bluuebunny/crossref_metadata_2025 huggingface dataset:
On the compatibilization and dynamic vulcanization of polyacetal/ethylene propylene diene terpolymer blends
Authors: Kumar G. , Neelakantan N. R. , Subramanian N.
Published: April 2003

This study describes an attempt to improve the impact resistance of polyacetal (POM)/ethylene propylene diene terpolymer (EPDM) blends by means of compatibilization and dynamic vulcanization. A commerical copolymer, poly(acrylic acid)‐grafted polypropylene (PGP), has been used as a compatibilizer to control the phase morphology of the blend system. Dicumyl peroxide is used to dynamically vulcanize the EPDM elastomer in the blend. At temperatures higher than 185°C, the compatibilizer decreases the viscosity of compatibilized and dynamically vulcanized (cdv) POM/EPDM blends. Impact strength of the cdv blend system increases considerably with a marginal decrease in tensile yield stress and heat deflection temperature as the PGP content increases. The significant increase in impact strength seems to be due to the role of PGP as a linking agent for the binary blends rather than as a third component. Though dynamic mechanical studies do not indicate any compatibility in cdv‐POM/EPDM blends, scanning electron microscopy reveals the strong interpenetrating interphase in the compatibilized blend system. Dynamic vulcanization raises elastic recovery and tensile modulus of the blends. Hysteresis energies of the blends increase consistently with the addition of PGP. The crystalline structure of POM is not affected by compatibilization and vulcanization. © 1994 John Wiley & Sons, Inc.
Properties of a mechanically processed polymeric material
Authors: Pan J. , Shaw W. J. D.
Published: April 2003

A semicrystalline polymer, polyamide, was processed using a new technique. The technique is that of mechanically grinding the material using large inputs of energy at temperatures below the glass‐transition temperature and then later reconstituting the material by applying pressure and holding at a temperature below its melting point for a period of time. This technique is normally known as mechanical alloying and only very recently has been applied to polymeric materials. The mechanical properties of strength, ductility, toughness, and hardness of polyamide material processed by this technique are investigated and compared with those of polyamide material processed by other techniques. The results indicate that altered mechanical properties occur with specific enhancements. This means that useful structural components can be made from polymers using this processing technique. The analysis of x‐ray diffraction, nuclear magnetic resonace, scanning electron and optical microscopy suggests that this process has resulted in considerable alteration of both crystal structure and microstructure of this polymeric material. © 1994 John Wiley & Sons, Inc.
Analysis of polyethylene surface sulfonation
Authors: Fischer Dahlia , Eysel Hans H.
Published: April 2003

Attachment of SO3H groups onto the surface of polymers by treatment with fuming sulfuric acid is a well‐known procedure. In the present study we compare the number of SO3H groups per unit area measured by a number of methods including weight gain, thickness, FT‐IR transmittance spectra, FT‐IR surface spectra with ATR method, sodium exchange, and pH measurement of water in contact with the polymer surface. It can be shown that, under the chosen conditions, i.e., room temperature and 32% SO3 in H2SO4, oxidation of PE is the main reaction, while sulfonation accounts for less than 20% of the weight gained during reaction. Differences in the reactivity of high density and low density polyethylenes are discussed. Deprotonation in water compared with H+ /Na+ exchange indicates a poor penetration of sodium ions into deeper layers of the polymer. © 1994 John Wiley & Sons, Inc.
Viscoelastic behavior of flexible slabstock polyurethane foams: Dependence on temperature and relative humidity. I. Tensile and compression stress (load) relaxation
Authors: Moreland J. C. , Wilkes G. L. , Turner R. B.
Published: April 2003

The relaxation behavior of the load in compression and the stress in tension was monitored at constant temperature and/or relatively humidity for a set of four slabstock foams with varying hard‐segment content as well as two of the compression molded plaques of these foams. The majority of the compression relaxation tests were done at a 65% strain level in order to be consistent with the common ILD test. The tensile stress relaxation tests were performed at a 25% strain level. Over the 3‐h testing period, a linear relationship between the log of compressive load or the log of tensile stress versus log time is observed for most testing conditions. For linear behavior, the values of the slope or the load/stress decay rate are comparable in both the tension and compression modes with the values being slightly higher in magnitude for the compression mode. These rates of decay are in the range of −2.2 × 10 −2 to −1.7 × 10 −2 for a 21 wt % hard‐segment foam and −3.2 × 10−2 to −2.4 × 10−2 for a 34 wt % hard‐segment foam. Increasing %RH at a given temperature does bring about a steady decrease in the initial load or initial stress as well as a slight increase in the rate of relaxation. The effect of temperature on the relaxation behavior is most significant at temperatures near 125°C and above. The FTIR thermal analysis of the plaques indicates that this significant increase is due to additional hydrogen bond disruption and possible chain scission taking place in the urea and urethane linkages that are principally present in the hard segment regions. The relaxation behavior in both tension and compression is believed to be mostly independent of the cellular texture of the foam at the strain levels given above. This conclusion is based on the similar relaxation behavior between the plaques and the foams. © 1994 John Wiley & Sons, Inc.
Viscoelastic behavior of flexible slabstock polyurethane foam as a function of temperature and relative humidity. II. Compressive creep behavior
Authors: Moreland J. C. , Wilkes G. L. , Turner Robert B.
Published: April 2003

The compression creep behavior was monitored at constant temperature and/or relative humidity for two slabstock foams with different hard‐segment content. The tests were performed by applying a constant load (free falling weight) and then monitoring the strain as a function of time over a 3‐h time period. A near linear relationship is obtained for linear strain versus log time after a short induction period for both foams and at most conditions studied (except at temperatures near and above 125°C). The slope of this relationship or the initial creep rate is dependent on the initial strain level, espcially in the range of 10–60% deformation. This dependence is believed to be related to the cellular structs buckling within this range of strain. At deformations greater than 60% and less than 10%, the solid portion of the foam is thought to control the compressive creep behavior in contrast to the cellular texture. Increasing relative humidity does cause a greater amount of creep to occur and is believed to be a result of water acting as a plasticizer. For low humidities increasing the temperature from 30 to 85°C, a decrease in the rate of creep is observed at a 65% initial deformation. At 125°C, an increase in the creep rate is seen and is believed to be related to chemical as well as additional structural changes taking place in the solid portion of the foams. The creep rate is higher for the higher hard‐segment foam (34 wt %) than that of the lower (21 wt %) at all of the conditions studied and for the same initial deformation level. This difference is principally attributed to the greater amount of hydrogen bonds available for disruption in the higher hard‐segment foam. © 1994 John Wiley & Sons, Inc.
Synthesis and fungicidal activities of polymeric biocides. I. TBZ‐containing monomer and polymers
Authors: Oh Sang Taek , Min Byung Kwon , Ha Chang Sik , Cho Won Jei
Published: April 2003

The fungicidal monomer, N‐acryloyl‐2‐(4′‐thiazolyl) benzimidazole (AcTBZ) was synthesized from 2‐(4′‐thiazolyl) benzimidazole (TBZ) and acryloyl chloride in the presence of triethylamine in dry benzene at 30°C. The synthesized AcTBZ was identified by IR and 1H‐NMR spectra. The homopolymers of AcTBZ were obtained using BPO as a thermal initiator in benzene under different experimental conditions such as various initiator concentrations or polymerization temperatures. The homopolymer of AcTBZ was also prepared using benzophenone as a photo initiator in DMF at 20°C. The average molecular weights (Mw) of those poly(AcTBZ) s obtained were very low, being in the order of ca. 103. Copolymer of AcTBZ and polymer of AcTBZ and acrylic acid (AA) was synthesized with thermal or photo initiators. Poly(AcTBZ) and poly(AcTBZ‐co‐AA) were identified by IR and 1H‐NMR spectra. The fungicidal activities of AcTBZ, poly(AcTBZ), and its polymers as well as TBZ against Aspergillus niger and Chaetomium globusum were very excellent compared to those of control polymers such as poly(AA) and poly(ethylene‐co‐vinyl acetate). The fungicidal activities were decreased in the order TBZ > AcTBZ > poly(AcTBZ) > poly(AcTBZ‐co‐AA) against both Aspergillus niger and Chaetomium globusum. The fungicidal activities of TBZ, and the synthesized AcTBZ and polymers containing AcTBZ were better against Chaetomium globusum than against Aspergillus niger. © 1994 John Wiley & Sons, Inc.
Properties of blends of starch and synthetic polymers containing anhydride groups
Authors: Vaidya Utpal R. , Bhattacharya Mrinal
Published: April 2003

Corn starch was blended with styrene maleic anhydride copolymer (SMA), ethylene‐propylene‐g‐maleic anhydride copolymer (EPMA), and corresponding nonfunctional polystyrene and ethylene propylene copolymers. The concentration of starch in the blend was varied between 50 and 80% by weight. The torque generated during blending is reported increasing starch content for starch/SMA blends: the reverse was true for starch/EPMA blends. The torque was higher for the blends of the anhydride functional polymers compared to the blends of corresponding nonfunctional polymers. Water absorption of the blends increased with an increase in the starch content. Starch/SMA blends made at higher mixer speed or time were more water sensitive. Blends containing EPMA absorbed less water than SMA blends containing the same weight fraction of starch. Tensile strengths of blends containing functional groups were superior compared to the blends made from nonfunctional polymers. When the starch contents increased from 60 to 70%, the tensile strength remained unchanged for SMA blend but increased for EPMA blend. All samples supported the growth of microorganisms, which increased with increasing starch content. © 1994 John Wiley & Sons, Inc.
Semiempirical models for steady‐shear viscosity and prediction of first normal stress function
Authors: Seo Yongsok
Published: April 2003

In order to describe viscosity function behavior dependent on shear rate in steady‐shear flow and to predict the first normal stress function without using discrete relaxation time specturm, we combined the microscopic entanglement concept based on Graessley's entanglement network theory with the macroscopic constitutive model. The viscosity function derived from the entanglement model has three adjustable parameters and it was assumed to have the form of the inverse contangent function of the shear rate. Then the first normal stress function is obtained using the Wagner's relationship. The model prediction for the first normal stress coefficient is compared with experimental data of polymer melts. Even though viscosity function and the first normal stress function vary over a wide range of shear rate, they were in good agreement for polymer melts at high shear rate. First normal stress function do not show any numerical artifacts. However, discrepancy in the first normal stress function occurs at low shear rate. This is due to the irreversibility of the entangled molecule's motion that was not taken into consideration in the entanglement model. Irreversible nonaffine motion is introduced by adding a term similar to the White‐Metzner model's irreversible factor. Addition of irreversibility in the calculation of the first normal stress function considerably improves the agreement. Other comparisons are also presented and related discussions are given. © 1994 John Wiley & Sons, Inc.
Epoxy resin–polyethersulphone blends
Authors: Akay M. , Cracknell J. G.
Published: April 2003

A series of amine‐cured epoxy resin systems and the blends of these containing up to 50% polyethersulphone (PES) were evaluated in terms of curing behavior, microstructure, and mechanical and dynamic mechanical thermal properties. The epoxy networks were based on a 2 : 1 mixture of triglycidyl‐p‐aminophenol and the polyglycidylether of a phenolformaldehyde novolac, and a curing agent of 3,3'‐diaminodiphenylsulphone (DDS). The curing mechanism and the rate of curing were affected by the DDS and PES contents. Reaction between the epoxy resin and hydroxyl groups attached to PES was indicated in epoxy‐rich formulations. Phase separation, evident in all the blends, was affected by the curing rate. Various blend morphologies were observed depending on the epoxy network/thermoplastic composition. Blending improved ductility and toughness‐related properties, particularly at 20–40% PES contents, which corresponded to spinodal/co‐continuous morphologies. Changes in glass transition behavior were attributed to possible variations in intermolecular free volume. © 1994 John Wiley & Sons, Inc.
Rheological properties of highly swollen hydrogel suspensions
Authors: Budtova T. V. , Budtov V. P. , Navard P. , Frenkel S. Ya.
Published: April 2003

The shear rheology of diluted to concentrated suspensions of weakly cross‐linked sodium polyacrylate hydrogels were investigated by concentric cylinder rheometry. The size of the swollen gel particles is dependent on the initial size of the dry particle and on the nature of the added salt. Polyvalent salts are more efficient for contracting the swollen particles than monovalent ones. When suspended in water or in monovalent salt solutions, the viscosity at low concentrations shows a behaviour very similar to the one of flexible polymer solutions. Below the critical overlap concentration, the viscosity is independent of shear rate. The intrinsic viscosity is very large, on the order of 10–15 dL/g. This is in agreement with the large size of these swollen particles. Suspensions of such swollen gel particles are thus a good model for extremely high molecular weight polymer solutions. In polyvalent salt solutions different behaviour of the viscosity curves versus concentration was observed. This effect is caused by chemical cross‐linking of the hydrogel by polyvalent ions. © 1994 John Wiley & Sons, Inc.
Kinetics and reaction mechanism of fenton's‐reagent‐initiated graft copolymerization of acrylonitrile onto sodium alginate
Authors: Shah S. B. , Patel C. P. , Trivedi H. C.
Published: April 2003

The kinetics and mechanism of grafting of acrylonitrile (AN) onto sodium alginate (SA) using Fenton's reagent (Fe2+–H2O2) has been studied. The experimental results are found to be in good agreement with the proposed kinetic scheme. © 1994 John Wiley & Sons, Inc.
Simultaneous measurement of water diffusion, swelling, and calcium carbonate removal in a latex paint using FTIR–ATR
Authors: Balik C. M. , Xu J. R.
Published: April 2003

An in‐situ FTIR–ATR method has been used to monitor the sorption processes of water and pH 1.3‐sulfurous acid in two latex paints and the base polymer common to both. The sorption kinetics could not be described by a simple Fickian model. The spectra also showed evidence of polymer swelling, which was confirmed in separate swelling measurements. Anomalous behavior was noted for the latex paint containing CaCO3 when exposed to sulfurous acid. The amount of water sorbed by this sample went through a maximum, then decreased to a constant level. This was accompanied by similar variations in the degree of swelling of the sample. These changes are explained by the rapid loss of CaCO3 from this particular paint upon exposure to acidic solutions, followed by structural rearrangement to fill in the voids left by the CaCO3 particles. © 1994 John Wiley & Sons, Inc.
A generalized model to predict the viscosity of solutions with suspended particles. IV. Determination of optimum particle‐by‐particle volume fractions
Authors: Sudduth Richard D.
Published: April 2003

A new approach has been introduced to establish the optimum composition for all particles within a mixture or suspension to achieve the optimum packing fraction, φn, and/or the minimum viscosity, η. The derivation to obtain the optimum particle volume fraction assumed that a previously developed optimum composition for binary particles applied to any two particle volumes Vi and Vj in the mixture. The composition of the maximum packing fraction for a mixture of more than two particles was then assumed to be calculable from the optimized relationship of each separate binary pair of particle volumes Vi and Vi in the mixture. This derived equation was successfully shown to predict the optimum particle‐to‐particle composition of McGeary's experimentally measured binary, tertiary, and quaternary mixtures. The difference between the calculated and measured volume fractions was no greater than 3.85% and, in most instances, was significantly less than 3.85%. The maximum packing fractions, φn, determined experimentally by McGeary, were also successfully predicted to better than 3.26%. Theoretical particle‐to‐particle volume fractions evaluated for an example pressure‐agglomerated latex appeared to predict the particle‐size distribution only within a narrow range of particle sizes. However, when the theoretical and experimental results were evaluated as a function of the number of particles for each particle diameter, it was apparent that the agglomerated distribution closely approximated the theoretical optimum distribution above 600 Å. Agreement with theory below 600 Å was unsatisfactory. The decrease in viscosity of the example agglomerated latex appeared to have been enhanced as the optimum theoretical particle‐size distribution was approached. © 1994 John Wiley & Sons, Inc.
Fracture toughness and morphology of phenolphthalein poly(ether sulfone)–thermotropic liquid crystalline polymer blends
Authors: Yang Yuming , Yin Jinghua , Li Binyao , Zhuang Guoqing , Li Gang
Published: April 2003

Blends of a new phenolphthalein poly(ether sulfone) (PES‐C) and a thermotropic liquid crystalline polymer (LCP) were prepared by melt‐blending in a twin‐screw extruder. Rheological properties, fracture toughness, KIC, and morphology of the blends were studied. It was found that the addition of LCP could reduce the melting viscosity and improve the fracture toughness of the PES‐C matrix. The morphology of the LCP phase for the fractured section changed with increasing LCP content in the blend from dropletlike to fibrillar and layered structure. Strong interfacial adhesion could be observed at a lower content of LCP. The toughening mechanisms by blending LCP were also discussed. © 1994 John Wiley & Sons, Inc.
Compostability of cellulose acetate films
Authors: Gardner Robert M. , Buchanan Charles M. , Komarek Ron , Dorschel Debbie , Boggs Christy , White Alan W.
Published: April 2003

Composting is an accelerated biological decay process viewed by many to be a potential solution to the solid‐waste management crisis existing in many parts of the world. As part of a program to develop environmentally nonpersistent polymers that are compatible with a composting environment, we have developed a bench‐scale compost methodology that emulates a high efficiency municipal windrow composting operation. A series of cellulose acetate films, differing in degree of substitution, were evaluated in this bench‐scale system. In addition, commercially available biodegradable polymers such as poly(hydroxybutyrate‐co‐valerate) (PHBV) and polycaprolactone (PCL) were included as points of reference. Based on film disintegration and on film weight loss, cellulose acetates, having degrees of substitution less than approximately 2.20, compost at rates comparable to that of PHBV. NMR and GPC analyses of composted films indicate that low molecular weight fractions are removed preferentially from the more highly substituted and slower degrading cellulose acetates. © 1994 John Wiley & Sons, Inc.
Miscibility in blends of sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) and poly(p‐bromostyrene‐co‐o‐bromostyrene)
Authors: Vuković Radivoje , Bogdanić Grozdana , Kurešević Vjera , Srića Vlasta , Karasz Frank E. , MacKnight William J.
Published: April 2003

Miscibility in blends of random copolymers of p‐bromostyrene (pBrSt) and o‐bromostyrene (oBrSt) [P(pBrSt‐co‐oBrSt)] with partially sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) have been studied by differential scanning calorimetry (DSC). For an SPPO of given degree of sulfonylation, a miscibility window in terms of the isomeric composition of the brominated copolymer was seen; the location and width of the window was a function of sulfonylation. In general, copolymers with a higher content of pBrSt exhibit miscibility with SPPOs with higher degrees of sulfonylation. Upon annealing to temperatures of 280° and 320°C, only small changes in the miscibility regime were observed. The miscibility behavior was analyzed on the basis of the mean‐field theory in terms of the individual segmental interaction parameters. © 1994 John Wiley & Sons, Inc.
Effects of processing parameters and molecular weight distribution on the tensile properties of polypropylene fibers
Authors: Andreassen Erik , Myhre Ole Jan , Hinrichsen Einar L. , Grøstad Kristin
Published: April 2003

The tensile properties of polypropylene fibers, produced in a short‐spin line, are correlated with the parameters of the three processing stages (spinning, drawing, and annealing), and with the molecular weight distribution. In general, tensile stiffness and strength increase with increasing molecular orientation, while the elongation at break decreases. The degree of orientation is determined by the deformation ratios and temperatures of the first two stages. Tensil modulus and strength also increase with increasing annealing stage shrinkage ratio. All the tensile properties, including the elongation at break, increase with increasing average molecular weight. The mechanisms of crystallization and deformation are related to the molecular weight distribution in different ways. Hence, the tensile modulus is highest for broad distributions when the draw ratio is low, and for narrow distributions when the draw ratio is high. The tensile strength increases and the elongation at break decreases as the width of the molecular weight distribution decreases, for all combinations of processing parameters. The distribution of tensile strength, for fibers with high draw ratios, broadens as the molecular weight distribution narrows. The total draw ratio of fibers, as experienced during processing and testing, and the true stress at break, are discussed in terms of deformation rates and relaxation times. © 1994 John Wiley & Sons, Inc.
ESR studies of molecular motions at the interphase region of a blendlike polymeric material
Authors: Pekcan Önder , Demir Yusuf , Güven Olgun
Published: April 2003

The molecular motions of spin probes at the interphase region of poly(methyl methacrylate) particles sterically stabilized by polyisobutylene (PIB) were studied by ESR spectroscopy. The correlation times (τ) were measured by using the methods of Freed and Kivelson. Activation energies for different modes of motion were calculated at wide temperature range between −140 and 140°C. Viscosities were estimated in methanol saturated PIB channels in the polymer particles. © 1994 John Wiley & Sons, Inc.
Direct electrodeposition of thin‐layer (phenylene–carbazolylene) copolymers
Authors: Aboulkassim A. , Faid̈ K. , Chevrot C.
Published: April 2003

Thin (phenylene–carbazolylene) copolymer films of controlled composition can be directly deposited onto solid cathodes such as indium tin oxide (ITO) glass or glassy carbon through a dehalogenative polycondensation of 4,4′‐dibromobiphenyl and 3,6‐dibromo‐N‐alkylcarbazole mixtures in the presence of an electrogenerated zero‐valent nickel catalyst. The electrochemical and optical properties of the resulting thin films have been studied. The electrochemical behavior reveals two distinct electronic states that depend on the copolymer composition and structure. The first electronic state is characterized by either only one redox process, attributed to the presence of phenylene‐disubstituted carbazolic units in the case of copolymers with the highest proportion of phenylene, or two successive redox processes, attributed to the occurrence of a radical cation and dication of carbazolic diades, in the case of copolymers with the lowest proportion of phenylene. The second electronic state shows in all cases a single redox system occurring at a higher potential than the first state and due to phenylene moieties in the copolymer. All the electrodeposited copolymer films were found to be reducible in the same manner as pure poly(p‐phenylene). © 1994 John Wiley & Sons, Inc.
Structure and dielectric properties of poly(vinyl chloride) thermoplastic elastomer blends
Authors: Radhakrishnan S. , Saini D. R.
Published: April 2003

The structure, development, morphology, and dielectric relaxation have been investigated in poly(vinyl chloride)–thermoplastic elastomer (copolyester–ether) blends having different compositions. The changes in the intensities of dielectric relaxation peaks for the β and γ processes with respect to blend composition have been found to be associated with corresponding changes in crystalline structure and morphology of the elastomeric component. The critical composition for observing such modification of properties is about 50% of poly(vinyl chloride) above which the blend becomes almost amorphous. © 1994 John Wiley & Sons, Inc.
Rheological behavior and thermal stability of poly(phenylene sulfide)/vectra‐B950 blends
Authors: Valenza A. , La Mantia F. P. , Minkova L. I. , De Petris S. , Paci M. , Magagnini P. L.
Published: April 2003

Blends of polyphenylene sulfide (PPS) with a commercial, wholly aromatic, liquid crystalline polymer (LCP), Vectra‐B950, have been prepared by melt‐blending. Their rheological behavior has been studied in order to determine if the LCP displays a processing aid ability, and under what conditions it gives rise to potentially reinforcing fibrils dispersed in the PPS matrix. The problem of the thermal stability of PPS/LCP blends, which has been considered by some authors as the main obstacle to the production of usable materials due to the evolution of gaseous substances during processing, has been discussed. © 1994 John Wiley & Sons, Inc.
Physical modification of polyacrylonitrile precursor fiber: Its effect on mechanical properties
Authors: Wang P. H. , Liu J. , Li R. Y.
Published: April 2003

Polyacrylonitrile precursor fiber of a special grade for making carbon fibers was modified by stretching in the prestabilization stage to various extents. The effect of such stretching on tensile properties of the original precursor fiber, intermediate (oxidized) fiber, and resultant carbon fiber prepared through a continuous process was monitored. Improvements in tensile modulus of fibers at various stages were observed with increasing stretch ratios. However, no obvious enhancement of tensile strength of final carbon fibers was found. © 1994 John Wiley & Sons, Inc.
Estimation of sphere‐size distributions in two‐phase polymeric materials from transmission electron microscopy data
Authors: Gleinser W. , Maier D. , Schneider M. , Weese J. , Friedrich Chr. , Honerkamp J.
Published: April 2003

The blending of two immiscible polymer samples can lead to spherical inclusions of one component in a matrix of the other component. The mechanical solid‐state properties as well as the flow behavior of the m+lt depend on the size of the spheres in the blend. For that reason, the sphere‐size distribution is of major interest. Information about this distribution is often obtained by analyzing thin slices of the blend with transmission electron microscopy. In that way, however, the sphere‐size distribution itself is not obtained. The reconstruction of the sphere‐size distribution is introduced as a stereological problem, well known in fields as metallurgy, biology, geology, and medicine. It is shown that the sphere‐size distribution can be reconstructed using a regularization method as implemented in the program FTIKREG. © 1994 John Wiley & Sons, Inc.
Electron‐beam‐initiated grafting of triallyl cyanurate onto polyethylene: Structure and properties
Authors: Chaki Tapan K. , Roy Sanjoy , Despande R. S. , Majali A. B. , Tikku V. K. , Bhowmick Anil K.
Published: April 2003

Electron‐beam (EB)‐initiated grafting of triallyl cyanurate (TAC) onto polyethylene (PE) has been carried out over a range of radiation dose (2–20 Mrad) and concentrations of TAC (0.5–3 parts by weight). The grafting level, as determined from IR spectroscopy, is maximum at a 10 Mrad radiation does using 1 part TAC. With increasing TAC level at a 15 Mrad dose, the grafting level is higher only after 1.5 parts TAC. The gel content increases with radiation dose in the initial stages. X‐ray studies indicate two peaks at 10.6–10.8° and 11.7–11.9° and the corresponding interplaner distances of 4.15 and 3.80 Å. With increase in radiation dose or TAC level, the crystallinity decreases in the initial stage and then increases. It shows a decreasing trend again at higher radiation dose. The interplanar distance or the interchain distance of the modified polymer does not change. However, the crystallite size increases initially and then decreases. The tensile properties are relatively insensitive to the variation of radiation dose because of the interplay of various factors. The dielectric loss, tan δ, shows a maximum at a 10 Mrad dose and minimum at 5 and 15 Mrad due to changes of polarity and the carrier mobility. © 1994 John Wiley & Sons, Inc.
Unusual effect of filler (CaCO3) on thermal degradation of polyurethane
Authors: Dolui S. K.
Published: April 2003

The thermal degradation of polyurethane is exothermic in nature. The addition of CaCO3 inverts the exothermicity to endothermic behavior in the presence of air. © 1994 John Wiley & Sons, Inc.
Linear polythioesters. XXII. Products of interfacial polycondensation of bis(4‐mercaptomethylphenyl)sulfide with some aliphatic and isomeric phthaloyl dichlorides
Authors: Podkościelny Wawrzyniec , Rudż Wiesław
Published: April 2003

New polythioesters were obtained by interfacial polycondensation of bis(4‐mercaptomethylphenyl) sulfide with some aliphatic and isomeric phthaloyl dichlorides. To determine optimal conditions for polycondensation, the polythioester from bis(4‐mercaptomethylphenyl) sulfide and sebacoyl dichloride was chosen as a model system. The influence of some factors on the reduced viscosity and the yield were studied. Polythioesters from aliphatic and isomeric phthaloyl dichlorides were prepared under the same optimal conditions as those established for the reaction of the dithiol with sebacoyl dichloride. The structure of all polythioesters was determined by elementary, infrared spectra, and X‐ray analysis. Initial decomposition temperature and maximum rate of decomposition temperature were defined from the curves of thermogravimetric analysis. Some physicochemical, mechanical, and electrical properties have been determined. © 1994 John Wiley & Sons, Inc.
Photodegradation of polyethylene films formulated with a titanium‐based photosensitizer and titanium dioxide pigment
Authors: Angulo‐Sanchez J. L. , Ortega‐Ortiz H. , Sanchez‐Valdes S.
Published: April 2003

This work reports on the photodegradation of low‐density polyethylene films formulated with titanium (IV) oxide actylacetonate (TAc) and titanium dioxide pigment in different proportions; no previous reports on the photoactivity of this acetylacotonate have been found. Samples of blow‐extruded films were submitted to accelerated UV aging with fluorescent lamps and the polymer degradation measured. The changes in carbonyl groups, molecular weight, and film elongation at break are discussed. The results show that TAc can promote photooxidation and accelerate the film degradation. The retention percent of elongation at break (EB) is apparently proportional to the carbonyl index irrespective of the formulation but has different relations with molecular weight (Mn), time, or the number of chain scissions (n), probably as a result of microstructural differences. © 1994 John Wiley & Sons, Inc.
Graft copolymers of methy methacrylate onto canna starch using manganic pyrophosphate as an initiator
Authors: Gao Jian‐Ping , Tian Ru‐Chuan , Yu Jiu‐Gao , Duan Meng‐Lin
Published: April 2003

In this article, the graft copolymerization of methy methacrylate with canna‐starch under the initiating of manganic pyrophosphate was investigated systemly. It was found that the percentage of grafting, grafting efficiency, and rate of grafting were all dependent, to some extent, on the concentration of the initiator, monomer and starch, as well as reaction time and temperature. The rate equation of graft copolymerization established from the experimental results was similar to the equation derived from the reaction mechanism. The graft copolymer was investigated with an infered spectroscope, scanning electron microscope, and x‐diffraction methods. © 1994 John Wiley & Sons, Inc.
Graft copolymerization of 2‐hydroxyethylmethacrylate onto chitosan films and their blood compatibility
Authors: Singh D. K. , Ray Alok R.
Published: April 2003

This article examines the blood compatibility of chitosan grafted with 2‐hydroxyethyl‐methacrylate (HEMA) using 60Co gamma radiation. The effect of various syntheses conditions on the grafting was determined. The solvent composition has a marked effect on the degree of grafting. Maximum yield was obtained in an equivolume mixture of a water–methanol system. The percent grafting increased with the increase in the monomer concentration up to 20 vol % in a total dose of 0.216 Mrad. The percent grafting was found to be higher at a lower dose rate for a constant total dose of 0.216 Mrad. The swelling of grafted chitosan films decreased on increasing graft level. The grafted copolymers showed improved blood compatibility as compared to original chitosan sample. © 1994 John Wiley & Sons, Inc.
Kinetics of crazing in polybutadiene/polystyrene blends
Authors: Spiegelberg Stephen H. , Argon Ali S. , Cohen Robert E.
Published: April 2003

The crazing behavior of blends of polystyrene (PS) and a low molecular weight polybutadiene (PB) was examined as part of a continuing study of toughening mechanisms in thermoplastic polymers. These PS/PB blends attain high levels of toughness from the stress‐activated plasticizing action of the polybutadiene (PB), a mechanism that is active only in the region of a growing craze. The plasticization is therefore localized and leads to enhanced toughness without loss in stiffness. The net result of this plasticization is a reduction in craze flow stress accompanied by an increase in craze velocity, which, in turn, allows the specimen to reach substantial strains‐to‐fracture in uniaxial deformation under an imposed strain rate. The ability of the PB to plasticize a growing craze is expected to be a function of the mobility of the PB. To investigate the role of diluent mobility, tensile tests and craze velocity measurements were conducted at −20°C and compared with previously published results collected at 23°C. Although the blends displayed high levels of toughness at 23°C, the blends tested at −20°C showed brittle behavior. Craze velocities measured at −20°C were 2 orders of magnitude lower than the results at 23°C. Addition of 3 wt % PB at −20°C led to craze velocities only as large as those found in pure PS at 23°C. Comparison of the craze velocities with an asymptotic theoretical model describing the dependence of the craze velocity on the PB content showed good agreement with the results at −20°C and only fair agreement with the room‐temperature results. © 1994 John Wiley & Sons, Inc.
Polymerization of acrylonitrile using magnetron deposition technique
Authors: Shirodkar V. S. , Jathar R. T. , Bapat A. M. , Kulkarni S. D. , Bhat N. V.
Published: April 2003

Polymerization of acrylonitrile (PAN) in a capacitively coupled glow discharge under magnetic enhancement was studied. The design aspects of a magnetron electrode and its characteristics are described. The study suggests that an improved magnetron design helps in achieving a higher monomer conversion ratio that improves the quality of films and allows the use of lower system pressure. Thin, uniform, pinhole free films of PAN having very high molecular weight were formed. © 1994 John Wiley & Sons, Inc.
Determination of interfacial tensions for latex particles
Authors: Durant Yvon G. , Sundberg Donald C. , Guillot J.
Published: April 2003

The possibility of measuring in situ the interfacial tension at the monomer‐swollen polymer‐water interface of synthetic latices is considered in detail. Experimental measurements of certain liquid or vapor phase properties of the latex can, in principle, yield values of the desired interfacial tension. This technique requires the evaluation and comparison of the Flory–Huggins term and the Morton term of the thermodynamic expression for the chemical potential of the monomer in the latex particle. While each term can be evaluated, it turns out that the relative magnitudes of the two terms are such that unrealistically high precision is required in the experimental measurements for this technique to be useful for obtaining reasonably accurate interfacial tensions. At saturated swelling conditions with highly surface‐active emulsifiers (e.g., sodium dodecyl sulfate), the interfacial tension values obtained have a precision of only about ±50%. The reliability of these approximate values degrades rapidly as one moves away from saturation conditions, so as to render in situ experimental techniques inappropriate for gaining accurate knowledge about the surface energy at the latex particle–water interface at any monomer–polymer ratio. © 1994 John Wiley & Sons, Inc.
Synthesis and characteristics of organic soluble photoactive polyimides
Authors: Ho Bang‐Chein , Lin Yeh‐Sen , Lee Yu‐Der
Published: April 2003

Soluble aromatic polyimides with inherent viscosities of 0.23–0.50 dL/g have been synthesized from 2,2‐bis(3‐amino‐4‐hydroxyphenyl) hexafluoropropane (BAPAF) and various aromatic tetracarboxylic dianhydrides. Almost all polyimides were soluble in a wide range of organic solvents, i.e., acetone, m‐cresol, N,N‐dimethylacetamide, N,N‐dimethylformamide, N,N‐dimethylsulfoxide, N‐methyl‐2‐pyrolidone, methyl ethyl ketone, and tetrahydrofuran (except that polyimide deriven from 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride). Synthesized polyimides have a glass transition temperature in a range of 293 to 355°C, showing no appreciable weight loss up to 400°C in both air and nitrogen. These soluble polyimides exhibit high transparency in the UV visible region, with water absorption being between 3.6 to 5.7 wt %. They provide an aqueous base developable positive photoresist system when formulated with diazonaphthoquinone sensitizer. On the other hand, negative photoactive polyimides which are soluble in common organic solvents and optically transparent at a light of 365 nm wavelength, being obtained by reacting these soluble polyimides with methacryloyl chloride. Properties and characteristics of both positive and negative photoactive polyimides have been studied here. © 1994 John Wiley & Sons, Inc.
Selectivity as a function of membrane thickness: Gas separation and pervaporation
Authors: Koops G. H. , Nolten J. A. M. , Mulder M. H. V. , Smolders C. A.
Published: April 2003

In this article, the pervaporation selectivity as a function of the membrane thickness is studied for the dehydration of acetic acid. From this study, it appeared that the selectivity of polysulfone (PSF), poly(vinyl chloride) (PVC), and polyacrylonitrile (PAN) decreases with decreasing membrane thickness, below a limiting value of about 15 μm. However, in the case of gas separation, the selectivity of PSF membranes is independent of the membrane thickness. This phenomenon could not be explained by a difference in membrane morphology, sorption resistance, thermodynamic interaction, or coupling. It is believed that the decrease in selectivity for thin membranes has to be attributed to defects induced during pervaporation. These defects, crazes (and cracks), result from a reduced value of the critical strain, due to sorption of acetic acid/water and stresses between the polymer chains, due to a concentration gradient across the membrane. © 1994 John Wiley & Sons, Inc.
A numerical prediction of peak area in loss factor for polymers
Authors: Ogawa Toshio , Yamada Takuto
Published: April 2003

We tried to correlate the polymer constitutes with the peak areas under tan δ–temperature curves, which are abbreviated as TA (loss tangent area) hereafter. TAs for homopolymers were obtained as the summation of ratio of contributions for functional groups in addition to the constant. TAs for semicrystalline polymers decreased with increase of the degree of crystallinity. Therefore, TAs for semicrystalline polymers were estimated from the ratio of the contribution of functional groups and crystallinity. TAs for copolymers were obtained by adopting the idea of mole ratio. Thus, the predicted values were fairly good in agreement with the measured ones for almost all kinds of linear polymers adapted in this study. © 1994 John Wiley & Sons, Inc.
Transesterification of ethylene vinyl acetate copolymer in a modular intermeshing corotating twin screw extruder with different screw configurations
Authors: Kim Pan Jong , White James L.
Published: April 2003

The transesterification of ethylene‐vinyl acetate (EVA) copolymer to produce ethylenevinyl alcohol copolymer (EVAL) was studied in both a batch reactor and in a modular corotating twin screw extruder with various screw configurations. Increasing the number of left‐handed screw elements and kneading disc blocks increases the extent of conversion under any set of operating conditions. Conversion is increased by decreasing screw speed and reducing throughput. Reactor design models have been developed to represent the modular twin screw extruders. These use a drag flow reactor for screw elements, a continuous stirred tank reactor (CSTR) to represent kneading disc blocks and a plug flow reactor to represent post screw and die regions. Comparison are made with experiment. © 1994 John Wiley & Sons, Inc.
Determination and correction of peak broadening in size exclusion chromatography of controlled rheology polypropylene
Authors: Lederer K. , Beytollahi‐Amtmann I. , Billiani J.
Published: April 2003

The peak broadening in size exclusion chromatography of seven commercial polystyrene (PS) standards with narrow molar mass distribution (MMD) and of 6–9 polypropylene (PP) fractions (M̄w/M̄n = 1.34–2.10) obtained by direct extraction was determined in four different column sets. The dependence of the Gaussian peak broadening parameter, σ2, on the peak elution volume was different for PS and PP. For a commercial grade of controlled rheology PP (CR‐PP) (Daplen PT55) with M̄w/M̄n < 3 it was shown that disregard of the peak broadening effect leads to considerable errors in the MMD at low and higher molar mass and in the polydispersity parameter M̄w/M̄n. The same lot was studied in an Austrian National Research program for its physical propeties in processing and application and in a round‐robin test of IUPAC working party IV.2.2. on molecular characterization of commercial polymers. © 1994 John Wiley & Sons, Inc.
Preparation of anti‐oil stained membrane by grafting polyethylene glycol macromer onto polysulfone membrane
Authors: Iwata Hiroo , Ivanchenko Maria I. , Miyaki Yoshiyuki
Published: April 2003

In this study, anti‐oil stained ultrafiltration membrane was prepared by grafting a polyethylene glycol diacrylate macromer onto a plasma‐activated polysulfone membrane. The macromer formed a hydrate layer which prevented oil in emulsion from directly contacting the membrane surface, thus preventing the oil from staining the membrane. © 1994 John Wiley & Sons, Inc.
Preparation and properties of poly(vinyl acetate)/silica‐gel microhybrids
Authors: Yano Shoichiro , Nakamura Kensuke , Kodomari Mitsuo , Yamauchi Naofumi
Published: April 2003

Poly(vinyl acetate) (PVAc) was incorporated into silica gel using the sol–gel process involving tetraethoxysilane (TEOS). In order to prepare silica‐gel microhybrids, two different processes were employed, and the physical properties of the resulting two sets of hybrids were compared. In the first method, PVAc was first mixed with TEOS in an acetone solution and then cured using HCI and H2O. In the second method, an acetone solution of a copolymer composed of vinyl acetate (VAc) and vinyl triethoxysilane (VTES) was first mixed with TEOS and then cured. This copolymer contained 10 mol % of VTES component and was bound covalently to silica‐gel molecules. When comparing the properties of the hybrids, the dynamic modulus, E′, increased with increasing amounts of TEOS over a wide temperature range: −20–120°C. E′ of a hybrid from PVAc was lower than that of a hybrid from the VAc/VTES copolymer. A sharp peak in the loss modulus, E″, of a PVAc hybrid occurred at 40°C, and its position did not change with TEOS content. In contrast, the E″, peak of a copolymer hybrid was broad and its position also shifted to a higher temperature as the TEOS content increased. The tensile strength of a PVAc hybrid increased as the amount of mixed TEOS increased, reaching a maximum of 30 MPa at 50 wt % of TEOS. However, the strength of a copolymer hybrid reached a maximum of 50 MPa at 50 wt % of TEOS. The differences in the physical properties between a PVAc hybrid and a copolymer hybrid arise from the difference in their structure. Organic polymer molecules in a copolymer hybrid combine covalently with silica‐gel molecules through the VTES component, while a PVAc hybrid has no bounding between PVAc and silica‐gel molecules. © 1994 John Wiley & Sons, Inc.
Modifying acrylic‐based superabsorbents. II. Modification of process nature
Authors: Omidian H. , Hashemi S. A. , Askari F. , Nafisi S.
Published: April 2003

This article is devoted to the synthesis, characterization, and modification of acrylic‐based superabsorbents which are synthesized by inverse suspension and solution polymerization techniques. Distilled and saline water absorbency of these hydrogels and the effects of varying process nature on their absorbency characteristics (capacity and rate) are graphically discussed. © 1994 John Wiley & Sons, Inc.
Improvement of jute fiber through ultraviolet‐cured films of urethane acrylate
Authors: Ali K. M. Idriss , Uddin M. K. , Bhuiyan M. I. U. , Khan Mubarak A.
Published: April 2003

Formulations were developed with urethane acrylate in combination with different monomers. The role of plasticizers used as coadditives in the formulations was investigated. Physical and mechanical properties of the UV‐cured films were studied. Hessian cloths made with jute fibers were coated with these formulated solutions and cured under UV radiation. Though plasticizers decrease the tensile properties of the UV‐cured films, but they substantially enhance both tensile strength by 80% and elongation of the coated hessian cloths by more than 300%. Uptake of water and moisture at different relative humidity conditions decreases significantly by the hessian cloths when coated with these formulations. © 1994 John Wiley & Sons, Inc.