bluuebunny/crossref_metadata_2025 huggingface dataset:
The study of cracking and fracturing of spherulitic isotactic polypropylene
Authors: Barish Leo
Published: April 2003

Isotactic polypropylene was melted and crystallized at 125°C. Crystallization was observed dynamically on a microscopic heating stage. Spherulites, when first formed, appear to have a lower order of birefringence than after some growth. Between 4–4.5 min. of crystallization cracking occurs between spherulitic boundaries. In a parallel experiment samples crystallized at 125°C. were quenched after different degrees of spherulization. The effect of degree of spherulization on stress‐strain properties was studied and the necks and fractures of the samples studied. The completely spherulitic samples broke abruptly at spherulitic boundaries without necking. The rate of elongation affected the nature of the fracture of completely spherulitic samples. At low rates of elongation the spherulites have a tendency to “pull out” at the fracture. At high rates of elongation the spherulites break more sharply at their boundaries.
Swelling of filler‐reinforced vulcanizates
Authors: Kraus Gerard
Published: April 2003

A theory is developed to account for the restricted swelling in solvents of crosslinked elastomers containing reinforcing fillers. Assuming swelling to be completely restricted at the filler‐rubber interface due to adhesion, the following relation is obtained:

where vr is the volume fraction of rubber in the swollen rubber phase, Vro is the same quantity referred to on otherwise analogous, unfilled vulcanizate, Φ is the volume fraction of filler, and c a parameter depending on the filler, but independent of Φ and Vro. This equation is shown to hold for a large volume of experimental data on carbon blacks, involving four rubbers, several sulfur vulcanizing systems, five solvents, and a wide range of crosslinking. Conformance with the theory indicates that carbon blacks are firmly bonded to the rubber and that, in the sulfur crosslinking systems investigated, they have no significant effect on the stoichiometry of vulcanization (although they may affect the rate of vulcanization). Illustrative examples of applications of the theory to problems in filler reinforcement and vulcanization are shown.
Dynamic properties of heat‐treated butyl vulcanizates
Authors: Payne A. R.
Published: April 2003

Heat treatment of butyl rubber containing carbon black can considerably reduce “structure effects” in the dynamic properties of the vulcanizate, although swelling measurements indicate that G ∞ the shear modulus at very high amplitudes is unaltered. This paper compares the G′, G″ and phase angle δ changes that occur with the amplitude of oscillation for both a normal butyl rubber containing HAF black and a vulcanizate of the same composition but which has been subjected to an additional heat‐treatment process with N‐methyl‐N, 4‐dinitrosoanaline.
Orientation in cold‐rolled polypropylene
Authors: Wilchinsky Zigmond W.
Published: April 2003

Sheets of isotactic polypropylene were prepared to have initially random orientation and were subsequently rolled at temperatures below the crystalline melting point. Their crystal orientation was investigated. The orientation of the c axis (fiber axis) was determined from pole figure data obtained by x‐ray diffraction. It was found that rolling produced orientation of the c axis in two preferred directions in the plane defined by the rolling direction and the normal to the sheet. These two directions made equal angles of inclination with the rolling direction. With increased severity of rolling the component of the orientation vector in the rolling direction increased and the angles between the preferred c axis orientation and the rolling direction decreased. Increasing the temperature reduced the angle of inclination of the preferred c axis orientation. This double c axis orientation was not observed in extruded film. An explanation of the c axis orientation in cold‐rolled polypropylene is offered on the basis of local necking down within the sample during the deformation.
The fine structure of fibers and crystalline polymers. III. Interpretation of the mechanical properties of fibers
Authors: Hearle J. W. S.
Published: April 2003

The mechanics of extension of plant fibers is considered in terms of a spiral arrangement of crystalline fibrils embedded in a noncrystalline matrix. Deformation may take place either by stretching of the fibrils or by extension such as that of a spiral spring. In the latter, the major resistance comes from the reduction in volume. The extension mechanism predominates for low spiral angles; the spring mechanism, for high spiral angles. There is reasonable agreement between the theoretical expressions and experimental results. The application of similar ideas to other types of fiber structure is considered.
Melting temperatures and polymer–solvent interaction for polycaprolactam
Authors: Gechele G. B. , Crescentini L.
Published: April 2003

Melting points of four polycaprolactam samples of different molecular weight and their mixtures with various diluents were determined. Heats of fusion and polymer–diluent energy of mixing parameters were calculated according to the theory of Flory. The heats of fusion were found to be about 38 cal./g. The experimental results (independence from molecular weight above a certain value, and from the nature of terminal groups, etc.) agree with the theory. However, in a few cases of poor solvents anomalous behavior can be suspected.
The action of epichlorohydrin in the presence of alkalies and various salts on the crease recovery of cotton
Authors: McKelvey John B. , Benerito Ruth R. , Berni Ralph J. , Burgis Beverly G.
Published: April 2003

As a phase of an investigation of the cellulose–epoxide reactions, experiments have been performed in which epichlorohydrin reacted with cotton cellulose in the presence of sodium hydroxide and various salts. Acidic and basic salts, as well as those which are relatively neutral in aqueous solutions, were used in pretreatments for the cellulose–epichlorohydrin reaction. No reaction with cellulose occurred in the presence of acid salts and only very slow addition of epichlorohydrin to cellulose in the presence of neutral salts; the greatest reaction was produced with basic salts. Particular emphasis was given to use of certain salts known to cause epichlorohydrin to undergo a type of cyclization reaction. Previously published methods, used for imparting both wet and dry crease resistance to cotton fabrics by means of diepoxides in the presence of NaOH, have resulted in wet crease resistance only when applied to the application of epichlorohydrin. Among the basic salts investigated, 20% solutions of sodium azide used in pretreatments were found to produce low weight gains of epichlorohydrin and a fair degree of dry and wet crease resistance in cotton after a slow reaction at 25°C. or a faster reaction at 80°C. The greatest improvement in dry crease resistance with epichlorohydrin was obtained by pretreatments with concentrated solutions of sodium orthosilicate, sodium metasilicate, or trisodium phosphate at 80°C. The effects of amount of water at time of reaction as well as speeds of reaction with the various pretreatments have been considered. Optical and electron microscopical examinations of fibers and ultrathin cross sections of fibers, respectively, after immersion in cupriethylene diamine (cuene) have indicated that the cellulose–epichlorohydrin reaction at 80°C. after pretreatment with concentrated solutions of silicates or phosphates differed from that after pretreatment with sodium hydroxide at all concentrations. Even when the pretreatments were with dilute sodium hydroxide, the epichlorohydrin‐reacted fibers were more swollen in cuene than were those treated fibers which had been pretreated with the concentrated silicates or trisodium phosphate solutions. Decrease in amount of swelling and dissolution in cuene was found to correlate with increase in dry crease resistance of the fabrics. While all these treated fabrics possessed high wet crease resistance, only those pretreated with the aforementioned concentrated salt solutions possessed good dry crease resistance. Effects of base‐catalyzed addition of certain monoepoxides to cotton on the resultant crease resistance properties of the fabrics have been reported and compared with properties imparted by epichlorohydrin. Attempts have been made to explain why the number of cellulose crosslinks formed per unit of time by epichlorohydrin is greater, when silicates or phosphates at high concentrations are present with hydroxyl ions, than when hydroxyl ions only are present.
Crosslinking efficiencies of dicumyl peroxide in unsaturated synthetic rubbers
Authors: Loan L. D.
Published: April 2003

The crosslinking efficiencies of dicumyl peroxide in SBR, cis‐polybutadiene, acrylonitrile–butadiene rubber, and polychloroprene have been measured. For the first two rubbers approximately ten crosslinks are formed per molecule of peroxide decomposed, while for the acrylonitrile–butadiene rubber an efficiency close to unity is found. With polychloroprene approximately two molecules of peroxide are used for each crosslink formed. Analysis of the low molecular weight products of the reaction shows that ease of hydrogen abstraction by cumyloxy radicals decreases in the order given above.
Polymerization activity test for methyl methacrylate
Authors: Georgieff K. K.
Published: April 2003

Two activity (polymerization) tests have been developed for evaluating the purity of methyl methacrylate industrially. A 10‐ml. portion of monomer is heated with 0.0400 g. of benzoyl peroxide in a test tube immersed in a bath at 101.2°C., until a spontaneous boil occurs. The effect of temperature, catalyst concentration, oxygen, barometric pressure, and weighing errors on the reproducibility of the test were studied. The inhibition factors for divinylacetylene, hydroquinone, p‐tert‐butylcatechol, and diphenylamine were determined. A second test in which 20 g. of monomer and 0.400 g. of benzoyl peroxide are brought to a spontaneous boil in a round‐bottomed flask heated with a Glass‐Col mantle was also developed. However, the sensitivity of this test to inhibitors and stabilizers was much lower than that of the test tube test.
Network characterization from stress–strain behavior at large extensions
Authors: Morris M. C.
Published: April 2003

The stress–strain properties of natural rubber and synthetic cis‐polyisoprene vulcanizates have been investigated over a large range of extensions. The results are in qualitative agreement with those of Mullins, in that the upturn of a Mooney‐Rivlin plot is ascribed to finite extensibility effects. It is further found that the stress–strain curves can be adequately described by a modification of existing non‐Gaussian theory. Analysis of the curves shows significant finite extensibility effects even at extensions well below the upturn. Thus, division of stress–strain curves into Gaussian and non‐Gaussian regions is to be avoided. Values for n, the number of statistical segments between crosslinks, were calculated using the proposed treatment. The values of n found were relatively unaffected by temperature. Further, the molecular weight of a statistical segment was found to be about the same for synthetic cis‐polyisoprene as for natural rubber despite differences in the crystallization behavior. Crystallization effects are therefore thought to be of little importance in determining the position of the upturn. The equivalent statistical segment was found to be 4.3 isoprene units for natural rubber and cis‐polyisoprene.
Noncorrosive nitrile elastomers
Authors: Trexler H. E. , Ilkka G. A. , Weiss P.
Published: April 2003

The corrosion of steel by nitrile elastomer oil seals prompted a laboratory study of the corrosivity of numerous compounding ingredients and nitrile polymers. Groups of materials studied in this investigation were plasticizers, antioxidants, black fillers, nonblack fillers, curing systems, and base polymers. A corrosion test procedure utilizing a benchtype corrosion chamber was developed, and a corrosion rating system was established. All materials were rated according to their corrosivity under conditions of 100% R. H., and 100°F. for 96 hr. From these data it was possible to formulate several noncorrosive seal compounds without the use of corrosion inhibitors.
Steric effects in the preparation and saponification of some fibrous cellulose esters
Authors: Stanonis David J. , King Walter D.
Published: April 2003

Two reaction paths which can be followed when an acid chloride reacts with an alcohol are discussed. The role of pyridine as solvent and catalyst in this reaction is described. The importance of inductive and resonance effects and the size and arrangement of groups near the carbonyl are emphasized. The heterogeneous preparations of seven cellulose partial esters, the phenylacetate, benzoate, trimethylacetate, triphenylacetate, β,β,β‐triphenylpropionate, α‐(4‐biphenylyl)phenylacetate, and mesitoate are described. Pronounced interference with esterification is noted only in the preparation of the triphenylacetate. Steric hindrance and a poor ability to ionize are considered to be responsible for this result. Outstanding resistance to saponification, thought to be the result of steric hindrance and a reduced tendency to ionize, is reported for three of the cellulose esters, the triphenylacetate, the β,β,β‐triphenylpropionate, and the mesitoate.
Kinetic observations of the quaternization of poly(ar‐vinylbenzyl chloride) with trimethylamine
Authors: Lloyd W. G. , Durocher T. E.
Published: April 2003

The quaternization of poly(ar‐vinylbenzyl chloride) with trimethylamine is shown to be a nucleophilic displacement reaction, the kinetics of which are complicated by several factors, notably differences in the reactivities of o‐ and p‐chloromethyl groups (position isomerism), differences in the reactivities of groups as a function of the reacted or unreacted status of immediately adjacent groups (neighboring group effect), and differences in the reactivities of groups arising from the microtacticity of the polymer segment (configurational effects). Estimates of mean rate constants, activation energies, and preexponential factors are given for high purity poly‐p‐vinylbenzyl chloride and for the analogous ortho polymer.
High temperature oxidative degradation of phenol–formaldehyde polycondensates
Authors: Jackson William M. , Conley Robert T.
Published: April 2003

The degradation of phenol–formaldehyde polycondensates has been investigated at temperatures as high as 1000°C. By employing infrared spectrophotometric techniques and vapor‐phase chromatographic methods, as well as thermogravimetric and x‐ray analyses, it has been possible to examine the oxidation chemistry of this resin system. It has been found that the primary degradation route of phenol–formaldehyde polycondensates, regardless of whether the resin is exposed to elevated temperatures in air, argon, or nitrogen, is oxidation. At elevated temperatures, products are observed from thermal pyrolysis in addition to those from the oxidation path. However, throughout the temperature region studied, the oxidative degradation is always more pronounced. The mechanism of oxidation has been found to agree favorably with the proposals formulated earlier by Conley and Bieron. It is also possible to extend this mechanism to include the formation of graphitelike char. This extension is postulated on the simultaneous formation of the char and carbon monoxide. By infrared studies of the intermediate stages in char formation, the postulation that these products arise from quinone‐type intermediates is justified. In this study, it was found that phenolformaldehyde polycondensates of unusual thermal stability could be produced by high temperature postcuring. The comparison of the oxidation rates of the resin cured at low temperature and this material indicates greatly improved oxidative stability, as well as resistance to thermal pyrolysis. This undoubtedly is due to the complete crosslinking of the resin system.
Ion‐exchange membranes. Application to the treatment of natural rubber skim latex
Authors: Sethu S.
Published: April 2003

Ion‐exchange membranes have been successfully used in the electrodialysis and electrodecantation of natural rubber skim latex for the recovery of ammonia as well as rubber. Diffusivity of the membrane and current efficiency were studied. An optimum condition is recommended for electrodecantation of skim latex.
Dynamic mechanical properties of several elastomers and their potentialities in vibration control applications
Authors: Yin T. P. , Pariser R.
Published: April 2003

The time–temperature‐dependent mechanical properties of Viton A, Neoprene ILA, Adiprene L‐167, and Nordel hydrocarbon elastomer have been measured primarily on the Fitzgerald transducer. The results cover the plastic to rubberlike transition regions which have been reduced to 25°C. whenever possible. The data are then discussed in terms of the relaxation spectra, monomeric friction coefficients and the shift factors, log QT. Following a brief presentation on the viscoelastic requirements for various vibration control devices, the potentialities of the present elastomers, as well as other common elastomers, are evaluated. It is found that Nordel, Hevea rubber, and Neoprene W are potential vibration isolators, whereas Viton A, Neoprene ILA, and polyisobutylene have desirable vibration damping characteristics. Their effective temperature‐frequency regions of application have been calculated.
Experiments on the effect of ethylamine treatment on the crystallinity of cellulose
Authors: Venkateswaran A. , Riemen W. P.
Published: April 2003

The results of the effect of ethylamine treatment on the crystallinity of cellulose under various conditions have been presented. The mode of removal of the swelling agent from cellulose is important in determining the amount of change in the lateral order structure of cellulose. It seems that the apparent change in crystallinity observed by ethylamine treatment is due to the swelling of cellulose, producing disorder only in the so‐called amorphous content of cellulose.
Radiation protection of polyethylene
Authors: Gardner J. B. , Harper B. G.
Published: April 2003

It is known that aromatic hydrocarbons are more stable to ionizing radiation than are saturated hydrocarbons. It is shown here that polyethylene can be more stable to radiation either by mixing aromatic compounds with the polyethylene or by grafting styrene onto the polyethylene. In either case, the polymer has greater radiation resistance than predicted from the law of averages. Aromatic compounds which have the greatest resonance energy protect the polymer to the greatest extent. In mixtures, polystyrene gives the least protection, and naphthalene, anthracene, and phenanthrene give the greatest protection. Polyethylene grafted with styrene has better radiation resistance than does a polyethylene‐polystyrene mixture. The G(H2) was calculated for each sample, and curves are presented illustrating the effect.
Polyacrylonitrile fiber behavior. I. Mechanisms of tensile response
Authors: Rosenbaum Shlomo
Published: April 2003

The behavior of polyacrylonitrile fibers has been studied by a number of methods over a wide range of temperatures. At the glass transition temperature Tg, in the vicinity of 100°C. by linear thermal expansion, creep, and dye sorption experiments, the break extension was found to rise abruptly, while an initial, stiff response disappeared. The tensile recovery as normally measured was incomplete at all temperatures; below Tg, however, all extensions were completely reversible when the kinetic conditions for retraction were provided. The main extension below Tg is attributed to the straightening of twisted molecules against the intramolecular repulsion of adjacent dipoles, the small initial extension up to the “yield” knee to an increase in volume required for the operation of the main response. The additional extension(s) above Tg appear(s) to involve permanent relative displacement of fiber elements. Water depressed Tg by 30–35°C.
Grafting of acrylate monomers in cotton fabrics
Authors: Negishi Michiharu , Nakamura Yoshio , Kakinuma Toshiko , Iizuka Yuriko
Published: April 2003

The graft copolymerization of acrylate monomers, methyl, ethyl, n‐propyl, and n‐ or isobutyl, in cotton fabrics was carried out in the aqueous emulsion system by the ceric ion method. The rate of grafting decreases with increasing length of the ester group. The maximum improvement of dry crease recovery, thus raising its value, increases with increasing graft‐on shifts towards the higher extents of grafting, and with decreasing second‐order transition temperature of graft polymer. The improvement of wet crease recovery, equilibrated in the presence of a wetting agent, is always greater than that in the dry crease recovery even when the hydrophobic propyl or butyl acrylate‐grafted cotton levels off with increasing graft‐on. The improvement of crease recovery was explained by the stabilization of the opened fiber structures by grafting with acrylates, especially those having bulky ester groups, the entangled crosslinking between the graft polymers or the graft polymers and cellulose chains, and the consequently developed elastomeric or swelling, elastomeric behaviors due to the segmental movements in the amorphous regions of graft copolymer. Furthermore, from the measurements of water imbibition and repellency, moisture regains, tensile properties, stiffness, flex abrasion, and thermosetting properties, it has been concluded that the improvements of physical properties are remarkable in the propyl or butyl acrylate‐grafted cotton.
Barus effect in filled polymer melts
Authors: Newman Seymour , Trementozzi Quirino A.
Published: April 2003

The influence of fillers on the post‐extrusion swelling (Barus effect) of polymer melts is explored with the use of three model fillers in poly(styrene–acrylonitrile). The filler effect is shown to be more complex than simple dilution of the polymer. The role of such factors as melt rigidity, tendency toward plug flow, trapping of matrix in filler aggregates, and filler migration are considered.
Polyurethanes as cryogenic adhesives
Authors: Sandler Stanley R. , Berg Florence R.
Published: April 2003

Polyurethanes containing the polyether backbone were found to give superior adhesives at cryogenic temperatures as compared to epoxy resins. However, the adhesives showed poor performance at 250 and 400°F. The adhesives were prepared from 2,4‐toluene diisocyanate (TDI)‐terminated polyether polyols and cured with 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane (MOCA, du Pont). The addition of free TDI causes an increase in elevated temperature strength when an equivalent amount of MOCA was used.
Polarization‐optical investigation of normal and shear stresses in flow of polymers
Authors: Brizitsky V. I. , Vinogradov G. V. , Isaev A. I. , Podolsky Yu. Ya.
Published: April 2003

A method has been suggested for calculating the first difference of normal stresses characterizing the flow of polymers at high shear stresses. The calculations are based on the results of rheooptical measurements in a slit of rectangular cross section. It has been found, for several samples of high molecular weight polybutadienes and polyisoprenes, that the flow behavior of the representatives of the given polymer homologous series having different molecular weights is characterized by a general relationship between the first normal stress differences and the shear stresses in those cases where the polymers are characterized by narrow molecular weight distributions. It has also been established that the first normal stress difference sharply increases in the region of shear stresses which immediately precedes the spurt—a jumpwise increase of the flow rate at a certain critical value of shear stress; while for polymers of wide molecular weight distribution the increase of the normal stress difference in the region of high values of shear stresses is retarded. Equilibrium swell of the extrudate has been measured and the first normal stress difference determined by the rheo‐optical method has been found to agree satisfactorily with the values calculated from the swelling ratios according to theoretical models.
Studies on melt spinning. VI. Simulation of draw resonance using Newtonian and power law viscosities
Authors: Ishihara Hideaki , Kase Susumu
Published: April 2003

Draw resonance, a periodic variation of spin line diameter in unstable melt spinning, was measured for its wave form under 34 different spinning conditions for PET and PP. In and attempt to simulate the measured wave form, the equations of continuity and momentum for the isothermal melt spinning of power law fluids were solved for their limit cycle solutions expressed in the time variations in the cross‐sectional area at the take‐up. Power law exponent p and draw down ratio ψw uniquely define the solution. Theoretical curves were superposed on the experimental amplitude‐versus‐ψw diagram and oscillation period‐versus‐ψw diagram to assign p value to each experimental point. Excellent agreement between theory and experiment was obtained with PET in that p values were nearly independent of ψw and of the diagram used in the determination of the p value, amplitude diagram, or oscillation period diagram. Motion pictures (16mm) of the side profiles of the pulsing spinline showed good agreement with the theoretical side profiles constructed from the corresponding limit cycle solution. It was proposed that the stability of melt spinning has no direct equivalence to the spinnability of fluids.
Increase of gold–Teflon FEP joint strength by removal of deposited aluminum prior to gold deposition for electret applications
Authors: Roberts R. F. , Ryan F. W. , Schonhorn H. , Sessler G. M. , West J. E.
Published: April 2003

A new method is described for bonding gold to Teflon FEP, yielding high joint strength without affecting the electrical properties of the virgin polymer material. The method consists of depositing a 1000‐Å aluminum layer onto the Teflon by evaporation, removing it by washing the sample in dilute sodium hydroxide, followed by deposition of gold by evaporation. The tensile shear strength of this composite is in excess of 80 kg/cm2, approaching the cohesive strength of Teflon. The desirable electrical properties of Teflon FEP, as measured by isothermal charge decay and thermally stimulated currents methods, are preserved by this method. X‐Ray photoelectron (ESCA) spectra suggest that the modified wetting characteristics and enhanced joint strengths can be attributed in part to the existence of a thin layer of oxygen‐containing hydrocarbon material on the surface of aluminum‐treated Teflon FEP.
Permeabilities to salts and water of macrocyclic polyether–polyamide membranes
Authors: Shchori Ehud , Jagur‐Grodzinski Joseph
Published: April 2003

The polyether–polyamide (PC‐6) strongly absorbs sodium salts from their aqueous solutions. Membranes based on PC‐6 and on its polymeric alloys with poly(vinylpyrrolidone) (PVP) are, however, much more permeable to water than to salts. The membrane permselectivity is due to the low mobility of the absorbed salts. Desorption experiments were conducted to determine the values of the diffusion coefficients of the sodium ions in the investigated membranes. They were found to vary from 5 × 10‐12 cm2/sec in loose PC‐6 membranes to 1.7 × 10‐9 cm2/sec in the polymeric alloy containing 30% PVP. Water permeation experiments with the alloy membranes yielded values of the diffusion coefficients in the range of 2–5 × 10‐7 cm2/sec. The apparent “energy of activation of the diffusion” of sodium ions in such membranes was found to be essentially indentical (∼12 kcal) with the energy of activation of the decomplexation of the sodium–“crown” complex. The ramifications of the proposed “site to site jump” diffusion mechanism were discussed. The permeability characteristics of PC‐6 membranes were found to be strongly affected by their “history.”. The observed phenomenon was explained in terms of reversible changes in the structure of the polymeric network, in the presence and in the absence of the absorbed salts. It has been found that PVP has a stabilizing effect on the permeability characteristics of the membranes. Reverse osmosis experiments indicated that their intrinsic osmotic characteristics seem to be superior to those of the commercially used materials. Their salt rejections are in the range of 95–99.5%, and their permeabilities to water are at least one order of magnitude higher than those of the unmodified aromatic polyamides.
Viscoelastic characterization of PVC plastisol melts for foam applications
Authors: Nakajima N. , Ward D. W. , Collins E. A.
Published: April 2003

Melt rheology and its time‐temperature dependence have long been known to be fundamental properties associated with satisfactory expansion characteristics in vinyl foam. Since much is known about the relationship between rheology and material variables like polymer morphology and system composition, adequate rheological characterization should be quite helpful in polymer design and plastisol compounding.

Earlier attempts to study the melt rheology of plasticized PVC foam systems were only partially successful because instrument limitations required that the material be studied at too high shear rate or temperature, or that behavior of specific compositions be extrapolated from data obtained at considerably higher plasticizer level.

This paper deals with measurement of the viscoelastic behavior of melts from actual azodicarbonamide foam compositions. The Rheometrics Mechanical Spectrometer was used in the orthogonal mode to study both elastic modulus and loss modulus (viscosity) in the range of shear rates and temperatures which actually occur during commercial utilization of PVC foam compounds. The effects of changing vinyl resin types and plasticizer types and levels were explored.
Pulse propagation in polyester–solvent systems
Authors: Weigmann H.‐D. , Ribnick A. S.
Published: April 2003

The propagation of sonic pulses through solvent‐swollen polyester yarns has been investigated. A discontinuity is observed in the temperature dependence of the pulse transit time which has been associated with the on set of the glass transition of the polyester–solvent system. Good agreement is reached for several systems with an extrapolated zero shrinkage temperature obtained from dynamic shrinkage determination of the filament in the appropriate solvent. The agreement between the two methods suggests that an interaction parameter for the polyester–solvent system is measured which must ba associated with the onset of its glass transition.
A theory for the impact behavior of rate‐dependent padding materials
Authors: Cousins R. R.
Published: April 2003

A continuum theory is used to describe the rate‐dependent behavior of padding materials and is applied to predict the impact behavior of these materials when struck by flat or spherical impactors. Numerical results are given to show the effect of varying the material and geometric parameters. Some implications of the theory to practical situations are discussed.
Tough, transparent heat‐ and flame‐resistant thermoplastics via silicone block‐modified bisphenol fluorenone polycarbonate
Authors: Kambour R. P. , Corn J. E. , Miller S. , Niznik G. E.
Published: April 2003

Bisphenol fluorenone carbonate–dimethylsiloxane block polymers have been synthesized by interfacial condensation of phosgene with various mixtures of BPF‐endcapped silicone oligomers and free BPF or its monosodium salt. The multisequence block polymers described here contain 7% to 27% silicone consisting of blocks of number‐average degree of polymerization 10 to 40. Cast films are clear and colorless. Two glass temperatures are evident in each resin, one at about −100°C for the silicone microdomains and one at temperatures as high as 275°C for the polycarbonate matrix. While BPF polycarbonate is brittle, block polymers with as little as 10% silicone yield by shear deformation before breaking. Ultimate elongations are increased by preorientation at silicone contents above 15%. At temperatures far removed from BPF carbonate domain Tg's, both modulus and yield stress decrease with increasing silicone content, independent of block length, in a manner rationalized quantitatively by hard phase–soft phase continuum models. Ultimate tensile elongation, impact toughness, and plane strain stress intensity factors increase with silicone content, through a stress whitening mechanism. At higher silicone contents, shear deformation enhances tensile elongation and impact toughness. Heat distortion temperatures of 200°C or more are achieved. Flame resistance exceeds that of any known nonhalogenated resin. The resins are extrudable and injection moldable with only minor changes in color, transparency, and strength properties. Resins with 15% to 20% silicone can have a balance of properties that makes them attractive as tough, transparent heat‐ and flame‐ resistant engineering plastics.
The near‐infrared spectra of polymers
Authors: Crandall Elbert W. , Jagtap Ashvin N.
Published: April 2003

A series of step reaction polymers have been prepared and studied as melt films or in solution in the overtone region and the combination region of the near‐IR. Systems containing aryl rings show bands in the 2.13‐ to 2.16‐μm region which are not observed in those systems not having aryl rings. Polyester, polyamide, and urea‐formaldehyde polymers show carbonyl, hydroxyl, and NH overtones. Polyurethanes show only the intense band of NH, in the 2.0‐ to 2.1‐μm region. Ureaformaldehyde and polyamides show this same band. Relative band intensities were compared to the first overtone of CH which appears at 1.67–1.72 μm. In this way, polymers can be compared in a quantitative manner, both with respect to reaction conditions and effect of heat curing.
Diffusion with simultaneous reaction of reactive dyes in cellulose
Authors: Motomura Hiromi , Morita Zenzo
Published: April 2003

The theoretical equations which described the concentration profile of immobilized species of reactive dyes in the substrate were derived from the diffusion equation with the chemical reaction of first‐order or pseudofirst‐order. The theoretical profiles in the substrate described by the equations were discussed. The larger the diffusion coefficient D of active species and the smaller the reaction rate constant k, the deeper is the penetration of the immobilized and active species of reactive dyes into the substrate. The method of estimating D and k from the diffusion profiles of both species obtained by means of the method of the cylindrical cellophane film roll was described. The diffusion coefficients of the hydrolyzed species of C.I. Reactive Orange 1 and Red 1 were nearly constant in all the pH values examined. The concentration profiles of both the species of Orange 1 at pH 8.8 were identical with the theoretical ones; while the profiles of immobilized species of Red 1 at pH 10 and of Orange 1 at pH 12 agreed with the theoretical ones and those of active species did not because of the hydrolysis. The diffusion coefficients of active species of these dyes at these pH ranges were smaller than those of the hydrolyzed species.
Graft copolymers from thiolated starch and vinyl monomers
Authors: Trimnell D. , Stout E. I. , Doane W. M. , Russell C. R.
Published: April 2003

Thiol starches of degree of substitution (D.S.) 0.005–0.162 were prepared by displacing starch tosyloxy groups with xanthate and treating the resulting xanthate esters with either sodium hydroxide or sodium borohydride. Acrylonitrile, styrene, acrylamide, acrylic acid, and dimethylaminoethyl methacrylate were grafted onto the thiol starches with hydrogen peroxide as initiator. The peroxide caused both grafting of monomer and coupling of thiol groups to disulfide. Treating graft copolymers with sodium borohydride regenerated thiol groups from disulfide groups so that the grafting sequence could be repeated. By regenerating the thiol groups and repeating the grafting steps, high add‐on and high‐frequency starch graft copolymers were prepared. During four grafting sequences, acrylonitrile reacted with D.S. 0.162 thiol starch to give graft copolymers that contained increasing amounts of polyacrylonitrile (46.0–66.5%). Grafting frequency increased from 183 to 71 anhydroglucose units (AGU)/graft, while molecular weights of the grafted chains ranged between 20,000 and 25,200. The final product was hydrolyzed with potassium hydroxide solution to a copolymer, which absorbed up to 400 ml water per gram. Styrene was grafted onto thiol starch to give products containing 34.4–69.5% polystyrene with 986–3520 AGU/graft and having molecular weights of grafted chains between 276,000 and 364,000. Graft copolymers containing 48.9% polyacrylamide, 21.2% poly(acrylic acid), and 77.7% poly(2‐methacryloyloxyethyldimethylammonium acetate) were obtained under similar conditions.
Thermal properties of metal‐filled epoxies
Authors: Papanicolaou G. C. , Paipetis S. A. , Theocaris P. S.
Published: April 2003

Thermal expansion coefficients and glass transition temperatures for metal–epoxy composites were determined experimentally. Results were in fair agreement with existing theories when certain fundamental assumptions were fulfilled. The effects of filler content and particle size as well as of adhesion between matrix and filler particles were investigated. The latter, in particular, was found to be of cardinal importance for the properties examined in the present work.
High‐speed gel permeation chromatography. A study of operational variables
Authors: Mori Sadao
Published: April 2003

Systematic studies of operational variables affecting GPC separation using μ‐Styragel of nominal porosity 106, 105, 104, and 103 Å are reported. The dependences of (1) flow rate, (2) injection volume, and (3) concentration on elution volume (Ve), the theoretical plate number (N), and peak width at half‐height were examined. The values of Ve changed with changing (1), (2), and (3). The values of N were inversely proportional to the root of flow rate. The relation between sample load and N showed that lower concentration and larger injection volume were desirable for N than the opposite. The concentration dependence for high‐speed GPC was significantly higher than classical low‐speed GPC. The methods of minimizing the effects produced by the individual variables and the optimum operational conditions are discussed. Recommended operational conditions are as follows: flow rate, 1 to 2 ml/min; injection volume, 0.1 ml; sample concentration, below 0.4% (or if injection volume 0.5 ml, sample concentration below 0.1%).
Noble gas permeability of polymer films and coatings
Authors: Hammon H. George , Ernst Klaus , Newton John C.
Published: April 2003

Permeabilities of noble gases, particularly argon, krypton, and xenon, were measured through a number of polymer films and coatings. Extrapolation of the log of the permeation coefficient versus the square of the gas molecular diameter was used to estimate radon permeability. An equation has been developed that can predict permeability to these noble gases as a function of the base polymer structure of the coating.
Preparation and properties of polycarbodiimides
Authors: Alberino L. M. , Farrissey W. J. , Sayigh A. A. R.
Published: April 2003

A series of polycarbodiimides was prepared from isocyanates using 1‐phenyl‐3‐methyl‐2‐phospholene‐1 oxide as catalyst. The molecular weight of the series was varied by employing controlled amounts of phenyl isocyanate as a terminating agent. The resultant polymers showed improved processing over very high molecular weight unterminated polymer, while still maintaining good thermal stability and equivalent mechanical properties. A study of the viscoelastic properties of these polymers using modulus–temperature plots showed that the materials underwent a crosslinking reaction at elevated temperatures (200–250°C). These reactions could be explained on the basis of a model, diphenylarbodiimide, and most likely include the formation of carbodiimide dimers and trimers.
On the structure of concentrated cellulose acetate solutions
Authors: Kunst B. , Vajnaht Z.
Published: April 2003

The supermolecular structure of cellulose acetate membrane casting solutions was determined by measuring their rheological behavior. The method was applied to both clear and turbid casting solutions. The resulting data on activation energy of viscous flow are shown to depend on the cellulose acetate content of the casting solution and on the nature of solvent used. The separation properties of the prepared asymmetric membranes determined by reverse osmosis testing indicate a good correlation with the data obtained by the rheological measurements of the casting solutions. The latter can, therefore, be used as a practical tool for the investigation of early stages in the asymmetric membrane formation process.
Dyeing behavior of swollen cotton fibers and swelling mechanisms of intra‐ and intercrystalline swelling agents
Authors: Lokhande H. T.
Published: April 2003

Dyeability was used to study the swelling mechanisms of intra‐ and intermicellar swelling agents on cotton cellulose. Reactive and direct dyes were used for dyeing, and zinc chloride, ethylenediamine (EDA), and morpholine were used for swelling reactions. Changes taking place in the accessible regions as a result of swelling were determined by moisture regain, acid hydrolysis, formylation, and the lateral order distribution in the fiber structure. The results indicate that the intracrystalline swelling agents, viz., zinc chloride and EDA, induce specific changes in the accessible portions of the fiber. The accessible portion produced by the inorganic swelling agent has a more open structure than the disordered region produced by the EDA treatment. The distinctive nature of the accessible portions in swollen cotton fibers treated with the two reagents was reflected in all the properties studied. This was attributed to the different mechanisms of swelling and decrystallization of cotton fibers by zinc chloride and EDA. Morpholine was shown to bring about considerable changes in the accessible portions of the cotton fiber which were responsible for increased dyeability with reactive dyes, and was also shown to increase the amount of “truly” accessible regions by breaking the “imperfect crystals” in the disordered regions as well as on the surface of crystallites.
Viscosity index. I. Evaluation of selected copolymers incorporating n‐octadecyl acrylate as viscosity index improvers
Authors: Jordan Edmund F. , Smith Steven , Koos Ronald E. , Parker Winfred E. , Artymyshyn Bohdan , Wrigley A. N.
Published: April 2003

Compositionally and structurally varied copolymers all containing n‐octadecyl acrylate were prepared and evaluated as viscosity index improvers in a common base oil under conditions of low shear. Systems evaluated over a range of copolymer and blend composition were: copolymers of n‐octadecyl acrylate with, respectively, methyl methacrylate, 2‐ethylhexyl acrylate, and n‐dodecyl acrylate; and homopolymers of poly(n‐octadecyl acrylate), prepared with a wide range of molecular weights. Properties were compared with those of blends of commercial methacrylate copolymers (acryloids) which had been freed of their entraining liquid. Mixtures of base oil with copolymers of n‐octadecyl acrylate and methyl methacrylate, compared at fixed SAE viscosities, were the most efficient of all blends studied. They had the smallest rate of change of viscosity with temperature (as measured by their ASTM slopes), particularly in the composition region of incipient polymer precipitation at room temperature. Efficiency of certain of these composition was somewhat greater than that of the acryloids. A parameter that related concentration and weight‐average molecular weight was used to correlate all of the data for ASTM slope and viscosity. Empirical relations developed by using this parameter enabled rheological data to be estimated that agree within 6% of experimental values for the case of thermodynamically good base oil solvents. These data demonstrated the relatively small contributions of copolymer structure to viscosity index improvement.
A proposed mechanism for the degradation of addition polymers in cavitating ultrasonic fields
Authors: Doulah M. S.
Published: April 2003

A mechanism for the degradation of polymer molecules in ultrasonic cavitation has been proposed which takes into account the energy released by imploding cavitation bubbles in the form of hydrodynamic waves. Relationships for degradation rate constant and limiting chain length linking with the cavitation energy have been derived and are compared with published results on 1% solutions of polystyrene in benzene. These results show satisfactory agreements with the theory presented when the cavitation wave energy is taken proportional to the energy supplied to the ultrasound generating transducer.
The chemistry and development of tannin‐based adhesives for exterior plywood
Authors: Pizzi A. , Scharfetter H. O.
Published: April 2003

Condensed tannins are phenolic in nature and undergo reaction with formaldehyde to form resins. Tannin/formaldehyde condensates tend to have a low degree of condensation resulting in bonds lacking strength and water resistance. Small amounts of short‐length phenol/resorcinol/formaldehyde, phenol/formaldehyde, and urea/formaldehyde polymers are used to increase the degree of polymerization of tannin‐formaldehyde resins, decreasing brittleness and increasing water resistance. Furfural is used to plasticize tannin/formaldehyde resins to improve the distribution of stress forces on the glueline, overcoming weakness due to stress concentration. Exterior plywood panels were prepared using these modified tannin/formaldehyde resins as adhesives. The modified tannin/formaldehyde adhesives perform well, have similar characteristics to and are as easy to use as phenol/formaldehyde adhesives, and also have a few advantages, especially tolerance to faster pressing times.
The effect of polar groups on the dielectric loss of polyethylene
Authors: Sato Yukihiko , Yashiro Takamasa
Published: April 2003

The dielectric loss tangent for polyethylene with low dielectric loss was approximated by tan δ = Cf Σ(nμ2), where n and μ are the number and dipole moment of polar groups, respectively, and Cf is a parameter. The type and number of polar groups in the polyethylenes were mainly determined from infrared spectra obtained with a Fourier transform spectrometer. It was found that the contribution of hydroxyl and carbonyl groups to tan δ was significantly large, but the contribution of double bond groups was less significant. The tan δ was observed to decrease with a decrease of methyl group density although the overall contribution of methyl groups to tan δ was small. This suggests that tan δ is closely related to the secondary structure of polyethylenes, thus indicating the methyl groups seem to play an important role in the secondary structure.
A free‐volume interpretation of the influence of the glass transition on diffusion in amorphous polymers
Authors: Vrentas J. S. , Duda J. L.
Published: April 2003

A new version of the free‐volume theory of diffusion is used to describe polymer–solvent diffusion both above and below the glass transition temperature. Expressions are derived for the temperature dependence of the mutual diffusion coefficient and for the effective activation energy in the limit of zero penetrant concentration. The theory also describes the effect of the glass transition on the diffusion process. Predictions of the theory are compared with available diffusivity data for amorphous polymer–solvent systems.