bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of reinforcing carbon black on network structure, technical properties, and failure mode of EPDM rubber
Authors: Pal Pranab K. , De S. K.
Published: April 2003

The high sulfur (HS) vulcanization system gives rise to higher apparent crosslink density and improvement in modulus, resistance to abrasion, compression set, heat buildup, rebound resilience, and dynamic set than that of the low sulfur (LS) vulcanization system. Tensile strength, tear strength, and flexing resistance were found to be better for the low sulfur (LS) vulcanization system. Rupture energy during tensile and tear failure determined from the Universal Testing Machine (Instron 1195) also reveals a similar phenomenon. Studies on fracture mode during different types of failure have been done by using a scanning electron microscope (SEM).
Effect of stabilizer type on the physicochemical properties of rigid PVC. III
Authors: Aboul‐Gheit A. K. , El‐Hennawi I. M. , Mohsen R. , Younan M. Y. A.
Published: April 2003

The crystallinity of rigid PVC specimens, stabilized by a tin mercaptide or a lead stabilizer, has been studied. It is found that the crystallinity of rigid PVC is greatly influenced by the type of stabilizer added, and that the response of the PVC toward subsequent UV exposure was also different. The effects of unstable structures and crystallinity, after UV irradiation, on the mechanical properties of rigid PVC have been investigated.
Applied macroinorganics. IV. Effect of the crosslinking agent on protonation, and metal ions complexing abilities, of ion exchange resins with poly(amido–amine) structure
Authors: Pesavento M. , Soldi T. , Ferruti P. , Barbucci R. , Benvenuti M.
Published: April 2003

Two classes of resins, having a poly(amido–amine) structure, have been synthesized. The basicity constants and the complexing abilities toward copper (II) and nickel (II) ions have been investigated by potentiometric techniques. The influence of the nature of the crosslinking agent on the basicities and the complexing abilities has been studied.
Effects of coupling agents on the rheological behavior and physical/mechanical properties of filled nylon 6
Authors: Luo Hong‐Lie , Han Chang Dae , Mijović Jovan
Published: April 2003

An investigation was made on the rheological behavior and physical/mechanical properties of highly filled nylon 6 composites with and without a coupling agent. As fillers, calcium carbonate and calcium silicate were used, and, as coupling agent, two silanes (Union Carbide, A1100 and Y9187) and two titanates (Kenrich Petrochemicals, KR‐44 and KR‐138) were used. It was found that all the coupling agents used increased the viscosities of the nylon/CaCO3 system. However, the effect of the coupling agents on the viscosity of the nylon/CaSiO3 system seems quite complex; namely, the titanate KR‐44 decreased the melt viscosity of the nylon/CaSiO3 composite, whereas the titanate KR‐138S and the silane Y9187 increased it. In general, the effectiveness of the coupling agents in improving the physical/mechanical properties of the nylon/CaCO3 and nylon/CaSiO3 composites was marginal. A considerable decrease in glass transition was observed upon exposure of all samples to water, regardless of the type of filler and coupling agent.
Viscoelastic properties of short‐fiber‐reinforced rubber composites and the role of adhesion
Authors: Murty V. M. , De S. K. , Bhagawan S. S. , Sivaramakrishnan R. , Athithan S. K.
Published: April 2003

Viscoelastic properties of short‐fiber‐reinforced natural rubber composites have been studied as a function of temperature and at different levels of adhesion. The effect of adhesion on the viscoelastic properties of the composites has been assessed, and it is found that the increase in adhesion increases the mechanical loss per cycle and modulus. With the increase in temperature the mechanical loss and modulus drop, indicating a possible deterioration of the adhesion at higher temperatures. Presence of carbon black increases the mechanical loss but does not necessarily increase the level of adhesion. The effect of overcuring has also been studied. Complex modulus of the composites displays an exponential behavior with the increase in volume fraction of fiber.
The preparation of high‐viscosity, partially hydrolyzed polymethacrylamides
Authors: Shepitka J. S. , Case C. E. , Donaruma L. G. , Hatch M. J. , Kilmer N. H. , Khune G. D. , Martin F. D. , Ward J. S. , Wilson K. V.
Published: April 2003

Due to the high chain transfer to monomer, the homopolymerization of methacrylamide yields polymers of extremely low molecular weight. On partial alkaline hydrolysis, the viscosities of these polymers in aqueous solution are much inferior to those of partially hydrolyzed polyacrylamide (HPAM). However, polymethacrylamides prepared by room temperature, persulfate‐initiated polymerization in the presence of small amounts of N,N′‐methylenebisacrylamide demonstrate posthydrolysis reduced viscosities in 0.01% NaCl comparable to typical commercial HPAM materials.
Photoinduced graft copolymerization. IX. Graft copolymerization of methyl methacrylate onto nylon 6 in the presence of pyridine–bromine charge–transfer complex as photoinitiator
Authors: Lenka Subashini , Nayak Padma L. , Dash Manoranjan
Published: April 2003

Photoinduced graft copolymerization of methyl methacrylate onto nylon 6 was investigated by using pyridine–bromine (Py–Br2) charge–transfer complex as initiator. The graft yield increased with increasing monomer and initiator concentration at the initial stages, and therefore it decreased. The initiator exponent was computed to be 0.5. The reaction was carried out at three different temperatures, and the overall activation energy was computed. A suitable mechanism has been suggested.
Determination of total short‐chain branching in polyethylenes by computerized data processing of infrared spectra
Authors: Dankovics A. , Füzes L.
Published: April 2003

A computer method is described to determine the short‐chain branching of polyethylene from IR spectroscopic data. The shape of the band at 1378 cm−1 (characteristic to the methyl side groups) was calculated by using first a deconvolution procedure (Ishige method) for the envelope curve of the overlapping peaks in the region of 1300‐1400 cm−1, followed by a convolution calculus applied only to the deconvoluted points of the peak in question. The results were in good agreement with values determined by Willbourn's compensation method.
The effect of interfacial adhesion on the tensile behavior of polystyrene–glass‐bead composites
Authors: Dekkers M. E. J. , Heikens D.
Published: April 2003

The tensile behavior at 20°C of polystyrene‐glass‐bead composites has been studied at several glass concentrations. To gain insight into the role of interfacial adhesion, the bonding between glass and polystyrene was varied by using different silane coupling agents. In contrast to the elastic behavior, the crazing behavior of the composites was found to be considerably affected by the degree of interfacial adhesion. This is explained by means of the different mechanisms for craze formation at adhering and nonadhering glass beads, respectively. Furthermore, it was found that both elastic and crazing behavior of the composites are influenced by the glass bead concentration.
Rheology of solvent‐cast polymer films
Authors: Briscoe B. , Smith A. C.
Published: April 2003

This paper describes and analyzes the results of an experiment where various thin polymeric films are continuously sheared between smooth glass substrates. The shear force per unit area has been measured as a function of mean uniaxial stress and temperature using representative “good” and “poor” casting solvents followed by a range of heat treatments. The polymers studied include high density polyethylene, polybisphenol‐A–carbonate, poly(ethylene terephthalate), atactic polystyrene, isotactic polystyrene, atactic poly(methyl methacrylate), isotactic poly(methyl methacrylate), poly(vinyl acetate), poly(vinyl alcohol), poly(vinyl pyrrolidone), poly(vinyl chloride), and polytetrafluoroethylene. The results indicate that the casting solvent has a very pronounced influence upon the rheology of the film. The casting solvents may apparently confer either ductile or brittle failure in the film and also influence the nature of the temperature and pressure dependence of the shear stress. The data have been analyzed using Eyring theory and also by reference to relevant published literature on the influence of solvent and thermal treatments on the morphology and deformation behavior of polymers. “Good” solvents generally tend to promote a brittle mode of failure with little temperature dependence. The same type of solvents also produced films which have higher shear strengths and show greater increases in shear strength with pressure. These data are adequately rationalized using free volume and entanglement notions.
Reaction of 3‐methyl phenol with methyl α‐eleostearate
Authors: Yoshimura Yukio
Published: April 2003

The aromatic ring substitution reaction of 3‐methyl phenol with methyl α‐eleostearate under acidic conditions was carried out. The product was analyzed to find out if 3‐methyl phenol was subjected to the ring substitution reaction with methyl α‐eleostearate at its conjugated double bonds. Up to two molecules of 3‐methyl phenol were addition‐reacted with the conjugated triene of the eleostearyl group of methyl α‐eleostearate. The 4‐position of 3‐methyl phenol was preferentially subjected to the cresol's ring substitution. When 3‐methyl phenol was reacted with a relatively large amount of methyl α‐eleostearate, the substitution reaction occurred at the 6‐ as well as 4‐position of 3‐methyl phenol, to yield a methyl α‐eleostearate dimer having 3‐methyl phenol units in its molecule. The above results were confirmed by infrared (IR), nuclear magnetic resonance (NMR), and high‐speed liquid chromatographic (HLC) analyses, and the results of a previous paper connected with reaction of 3‐methyl phenol were supported by the results of this paper.
Organotin polymers. VII. Copolymerization of triphenyltin methacrylate with some acrylic and methacrylic acid esters
Authors: Ikladious N. E. , Messiha N. N. , Shaaban A. F.
Published: April 2003

The monomer reactivity ratios for the copolymerization of triphenyltin methacrylate with methyl acrylate, ethyl acrylate, and butyl acrylate have been found to be r1 = 2.58, r2 = 0.66, r1 = 2.37, r2 = 0.43, and r1 = 1.27, r0.39 = 0.39, respectively. also, the copolymerization parameters of triphenyltin methacrylate with methyl methacrylate and butyl methacrylate were as follows: r1 = 0.94, r2 = 0.99, and r1 = 0.68, r2 = 0.83, respectively. Copolymerization reactions were carried out in solution at 70°C using 1 mol % AIBN, and the copolymer compositions were determined by tin analysis. The sequence distribution of the alternating diad fractions for the systems studied were calculated at various feed compositions. The structure of the triphenyltin methacrylate monomer as well as its azeotropic copolymer with butyl methacrylate were investigated by IR spectroscopy.
Photochemistry of polymeric systems. VI. Photocrosslinking of basic polymers and copolymers dyeing
Authors: M'Bon Gaston , Roucoux Colette , Lablache‐Combier A. , Loucheux C.
Published: April 2003

Poly(N‐vinylamine) (PVAm) and methylmethacrylate/dimethylaminoethylmethacrylate copolymers (MMA/DMAEMA) were prepared and then substituted by cinnamic or cinnamylidene photosensitive groups. The photosensitivity of these materials was determined using the so‐called photoresist test in various experimental conditions. A comparison was made between MMA/DMAEMA and methylmethacrylate/4‐vinylpyridine (MMA/4VP) photosensitized copolymers. The best results were obtained with MMA/DMAEMA on textile support. A photosensitization study was carried out by adding some compounds such as thioxanthone (10% in bulk). It showed that the multiplicity factor can be 10 with MMA/DMAEMA copolymers and even up to 64 for photosensitive PVAm. The addition of anionic dyes on the polymers emphasized that a better fixation occured for aliphatic amines than for pyridinic ones.
Concentration‐induced stress effects in diffusion of vapors through polymer membranes
Authors: Kim Myungsoo , Neogi P.
Published: April 2003

There are two types of anomalous diffusion of vapors in solid polymers which are held to be due to swelling. If the latter is seen as strain, then there must be an accompanying stress which can affect the nature and magnitude of diffusion. The theories of diffusion in polymers are examined in light of the network theory of Larché and Cahn. Their formalism is used to solve permeation and sorption in polymer membranes to illustrate the general features of the elastic effects, particularly the time‐dependent nature of the solubility. That “anomalous” effects will be present is without doubt, considering the concurrent nature of the added elastic effects. However, the present calculations fail to unearth any behavior similar to the case II diffusion. An order of magnitude estimate has been provided which shows that the effects of elasticity are usually significant in rubbery or amorphous glassy polymers where the anomalous effects occur.
Kinetics of swelling of cotton fibers in aqueous ethylenediamine solutions using X‐ray diffraction data
Authors: Chidambareswaran P. K. , Patil N. B. , Pawar A. D. , Shukla S. R. , Lokhande H. T.
Published: April 2003

Kinetics of swelling of cotton cellulose with 75% (w/w) ethylenediamine (EDA) solution has been studied using X‐ray diffraction. Apparently, the swelling reaction proceeds at three different rates, all obeying the first‐order kinetics. The first rate (k1), which is the fastest one, is hypothetically attributed to the swelling action of EDA–monohydrate in the amorphous region of cellulose; the second rate (k2), which is extremely slow, is responsible for the penetration of swelling species into the crystallites, accompanied by breakage of the hydrogen bonds in these regions; and the third rate (k3), which is faster than k2 but slower than k1, has been assigned to the decrystallization of the crystalline regions. The increase in temperature of swelling (from 10°C to 55°C) brought about increase in all these three rates with shortening of their respective periods. Thus, at temperatures of 35°C and above, k2 and k3 merge, giving a combined rate (k2+3). These results were confirmed from the data on the activation energy values. The changes in crystallinity were comparatively less, when 65% (w/w) EDA solution was used for swelling cotton fibers. The ineffectiveness of 65% (w/w) EDA solution was explained on the basis of the absence of powerful swelling species in the solution. An attempt has also been made to examine the kinetic data on the basis of the model for cotton fiber fine structure consisting of crystalline elementary fibrils and surfaces or regions of varying extents of hydrogen bonding.
Modified Cole–Cole plot based on viscoelastic properties for characterizing molecular architecture of elastomers
Authors: Harrell E. R. , Nakajima N.
Published: April 2003

The types of molecular architecture commonly present in many commercial elastomers include long branching, which in extreme cases results in crosslinked gel network. This architecture was modeled by preparing a series of ethylene–propylene copolymer samples in which the degree of branching was systematically varied. The frequency‐dependent viscoelastic properties of these model systems were measured over a temperature range of 80–230°C with a Rheometrics Mechanical Spectrometer. Time–temperature superposition was employed to obtain master curves of the storage G′ and loss G″ moduli and complex viscosity. The viscoelastic properties of the model samples change systematically with the variations in molecular architecture. Specifically, the low frequency Newtonian viscosity behavior is progressively replaced by non‐Newtonian power‐law behavior, and the G′ response relative to that of the G″ is significantly enhanced as long‐branching increases. The practical use of a modified Cole–Cole plot, in which the axes are expressed as the logarithms of G′ and G″, for analysis of molecular architecture is demonstrated. Changes in the long‐branch architecture of the model samples were readily detected as systematic variations in shape and displacement of the modified Cole–Cole plot. On the other hand, the data of molecularly linear elastomer samples of different Mw but similar MWDs were reduced to a single master Cole–Cole plot.
Diffusion of dyes in polyester fibers. IV. Anomalous sorption of disperse dye synthene scarlet P3GL
Authors: Narȩbska Anna , Lemańska Gizela
Published: April 2003

The investigations on dyeing of poly(ethylene terephthalate) fibers with disperse dye Synthene Scarlet P3GL have revealed anomalous sorption of the dye in heat‐treated samples. In the mathematical solution of the process it has been assumed that anomalous sorption can be treated as superposition in time of two stages of Fickian sorption. The contents of absorbed dye at quasiequilibrium CI, at the final equilibrium CII, and the apparent diffusion coefficients DI, and DII have been calculated using Hill's equation.
Use of photoacoustic spectroscopy in studying the natural weathering of polyethylene films
Authors: Anani Ali , Mobasher Amal , Rasoul Firas A.
Published: April 2003

Photoacoustic spectroscopy was used to assess the degradation of polyethylene under local natural weathering conditions. The results obtained are in good agreement with those obtained using infrared spectroscopy and from mechanical testing. Photoacoustic spectroscopy supports the accepted mechanism of polyethylene degradation.
Microscopic approach to energy dissipation during viscoelastic crack propagation
Authors: Ohtani Nobuo , Kobayashi Akira
Published: April 2003

The microscopic factors relating to the energy dissipation increase in the viscoelastic dynamic crack propagation such as in PMMA [poly(methyl methacrylate)] were investigated through the observation on the microfracture process ahead of the crack tip up to the microcrack formation. It is found that the energy dissipation remains almost constant in a certain low velocity range but increases sharply in the higher velocity range for the PMMA case. A cleavagelike fracture mode works in the former, and both the cleavagelike and a ductile‐fracture mode work in the latter. The increase in energy dissipation is attributed to the secondary cracks which remarkably increase in number depending on the crack velocity. The energy dissipation is proved to be independent of the crack velocity in cases where the crack is propagated by the cleavagelike fracture mode.
Solid foam–polyurethanes with a lowered combustibility
Authors: Troev K. , Todorov K. , Borisov G.
Published: April 2003

A composition of solid foam–polyurethane is developed, the polyol component of which is a mixture of oligoesteralcohols obtained as waste products in the production of dimethylterephthalate, and is modified with phosphorus or phosphorus plus chlorine‐containing antipyrenes. It is demonstrated that the introduction of antipyrenes into the foam–polyurethanes substantially enhances the combustion resistance of the composition, without impairing its physical and mechanical properties.
Peculiar thermal behavior of diallyl oxalate prepolymer
Authors: Yamawaki Masataka , Matsumoto Akira , Oiwa Masayoshi
Published: April 2003

First, the thermal behavior of diallyl oxalate prepolymer (PDAO) at 130–300°C was preliminarily compared with diallyl phthalate prepolymer; PDAO was self‐curable and degraded easily accompanying the evolution of gas. Next, the thermal degradation of PDAO was investigated in detail by TG. The TG curve of PDAO compared with those of various diallyl dicarboxylate prepolymers was peculiar suggesting two stages of thermal degradation processes with two maximum degradation temperatures, although the first stage is relevant to the significant release of carbon dioxide. In addition, the effect of the structural units, involving uncyclized, cyclized, and crosslinked units, on the thermal degradation of PDAO was examined; the thermal degradation rate was reduced with an increase in the cyclized units and was independent of the content of crosslinked units. From these results, the thermal degradation mechanism of PDAO is briefly discussed in terms of a radical mechanism.
Grafting onto polyester fibers. IV. Synergism during graft copolymerization of binary mixtures of vinyl monomers onto polyester fibers
Authors: Lokhande H. T. , Teli M. D. , Rao K. N. , Rao M. H.
Published: April 2003

Graft‐copolymerization reactions of binary mixtures of vinyl monomers (acrylamide–acrylic acid and acrylonitrile–acrylic acid) with polyester fibers have been studied by chemical initiation technique using benzoyl peroxide as an initiator. The total graft add‐on was determined gravimetrically, while the modified Kjeldahl's method for N‐estimation was employed to determine acrylamide and acrylonitrile grafts in their mixtures with acrylic acid grafts. Synergism of very high order was noticed during the graft‐copolymerization reactions. In the case of the acrylamide–acrylic acid system a very high order of synergism (129.15%) was noticed at equimolar proportions of the monomers in the grafting bath. Both acrylamide and acrylic acid showed synergistic influence over each other during graft‐copolymerization reactions. In the case of the acrylonitrile–acrylic acid system, however, the presence of acrylonitrile reduced the graft yield of the acrylic acid component showing a negative synergism; but acrylic acid enhanced the acrylonitrile graft yield to a considerable extent. The results have been explained in terms of reactivity ratios of the monomers. The conductivity results of the monomer mixtures also supported the experimental results.
Microphase state of oligobutadienediol‐based polyurethaneureas
Authors: Lipatov Yu. S. , Dmitruk N. V. , Tsukruk V. V. , Shilov V. V. , Priss L. S. , Dashevsky L. I.
Published: April 2003

Structural studies of oligobutadienediol‐based polyurethanes with various degrees of crosslinking were carried out. From absolute small‐angle X‐ray scattering, the degree of segregation of components was determined. It was concluded that a complete microphase separation of the different components is realized in all samples irrespective of the degree of crosslinking, and these polymers are two‐phase systems. While stretching, the fibrillar structure is formed.
New polyisobutylene‐based model elastomeric ionomers. VI. The effect of excess neutralizing agents on solid‐state mechanical properties
Authors: Mohajer Y. , Bagrodia S. , Wilkes G. L. , Storey R. F. , Kennedy J. P.
Published: April 2003

The role of excess neutralizing agents on the mechanical properties of three‐arm star polyisobutylene‐based model ionomers is discussed. The stress level, particularly at high elongations, is significantly affected by the presence of excess neutralizing agents, and these effects are observed with different cations such as potassium, calcium, and zinc. A morphological model is proposed that can account for the observed mechanical behavior.
Grafting vinyl monomers onto wool fibers: Graft copolymerization of methyl methacrylate onto wool fibers using vanadyl acetyl acetonate complex
Authors: Samal Shashadhar , Sahu Gangadhar , Nayak P. L.
Published: April 2003

The graft copolymerization of methyl methacrylate (MMA) onto native and reduced Indian Chokla wool fibers was studied in aqueous solution using the acetylacetonate oxovanadium (IV) complex. The rate of grafting was investigated by varying the concentration of the monomer and the complex, acidity of the medium, and the solvent composition of the reaction medium. The graft yield increases with increasing concentration of the initiator up to 8.75 × 10−5 mol/L, of the monomer up to 0.5634 mol/L, and thereafter it decreases. MMA was found to be the most active monomer when compared to other vinyl monomers. Grafting increases with increasing concentration of HClO4 and with increasing temperature. Reduced and oxidized wools were found to be better substrates than untreated, esterified, crosslinked, and trinitrophenylated wools. The extent of grafting was mostly dependent upon the concentration of SH groups in case of reduced wool. A suitable reaction scheme has been proposed and the activation energy was calculated from Arrhenius plot.
Water absorption isotherms for cured bisphenol A type epoxy resins: Effects of isotherm temperature and resin hardener
Authors: Ellis Bryan , Rashid H. U.
Published: April 2003

Water‐sorption isotherms have been determined for some bisphenol‐A‐type epoxy resins cured with either 4,4′‐diamino diphenyl methane (DDM), phthalic anhydride, or polyamide, Versamid 115. The absorption isotherms for the diamine‐cured resin are reversible and that at 0.2°C is linear for the whole accessible range of relative pressures (0 ⩽ h ⩽ 1). With increase in temperature deviations from Henry's law occur at successively lower relative pressures. It is shown that these deviations from Henry's law are related to a concentration dependence of the isosteric heat of absorption. Sorption by both the polyamide and phthalic‐anhydride‐cured resins is not reversible; there are weight increases following an absorption–desorption cycle.
Preparation and properties of graft and block copolymers of poly(p‐phenylene terephthalamide) with polybutadiene
Authors: Takayanagi Motowo , Goto Kohei
Published: April 2003

Graft copolymers of polybutadiene (PBD) onto poly(p‐phenylene terephthalamide) (PPTA) were prepared by the nucleophilic substitution of N‐metalated PPTA with telechelic PBD having bromide end groups. Block copolymers were synthesized by the condensation reaction of telechelic PBD having acid chloride end groups with amino‐group‐terminated PPTA. The structure of these copolymers was identified by IR spectra. Graft and block copolymers contained PBD segments up to 85 wt % and 45 wt %, respectively. Thermomechanical analyses (TMA) proved the existence of distinctive primary absorption peak corresponding with Tg of PBD for both graft and block copolymers. The Tg's of both types of the copolymers were further ascertained by the DSC curves. TMA curves suggested that the microphase separation occurred between PPTA and PBD. The incorporation of PPTA segments into PBD increased the decomposition temperature compared with the blend polymer composed of PPTA and PBD with the same composition.
Effects of complexation on the water vapor sorption of polymer alloys
Authors: Oyama Hideko Tamaru , Nakajima Toshinari
Published: April 2003

Water sorption measurements of the polyion complex between poly(p‐styrenesulfonic acid) (PStS) and poly(4‐vinylpyridine) (PVP) were carried out to study the effect of the Coulombic interactions between a polyanion and a polycation. The properties of the polyion complex were examined using infrared spectroscopy (IR), X‐ray diffraction, X‐ray photoelectron spectroscopy (XPS), and elemental analysis.

It was found that the ionic bonds between and groups led to the formation of a 1:1 polyion complex between PStS and PVP. The nitrogen 1s level in the PStS/PVP polyion complex increased 2.1 eV above its level for PVP, indicating protonation of the pyridine group. In addition, at 293 K and 303 K the water sorption of the complex was larger than that of the sum of the component polymers. In the preceding paper, the water sorption properties of the polyion complex between poly(acrylic acid) (PAA) and PVP were studied. Compared to this complex, the PStS/PVP complex absorbed more water relative to its components. This may be due to the stronger acid strength of the
over the COOH groups.
Sensitivity analysis of a batch polymerization reactor
Authors: Thomas Isabelle M. , Kiparissides Costas
Published: April 2003

The sensitivity of model output variables for a batch polymerization reactor to uncertainties in the kinetic parameters and initial conditions is studied. Differential equations that describe the time variation of sensitivity coefficients for the batch reactor are derived. Numerical integration of the sensitivity equations reveals that the system output responses are very sensitive to parameter variations especially when the polymerization exhibits an autoacceleration of the reaction rate.
Absorption of dicumyl peroxide by extruded polyethylene: Difference between surface and bulk morphology
Authors: Gupta J. P. , Sefton Michael V.
Published: April 2003

Under some conditions, the absorption of dicumyl peroxide (DICUP) at 70°C by extruded low density polyethylene (LDPE) displayed features which are characteristic of two‐stage sorption. For example, the initial slope of the DICUP absorption curve (plot of Mt/M∝ against \documentclass {article}\pagestyle{empty}\begin{document}$\sqrt t$\end{document} ) reflecting diffusion in the surface region was 2.5 times higher than the slope of the second stage (reflecting diffusion in the bulk) for 4‐mm‐diameter LDPE rods extruded at 130°C and 180 rpm (die pressure = 6000 psig). Only a single stage curve was evident in the same rod with its surface removed or in smaller diameter extrudate. Increasing the screw speed from 10 to 45 rpm at nearly constant extrusion pressure (1800–2380 psig) resulted in an approximately 50% decrease in the initial (first stage) slope with a negligible effect on the second stage slope. Increasing the die pressure (4900–6000 psig), by decreasing the extrusion temperature, at constant screw speed (125 rpm) resulted in an almost threefold decrease in the second stage slope without apparent effect on the first stage slope. Photomicrographs demonstrated the presence of distinct surface and bulk morphologies with evidence of a transcrystalline surface layer oriented prependicular to the surface at low screw speeds and larger spherulites in the bulk of the high pressure extrudate. Such morphological features and the observed dependence of the two stage sorption curves on extrusion conditions are consistent with the surface and bulk morphology of the extruded LDPE rod being dependent on the screw speed and die pressure, respectively. These uptake curves were determined by modifying the classical sorption technique to separate the measurement of the equilibrium uptake from the continuous recording of the slow changes in mass during absorption. This technique may be useful in the characterization of the migration process in other plastic/penetrant systems where diffusion is too slow to be measured by conventional means.
Effects of coupling agent on the rheological behavior and processability of polypropylene
Authors: Han Chang Dae , Kwack Tae Hoon , Luo Hong‐Lie
Published: April 2003

An investigation was made into the effect of coupling agents on the rheological behavior and processability of polypropylene. For the study, each of the following three commercially available coupling agents, a titanate coupling agent (Kenrich Petrochemicals, KR‐TTS) and two silane coupling agents (Union Carbide, A1100 and Y9187), was melt‐blended with polypropylene (PP). Melt blending was performed using a twin‐screw compounding machine. It was found that the zero‐shear viscosity of polypropylene was decreased by 1 order of magnitude after it had been extruded through the twin‐screw compounding machine and that, when coupling agents were added to it, its viscosity was higher than that of the PP without the coupling agents, undergoing the same deformation history through the twin‐screw compounding machine. Independent measurements of the molecular weight of the materials show that the weight‐average molecular weight (MW) of the extruded PP is 3.77 × 105, whereas the MW of the virgin PP (before extrusion) is 4.80 × 105, indicating that considerable molecular degradation occurred during extrusion and the MW of the PP extruded with coupling agent is greater than that of the PP extruded without coupling agent. In other words, the molecular weight measurement supports the viscosity measurements of the PP investigated with and without coupling agent. Also measured were the elongational viscosity of the PP with and without coupling agent, which was then correlated to the melt drawability of the materials investigated.
Permeability coefficient of proton‐irradiated poly(ethylene terephthalate) thin films
Authors: Bassani L. C. , Santos W. M. S. , Maréchal B.
Published: April 2003

The principle of operation of an apparatus developed to study gas permeation through thin films is described, and the measurement method is discussed. Use is made of diffusion theory to obtain an expression for the permeability coefficient as a function of the rate of increase of the pressure in the receiving volume. The activation energy for permeation of helium through PET is determined. The permeability coefficient for helium is found to increase significantly with the range of the implanted protons although the incident charge has been kept constant. The hypothesis of structural modifications of the proton implanted PET seems to be confirmed by small‐angle X‐ray scattering experiments on the irradiated samples.
Structure–property relationship in heat‐set poly(ethylene terephthalate) fibers. I. Structure and morphology
Authors: Gupta V. B. , Ramesh C. , Gupta A. K.
Published: April 2003

Poly(ethylene terephthalate) (PET) fibers having a range of structure and morphology were prepared by heat‐setting commercial PET yarn at temperatures of 100–250°C for 5 min under two conditions, while the yarn was free to relax and when it was held taut at constant length. The crystallinity, crystallinity orientation, and crystallite size were determined by X‐ray diffraction while birefringence was measured with the help of optical microscopy. The amorphous orientation factor was computed from the structural parameters. The coupling between the crystalline and amorphous regions was determined using the Takayanagi model. While crystallinity and crystallite orientation values for the corresponding samples of the free‐annealed and taut‐annealed series did not show very large differences, the free‐annealed samples had much lower amorphous orientation, especially when heat‐set at higher temperatures. Also while the free‐annealed samples showed a predominantly series type of coupling between the crystalline and amorphous regions, the taut‐annealed samples showed a significant degree of parallel coupling. It is shown that samples in which there is distinct phase separation between the crystalline and amorphous regions have a predominantly series type coupling.
The mechanism for enhanced autoadhesion in azoester‐modified polybutadienes
Authors: Roland C. M. , Böhm G. G. A.
Published: April 2003

The addition of IAD pendant groups to PB molecules results in a larger effective chain crosssectional area with consequent decrease in chain entanglements. This causes the rubber to be more complaint at low strains and strain rates. Simultaneously, the IAD structures give rise to polar and H‐bond interactions which cause the material to exhibit strong adhesion and to possess high green strength. As a result, the IAD‐PB is a relatively rare example of a synthetic polymer with good autoadhesive properties.
Force–temperature behavior of rigid rod polymeric fibers
Authors: Pottick L. A. , Allen S. R. , Farris R. J.
Published: April 2003

The force versus temperature behavior (at constant length) of poly(p‐phenylene benzobisthiazole) fibers (PBT) and Kevlar fibers has been investigated. Thermal expansion coefficients are evaluated for heat treated PBT (PBT‐HT) and Kevlar 49, to be −1.1 × 10−6/°C and −3.2 × 10−6/°C, respectively. Kevlar 49, PBT‐HT, and steel fibers exhibit a linear thermal elastic behavior whereas Kevlar 29 and as‐spun PBT do not. Material changes which occur during heat treatment processing are detected in the force‐temperature profile. A correspondence between the thermal and mechanical energy input which induces these material changes has been found.
Effect of absorbed water on dynamic modulus for short fiber–CR composites
Authors: Ashida Michio , Noguchi Toru , Mashimo Satoshi
Published: April 2003

Short fiber–elastomer composites with 10 vol % fiber, nylon 6–CR and PET–CR composites, absorbed water either in the moisture atmosphere or in water. The effect of absorbed water on the viscoelastic properties for these composites was investigated. The temperature dependence of tan σ for the nylon–CR composite showed that the α‐dispersion peak of nylon shifted to lower temperatures with increasing absorbed water content and that after displacement of the α‐dispersion peak the additional small hump appeared at about 90°C. For the PET composite, the α‐dispersion peak of PET shifted slightly to lower temperatures and the small shoulder at 90°C diminished with increasing absorbed water. The additional dispersion probably was caused by the interface between fiber and CR matrix and was independent of fiber orientation. The results suggested that nylon fiber absorbed a larger amount of water than CR matrix, while the water absorption for PET fiber was considerably less than for nylon fiber. The absorbed water in nylon fiber bonded stronger than that in CR matrix and was only slightly diminished by heat treatment under 100°C.
Compatibility of polypeptide blends of poly(γ‐butyl glutamate)/poly(γ‐benzyl glutamate)
Authors: Tsujita Yoshiharu , Ikenouchi Masami , Inukai Masahiko , Takizawa Akira
Published: April 2003

The compatibility of poly(γ‐butyl glutamate)/poly(γ‐benzyl glutamate) blend was examined by the estimation of the side chain dispersion of polypeptides in terms of the condition of preparation of blend films and the blend ratio. The polypeptide blend prepared for very short casting time exhibited an apparent compatibility. On the other hand, the polypeptide blend cast for long time did show incompatibility, irrespective of the blend ratio or mole fraction. The structures of the separated phase changed around mole fraction of 0.5 with the increasing mole fraction. The poly(γ‐butyl glutamate) island phase transformed into the poly(γ‐benzyl glutamate) island phase with increasing mole fraction of poly(γ‐benzyl glutamate) according to the calculation of the simple island‐matrix model by Takayanagi et al.
Chemical etching of poly(ethylene terephthalate) filaments
Authors: Chauhan R. S. , Rao M. V. S. , Dweltz N. E.
Published: April 2003

Chemical etching of poly(ethylene terephthalate) filaments with aqueous methylamine has revealed a complex stress—cracking behavior, which varied with orientation and thermal crystallization conditions. The appearance of both longitudinal and transverse cracks, can be explained on the basis of the existence of two types of domains, where the stresses are preferentially concentrated. They are explained on the basis of Prevorsek's structural model. In heat‐set fibers, there exists a skin to core differentiation in the internal stress distribution. The crack pattern also varied depending on whether the fibers were heat‐set in the taut or slack conditions. This chemical etching technique can prove to be a very useful tool, for the study of the internal stress distribution induced in fibers by various fabrication processes or post mechanical deformations.
The influence of reactor type and operating conditions on the molecular weight distribution in vinyl acetate polymerization
Authors: Taylor T. W. , Reichert K. H.
Published: April 2003

The vinyl acetate polymerization system was investigated with respect to the breadth of the molecular weight distribution (MWD) in batch, continuous segregated, and continuous micromixed reactors. Models were developed employing a complex kinetic scheme including polymer transfer and terminal double bond polymerization, without neglecting initiation and termination steps. Inclusion of a gel effect for terminal double bond polymerization gave better agreement with experimental molecular weight data in suspension polymerization. Simulation results showed the MWD order in the three reactor types is not fixed, but a function of reactant concentrations and the importance of chain branching. In some cases changing the initiator type and concentration will change the MWD order.
Annealing of polypropylene/poly(ethylene‐co‐propylene) blend. II. Influence of the structure and properties of poly(ethylene‐co‐propylene) and blended polyethylene on impact strength
Authors: Ito Junichi , Mitani Katsuo , Mizutani Yukio
Published: April 2003

The effect of annealing on the impact strength of PP/poly(ethylene‐co‐propylene) (PEP) and PP/PEP/PE blends was studied with regard to the structure of PEP and the polyethylene crystallinity. The tensile impact strength of annealed blends was remarkably affected by the PEP structure such as molecular weight and comonomer composition and the annealing temperature, while the brittle temperature was scarcely affected. For the PP/PEP/PE blends, annealing at temperatures above the melting point of PE lowers the tensile impact strength in a similar manner as the PP/crystalline PEP blend. These phenomena were explained on the basis of the deformation mechanism presented in the previous article, that is, a thicker interfacial layer of PP and PEP forms by means of annealing to increase the energy needed to deform the interface. By using a scanning electron microscope, the transition layer was observed at the interface between amorphous PEP and PE in the PP/amorphous PEP/PE blend after etching with nitric acid. The formation of a thicker transition layer between amorphous PEP and PE and a sizeable increase in PE particle size by annealing was observed. The phenomena should be correlated with the impact sensitivity, especially tensile impact strength, in the PP/crystalline PEP and PP/amorphous PEP/PE blends. A reasonable explanation of the microstructure in PP/PEP blends has been developed in terms of comonomer composition and melting property of PEP.
Biodegradation of gelatin graft copolymers. III
Authors: Kumar G. Sudesh , Kalpagam V. , Nandi U. S.
Published: April 2003

Gelatin‐g‐poly(methyl acrylate) and gelatin‐g‐poly(acrylonitrile) copolymers were prepared in an aqueous medium using K2S2O8 initiator. A plausible mechanism has been put forward for the observed grafting behavior of monomers. Gelatin‐g‐PAN showed a greater resistance to mixed bacterial inolucum compared to gelatin‐g‐PMA samples. The rate of degradation decreased with the increase in grafting efficiency. A parallel set of experiments carried out by employing the samples as the only source of both carbon and nitrogen showed a marginal but definite increase in the utilization of the polymer. The nitrogen analysis also showed the utilization of the polymer. Scanning electron micographs of the polymer films do show extensive pitting after microbiological testing.
Mechanisms of antioxidant action: Transformations involved in the antioxidant function of zinc dialkyl dithiocarbamates. I
Authors: Al‐Malaika S. , Marogi A. , Scott G.
Published: April 2003

The antioxidant mechanism of zinc dialkyl dithiocarbamate is examined in detail in model compounds. The kinetics of the reaction of zinc dialkyl dithiocarbamate with hydroperoxides were studied in inert and oxidizable substrates. A typical electron donor antioxidant and a base (CaCO3) were found to inhibit the peroxide decomposition. The oxidation products of the Zinc II complex appear to be quite different from those of the nickel II and iron III complexes. Two processes are involved in the antioxidant function of the zinc complex: The first is a free radical decomposition of the peroxides, which predominates at molar cumene hydroperoxide (CHP)/zinc diethyl dithiocarbamate (ZnDEC) ratios of 10 or less. At higher molar ratios an ionic reaction predominates, although there is a radical contribution at all ratios. Thiocarbamoyl disulfide does not seem to be formed as an intermediate from ZnDEC during the ionic process.
Shear modification of low density polyethylene
Authors: Teh J. W. , Rudin Alfred , Schreiber Henry P.
Published: April 2003

A single screw extruder was used to impose different shear histories on a low density polyethylene with broad molecular weight distribution and high molecular weight tail that had very little long chain branching. This polymer exhibits relatively high melt elasticity and the viscoelastic properties of its melt are strongly affected by preshearing. Such changes are accomplished without significant changes in molecular weight distribution or chemical structure. Measured viscous and elastic properties of the melt are different from piston‐driven and screw extruder capillary rheometers. Shear modification effects in single screw extruders are enhanced by decreasing melt temperature, increased screw rotation speeds, and higher screw compression ratios. Melt elasticity can be cycled between high and relatively low values, for the particular polymer, by annealing or shearing the polymer melt.
Solute diffusion in swollen membranes. IV. Theories for moderately swollen networks
Authors: Peppas Nikolaos A. , Moynihan Humphrey J.
Published: April 2003

A theoretical model was developed to describe solute transport through moderately swollen networks. The model is an extension of the previous analysis of Peppas and Reinhart (1983), and it describes the normalized effective diffusion coefficient of the solute through the network as a function of the equilibrium degree of swelling, Q, the hydrodynamic radius of the solute, rs, the number average molecular weight between crosslinks, M¯c, and a function f(ξ) of the mesh size ξ, which takes into consideration barriers due to crosslinks, entanglements, etc. For the development of this model, the Cohen–Turnbull (1958) free volume theory was modified to incorporate topological and mobility characteristics from de Gennes' analysis (1979).
Gas sorption and permeation of poly(γ‐methyl glutamate)
Authors: Tsujita Y. , Sumitomo T. , Nomura M. , Takizawa A.
Published: April 2003

Sorption, permeation, and diffusion behaviors of poly(γ‐methyl glutamate) were examined in the light of superstructure including conformation. Highly crystalline PMG, chloesteric twisted structure, low crystalline PMG, which are all composed of α helix, and β form PMG were prepared using cast solvent of chloroform, dichloromethane–dimethylformamide, and dimethylformamide and treating by formic acid, respectively. The large amount sorbed and the sorption capacity were interpreted by an existence of a microvoid in PMG cast film from chloroform. On the other hand, β form PMG had small amount sorbed. The sorption behavior was remarkably influenced by superstructure as well as conformation, while the effect of only conformation on the permeation behavior was recognized. A peculiar permeation was detected around 100°C for all the samples.
Polymerization of dicyclopentadiene: A new reaction injection molding system
Authors: Matějka Libor , Houtman Carl , Macosko Christopher W.
Published: April 2003

Dicyclopentadiene was polymerized by reaction injection molding (RIM) using a catalyst system based on WCl6 and diethylaluminium chloride. Ring opening polymerization results in formation of a crosslinked polymer with a high crosslink density. The kinetics of the fast exothermic reaction was followed by the adiabatic temperature rise method. In addition to the “adiabatic” polymerization, isothermal reactions were carried out in a thin mold. The properties of the cured samples were determined by dynamic mechanical measurements, solgel analysis, gas chromatography, mass spectrometry, DSC, and IR spectrometry. Gel fraction, glass transition temperature, content of the unreacted monomer, the modulus, and the degree of swelling were used to characterize the cured samples. The system shows very low critical conversion at the gel point (αc < 0.01) proving a chainwise mechanism of the polymerization. Possible participation of a cationic mechanism is discussed. We found the specific reaction temperature range (T = 100–140°C) for optimum properties of the cured samples. Deterioration of properties (decrease in the crosslinking density, etc.) at a high temperature is a result of a faster deactivation of catalytic centers and a reversibility of the exothermic ring opening polymerization. Reverse cyclodegradation is preferred at a higher temperature.