bluuebunny/crossref_metadata_2025 huggingface dataset:
The mechanism of radiation damage to elastomers. I. Chain scission and antirad action
Authors: Bauman Richard G. , Born John W.
Published: April 2003

The effect of antirads on the gamma radiation yields of scission in black loaded natural rubber stocks has been studied. The yield of chain scission has been measured by stress relaxation methods. The antirads were found to decrease the rate of chain scission, both in air and under nitrogen, with the antirad effectiveness being greater in the former case. The presence of oxygen accelerated the radiation induced chain scission. These results may be explained if it is assumed that (1) RO2 · radicals lead to chain scission more readily than do R · radicals, and (2) RO2 · radicals react with antirads leading to stabilized products more readily than do R · radicals.
The gelation of plastisols: An automatic method for the determination of plastisol temperature‐rheology characteristics
Authors: Alter Harvey
Published: April 2003

A technique is described for the small scale evaluation of plastisol formulations for molding, casting, coating, and foam applications. The technique described rapidly measures and automatically records the viscosity of a plastisol as a function of temperature by means of a Bendix Ultra‐Viscoson and thermocouple. The measurements are made under conditions that closely approach process conditions. Small changes are accurately followed and the portion of the curve in the vicinity of gelation is amplified. The shape and position of the viscosity‐temperature plot are dependent on the chemical nature of the plasticizer as well as the intrinsic viscosity and molecular weight distribution of the dispersed polymer. The resulting curves can be used to choose plastisol compositions for a given application. The application of the curves to foam and rotational casting formulations is outlined.
A modification of the method of intermittent stress relaxation measurements on rubber vulcanizates
Authors: Ore Svein
Published: April 2003

The method of continuous and intermittent stress relaxation measurements on rubber vulcanizates developed by Tobolsky and co‐workers has been modified by the introduction of intermittent tangent modulus measurements during the continuous relaxation experiments. This allows rate of scission and crosslinking to be determined simultaneously and on the same specimen. The method is based on the use of small or moderate extension ratios α and on the fact that in this case the stress f in actual rubbers is represented more closely by the empirical relationship f = 3G(1−1/α) than by the theoretical f = G[α−(1/α2)], where 3G denotes Young's modulus at infinitesimally small strains.
The mechanism of radiation damage to elastomers. II. Crosslinking and antirad action
Authors: Bauman Richard G.
Published: April 2003

The effect of antirads (compounds added to reduce changes of polymer properties during irradiation) on the crosslink yields in black‐loaded natural rubber stocks during gamma irradiation has been measured. The crosslink yields were determined by swelling techniques. Antirads decrease the crosslink yields if oxygen is absent. Oxygen alone effectively decreases crosslink yields. In the presence of oxygen some antirads further decrease crosslink yields, while others increase crosslink yields by their presence. These results may be explained in terms of competitive reactions between R. radicals, the antirad, and oxygen. Evaluation of the ratios of crosslink yields and scission yields indicate that most of the scission is temporary in nature, the chain breaks being reformed rapidly.
A statistical study of the effect of formulation variables on the properties of sorbitol polyether‐based rigid urethane foam
Authors: Wilson J. E. , Truax H. M. , Dunn M. A.
Published: April 2003

Each rigid urethane foam formulation must be carefully designed to meet the key requirements of its specific end use. For example, refrigerator insulation is an application which requires low thermal conductivity, low density, and excellent resistance to humid aging. The present investigation was carried out to determine variations in foam properties caused by changes in catalyst concentration, isocyanate/hydroxyl ratio in the quasi‐prepolymer, quasi‐prepolymer cooking time, dispersing agent concentration, and isocyanate/hydroxyl ratio in the total foam. The basic foam formulation contained sorbitol polyether (Hydroxyl Number 490), toluene diisocyanate, trichlorofluoromethane blowing agent, catalyst, and dispersing agent. The results showed that the tensile strength decreased as the isocyanate/hydroxyl ratio in the total foam increased. Shear strength was affected strongly by catalyst concentration, and by isocyanate/hydroxyl ratio in the prepolymer and in the total foam. Cure time (at room temperature) was strongly affected by catalyst concentration and technique of prepolymer preparation. The only factors having a significant effect on humid aging resistance were isocyanate/hydroxyl ratio in the prepolymer and in the total foam. The effects on thermal conductivity were complex, and included an interaction between dispersing agent concentration and catalyst concentration, and also between prepolymer preparation technique and isocyanate/hydroxyl ratio in the prepolymer. The compressive strength increased with catalyst concentration, and was strongly affected by prepolymer preparation techniques. Key effects and interactions were plotted in graphical form.
Effect of concentration of inhibitors and retarders on the catalyzed polymerization of styrene
Authors: Sugihara James M. , Wright Richard D. , Ernsdorff Bede
Published: April 2003

The effect of varying concentrations of several common retarders and inhibitors on the polymerization of bulk styrene, catalyzed by benzoyl peroxide, was studied dilatometrically at a temperature of 86°C. At a benzoyl peroxide concentration of 1.77 × 10−3M, the rate of volume contraction was found to be 1.472 ± 0.103%/hr. or approximately 7.4–8.5% polymerization/hr. The rate constant for the decomposition of benzoyl peroxide in styrene was found to be 36.5 × 10−6 sec.−1 at 86°C. At any given concentration for the several retarders and inhibitors, data were obtained which provided plots of extent of polymerization versus time of three different types. Trinitrobenzene and N‐(3‐N‐hydroxyanilino‐1,3‐dimethylbutylidene)aniline N‐oxide gave plots with single lines describing retarded rates of polymerization; diphenylpicrylhydrazyl and the free radical obtained from N‐(3‐N‐hydroxyanilino‐1,3‐dimethylbutylidene)aniline N‐oxide provided plots showing decreased rates of volume contraction following inhibition periods; and diphenylpicrylhydrazine and benzoquinone gave plots with two intersecting lines, suggesting two discrete steps. Concentrations of regulators were varied between 0.0002 and 0.0027M. In every instance plots of slopes of lines, inhibition times or intersection points versus concentration or logarithm of concentration provided straight lines.
Ultrafiltration of salt solutions by ion‐excluding and ion‐selective membrances
Authors: Reid C. E. , Spencer H. G.
Published: April 2003

Salt‐filtering properties of several polymeric membranes were investigated at 40 atm. applied pressure. The ultrafilters were classified as ion‐excluding or ion‐selective membranes according to their ohmic resistance to the ions of the sodium chloride test solution. Membranes containing hydrophilic groups which have a high resistance to both cations and anions are classified as ion‐excluding. Polyelectrolyte membranes with high resistance to cations only are considered to be ion‐selective. In addition to cellulose acetate, which has been investigated previously, cellulose isobutyrate, cellophane‐supported polyvinyl methyl ketone, and cellophane‐supported polyvinyl acetate were found to be ion‐excluding membranes. The amorphous membranes, polyvinyl methyl ketone and polyvinyl acetate, do not reject salt alone; the cellophane appears to provide a supporting matrix which restricts the interchain distances in the interfacial region. Membranes composed of mixtures of the 1:1 copolymer of methyl vinyl ether and maleic anhydride with polyvinyl alcohol were durable, ion‐selective salt filters. Baking these membranes reduced swelling and flow rate and increased salt rejection. Those membranes containing high concentrations of the copolymer were flimsy and required bonding to a cellophane supporting membrane in order to obtain high salt rejection. The effects of process variables on the ultrafiltration properties of the ion‐selective membranes were also investigated. The salt rejection by either class of membrane depends on both a high concentration of the required functional groups and restricted interchain distances. Despite differences in the mechanism, each class behaves as a filter, in that the smaller the pores, the more effective the separation and the lower the flow rate.
Influence of the initiator on the grafting of polyvinyl polymers
Authors: Smets G. , Roovers J. , Van Humbeek W.
Published: April 2003

The dependence of grafting on the type of initiator has been examined in the case of three polymer–monomer systems: polystyrene–methyl methacrylate, polymethyl methacrylate–vinyl acetate, and polyethyl α‐chloroacrylate–vinyl acetate. The different initiators used in these experiments were benzoyl peroxide (Bz2O2), azobisisobutyronitrile (AIBN), di‐tert‐butyl peroxide (DTBP), and tert‐butyl hydroperoxide (TBHP). In each case the graft copolymers were separated from the homopolymers by fractional precipitation or by extraction. In the case of the system polystyrene–methyl methacrylate, an appreciable degree of grafting as well as formation of graft copolymer occur in the presence of Bz2O2; in contrast, the grafting is low with DTBP and doubtful with AIBN. For the other two systems no noticeable differences occurred as function of the initiator. In the case of polyethyl α‐chloroacrylate the amount of graft copolymer is exceptionally high owing to the sensitivity of this polymer to a radical attack; this sensitivity results in the partial insolubility of the graft copolymers in the presence of TBHP and DTBP, but not in the presence of AIBN.
Determination of residual styrene (monomer) and acetophenone in polymer latices
Authors: Murphy John E. , Forrette John E.
Published: April 2003

A rapid, quantitative, direct procedure for the determination of monomeric styrene in a styrene‐based polymer emulsion has been developed. The method includes the extraction of styrene in cyclohexane and a subsequent measurement of the ultraviolet absorbance of the solution. Determination of, and compensation for interference from, acetophenone is also described. The range of 0–5% monomeric styrene was studied by statistical methods.
The mechanism of film formation from viscose
Authors: Miller M. , Haskell V. C.
Published: April 2003

The coagulating and regenerating conditions that are necessary for the formation of a highly durable cellulosic film are described. It is shown that low orientation, low lateral order, low gel swelling, and cellulose with a high DP are primary requisites for best film properties. Experiments demonstrated that the application of a unidirectional stress produced an unbalance of physical properties in the film, and this, in general, had an adverse effect on the durability level of a packaging film. Studies of the rates of loss of water and sodium hydroxide from the viscose during coagulation revealed that thermal and osmotic effects were not as important in determining the rate of coagulation as was the buffering and neutralizing capacity of the bath. A bath with high acid content caused the cellulose to be regenerated prior to collapse of the sheet.
Odor control performance of carbon‐loaded rayon monofilaments
Authors: Turk Amos , Berlin Alvin
Published: April 2003

The odor control performance of carbon‐loaded rayon monofilaments depends on the type and proportion of activated carbon used. The filter efficiency in turn determines the rate of odor reduction in a closed space and the ultimate or equilibrium concentration when odorant generation and removal occur simultaneously. Four types of filters were evaluated: rayon loaded with air‐ or water‐purification carbon, granular air‐purification carbon, and open‐lattice commercial filters. Air laden with synthetic tobacco malodor was streamed through successive increments of adsorbent bed. Sensory odor judgments were made before and after each adsorption stage by matching the effluent odors with those from mixtures of known concentrations. It was thus possible to estimate adsorption efficiencies and, by repeating the measurements after various degrees of carbon saturation, to construct adsorption waves. It was found that airpurification carbon was superior to water‐purification carbon for loading in the rayon filaments, and that all the rayon‐carbon compositions were much superior to the commercial open‐lattice filters. The rayon‐carbon filters showed efficiencies up to 70% for one pass at 0.1 sec. detention time through a 3/4‐in. bed packed at 0.096 g./ml. with a filament comprising 20% rayon and 80% carbon.
Thermally reversible gels from carbonyl‐containing water‐soluble synthetic polymers
Authors: Jones Giffin D.
Published: April 2003

The reversible reaction with di‐hydrazides in acidic solution or polyamines in alkaline solution is used to cause synthetic polymers containing labile carbonyl groups to gel with sharp thermoreversibility in dilute water solution. Some of the polymers described contain active methylenes, for example, partially acetoacetylated polyvinyl alcohol and polyethylenimine, and copolymer of allyl acetoacetate with acrylamide. These polymers function also as couplers for azo and azomethine dye formation.
Chlorinated and chlorosulfonated polyolefins
Authors: Canterino P. J. , Kahle G. R.
Published: April 2003

The properties of chlorinated and chlorosulfonated ethylene polymers and copolymers have been examined. The effect of such variables as polymer chain structure, molecular weight, degree of chlorination, and chlorination conditions was studied. A variation in physical properties of different polyolefins chlorinated to the same degree is attributed to differences in residual crystallinity in the chlorinated product. Chlorinated linear polyethylenes are more crystalline than chlorinated branched polyethylene and are semicrystalline, flexible plastics in the 15–35 wt. % range. The chlorinated branched polyethylenes of this chlorine content are soft and rubbery. Chlorination conditions can influence the degree of residual crystallinity in the chlorinated product, and hence have a pronounced effect on the properties of the products Molecular weight of the polymer and degree of chlorination influence the properties of the chlorinated product. Chlorosulfonated linear ethylene polymers and copolymers were tested as elastomers. Stress‐strain properties were better for the chlorosulfonated linear copolymers as compared to chlorosulfonated linear polyethylene or branched polyethylene. Poor residual elongation was characteristic of the chlorosulfonated linear polymers. An increase in the number of side groups in the basic polymer chain did not affect residual elongation.
Effect of catalytic aging reactions on mechanical and solubility properties of films derived from neopentyl adipate polyesters and toluene diisocyanate
Authors: Cinadr Bernard F. , Bobalek G.
Published: April 2003

Although the necessary conditions are known for formation of tough films from polyurethane intermediates, the chemistry is too complex to allow certain predictions of how variances in the polymerization process effect molecular structure and polymer properties. This research examined the hope that a correlated study of solubility and mechanical behaviors might show the effect of different catalysts and environments on crosslinking or other structural features which can modify film quality. Films (0.01 in. thick) were cast on mercury of intermediates derived from reaction in solvent of 2 moles of diisocyanate per mole of hydroxyl terminated polyesters, catalysts like N‐methylmorpholine, methyldiethanolamine, and cobalt and/or lead ions being used to promote film‐forming reactions. The films, when dry, were aged at different levels of temperature and humidity. The solubility behavior was rated by measuring swelling ratios, rates of extraction, and intrinsic viscosity of extracts. Mechanical properties were rated by measuring tensile and stress relaxation behavior. The stress‐induced microstructure and fracture process were observed microscopically in a few typical specimens. The data support the theory that hydrogen bonding provides a strong crosslinking mechanism which dominates even the effects of moderate covalent crosslinking. Polymers derived from the same intermediates show very similar mechanical properties, even though significant differences in solubility properties suggest variances in other details of molecular structure.
The extraction of admixed polymers from natural rubber vulcanizates
Authors: Cooper W. , Smith R. K.
Published: April 2003

Extraction by solvent of admixed polymethyl methacrylate or polystyrene from natural rubber vulcanizates is dependent on the crosslink density, the solvent, the molecular weight of the polymer, and the size of sample extracted. High molecular weight polymer is extracted very slowly, and in some cases several weeks of continuous extraction have been found necessary. The rate of extraction is increased, as would be expected, by solvents which swell the rubber strongly, and by increase in temperature of extraction. In some cases the vulcanization procedure degrades the polymer, while in others there is a possibility of cocrosslinking the rubber and polymer. Graft copolymers from rubber and methylmethacrylate or styrene possess similar characteristics when vulcanized. In consequence, analysis of the content of free homopolymer is subject to considerable uncertainty. In the analysis of these rubber–polystyrene mixtures by ozonolysis, polystyrene was found to be very susceptible to attack by ozone.
The different states of polymers based on their thermomechanical properties
Authors: Chatain M. , Dubois P.
Published: April 2003

The different transition points which characterize eventually the three solid, plasto‐elastic and rubbery states have been determined by several methods. The authors show nevertheless that good data can be obtained using very simple traction experiments, at different temperatures. These experiments were carried out in different conditions of mechanical strain and temperature; the corresponding characteristics of breaking load and flow strain were noticed. Thus thermomechanical diagrams were obtained, either of the breaking load either flow strain, in function of the temperature for the most important classes of polymers: thermoset, thermoplastics, including crystalline linear and regular polymers, linear irregular polymers and crosslinked polymers. These diagrams give an indication on the limiting strains from which the use must be excluded taking into account flow straining at a given temperature. These diagrams make also more precise the transition points determined at given mechanical strains, of which the effect is important on the temperature where they occur. It is interesting to notice the increasing thermosensitivity of the method for the multibranched, crosslinked, irregular and regular polymers.
Dynamic mechanical spectra and limit of linear viscoelasticity of high polmers
Authors: Maxwell Bryce , Guimon Claude
Published: April 2003

The dynamic mechanical properties of a typical polycrystalline polymer (polyethylene) and a typical glassy state amorphous polymer (polystyrene) have been studied as a function of both frequency and temperature. The response of these materials to mechanical loading was found to be dependent upon the magnitude of strain resulting from the mechanical load above the limit of linear viscoelastic response. Therefore, the limit of linear viscoelastic response must be considered as an important material characteristic in design application of high polymers. This limit has been studied as a function of time scale of loading and polymer structure for a series of materials. A general trend of increased strain limit of linear viscoelastic response with increased heterogeneity of internal structure has been found.
Structural adhesives—characteristics and application
Authors: De Lollis Nicholas J.
Published: April 2003

Structural adhesives are one of the more important developments in the adhesives field because they make possible bonded assemblies in lightweight structures which take full advantage of the strengths of the materials used. Structural adhesives can be divided into two classes. One class consists of hard brittle resins typified by unmodified epoxy adhesives which have high shear and tensile strengths but low peel strength. The second class consists of a combination of resins resulting in a more ductile type of adhesive which has high peel strength along with high shear and tensile strength. One application is described here in which an epoxy adhesive is used in a design which minimizes peel forces and which causes failure of the bonded assembly in the metal. The evaluation of this design showed it to be successful.
Importance of evaluation of adhesives for all environmental conditions and permanence studies
Authors: Blomquist Richard F.
Published: April 2003

Although considerable research has been conducted to establish the performance of various adhesives under different conditions of service, much remains to be done. Of great importance are basic studies of the mechanisms of deterioration of adhesives in joints under known conditions so that reliable short‐term performance tests may be devised to determine the expected performance of adhesives under various service conditions. Such research needs will undoubtedly be increased in importance by the continued introduction of new adhesives of different chemical types. In all probability, the nature of the adherend influences not only initial adhesion but also subsequent joint performance. Most experience reported here on permanence of joints has been gained with wood, but research on metal adhesives is also reviewed.
Solvent‐resistant rubbers obtained by the use of metallic soaps
Authors: Korb Juan
Published: April 2003

At present, solvent‐resistant rubbers are obtained only by the introduction of polar groups in the polymer chain. These groups impair some physical properties of the rubber. A new way is suggested for obtaining solvent‐resistant rubbers by using nonpolar elastomers compounded with metallic soaps. These soaps can be considered polymeric materials, whose long chains are built up by weak coordinate bonds, which can be easily broken and reformed in contact with solvents. In this way a layer of solvent‐swollen soap is formed over the soap‐compounded vulcanizate, which prevents further attack. An explanation of the above behavior is given on the basis of the crystallization tendency of the metallic soap.
Basic design features of a nonimpacting, pneumatically driven, hydraulically damped high speed tester
Authors: Spangler R. D.
Published: April 2003

The significance of the time to acquire constant velocity in high speed testing is discussed. It is pointed out that the border line between impact and nonimpact testing depends on this time as well as the length of the test specimen and the velocity of sound in the material being tested. Equations relating force, mass, velocity, damping, and time are worked out for a pneumatically driven, hydraulically damped piston‐type machine. These equations afford a basis for the design of a high speed tester. Practical values of parameters are given for a machine which will acquire a uniform velocity of 50 ft./sec. in about 3 × 10−4 sec. Design data for a damping system are also given.
High speed measurements of dry adhesion as related to the friction and abrasion of elastomers
Authors: Vickers H. H.
Published: April 2003

Studies of friction and abrasion of elastomers have indicated that static friction or adhesion may be one of the important parameters in the traction and wear obtained with automobile tires. In this case static friction is considered to exist where a point of contact, adhesive attachment, or an interlocking is made between the rolling tire and the road which is strong enough to hold and transfer energy from one surface to the other. To investigate the magnitude of adhesion between tire tread rubber and the road, a test was developed that would measure the dry adhesion of rubber to other materials at break‐away speeds above the recovery rate of the rubber. By using clean dry surfaces and break‐away speeds of 2000 in./min., adhesive values in the order of 100 psi were measured with butyl tread stocks against impact styrene or against a rough stone surface. Much lower values were obtained for SBR and natural rubber. The influence of surface contamination, break‐away velocity, and hysteresis was also studied. The equipment used and the procedures for these tests are described in this paper.
Investigations of the phenomena of coacervation. Part II. Coacervation of polyethylene terephthalate
Authors: Turska E. , Utracki L.
Published: April 2003

Investigations are reported for the influence of temperature, initial polymer concentration, and solvent composition on the course and character of the phenomenon of a division into two liquid phases of the system polyethylene terephthalate–phenol–tetrachloroethane–n‐heptane. Some curves presented show changes in volumes of the phases in polymer content in phases, and in binodials of the liquid phases (Gibbs triangles). The term “coacervate” is suggested for the phase in which concentration of polymers during titration with nonsolvent is greater than that in the balancing phase, and in which at the same time the polymer content changes from 0 to 100%. It is shown that such a division into two liquid phases can take place only when the straight line representing the changes of nonsolvent content intersects the binodial between the critical point of miscibility and the side of the triangle of Gibbs corresponding to the zero content of polymer.
Relationship of molecular structure and resin performance for a series of diglycidyl ethers
Authors: Kelly P. B. , Landua A. J. , Marshall C. D.
Published: April 2003

An investigation of the relationship between molecular structure and polymer performance has been made for a series of six diglycidyl ethers. The resins evaluated were those based on the bisphenols derived from methyl ethyl, methyl isobutyl, methyl n‐amyl, methyl n‐nonyl, methyl‐n‐heptadecyl and di‐n‐heptadecyl ketones. The first three members of this series gave performances close to those of the diglycidyl ether of p,p′‐bisphenol acetone. The long chain members of the series showed poorer over‐all performance but did exhibit significant hydrophobic character in the cured specimens. The cured diglycidyl ethers showed variation attributed to both length and configuration of the alkyl chain. An increase in length of straight chain resulted in lowered heat distortion temperature, hardness, shear strength, and organic solvent resistance. Branching in the alkyl chain imparts improved performance characteristics.
Effect of radiation of polyethylene on environmental stress cracking
Authors: Liebling Gerald , Barton Stephen , Ullman Robert
Published: April 2003

The influence of radiation on the environmental stress cracking of polyethylene is described. The polymer was irradiated by cobalt‐60 γ‐rays, and studied as a function of a variety of experimental conditions. The deleterious effects of oxygen were noted. To prevent oxidative deterioration, the free radicals created had to be terminated by a heat treatment in the absence of oxygen. Some procedures were developed in which polyethylene could be made resistant to environmental stress cracking.
Polyspiroacetal resins. Part II. Structure and properties of polyspiroacetals from pentaerythritol‐glutaraldehyde and from (pentaerythritol–dipentaerythritol)‐glutaraldehyde
Authors: Cohen S. M. , Hunt C. F. , Kass R. E. , Markhart A. H.
Published: April 2003

Polyspiroacetal polymers and copolymers derived from pentaerythritol, and glutaraldehyde were prepared and examined for physical properties. Elemental and infrared analyses support the polyspiroacetal structure. X‐ray analysis indicates a range of 20–40% crystallinity. Dipentaerythritol was observed to influence in varying degrees the crystallinity, the solubility, and the optimum range of film curing conditions. Resins with more than 25% dipentaerythritol always crosslinked during polymerization. In addition, the variables influencing such resin properties as molecular weight and gelation were examined. Films crosslinked with pyromellitic dianhydride exhibited good flexibility and tensile strength. Moreover, their oxidative thermal stability was only slightly less than that of crosslinked poly(ethylene terephthalate).
A theory of inclusions in viscoelastic materials
Authors: Radok J. R. M. , Tai Clement L.
Published: April 2003

Two important groups of viscoelastic materials may, in practical applications, be characterized by the presence of inclusions. In high polymers, the control of the production of homogeneous batches presents often unsurmountable difficulties and hence unintended regions of nonhomogeneity will result. In concrete structures, reinforcements are often introduced to ensure strength in tension, and these inclusions, while intentional, are bound to change the behavior of the bulk material. This investigation of the effects of circular cylindrical and spherical inclusions in infinite two‐ and three‐dimensional bodies, subject to uniaxial loading at infinity, has been based on linear viscoelastic theory. It has been assumed that the inclusions are either rigid, perfectly elastic or viscoelastic and that their boundaries are free or welded to the surrounding material. In all these cases, the behavior of the viscoelastic material surrounding the inclusions will differ essentially from that of the material without inclusions. For example, it may be shown that a single parameter material will exhibit several retardation or relaxation times. In view of this situation, the interpretation of experimental test results on viscoelastic materials as well as the practical usefulness of linear viscoelastic theory appear in a new light which is discussed on the basis of the available information.
Adhesion between viscoelastic and hard materials
Authors: Brunt N. A.
Published: April 2003

The steady of peeling off process of a resin layer from a hard substrate can be considered as a rate process, being greatly dependent on temperature. Formulae relating the rate of release, the temperature, and the load with the energy of adhesion and the number of contact points between resin layer and substrate are derived. In the experimental part the energy of adhesion is measured according to these formulae for a number of different combinations of the same resin with glass, glass after removal of the water layers ordinarily adsorbed on a glass surface, and stainless steel. In all these cases there is but very little difference between the real energies of adhesion. Of more importance are time and temperature of the curing of the resin.
Electrochemistry of poly(methyl vinyl ether‐maleic anhydride)‐polyvinyl alcohol membranes
Authors: Spencer H. G. , Hunt O. L.
Published: April 2003

The electrochemical properties of a series of baked poly(methyl vinyl ether‐maleic anhydride)‐polyvinyl alcohol membranes were investigated. Increased baking time and carboxylic acjd content reduced swelling and osmotic flow, and increased the concentration potentials. Near‐maximum concentration potentials were obtained for some membranes in a limited concentration range.
Non‐Newtonian flow of concentrated solutions of high polymers
Authors: Onogi Shigeharu , Kobayashi Tadashi , Kojima Yasuhiro , Taniguchi Yoshishige
Published: April 2003

Non‐Newtonian flow of moderately concentrated solutions of polyvinyl alcohol (PVA) in water and polystyrene (PS) in toluene were measured with a Maron‐Krieger‐Sisko viscometer at various temperatures and concentrations. The usual dependences of the apparent and zero shear viscosities for two polymers on rate of shear, temperature, and molecular weight have been found. The log‐log plot of zero‐shear viscosity versus concentration can be represented by two straight lines intersecting at one point (critical concentration cc). The critical concentration in volume fraction of polymer, v2c, multiplied by the chain length Z is not constant but decreases with decreasing Z, although it has the same order of magnitude as the value of Zcv2 obtained from the log‐log plots of viscosity versus Z for many systems of polar and nonpolar polymers. The product ccρZ1/2 (ρ = density of the solution) is constant and independent of Z. To explain the constancy of this product, an equivalent sphere model is presented. When the volume fraction of spheres is assumed to be unity, the extension of molecules agrees very well with the unperturbed extension evaluated from intrinsic viscosity data in ⊖ solvent.
Adhesiveness of polyethylene mixtures
Authors: Bikerman J. J. , Marshall David W.
Published: April 2003

The effect of additions to polyethylene wax on the breaking stress f of butt joints between two steel cylinders depended on the nature of the addition. Oleic acid lowered f in concentrations as small as 0.2%, and in presence of 1% oleic acid f was immeasurably small. Ethyl palmitate slightly diminished f (to about 1/5th of the initial value when the amounts of polyethylene and palmitate were equal), but this decrease was wholly due to the weakening of the polymer itself, and the ratio of f to the tensile strength of polyethylene‐palmitate mixtures was >1 at all compositions. Thus, with oleic acid above 0.2% improper, and with ethyl palmitate at all percentages, proper adhints were obtained. Stearone apparently formed a weak boundary layer and 4‐methyl‐2,6‐di‐tert‐butylphenol gave erratic results as it decomposed on heating and apparently reacted with steel. Addition of ethyl palmitate to polyethylene contaminated with oleic acid made the mixture adhesionable. The solubility of the contaminant in solid polyethylene was more important than polarity. The relation between the composition of an adhesive and the breaking stress of its adhints can be understood if the distinction between proper and improper joints is kept in mind.
Siloxy methylene oxide compounds
Authors: Ender H. H.
Published: April 2003

Silicon containing chain and ring formals of the structures
magnified image
were synthesized from the reaction of a chlorosilane with formaldehyde or a formaldehyde donor in acid solution or in the presence of an HCl acceptor. Mono‐, di‐, tri‐, and tetrafunctional “silyl formals” were obtained; they are oily products of various degrees of polymerization and of relatively high refractive index and specific gravity. Silyl formals are stable at room temperature. They are useful intermediates in cases in which a siloxy group should be introduced into an organic molecule by reaction with an organic OH group or active hydrogen. Tri‐ and tetrafunctional silyl formals are effective crosslinkers in various systems.
Crosslink formation during aging of natural rubber vulcanizates
Authors: Maisey L. J. , Scanlan J.
Published: April 2003

The effect of antioxidant on the crosslinking reaction occurring during the oxidation of sulphur vulcanizates of natural rubber was investigated by using both continuous and intermittent stress relaxation measurements. Similarly, by means of continuous stress relaxation and equilibrium swelling measurements the crosslinking reaction in vacuum was followed. The presence of antioxidant or removal of air reduced considerably both continuous and intermittent relaxation and also the difference between them, which measures the crosslinking. The crosslink formation must therefore form part of the sequence of oxidative reactions.
The capillary flow of silicones
Authors: Johnson Donald L. , Baer Eric
Published: April 2003

The non‐Newtonian flow of silicone fluids in capillaries was investigated with special emphasis on the viscoelastic nature of entrance and exit effects. At low pressures the power law was obeyed, while at high pressures considerable deviations were observed, particularly with short capillaries. For capillaries with large length‐to‐radius ratios, the flow index and consistency approached the Newtonian values. Entrance effects were successfully analyzed by the method proposed by Bagley. At low shear stresses the end correction was dependent only on the geometry of the apparatus. An elastic contribution to the end correction was observed only at high shear stress, indicating a relatively mild viscoelastic behavior. Additional evidence indicating small elastic effects was obtained from swelling measurements of capillary jets.
Crosslinked polyesters from allyl glycidyl ether and maleic anhydride
Authors: Fischer R. F.
Published: April 2003

Allyl glycidyl ether and maleic anhydride, mixed in equimolar quantities, cure together readily in the presence of air, peroxide, and/or Lewis acids. Outstanding properties of the castings formed are hardness (Barcol 50–60 at 25°C., 30 at 150°C.), clarity and heat distortion temperature (165–168°C.). Color is yellow to amber, and strength properties are adequate. Water resistance is fair. The mixture is too thin for convenient use in laminating, but it can be bodied by heating (1 hr., 110°C.), giving a syrup of 50 cpoise. In glass cloth laminates, through‐cure appears to be inhibited by the glass. The addition of styrene overcomes this effect. Small amounts are best (5–20%), since large quantities impair elevated temperature strength. Unusually good strength is attained even at 500°F., but resistance to aging at 500°F. is poor.
Polymeric ligands. V. Derivatives of dimethylglyoxime
Authors: Degeiso R. C. , Donaruma L. G. , Tomic E. A.
Published: April 2003

Monomethacrylyldimethylglyoxime and dimethacrylyldimethylglyoxime were prepared by acylation of dimethylglyoxime with methacrylyl chloride. Monoallyldimethylglyoxime and diglycidyldimethylglyoxime were prepared by alkylation of dimethylglyoxime sodium salt with allyl bromide and epichlorohydrin, respectively. The monomethacrylyl derivative formed a copolymer with methyl methacrylate and the dimethacrylyl derivative yielded a homopolymer. Nickel chelates could be formed from both polymers. Diglycidyldimethylglyoxime was easily copolymerized with a number of diamines. A polymer formed as a by‐product from the preparation of the diglycidyldioxime was easily cured with m‐phenylenediamine.
The effect of extraction and rubber purity on the stress relaxation of dicumyl peroxide vulcanizates
Authors: Dunn J. R.
Published: April 2003

The oxidative stress relaxation of peroxide vulcanizates of various grades of natural rubber has been investigated at 100°C. The rubbers were examined both with and without hot acetone extraction before or after cure. Highly purified rubber vulcanizates exhibited autocatalytic relaxation, but those based on crêpe or smoked sheet did not, because they retained natural antioxidant even after extraction. Autocatalysis was no longer found in extracted purified rubber vulcanizates if these were prepared from a mix containing phenyl‐β‐naphthylamine. The presence of such an antioxidant reduced network scission but had less effect upon the amount of crosslinking taking place during aging.
Permeation rate constants for water and salt flux through synthetic membranes
Authors: Skiens W. E. , Mahon H. I.
Published: April 2003

Water and salt fluxes through synthetic membranes were measured as functions of pressure. In the pressure range 0–60 atm. both the water permeation rate constant and the salt permeation rate constant were independent of pressure. The water flux increased linearly with pressure driving force (hydraulic‐osmotic). The changes in salt flux were small. These changes were proportional to changes in the activity of the salt solutions due to concentration and pressure effects. Good agreement was obtained between the experimental flux data and the kinetic equations describing the process.
A contribution to the theory of periodate oxidation of starch
Authors: Mejzler D. , Schmorak J. , Lewin M.
Published: April 2003

The mathematical theory of periodate oxidation of unfractionated starches was studied. The degrees of polymerization (DP) of the amylose and amylopectin components of the starch were considered to be unknown, whereas the proportion of amylose in the starch, the repeating chain length of the amylopectin component, and the amount of formic acid evolved on quantitative oxidation were considered to be experimentally ascertainable and thus known. The treatment thus reduces to an approximate solution of one equation with two unknowns. It is shown that certain inequalities are then valid, when the following information can be obtained: (1) the upper and lower DP limits of each component, (2) the extent of degradation of a randomly degraded starch, and (3) the maximum relative errors involved in the determination of the DPs of the components by the periodate method. A numerical example is given to show the application of the method in laboratory practice.
Effect of addition of cations on the simultaneous grafting of styrene to rayon by gamma–irradiation
Authors: Suzuki Ikuo , Ogawa Seiji
Published: April 2003

Simultaneous radiation grafting of styrene to rayon in the presence of atmospheric oxygen was accelerated when the rayon was immersed in an aqueous solution of some reducing cation. The irradiation time required for the same amount of grafting as in the case of no addition of salt is reduced by 40 min. or more on the addition of TiCl3, SnCl2, SnCl4, NiCl2, CrCl3, or CoCl2, while FeCl2 has little effect on acceleration. This acceleration is chiefly due to the decrease in the induction period caused by the oxygen in polymer phase. The mechanism of acceleration of grafting is discussed in relation to radiolysis of aqueous solution involving cation.
Polyhydroxyethers. III. Ester derivatives
Authors: Reinking N. H. , Barnabeo A. E. , Hale W. F. , Mason J. H.
Published: April 2003

The esterification of high molecular weight hydroxyether polymers, derived from dihydric phenols and epichlorohydrin, has been studied. The esters of an assortment of monobasic acids, both organic and inorganic, were prepared by reaction of acid halides, anhydrides, esters or free acids with the secondary hydroxyl group in the polymer repeating unit. The effects of the structure of the acid radical and the degree of esterification on polymer properties were determined. In general, esterification resulted in a lowering of the major glass transition temperature of the polymer. This was true at all levels of esterification. Decreased chain symmetry and decreased hydrogen bonding appeared to be the major causes of the observed effect. Permeability of the polymers to oxygen and water vapor was increased by esterification. The increases was found to correlate well with the size and polarity of the acid radical. Some additional properties of the ester derivatives were examined in less detail.
Colorimetric method for measuring polyester degradation due to weathering
Authors: Gray V. E. , Wright J. R.
Published: April 2003

Chemical changes occurring in thermoset polyesters during exposure to solar and carbon‐arc radiant energy were determined quantitatively by a color reaction with a diamine, N,N‐dimethyl‐p‐phenylenediamine, in a methanol–benzene solution. The amount of diamine reacting with a specimen and the color change of the treated specimen, as measured by differential reflectance, varied directly with exposure time. Three commercial polyesters (glass fiber‐reinforced) exposed under identical conditions showed widely different degradation rates as measured by the amount of N,N‐dimethyl‐p‐phenylenediamine used per specimen. The relative stability of the three materials was independent of irradiation source. The color of the treated specimen was dependent on exposure time.
Polymer structure and gas permeation. I. Thermodynamic interpretation of permeation
Authors: Roberts R. W. , Kammermeyer Karl
Published: April 2003

A thermodynamic interpretation of the permeation process of gas transport through polymeric membranes is proposed. The mechanism used does not require the usual P = DS relationship. The dependence of gas permeability upon the crystallinity, strain, etc. is presented, and a method for obtaining values for the entropy of crystallization is suggested. Literature data have been correlated by this approach and values for the entropy of crystallization of polyethylene, polyethylene terephthalate, and nylon 610 were derived.
Tensile strength of gum and reinforced EPR and SBR vulcanizates
Authors: Dudek T. J. , Bueche F.
Published: April 2003

The tensile strength and elongation at break of EPR and SBR gum vulcanizates were determined as a function of network chain density. A large viscous contribution to the tensile force was found at low crosslink density, and the maximum in the tensile strength versus chain density curve decreased as more nearly equilibrium conditions were approached. The rate dependence of tensile strength of black‐filled EPR was studied by creep rupture experiments. The temperature dependence of the tensile strength of filled EPR and SBR was studied and compared. The same limiting degree of cure was obtained for both filled and gum vulcanizates of EPR.
Effect of homogeneity on viscosity in capillary extrusion of polyethylene
Authors: Heitmiller R. F. , Naar R. Z. , Zabusky H. H.
Published: April 2003

The change in melt flow properties, as determined by melt index measurement, as a function of shear history, has been measured for linear polyethylene. It is shown that a drop in melt index occurs when a polymer sample which has had no previous shear history is melted and subjected to shear mixing. This fact is attributed to a molecular homogenization of a previously unmixed blend. An analytical model of the laminar flow in a pipe of concentric adjacent fluids with different viscosities is presented. The model indicates that the effective viscosity of this non‐homogeneous system is much lower than the viscosity of fan intimate blend of the same viscosity of an intimate blend of the same viscosity fluids.
Oxyluminescence of polymers. I. General behavior of polymers
Authors: Schard M. P. , Russell C. A.
Published: April 2003

The faint emission of light by various classes and types of polymers when heated in the presence of oxygen, oxyluminescence, was studied by means of a photomultiplier tube and sensitive microammeter. Among the polymers with a carbon‐carbon backbone, the polymers having the greater number of tertiary carbon atoms generally showed greater intensities of luminosity. Polystyrene was a notable exception to this generalization. The shape of the luminosity versus time curves varied with the type of polymer. It was also found that the emission of light did not stop instantly when the oxygen atmosphere was replaced by an inert gas, but rather followed an exponential type of decay. The rate of decay appeared to be different with different types of polymers. The intensities of luminescence and the times required to reach maximum or steady state luminescence were compared with oxygen uptake data for various polymers. In general there was a qualitative, but not necessarily quantitative correlation between the luminous intensities and polymer stabilities in the presence of oxygen.