bluuebunny/crossref_metadata_2025 huggingface dataset:
Azobisisobutyronitrile‐Initiated graft copolymerization of methyl methacrylate onto poly(ethylene terephthalate) fibers
Authors: Saçak Mehmet , Bas̆tuğ Neriman , Talu Muzaffer
Published: April 2003

In this study, the grafting of methyl methacrylate onto poly(ethylene terephthalate) fibers using azobisisobutyronitrile is reported. An increase in temperature and monomer concentration were found to increase the graft yield. The graft yield increased up to an initiator concentration of 0.90 × 10−2 mol/L and decreased at higher initiator concentrations. The fiber densities decreased, and fiber diameters and intrinsic viscosities increased with increasing graft yield. Moisture regain values showed a slight increase with the grafting. Fiber orientation decreased the graft yield to an important extent. The overall activation energy for grafting was calculated to be 11.9 kcal/mol. © 1993 John Wiley & Sons, Inc.
Characterization of friction‐deposited polytetrafluoroethylene transfer films
Authors: Fenwick David , Ihn Kyo Jin , Motamedi Farshad , Wittmann Jean‐Claude , Smith Paul
Published: April 2003

The structure of oriented transfer films of poly(tetrafluoroethylene) (PTFE), previously used as orientation‐inducing layers for a variety of materials, was studied. Transmission electron microscopy and X‐ray diffractometry were empolyed to determine the continuity and relative volume of the PTFE films, which were deposited onto glass substrates by friction transfer at controlled temperatures, pressures, and sliding rates. The thickness and continuity of the films were found to increase with increasing temperature and applied pressure. In the range of sliding rates used (0.1–10 mm/s), no significant correlation between this processing variable and the thickness or continuity was apparent. Transmission electron microscope investigations showed that, generally, the (100) plane of the PTFE crystalline unit cell was parallel to the glass surface. © 1993 John Wiley & Sons, Inc.
Effect of polycarbonate molecular weight on polymer blends of polycarbonate and ABS
Authors: Wu Jiann‐Shing , Shen Shu‐Chen , Chang Feng‐Chih
Published: April 2003

The melt viscosity of polycarbonate/acrylonitrile‐butadiene‐styrene (PC/ABS) blends relative to PC is significantly lower, even lower than that of pure ABS in some compositions. Annealing above theTgof PC coalesces and coarsens phase structure in core and skin regions. Increase in the molecular weight of PC in PC/ABS blends results in low‐temperature fracture toughness improvement but suffers from the disadvantage of higher melt viscosity. The selection of PC in PC/ABS blends must be a compromise between the toughness advantages of higher PC molecular weight and the disadvantage of higher melt viscosity. © 1993 John Wiley & Sons, Inc.
Synthesis and properties of a new AB‐cross‐linked copolymer membrane system
Authors: Kerres J. A. , Strathmann H.
Published: April 2003

The alcohol permeability and permselectivity properties as well as the morphology of membranes made of a newly developed AB‐cross‐linked copolymer system composed of elastomeric and glassy components were investigated. The copolymer was synthesized by a hydrosilylation reaction between poly(styrene‐stat‐isoprenes) (Mn from 40,000 to 100,000 g/mol) with high content in unsaturated side groups (≈ 60% of entire isoprene content) and polyhydrogen polysiloxanes with varying SiH content (0.75 10.7 mol %) and molecular mass, Mn, from 2,500 to 36,000 g/mol. A two‐track approach was taken to determine the morphology of the copolymer system. The first employed the usual polymer characterization methods such as electron microscopy, DSC, IR spectroscopy, the density gradient method, and mechanical measurements. For the second approach, different copolymer permeability models were tested so as to give an insight into the copolymer morphology. As a final step, the permeability and permselectivity properties were correlated with the morphological structure of the copolymer system. It was observed that the respective continuous microphase dominated the copolymer's physical properties, as, e.g., permeability, permselectivity, and mechanical properties. The microphase inversion in the copolymer system was proved by the permeability/permselectivity as well as by the mechanical measurements. © 1993 John Wiley & Sons, Inc.
Dielectric behavior at microwave frequencies of an epoxy resin during crosslinking
Authors: Livi A. , Levita G. , Rolla P. A.
Published: April 2003

The dielectric behavior during the crosslinking process of a low molecular weight liquid diglycidyl ether of bisphenol‐A (DGEBA) and ethylenediamine, as the curing agent, has been investigated at microwave frequencies (0.1–10 GHz) by means of the time domain reflectometry. It was found that both the real and the imaginary part of the dielectric constant, which regularly decreased as the cure reaction proceeded, were mainly affected by the disappearance of specific dipolar species, whose relaxation time did not change significantly. A simple model based on disappearance of dipoles agrees with the experimental data and explains the coincidence between kinetic data obtained by dielectrometry and calorimetry. The microwave dielectric constant can thus be used to directly measure in real time the conversion of the reaction. © 1993 John Wiley & Sons, Inc.
Infrared spectroscopy measurements of residual stresses in polypropylene fibers
Authors: Andreassen Erik , Myhre Ole Jan
Published: April 2003

Average residual stresses in polypropylene fibers, produced in a full‐scale short‐spin line, are estimated from the shift of the IR absorption peak at 975 cm‐1. Linearly polarized incident IR radiation is used to separate between stress components parallel and perpendicular to the fiber axis. For all the fibers in this study, the axial stress component is larger than the average stress perpendicular to the fiber axis. Axial and perpendicular stresses are correlated with draw ratio and polydispersity index. For narrow molecular weight distributions (Mw/Mn < 4–5), the axial stress increases with increasing draw ratio. Average stress perpendicular to the fiber axis decreases with increasing draw ratio for all the molecular weight distributions in this study (Mw/Mn = 3–6). Measurements of residual stresses are consistent with other results characterizing molecular structure and mobility. An expression for estimating the stored deformation energy is discussed. © 1993 John Wiley & Sons, Inc.
Synthesis, rheology, and physical properties of a metathesis polymer
Authors: Asrar J. , Hurlbut J. B.
Published: April 2003

This paper describes the synthesis, physical properties, and the impact modification of poly(N‐phenylnorbornene dicarboximide) (PNDI). Impact modification is carried out both by physical blending with acrylonitrile‐butadiene rubber (Hycar®) and by in situ metathesis polymerization of the monomer with the rubber. Better success is achieved by in situ metathesis polymerization. A copolymer, poly(N‐phenylnorbornene dicarboximide) ‐ co‐poly(norbornene nitrile) containing Hycar rubber (PNDI/PNN/Hycar), is prepared with a good balance of high‐heat impact and flexural properties. The melt viscoelastic behavior of PNDI/PNN/Hycar is evaluated and the energy of activation for viscous flow (Ea) was found to be 42 kcal/mol. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of acrylic‐based superabsorbents
Authors: Askari F. , Nafisi S. , Omidian H. , Hashemi S. A.
Published: April 2003

This paper is devoted to the synthesis and characterization of superabsorbent polymers based on acrylic acid. These hydrogels were prepared by carrying the inverse suspension polymerization in an aromatic hydrocarbon. The dispersion is stabilized by the mixture of micromolecular and macromolecular emulsifiers. To obtain high swelling and appropriate absorption kinetics, parameters such as initial monomer and cross‐linker concentration, range of neutralization, monomer addition rate, temperature, initiating system, stabilizing system, and nature of the organic phase were studied but not reviewed here. Thus, based on these topics a basic formula is obtained to display the effect of some structural parameters on behaviour of superabsorbents utilized. © 1993 John Wiley & Sons, Inc.
Ring‐opening polymerization of tetrahydrofuran with rare earth‐contained catalysts
Authors: Li Fengfu , Jin Yingtai , Pei Fengkui , Wang Fosong
Published: April 2003

Rare earth trifluoroacetates, Ln(CF3CO2)3 (Ln=thirteen rare earth elements), combined with RnAlH3−n (R=methyl, octyl, n=3; R=ethyl, i‐Butyl, n=2,3) were used as catalysts for the polymerization of tetrahydrofuran (THF). The activity increased by adding propylene oxide (PO), as a promoter, to the polymerization system, producing high molecular weight polytetrahydrofuran (PTHF). The effects of Ln, PO/Ln, and Al/Ln, and others on the polymerization of THF were also studied. © 1993 John Wiley & Sons, Inc.
Preparation of a polyelectrolyte complex gel from chitosan and κ‐carrageenan and its pH‐sensitive swelling
Authors: Sakiyama Takaharu , Chu Chia‐Hong , Fujii Tomoyuki , Yano Toshimasa
Published: April 2003

A polyelectrolyte complex gel was prepared by mixing chitosan and k‐carrageenan solutions in the presence of NaCl. To study the effect of ambient pH on the swelling behavior, the diameter of the cylindrical gel(4 mm x 8 mm) immersed in aqueous NaOH, KOH, or HCl solution was measured. In the range of pH 10–12, the diameter increased with time, and the gel reached swelling equilibrium within 6 days. In an NaOH solution of pH 10.5, the maximum swelling occurred, and the volume of the gel at equilibrium was 10.2 times as large as the initial one. At pH below 9 and at pH 13, no swelling was observed. Thus, the swelling of the complex gel prepared in this study was sensitive to a rather narrow range of pH. The swelling equilibrium in the presence of NaCl was also investigated at various pH. © 1993 John Wiley & Sons, Inc.
Highly crosslinked polymer particles by dispersion polymerization
Authors: Hattori M. , Sudol E. D. , El‐Aasser M. S.
Published: April 2003

Monodisperse poly(divinylbenzene) and poly(styrene‐co‐divinylbenzene) particles were prepared in the 0.4−3 μm size range by dispersion polymerization in methanol and methanol/co‐solvent mixtures. The effects of polymerization parameters, such as the crosslinking monomer concentration, the co‐solvent, and the presence of oxygen were studied. For good colloidal stability, it was necessary to use a relatively large fraction of crosslinking monomer. The initial presence of oxygen was also found to play an important role in determining the colloidal stability during the polymerization. Although the exact mechanism is not certain, it is considered likely that the oxygen promotes the grafting of poly(divinylbenzene) to the polyvinylpyrrolidone (PVP) stabilizer molecules. The growing particles were investigated by electron microscopy. Precipitation of small particles onto the nucleated particles was determined to be the primary mechanism of particle growth. © 1993 John Wiley & Sons, Inc.
A comparative C13 NMR study of polyflavonoid tannin extracts for phenolic polycondensates
Authors: Pizzi A. , Stephanou A.
Published: April 2003

Assignment of C13 NMR bands to important sites of polymeric flavonoid tannin extracts produced industrially for production of tannin–formaldehyde resins is reported. Five different tannin extracts were studied. The C13 NMR bands' position and relative intensities allowed us to qualitatively explain comparative differences in the five tannins' structural features and properties that are of importance for tannin adhesives applications. The five tannins could be divided into two classes (1) mimosa and quebracho tannins and (2) pecan nut, pine, and gambier tannins. Properties of relevance that varied considerably among the five tannins and that could be detected by 13C NMR were: the relative proportions of fisetinidin/robinetinidin units in relation to catechin/gallocatechin units; differences in number average degree of polymerization; the extent of open heterocycle forms present; branching; and relative proportion of pyrogallol versus catechol B‐rings in the flavonoid repeating units. © 1993 John Wiley & Sons, Inc.
Ion sorption by polyamide with consideration of ionic interaction and other physical interactions
Authors: Yang Yiqi , Li Shiqi , Lan Tian
Published: April 2003

A modified Donnan model is discussed with consideration of physical interactions in the ion sorption by polyamide as a function of the influence of ions in the system. Lyotropic numbers and the salt effect on water‐structure changes are considered to describe their influence on the physical interactions between the sorbate and the sorbent. It is found that some electrolytes, such as sulfates and phosphates, can increase the sorption of some negatively charged ions (e.g., acid dyes) on positively charged polyamide it salt concentration is high (e.g., > 0.5 M), after the initial decrease of ion sorption at a low salt concentration range. This result is difficult to explain by the model that treats all interactions other than ionic interaction as a constant. The modified Donnan model explains both the decrease and increase of ion sorption with increasing salt concentration quantitatively. © 1994 John Wiley & Sons, Inc.
Heat sealing of semicrystalline polymer films. II. Effect of melting distribution on heat‐sealing behavior of polyolefins
Authors: Stehling Ferdinand C. , Meka Prasadarao
Published: April 2003

Heat sealing of films, i. e., formation of a joint between two films by placing them fleetingly between heated platens, was experimentally investigated for a variety of semicrystalline polyolefins, especially various polyethlenes, to determine how sealing temperature affected seal strength measured at room temperature. Seal strength as a function of sealing temperature, SS(T), is closely related to the melting distribution of the polymer determined by DSC measurements, i. e., to the fraction of amorphous phase as a function of temperature, fa(T). Seal initiation temperature, the temperature at which a specific, low level of seal strength of polyethylene films is achieved, corresponds to the temperature at which the fraction of amorphous phase equals 77±3%. At higher temperatures, SS(T) increases approximately as fa(T) increases. At the final melting point of the polymer, i.e., when fa(T) =1, seal strength reaches an approximately constant value termed the plateau seal strength. The magnitude of the plateau seal strength is determined by the yield stress of the polymer film. Thus, the heat‐sealing curve, SS(T), for a polyethylene can be semiquantitatively predicted from the melting distribution and yield stress of the polymer. © 1994 John Wiley & Sons, Inc.
Surface modification of polyethersulfone hollow‐fiber membranes by γ‐ray irradiation
Authors: Mok S. , Worsfold D. J. , Fouda A. , Matsuura T.
Published: April 2003

The fouling of ultrafiltration membrane is often caused by gel formation on the membrane surface. This gel layer arises due to concentration polarization or macromolecular adsorption on the membrane surface. The gel layer affects both the hydraulic permeability and the rejection properties of the membrane. In this report, the adsorption of porcine albumin and the concentration polarization effect on modified and unmodified polyethersulfone (PES) hollow‐fiber membrane is studied. PES ultrafiltration hollow‐fiber membranes were modified by the grafting of polyethylene glycol (PEG) polymer on the internal surface using γ‐ray irradiation method. The modified hollow fibers were less susceptible to fouling than were the unmodified fiber. The performance of both modified and unmodified hollow fibers was tested as a function of feed flow rates and protein concentrations. © 1994 John Wiley & Sons, Inc.
Interchain crosslinking between NBR and polyacrylic rubber and effect on (i) processibility and blend‐morphology
Authors: Tripathy A. R. , Das C. K.
Published: April 2003

Flow behaviour of NBR and polyacrylic rubber blends have been studied throughout the entire composition ranges. The effect of preheating of the blends is also studied in order to understand the interchain crosslinking. Viscosity, extrudate swell, power law indices, have been studied as a function of shear rate and blend ratio. The shearing accompanied by blend ratio has a predominent effect on the rheological behaviour of the preheated blends due to microgel formation. From the rheological behaviour it appears that there is a phase inversion at around 50% of NBR, however, preheating does not change this trend. © 1994 John Wiley & Sons, Inc.
Computer simulation of crystallization kinetics in fiber‐reinforced composites
Authors: Krause Th. , Kalinka G. , Auer C. , Hinrichsen G.
Published: April 2003

A computer simulation model was developed to investigate spherulitic growth in polymers of infinite and plate‐limited volume as well as in fibre‐reinforced polymer composite systems. Parameters like thermal nucleation rate and athermal nucleation density, plate distance, and fibre content were varied. The simulation crystallization process was evaluated following Avrami's method in the case of infinite volume and by stepwise approximation by Avrami functions in the case of limited volume. In addition, the simulation method allows the visualization of the growing entities at any phase of crystallization. Therefore the geometry of growing entities can be easily compared with the corresponding crystallization exponent. A good agreement between the crystallization exponent and the growth geometry was found.

Depending on nucleation mode, “infinite” systems yield Avrami exponents of 3 and 4. In plate‐limited volume, a transcrystallization effect was observed in case of high athermal nucleation density on plate surface and large plate distances. This particular skin effect decreases the three‐dimensional growth to a one‐dimensional needle‐shaped one. Small plate distance changes the spherical to a disk‐like growth, resulting in crystallization exponents of 2 or 3, depending on nucleation mode. The crystallization behaviour of fibrereinforced composite systems is more complex. Low fibre content or large fibre distance and high athermal nucleation density on the fibre surface induce the formation of transcrystalline zones. The three‐dimensional growth of the spheres at the beginning is restricted by their neighbours, so that their geometry changes to a pyramidical one. They grow with a front normal to the fibre surface and the crystallization exponent is shifted in between 2.0 and 2.6 depending on nucleation density. High fibre content leads to a growth along the triangular channels between three adjacent fibres; the corresponding exponent amounts to 1.6. © 1994 John Wiley & Sons, Inc.
Separation of water/ethanol mixture through poly(acrylonitrile‐co‐acrylic acid)/poly(ethylene oxide) membranes by pervaporation
Authors: Jo Won Ho , Kim Hyo Jin , Kang Yong Soo
Published: April 2003

The separation of water/ethanol mixtures was investigated by poly(acrylonitrile‐co‐acrylic acid) and by poly(acrylonitrile‐co‐acrylic acid)/poly(ethylene oxide) blend membranes. The flux increased with the content of acrylic acid in copolymers and the selectivity remained constant. The marked increase of the selectivity was observed for blend membranes of a certain blend ratio, suggesting that the two polymers are partially miscible. Poly(ethylene oxide) in blends was thought to act as a plasticizer as well as a preferentially water absorbing and diffusing component. © 1994 John Wiley & Sons, Inc.
Studies of water‐soluble oligomers formed in emulsion copolymerization
Authors: Wang Shou‐Ting , Poehlein Gary W.
Published: April 2003

A polymer chain transfer agent was synthesized by the reaction between poly(vinylbenzyl chloride) latex particles and 2‐aminoethanethiol in a basic environment. In subsequent emulsion polymerization reactions, low molecular weight species were formed when waterborn oligomeric radicals diffused to the surface of these seed particles. These low molecular weight oligomers were separated by membrane filtration and their composition and molecular weight weight were analyzed by FTIR and mass spectroscopy. The measured composition results were compared with those that were calculated from the copolymerization equation. The molecular weights were compared with earlier experimental results that were obtained by isolation of oligomers formed when a water‐soluble inhibitor was added to a reacting emulsion.

Three seeded emulsion copolymerization systems, that is, styrene–acrylic acid, styrenemethacrylic acid, and styrene–methyl methacrylate, were investigated. The distribution of monomer in the water phase and in the copolymer particles was analyzed. The results show that the oligomer compositions for different copolymerization systems can be approximated reasonable well by the copolymerization equation, using the reactivity ratios obtained from bulk copolymerization. The length of the oligomer radicals formed depends on their composition and the properties of the polymer particles, such as surface charge, composition, size, and concentration. © 1994 John Wiley & Sons, Inc.
Temperature‐responsive characteristics of N‐isopropylacrylamide‐grafted polymer films prepared by photografting
Authors: Kubota Hitoshi , Nagaoka Noriyasu , Katakai Ryoichi , Yoshida Masaru , Omichi Hideki , Hata Yasuo
Published: April 2003

Photografting of N‐isopropylacrylamide (NIPAAm) on ethylene–vinyl alcohol copolymer films (thickness = 15,20, and 25 μm) and low‐and high‐density polyethylene films (thickness = 30 μm) was carried out at 60°C in a water medium. Xanthone was used as a photoinitiator by coating it on the film samples. The resultant NIPAAm‐grafted films exhibited a temperature‐responsive character, which was evaluated by measuring a dimensional change of the grafted films. The grafted films swelled and shrank in water at temperatures lower and higher than around 30°C, respectively. The character was found to be reversible between 0 and 50°C. It was observed that the extent of the character is largely influenced by film thickness, location of NIPAAm‐grafted chains, and crystallinity of film substrate. © 1994 John Wiley & Sons, Inc.
Effects of thermal and mechanical fatigue on flexural strength of G40‐600/PMR‐15 cross‐ply laminates
Authors: Roberts Gary D. , Ho Barry Ping Hsiao , Wallace John F.
Published: April 2003

The effects of thermal and mechanical fatigue on the flexural strength of G40‐600/PMR‐15 cross‐ply laminates with ply orientations of (02, 902)2sand (902, 02)2sare examined. The relative improtance of shear and tensile stresses is examined by varying the span‐to‐depth ratios of flexural test specimens from 8 to 45 Acoustic emission singals are measured during the flexural tests in order to monitor the initiation and growth of damage. Optical microscopy is used to examine speciments for resin cracking, delamination, and fiber breaks after testing. Transverse matrix cracks and delaminations occur in all specimens, for regardless of ply orientation, span‐to‐depth ratio, or previous exposure of specimens to thermal and mechanical fatigue. A small amount of fiber tensile fracture occurs in the outer 0° ply of specimens with high span‐to‐depth ratios. Because of the complex failure modes, the flexural test results represent the “apparent” strengths rather than the true flexural or shear strenghts for these cross‐ply laminates. Thermal cycling of specimens prior to flexural testing does not reduce the apparent flexural strength or change the mode of failure. However, fewer acoustic events are recorded at all strins during flexural testing of specimens exposed to prior thermal cycling. High temperature thermal cycling (32–260°C, 100 cycles) causes a greater reduction in acoustic events than low temperature thermal cycling (‒85 to 85°C, 500 cycles). Mechanical cycling (0–50% of the flexural strength, 100 cycles) has a similar effect, except that acoustic events are reduced only at strains less than the maximum strain applied during flexural fatigue. © 1994 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Preparation and characterization of cryogenic adhesives. I. Glycidyl‐terminated polyurethane resins
Authors: Chen Der‐Shyang , Ma Chen‐Chi M. , Hsia Hung‐Chung , Wang Wang‐Nang , Lin Shiaw‐Ruey
Published: April 2003

Glycidol has been introduced into isocyanate‐terminated polyurethane to form glycidyl‐terminated polyurethane resin. A series of glycidyl‐terminated polyurethanes, based on PTMEG, PPG, and polyester soft segments, having different molecular weights were synthesized and their adhesion properties on aluminum were evaluated. The effect of the soft‐segment structure, soft‐segment length, and temperature on adhesion were examined. It was found that the resin showed superior adhesion at cryogenic temperatures. The results coincide with the phenomenon observed in dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). In addition, the modified system also offered some distinct advantages over the commercial polyurethane adhesives, e.g., good storage stability and room‐temperature curing. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of 2‐vinylnaphthalene–EPDM–methyl methacrylate graft copolymer
Authors: Park Joo‐Yong , Park Duck‐Jei , Ha Chang‐Sik , Cho Won‐Jei
Published: April 2003

A graft copolymer of 2‐vinylnaphthalene (2‐VN) and methyl methacrylate (MMA) onto ethylene–propylene–diene terpolymer (EPDM) was synthesized in tetrahydrofuran using benzoyl peroxide. The effects of EPDM content, and ratio of 2‐VN to MMA, reaction time, reaction temperature, and initiator concentration in the graft copolymerization were examined. The light resistance, thermal stability, and the tensile properties of the graft copolymer were investigated by using Fade‐o‐Meter, thermogravimetric analyzer, and tensile tester. It was found that the light resitance and the heat resistance as well as the tensile strength of the graft copolymer are considerably better than those of the acrylonitrile–butadiene–styrene (ABS) copolymer. © 1994 John Wiley & Sons, Inc.
The mechanisms of oxidative degradation of biomedical polymers by free radicals
Authors: Ali S. A. M. , Doherty P. J. , Williams D. F.
Published: April 2003

Degradation is an essential factor in polymer biocompatibility. The physiological environment of the human body can be aggressive to polymers. Most implanted polymers suffer degradation and the kinetics and mechanisms of the processes can be significantly affected by various biologically active species, especially enzymes, lipids, peroxides, free radicals, and phagocytic cells. Iron enhances the toxicity of oxygen free radicals. Superoxide and hydrogen peroxide can interact to form the very toxic hydroxyl radical in the presence of iron. The data have shown that the hydroxyl radical is likely to be one of the main causes of polymer degradation in implantable devices. © 1994 John Wiley & Sons, Inc.
Fenton's reagent‐initiated graft copolymerization of acrylonitrile onto sodium alginate
Authors: Shah Samir B. , Patel Chandrakant P. , Trivedi Harikrishna C.
Published: April 2003

Graft copolymerization of acrylonitrile (AN) onto sodium alginate was studied in an aqueous medium using ferrous ammonium sulfate–hydrogen peroxide (Fenton's reagent) as the redox initiator. To optimize the reaction conditions for affording maximum percentage of grafting, the concentrations of sulfuric acid, initiator components, monomer, and also temperature and time were varied. The results are discussed and a reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc.
Rheological properties, tensile properties, and morphology of PP/EPDM/lonomer ternary blends
Authors: Kim Youngkyoo , Ha Chang‐Sik , Kang Tae‐Kyu , Kim Yang , Cho Won‐Jei
Published: April 2003

The rheological and tensile properties and the morphology of polypropylene (PP)/ethylenepropylene‐diene terpolymer(EPDM)/ionomer ternary blends were investigated, using a rheometric dynamic spectrometer (RDS), a dynamic mechanical thermal analyzer (DMTA), a tensile tester, and a scanning electron microscope (SEM). Two kinds of poly(ethylene‐co‐methacrylic acid) (EMA) ionomers, neutralized with different metal ions (Na+ and Zn++), were used. Blends were melt‐mixed, using a laboratory internal mixer at 190°C. The composition of PP and EPDM was fixed at 50/50 by wt % and the EMA ionomer contents were varied from 5 to 20 wt %, based on the total amount of PP and EPDM. It was found that the ternary blends, containing Na‐neutralized ionomer, showed considerably different rheological properties and morphology as compared to the PP/EPDM binary blends, due to the compatibilizing effect of the ionomer for PP and EPDM, while the ternary blends, containing the Zn‐neutralized ionomer, did not. The compatibilizing effect was most prominent at 5 wt % ionomer concentration. © 1994 John Wiley & Sons, Inc.
Studies on graft copolymerization of 2‐hydroxyethyl methacrylate onto poly(vinyl chloride)
Authors: Lee Wen‐Fu , Lai Cherng‐Ching
Published: April 2003

Poly(vinyl chloride) was dehydrochlorinated in alkali solution and then grafted with 2‐hydroxyethyl methacrylate (HEMA) using benzoyl peroxide as a free‐radical initiator under a nitrogen atmosphere. The investigations involved examining the effects of grafting efficiency on various conditions, such as degree of dehydrochlorination, HEMA concentration, solvent effect, and reaction time. Maximum grafting to the extent of 57.2% was obtained. The mixed solvent grafting was attempted. © 1994 John Wiley & Sons, Inc.
The use of mica flakes for reducing internal stress in cured epoxy resin
Authors: Gupta V. B. , Brahatheeswaran C.
Published: April 2003

Mica, in the form of flakes of different sizes and size distributions, was mixed with a difunctional epoxy resin to the extent of 10 to 50 parts by weight of the resin. To this resin–filler mixture, a stoichiometric amount of a tetrafunctional curing agent was added. First, a thin a aluminium strip was coated with the mica–resin–amine mixture and was subjected to two curing cycles. Second, sheets were cast from the mixture by subjecting them to the same two cure cycles. The internal stresses that developed in the coated samples, and their relaxation with time, were studied. The dynamic torsional spectra of rectangular bars cut from the sheet were also mapped. The debonding and microcracking, resulting from internal stress, have been shown to result in a significant reduction in internal stress in the mica‐filled samples, particularly in samples containing large mica flakes in which delamination of the mica layers in the flake has also been shown to occur. However, despite this phenomenon, the filled samples were found to have adequate mechanical and electrical properties. © 1994 John Wiley & Sons, Inc.
Crystallization analysis fractionation: A new technique for the analysis of branching distribution in polyolefins
Authors: Monrabal Benjamin
Published: April 2003

A new technique to analyze the short‐chain branching distribution (SCBD) in linear lowdensity polyethylene has been developed. The technique referred as crystallization analysis fractionation is based on a stepwise precipitation approach. By monitoring the polymer solution concentration during crystallization, the cumulative and differential SCBD can be obtained without the need of physical separation of fractions. The new technique has been shown to provide similar results to temperature rising elution fractionation but in a shorter time and with a simplified apparatus. It allows the simultaneous analysis of various samples and could also be used for analysis of polypropylene and other semicrystalline polymers that can be fractionated on the basis of crystallizability. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of liquid crystal photoresist
Authors: Yamashita K. , Kyo S. , Miyagawa T. , Nango M. , Tsuda K.
Published: April 2003

A thermotropic liquid crystal polymer with photosensitive groups (liquid crystal photoresist), copoly(4‐methoxyphenyl) 4′‐(2″‐acroloyloxy ethoxy) benzoate (MPAEB)‐4‐vinylbenzyl cinnamate (VBC) was prepared, and its thermal behavior was characterized by a differential scanning calorimetry. The copolymer exhibited a liquid crystal mesophase between approximately 70°C and 120°C. In the mesophase, poly(MPAEB‐VBC) (85/15) had a higher photo‐crosslinking ability than that at room temperature and at 140°C, where the copolymer exhibited the isotropic phase. It was found that the liquid crystal photoresist had a high crosslinking ability owing to alignment of its photosensitive groups. © 1994 John Wiley & Sons, Inc.
Dyeability of silk fabrics modified with dibasic acid anhydrides
Authors: Freddi Giuliano , Tsukada Masuhiro , Kato Hiroshi , Shiozaki Hideki
Published: April 2003

Silk fabrics were chemically modified with different kinds of dibasic acid anhydrides. Samples with different acyl contents, ranging from 24 to 107 mol/105g, were obtained by reaction with succinic (S), glutaric (G), phthalic (PA), and 0‐sulfobenzoic (OSBA) anhydrides. Dyeability with a cationic dye (Rhodamine B, C.I. Basic Violet 10) was determined by measuring dye uptake and K/S values. Following acylation, the absorption of basic dye was significantly enhanced for all samples. The maximum dye uptake was attained by OSBA‐treated silk fabrics, while samples treated with S. G. and PA did not differ significantly. Dye uptake increased regardless of the content, at least in the range examined. Reflectance measurements and K/S values confirmed the trend evidenced by dye uptake results. © 1994 John Wiley & Sons, Inc.
Effect of environmental factors on the mechanical properties of grafted casein films: Influence of temperature and extension rate
Authors: Somanathan N.
Published: April 2003

Casein was grafted with acrylonitrile (AN) and with a binary mixture of acrylonitrile and n‐butyl methacrylate (n‐BMA). Stress‐strain characteristics of these films were analyzed as a function of temperature and rate of extension. The results shows that both the systems are sensitive to temperature. Due to the incorporation of n‐BMA, the material becomes flexible since the Tg of the multiphasic polymer was reduced and therefore shows the changes even at lower temperatures when compared to casein grafted with AN. The fracture morphologies of the binary mixture‐grafted casein films show that the effect produced by temperature and rate of extension are inversely related. © 1994 John Wiley & Sons, Inc.
Effect of surfactants on the particle sizes of red#170 polyurea microcapsules
Authors: Kuo Y. M. , Wu C. T. , Wu W. H. , Chao D. Y.
Published: April 2003

Red#170 (pigment) polyurea microcapsules have been successfully prepared at our laboratory. Both core and shell of these microcapsules are demonstrated to be red#170 pigment and polyurea, respectively, by infrared (IR) spectra. The number‐average particle sizes of these microcapsules are seen to decrease with increasing concentration and the ethylene oxide chain length of nonylphenylpolyoxyethylene ether (NPn; n = 6, 8, 10, 12, 16) as an emulsifier in the water phase used for making microcapsules. Experimental results indicate that the average particle sizes of red#170 polyurea microcapsules are smaller for the system with NP16 than for the system with NP4 (in the oil phase) and/or NP16 (in the water phase) and that, in the presence of NPn, these particle sizes are seen to be slightly smaller for use of methylcellulose than for use of sodium carboxymethylcellulose as a protective colloid. It is also interesting to note that the released amounts of red#170 pigment from polyurea microcapsules in di‐n‐butylphthalate solvent is lower for a system with NP16 than for a system with methylcellulose, as a result of good emulsification leading to decrease the interaction between toluene diisocyanate and water molecules. This may further cause more crosslinkage to take place at the urea groups, resulting in a decrease in the porosity of the capsules. © 1994 John Wiley & Sons, Inc.
Properties of oriented polyethylene bars of large cross section
Authors: Courval Gregory , Wang Li‐Hui , Porter Roger S.
Published: April 2003

The solid‐state extrusion technique has been used to prepare uniaxially oriented polyethylene bars with rectangular end cross sections of 6 × 50 mm2. They were extruded at 110°C from billets of high density polyethylene. The tensile modulus and strength for the extrudate with a draw ratio (DR) of 14 were 17.9 and 0.32 GPa, respectively. The mechanicals were also measured in the transverse direction by means of the proportional elastic limit (PEL) bending test. The PEL results do not change after DR 14 due to the fibrillate structure formation. Crystallinity and shrinkage tests were made on samples taken over the bar cross section. They show that uniform properties were achieved across the width of the bar with proper die design. © 1994 John Wiley & Sons, Inc.
Continuous polymerization of caprolactam in a modular intermeshing corotating twin screw extruder integrated with continuous melt spinning of polyamide 6 fiber: Influence of screw design and process conditions
Authors: Kye Hyoungsan , White James L.
Published: April 2003

The continuous anionic polymerization of caprolactam to polyamide‐6 in a modular, intermeshing, corotating twin screw extruder was investigated. Caprolactam was polymerized by anionic polymerization techniques under a range of processing conditions, including different screw configurations, temperature profiles, screw speeds, and throughputs. Studies were also made of melt spinning polyamide 6 into oriented filaments. The polyamide‐6 melt spun filaments were characterized using birefringence and wide angle X‐ray diffraction. Uniaxial stress measurements of the fibers were obtained and are reported. The results for the melt spun filaments compare favorably with the previous literature. © 1994 John Wiley & Sons, Inc.
Immobilization of spent ion‐exchange resins in the urea‐formaldehyde matrix
Authors: Rao S. V. S , Kothandaraman H. , Sudhakar M. , Lal K. B. , Amalraj R. V.
Published: April 2003

Studies have been carried out on the immobilization of spent ion‐exchange resins produced in nuclear power plants in urea‐formaldehyde matrix. The matrices were prepared by incorporating different types of ion‐exchange resins in the pH range of 4.5 to 5.0, using boric acid as a catalyst. Characterization of the matrices was carried out with respect to dimensional changes, compressive strength, and leach resistance. The cumulative percentage weight loss and volume change were observed to decrease with the increase in boric acid concentration before attaining a plateau. The diffusion coefficients were in the order of 10−16 M/s, and the compressive strengths were in the range of 0.83 to 12 MPa. Infrared spectral studies on the urea‐formaldehyde matrices revealed that the rate and the extent of cure depended on the type of resin. © 1994 John Wiley & Sons, Inc.
Flocculation behavior of some cationic polyelectrolytes
Authors: Smith‐Palmer Truis , Campbell Nicole , Bowman Janice L. , Dewar Patricia
Published: April 2003

The settling rates and adsorption isotherms produced by a variety of suites of cationic polyelectrolytes in 3% kaolin suspensions were measured. Settling rates increased with molar mass even for low‐mass, high‐charge polymers. The very high settling rates produced by cationic copolymers of acrylamide decreased as the charge density of the polymer used increased. Hydrolysis of unbuffered polymers occurred over time and produced large changes in the effectiveness of the polymers. This is attributed to conformational changes. © 1994 John Wiley & Sons, Inc.
Investigation of the miscibility of polycarbonate–poly(ethyleneterephthalate) blends: Solid‐state 1H‐NMR T1 relaxation time measurements, transmission electron microscopy, and structure–properties relationship
Authors: Abis L. , Braglia R. , Camurati I. , Merlo E. , Natarajan K. M. , Elwood D. , Mylonakis S. G.
Published: April 2003

Solid‐State 1H‐NMR measurements of T1 relaxation times performed on polycarbonate‐poly(ethyleneterephthalate) (PC–PET) blends point out the presence of two separate domains with apparent dimensions of about 80 nm. The variation of PET domain relaxation time with the increase of PC content is explained in terms of an interface in which parts of the PC molecules are finely dispersed into the PET matrix. Relaxation parameters and compositions match very well an equation that quantitatively describes a three‐phase model formed by two domains separated by an interface of mixed components. Micrographs obtained by transmission electron microscopy (TEM) clearly reveal the presence of two separate domains with a phase inversion at 40/60 wt% composition. PET domains, although larger than expected from NMR analysis, are characterized by a dispersion of small PC particles that are considered responsible for the observed diffusion of magnetization from PET to PC domains. The partial miscibility seems to be physical in nature rather than due to transesterification processes between the components, as stem from 1H‐NMR spectra in solution of PET and PC–PET blends. T1 relaxation times measured in the same way on totally immiscible PC–PA‐6 blends, support, by contrast, the NMR interpretation of PC–PET results. The mechanical properties of PC–PET blends exhibit ductile behavior throughout the entire range of composition. This indicates that PC and PET are mechanically compatible. This is also in agreement with the isothermal crystallization data for PET at various compositions of PC–PET. These results are in agreement with the existence of a partial miscibility between PET and PC. © 1994 John Wiley & Sons, Inc.
Influence of N‐acetylglycine on the kinetics of the ceric ion‐initiated graft copolymerization of acrylonitrile and methyl methacrylate onto jute fibers
Authors: Patra C. M. , Singh B. C.
Published: April 2003

The influence of N‐acetylglycine on the kinetics of graft copolymerization of acrylonitrile (AN) and methyl methacrylate (MMA) onto chemically modified jute fibers was studied in the temperature range 40–60°C. The optimum conditions for grafting have been determined by studying the effects of concentrations of monomers, Ce(IV), and N‐acetylglycine on the rate of grafting. Besides the effect of time, temperature, and concentration of the acid, the amount of jute fibers and some organic solvents and inorganic salts on the rate of grafting has been investigated. On the basis of experimental findings, a kinetic scheme has been proposed. Infrared spectra of chemically modified jute and grafted jute have been investigated. More than 185% graft yield could be achieved with the present system. Grafting has improved the thermal stability of jute fibers. © 1994 John Wiley & Sons, Inc.
Effect of chemical and physical crosslinks on strength of rubber and plastics—a theoretical approach
Authors: Furukawa Junji , Yamada Eisuke
Published: April 2003

For rupture of rubber and plastics, three types are proposed: (a) elastic, (b) plastic, and (c) brittle. For (a) the rupture takes place at the ultimate elongation of chains between crosslinks. Strength f is proportional to the number of crosslinks and also the fraction of effective chains giving the optimum degree of vulcanization ν. Both ν and f at the maximum strength decrease with increasing the bond energy D of crosslinks. The rupture in (b) occurs for filled rubbers. The maximum reinforcement with filler is expected to be attained at 20% volume fraction of filler from the pseudo‐link model in which the number of links are proportional to the specific surface area, the fraction, and the adsorption ability of the filler particles. For (c) the craze occurs due to the breakdown of pseudo‐crosslinks of the smallest size b, and b is 2 at the glass transition temperature. Impact strength is improved by the dispersion of rubber particles at the optimum fraction of 13% and under the small distance of neighboring particles, which is 0.4 μm and is corresponding to the relaxation distance. © 1994 Wiley & Sons, Inc.
Molecular weight measurement in weathered polymers
Authors: O'Donnell B. , White J. R. , Holding S. R.
Published: April 2003

Gel permeation chromatography has been used to monitor the molecular weight changes that occur when polymers are degraded by photooxidation. Methods of sample preparation and procedures for conducting the chromatography measurements and for analyzing the results are discussed. Examples are given of applications to studies of polystyrene (PS), polypropylene (PP), and glass fiber‐reinforced polypropylene (GFPP) exposed to ultraviolet (UV) irradiation in the laboratory. The results show that the degradation rate is fastest near the exposed surface, but in PS and PP, degradation is much faster at the unexposed surface than in the center of the molding, where the UV intensity is greater than at the unexposed surface. It is deduced that degradation at the center is slowed by a shortage of oxygen. © 1994 John Wiley & Sons, Inc.
Automated microscopic technique for evaluating poly(vinyl chloride)–plasticizer compatibility
Authors: Caldas V. , Radiotis T. , Brown G. R.
Published: April 2003

An automated microtechnique has been developed that permits a rapid, reproducible determination of the Flory–Huggins χ interaction parameters for poly(vinyl choloride)–plasticizer systems. It is a modification of the Anagnostopoulos method of determining an apparent melting temperature of a poly(vinyl chloride) (PVC) particle in excess plasticizer. A microscope equipped with a photodiode sensor is used to measure changes in the light transmitted through a plasticizer sample containing a PVC particle as the temperature is increased at a fixed rate, either 0.2 or 1.0°C/min. Data acquisition is done by computer so that minimal operator assistance is required. The apparent melting region is characterized by a sigmoidal change in the light transmitted through a fixed sample area. This curve allows an accurate, reproducible definition of the apparent melting temperature from which the χ parameter is easily derived. The values obtained for the interaction parameter of PVC with four plasticizers chosen from the phthalate and phosphate families are in good agreement with general trends of solvent quality. Separate experiments demonstrated that the overall transmittance profile reflects changes in both the size and the optical clarity of the PVC particle during heating. This leads to added features in the profile that reflect important diffusion and swelling characteristics for a given system. © 1994 John Wiley & Sons, Inc.
Synthesis and structural investigation of conductive composites from cellophane and polypyrrole
Authors: Bhat N. V. , Shaikh Y. B.
Published: April 2003

A versatile method for preparing conducting composites from cellophane and pyrrole by an interface technique has been attempted. Polymerization of pyrrole into the porous matrix of cellophane produces black, flexible composite film with conductivity comparable to that of polypyrrole and mechanical properties very similar to cellophane. © 1994 John Wiley & Sons, Inc.
Correlations between rheological and mechanical properties of mineral filled polypropylene compounds
Authors: Gahleitner M. , Bernreitner K. , Neißl W.
Published: April 2003

A comparative study of rheological and mechanical properties of Polypropylene compounds with talc as a mineral filler is presented. It turns out that the main factors determining the mechanical behavior, namely (a) filler concentration, (b) filler particle size, and (c) degree of dispersion, influence the linear viscoelastic properties as well. Thus, a quick method for estimating compound properties from melt rheology is established. © 1994 John Wiley & Sons, Inc.