of the polymer when the last one possesses a basic character (e.g., 2‐vinylpyridine). The dehydrochlorination rate is greatly increased, even if the monomer is present in only small amounts. In the most cases (styrene, acrylic ester) a better thermal stability is observed with respect to the acceleration of the dehydrochlorination, which is retarded or even suppressed. Infrared spectroscopy and differential thermal analysis show that the improved stability is due to an improved crystalline organization. When mastication causes the polymerization of the monomer (methyl methacrylate), degradation of the PVC part and depolymerization of the rafted part are observed simultaneously; this fact supports a radical mechanism for the thermal degradation of the PVC.
Tensile behavior of glass fiber‐reinforced acetal polymer
Authors: Hardy G. F. , Wagner H. L.
Published: April 2003

The tensile stress‐strain behavior of glass fiber‐reinforced polyacetal resin was investigated for various fiber concentrations, fiber length distributions, and finishing agents. The polyacetal fiber blends change considerably in strength and elongation at break when treated with ammonium chloride, but otherwise similar specimens still follow a common stress‐strain curve to a point shortly before failure. As the mean fiber length decreases, the modulus and tensile strength fall, but the elongation at break remains almost unchanged. The observed tensile behavior is discussed in terms of a simplified model, which assigns the fibers to two categories: a fraction α parallel to the applied load, and the remainder distributed in a plane perpendicular to the load axis. By fitting this model to the stress‐strain curves, two other constants of each system are derived: a length‐dependent efficiency factor β for parallel fibers, whose magnitude agrees with the predictions of Rosen and his co‐workers, and a factor γ which expresses the constraint of the matrix resin by the “transverse” fibers. The behavior of γ is consistent with Tsai's theory of the transverse modulus of laminates, if a reasonable amount of fiber–fiber contact is assumed. In terms of this model, possible interpretations of the behavior under repeated loading and the mechanism of tensile failure are presented.
Thermal properties of an epoxide resin cured with bicyclo Diels‐Alder anhydride adducts
Authors: Fleming Gerald J.
Published: April 2003

The thermal properties of polymers derived from resorcinol diglycidyl ether cured with several bicyclo Diels‐Alder anhydride adducts have been investigated. Increased char yields and decreased rates of weight loss were observed for these systems as compared to polymers cured by Diels–Alder adducts from acyclic dienes. This is explained on the basis of a reverse Diels‐Alder reaction which these bicyclo adducts undergo at lower temperatures than do adducts from acyclic dienes.
Influence of elastic effects on capillary flow of molten polymers
Authors: McLuckie Colin , Rogers Morris G.
Published: April 2003

Capillary viscometer measurements for a number of polyethylenes and polystyrenes reveal deviations from linearity in plots of applied pressure versus capillary length to diameter ratio, at constant rates of shear, resulting in apparently negative end corrections. This is contrary to previous physical considerations. Some polymers obey Hooke's law in shear permitting the separation of the end correction into two components. A Couette correction, dependent upon the capillary dimensions, is constant for any given polymer, shear rate, and temperature; an elastic shear strain correction, dependent upon the transit time through the capillary, may be determined by post‐extrusion measurements. Determination of these two correction leads to linear plots of pressure versus capillary length to diameter ratio and enables flow curves to be calculated independent of the capillary dimensions and the swell properties of the polymer.
Young's modulus and secondary mechanical dispersions in polypromellitimide
Authors: Butta Enzo , De Petris Silvano , Pasquini Mario
Published: April 2003

Dynamic mechanical properties were determined in polypyromellitimide at acoustic frequencies over a wide temperature range (80–750°K). Two distinct secondary relaxation effects were found: one (β′) at lower temperature, characterized by a loss maximum at 250°K, and another (β) at higher temperatures with a loss maximum at 400°K. The lower temperature peak is shifted towards higher temperature with increasing frequency following an Arrhenius‐type equation (apparent activation energy: 15 kcal/mole); the relaxation strength increases with water content and becomes practically zero when samples dried under vacuum at 200°C are examined. The β′ relaxation process is thus attributed to the presence of adsorbed water molecules. The higher‐temperature (β) dispersion, which persists even after dehydration, on the basis of some results obtained for other polymers containing p‐oxylphenylene rings in the backbone, is tentatively attributed to torsional oscillations of aromatic rings along the chain.
Adhesion of metals to polymers. I. Study of interfaces modified by inductive heating
Authors: Raff R. A. V. , Sharan A. M.
Published: April 2003

The objective of the work reported in this paper is to explain theoretically the observations made in an earlier study that castings of an epoxide resin reinforced by electrically conductive inserts, after having been postcured by inductive heating, had strength properties superior to those achieved by a purely thermal postcure. A search of the literature on adhesion suggested that among the theories presented, those dealing with electrical double layer formation, interdiffusion, and mixed polymer grafting on the insert–polymer interface deserve to be considered. Experiments were then planned in such a manner as to permit a choice between these theories. Epoxide resin specimens reinforced with various metals (pure silver, silver with an oxide layer, pure copper, copper with an oxide layer, aluminum, and stainless steel) were prepared. They were then either postcured in a heated oven, or postcured in an induction furnace for various lengths of time. Bonding strength was determined by a knife‐edge method, and the exposed insert and resin surfaces were tested for electrical potential and surface wettability (angle‐of‐contact). Most strikingly, the curves obtained with increasing induction heating times for bonding strength, electrical potential, and wettability were all sinusoidal in shape, and their maxima and minima generally were found to coincide. For oven‐postcured specimens, bonding between different metal inserts and an epoxide resin is explained by double electrical layer formation (insert positive, resin negative), with bonding strength increasing as the stability of the oxide forming the surface layer of the metal decreases. Metals with no oxide surface layer thus have the highest bonding strengths. For inductively postcured specimens, bonding is effected by both electrical double layer formation and mixed polymer grafting through the oxygen atoms in the metal surfaces, with the more stable metal oxide giving the stronger bonding in grafting. Where the insert does not carry an oxygen surface layer, bonding takes place through electrical forces only. Alternating build‐up and internal discharge of electrical double layers are the direct cause of the sinusoidal shape of the electrical potential curves and the indirect cause of the comparable shape of the wettability curves. Their combination results in the observed periodicity of the breaking load curves.
Structural modification and molding of polyacrylonitrile
Authors: Griffith Russell K. , Zorska Roman
Published: April 2003

Polyacrylonitrile can be compression‐molded with conventional equipment if the inherent polymer particle structure is modified. With normal polymerization methods, a circumferential orientation in the polymer particle is obtained. This structure can be changed under the effects of shear to yield highly ordered, laminar particles with planar orientations. In this form, PAN can be compression‐molded into tough, clear, chemically resistant articles with retention of the laminar structure. The polymer has been characterized by its x‐ray diffraction and infrared spectrum which, in combination, distinguish it from previously observed forms of PAN.
Moisture determination in plasticizer–pigment formulations by gas chromatography
Authors: Slanski J. M. , Jacin H. , Moshy R. J.
Published: April 2003

A rapid quantitative method has been developed for the determination of small amounts of water present in plasticizer‐pigment and epoxy resin–pigment dispersion used in polyurethane formulations. Specific dispersions examined have been the systems diisooctyl phthalate–titanium dioxide and titanium dioxide–epichlorhydrin–Bisphenol A. The samples examined contained 50–70% titanium dioxide.
Role of hydrophobic bonding in the contraction of nylon 66 in phenolic solutions
Authors: Jacobs Martin I.
Published: April 2003

Rate constants for intermolecular bond breaking (k1) and bond re‐formation (k2) were calculated from contraction measurements. Variation of ΔH‡ and ΔS‡ for k1 with phenol substituents and concentration suggests the existence of hydrophobic bonding between the solution and the polymer activated complex. This behavior has been substantiated by correlating ΔH‡ and ΔS‡ for k1 with a parameter related to hydrophobicity.
The effect of time and temperature on the mechanical behavior of a “plasticized” epoxy resin under different loading modes
Authors: Moehlenpah A. E. , Ishai O. , Dibenedetto A. T.
Published: April 2003

Epoxy–Versamid specimens were loaded in tension, compression, and flexure at different strain rates and temperatures to determine mode of failure, yield stress and strain, and tangent and relaxation moduli. Stress‐strain curves were used to define brittle, ductile, ductile‐rubbery, and rubbery modes of behavior which prevailed in different temperature‐strain rate regions. The time‐temperature superposition principle was applied to yield stress, initial tangent moduli, and relaxation moduli data for all three types of loading.

The transition regions, tangent and relaxation moduli, and shift factors were the same in tension, compression, and flexure. Thus the most convenient mode of loading can be used to determine the general time‐temperature dependence. The ratio of compressive‐to‐tensile yield stress was almost constant over the entire ductile region. Flexural yielding data were used to predict yield stress in tension and compression, and stress relaxation master curves were shown to be related to elastic modulus vs. strain rate curves. The yielding phenomenon was interpreted using Eyring's theory of non‐Newtonian viscoplastic flow. The apparent activation energy and activation volume were larger for tension than compression. A theory is offered to explain why yielding can occur in a cross‐linked system.
Use of gas‐liquid chromatography in the analysis of rigid polyurethane foam polyols
Authors: Corbett G. E. , Hughes W. , Morris‐Jones R. G.
Published: April 2003

Detailed characterization of the low molecular weight polyols used as intermediates in rigid polyurethane foam production has not been feasible to date. Gas‐liquid chromatography of the trimethylsilyl ether derivatives of the polyols now offers a more complete picture of polyol composition, particularly with regard to the molecular weight distribution. The data may be interpreted on a semiquantitative basis. The study of processing variables in polyol manufacture, detection of impurities and analysis of unknown polyols or those based on mixed initiators may all be facilitated by use of this GLC technique.
Mechanisms of antioxidant action: Effects of sulfur compounds on the melt stability of polypropylene
Authors: Scott Gerald , Shearn Peter A.
Published: April 2003

The effects of a number of sulfur compounds on the melt stability of polypropylene milled at 165°C have been studied. Dilaurylthiodipropionate (DLTP), Mercaptobenzimidazole (MBI), and Mercaptobenzthiazole (MBT) are all antioxidiants in a polymer lightly stabilized with a phenolic antioxidant although the last two are initially pro‐oxidants. 2,2′‐Dibenzoylaminodiphenyldisulfide (22BDD) is a pro‐oxidant under the Conditions studied.

In the absence of a phenolic antioxidant the effectiveness of DLTP is reduced in the early stages of oxidation, with increasing concentration although its over all antioxidant activity increases. The results are consistent with the view that both radical and non‐radical processes occur concomitantly.
Several reactions of poly(vinyl alcohol)–type acetaldehyde polymer
Authors: Matsubara Tsutomu , Imoto Tatsuya
Published: April 2003

The preparation of the acetaldehyde polymers (PACH) having a poly(vinyl alcohol)‐type structure and the thermal degradation of PACH have been reported previously. This paper will describe detailed aspects of several reactions of PACH. Copolymerization of PACH with toluene diisocyanate (TDI) was performed both thermally and catalytically. When piperidine was used as catalyst, the rate of reaction between PACH and TDI was found to depend on the concentration of both the active hydrogen of PACH and the isocynante group TDI. Acid and alkali treatment of PACH were carried out. On treatment with sulfuric acid, white polymers with good spinnability were obtained. The copolymerization of acetaldehyde with n‐butylaldehyde were performed in the presence of sodium amalgam as catalyst. The reaction products were colorless, viscous liquids and assumed from the infrared and NMR spectra, elemental analyses, molecular weight and solubility tests to be aldol condensation‐type copolymers.
Polymerization of trithiane
Authors: Takeda Jun‐Ichi , Hayashi Koichiro , Okamura Seizo
Published: April 2003

The catalytic solid‐state polymerization of trithane to polythiomethylene has been studied. The polymerization can be initiated by wide varieties of substances such as metal salts, halogen, and active organic halides. The polymerization proceeds in solid‐state without topochemical process. The catalytic irreversible degradation of polythiomethylene to dimethyl sulfide and carbon disulfide has been observed.
A new method for calculating and correcting molecular weight distributions from gel permeation chromatography
Authors: Chang Kung S. , Huang Robert Y. M.
Published: April 2003

A new method for calculating and correcting molecular weight distributions of polymer samples from GPC chromatograms is presented. The integral equation which relates the true molecular weight distribution of polymer sample to the chromatogram is reformulated into an equivalent variational problem of quadratic functional. The method of steepest descent in the function space is then applied to the minimization problem to obtain the true molecular weight distribution. This method is efficient and reduces some of the oscillation problems encountered in the previous methods. Examples are given.
Selectivity of the epoxide phenol reaction
Authors: Alvey Francis B.
Published: April 2003

A method for determining the relative amount of alcohol side reaction which occurs in reactions of epoxy compounds with active hydrogen compounds has been investigated. It involves determining the ratio of rates of the successive reaction, epoxide‐active hydrogen compound and epoxide‐generated secondary alcohol, in the reaction of epoxide and active hydrogen compound at respectively a 2:1 mole ratio. Rate ratios are reported for the bulk reaction of bisphenol‐A and the diglycidyl ether of bisphenol‐A under different reaction conditions. The data correlated with the properties of high molecular weight polymers. Amines with β‐hydroxyl groups were very selective catalysts.
Gel permeation chromatography: The effect of treatment with hexamethyldisilazane on porous glass packings
Authors: Cooper Anthony R. , Johnson Julian F.
Published: April 2003

Porous glass column packings have been shown to be an effective substrate for gel permeation chromatography. When carbon tetrachloride is used as a solvent in conjuction with infrared detection, the porous glass exhibits adsorptive properties with polystyrene and polyisobutene. A procedure to eliminate these undesirable properties by treatment with hexamethyldisilazane has been developed. Experiments showed complete elution of all injected polymer. The treatment thus permits quantitative fractionation studies using infrared detection.
Effects of termonomers on crosslinking rate and crosslinking structure of ethylene propylene terpolymers
Authors: Fujimoto K. , Nakade S.
Published: April 2003

Study was made concerning both the rate of crosslinking and the structure of crosslinks of terpolymers that have dicyclopentadiene, 1, 4–hexadiene, methylene norbornene, and ethylidene norbornene for termonomers so as to look into the role of termonomers during crosslinking of ethylene propylene terpolymers. In the study, activation energy and frequency factor, both apparent were determined by the rate constant of crosslinking and differences in crosslinks were analyzed following both chemical and physical methods. Infrared analysis into the volume of consumption of double bond was adopted to examine the manner of crosslinking. In respect to the magnitude of the rate constant, ethylidene norbornene came in first being followed by 1,4‐hexadiene, methylene norbornene, and dicyclopentadiene. The structure of termoners affected the apparent activation energy and the apparent frequency factor was subject to the influences of said structure and others including the variation in the degree of unsaturation. During the early stage of crosslinking, the formation of the crosslink of polysulfide‐type was paramount to all others and the speed of conversion therefrom either to disulfide–type or to monosulfide varied with the kind of terpolymers and was in proportion to the rate constant of crosslinking.
Modification of polyethylene surfaces with carbethoxy substituted carbenes and nitrenes
Authors: Osteraas A. Jean , Olsen Douglas A.
Published: April 2003

Carbethoxycarbene, carbethoxynitrene, and nitrene generated respectively by the pyrolysis of ethyl diazoacetate, ethyl azidoformate, chloramine and sodium hydroxyl amine‐o‐sulfonate are shown to irreversibly modify the surface of polyethylene as shown by wettability measurements. The nature of the modification is not fully understood; however, insertion of the carbene or nitrene into a carbon‐hydrogen bond appears likely. The modified surfaces thus formed are shown to undergo several classical organic reactions as again determined by wettability measurements.
Homo‐and copolymers of vinyl esters, acrylates, and methacrylates of some derivatives of fatty acids
Authors: Chow Roberta C. L. , Marvel C. S.
Published: April 2003

Vinyl esters of some undecylenic acid derivatives and acrylates and methacrylates of undecyl and undecylenyl alcohols, which may be considered as derivaties of castor oil, have been polymerized and copolymerized with vinyl chloride to provide a variety of new polymers. The acrylate and the methacrylate of undecylenyl alcohol have been epoxidized to yield two new polymerizable monomers of potential usefulness as crosslinking agents in finished copolymers.
Thermal degradation of polymers. part IV. Vacuum pyrolysis of poly(m‐aminostyrene). The residue and the fraction volatile at pyrolysis temperature involatile at room temperature
Authors: Still R. H. , Jones P. B.
Published: April 2003

The effect of the extent of degradation of poly(m–aminostyrene) on the quantity and composition of the residue and the effect of pyrolysis temperature on the fraction volatile at pyrolysis temperature are discussed. The behavior of poly(m–aminostyrene) is compared to that of polystyrene; a significant difference has been found for the behavior of the residue from poly(m–aminostyrene), which is ascribed to a crosslinking reaction involving the amino substituent. Mechanisms to acount for the observed products of degradation have been suggested and are discussed. Relative thermal stability studies have also been made and compared with results from polystyrene.
Effect of lignin in graft copolymerization of methyl methacrylate on cellulose by ceric ion
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

The effect of lignin contained in cellulosic materials in graft copolymerization of methyl methacrylate on such materials using ceric ion as initiator was studied. It was found that the percent grafting and the average molecular weight of grafts became lower in samples having a larger lignin content but the number of grafts formed increased proportionally up to lignin content of about 2.5%. Ceric ion reacted at a faster rate with lignin than with cellulose in wood pulp, and the results indicating that the active sites formed on lignin by oxidation with ceric ion accelerate the formation of grafts and increase the number of grafts were obtained. But on the other hand, the active sites participated in the termination reaction of the growing graft polymer radicals to cause lowering of the average molecular weight of grafts.
Multiple glass transitions in butadiene‐acrylonitrile copolymers
Authors: Chandler Lyle A. , Collins Edward A.
Published: April 2003

The second order transition temperatures (Tg) have been determined for a range of compositions of polybutadiene‐acrylonitrile copolymers. It was found that copolymers having more than 36 percent acrylonitrile had a single Tg while copolymers with less than 36 percent acrylonitrile had two main Tg's. The analyses were carried out with differential thermal analysis (DTA). The two Tg's are interpreted as the result of incompatible phases which differ in BD and VCN ratio. The presence of two phases is discussed in terms of polymerization conditions and molecular structure.
Comparison of Fe2+H2O2 and Fe3+H2O2 initiation systems in graft copolymerization of cellulosic materials
Authors: Ogiwara Yoshitaka , Kubota Hitoshi
Published: April 2003

Studies were carried out on decomposition of hydrogen peroxide by ferrous and ferric ions adsorbed on cellulosic materials (SP, SCP), scission of the cellulose chain and formation of grafts by graft copolymerization. As a result, it was found that the activity of ferrous ion is always higher than that of ferric ion, but there exists a common relation between the amount of decomposition of hydrogen peroxide and the number of grafts for all cellulose samples and kinds of metallic ions, and it was inferred that essentially, copolymerization takes place by the same mechanism irrespective of the kind of metallic ions. Consequently, it can be considered that the difference in degree of activity between ferrous ion and ferric ion is due to the difference in the decomposition mechanism of hydrogen peroxide by these metallic ions and it is assumed that the high activity of ferrous ion in graft copolymerization is due to the high hydrogen peroxide decomposition effect.
The stress cracking of polyamides by metal salts. Part I. Metal halides
Authors: Dunn P. , Sansom G. F.
Published: April 2003

The stress cracking of polyamides (nylons) by a number of metal salts, in aqueous and nonaqueous solutions, has been investigated. Many metal halides and halide‐like salts were found to be active stress‐cracking agents, while metal acetates and sulfates were inactive. Zinc chloride was found to be most active, and its activity was compared with other metal halides. Using a recording tensometer, time to crack initiation, time to crack‐through and time to rupture were determined. These parameters were found to be dependent on temperature, moisture content of the nylon, concentration of the cracking agent and level of stress. High values of all these factors favored rapid cracking. Cracking parameters were shown to be mainly independent of the surface geometry of the nylon and the hydrogen ion concentration of the cracking agent. Metal halides did not appear to cause any chain scission in the nylon and stress cracking was not due to hydrolysis or metal‐ion catalysed hydrolysis.
The stress cracking of polyamides by metal salts. Part II. Mechanism of cracking
Authors: Dunn P. , Sansom G. F.
Published: April 2003

The action of metal halides on polyamide (nylon 6) and secondary amide model compounds has been investigated, using infrared and NMR techniques. Metal halides, which are active stress cracking agents for polyamides, induce characteristic changes in the spectra of both nylon 6 and the model compounds. Two types of changes were observed, depending on the metal halide involved, and on this basis the metal halides have been classified as Type I or Type II. The spectral changes appear to be due to the formation of complexes between the amide group and the metal halide, and structures for these complexes are proposed. Type I metal halides, such as zinc, cobaltII, copperII and manganeseII chlorides, form complexes in which the metal atom is coordinately bonded to the carbonyl oxygen atom of the amide group. These agents cause stress cracking by interference with the hydrogen bonding in the polyamide. Type II metal halides, such as lithium, calcium and magnesium chlorides and lithium bromide in solution form proton donating, solvated, species which act as direct solvents for nylon 6 in a manner similar to phenols and formic acid. Type II agents appear to cause simple solvent cracking.
The stress cracking of polyamides by metal salts. Part III. Metal thiocyanates
Authors: Dunn P. , Sansom G. F.
Published: April 2003

The stress cracking of polyamide (nylon 6) by a number of metal thiocyanates in aqueous and nonaqueous solutions has been investigated. Lithium, zinc and cobaltII thiocyanates were the most active and their activity was compared with that of the corresponding metal halides. Stress cracking parameters were determined and the mechanism of cracking studied by infrared techniques. The action of metal thiocyanates on nylon 6 is similar to that of the corresponding metal halides. Some metal cobaltothiocyanates were also found to be active stress cracking agents.
Studies of water adsorbed on cellulosic materials by a high resolution NMR spectrometer
Authors: Ogiwara Yoshitaka , Kubota Hitoshi , Hayashi Shoichi , Mitomo Noriko
Published: April 2003

A study of water contained in cellulose samples softwoods dissolving pulp (DP) and hardwoods semichemical pulp (SCP) by a high resolution NMR spectrometer indicated the presence of two regions, one where the width at half value decreased rapidly with increasing water content and the other where the width at half value decreased slowly. As a result of a treatment for increasing the hydrophilicity of cellulose fibers such as beating, swelling by sodium hydroxide, and hydrolysis with hydrochloric acid, the differential energy of water binding increased in the low water content region, whereas it either did not change or decreased in the high water content region in spite of an increase in the amount of water, which is subject to the influence of the cellulosic materials. A comparison of different cellulosic materials showed that the differential energy of water binding of SCP was larger than that of DP. Moreover, an investigation of the relationship between the width at half value and the temperature indicated that different temperature ranges exist regarding binding of water, and such ranges are affected greatly by the degree of beating and the water content of the sample.
Comments on the reactivity of methoxy pentadecyl phenyl isocyanate isomers
Authors: Carignan Yvon P.
Published: April 2003

The reactions of 2‐methoxy‐4‐pentadecyl phenyl isocyanate and 4‐methoxy‐2‐pentadecyl phenyl isocyanate with excess 2‐ethyl hexanol originally reported by Ghatge and co‐workers to follow zero order kinetics have been re‐examined on the basis of their data and shown to follow more realistically the product catalyzed pseudo first order kinetics. The new rate constant, ks (sec−1) for the spontaneous reaction and kp (li. mole−1 sec−1) for the product catalyzed reaction are found to be: ks = 0.57 × 10−6 and kp = 34 × 10−6 for 2‐methoxy‐4‐pentadecyl phenyl isocyanate and ks = 1.2 × 10−6 and kp = 82 × 10−6 for 4‐methoxy‐2‐pentadecyl phenyl isocyanate.