bluuebunny/crossref_metadata_2025 huggingface dataset:
Hard elastic behavior in polyurethane foams
Authors: Kau C. , Huber L. , Hiltner A. , Baer E.
Published: April 2003

Hard elastic behavior is characterized by high porosity and high recoverability from large strain, and initial Hookean elasticity was discovered in polyurethane foams containing styrene–acrylonitrile (SAN) copolymer particles. The presence of SAN particles introduces a heterogeneous morphology, and when the foam was strained in the SEM, it was observed that the struts became highly porous with profuse voiding nucleated by the SAN particles. It was found that these flexible polyurethane foams had a similar morphological structure in the strained struts as did the typical hard elastic materials. The phenomenon of stress depression, when foam specimens under stress were subjected to nonswelling liquids, was utilized to probe the role of surface stress in these hard elastic foams. An analytic methodology established for other highly porous hard elastic materials based on stress depression was utilized to obtain the average distance between voids in the struts. The calculated values were in good agreement with direct scanning electron microscopy observations, confirming that voiding initiated at the boundaries of SAN particles.
Dynamic light‐scattering studies of poly(γ‐benzyl α, l‐glutamate)–benzyl alcohol system
Authors: Shukla Premal , Muthukumar M. , Langley Kenneth H.
Published: April 2003

We report the concentration and temperature dependencies of the diffusion coefficients obtained from dynamic light‐scattering studies for the poly(γ‐benzyl α, l‐glutamate)‐benzyl alcohol (PBLG–BA) system. These studies were made at dilute and semidilute polymer concentrations, mainly in the isotropic phase. The measured translational and rotational diffusion coefficients in dilute solutions are consistent with predictions based on wormlike chain models. The mutual diffusion coefficient in semidilute solutions shows a marked deviation from scaling predictions, demonstrating the strong coupling between the translational and rotational motions. The measured time evolution of the scattered intensity after the PBLG–BA system is suddenly quenched into the gel phase demonstrates that aggregation is a significant mechanism in the formation of the gel phase.
Chemical modification of dialysis membrane based on poly(acrylonitrile–methylmethacrylate–sodium vinylsulphonate)
Authors: Godjevargova Z. , Dimov A. , Petrov St.
Published: April 2003

Poly(acrylonitrile–methylmethacrylate–sodium vinylsulphonate) membranes were subjected to modification with a view to improve their dialysis properties. Hydroxylamine and diethylaminoethylmethacrylate were used as modifying agents. As a result of the modification, nitrile groups depending on the modifying agent were partially converted to primary amine, oxime, and tertiary amine groups. The newly formed functional groups provide the membrane more hydrophvlic properties and the permeability of the membranes substantially increases. The appearances of the NH2 and oxime groups were identified by IR spectroscopy. The primary as well as tertiary amino groups were determined quantitatively by potentiometric titration. The pore size distribution of the initial as well as modified membranes were compared. The mentioned modifying agents appeared to be very prospective to improve the dialysis characteristics of the ter‐PAN membranes.
Invariant kinetic parameters of polymer thermolysis. IV. Influence of fire‐retardant additives on polypropylene thermolysis
Authors: Vyazovkin S. V. , Bogdanova V. V. , Klimovtsova I. A. , Lesnikovich A. I.
Published: April 2003

Analyzing the transformation‐degree dependence of the effective activation energy, we have studied the thermolysis gross kinetics of polypropylene (PP)‐based fire‐resisting composition and a synergetic mixture of fire‐retardant additives: antimony oxide and hexabrominecyclododecane (HBCD). The addition to PP of individual HBCD and in a mixture with antimony oxide increases the activation energy at the initial stage of thermolysis, which is attributed to the ability of fire‐retardant additives to impede destruction initiated by oxidation. The investigation of the process proceeding in PP prior to the onset of decomposition in the presence of fire‐retardant additives has shown that these additives stimulated crosslinking of polymer chains. The addition to PP synergetic mixture gives the greatest—compared to its individual components—content of the crosslinked fraction (10%), whose presence is likely to inhibit the proceeding of thermolysis by the oxidation mechanism.
Structure and physical properties of epoxide‐treated tussah silk fibers
Authors: Tsukada Masuhiro , Goto Yoko , Freddi Giuliano , Matsumura Masaaki , Shiozaki Hideki , Ishikawa Hiroshi
Published: April 2003

The structural characteristics and physical properties of epoxide‐treated tussah silk fibers from Antheraea pernyi silkworm are discussed in relation to the increasing weight gain values. Ethyleneglycol diglycidylether (E) and glycerin diglycidylether (G) were used as modifying agents. The noticeably high weight gain values (about 140%) obtained were attributed to the catalytic effect of SCN− anion absorbed by the fibers during the pretreatment under reduced pressure conditions. The amino acid analysis showed that epoxide G exhibited a slightly higher reactivity toward tyrosine, while arginine preferably reacted with epoxide E. The peak of loss modulus (E″) determined by dynamic viscoelastic measurements became broader and its position linearly shifted to lower temperature when the weight gain increased, and a minor peak appeared in the low‐temperature region below 50°C. Differential scanning calorimetry (DSC) thermograms showed that the position of the decomposition peak of modified silk fibers shifted to lower temperature with increasing weight gain values. The minor and broad endothermic peaks, appearing in the reference sample at about 234 and 290°C, disappeared by epoxide treatment. X‐ray diffraction patterns of tussah silk fibers suggested that the epoxide treatment does not affect directly the crystalline regions but causes a decrease of molecular orientation in the amorphous regions. Both briefringence (Δn) and isotropic refractive index (niso) of tussah silk fibers decreased by the reaction with epoxides, although with different rate and extent, confirming the decrease of average molecular orientation. The extent of decrease of strength and elongation depends on the kind of epoxide and on the weight gain value. Epoxide‐treated tussah silk fibers did not show significant changes of surface characteristics as the weight gain values attained up to 60%.
Kinetic studies on anaerobic initiated polymerization
Authors: Smith J. D. B.
Published: April 2003

Using a model reaction system consisting of cumene hydroperoxide, N,N‐dimethyl‐p‐to‐luidine and O‐benzoic sulfimide in toluene solvent (without reactive acrylic monomer), attempts have been made to understand the initiation mechanism operating during anaerobic polymerization. In these studies, the instrumental techniques of visible spectroccopy (VS), high performance liquid chromatography (HPLC) and infrared spectroscopy (IR) were employed.

Valuable kinetic data have been obtained using these three instrumental techniques. HPLC studies have shown conclusively that the N,N‐dimethyl‐p‐toluidine (N,N‐DMpT) component is significantly depleted during the initiation step of the anaerobic process. By way of contrast, the benzoic sulfimide (BS) concentration was found to be essentially unchanged during initiation.

Visible spectral changes with the model anaerobic solutions indicate that the initiation mechanism may involve radical‐ionic species derived from N,N‐DMpT rather than free radical reactive intermediates. Increasing the acidity of the reaction solution, with addition of acetic acid, appears to accelerate the initiation rate under anaerobic conditions.
Inhibition of deterioration of plastics by hydroaromatics
Authors: Kubo Junichi
Published: April 2003

Based on our previous works concluding that the addition of hydrogen‐donating hydroaromatics is effective in inhibiting the deterioration of hydrocarbons, heavy hydroaromatics from petroleum (HHAP) that were produced by hydrogenating highly aromatic heavy oil containing partly hydrogenated condensed aromatic rings were examined by the addition to high‐density polyethylene (PE), isotactic polypropylene (PP), and poly(vinyl chloride) (PVC, MW: 1300) after confirming its prominent hydrogen‐donating ability. The following results were obtained by the deterioration tests and melt‐flow tests: (1) Clear inhibiting effects could be found on preservation of elongation and tensile strength by the addition of 0.1% and 0.5% of HHAP to PE. (2) Cross‐linking of PE was restricted by the addition of HHAP. (3) Obvious effects could be found on preservation of elongation and tensile strength by the addition of 0.5% of HHAP to PP, but 0.1% of HHAP was not so effective. (4) Melt‐flow rate of PP at 270°C supported the results of the deterioration tests at 120°C. (5) Color changes were remarkably improved by the addition of HHAP to PVC (at 160°C, 140 min). From these results, hydrogen donation from hydroaromatics can be considered effective in inhibiting the deterioration of PE, PP, and PVC.
Surface properties of polymethylenediamine‐fixed styrene/acrylic acid copolymer latex
Authors: Tamai H. , Kiyota H. , Suzawa T.
Published: April 2003

Surface charge density, ζ‐potential, and dispersion stability of polymethylenediamine (PMD)‐fixed styrene/acrylic acid copolymer [P(St/AA)] latex were investigated. PMD‐fixed P(St/AA) latices are amphoteric and have isoelectric points at pH 4–7. Though the flocculations were observed at neutral pH, the pHs where the flocculation rates were maximum are slightly higher than were the isoelectric points. This result suggests the influence of the expansion of PMD‐fixed polymer layer surrounding the particles on the flocculation. The fixation of PMD to the surface of P(St/AA) latex lowers the dispersion stability for high electrolyte concentration.
Preparation of a plasma polymer containing phosphine complexed nickel by concurrent nickel evaporation
Authors: Morosoff N. C. , Clymer S. D. , Crumbliss A. L.
Published: April 2003

This article describes one of the first examples of concurrent metal evaporation and substituted hydrocarbon plasma polymerization as a general method for preparing thin films containing a metal coordinated to a plasma polymer. In this report, the evaporation of Ni into a triallylphosphine (TAP) glow discharge is described Deposition of a plasma polymer with concurrent reaction of Ni atoms with phosphine groups forms nickel containing triallylphosphine plasma polymer, NiTAPPP. The chemical nature of the product is derived on the basis of infrared spectra taken of the film as formed and after reaction with air, CO, and NO. The extent of the reaction is deduced from gravimetric data obtained during reaction with CO and with NO; each case was followed by evacuation of the gas. The CO gravimetric data also suggest that uncoordinated Ni is predominantly formed at high (Ni evaporation rate)/(plasma polymer deposition rate) ratios; coordinated Ni predominates at low values of this parameter. The ESCA spectra are also obtained for this plasma polymer (NiTAPPP) as well as for that described in the previous paper, in which TAP is plasma polymerized (yielding TAPPP) and subsequently reacted with Ni(CO)4 (TAPPP + Ni(CO)4). In both cases, it was found that Ni is oxidized on contact with air. After such air exposure, ESCA spectra reveal the presence of residual NiP moieties on the surface of TAPPP + Ni(CO)4, but not of NiTAPPP. This is attributed to the greater reactivity of the coordinatively unsaturated Ni sites postulated for NiTAPPP.
Removal and recovery of nickel ion in sodium citrate solution with chelating resin containing triethylenetetramine side chain
Authors: Maeda Hironori , Egawa Hiroaki
Published: April 2003

Removal and recovery of nickel ion in sodium citrate solution with the macroreticular chelating resin containing triethylenetetramine side chain was investigated. The resin (RMT) exhibited high affinity for nickel ion in a solution containing 100 mmol/dm3 of sodium citrate over the pH range of 7.4–11.5. The adsorption of nickel ion was above 98%. In the column method, the breakthrough capacity of the RMT for nickel ion was 3.0 g/dm3‐resin, when the solution containing 0.5 mmol/dm3 of nickel (II) nitrate and 100 mmol/dm3 of sodium citrate was passed through the RMT column at a space velocity of 7.5 h−1. The nickel ion adsorbed was eluted by allowing 1 mol/dm3 hydrochloric acid to pass through the column. The recycle of adsorption and elution was found to be satisfactory.
Self‐vulcanizable rubber blend system based on neoprene and carboxylated nitrile rubber
Authors: Mukhopadhyay Sujata , De Sadhan K.
Published: April 2003

A novel rubber blend system has been developed that is self‐vulcanizable. No rubber chemical was required for vulcanization, and the mixing operation could be completed in less than 14 min. Such a clean rubber blend system can be reinforced by carbon black filler, and physical properties are comparable to those of conventional rubber vulcanisates. Differential scanning calorimeter studies and dynamic mechanical analysis show that neoprene and carboxylated nitrile rubber are not miscible at the segmental level.
Solution of free radical polymerization
Authors: Venkateshwaran G. , Kumar Anil
Published: April 2003

The steady state approximation in free radical polymerization is known to break down during the operation of commercial reactors, in which case the unsteady mole balance of polymer radicals have to be solved numerically. We observed that the differential equations governing the zeroth, first, and second moments of polymer radicals in free radical polymerization are nonlinear in nature. The numerical solution of these is “stiff” because the concentration of polymer radicals is very small. Assuming an isothermal reactor, in the absence of the gel effect, these differential equations can be transformed in a suitable new domain where they are linear and can be solved analytically. We have subsequently developed a computer program for nonisothermal reactors in the presence of the gel effect using the analytical solution between any time increment. The results have been compared with those obtained from the fourth order Runge‐Kutta technique. We show that when the temperature changes are fast, the Runge‐Kutta technique cannot handle the stiffness, and the results begin to deviate from the exact solution. We find that our computer program is computationally efficient in handling this stiffness, takes considerably less time, and can be adapted to any personal computer.
Effect of microenvironment of oxirane groups on the immobilization of penicillin G acylase
Authors: Bahulekar R. V. , Ponrathnam S. , Ayyangar N. R. , Kumar K. K. , Shewale J. G.
Published: April 2003

Macroporous beaded terpolymers containing oxirane groups were synthesized for immobilization of penicillin G acylase. The effect of incorporation of various monomers such as hydroxyethyl methacrylate and methyl methacrylate, and the effect of crosslinking agents such as ethylene glycol dimethacrylate and divinyl benzene on binding and expression of penicillin G acylase were studied. The terpolymers were modified to varying extents by treating with polyethyleneimine. The influence of the microenvironment around the oxirane group on the binding and expression of penicillin G acylase was investigated.
Kinetics and mechanism of oligomerization of cardanol using acid catalysts
Authors: Manjula S. , Kumar V. G. , Pillai C. K. S.
Published: April 2003

The kinetics and mechanism of oligomerization of cardanol over acid catalysts were studied. GPC results showed the formation of a mixture of oligomers such as dimer, trimer, tetramer, etc. IR spectra of the products of oligomerization showed a decrease in the intensity of the double bond absorption band at 1630 cm−1 and the disappearance of terminal vinyl bands at 895 cm−1 and 907 cm−1. 1H NMR spectra showed drastic changes in the unsaturated proton resonance signals at 5.5δ with respect to saturated protons at 0.2–2.5δ. The ratio of resonance integrals of unsaturated to saturated protons decreased from 1 : 6.5 to 1 : 20 after oligomerization. GPC studies showed that the rate of formation of the dimer, trimer, tetramer, etc. follow an identical path and that the individual oligomers are formed in the same weight percentage at any time during the reaction. A kinetic scheme is proposed to explain this phenomenon. Kinetic studies showed that the oligomerization reaction follows first order kinetics with respect to the monomer concentration and the rate constant is K = 6.6 × 10−5s−1. A probable mechanism for the oligomerization of cardanol is proposed.
Determination of methylene bridge type of mixed meta and para‐cresol–formaldehyde novolaks by 13C‐NMR spectroscopy
Authors: Fitzgerald E. A. , Tadros S. P. , Almeida R. F. , Sienko G. A. , Honda K. , Sarubbi T.
Published: April 2003

Cresol–formaldehyde resins are important components of photoresists for semiconductor fabrication. The type of methylene bridge and relative amounts thereof are key structural features that determine resin properties. Several model compounds were prepared that represent the various types of methylene bridges that are possible from condensation of meta‐ and para‐cresol with formaldehyde. The methylene bridges were characterized by 13C‐NMR spectroscopy, and the assignments made were used to analyze spectra of cresol–formaldehyde novolak resin and several oligomer types. The effect of complexation with metal ion on the methylene bridge chemical shift was investigated for one oligomer. The effect of bridging position on the intramolecular hydrogen bonding of the phenolic hydroxyl group was investigated by infrared spectroscopy.
Thermal aging of impact‐modified polycarbonate
Authors: Cheng T. W. , Keskkula H. , Paul D. R.
Published: April 2003

Glassy polymers undergo relatively rapid physical aging just below their glass transition temperatures that can lead to embrittlement of normally tough materials like polycarbonate (PC). One approach for solving the embrittlement problem is to incorporate an impact modifier that can cause toughening when the matrix loses its inherent ductility due to physical aging. The effects of thermal aging below the glass transition temperature of polycarbonate on selected properties of blends of PC with various core‐shell impact modifiers have been studied. Observed changes in mechanical properties are related to rubber content, free volume, fracture morphology, discoloration, enthalpy relaxation, glass transition temperature, intrinsic viscosity, and dynamic mechanical behavior. Blend mechanical properties are affected by chemical changes in the impact modifier that occur simultaneous with the physical aging of the PC matrix. The degradation mechanisms involved reduce the effectiveness of the modifier for toughening and also lead to a loss of molecular weight of the PC matrix. Blends containing 10% methacrylated butadiene‐styrene (MBS) core‐shell impact modifiers give the maximum extension of time to embrittlement at 135°C in air. More thermally stable modifiers are required for further extending the ductile mode of failure for physically aged PC blends.
Graft copolymerization of butyl acrylate onto pullulan using manganic pyrophosphate as initiator
Authors: Tian R.‐C. , Gao J.‐P. , Yu J.‐G. , Duan M.‐L.
Published: April 2003

The graft copolymerization of butyl acrylate onto pullulan using manganic pyrophosphate as initiator in aqueous medium was studied. The effects of concentration of initiator, monomer, pullulan, and sulfuric acid on the percentage of grafting, the grafting, efficiency, as well as the rate of graft copolymerization were investigated. The rate equation was derived and a suitable reaction mechanism was proposed. Finally, the grafted samples were characterized by IR spectral measurement.
Acoustic emission in bonded elastomer discs subjected to compression. I
Authors: Kakavas P. A. , Chang W. V.
Published: April 2003

The apparent initial stiffness, M, of a rubber disc subjected to compression was experimentally determined. It was found that the experimental value of M is different than the value theoretically predicted according to Gent's equation. The aim of this study is to prove that this difference in the apparent modulus is due to the existence of microcavities within the testing rubber discs. The microvolds are formed along the curing process of the samples. A new nondestructive experimental technique, the Acoustic Emission (AE) technique, was used for the analysis of microcavitation within rubber discs subjected to compression. The count, event average count rate, amplitude, duration time, and rise time distributions of the received acoustic emission signals from the buckling of voids in the deformed solid, give more insight about the phenomenon of microcavitation.
Starch urea formaldehyde matrix encapsulation of solid agrochemicals. II. Release mechanism and release modeling
Authors: Kulkarni N. V. , Rajagopalan N. , Kale R. P. , Khilar Kartic C.
Published: April 2003

Based on experimental observation, a mechanism is proposed to describe the release of carbofuran from a starch‐UF matrix. A simple mathematical model is developed to describe the diffusion‐controlled release of a solid insecticide from a porous starch‐UF matrix undergoing both volume and surface erosions. The model is tested with the release data collected for different matrices and with different pH values of the environmental liquid. The comparison between the model predictions and data is found to be reasonably good. The model describes the release process at different pH values by accounting for the influence of pH on the erosion rates.
Plasma polymerization of metal acetylacetonates and application for gas sensor devices
Authors: Inagaki N. , Tasaka S. , Nozue Y.
Published: April 2003

Plasma polymerization of five metal acetylacetonates (MAcAc), aluminium acetylacetonate (AlAcAc), copper acetylacetonate (CuAcAc), titanium acetylacetonate (TiAcAc), zinc acetylacetonate (ZnAcAc), and magnesium acetylacetonate (MgAcAc), were investigated for the application of CO gas sensor devices. Plasma polymerization deposited thin films with metal elements as well as carbon and oxygen elements. The polymer deposition rate in the plasma polymerization was a function of the rf power, the system pressure, and the nature of the MAcAc. The elemental composition of the deposited films was fairly different from that of the starting materials, MAcAc. The complexing bonds of the MAcAc between acetylacetone and the metal element occurred in the plasma zone. The cleavage was closely related to the delocalization of electrons on the complexing of the MAcAc. The plasma polymer films prepared from TiAcAc and ZnAcAc in the presence of Pt catalyst showed a response toward CO gas. The plasma polymer films, especially prepared from TiAcAc, are potential materials for a CO sensor device with both sensitivity and selectivity.
Premembranes for porogen‐derived membranes and thermal decomposition of porogens
Authors: Eyal A. M. , Hazan B. , Hajdu K. , Edelstein D.
Published: April 2003

Various t‐butyl and di‐t‐butyl esters, N‐boc and di‐N‐boc amines, metal salts of N‐boc amino acid, and glycerol–formic acid esters are potential porogens for porogen‐derived membranes. Introduction of more than 20 such compounds into polysulfone or poly(vinyl chloride) films was studied. Transparency, IR spectra, changes in glass transition temperature, and differential scanning calorimetry were used to differentiate between molecular dispersion and formation of micro phases. The results show that for many of the studied additives more than 10% by weight can be practically molecularly dispersed in the polymers. The upper limit of porogen concentration in premembranes depends on characteristics of the polymer and of the porogen, on casting solvent composition, and on drying procedure. Metal salts of N‐boc amino acids were found to be suitable heat‐decomposable porogens. Their decomposition in premembranes proceeds in two stages, in the first of which 2 C4H8 + 2CO2 are released per salt molecule. The metal complex formed goes through decarboxylation at a higher temperature. A heating procedure for completion of the first decomposition stage and for avoiding the second was determined.
Characterization of natural polyisoprenes and synthetic polybutadiene
Authors: Vangani Veena , Rakshit Animesh Kumar
Published: April 2003

Synthetic polybutadiene (PBR) and natural rubbers from India (InR) and Guyana (GR) have been characterized in detail. The characterization includes IR, NMR, GPC, DSC, TGA, contact angle, and viscosity measurements. Spectroscopic characterization helped in the differentiation of InR and GR. Viscosity data is used in the evaluation of activation parameters at infinite dilution of the viscous flow. Viscosity data is also used for the determination of the conformation of the macromolecules in various solvents. Surface characterization confirms the total hydrophobic nature of the three rubbers. Thermal analysis shows different degradation pattern for natural rubbers than for the synthetic rubber.
The effects of functional azo initiator on PMMA and polyurethane IPN systems. III. Tear resistance and crack growth of PBD(1,2)‐PU/PMMA (50%) blends
Authors: Roha M. , Dong F.
Published: April 2003

The tear strength and crack growth mechanism of PBD(1,2)–PU/PMMA (50%) IPN systems were studied by the trouser tear test and single edge notched (SEN) tensile test. It was found that these blend systems showed similar structures and properties to particulatereinforced elastomers. The tear strength was dominated by the structure of the rubber matrix. The PMMA phase increased the tearing resistance by increasing the hysteresis of the IPN systems. Chemical bonding between the PMMA‐rich particle and PU‐rich matrix prepared by using a reactive azo initiator inhibited the initiation of the fracture nucleus, decreased the intrinsic flaw size, and increased the tear strength. The crack growth of these IPNs was dependent on both the fracture energy available for crack propagation and the hysteresis of the material. The similar structure of these two blends resulted in the similar crack growth behavior.
New results on the kinetic aspect of the permeation resistance of elastomers, using an original testing cell and methanol as model permeating fluid
Authors: Forte R. , Leblanc J. L.
Published: April 2003

This work describes a method developed to study the permeation of fluids through rubber membrane in a semiautomatic manner, in such a way that information regarding the complete process is obtained. Using this technique, several permeation parameters were assessed with fluoroelastomer and hydrogenated nitrile rubber membranes. A phenomenological model for the permeation process is proposed that includes two concomitant physical phenomena: the swelling of the membrane and the permeation itself. Simple mathematical relationships are derived from the experimental data, with the permeation rate as the key parameter.
Study of curative interactions in cis‐1,4‐polyisoprene. XI. Network maturing reactions in the cis‐1,4‐polyisoprene–sulfur–zinc dimethyldithiocarbamate and cis‐1,4‐polyisoprene–sulfur–zinc dimethyldithiocarbamate–ZnO systems
Authors: Kruger F. W. H. , McGill W. J.
Published: April 2003

The network maturing reactions of the inefficient cis‐1,4‐polyisoprene (IR)–sulfur–zinc dimethyldithiocarbamate (ZDMC) and IR–sulfur–ZDMC–ZnO vulcanization systems were discussed. The Moore–Trego efficiency E was exceptionally high and increased, for example, from 13.0 at 132.4°C to 49.9 at 170.0°C in the IR–sulfur–ZDMC mixture. Calculations showed that ∼ 60% of the elemental sulfur was combined in the network in the form of cyclic sulfides and/or vicinal crosslinks at 148.2°C. The inefficient use of sulfur at the initial cure stages may be attributed to the insolubility of ZDMC in rubber. The increase in E at the later stages of vulcanization was attributed to a decrease in the total number of polysulfidic crosslinks, as the number of mono‐ and/or disulfidic crosslinks remained constant. The destruction of polysulfidic crosslinks was enhanced in the absence of ZnO, due to the catastrophic attack of thiophilic species such as Me2NH. The Me2NH resulted from the rapid decomposition of dimethyldithiocarbamic acid, which formed as a by‐product in the initial crosslink reactions. No evidence was found for the participation of ZDMC in crosslink desulfuration. ZDMC is not a vulcanizing agent.
Synthesis and fluorescence properties of rare earth metal ion–polymer ligand–low molecular weight ligand ternary complexes
Authors: Wang Yunpu , Lei Ziqiang , Feng Hanyu , Bao Jiuntang , Wang Yaobin
Published: April 2003

Eu3+‐containing polymer ternary complexes were synthesized using different kinds of functional polymers such as poly(benzylmalonic acid styrene) (PBMAS), poly(benzylacetone styrene) (PBAAS), and poly(benzyl‐azo‐o‐hydroxybenzoic acid styrene) (PBAHBAS) as polymer ligands. The structures of the complexes were investigated by elemental analysis and IR spectroscopy. The fluorescence intensity of Eu3+–polymer–TTA (2‐thenoyltrifuoroacetone ion) complexes was decreased in the order PBMAS(61) > PBAAS(42) > PBAHBAS(32). In system of Eu3+–PBMAS–low molecular weight ligand, the emission spectrum shape, the fluorescence intensity, and the wavelength of the maximum emission peak were changed when the low molecular weight ligand was varied. The fluorescence intensity of the Eu3+–PBMAS–TTA ternary complex was 610 times stronger than that of the Eu3+–PBMAS binary complex and 160 times stronger than that of Eu3+–PBMAS–oxine complex. The fluorescence intensity of the Eu3+–PBAAS–TTA complex was enhanced greatly when the proper mol ratio of HTTA/Eu3+ and pH in the reaction were chosen.
Thermogravimetric determination of starch content in starch–polyethylene blend films
Authors: Nakatsuka S. , Andrady A. L.
Published: April 2003

Thermogravimetric analysis as a technique for rapid determination of starch content in LDPE/starch blend films was investigated. The percent weight loss in a specified temperature range, under a constant heating rate, correlated well with the starch content of films in the range of 0–12 wt % starch, as determined by chemical analysis. The method was used to estimate the residual starch content of LDPE/starch films, containing approximately 6.0% starch, exposed under several biotic exposure conditions. Generally 87–88% of the initial starch content was present in the films after different types of environmental exposures.
Enhanced reactivity of melamine–formaldehyde resins by fractionation. Crosslinking at ambient temperature
Authors: Samaraweera Upasiri , Gan Shubang , Jones Frank N.
Published: April 2003

A commercial hexakis(methoxymethyl)melamine (HMMM) resin was fractionated (1) by crystallization of the hexane–soluble fraction from hexane and (2) by partitioning the hexane–soluble and hexane–Insoluble fractions between alumina and various solvents. Crystallization afforded hexakis(methoxymethyl)melamine (1) of 90 to 95% purity. Partitioning afforded 12 fractions with altered proportions of polar and nonpolar species; the least polar fraction was spectroscopically and chromatographically similar to the crystallized material. Relative reactivities of certain fractions were estimated by 1H NMR studies of the rates of reaction with neopentyl alcohol in the presence of catalytic amounts of p‐toluenesulfonic acid (p‐TSA). It was found that the reactivity of fractions, rich in less‐polar species, was substantially greater than that of the commercial HMMM resin, whereas reactivity of fractions, rich in polar species, was less. Reactivity was especially enhanced by removal of all active hydrogen species, notably those containing NH groups. A practical consequence of this result was that fully formylated and alkylated melamine resins could crosslink with polyols at substantially lower temperatures than the commercial HMMM resin, which contained NH groups. Therefore, room‐temperature crosslinking was feasible.
Solution copolymerization of alkyl methacrylates and N–vinyl carbazole: Reactivity ratios
Authors: Ryttel Anna
Published: April 2003

The copolymerization of ethyl methacrylate and n‐butyl methacrylate with N‐vinyl carbazole was studied at 60°C, using AIBN as the initiator. The reactivity ratios of the monomers were determined in benzene, ethyl acetate, acetone or (N,N–dimethylformamide) solutions. The values of r1 and r2 were calculated by the Fineman–Ross and Kelen–Tüdös methods and were compared with those obtained earlier in bulk copolymerization.
Thermal conductivity of polyethylene/polystyrene blends containing SEBS block copolymer
Authors: Agari Y. , Ueda A. , Nagai S.
Published: April 2003

We measured the thermal conductivity of a polyethylene/polystyrene blend containing SEBS block copolymer, which has two components of polystyrene block and hydrogenated polybutadiene block, and discussed the effect of phase inversion on the thermal conductivity by observing the morphorogy of the blend. Further, we examined the applicability of the thermal conduction model for composites, which was proposed in our previous reports, to this blend system. By plotting the logarithm of the thermal conductivities of the blends vs. the weight content of polyethylene, it was found that the experimental data lie approximately on a straight line with an increase in polyethylene until the range of dual–phase continuity (phase inversion), and then the data move on another straight line beyond the range of dual–phase continuity. Thus, our model to explain the thermal conductivity of the polymer blend was proved. Further, both coefficients A and B in our model took linear relations with the weight content of the block copolymer, and the model was, thus, more strongly confirmed to be applicable to thermal conductivity of polymer blends.
Studies on the sorption of lipids in segmented polyurethanes. II. Effect of hard‐segment content
Authors: Sreenivasan K. , Jayabalan M. , Rao K. V. C.
Published: April 2003

Diffusion and absorption, of a few representative components found in blood, in segmented polyurethane are studied. The absorption of the components, confined to the soft segment, is found to be Fickian. Both diffusion coefficients and equilibrium absorption was found to decrease with % hard‐segment content. An empirical equation has been proposed to visualize the absorption behavior with soft/hard‐segment content.
Studies on semi‐interpenetrating polymer networks from poly(vinyl chloride‐co‐vinyl acetate) and poly(butyl acrylate)
Authors: Mathew Annakutty , Deb P. C.
Published: April 2003

A series of semi‐interpenetrating polymer networks (semi‐IPN) based on linear poly(vinyl chloride‐co‐vinyl acetate) and cross‐linked poly(butyl acrylate) were synthesized. The copolymer was swelled in butyl acrylate monomer containing azobisisobutyronitrile (AIBN) initiator and tetraethylene glycol dimethacrylate cross‐linker and later polymerized in situ. Variation in composition of the IPN was achieved by varying the copolymer/monomer ratio. The semi‐IPN was found to exhibit two distinct glass transitions as measured by differential scanning calorimetry and dynamic mechanical analysis. The tan θ values were found to be dependent on the composition. The tensile strength was found to be higher for semi‐IPNs containing a higher percentage of copolymer.
Influence of polymer characteristics and melt‐spinning conditions on the production of fine denier poly(ethylene terephtalate) fibers. Part I. Rheological characterization of PET polymer melt
Authors: Kiang Chang T. , Cuculo John A.
Published: April 2003

The rheological characterization of four poly(ethylene terephtalate) (PET) polymers, with viscosity average molecular weight ranging from 2.7 × 104 to 7.1 × 104, has been performed in the Instron capillary rheometer. The apparent elongational viscosity was obtained from the shear flow and entrance pressure data, following the methods proposed by Cogswell and Binding in contraction flow experiments. The PET polymers showed a tension thinning behavior in the deformation rate range of 300–3000 s−1 employed in this study. These results were explained on the basis of the network model. Polymers with similar behavior in shear may be distinct in elongational and may lead to distinct polymer processability. Polymers with lower apparent elongational viscosity level were shown to allow spinning of finer denier fibers, which is determined by the polymer spinnability.
Protein‐dispersed liquid crystals
Authors: Hermel H. , Seeboth A.
Published: April 2003

Nematic liquid crystals (LC) were embedded in a highly structured gelatin film as the discrete phase in the form of droplets. Thereby, the gelatin matrix forces a preferred orientation of the LC molecules in the droplets, initiated by the interaction between the triple helices of gelatin and the LC at the interface protein/LC. This is explained on a molecular level by the formation of a supramolecular structure at the interface, which is a germ for the continued preferred orientation of the mesogenes inside the droplets.
Polyurethane elastomers based on novel polyether macrodiols and MDI: Synthesis, mechanical properties, and resistance to hydrolysis and oxidation
Authors: Gunatillake Pathiraja A. , Meijs Gordon F. , Rizzardo Ezio , Chatelier Ronald C. , McCarthy Simon J. , Brandwood Arthur , Schindhelm Klaus
Published: April 2003

Novel polyurethane elastomers based on 4,4′‐diphenylmethanediisocyanate, 1,4‐butanediol, and polyether macrodiols that have 6, 8, or 10 methylene groups between the ether oxygens were prepared by two‐step solution polymerization. Their mechanical properties and degradation resistance were compared with poly(tetramethylene oxide)‐based polyurethanes. The new polyurethanes were more resistant to hydrolysis and to hydrogen peroxide‐induced oxidation than were the poly(tetramethylene oxide) ‐based materials. The poly(octamethylene oxide) ‐based polyurethane displayed good resistance to sodium hypochlorite. 1,2‐Diaminoethane chain‐extended polyurethane–ureas were also prepared using the macrodiols poly(hexamethylene oxide) and poly(octamethylene oxide). They were not thermally processable or solvent‐castable. Bulk synthesis of novel polyether polyurethanes yielded, in some cases, materials with improved mechanical properties compared with their solution‐polymerized counterparts. The outcome of the bulk syntheses was highly dependent, however, on reaction conditions and stoichiometry.
Polymerization of allyl esters derived from long‐chain fatty acids and palm olein
Authors: Gan L. H. , Ooi K. S. , Goh S. H. , Chee K. K.
Published: April 2003

Allyl esters of palm olein, palmitic, and oleic acids were synthesized by transesterification and esterification methods using KOH and absolute H2SO4 as catalysts, respectively. Three allyl esters, namely, allyl palmitate, allyl epoxystearate, and epoxidized allyl ester of palm olein, were successfully polymerized in the presence of t‐butyl perbenzoate at 120°C to obtain oligomers with the average number of backbone atoms approximately equal to the number of skeletal atoms of the long‐dangling side chains. The kinetic data of polymerization were conformed to the rate equation proposed by other workers. No oxirane cleavage was detected during the chain reaction. The melting behavior of these comb‐shaped polymers was compared with that of their respective allylic monomers. The polymer of epoxidized allyl ester of palm olein exhibits a glass transition temperature at 204.4 K. The critical molecular weights of the polymers of allyl esters investigated are predicted to be not lower than 104.
Effect of blending on the crystallization behavior of PET
Authors: Nadkarni V. M. , Shingankuli V. L. , Jog J. P.
Published: April 2003

The crystallization of poly(ethylene terephthalate) (PET) in its blends with other thermoplastics such as poly(phenylene sulfide) (PPS), high‐density polyethylene (HDPE), poly(methyl methacrylate) (PMMA), aromatic polyamide, and a co‐polyester is reported. The nonisothermal crystallization and melting behavior of PET in its blends has been discussed. Because of differences between the melting/softening points of these polymers and the melting point of PET, the crystallization of PET takes place in the presence of solidified PPS in PET/PPS blends and in presence of the molten phase of the second component in the remaining blends. The observed changes in the melting and crystallization behavior are explained on the basis of the effect of the physical state of the second component. The results of the isothermal crystallization studies are consistent with these studies. The changes in the overall crystallization rate could be further explained in terms of the nucleation and growth processes occurring during the crystallization of PET using the isothermal crystallization data.
Interaction of polyamic acids and polyamic esters with copper and substituted polysilsesquioxane copolymers
Authors: Linde H. G.
Published: April 2003

The interactions of biphenyldianhydride–p‐phenylenediamine (BPDA–PDA) polyamic acid and ester polymers with copper and copper‐treated surfaces containing polysilsesquioxanes formed from 3‐aminopropyltriethoxysilane (APS) (or copolymers of APS and phenyltriethoxysilane) were compared by grazing‐incidence infrared spectroscopy. This investigation of a flexible dianhydride–stiff diamine copolymer compliments earlier work using the stiff dianhydride–flexible diamine polyamic acid and ester of pyromellitic dianhydride–oxydianiline (PMDA–ODA). Results support earlier findings that amic acids form thermally labile salts on copper but esters do not. Further, while APS forms a copper‐interactive film that insulates amic acid/metal interaction, APS–phenylsilsesquioxane copolymers create an interfacial region interactive with both copper and overlying polyamic acid.
Effect of shear rheology on PVDC and PE blend permeation behavior
Authors: Kirkpatrick D. E. , Mclemore J. K. , Wright M. A.
Published: April 2003

The morphology of an immiscible polymer blend is dependent on the flow properties of the components and the deformation fields to which the mixture is exposed. The barrier properties of an immiscible blend is dependent on the barrier properties of the components and the morphological structure of the blend. Therefore, the resulting permeation rate of these blends is dependent on the rheology of the component materials. Conversely, the morphology of these blends can be studied by measuring permeation rates of a probe molecule. The oxygen permeation rate of vinylidenechloride copolymers blended with polyethylene changes abruptly over a small composition range. In the absence of significant extensional flow fields, this change is due to a phase inversion, and its position in the composition range is dependent on the shear rheology of the components.
Enzyme membrane based upon polyamide‐6 for oil hydrolysis
Authors: Ceynowa J. , Adamczak P.
Published: April 2003

This work presents the preparation of the enzyme membrane based upon polyamide‐6 (PA‐6) destined for the hydrolysis of oils. The transport properties of the base PA‐6 membranes, i.e., their porosity and permeability coefficients, as well as the mode of their modification, aimed at the chemical binding of lipase molecules have been estimated. © 1992 John Wiley & Sons, Inc.
Evaluation of particle dispersion in polymer solids by oxygen plasma etching
Authors: Yang A. C.‐M. , Allen R. D. , Reiley T. C.
Published: April 2003

A new technique using oxygen plasma etching was developed for studying the dispersion of filler particles in polymer solids. With this method, the organic polymer matrix is selectively etched from the top surface down into the bulk, revealing the dispersion state of the filler particles upon scanning electron microscopic analysis. A polymer composite, comprised of zinc oxide particles and a linear styrene‐n‐butylmethacrylate copolymer, was used to investigate the particle dispersion as a function of filler volume fraction. Preliminary data on the effect of a surfactant on filler dispersion is also discussed. © 1992 John Wiley & Sons, Inc.
Structural analysis of conveyor belts. II. Finite element approach
Authors: Parvini M. , Harandi J. N. , Kavousian A. , Soufian M.
Published: April 2003

The use of finite element analysis (FEA) in the design of a conveyor belt reduces the number of assumptions required in other methods. Although the problem is nonlinear (because of material property and geometry), a linear analysis produces comparable results. For handling the problem of large displacements, a prestrain method based upon a temperature gradient was used. The thickness of rubber interplies corresponding to minimum shear stress were determined for a number of three‐ply belts. © 1992 John Wiley & Sons, Inc.
Inverse gas chromatographic study of polymer blend interactions and their temperature dependence
Authors: Shi Z. H. , Schreiber H. P.
Published: April 2003

The temperature dependence of the thermodynamic interactions in blends of polypropylene and a fluorochemical was studied by inverse gas chromatography (IGC). A modified procedure has been proposed to evaluate the effective surface composition in polyblends. This shows that the low surface energy component preferentially concentrates in the surface region of blends. Moreover, the new procedure greatly reduces the probe‐to‐probe variation of χ23, a problem frequently encountered in thermodynamic applications of the IGC method. As a result, IGC may now be used with increased confidence for the determination of interaction thermodynamics in polymer systems over broad temperature ranges. © 1992 John Wiley & Sons, Inc.
New cation exchange composite based upon cellulose/melamine formaldehyde/citric acid reaction products
Authors: Ibrahim N. A.
Published: April 2003

A new cation exchange composite was synthesized through the reaction of cellulose with both melamine formaldehyde precondensate and citric acid. Factors affecting the reaction such as reactants' molar ratios, liquor ratio, time, and temperature were reported. Reaction conditions were selected to prepare a cation exchange composite having a carboxyl content of 120 meq/100 g and a nitrogen percent of 22.1. Potentiometric titration of this exchanger showed that it behaves like a tribasic acid, and the strengths, pKa, of each stage of ionization are 5, 6.7, and 9.7, respectively. Water solubility as well as durability to use of the prepared exchanger were evaluated. © 1992 John Wiley & Sons, Inc.
Flow‐induced on‐line crystallization of rodlike molecules in fiber spinning
Authors: Yarin Alexander L.
Published: April 2003

The micromechanical description of nonisothermal flow‐induced crystallization of a polymeric liquid with rodlike molecules is the main part of the fiber spinning model described here. Solutions of the governing equations show that an increase in winding velocity leads to the appearance of an on‐line flow‐induced crystallization zone in a fiber. This zone manifests itself in accelerated formation (necking) due to the release of heat of crystallization which results in the decrease of viscosity. Liquid crystallinity grows very rapidly in the necking region, which, in turn, leads to the growth of viscosity after some minimal value, which finally arrests fiber deformation.