bluuebunny/crossref_metadata_2025 huggingface dataset:
Graft copolymerization of vinyl monomers onto modified cotton. IX. Hydrogen peroxide–thiourea dioxide redox system induced grafting of 2‐methyl‐5‐vinylpyridine onto oxidized celluloses
Authors: Hebeish A. , El‐Rafie M. H. , Waly A. , Moursi A. Z.
Published: April 2003

Cotton cellulose was independently oxidized with potassium periodate, potassium dichromate‐sulfuric acid, and potassium dichromate–oxalic acid, and the resulting oxidized celluloses were further modified by treatment with chlorous acid or sodium borohydride. The various modified celluloses so obtained were grafted with 2‐methyl‐5‐vinylpyridine using a thiourea–dioxide–H2O2 redox system. It was found that the initiation characteristics of the cellulose samples vary widely with the oxidizing agent used. Further modification of the oxidized celluloses by treating them with chlorous acid enhances considerably their susceptibility toward grafting. The opposite holds true when these oxidized celluloses were modified by sodium borohydride treatment. Excluding thiourea dioxide from the polymerization system offsets grafting onto cotton cellulose while considerable grafting takes place on the various oxidized celluloses and their further modified samples. The work was also extended to study the factors which affect the graft uptake, homopolymer formation, and total conversion. In addition, the reactions involved in initiation of grafting were elucidated.
Ozone treatment of water‐soluble polymers. III. Ozone degradation of polyacrylamide in water
Authors: Suzuki Junzo , Iizuka Shinobu , Suzuki Shizuo
Published: April 2003

Polyacrylamide (MW 350,000) was ozonized at pH 2 and pH 10 buffer solution. There was little ozonization at pH 2, but at pH 10 the COD and the viscosity of the solution decreased upon ozonization, and a linear relationship existed between the ozone consumed and the number of breaks calculated from the viscosity. This relationship apparently indicated that 45 molecules ozone were consumed for one cleavage of the polymer chain. Such random cleavage was confirmed also by the observation of molecular weight distribution by means of gel filtration chromatography. The amide group decreased scarcely by the ozonization, while a small amount of aldehyde was observed in the ozonized solution. No remarkable change was observed in the IR spectra of the ozonized sample, except for a weak absorption band at 1725 cm−1 which arose from the carbonyl of aldehyde or ketone. Although no variation was observed in the 13C NMR spectra either, a strong absorption peak at 266 nm appeared in the UV spectra of the ozonized solution and increased with the ozonization time. This phenomenon was presumed to be due to the formation of a certain ring structure between the amide group and the small amount of ketone produced in the main chain. However, the details of the ozonization mechanism could not be ascertained.
Comparison of similar narrow molecular weight polystyrenes
Authors: Plazek Donald J. , Agarwal Pawan
Published: April 2003

Discrepancies between the level of the viscosity at 200°C of the Dow series of polystyrenes and another narrow molecular weight distribution polystyrenes have been pointed out by Toosi, Porter, and Johnson in 1969. Penwell and Graessley have shown in 1974 that over a wide range in temperature one member of this series, S109, has a significantly lower viscosity than samples of similar molecular weight from other sources. Fetters has established the presence of high molecular weight tails in several of the much studied series. The investigation being reported here reveals the effect of the high molecular weight tail in the viscoelastic behavior of the S109 in the terminal zone of response. In addition, it is shown by an enhanced rate of creep in the glass to rubber‐like dispersion that the glass temperature of the S109 is depressed by about 4°C.
Degradation of aqueous poly(acrylic acid) and its sodium salt solutions by high‐speed stirring
Authors: Nakano Akihiko , Minoura Yuji
Published: April 2003

Poly(acrylic acid) and 100% neutralized poly(acrylic acid) in pure water were stirred at 30°C at 30,000 rpm with a T. K. Homomixer at polymer concentrations ranging from 2% w/v to 0.0025% (25 ppm) for 2 hr to investigate the effect of polymer chain conformation on chain scission by high‐speed stirring. After 2 hr of stirring at low concentration, intrinsic viscosity measured in 1.00 mole/1. NaCl solution at 30°C for 100% neutralized polymer was lower for the polymer which was stirred after 100% neutralization than for the one before 100% neutralization, showing that expanded polymer chains were more easily ruptured.
Indentation studies in aluminum‐filled epoxies
Authors: Theocaris P. S. , Paipetis S. A. , Papanicolaou G. C.
Published: April 2003

A class of aluminum‐filled epoxy composites were subjected to indentation tests over a wide temperature range. The tests were carried out under constant load and continuously varying temperature. The effect of aluminum content, applied load, and adhesion efficiency between matrix and aluminum particles on the indentation behavior was studied. Measured indentation values were found to lie within limits predicted theoretically.
Morphological zones and orientation in injection‐molded polyethylene
Authors: Tan Victor , Kamal Musa R.
Published: April 2003

The properties of injection‐molded plastics parts are affected by resin properties, molding geometry, and molding conditions. The thermomechanical history, which results from the interactions between resin properties and molding conditions, controls the development of microstructure within the article. In turn, the microstructure controls the ultimate behavior of injection‐molded parts. Morphology and orientation and their distributions are among the most important microstructural characteristics affecting the ultimate mechanical and physical behavior of molded articles. This work summarizes some of the results of an extensive experimental and theoretical program to study the factors affecting the development of morphology and orientation in injection‐molded polyethylene. In particular, various experimental techniques are employed to study the distribution of morphology and orientation in simple moldings and to relate these characteristics to resin properties and molding variables. Furthermore, an attempt is made to employ mathematical models to explain and predict some of the observed phenomena especially in relation to the distribution of morphological zones in the molding. It appears that model predictions are in good agreement with experimental results.
Plasma‐deposited polymer films. III. The effects of gamma irradiation
Authors: Oberbeck W. F. , Mayhan K. G. , James W. J.
Published: April 2003

The results of a study of irradiated and unirradiated samples of polymers prepared by plasma polymerization in an inductively coupled radiofrequency (rf) reactor using infrared, elemental, thermogravimetric, and ESR analyses and density and refractive index measurements are presented. The plasma‐formed polymers studied include polypropylene, poly(ethylbenzene), poly(methyl methacrylate), poly(tetrafluoroethylene), poly(chlorotrifluoroethylene), and poly(trimethylchlorosilane).
Heterogeneous network polymers. VI. Effects of rate of solvent evaporation on residual PGA liquid crystal structure and its dynamic mechanical properties
Authors: Mori Tetsuo , Tanaka Ryuichi , Tanaka Takehide
Published: April 2003

Domains of cholesteric liquid crystal structures exist in films of heterogeneous network polymers from poly(L‐glutamic acid) (PGA) and poly(oxyethylene glycol) (PEG M̄n = 302, 1003). The sizes and the amounts of the domains are dependent on the PGA content, the evaporation rate of the solvent, and the molecular weight of PEG. At the PGA content of 40% by weight, the sizes of the domains increase, the glass transition temperatures shift to higher temperatures, and the densities increase with increase in the rate of solvent evaporation. These observations suggest that the phase separation of PEG takes place at a PGA content of 40% when the evaporation rate is small. On the other hand, at a PGA content of 70% by weight, the sizes of the domains increase, the glass transition temperatures shift to higher temperatures, and the densities vary little with decrease in the rate of solvent evaporation. These observations suggest that PEG molecules are accommodated among α‐helices of PGA and that the cholesteric liquid crystal phase grows at a PGA content of 70% when the evaporation rate is small.
Thermal behavior of aryl‐aliphatic polyamides
Authors: Varma I. K. , Sundari V. S. , Varma D. S.
Published: April 2003

Low molecular weight poly(p‐phenylene sebacamides) and (m‐phenylene sebacamides) were prepared by interfacial polycondensation by varying the concentration of p‐and m‐phenylenediamine in the initial feed. The polymers were characterized by intrinsic viscosity measurement and IR spectra. The relative thermal stability was evaluated by differential thermal analysis and dynamic thermogravimetry in air and nitrogen atmospheres. A systematic dependence of stability on intrinsic viscosity of poly(m‐phenylene sebacamide) was observed indicating an endgroup initiation of degradation. No such dependence was observed in poly(p‐phenylene sebacamide). A probable mechanism for the thermal degradation has been proposed.
Spectral studies on cellulose treated with sodium deuteroxide
Authors: Venkataraman A. , Subramanian D. R. , Ayare D. S. , Manjunath B. R. , Padhye M. R.
Published: April 2003

Cellulose II and cellulose I samples were treated respectively with a strong solution of sodium deuteroxide in D2O and a 99% solution of ethylenediamine. The complexes were washed with D2O and the nature of the OD bands were studied after rehydrogenating the sample. The infrared spectra of these rehydrogenated samples showed well‐resolved OD bands which are resistant to reexchange. The Characteristic bands are discussed and compared with the predicted OH‐OD frequency shifts.
Graft copolymerization onto starch. III. Grafting of acrylonitrile to gelatinized potato starch by manganic pyrophosphate initiation
Authors: Mehrotra Rakesh , Rånby Bengt
Published: April 2003

Recent development of synthesis and applications in grafting of acrylonitrile (AN) to gelatinized starch by Ce4+ initiation have been briefly reviewed. Using the Mn3+ method, the effects of starch pretreatment temperature on grafting parameters in grafting of AN onto starch have been studied. Total conversion of AN to PAN and % add‐on were almost constant and showed only slight variation with increasing starch pretreatment temperature. Average molecular weight of grafts showed, however, an increase by a factor of nearly 10 (i.e., from 0.4 X 105 to 4 X 105) after swelling and gelatinization of the starch, and the grafting frequency (anhydroglucose units per grafted chain) increased in proportion. In grafting of AN onto gelatinized starch, increasing Mn3+ concentration increased the conversion of monomer and % add‐on, whereas the average molecular weight of grafts and the grafting frequency (AGU/chain) decreased. An increase in the amount of starch also increased the conversion of monomer and the grafting frequency (AGU/chain) but decreased the % add‐on and the average molecular weight of the grafts. Selective solution of PAN homopolymer by dimethylformamide indicated that grafting efficiencies were high in all cases. The results are interpreted in terms of slow termination rates due to high viscosity of gelatinized starch.
Notch sensitivity of polymers
Authors: Prabhakaran R. , Nair E. M. Somasekharan , Sinha Pramod Kumar
Published: April 2003

The influence of notches on the static tensile strenght, low‐cycle fatigue strength, and creep rupture strength was investigated for selected polymeric materials. This investigation was prompted by the unusual phenomena of necking and notch strengthening observed in some glass fiber reinforced plastic materials. Two types of epoxy resin, polymethyl methacrylate and polycarbonate, were studied under static tensile loading. Three sizes of semicircular symmetrical side notch on flat specimens were investigated. It was observed that one of the epoxies was very notch sensitive, while the other exhibited significant (and maximum, out of all the polymers tested) notch strengthening in tensile loading. Perspex and polycarbonate showed a small notch sensitivity for the smallest and intermediate notches but notch strengthening for the biggest notch. The epoxy resin which exhibited notch strengthening was also tested with different percentages of hardener; for the biggest and the intermediate notches, there was a notch strengthening effect and unnotched as well as notched tensile strength showed a peak around 14% hardener. The epoxy which exhibited notch strengthening in tensile loading was next tested in low‐cycle fatigue and creep loading. The behavior in low‐cycle fatigue and creep loading was remarkably similar: it was found that for this polymer, the notch sensitivity was small in the case of the smallest and intermediate notches, whereas there was a significant notch strengthening effect in the case of the biggest notch. It is recommended that notch‐strengthening behavior be added to the other criteria for the selection of matrices for composite materials.
Shear girdling phenomenon in polymers
Authors: Pae K. D. , Silano A. A.
Published: April 2003

Hollow and solid specimens of polypropylene and solid specimens of polyoxymethylene exhibited an effect under torsional shear which is analogous to the necking usually observed in tensile tests. After reaching some critical shear strain in the postyield region localized shear deformation developed on the gauge length. As twisting was continued a dramatic decrease in the diameter of the cross section was observed. This torsional shear induced phenomenon was named girdling. The superimposition of hydrostatic pressure up to 6 kbar has a significant influence on the extent of girdle formation. Stress whitening, observed on the solid polyoxymethylene specimens was suppressed by the application of pressures greater than 1 kbar. Very large shear strains produced a ratchet‐type fracture surface on the solid specimens which indicates the presence of axial, radial, and tangential strains. Qualitatively, these results are supported by the finite deformation theory of elasticity.
Flame‐retardant action of chlorine compounds and antimony trioxide on cellulose fabric
Authors: Inagaki Norihiro , Hamajima Keiji , Katsuura Kakuji
Published: April 2003

Chemical research on the flame‐retardant action of halogen compounds and antimony trioxide on cellulose fabric was carried out by thermogravimetry, infrared spectrum analysis, and x‐ray diffraction analysis. The following results and conclusion were drawn: (1) Independently of the type of chlorine atoms introduced, that is, whether chlorine atoms are chemically bonded with cellulose chains or not, the introduction of chlorine atoms alone has little flame‐retardant effect, while combination of chlorine atoms with antimony trioxide is more effective. (2) Addition of only antimony trioxide to samples obtained from the dechlorination of chlordeoxycellulose is as effective as the combination of chlorine compounds and antimony trioxide, in spite of a trace of chlorine in the DCDC samples. (3) Introduction of chlorine compounds yielded the formation of carbonyl and double bond groups in the cellulose chains. The formation of the latter groups was accelerated by the combination of antimony trioxide; that of the former groups was inhibited. Most of the introduced chlorine atoms were missing in the condensed phase even at 300°C while a large portion of the initially added antimony trioxide remained in the condensed phase at least up to 400°C. One mode of flame‐retardant action of the combination of chlorine compounds and antimony trioxide was assumed to be the catalytic effect on the dehydration of cellulose to yield a thermostable polyene structure in the cellulose chains.
Polymérisation des méthacrylates d'ethers glycériques par le peroxyde de benzoyle: Accélération de la polymérisation par les sulfinates d'amines tertiaries
Authors: Ades D. , Fontanille M.
Published: April 2003

The kinetic study of the radical polymerization of phenyl glyceric ether methacrylate, taken as model of the corresponding derivative of bisphenol A, initiated by the system benzoyl peroxide/dimethyl p‐toluidine p‐toluene sulfinic acid salt, was performed. The effect of hydroxylic groups of the monomer on the polymerizability was established. The system used as initiator allows rapid polymerization of the monomer in presence of stabilizers.
Organic polymeric coatings for silica fibers. I. UV‐curing epoxy acrylate (V1F)
Authors: Schonhorn H. , Torza S. , Albarino R. V. , Vazirani H. N. , Wang T. T.
Published: April 2003

Coated optical fibers (∼100 μm) were prepared exhibiting fracture strengths in excess of 750 ksi (5.3 GN/m2) for lengths up to 100 meters. To achieve this we have developed a novel coating and coating application process. The coating is an epoxy acrylate, cured by UV irradiation, which may contain a multifunctional silane coupling agent. The coating liquid was applied to the fiber prior to solidification by an applicator, which facilitates centering of the fiber in the coating. Our coating system offers advantages in that there is no solvent to remove, thereby avoiding possible surface “corrosion” of the glass fiber. The reasonably low viscosity of the coating formulation allows for the extensive wetting of the fiber surface irregularities prior to solidification.
Investigation of the composite molecular structure of LDPE by using temperature rising elution fractionation
Authors: Bergström Christer , Avela Eero
Published: April 2003

In the synthesis of low‐density polyethylene there is a direct relationship between the synthesis conditions, molecular structure, and technical properties of the product. The evaluation of the molecular structure of the polymer is therefore important. The most important structure parameters in low‐density polyethylene are molecular weight distribution (MWD), degree of long‐chain branching (LCB), and short‐chain branching distribution (SCBD). Through chain transfer to polymer it is possible to get composite molecules made up of chains with different amounts of short‐chain branching. By using temperature rising elution fractionation (TREF) and plotting the methyl contents or the DTA melt temperature of the fractions as functions of the elution temperature, the SCBD within composite molecules can be evaluated. The deviations from linear relationships are caused by such SCBD within composite molecules. In order to demonstrate the buildup of composite molecules, samples from different parts of a reactor were investigated.
Decomposition of peroxide on carboxymethyl cellulose and its ability to initiate graft copolymerization
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

The decomposition of the peroxide group on fibrous carboxymethyl cellulose (CMC) and its ability to initiate graft copolymerization were investigated. The peroxide on CMC liberated hydrogen peroxide when the sample was heated in an aqueous medium. The decomposition of the peroxide was markedly increased by the use of ferrous salt and the irradiation with light of λ > 300 nm. The grafting of methyl methacrylate on CMC peroxide was initiated by heating or irradiating with light, where the rate of grafting and the reciprocal of the average molecular weight of grafts in general were proportional to the square root of the peroxide content of the sample. The peroxide content of the sample was related closely to the number of grafts in initiation. The number was estimated as 17 times for thermal initiation and 6 times for photoinitiation at the maximum values. The CMC peroxide showed a marked activity toward photografting of acrylamide, acrylic acid, acrylonitrile, and vinyl acetate on the substrate.
Influence of shearing history on the rheological properties and processability of branched polymers. I
Authors: Rokudai Minoru
Published: April 2003

The influence of shearing history on the viscoelastic properties of low‐density polyethylene (LDPE) is investigated. Swelling of extrudates from a melt indexer is measured for monitoring the variation in viscoelasticity. Continuous shearing of molten LDPE reduces the swelling ratio. The reduction is not due to molecular degradation, as evidenced by constancy of intrinsic viscosity. The rate of the reduction in the swelling ratio depends on the shearing conditions and characteristics of LDPE, but the swelling ratio finally attain a steady value. The swelling ratio reduced by the continuous shearing is completely recovered by solvent or heat treatment. The ratio of the completely reduced swelling ratio to the completely recovered one is defined as a new index representing the viscoelastic variation, the processing index (PI), and the relationship between PI and the primary molecular parameters of LDPE is investigated. It is concluded that the variation in the viscoelastic properties becomes more remarkable with increase in the weight‐average molecular weight. The cause of the viscoelastic variation is also discussed from the rheological and thermodynamic points of view.
Studies on chitin. VI. Binding of metal cations
Authors: Kurita Keisuke , Sannan Takanori , Iwakura Yoshio
Published: April 2003

The adsorption abilities of chitin and its congeners with two series of degrees of deacetylation prepared by two different deacetylation procedures were compared. Among the polysaccharides obtained by the heterogeneous method, those with higher amino group content had higher adsorption ability. Plots of collection percentages versus amino group content, however, did not give straight lines. The plot for the chelation on the congeners that were prepared by homogeneous hydrolysis had a maximum at about 50% amino group content, and the value was higher than that for the sample with the highest amino group content, which was prepared by heterogeneous hydrolysis. These results suggest that the polysaccharides with about 50% amino group content obtained by the homogeneous procedure are potentially useful for the removal of metals.
A rheological study of long branching in polyethylene by blending
Authors: Jaćović Mihailo S. , Pollock Dorothy , Porter Roger S.
Published: April 2003

Steady shear viscosities, dynamic viscosities and moduli, and the corresponding activation energies for flow were examined for a branched polyethylene, a linear polyethylene, and three of their blends at 150° and 190°C. The polyethylenes were chosen to have closely matched molecular weights and distributions. An R‐17 Weissenberg rheogoniometer and an Instron capillary rheometer were used. At lower stress, the branched polymer had a higher viscosity than the linear one, possibly because of the contribution of long branches to entanglements. At high stress, this contribution is reduced and the inherently smaller coil dimensions likely become responsible for the lower viscosity of the branched polymer. The activation energy for the branched polymer is high and decreases with stress, in contrast to the low and almost‐constant value for the linear polymer. The effects here of pressure on compression are considered. The entanglements of long branches may also decrease with increasing temperature. With decreasing stress, the activation energy for branched polymer tends to become constant, corresponding to an absence of pressure effects and an equilibrium entanglement of long branches for a given temperature range. The linear relationship between activation energy and blend composition problably means that any compressional effects, like free volume, are additive and that long‐branch entanglements rearrange with added linear molecules. The linearity may be the result, in part, of a broad distribution for the lengths of long branches.
Synergistic effect in gamma‐irradiated poly(vinyl chloride) hard foils stabilized by plasticizer–stabilizer systems
Authors: Szymański W. , Śmietańska G.
Published: April 2003

Changes in transparency and color as well as GHCl values of hard PVC foils exposed to gamma radiation were investigated while using different amounts of the stabilizers ethylene glycol bis‐β‐aminocrotonate (I), calcium/zinc laurate + epoxy compounds (II), and magnesium/zinc stearate + sorbitol + epoxy compounds (III), and plasticizers dioctyl phthalate (DOP) (IV), dioctyl sebacate (V), propylene glycol polyadipate + octyl alcohol composition (VI), and diisotridecyl phthalate (VII). A strong synergistic effect was observed in systems containing both plasticizer and stabilizer. Best results were obtained for the I + II + IV, I + II + V, and I + III + V systems.
Composite cation exchangers
Authors: Vasudevan Padma , Sarma N. L. N.
Published: April 2003

Sulfonated phenol formaldehyde resins containing different amounts of sulfonated sawdust were prepared. The thermal and chemical stabilities, scientific weight capacity, and apparent capacities for the exchange of Na+, Ca2+, and Mg2+ at different concentrations were detemined for both H+ and Na+ forms of resins. Composites containing up to 30%–50% of sawdust, while being very much cheaper, are comparable in their properties to the pure polymeric resin. Thus, cheaper exchangers can be prepared by substituting part of the polymer by sawdust.
Extrusion die swell of carbon black‐filled natural rubber
Authors: Bagchi Anoop K. , Sirkar Kamalesh K.
Published: April 2003

Extrusion die swell of natural rubber compounded with a wide variety of carbon blacks has been determined in a capillary rheometer using a long circular die. The range of variation of carbon black loading, surface area, and structure are, respectively, 10 to 60 phr, 44 to 124 m2/g, and 78 to 120 cc/100 g. The effective carbon black volume fraction φe not participating in the strain recovery leading to die swell is assumed to be the sum of the actual filler volume fraction and the fraction of unextractable rubber determined experimentally for each compound. Bagley and Duffey's analysis of extrusion die swell of unfilled polymers as unconstrained elastic recovery was adopted for a filled elastomeric system whose relative shear modulus (G/G0) is assumed to vary as (1 − φe)−N. The matrix shear modulus G0, originally introduced by Nakazima and Shida on the basis of a linearized approximation, will depend on the shear stress level because of nonlinear deformation. The power N will vary with shear stress which changes the orientation of carbon black aggregates. Except for these features, die swell data for a wide range of carbon black compounds fall on a single curve when plotted in the manner of the predicted relation between the wall shear stress, die swell, and φe. Replacing φe by Medalia's φ′ based on an equivalent sphere concept introduces a larger scatter around the mean curve.
Mechanochemistry and permeability of polyelectrolyte complex membranes composed of poly(vinyl alcohol) derivatives
Authors: Sato Hiroko , Maeda Makoto , Nakajima Akio
Published: April 2003

Two polyanions and two polycations were prepared by the esterification of poly(vinyl alcohol). Properties of their neutral polyelectrolyte complex membranes were compared with those of polyelectrolyte membranes. The charged state on the membranes was related closely to the mechanochemical reaction, the salt rejection, and the solution permeability. Both the salt rejection and the water flux of neutral polyelectrolyte complex memberanes were lower than those of the corresponding acidic or basic complex membranes.
The interaction of hydrogen sulfide with lead‐ and barium–cadmium–zinc‐stabilized poly(vinyl chloride)
Authors: Graedel T. E. , Franey J. P. , Starnes W. H. , Hische D. C. , Warren P. C.
Published: April 2003

Poly(vinyl chloride) polymers stabilized with tribasic lead sulfate discolor upon exposure to hydrogen sulfide gas as a result of lead sulfide formation. The discoloration occurs for samples in both cord and sheet forms and is shown to be a function of total H2S exposure, reaching a limiting value that is determined by the amount of lead stabilizer used in the polymer formulation. The permeation and diffusion constants for H2S through PVC stabilized with tribasic lead sulfate and with a liquid Ba–Cd–Zn formulation are found to be PPb = (6.0 ± 0.2) × 10−9, PBaCdZn = (5.2 ± 0.2) × 10−9 (both in cm3 gasċcm film/cm2 areaċsecċcm Hg), DPb = (1.3 ± 0.2) × 10−7 cm2/sec, and DBaCdZn = (6.4 ± 0.6) × 10−8 cm2/sec, all measured at 21°C. The stabilizing efficiencies of the formulations were assessed by HCl evolution measurements, which show that exposure to H2S decreases the initial polymer stability for both Pb‐stabilized and Ba–Ca–Zn‐stabilized formulations. Protection of stabilized PVC formulations from diffusing hydrogen sulfide is thus advisable for long‐term stability as well as for color integrity.
Novolacs from paraformaldehyde
Authors: Rojas A. J. , Williams R. J. J.
Published: April 2003

Novolacs were prepared from phenol, paraformaldehyde, and variable amounts of water and methanol using oxalic acid as a catalyst. The retarding effect of water and methanol is clearly shown. Diffusion of reactants in the two‐phase system does not seem to have a bearing on the measurements of reaction kinetics. A correlation between viscosity and refractive index of the polymer phase is shown. The advantages of using paraformaldehyde instead of aqueous formaldehyde solutions are summarized.
The effect of thermal history and strain rate on the mechanical properties of diethylenetriamine‐cured bisphenol‐A‐diglycidyl ether epoxies
Authors: Morgan Roger J.
Published: April 2003

The tensile mechanical properties of diethylenetriamine (DETA)‐cured bisphenol‐A‐diglycidyl ether (DGEBA) epoxies prepared from 9, 11 and 13 phr DETA are reported as a function of thermal history, strain‐rate and test temperature. These epoxies exhibit macroscopic yield stresses and >10% ultimate elongations. The mechanical properties of these epoxies exhibit a free‐volume dependence as a function of thermal history. Annealing below Tg causes an increase in the macroscopic yield stress and a decrease in the ultimate elongation, whereas quenching from above Tg lowers the yield stress and increases the elongation. These mechanical property modifications are shown to be reversible with reversible thermal–anneal cycles. The activation volumes associated with Eyring's theory for stress‐activated viscous flow for the DGEBA‐DETA epoxies are within the range of values (9–12 nm3) reported for noncrosslinked polymers. These observations suggest that the DGEBA‐DETA epoxies are not as highly crosslinked as would be expected from normal addition reactions of epoxide groups with primary and secondary amines. The formation of lower crosslink density networks is discussed in terms of potential chemical reactions.
Pressure drop through a tapered die with optimized flow characteristics
Authors: Lenk R. S. , Slater G.
Published: April 2003

The flow of power‐law liquids through tapered dies has been analyzed in an earlier paper.1 We now consider a taper which is additionally streamlined so as to make the transition from a broad and sluggish flow to a flow which is narrow and fast and as smooth as possible. This involves (1) the rational selection of an appropriate taper function within the relevant flow geometry and (2) the integration, between limits, of that function.
Studies of liquid‐induced crystallization of bisphenol a polycarbonate
Authors: Turska E. , Benecki W.
Published: April 2003

The course of liquid‐induced crystallization of a bisphenol A‐derived polycarbonate was investigated using acetone, methyl propyl ketone, methyl isobutyl ketone, and xylene as swelling agents. It was found that above a certain temperature, characteristic of a given polycarbonate–swelling agent system, the diffusion process takes place with the formation of a sharp boundary. The velocity of motion of the diffusion front was determined at various temperatures, and these data were then used to calculate the apparent diffusion coefficients and diffusion activation energies for the different swelling liquids employed. Moreover, a distinct separation of the diffusion and crystallization fronts was observed in the systems investigated, changes in the distance between these two fronts having been determined for various swelling temperatures. The above phenomenon was used to determine the experimental conditions making possible the characterization of a crystallization process not controlled by the diffusion of the swelling agent into the sample. The dependence of half‐times of crystallization on temperature was determined based on crystallization kinetics studies performed by means of a light depolarization technique.
Room temperature‐vulcanized silicone elastomer: Effect of curing conditions and the nature of filler on mechanical and thermal properties
Authors: Bajaj P. , Babu G. N. , Khanna D. N. , Varshney S. K.
Published: April 2003

Linear poly(dimethylsiloxane diol) of about 650 D.P. was synthesized by hydrolytic condensation of dimethyldichlorosilane in a saturated solution of sodium chloride. The polymer was then compounded with various fillers, Cab‐O‐Sil, Dicalite, and titanium dioxide, and cured at room temperature in the presence of tin salt and tri‐ or tetrafunctional silane. The tensile strength and elongation of the unfilled rubber were found to be 0.8 kg/cm2 and 320%, respectively. However, Dicalite White (100 phr)‐reinforced elastomer showed a tensile strength of 40 kg/cm2. Crosslink density was determined from the swelling studies. Thermal aging at 150, 200, and 250°C was also studied.
New attempt at flame‐retardation of polyester/cotton fabric blends
Authors: Inagaki Norihiro , Shintani Toshio , Kunisada Hideshi , Katsuura Kakuji
Published: April 2003

Two new flame‐retardation methods for polyester/cotton blend fabric were attempted with reference to thermal reactions of the blend fabric. One is the combination of phosphorylation of the cotton component and the addition of a phosphorus compound. The phosphorus compound must not interact with cotton component. The other involves the addition of a powerful flame retardant for the cotton component only. The flame retardant must induce only a small amount of carbonous products from the pyrolysis of the cotton component.
Mechanism and kinetics of grafting of macrodiisocyanate on to carboxyl‐containing acrylonitrile copolymers
Authors: Shalabi S. E. , Yan G. A. Gabriel , Rogovin Z. A.
Published: April 2003

The reaction of a carboxyl‐containing acrylonitrile copolymer with a macrodiisocyanate based on polypropylene oxide (Mn = 2000) in dimethylformamide (DMFA) and dimethylsulfoxide (DMSO) solutions was studied. The mechanism and main kinetic regularities of the grafting reaction were investigated. The reaction proceeds through formation of a mixed anhydride with its subsequent decomposition leading to liberation of CO2 and formation of graft copolymers. Carboxyl and nitrile groups of the copolymer take part in the reaction. A side reaction involving interaction of isocyanate groups of macrodiisocyanate with DMFA proceeds during synthesis of graft copolymers in DMFA solutions. The dependence of graft polymer yield on temperature, macrodiisocyanate concentration and on the catalyst/NCO ratio was determined. The activation energy of the grafting reaction is 22.9 kcal/mole. The specific viscosity of graft copolymers in DMFA solutions increases with the number of grafted chains.
Measurement of the rheological properties of thermoplastic elastomers
Authors: Han Chang Dae , Rao D. A.
Published: April 2003

Using the Han slit/capillary rheometer, measurements were taken of the rheological properties of commercially available thermoplastic elastomers, namely, styrene–butadiene–styrene (SBS) block copolymer (Shell, Kraton), ethylene–propylene copolymer (Exxon, Vista), olefinic‐type thermoplastic rubbers (UniRoyal, TPR 1600, TPR 1900, and TPR 2800), and urethane thermoplastic elastomers (UniRoyal, Roylar A863 and Roylar E9). The rheological properties determined were shear viscosity and first normal stress difference at various melt temperatures. Depending on the material and the melt temperature tested, the range of shear rates tested was 50 to 700 sec−1, and the range of shear stresses tested was 105 to 106 dyn/cm2. For comparison purposes, rheological measurements were also taken for a few materials using the Weissenberg rheogoniometer although its use was limited to low shear rates (or shear stresses). It was demonstrated clearly that the Han slit/capillary rheometer is a unique instrument for determining the rheological properties of thermoplastic elastomers in the range of high shear rates (or high shear stresses) often encountered in various polymer processing operations.
Photochemical behavior of poly(organophosphazenes). I. Poly[bis(p‐tolylamino)]phosphazene
Authors: Bortolus Pietro , Minto Francesco , Beggiato Giancarlo , Lora Silvano
Published: April 2003

The photolysis of poly[bis(p‐tolylamino)]phosphazene has been studied in methylene chloride solution. The main reactions observed were chain scission and crosslinking. The dissociation into radicals of polyphosphazene is proposed as the primary act of the photolysis. This has been substantiated by the results of the photolysis carried out in the presence of both radical scavengers and some benzophenones as sensitizers.
Wool shrinkage control and surface modification by ozone
Authors: Thorsen W. J. , Ward W. H. , Millard M. M.
Published: April 2003

In treating fine wool top, more ozone is needed to achieve a given level of felting shrinkage control than with coarse wool. Treatment that allows no more than about 20% top shrinkage in three successive washes is usually satisfactory for controlling fabric shrinkage. A detergent rinse after treatment markedly decreases top and fabric shrinkage. Ozonization decreases fiber strength and wet friction against glass but increases fiber‐to‐fiber adhesion enough to increase yarn strength. Scanning electron microscopy (SEM) of fibers before and after treatment and laundering indicates that ozone makes the fiber surface more plastic (presumably when wet) but more liable to mechanical damage and erosion, which increase with the severity of treatment and with laundering. However, treatments most effective for shrinkage control are not distinguished from less effective treatments by the degree and character of surface changes shown by SEM. Ring dyeing of fiber cross sections shows that effects of ozone are greatest near the surface. X‐ray photoelectron spectroscopy (XPS) and amino acid analysis show that cystine is oxidized to cysteic acid and that carbon is also oxidized at the surface. The increased dyeability (rate and uptake) is attributed to increased wettability, changed ionic balance, and crosslink scission, which, with cuticle damage, allow greater swelling and easier penetration. As found earlier with coarse wools, acid milling (leveling) dyestuffs further decrease shrinkage of treated fine wool. The position of wool in the triboelectric series is shifted toward the negative end by ozone treatment, expressing the higher electron work function of the added sulfonic acid groups. This shift is not simply related to shrinkage. Decreased feltability is attributed to softening of the wet cuticle layer and to increased surface charge, but the mechanism needs further study.
Preparation of ultrahigh modulus isotactic polypropylene by means of zone drawing
Authors: Kamezawa Mitsuhiro , Yamada Kenji , Takayanagi Motowo
Published: April 2003

Highly oriented isotactic polypropylene with ultrahigh modulus was prepared by means of the zone drawing method proposed by Kiho and Asai. This method features heating a limited portion of the sample. The maximum value of modulus attained was 15 GPa, which corresponds to about half the crystal modulus along the molecular axis evaluated by the x‐ray method. Such an ultrahigh modulus was obtained for a sample of medium molecular weight by inducing necking in the heater and subsequently cooling the sample at lower temperature. The loss tangent peak with the initiation of micro‐Brownian motion of amorphous chains became progressively smaller and broadened more at higher temperatures with increasing draw ratio. Orientation function of the crystal c‐axis increased with draw ratio λ in the region below λ = 9, but reached a constant value, 0.995, in the region above λ = 9. The modulus increased with draw ratio in all ranges of the draw ratio.
Flame‐retardant thermoplastics. I. Polyethylene–red phosphorus
Authors: Peters Edward N.
Published: April 2003

Red phosphorus is a highly effective flame retardant for polyolefins. The low additive levels of red phosphorus in polyethylene make it an attractive route to nonhalogen flame‐retardant systems. The mode of action of the red phosphorus has been investigated. Results indicate that the red phosphorus is effective both in the vapor and condensed phase. In the gas phase, PO species produced from the combustion of red phosphorus quench radical processes. In the condensed phase, the red phosphorus substantially lowers the heat of oxidation and traps radicals. This improved thermal stability results in a decrease in fuel production during burning.
Mechanochemical aspects of repetitive impacts and sliding on polymers
Authors: Sacher E. , Engel P. A. , Bayer R. G.
Published: April 2003

Scattered data exist in the literature on the chemical reactions which occur during mechanical contact. It is our contention that these reactions occur as a direct result of the high temperatures generated at the contact interface, due to the dissipation of mechanical energy. A theoretical analysis is used to identify and rank the various sources of heat generation during repetitive impact or sliding. New data, on both filled and unfilled polymers and elastomers, supported by data from the literature, are used to show that the resultant temperature rise causes reactions at the interface; the extents of these reactions depend on the polymer structure and the magnitude of the temperature rise. Several ways of reducing the magnitude of this temperature rise are discussed.
Influence of history on the gas sorption, thermal, and mechanical properties of glassy polycarbonate
Authors: Chan A. H. , Paul D. R.
Published: April 2003

Glassy polycarbonate has been subjected to sub‐glass‐transition annealing and exposure to high‐pressure CO2. The subsequently measured solubilities of nitrogen, argon, and CO2 in these specimens were found to be decreased by the former and increased by the latter. Annealing decreases the enthalpy of polycarbonate and mechanically embrittles it, whereas subsequent exposure to CO2 erases these effects of annealing, can make the polymer even more ductile than the untreated material, and can apparently give it a higher enthalpy. Annealing densifies the glass, whereas the CO2 treatment dilates it. The gas sorption observations are in accord with the dual‐sorption model, and the effects of prior history are apparently the result of changes in the Langmuir capacity, which evidently is a sorption mechanism that exists as a result of the nonequilibrium nature, or excess volume, of the glassy state.
Spectroscopic evidence for mechanochemical effects of moisture in epoxy resins
Authors: Levy R. L. , Fanter D. L. , Summers C. J.
Published: April 2003

Internal reflectance Fourier transform infrared (FT‐IR) spectra of tetraglycidyl diaminodiphenylmethane (TGDDM) cured with diaminodiphenyl sulfone (DDS) obtained before and after exposure to the combined effect of stress, elevated temperature, and moisture (STM), elevated temperature and moisture (TM), or stress and elevated temperature (ST) environments were used to search for evidence of irreversible chemical changes in epoxy resins. These changes were compared with the infrared changes observed during the late stages of curing. The infrared intensities of the bands attributed to the sulfone group are sensitive to chemical changes and moisture content, which suggests their potential use as molecular monitors within the epoxy network. The results of eight experimental series provide spectroscopic evidence indicating that exposure of epoxy specimens to STM and TM environments that greatly exceed anticipated service conditions results in detectable rupture of chemical bonds in the polymer network. The extent of bond rupture is independent of the applied stress in the 0–90 kg/cm2 range. Internal swelling stresses are therefore believed responsible for the observed bond cleavages. Spectral evidence indicates that postcure reactions are the most prominent chemical changes induced by exposure of epoxy specimens to the ST, SM, M, and T environments.
Mechanics of the extension of cotton fibers. II. Theoretical modeling
Authors: Hearle J. W. S. , Sparrow J. T.
Published: April 2003

A preliminary analysis of deconvolution of a nylon model is given. This is then developed to give the available deconvolution strain in cotton. The total extension is then given by adding the fibrillar strain and is compared with experimental values of breaking extension. The relation between convolution extension and stress is calculated in terms of structural and mechanical parameters. An earlier analysis derived cotton fiber modulus in terms of fibril extension and volume change. A new analysis shows that the introduction of shear resistance does not have a significant effect when rotation is prevented. However, false untwisting can occur at the helix reversal in cotton fibers. An analysis which allows for this rotation shows a strong dependence on shear modulus as well as fibril extension and helix angle. There is no volume change.
Interaction mechanisms between poly(methyl methacrylate) and tricalcium silicate (C3S)
Authors: Sugama T. , Kukacka L. E. , Horn W.
Published: April 2003

Interaction mechanisms between poly(methyl methacrylate) (PMMA) molecules and tricalcium silicate (C3S) occurring in a C3S‐filled PMMA molecular structure before and after exposure to a simulated 25% geothermal brine solution at 240°C have been investigated by use of thermal analysis, infrared spectroscopy analysis, scanning electron microscopy, and compressive strength tests. For C3S‐filled PMMA samples before exposure to hot brine, it was observed that an interaction between the C3S filler and the CH2 groups in the main chain of the PMMA occurred. After exposure to the hydrothermal environment, indications were that the brine solution induced ionic bonding between the carboxylate anion (COO−) groups in the PMMA and the Ca2+ ions from the C3S. The reaction contributed to improvements in the thermal stability of the PMMA.
Ultradrawing of amorphous polymers by coextrusion illustrated with atactic polystyrene
Authors: Zachariades Anagnostis E. , Sherman Edward S. , Porter Roger S.
Published: April 2003

Films of pure and high‐impact atactic polystyrene were prepared by the recently developed technique of solid‐state coextrusion. The films were produced at extrusion rates ≥4 cm/min at 126°C with a maximum extrusion draw ratio (EDR) of 11.6. These ultradrawn films are fibrous, have a high birefringence of −2.24 × 10−2, and exhibit a 72% elastic recovery. The material has a tensile modulus of ∼4–5 GPa and a tensile strength to break of 85 MPa. Thermal analysis suggests a constant Tg.
Properties of some cast polyurethane rubbers prepared from poly‐ε‐caprolactone polyols and diisocyanates
Authors: Guise G. Bruce , Smith Geoffrey C.
Published: April 2003

Polyurethanes were prepared by a one‐step method from poly‐ε‐caprolactone (PCL) diols, diisocyanates, and a triol crosslinking agent (either PCL triol or trimethylolpropane). The influence of composition on mechanical properties was examined. In some formulations the elastomeric properties were lost by crystallization of the PCL segments. The occurrence and rate of crystallization were influenced by the composition and factors such as hydrolytic degradation and oil swelling. In one series of polymers the susceptibility to crystallization could be predicted from the composition. These materials showed melting and glass transitions when examined by differential scanning calorimetry and thermomechanical analysis. The molecular weight of the PCL diol had a greater influence on the glass transition temperature than the diol concentration.