bluuebunny/crossref_metadata_2025 huggingface dataset:
Permeability of silicone polymers to hydrogen
Authors: Bhide B. D. , Stern S. A.
Published: April 2003

Permeability coefficients, P̄, for H2 in 10 different types of silicone polymer membranes were measured in the temperature range of 10.0–55.0°C and at pressures up to 100 psig (∼6.8 atm). The values of P̄ decrease slightly with increasing Δp, the pressure difference across the membranes. The permeability of silicone polymers to H2 increases with an increase in temperature; the values of the energy of activation for permeation are in the range of 1.4–4.3 kcal/mol. The substitution of different functional groups in the backbone and side chains of silicone polymers has similar effects on the permeability of the polymers to H2 as observed in earlier studies with other light gases. P̄ for H2 decreases with an increase in the bulkiness of the substituted functional groups. The substitution of SiO bonds with stiffer SiC bonds in the backbone chains also results in a considerable decrease in permeability.
Plasma surface treatments on carbon fibers. II. Mechanical property and interfacial shear strength
Authors: Yuan L. Y. , Shyu S. S. , Lai J. Y.
Published: April 2003

Carbon fiber are surface treated by oxygen, argon, and styrene plasma to study the effects on fiber strength and interfacial shear strength with PPS resin. Interfacial shear strength between carbon fiber and high melting temperature thermoplastic resins is successfully measured with the microbond pull‐out test with the help of scanning CO2 laser beam which solved the difficulties in preparing PPS microspheres. Tensile tests show that etching by oxygen plasma and deposition with plasma–PS increase strength of the fibers in some cases. ESCA spectra deconvolutions demonstrate that the improved interfacial strength is strongly related to the hydroxyl, ether, or aromatic groups on the surface. On the other hand, hydrocarbon segments are detrimental to the interface. Surface area and roughness have little influences on the interfacial strength of carbon fiber/PPS composites.
A DSC study of curative interactions. IV. The interaction of tetramethylthiuram disulfide with ZnO, sulfur, and stearic acid
Authors: Kruger F. W. H. , McGill W. J.
Published: April 2003

The interaction of combinations of sulfur, tetramethylthiuram disulfide (TMTD), ZnO, and stearic acid were investigated by differential scanning calorimetry in the absence of rubber. TMTD decomposed partially to tetramethylthiuram monosulphide on liquefaction. Sulfur and TMTD reacted at vulcanization temperatures, and although the exact composition of all the products was not established, several features involving DSC and HPLC analysis were interpreted in terms of the formation of tetramethylthiuram polysulfides (TMTP). TMTD decomposed much faster to volatile products such as Me2NH, CS2, and CS when heated in the presence of stearic acid. Contrary to literature reports on the facile reaction of TMTD and ZnO to yield zinc perthiomercaptides (or zinc dimethyldithiocarbamate), the TMTD/ZnO reaction was found to be extremely sluggish under a variety of conditions. In the presence of sulfur, too, the TMTD/ZnO reaction was of negligible importance. It was inferred that several reactions occurred concurrently on heating a TMTD/stearic acid/ZnO system. These reactions were not observed for the sulfur/TMTD/stearic acid/ZnO mixture per se, but, instead, the stearic acid/ZnO reaction was very prominent. The formation of zinc stearate occurred at temperatures as low as 77°C in the quadruple system. TMTD and zinc stearate were virtually unreactive at vulcanization temperatures. None of the reactions involving ZnO could be attributed to the formation of a zinc perthiomercaptide, generally accepted to be a precursor in thiuram vulcanization.
Structures and properties of injection moldings of crystallization nucleator‐added polypropylenes. I. Structure–property relationships
Authors: Fujiyama Mitsuyoshi , Wakino Tetsuo
Published: April 2003

Flexural test specimens were injection‐molded from polypropylenes added with 0.5 wt % of calcium carbonate, talc, p‐tert‐ dibutyl‐benzoic acid monohydroxy aluminum, or p‐di‐methyl‐benzylidene sorbitol under cylinder temperatures of 200–;320°C. Properties such as flexural modulus, flexural strength, heat distortion temperature, Izod impact strength, hardness, and mold shrinkage and higher‐order structures such as crystalline texture, crystallinity, a*‐axis‐oriented component fraction, and degree of crystalline orientation were measured and structure–property relationships were studied. By the addition of crystallization nucleators, the flexural modulus, flexural strength, heat distortion temperature, hardness, and mold shrinkage were increased and Izod impact strength was decreased. The degrees of crystalline orientation such as the orientation fraction OF and c‐axis orientation function fc were increased by the addition of nucleators. The degree of the increase was higher as the crystallization temperature was higher. Close relationships were observed between some properties and the degrees of crystalline orientation.
IR and X‐ray diffraction studies of raw and chemically treated pineapple leaf fiber (PALF)
Authors: Saha S. C. , Ray P. K. , Pandey S. N. , Goswami K.
Published: April 2003

IR and X‐ray diffraction studies have been carried out on raw and chemically treated pineapple leaf fiber (PALF). The degree of crystallinity, as found by X‐ray diffraction and the crystallinity index as found by infrared methods, decreases on treatment with NaOH and NaClO2 solutions. The decrease of crystallinity with lower concentration of NaOH is attributed to the conversion of intermediate or semicrystalline regions to amorphous ones and with higher concentration to structural changes and with NaClO2 solution to the disorientation caused due to removal of cementing material lignin.
Graft copolymerization of vinyl monomers onto chitin with cerium (IV) ion
Authors: Kurita Keisuke , Kawata Mitsuo , Koyama Yoshiyuki , Nishimura Shin‐Ichiro
Published: April 2003

Graft copolymerization of vinyl compounds onto chitin was studied, and an efficient and reproducible procedure has been established, cerium (IV) being used as the initiator. The reactions with acrylamide and acrylic acid onto powdery chitin were carried out under various conditions to elucidate the polymerization behavior in terms of grafting percentage. The amount of cerium (IV) affected the polymerization most strikingly, and grafting percentages showed maxima with suitable amounts of initiator for both the monomers. As a solvent water proved to be superior to aqueous nitric acid except the reaction with a small amount of initiator. Under appropriate conditions, around 240 and 200% grafting percentages were achieved for acrylamide and acrylic acid, respectively. The resulting graft copolymers showed much improved affinity for solvents and hygroscopicity compared to the original chitin.
Streaming potential of microporous membranes made from homogeneously functionalized polysulfone
Authors: Hinke Ekkehard , Staude Eberhard
Published: April 2003

Microporous membranes were prepared from chemically modified polysulfone. The substitution of the polysulfone was performed in solution using reactions known from polymer modification such as halomethylation, aminomethylation, and lithiation. Membranes can be prepared directly from halomethylated polysulfones which are consecutively converted heterogeneously in a second step to the final functionalized form. Sometimes, two‐step reactions are necessary to yield the polymers from which the membranes were cast. In those cases where the reactions change the charge of the polymer, the success of the reaction can be demonstrated by streaming potential measurements. The advantage of this analytical method lies in the fact that the intact membrane is investigated.
The effect of molecular weight on the cross section and properties of polyacrylonitrile precursor and resulting carbon fiber
Authors: Tsai Jin‐Shy , Lin Chung‐Hua
Published: April 2003

In this study, we investigated the effect of molecular weight in the range 1.65−4.29 × 105 (Mw) on the cross section, surface, thermal, and mechanical properties of polyacrylonitrile (PAN) precursor and its resulting carbon fiber. From the results, it can be seen that the molecular weight, with the same solid content of polymer, changes from 1.65 × 105 to 4.29 × 105 and the cross section of PAN precursor changes from a circular shape with no notable grooves surface to a been shape with a surface containing deep and straight grooves. PAN precursor with higher molecular weight has a higher onset of exothermic temperature and a higher peak temperature, but has a higher aromatization index (AI value) due to its thin and flat cross section, which causes rapid cyclization during oxidation. An increase in molecular weight results in an increase in crystal size and preferred orientation and a decrease in average pore diameter. This decrease can improve the mechanical properties of PAN precursor and its resulting carbon fiber.
Dynamic mechanical properties of polystyrene–polyurethane blends
Authors: Theocaris P. S. , Kefalas V.
Published: April 2003

Four polystyrene–polyurethane mechanical blends were prepared with 5, 10, 20, and 40% thermoplastic polyurethane, respectively. Their impact properties were compared with pure polystyrene and commerical types of impact polystyrene. The rheological properties of the blends were studied with DSC and dynamic mechanical spectroscopy. It was found that addition of softer polyurethane conglomerates embedded inside the polystyrene matrix, although increasing the toughness of the blend as expected from addition of the softer particulate, also increased the glassy region of the blends by shifting their Tgs to higher temperatures. A theory based on the interaction of phases was propounded explaining this phenomenon.
Fibers spun from blends of different molecular weights of polypropylene
Authors: Mahajan S. J. , Bhaumik K. , Deopura B. L.
Published: April 2003

Fibers spun from blends of small percentage of plastic grade polypropylene (HMPP) with fiber grade polypropylene (PP) are studied for drawing behavior. A factorial design of experiment is used for a two‐stage drawing process with variables, such as percent of HMPP component, first stage draw ratio and temperature, and second stage temperature. Optimization is carried out for breaking stress and modulus of drawn filaments. Breaking stress of up to 0.74 GPa and initial modulus of 7.34 GPa is possible by such an optimization process. These properties are observed for 6% HMPP blend composition. Heat setting of drawn filaments show little changes up to 140°C heat‐setting temperature. Large scale structural changes with rapid drop in mechanical properties is observed for 150‐160°C heat‐set samples.
The effect of additives, solvent type, and polymer concentration on macromolecule dimensions
Authors: Wood Hal , Sourirajan S.
Published: April 2003

An equation is derived to estimate the hydrodynamic volume occupied by a typical linear polymer molecule, knowing only the polymer molecular weight and concentration of polymer in the solution. This equation may be applied to solutions above a minimum polymer concentration. Accuracy of the equation is determined by comparing it to an established method of calculating macromolecule dimensions.

Above dilute solution conditions, the volume pervaded by a macromolecule is affected mainly by the polymer molecular weight and concentration of polymer in the solution. Chain dimensions are generally unaffected by the type of polymer, solvent, or additive in the solution.
Effect of plasma treatments on wettability of polysulfone and polyetherimide
Authors: Asfardjani K. , Segui Y. , Aurelle Y. , Abidine N.
Published: April 2003

Experimental results on plasma treatments of polysulfone and polyetherimide to improve the wettability of these polymers are presented. The plasma is characterized by optical emission spectroscopy. The wettability of the polymer surfaces were checked by contact angle measurements and ESCA is used to compare the surfaces before and after plasma treatment. Correlations between contact angle, concentration of oxygen at the surface, and optical emission intensity of the OH radical have been established. Optimization of operational plasma parameters leading to the best wettability of the treated samples is reported.
Study on modified phenolic resin. I. Modification with homopolymer prepared from p‐hydroxyphenylmaleimide
Authors: Matsumoto A. , Hasegawa K. , Fukuda A. , Otsuki K.
Published: April 2003

We studied the improvement of heat resistance and mechanical properties of phenolic resin modified with polymers prepared from p‐hydroxyphenylmaleimide (HPMI). Homopolymers of HPMI and copolymers of HPMI with some vinyl monomers were synthesized and Mn Tg and thermal decomposition temperature of them were measured by GPC, DSC, and TG, respectively. The miscibility of homopolymer with novolac was examined by DSC. It was found that the homopolymer had good heat resistance and good miscibility with novolac. Molding compounds were prepared by hot roll‐kneading the mixtures of novolac, the homopolymer, hexamethylenetetramine, and glass fiber. It was found that molded test pieces had good heat resistance.
Zinc–Borate complex as flame‐retardant filler
Authors: Agrawal J. P. , Gupta D. C. , Khare Yogesh , Satpute R. S.
Published: April 2003

Water‐insoluble complexes have been prepared by reaction of boric acid, pentaerythritol, and metal salts i.e., acetates of zinc, cadmium, mercury, copper, nickel, cobalt, and manganese. The composition of these complexes has been established by determining metal content and by elemental analysis, and structural aspects have been studied by far‐IR spectra. The heat‐resistance data indicate that the zinc–borate complex is better than other metal‐borate complexes, and, therefore, it has been selected for detailed study. The effect of 10‐60 parts of zinc‐borate complex on novel unsaturated polyester‐7 (II) in respect of gel time, exotherm peak temperature, tensile strength, % elongation, nitroglycerine absorption, and flame retardance has been studied, and results have been discussed. Further, the zinc–borate complex also gives a synergistic effect in combination with antimony trioxide similar to other metal oxide fillers.
Development of potentially degradable materials for marine applications. II. Polypropylene‐starch blends
Authors: Gonsalves K. E. , Patel S. H. , Chen X.
Published: April 2003

The effect of exposure of unstabilized polypropylene‐starch blends, with or without a metal catalyst (e.g., cobalt (III) acetylacetonate), autooxidant (e.g., fatty acid), and a metal containing plasticizer (e.g., aluminum stearate) to the marine environment was studied for about six weeks at two different locations in New Jersey. Starch tends to absorb water. Unstabilized polypropylene degrades significantly during processin in air, as indicated by melt index values. Thus, for blends of unstabilized polypropylene‐starch (no additives), prepared under controlled conditions and exposed to plain seawater, there seems to be no microbial activity or chemical degradation, as indicated by no surface erosion and practically no change in molecular weight and tensile properties. However, for unstabilized polypropylene starch blends containing metal catalyst, auto‐oxidant, or plasticizer exposed under soft mud, surface erosion due to microbial activity is evident. In addition, chemical degradation due to the presence of degradative additives has been confirmed, as observed by a decrease in molecular weight and tensile properties. Changes in thermal characteristics of these blends after exposure to the marine environment have been studied.
Wet spinning of solid polyamic acid fibers
Authors: Dorogy William E. , St. Clair Anne K.
Published: April 2003

Recent research at the NASA Langley Research Center has involved the production of polyamic acid fibers from resins derived from the reaction of 3,3′,4,4′‐benzophenonetetra‐carboxylic dianhydride and 3,3′‐diaminobenzophenone or 4,4′‐oxydianiline in N,N‐dimethylacetamide. Resins were extruded into aqueous solutions of ethylene glycol, ethanol, or N,N‐dimethylacetamide in order to induce filament formation. These filaments were then washed in water and dried using air or vacuum ovens. Fractured fiber ends were examined using an optical or scanning electron microscope for the presence of macropores, termed voids. Coagulation bath concentration and composition, resin inherent viscosity, resin % solids, and filament diameter were studied to determine their effect on the production of solid core fibers.
The thermal oxidative degradation of an ethylene–tetrafluoroethylene‐copolymer‐based electrical wire insulation
Authors: Morelli John J. , Fry Charles G. , Grayson Michael A. , Lind Arthur C. , Wolf Clarence J.
Published: April 2003

A multidisciplinary spectroscopic evaluation of a commercial wire insulation based on a cross‐linked copolymer of ethylene and tetrafluoroethylene (X‐ETFE) was conducted to determine the chemical changes taking place during thermal aging. These studies provided insight into the roles of the various additives, such as triallylisocyanurate (TAIC) and antimony oxide, in the formulated X‐ETFE insulation. During irradiation processing, a large fraction of the TAIC is converted to a cross‐linked isocyanurate moiety; the unconverted TAIC is released during aging. Thermal aging of the X‐ETFE wire insulations was performed in air at 200°C for up to 5 months and resulted in oxidation of the base ETFE, loss of unreacted TAIC, and a small amount of dehydrofluorination. The antimony oxide serves the multiple roles of flame retardant and scavenger for the pyrolytically generated hydrogen fluoride.
Low‐pressure polymerization of ethylene. II
Authors: Pandya M. V. , Lata K. V.
Published: April 2003

This paper presents the kinetic study of polymerization of ethylene with VOCl3 and aluminum alkyls such as Et3Al and Et2AlCl. The effect of various parameters like the [Al]/[V] ratio, catalyst concentration, reaction time, temperature, solvents, and additives on rate of the reaction, yield, and molecular weight is reported. Each of these parameters has a remarkable effect on the yield and the rate of polymerization for both catalyst systems. Triethylamine is found to increase the catalyst efficiency and the rate. It is also observed that aliphatic hydrocarbons acted as a better polymerization medium than did the aromatic ones.
Polyurethane membranes from polyether and polyester diols for gas fractionation
Authors: Pegoraro M. , Zanderighi L. , Penati A. , Severini F. , Bianchi F. , Cao Nanyun , Sisto R. , Valentini C.
Published: April 2003

Polyurethane prepolymers were prepared in ethylacetate from TDI and poly(oxypropilene)glicols) (PE‐PU) or poly(tetramethyleneglycoladipate)diols (PES‐PU) of different molecular weights (M). Homogeneous membranes were prepared by spreading the pre‐polymer solution added with a three, four or pentafunctional crosslinking agent, in the presence of stannous octoate as a catalyst. On increasing M, the PUs Tg decreases regularly in the range +30 to −47°C. PU's are amorphous with the exception of PES‐PU obtained from highest M polyester diols. Permeability P, diffusivity D, solubility coefficient S of N2, O2, CO2, CH4, CO were measured at T=35°C (>Tg).P, D, S do not depend on the crosslinker functionality, but mainly on M. P and D in PE‐PU are linear function of T‐Tg while in PES‐PU the function is not linear. Gas solubility fulfills in general the regular solution theory. P, D, S of water vapor is also given. Permeability decreases in the order H2O>CO2 > O2 > CH4 > CO > N2. Some practical application based on particular selectivities is suggested.
Peculiarities of phase and supermolecular structure of graft copolymers of polycaproamide with poly(methacrylic acid)
Authors: Rŭbtsov A. E. , Matv̆eev V. V. , Chălykh A. E. , Smirnova N. V. , Gabrielyan G. A. , Gal'Braikh L. S.
Published: April 2003

The structure of graft copolymers of PCA with PMAA obtained by the methods of chemically initiated liquid‐phase grafting polymerization has been investigated with the use of electron microscopy, electron‐probe microanalysis, and X‐ray radiography. The concentration profiles of the graft copolymer distribution along the fiber cross section and diffusion coefficients of the monomer solutions correlated with the kinetics of the graft layer penetration inside the polymeric matrix have been determined. The concentration profile of the graft polymer distribution has been shown to have drops down to the zero level. Grafting proceeds both in the amorphous regions and on the surface of imperfect crystals. The structure of the graft layer, in which the segregated chains of graft PMAA constitutes the dispersed medium and the PCA inclusions represent the dispersed phase, has been found to be heterogeneous.
Kinetics and mechanism of the thermal decomposition of potassium persulphate ions in aqueous solutions at 50°C in the presence of nitrogen gas and methacrylonitrile monomer
Authors: Guchhait Sukumar , Banerjee Monoranjan , Konar Ranajit Singha
Published: April 2003

The initial rate of persulphate (I) decomposition at 50°C in the presence of nitrogen and methacrylonitrile (MAN) in an unbuffered aqueous solution (pH 4–7) may be written as:

in the concentration ranges of persulphate (I) (0.25–2.50) × 10−2 (m/dm3) and of (MAN) 0.18–0.36 (m/dm3). During the reaction, a white substance (polymethacrylonitrile) separates out in the colloidal state or in the precipitate form from the medium depending on the ionic strength of the medium. The pH of the medium was found to decrease rapidly and continuously with time in the absence of methacrylonitrile, but it decreased slowly and continuously with time in the presence of the monomer, MAN. If an additional quantity of MAN is injected late in a run, the rate of persulphate decomposition is further accelerated in a given run. However, the rate of persulphate decomposition is found to decrease continuously in the presence of MAN with time, i.e., as the monomer is converted to polymer. It is suggested that MAN accelerates the decomposition of persulphate ions, due to the following reactions in the aqueous phase:

and

where (Mj˙)w is a‐water soluble oligomeric or polymeric (j = 1–10) free radical. The estimated values of k5 and k10 are 1.05 × 10−5 and 1.14 × 103 (in dm3/m/s), respectively.
Structure effect on water diffusion and hygroscopic stress in polyimide films
Authors: Jou Jwo‐Huei , Huang Rita , Huang Peir‐Teh , Shen Wen‐Ping
Published: April 2003

A bending‐beam technique has been used to in situ monitor the diffusion of water in various polyimide films. The polyimides studied are pyromellitic dianhydride‐4.4′‐oxydianiline (PMDA–ODA), pyromellitic dianhydride‐p‐phenylenediamine (PMDA–PDA), and 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride‐p‐phenylenediamine (BPDA–PDA), and their blends and random copolymers. The diffusion of water in these films obeys Fick's law. In PMDA–ODA, the mean diffusion constant is 5.2 ± 0.4 × 10−9 (cm2/s) for thicknesses ranging from 6.7 to 27.3 μm. In PMDA–PDA, it is 2.0 ± 0.4 × 10−9 (cm2/s) for thicknesses ranging from 7.3 to 20.0 μm, and in BPDA–PDA, 0.27 ± 0.02 × 10−9 (cm2/s) for thicknesses ranging from 4.8 to 21.0 μm. In the blends and random copolymer with 50 wt % PMDA–ODA and 50 wt % PMDA–PDA, the diffusion constants are slightly smaller than those in the pure PMDA–ODA, but much larger than in the pure PMDA–PDA. On the contrary, in those with 50 wt % BPDA–PDA and 50 wt % PMDA–PDA, the diffusion constants are much smaller than those in the pure PMDA–PDA, but slightly larger than in the pure BPDA–PDA. These diffusion constants are primarily affected by the chemical structure of the imide molecule. The morphology, such as crystallinity, of the films has played a secondary factor. Hygroscopic stresses due to water uptake in all the studied films increase as the film thickness increases. It can be attributed to that the film orientation decreases with the increase of thickness.
A dispersed anisotropic phase as the origin of the weak‐gel properties of aqueous xanthan gum
Authors: Carnali J. O.
Published: April 2003

Xanthan gum is a water‐soluble, extracellular polysaccharide that has gained widespread commercial use because of its strong pseudoplasticity and tolerance to high ionic strength. It possesses a rigid, rodlike structure and has been reported to form weak gels at concentrations on the order of 0.5%. The nature of these weak gels has been explored using creep measurements and dynamic mechanical spectroscopy. The usual weak gel symptoms are found in 0.02N KCl at xanthan levels exceeding 0.8% and include deviations from the Cox‐Merz rule (η* > η), onset of weak power‐law dependence of the loss and storage moduli, and appearance of unusually long relaxation times. We have also detected an apparent yield stress for concentrations beyond 0.8%. However, concentration‐independent relaxation times and a slip/stick behavior during extended flow runs also marked the weak gel region and suggested sample heterogeneity. This condition was confirmed by optical studies that showed samples in this region to consist of a nematic liquid crystalline phase dispersed in an isotropic phase. The conclusion is made that the unusual rheological behavior of xanthan can be traced to the occurrence of this phase separation. Possible mechanisms for the formation of the anisotropic phase are also discussed.
Grafting. IV. Graft tercopolymers as antifouling resin
Authors: Deb P. C. , Sankholkar S. C.
Published: April 2003

A graft tercopolymer CLR‐g‐(MMA–TBTMA) based on chlorinated rubber as the backbone and binary copolymer of methyl methacrylate and tributyltin methacrylate as grafted chains has been synthesized. This graft copolymer has been used for the formulation of controlled‐release antifouling paints, and leaching rate behavior of toxin from such paints has been studied. The data have been compared with those obtained using controlled‐release antifouling paint based on linear chain copolymer of methyl methacrylate and tributyltin methacrylate. The paint based on grafted copolymer is characterized by having a lower leaching rate and reduced time for attainment of steady‐state leaching. Raft exposure studies indicate longer antifouling life compared to that of linear chain copolymer‐based paint both having the same dry paint film thickness.
Drag‐reduction efficiency, shear stability, and biodegradation resistance of carboxymethyl cellulose‐based and starch‐based graft copolymers
Authors: Deshmukh S. R. , Sudhakar K. , Singh R. P.
Published: April 2003

Graft copolymers of carboxymethyl cellulose and starch with polyacrylamide have been synthesized by grafting acrylamide onto carboxymethyl cellulose and starch, respectively, using a ceric‐ion‐initiated solution polymerization technique. These graft copolymers have been tested for their drag‐reduction effectiveness, shear stability, and biodegradability. It has been shown that grafting enhances the drag‐reduction effectiveness and shear stability and also that these factors are very much dependent on the length and number of grafts in the molecule. None of the graft copolymer solutions shows any microbial degradation up to 10 days.
Effect of oxidized carbon black on the mechanical properties and molecular motions of natural rubber studied by pulse NMR
Authors: Asai Shigeo , Kaneki Hiromune , Sumita Masao , Miyasaka Keizo
Published: April 2003

The mechanical properties such as elastic modulus and stress‐relaxation and spin‐spin relaxation time T2 from pulse NMR were measured for surface‐oxidized carbon‐black‐filled natural rubber. The extent of reinforcement increased with CB volume percent in the range of 0–30%. At a given CB percent, this quantity increased by surface oxidation of fillers and decreasing filler size. From pulse NMR experiment, it was found that there were three components in rubber molecules which have different values for T2. Stress‐relaxation time and elastic moduli fitted one master curve against effective volume, fraction which is the sum of filler and bound rubber fraction. It was found that the distance between particle surfaces is the most important factor influencing reinforcing properties of filled polymers.
Effect of stirring on morphology and properties in a catalyst cured epoxy system
Authors: Wu Ching‐Shiun
Published: April 2003

This article describes the effect of stirring on epoxy network morphology and physical properties. Several different mechanical stirrer speeds, from 45 rpm to 800 rpm, were employed for the mixing of diglycidyl ether of bisphenol A resin with 2‐ethyl‐4‐methyl imidazole catalytic curing agent. The investigation indicated that the glass transition temperature, room temperature density, low temperature relaxation, tensile mechanical properties in the rubbery state, and nodular morphology are significantly affected by the stirrer speed used. Transmission electron microscopy has revealed that the extent of homogeneity for the dispersion of nodule domain in the low crosslinking matrix improved with increasing stirrer speed. However, an optimum stirrer speed condition is needed for achieving the most homogeneous system. In addition, it is shown that the room temperature tensile mechanical properties are independent of the mixing condition. This independence is ascribed to the fact that the glassy state mechanical properties are closely related to the intermolecular forces rather than to the network structure.
Photoelectronic properties of iodine‐incorporated poly(N‐vinylcarbazole) films
Authors: Hu J. , Kao K. C.
Published: April 2003

Iodine was incorporated into poly(N‐vinylcarbazole) (PVK) films by exposing the films to saturated iodine vapor at 100°C for 10 h. The content of iodine in the films was 2.3% by weight. The films were stable at room temperature. The infrared spectra indicate that no chemical reaction has taken place during the incorporation process. The dark conductivity of these films is about two orders of magnitude greater than that of pure PVK films. Carriers can be photogenerated in the films by light illumination from the UV region to the entire visible region. The most significant feature of these films is that the photoconductivity has a peak at the photon energy of 1.8eV. This is attributed to the charge transfer from the carbazole to I2. The results of thermally stimulated currents (TSC) indicate that there are deep traps in pure PVK films, but after iodine incorporation, these deep traps disappear or are replaced by a large quantity of shallow traps.
Preparation and properties of UV‐autocurable BTDA‐based epoxy‐multiacrylate resins. Effects of the degree of polymerization and the epoxy type
Authors: Chiang Wen‐Yen , Chan Shao‐Ching
Published: April 2003

A series of UV‐autocurable epoxy‐multiacrylate resins was synthesized, and the effects of degree of polymerization (DP) and epoxy type on their properties were investigated. These autocurable multiacrylate resins possess good pot life and are cured rapidly when exposed to ultraviolet (UV) without the addition of photoinitiator or photosensitizer. The curing rate of the autocurable resins was probably dependent on the number of abstractable hydrogen in epoxy resins. Stress‐strain, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) were used to characterize the properties of cured multiacrylate resins. Increased crosslinking density of cured films improved tensile properties. Increasing the molar ratio of epoxy resin in the multiacrylate resins was found to decrease the effective acrylate concentration of resins and to depress crosslinking density of cured resins, which also resulted in an increased elongation at break but a decreased Young's modulus and breaking strength. Furthermore, the different structures of epoxy resins were used to give wide range properties of cured epoxy‐multiacrylate resins with a glass transition temperature (Tg range from 74 to 102°C. The film properties of the multiacrylate resins coated on steel plates were also investigated.
Gas transport in halogen‐containing aromatic polycarbonates
Authors: Hellums M. W. , Koros W. J. , Husk G. R. , Paul D. R.
Published: April 2003

The gas permeability and permselectivity of a series of halogen‐containing polycarbonates are discussed in terms of the fundamental solubility and diffusivity factors. These materials have structural features that hinder interchain packing and intrachain rotational mobility. Both diffusion and solubility coefficients are higher in materials with higher fractional free volumes. Diffusivity selectivities tend to increase with increasing restriction of intrachain torsional mobility. The materials with four bromine atoms substituted on the phenyl rings ortho to the carbonate linkages display a significantly increased diffusivity selectivity relative to conventional polycarbonate. This improvement in the ability of the polymer matrix to discriminate between gas molecules of different sizes is due to a reduction in intrachain torsional mobility. The reduction in chain mobility is indicated by higher glass transition and higher sub‐Tg transition temperatures in the bromine‐substituted materials. The materials with hexafluoroisopropylidene moieties have high fractional free volumes and exhibit a very significant increase in permeability relative to conventional bisphenol‐A polycarbonate. The material with both the hexafluoro and the tetrabromo substitutions displays significant simultaneous increases in permeability and permselectivity relative to conventional polycarbonate.
Polymer aqyeous solutions as quenching media. I. Polyvinylpyrrolidone
Authors: Louai Abderrahim , Pollet Gilbert , Francois Jeanne , Moreaux Francois
Published: April 2003

The cooling power of aqueous solutions of polyvinylpyrrolidone are studied with a silver standard sample by using two apparatuses quench with injection and quench with agitation. The dependences of the cooling rates at each temperature on polymer concentration and solution viscosity are established and empirical laws of variation are given.
The use of crossflow to improve nonwoven melt‐blown fibers
Authors: Milligan M. W. , Lu F. , Buntin R. R. , Wadsworth L. C.
Published: April 2003

A stream of unheated crossflow air has been used to make finer melt‐blown fibers. Not only are smaller average fiber diameters obtained, but the variation in fiber diameter is smaller. The use of this technique can allow the production of melt‐blown nonwovens, which have finer fibers and more uniform webs. Since unheated air is used in the crossflow jet, the fiber enhancement in terms of finer, stronger fibers can be achieved with an energy savings by substituting unheated crossflow air for a portion of the primary air.
Tensile properties of polypropylene/kaolin composites
Authors: Maiti S. N. , Lopez B. H.
Published: April 2003

Tensile properties of isotactic polypropylene filled with particulate kaolin fillers were evaluated in the composition range 0–60 wt % kaolin. Tensile modulus increased with filler concentration while breaking elongation and tensile strength decreased. The modulus increase was attributed to the restriction on the molecular mobility of the polymer imposed by kaolin particles. The decrease in elongation was also an effect of this restriction coupled with interference to stress transfer by the filler particles. Generation of discontinuity in the composite structure through formation of stress concentration points accounted for the tensile strength decrease. Morphology studies by SEM also indicated the introduction of stress concentration points by the presence of bare and nonadherent kaolin particles and their agglomerates with sharp edges in these composites.
A general equation in polycondensation
Authors: Changren Zhou
Published: April 2003

In polycondensation, we define F and f to be the true and effective average functionalities of the reaction system, respectively. The value of Q relates to the functionality and quantity of the nonbifunctional monomer. If there is monofunctional monomer in the reaction system, the value of Q may be less than 0. If the ring‐closure reaction in a system can be neglected, the relation among the molecular weight, the component of the reaction system, and the reaction extent of functional groups can be represented by the following equation: P = (F − Q − 2/xn)/f. The equation may be used in line, branching, and cross‐linking polycon‐densations without any restrictional conditions. According to Carothers, the gelation point Pc can be estimated by the following equation: Pc = (F − Q)/f. All relations among the molecular weight of the polymer, the component of the reaction system, and the reaction extent of the functional group can be replaced by the new equation. Only the Flory equation that is used to estimate Pc cannot be replaced by the new equation.
Carbonization behavior of polyimide films with various chemical structures
Authors: Inagaki M. , Ibuki T. , Takeichi T.
Published: April 2003

Six kinds of polyimide films with different molecular structures were synthesized and carbonized up to 1100°C. The carbonization behavior of polyimides was followed by measuring the changes in weight, size, and electrical conductivity. Pyrolysis gases evolved on the way to carbonize up to 1000°C were analyzed by gas chromatography.

All films showed appreciable shrinkage and became a black color above 500°C. No cracks and pores were observed on the films heated up to 1100°C, even under the scanning electron microscope. A large weight decrease of 35–50% was observed in a narrow temperature range from 500 to 650°C, which seemed to be due to the departure of CO groups as either CO or CO2. An additional weight decrease occurred gradually above 800°C, due to N2 departure. A remarkable increase of electrical conductivity along the film surface, more than 2 orders, was observed with the increase in heat‐treatment temperature. The polyimide film with a flat molecular structure (PMDA/PPD) gave the highest conductivity: 3.7 × 102S/cm.
Dielectric relaxation during isothermal curing of epoxy resin with an aromatic amine
Authors: Koike Tsuneo
Published: April 2003

The isothermal curing behavior of an epoxy resin system has been monitored by a dielectric measurement whose sensor consisted of a vertical parallel‐plate cell based on a three‐terminal method. The materials used in the isothermal cure were the diglycidyl ether of bisphenol‐A (DGEBA), which was purified from Epon 825 by recrystallization, and 4,4′‐diamino diphenyl methane (DDM). A dielectric relaxation was observed during each isothermal cure at temperatures of 70,80,90, and 100°C, which were below the glass transition temperature (Tg) of the reactive DGEBA–DDM system at the gel point. The relaxation is considered to be caused by the transformation from a liquid state to an ungelled glassy state as a result of an increase in molecular weight because gelation followed by a rubbery state did not exist in the temperature range studied. The dielectric relaxation for the DGEBA–DDM system fits the empirical model of the Havriliak–Negami equation. The Tg of the DGEBA–DDM system, which was estimated from the dielectric relaxation time, agreed with the one experimentally determined by differential scanning calorimetry (DSC).
Synthesis and properties of acrylonitrile‐EPDM‐4‐chlorostyrene graft copolymer
Authors: Park Duck‐Jei , Lee Neung‐Ju , Ha Chang‐Sik , Cho Won‐Jei
Published: April 2003

Graft copolymerization of acrylonitrile (AN) and 4‐chlorostyrene (4‐Clst) onto ethylene–propylene–diene terpolymer (EPDM) was carried out using benzoyl peroxide as initiator. The effects of EPDM content, initiator concentration, solvent, mole ratio of 4‐Clst to AN, reaction time, and reaction temperature on the graft copolymerization were examined. It was found that the light resistance, weatherability, and thermal stability of the acrylonitrile–EPDM–4‐chlorostyrene graft copolymer were considerably better than those of acrylonitrile–butadiene–styrene copolymer.
Pultruded fiber‐reinforced poly(methyl methacrylate) composites. II. Static and dynamic mechanical properties, environmental effect, and postformability
Authors: Ma Chen‐Chi M. , Chen Chin‐Hsing
Published: April 2003

This paper presents a novel process developed to manufacture poly(methyl methacrylate) (PMMA) pultruded composite. The mechanical, thermal, and dynamic mechanical properties, environmental effect, postformability of various fiber (glass, carbon, and Kevlar 49 aramid fiber) reinforced pultruded PMMA composites have been studied. Results show mechanical properties (i.e., tensile strength, specific tensile strength, tensile modulus, and specific flexural strength) and thermal properties (HDT) increase with fiber content. Kevlar fiber/PMMA composites possess the highest specific tensile strength and HDT, carbon fiber/PMMA composites show the highest tensile strength and tensile modulus, and glass fiber/PMMA composites show the highest specific flexural strength. Pultruded glass‐fiber‐reinforced PMMA composites exhibit good weather resistance. These composite materials can be postformed by thermoforming under pressure, and mechanical properties of postformed products can be improved. The dynamic shear storage and loss modulus (G′, G″) of pultruded glass‐fiber‐reinforced PMMA composites increased with decreasing pulling rate, and their shear storage moduli are higher than those of pultruded Nylon 6 and polyester composites.
Plasma polymerization of organoisothiocyanates. I. Characterization of deposition process and deposited materials
Authors: Czeremuszkin G. , Wróbel A. M. , Kryszewski M.
Published: April 2003

Thin polymer films were produced from methyl‐, n‐propyl‐, allyl‐, and phenyl isothiocyanates in an RF plasma, induced in an electrodeless flow system. The deposition rate of polymer film as well as its composition was found to be dependent on the substrate position in the reactor tube. The distinct effect of the monomer structure and the monomer saturated vapor pressure on the polymer deposition rate suggest a molecular nature for the plasma polymerization process and an important role for adsorption in the deposition process, respectively. The surface free energy data, evaluated by contact angel measurements, reveal the polar character of the organoisothiocyanate plasma polymers. The polar component of the surface appears to increase with the sulfur concentration in the polymer film.
Crosslinking of poly(vinyl chloride) with bismaleic compound. II. Rheological behavior and mechanical properties of crosslinked PVC
Authors: Zhou Dafei , Chen Minwei
Published: April 2003

In this study the rheological behavior of crosslinking PVC was studied. We carefully probed the effects of styrene and initiators on crosslink course and further verified PVC's crosslink mechanism suggested previously. St as auxiliary crosslinker was very important for PVC crosslink, no matter whether at lower temperature or at higher temperature, in the absence of initiator or in the presence of initiator. With higher decay temperature cumvl hydroperoxide (CHP) was a very appropriate initiator for PVC crosslinking. By controlling technological conditions, the crosslinked PVC with different cross density was obtained. We found that PVC with THF‐insoluble fraction of about 7% had the best tenacity and maximum breaking energy. The tensile strength would increase as the gel‐fraction content increased. By citing T. Kurauchi's ROF toughening theory, we satisfactorily explained the good ductility of crosslinked PVC with low cross density and the high fragility of over‐crosslinked PVC. Because the motion of segments is hindered in thoroughly crosslinked PVC, its glass transition was so weak that we hardly found out Tg.
Injection‐moulded blends of a thermotropic liquid crystalline polymer with polyethylene terephthalate, polypropylene, and polyphenylene sulfide
Authors: Seppälä Jukka , Heino Markku , Kapanen Camilla
Published: April 2003

The properties of various blends of a polyester‐type thermotropic liquid crystalline polymer (LCP) with polyethylene terephtalate, polypropylene, and polyphenylene sulfide were investigated. The polymers were blended in a twin screw extruder after which samples were injection moulded. The mechanical properties, morphology, and thermal properties of the blends are discussed.
Effect of molecular architecture on microstructural characteristics in some polysiloxaneimide multiblock copolymers
Authors: Samseth Jon , Mortensen Kell , Burns Janet L. , Spontak Richard J.
Published: April 2003

Efforts to correlate molecular characteristics with microstructural dimensions in microphase‐separated diblock and triblock copolymers have been very successful, resulting in relationships that can be utilized to design materials with a specific microstructure and, consequently, with particular thermomechanical properties. However, similar efforts in the arena of multiblock copolymers have not been nearly as extensive, despite the increasing interest and diversity of this class of materials. In the present work, energy‐filtered electron microscopy (EFEM) and small‐angle neutron scattering (SANS) are used in a complementary fashion to probe the phase behavior of a series of three polysiloxaneimide (PSI) multiblock copolymers with different molecular architectures. Despite their relatively short segment lengths, all three materials exhibit signs of microphase separation at ambient temperature. SANS data are obtained from chemically unaltered materials and are subsequently interpreted with the Teubner‐Strey model for microemulsions. Resultant microstructural dimensions are in good agreement with those measured from EFEM micrographs. Additional insight into the intramolecular sequencing of each copolymer is obtained from scaling relationships.
Mechanisms of antioxidant action: Nature of transformation products of dithiophosphates. II. Antioxidant action of thiophosphoryl disulphides
Authors: Al‐Malaika S. , Coker M. , Smith P. J. , Scott G.
Published: April 2003

The nature of transformation products of high‐temperature reactions of thiophosphoryl disulphides with hydroperoxides in the absence and presence of oxidisable substrates and the role of the disulphide in the overall antioxidant mechanism was investigated using a range of techniques such as oxygen absorption, 31P nuclear magnetic resonance (NMR), gas‐liquid chromatography (GLC), and peroxide determination. The major transformation products of the above oxidation reactions were found to be the thio and thiono‐phosphoric acids, in addition to mono and polysulphides. At high molar ratios of peroxide to disulphide (>10), these oxidation products are the main catalysts for peroxide decomposition, while at lower ratios the disulphide itself was found to play a major role in the antioxidant mechanism.
Deformation processing of PMMA into high‐strength fibers
Authors: Buckley C. A. , Lautenschlager E. P. , Gilbert J. L.
Published: April 2003

Poly(methyl methacrylate) was drawn into fibers by melt extrusion followed immediately by a transient temperature drawing process. By varying five processing variables, fibers ranging from 0.635 mm to 25 μm in diameter were produced. Heat‐induced relaxation of the aligned structure was used to determine the draw ratio of the resultant fibers and therefore the degree of polymer chain alignment imposed by the deformation process. The resulting changes in length and diameter were measured and it was found that draw ratios of 5–20 had been achieved under the varying processing conditions. It was also observed that fiber diameter immediately after drawing is a good predictor of the degree of orientation present in the fiber irrespective of the processing conditions. To test the effect molecular orientation has on material properties, fibers with varying degrees of orientation were tested in tension. As expected, increasing alignment resulted in increasing tensile strength. The maximum observed true ultimate tensile strength was 225 ± 53 MPa and was seen in fibers with a draw ratio equal to 18.7 ± 4.5. Fibers with a lower degree of alignment, while not as strong in tension, exhibited significantly increased ductility. True strains of as high as 25% were observed.