bluuebunny/crossref_metadata_2025_split huggingface dataset:
Control of shrinkage and final conversion of vinyl ester resins cured in low‐temperature molding processes
Authors: Cao Xia , Lee L. James 
Published: September 2003

AbstractVinyl ester resin is a major thermoset polymer used in low‐temperature composite manufacturing processes such as the Seemann composite resin infusion‐molding process (SCRIMP). Volume shrinkage and residual styrene are important concerns for composites produced in such processes. A low‐shrinkage additive (LSA) is a typical agent added to control the volume shrinkage of vinyl ester resins during molding. In this study, the effects of LSA content and the temperature profile (the temperature gradient and peak temperature) on the volume shrinkage control of a vinyl ester resin were investigated. The reaction kinetics of the resin system were also studied. We achieved good volume shrinkage control if we raised the curing temperature slowly to allow sufficient time for phase separation and if the curing temperature reached a high value after phase separation to allow microvoid formation. On the basis of experimental results, we designed an improved SCRIMP to increase resin conversion, reduce resin shrinkage, and produce composites with better properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1486–1496, 2003
Preparation and characterization by radiation of poly(vinyl alcohol) and poly(N‐vinylpyrrolidone) hydrogels containing aloe vera
Authors: Park Kyoung Ran , Nho Young Chang 
Published: September 2003

AbstractIn these studies, hydrogels for wound dressings were made from a mixture of aloe vera and poly(vinyl alcohol) (PVA)/poly(N‐vinylpyrrolidone) (PVP) by freezing and thawing, γ‐Ray irradiation, or a two‐step process of freezing and thawing and γ‐ray irradiation. We examined the physical properties, including gelation, water absorptivity, gel strength, and degree of water evaporation, to evaluate the applicability of these hydrogels for wound dressings. The PVA:PVP ratio was 6:4, the dry weight of aloe vera was in the range 0.4–1.2 wt %, and the solid concentration of the PVA/PVP/aloe vera solution was 15 wt %. We used γ radiation doses of 25, 35, and 50 kGy to expose mixtures of PVA/PVP/aloe vera to evaluate the effect of radiation dose on the physical properties of the hydrogels. Gel content and gel strength increased as the concentration of aloe vera in the PVA/PVP/aloe vera gels decreased and as radiation dose increased and the number of freeze–thaw cycles was increased. The swelling degree was inversely proportional to the gel content and gel strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1477–1485, 2003
Toughening of epoxy resins by hydroxy‐terminated, silicon‐modified polyurethane oligomers
Authors: Bhuniya Sankarprasad , Adhikari Basudam 
Published: September 2003

AbstractEpoxy resins are among the most versatile engineering structural materials. A wide variety of epoxy resins are commercially available, but most are brittle. Several approaches have been used to improve the toughness of epoxy resins, including the addition of fillers, rubber particles, thermoplastics, and their hybrids, as well as interpenetrating polymer networks (IPNs) of acrylic, polyurethane, and flexibilizers such as polyols. This last approach has not received much attention; none of them have been able to suitably increase resin toughness with out sacrificing tensile properties. Therefore, in an attempt to fill this gap, we experimented with newly synthesized hydroxy‐terminated silicon‐modified polyurethane (SiMPU) oligomers as toughening agents for epoxy resins. SiMPU oligomers were synthesized from dimethyl dichlorosilane, poly(ethylene glycol) (weight‐average molecular weight ∼ 200), and toluene 2,4‐diisocyanate and characterized with IR, 1H‐NMR and 13C‐NMR, and gel permeation chromatography. The synthesized SiMPU oligomers, with different concentrations, formed IPNs within the epoxy resins (diglycidyl ether of bisphenol A). The resultant IPN products were cured with diaminodiphenyl sulfone, diaminodiphenyl ether, and a Ciba–Geigy hardener under various curing conditions. Various mechanical properties, including the lap‐shear, peel, and impact strength, were evaluated. The results showed that 15 phr SiMPU led to better impact strength of epoxy resins than the others without the deterioration of the tensile properties. The impact strength increased continuously and reached a maximum value (five times greater than that of the virgin resin) at a critical modifier concentration (20 phr). The critical stress intensity factor reached 3.0 MPa m1/2 (it was only 0.95 MPa m1/2 for the virgin resin). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1497–1506, 2003
Reactor blending of polyethylene with ethyl‐bridged zirconocene catalyst and iron‐based diimine complex
Authors: Guo Cunyue , Ma Zhi , Zhang Mingge , Ke Yucai , Hu Youliang 
Published: September 2003

AbstractBlends of polyethylene (PE) were produced in a single reactor using a combination of {[(2‐ArNC(Me))2C5H3N]FeCl2} [Ar2,6‐2CH3(C6H4)] and rac‐Et(Ind)2ZrCl2. The experimental results showed that the PEs obtained have a broad molecular weight distribution (MWD) and both the molecular weight and the MWD can be regulated through changing the mole ratio of the two active sites. In addition, the polymerization activities decreased with the increase of the Fe/Zr mole ratio whereas the crystallinity of the PE obtained exhibited a contrary trend, decreasing as the Fe/Zr mole ratio went up. The morphology of the blends also directly relates to the Fe/Zr mole ratio, and more iron content in the bimetallic catalysts system gives rise to compact PEs of high crystallinity. This reflects that the reactor blends are morphology controllable as well and can be easily applied to present processing techniques because of adjustable molecular weights and their distribution. Differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography, and scanning electron microscopy were employed to characterize the properties of the reactor blends of PEs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1515–1518, 2003
Rice husk ash filled natural rubber. III. Role of metal oxides in kinetics of sulfur vulcanization
Authors: da Costa H. M. , Visconte L. L. Y. , Nunes R. C. R. , Furtado C. R. G. 
Published: September 2003

AbstractIn preceding investigations the overall rate and apparent activation energy for the vulcanization process were calculated for natural rubber compounds, assuming that vulcanization follows first‐order kinetics. It was observed that the addition of white rice husk ash (WRHA) increased the rate of crosslinking and lowered the apparent activation energy more profoundly than commercial fillers, precipitated silica (Zeosil‐175) and carbon black (N762), with a conventional vulcanization system. In this work, a specific model for the vulcanization process accelerated by N‐cyclohexylbenzothiazole sulfenamide was used to investigate the real role of WRHA in crosslink formation. Cure studies were carried out at 150°C, and the kinetics constants were evaluated. In relation to the other fillers, WRHA seems to develop catalytic activity, resulting in a positive effect on the specific rate of crosslink formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1519–1531, 2003
Properties of extrusion cast sheets of blends of natural and aliphatic polyesters
Authors: Bhattacharya Mrinal , Mani Ramaswamy 
Published: September 2003

AbstractNatural and synthetic polymers of various compositions were blended in a twin‐screw extruder. These blends were then sheeted into thin sheets with a coat hanger die attached to a single‐screw extruder. The natural content in the blend was varied between 5 and 50 wt %, and the mechanical and morphological properties of the blends were evaluated. At 50 wt % natural content, the tensile strength decreased to a third of that of the synthetic polymer. The use of a compatibilizer doubled the tensile strength for the 50 wt % natural content blend. The sheets displayed equal strengths in the machine and transverse direction. The tear strength decreased as the natural content increased, and the decrease was greater in the anhydride‐compatibilized blends than in the uncompatibilized blends. The blends displayed two distinct glass transitions, one for each component, indicating phase separation. The crystallinity of the blends decreased as the starch content increased. This result was confirmed by differential scanning calorimetry (DSC), which showed that the melting endotherm decreased as the starch content increased. Gel permeation chromatography (GPC) results showed that the peak position was at the same location irrespective of blend composition, indicating minimal degradation of starch moieties. The water absorption was diffusion controlled, with a sharp initial burst of water uptake. Scanning electron microscopy (SEM) showed melting of starch granules that formed a co‐continuous phase with the synthetic polyester. Increasing the natural content also increased the surface roughness of the sheets. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1545–1554, 2003
Influence of carboxylic acid additives on the flow behavior of molten thermoplastics
Authors: Ahn Sungtae , White James L. 
Published: September 2003

AbstractFollowing the suggestions of the behavior of carboxylic acid lubricants between steel surfaces and the wide usage of such acids in polymer compounds, we have considered their influence as an additive in polymer melts. An experimental study of the influence of carboxylic acid additives in various thermoplastics in rheometers is described. Capillary and cone‐plate experiments are reported. A series of polymers of varying polarity, including polyethylene, poly(propylene), polystyrene, poly(methyl methacrylate), and polyamide‐12, are compared. Both aliphatic fatty acids and aromatic carboxylic acids were used as additives. The aliphatic fatty acids include propionic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid, and commercial stearic acid (mixture of tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, and octadecanoic acid). The aromatic carboxylic acids include benzoic acid, p‐toluic acid, and 3‐phenylpropionic acid. The greatest effects were found with polyethylene and poly(propylene). Little or no effects were found with the other polymers. Aliphatic fatty acids were more effective than aromatic carboxylic acids. Mechanisms for this behavior are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1555–1564, 2003
Melt‐intercalation nanocomposites with chlorinated polymers
Authors: Kim Younghoon , White James L. 
Published: September 2003

AbstractPolyolefins and chlorine‐containing polymers were investigated to produce polymer nanocomposites. Natural and organic‐treated montmorillonite clays were melt compounded with the polymers. Organic‐treated montmorillonite clay dispersed well in polychloroprene, chlorinated‐polyethylene, polyvinyl chloride, chlorinated‐polyvinyl chloride, and polyvinylidenechloride polymers, and formed nanocomposites. They were not well dispersed in polyolefins that contain no chlorine. X‐ray diffraction and transmission electron microscopy techniques indicated the separation of montmorillonite layers and indicated the formation of polymer nanocomposites in chlorine‐containing polymers. Mechanical testing showed enhanced tensile strength and Young's modulus of chlorinated‐polymers/clay compounds, but not polyolefins/clay compounds. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1581–1588, 2003
Shape‐memory effects of radiation crosslinked poly(ϵ‐caprolactone)
Authors: Zhu G. , Liang G. , Xu Q. , Yu Q. 
Published: September 2003

AbstractPoly(ϵ‐caprolactone) (PCL) with different molecular weight were crosslinked by γ‐radiation. The radiation crosslinking features were analyzed by Soxhlet extraction with toluene and the Charlesby–Pinner equation. The crosslinking degree is relative to molecular weight and radiation dose; the relation between sol fraction and dose follows the Charlesby–Pinner equation. All the samples were crystalline at room temperature, and the radiation crosslinking had a little effect on the crystallinity and the melting behavior of PCL. The shape‐memory results indicated that only those specimens that had a sufficiently high crosslinking degree (gel content is higher than about 10%) were able to show the typical shape‐memory effect, a large recoverable strain, and a high final recovery rate. The response temperature of the recovery effect (about 55°C) was related to the melting point of the samples. The PCL shape‐memory polymer was characterized by its low recovery temperature and large recovery deformation that resulted from the aliphatic polyester chain of PCL. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1589–1595, 2003
Living/controlled radical autopolymerization of styrene in the presence of CuCl2 and 2,2′‐bipyridine
Authors: Cheng Zhenping , Zhu Xiulin , Zhou Nianchen , Lu Jianmei 
Published: September 2003

AbstractThe bulk autopolymerization of styrene (St) was successfully conducted in the presence of CuCl2 and 2,2′‐bipyridine (bpy) at 110 and 130°C. We found that this polymerization was a living/controlled radical polymerization at a [St]0/[CuCl2]0/[bpy]0 ratio of 54:1:2.5. The resulting number‐average molecular weights linearly increased with conversion, and the polydispersity indices were very narrow (<1.5). The polymerization rate increased with temperature. Increasing the ratios (i.e., 129:1:2.5, 259:1:2.5, and 386:1:2.5) led to a decrease in the ability to control the autopolymerization of St, even uncontrolled polymerization (i.e., 643:1:2.5). The analysis of end groups by 1H‐NMR indicated that the spontaneous generation of radicals from St were generated by a Mayo‐type process, and this living/controlled radical polymerization might have underwent a reverse atom‐transfer radical polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1532–1538, 2003
Effect of the vulcanizing system on the mechanical properties of butyl rubber/ethylene propylene diene monomer–carbon black blends
Authors: Abd‐El Salam F. , Abd‐El Salam M. H. , Mostafa M. T. , Nagy M. R. , Mohamed M. I. 
Published: September 2003

AbstractThe effect of the vulcanizing system on the mechanical properties of butyl rubber/ethylene propylene diene monomer–general purpose furnace black–(GPF) blends was studied with static and dynamic mechanical measurements for these blends. The classical theory of elasticity was applied to show the mechanical behavior of the rubber–polymer blend and to calculate the degree of crosslinking. From the dynamic mechanical measurements, the elastic modulus, internal friction, and thermal diffusivity were calculated. The observed variations were explained in view of the role played by both the vulcanizing system and the reinforcing carbon black. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1539–1544, 2003
Effect of polydimethylsiloxane macrodiol molecular weight on properties and morphology of polyurethane and polyurethaneurea
Authors: Adhikari Raju , Gunatillake Pathiraja A. , Bown Mark 
Published: September 2003

AbstractTwo series of polyurethanes and polyurethaneureas were prepared using a two‐step bulk‐solution polymerization procedure. Each series consisted of three polymers based on three molecular weights of α,ω‐bis(6‐hydroxyethoxypropyl) polydimethylsiloxane (PDMS): 940, 1913, and 2955. The soft segment in all cases was an 80:20 mixture of PDMS and poly(hexamethylene oxide) (MW 700), and the hard segment was based on 4,4′‐methylenediphenyl diisocyanate and mixed chain extenders (40 wt %). In the polyurethane (PU) series the chain extender was a 60:40 (mol) mixture of BDO and 1,3‐bis(4‐hydroxybutyl)1,1,3,3‐tetramethyldisiloxane (BHTD), whereas in the polyurethaneurea (PUU) series it was a 60:40 (mol) mixture of BHTD and 1,2‐ethylenediamine. The polymerization was carried out by preparing a prepolymer using a bulk polymerization procedure followed by chain extension in a solution of N,N‐dimethylacetamide. Polymers were characterized by size‐exclusion chromatography, tensile testing, differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). The number‐average molecular weights of the polymers in the PU series were in the range of 114,300–124,500, whereas they were in the 78,400–103,300 range for the PUU series. Polymers with good clarity and mechanical properties were obtained with PDMS‐940 and PDMS‐1913, but those obtained from PDMS‐2955, despite having good tensile strength, had a low percentage of elongation, high modulus, and poor clarity. DSC and DMTA results indicated that regardless of the PDMS molecular weight, the siloxane segments existed as a highly phase‐separated state. This poor compatibility was consistent with the low solubility of PDMS compared to that of the hard‐segment‐forming components. The polymers in the polyurethane series exhibited multiple melting endotherms, attributed to the melting of ordered domains from different hard segments. The combined heats of fusion were similar for the materials in the PU series. In contrast, the polymers in the PUU series showed a hard‐segment order that was significantly less defined, with the heat of fusion approximately a third to a half that of the materials in the polyurethane series. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1565–1573, 2003
Preparation and characterization of bismaleimide‐modified bisphenol dicyanate epoxy matrices
Authors: Dinakaran K. , Suresh Kumar R. , Alagar M. 
Published: September 2003

AbstractAn intercrosslinked network of epoxy matrix systems modified by cyanate ester (CE) and bismaleimide (BMI) was developed. Epoxy systems modified with 4%, 8%, and 12% (by weight) cyanate ester were made by using epoxy resin and cyanate ester, with diaminodiphenylmethane as the curing agent. The reaction between the cyanate ester and the epoxy resin during the cure process of cyanate ester–modified epoxy systems was studied using Fourier transform infrared spectroscopy. The cyanate ester–toughened epoxy systems were further modified with 4%, 8%, and 12% (by weight) bismaleimide (N,N′‐bismaleimido‐4,4′‐diphenylmethane). BMI–CE–Epoxy matrices were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis, and heat deflection temperature analysis. The matrices, in the form of castings, were characterized for their mechanical properties such as tensile strength, flexural strength, and unnotched Izod impact test as per ASTM methods. Mechanical studies indicated that the introduction of cyanate ester into epoxy resin improved the toughness and flexural strength, with a reduction in tensile strength and glass‐transition temperature, whereas the incorporation of bismaleimide into epoxy resin influenced the mechanical and thermal properties according to its percentage content. However, the introduction of both cyanate ester and bismaleimide influenced the mechanical properties according to their percentage content. DSC thermograms of cyanate ester–modified epoxy and BMI‐modified epoxy showed unimodal reaction exotherms. The thermal degradation temperature and heat distortion temperature of the cured BMI‐modified epoxy and CE‐epoxy systems increased with increasing bismaleimide content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1596–1603, 2003
Effect of alkali treatment on properties of the lignocellulose fabric Hildegardia
Authors: Rajulu A. Varada , Meng Y. Z. , Li X. H. , Rao G. Babu , Devi L. Ganga , Raju K. Mohana , Reddy R. Ramakrishna 
Published: September 2003

AbstractThe uniaxial natural fabric from the tree Hildegardia populifolia was treated with 5% aqueous NaOH solution for 0, 2, 4, 6, and 8 h, and the resulting changes were analyzed by density, Fourier infrared spectroscopic, X‐ray, polarized microscopic, and scanning electron microscopic techniques. On alkali treatment, absorption of water and elimination of hemicellulose in the fabric were observed. In each case, the tensile strength, modulus, and percent elongation at break were determined. The tensile strength, modulus, and density were found to be maximum at 4 h of alkali treatment. Hemicellulose was found on the surface of the untreated fabric. After 6 and 8 h of alkali treatment, some microcracks developed in the fabric. The area of the void region in the fabric increased with the duration of alkali treatment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1604–1608, 2003
Additive diffusion from LDPE slabs into contacting solvents as a function of solvent absorption
Authors: Helmroth I. E. , Dekker M. , Hankemeier Th. 
Published: September 2003

AbstractThis article describes the simultaneous diffusion of a migrant and a solvent in low density polyethylene (LDPE). The migrant (Irganox 1076) moves out of the slab, while the solvent (isooctane, n‐heptane or cyclohexane) moves inwards. Solvent absorption was measured separately by following the increase of the mass of the slab in time. It can be described by the Fick diffusion equation with a diffusivity depending on the solvent concentration, and an interface concentration depending on time. The final absorptions were 12% for isooctane, 14% for n‐heptane, and 29%for cyclohexane. Additive concentrations in the slab were determined at different positions by microtoming. Experiments were done for several contacting times. The concentration profiles were strongly affected by the solvent. A larger local solvent concentration increases the diffusivity of the migrant. The Fick equation with a migrant diffusivity depending on the solvent concentration gives a good description for the results with isooctane and n‐heptane. The description is less good for the measurements with cyclohexane (when the polymer swells strongly). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1609–1617, 2003
Wettability enhancement of polystyrene with electron cyclotron resonance plasma with argon
Authors: Guruvenket S. , Komath Manoj , Vijayalakshmi S. P. , Raichur A. M. , Mohan Rao G. 
Published: September 2003

AbstractPolystyrene cell‐culture substrates were treated with argon glow discharge to make their surfaces hydrophilic. The process was novel in that it used a microwave electron cyclotron resonance (ECR) source for polymer surface modification. The substrates were processed at different microwave powers and time periods, and the surface modification was assessed with by measurement of the water contact angle. A decrease in contact angle was observed with increasing microwave power and processing time. Beyond a certain limit of power and duration of exposure, however, surface deterioration occurred. The optimum conditions for making the surfaces hydrophilic without deterioration of the samples were identified. The plasma parameters were assessed by Langmuir probe measurement. Fourier transform infrared spectroscopy with attenuated total reflectance showed evidence for the induction of hydrophilicity on the surface. The surface micromorphology was examined with scanning electron microscopy. The results prove that the ECR glow discharge was an efficient method for enhancing the wettability of the polymer surfaces. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1618–1623, 2003