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Showing papers in "Journal of Applied Polymer Science in 2002"


Journal ArticleDOI
TL;DR: In this article, the thermal properties, crystallinity index, reactivity, and surface morphology of untreated and chemically modified fibers have been studied using differential scanning calorimetry (DSC), X-ray diffraction (WAXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), respectively.
Abstract: Plant fibers are rich in cellulose and they are a cheap, easily renewable source of fibers with the potential for polymer reinforcement. The presence of surface impurities and the large amount of hydroxyl groups make plant fibers less attractive for reinforcement of polymeric materials. Hemp, sisal, jute, and kapok fibers were subjected to alkalization by using sodium hydroxide. The thermal characteristics, crystallinity index, reactivity, and surface morphology of untreated and chemically modified fibers have been studied using differential scanning calorimetry (DSC), X-ray diffraction (WAXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), respectively. Following alkalization the DSC showed a rapid degradation of the cellulose between 0.8 and 8% NaOH, beyond which degradation was found to be marginal. There was a marginal drop in the crystallinity index of hemp fiber while sisal, jute, and kapok fibers showed a slight increase in crystallinity at caustic soda concentration of 0.8–30%. FTIR showed that kapok fiber was found to be the most reactive followed by jute, sisal, and then hemp fiber. SEM showed a relatively smooth surface for all the untreated fibers; however, after alkalization, all the fibers showed uneven surfaces. These results show that alkalization modifies plant fibers promoting the development of fiber–resin adhesion, which then will result in increased interfacial energy and, hence, improvement in the mechanical and thermal stability of the composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2222–2234, 2002

1,396 citations


Journal ArticleDOI
TL;DR: In this article, ultrasonic energy was used to uniformly disperse multiwalled carbon nanotubes (MWNTs) in solutions and to incorporate them into composites without chemical pretreatment.
Abstract: The aim of this article was to elucidate the basic relationships between processing conditions and the mechanical and electrical properties of multiwalled carbon nanotube reinforced polymer composites. In conventional chopped fiber reinforced polymer composites, uniform distributions of fibers throughout the matrix are critical to producing materials with superior physical properties. Previous methods have dispersed carbon nanotubes by aggressive chemical modification of the nanotubes or by the use of a surfactant prior to dispersion. 1, 2 Here, ultrasonic energy was used to uniformly disperse multiwalled nanotubes (MWNTs) in solutions and to incorporate them into composites without chemical pretreatment. Polystyrene (PS) solutions containing MWNTs were cast and spun to yield thin film MWNT composites. The rheology of PS/MWNT suspensions was modeled using the Carreau equation. MWNTs were found to align at the shear rates generated by the spin casting process. The tensile modulus and strain to failure of samples compared well to classical micromechanical models, increasing with MWNT loading. The composite films showed lower strains at the yield stress than neat PS films. The presence of MWNTs at 2.5 vol % fraction approximately doubles the tensile modulus, and transforms the film from insulating to conductive (surface resistivity, ρ, approaching 103 Ω/□). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2660–2669, 2002

547 citations


Journal ArticleDOI
TL;DR: In this paper, a batchwise mixture of poly(lactic acid) and five plasticizers was mixed in a batch-wise mixer and then pressed into films, which were analyzed by means of dynamic mechanical analysis and differential scanning calorimetry.
Abstract: Poly(lactic acid) (PLA) was blended with five plasticizers in a batchwise mixer and pressed into films. The films were analyzed by means of dynamic mechanical analysis and differential scanning calorimetry to investigate the properties of the blends. Triacetine and tributyl citrate proved to be effective as plasticizers when blended with PLA. The glass transition temperature of PLA decreased linearly as the plasticizer content was increased. Both plasticizers were miscible with PLA to an extent of similar to 25 wt %. At this point, the PLA seemed to be saturated with plasticizer and the blends tended to phase separate when more plasticizer was added. There were also signs of phase separation occurring in samples heated at 35, 50, and 80degreesC, most likely because of the material undergoing crystallization. The presence of the plasticizers induced an increased crystallinity by enhancing the molecular mobility. (Less)

367 citations


Journal ArticleDOI
TL;DR: In this article, the morphology and thermal properties of polylactide (PLA)/clay nanocomposites and microcomposites were compared with unfilled PLA, keeping the same thermomechanical history.
Abstract: Polylactide (PLA)/clay nanocomposites loaded with 3 wt % organomodified montmorillonite and PLA/clay microcomposites containing 3 wt % sodium montmorillonite were prepared by melt blending. We investigated the morphology and thermal properties of the nanocomposites and microcomposites and compared them with unfilled PLA, keeping the same thermomechanical history. The influence of the processing temperature on the structural characteristics of the investigated systems was determined. The investigations were performed with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), size exclusion chromatography (SEC), and polarized light microscopy (LM). XRD showed that the good affinity between the organomodified clay and the PLA was sufficient to form intercalated structure in the nanocomposite. The microcomposite featured a phase-separated constitution. DSC and LM studies showed that the nature of the filler affected the ordering of the PLA matrix at the molecular and supermolecular levels. According to TGA, the PLA-based nanocomposites exhibited improvement in their thermal stability in air. Reduced flammability, together with char formation, was also observed for nanocomposites, compared to the microcomposites and pure PLA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1497–1506, 2002

348 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed to use rigid matrix polymers with high glass transition transition (Tg) polymers to construct composite membranes with high permselectivity and equivalent productivity compared to existing membrane materials.
Abstract: Mixed matrix materials comprised of molecular sieve domains embedded in processable polymer matrices have the potential to provide membranes with higher permselectivity and equivalent productivity compared to existing membrane materials. It has been shown that successful mixed matrix materials can be formed using relatively low glass transition (Tg) polymers that have a favorable interaction with the sieves. This article extends this earlier work to include the use of more practical rigid matrix polymers with high Tgs that can ultimately be used in forming high-performance mixed matrix layers for composite membranes. Initial attempts to form mixed matrix materials based on high Tg polymers with a type 4A zeolite resulted in poor adhesion between the polymer and sieve. Correcting this problem was pursued in this study by forming the composite material close to the Tg of the polymer by addition of a plasticizer to match the matrix Tg with the solvent volatility. Forming the films at elevated temperatures presented substantial challenges, and this work discusses overcoming these challenges in detail. With some modifications in the film casting procedure, successful materials were achieved. Promising oxygen/nitrogen transport results are presented for these zeolite 4A–Matrimid®/plasticizer membranes, and this data compares favorably with predictions of the well-known Maxwell model for composite systems. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 881–890, 2002

330 citations


Journal ArticleDOI
TL;DR: In this paper, a novel nanostructure polymer-ceramic composite with a very high dielectric constant (er ∼110, a new record for the highest reported er value of a nanocomposite) was developed.
Abstract: Embedded capacitor technology can increase silicon packing efficiency, improve electrical performance, and reduce assembly cost compared with traditional discrete capacitor technology. Developing a suitable material that satisfies electrical, reliability, and processing requirements is one of the major challenges of incorporating capacitors into a printed wiring board (PWB). Polymer–ceramic composites have been of great interest as embedded capacitor material because they combine the processability of polymers with the high dielectric constant of ceramics. A novel nanostructure polymer–ceramic composite with a very high dielectric constant (er ∼110, a new record for the highest reported er value of a nanocomposite) was developed in this work. A high dielectric constant is obtained by increasing the dielectric constant of the epoxy matrix (er >6) and using the combination of lead magnesium niobate–lead titanate (PMN–PT)/BaTiO3 as the ceramic filler. This nanocomposite has a low curing temperature (<200°C); thus, it is multichip-module laminate (MCM-L) process-compatible. An embedded capacitor prototype with a capacitance density of 50 nF/cm2 was manufactured using this nanocomposite and spin-coating technology. The effect of the composite microstructure on the effective dielectric constant was studied. This novel nanocomposite can be used for integral capacitors in PWBs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1084–1090, 2002

329 citations


Journal ArticleDOI
TL;DR: The strength properties of polypropylene fibers were enhanced with single-wall carbon nanotubes (SWNTs) as mentioned in this paper, and the modulus increased 55% (from 60 to 93 g/denier).
Abstract: The strength properties of polypropylene fibers were enhanced with single-wall carbon nanotubes (SWNTs) Solvent processing was used to disperse SWNTs in a commodity polypropylene After the solvent was removed, the solid polymer was melt-spun and postdrawn into fibers of unusual strength For a 1-wt % loading of nanotubes, the fiber tensile strength increased 40% (from 90 to 131 g/denier) At the same time, the modulus increased 55% (from 60 to 93 g/denier) © 2002 Wiley Periodicals, Inc J Appl Polym Sci 86: 2079–2084, 2002

285 citations


Journal ArticleDOI
TL;DR: In this article, the effect of molecular weight of polypropylene (PP)-MA on clay dispersion and mechanical properties of nanocomposites was investigated, and the best overall mechanical properties were found for composites containing PP-MA having the highest molecular weight.
Abstract: Polypropylene (PP) nanocomposites were prepared by melt intercalation in an intermeshing corotating twin-screw extruder. The effect of molecular weight of PP-MA (maleic anhydride- modified polypropylene) on clay dispersion and mechanical properties of nanocomposites was investigated. After injection molding, the tensile properties and impact strength were measured. The best overall mechanical properties were found for composites containing PP-MA having the highest molecular weight. The basal spacing of clay in the composites was measured by X-ray diffraction (XRD). Nanoscale morphology of the samples was observed by transmission electron microscopy (TEM). The crystallization kinetics was measured by differential scanning calorimetry (DSC) and optical microscopy at a fixed crystallization temperature. Increasing the clay content in PP- MA330k/clay, a well-dispersed two-component system, caused the impact strength to decrease while the crystallization kinetics and the spherulite size remained almost the same. On the other hand, PP/PP-MA330k/clay, an intercalated three-component system containing some dispersed clay as well as the clay tactoids, showed a much smaller size of spherulites and a slight increase in impact strength with increasing the clay content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1562–1570, 2002

238 citations


Journal ArticleDOI
TL;DR: In this paper, longitudinal stiffeners were used in composite materials for use in composite composite materials, where plant fibers are of increasing interest for composite materials and waste management is easier than with glass fibers.
Abstract: Plant fibers are of increasing interest for use in composite materials. They are renewable resources and waste management is easier than with glass fibers. In the present study, longitudinal stiffn ...

219 citations


Journal ArticleDOI
TL;DR: In this paper, the solubility of different lignins (pine kraft, hardwood, ethoxylated, and maleinated) was determined in different resin systems (acrylated epoxidized soybean oil, hydroxylated soybeanoil, soy oil monoglyceride, and a commercial vinyl ester) to give an idea of the compatibility of lignin with the resin systems that were used.
Abstract: Some exploratory work was done to look at novel applications, such as filler use and comonomers, for lignin in thermosetting unsaturated polyesters and vinyl esters. The solubility of different lignins (pine kraft, hardwood, ethoxylated, and maleinated) was determined in different resin systems (acrylated epoxidized soybean oil, hydroxylated soybean oil, soy oil monoglyceride, and a commercial vinyl ester) to give an idea of the compatibility of lignin with the resin systems that were used. Further, the use of lignin as a filler was studied. An increase in the glass-transition temperature was noticed, and the modulus at 20°C decreased because of the plasticizing effect of lignin. The lignin was modified to improve its effect on the matrix properties by adding double bond functionality, thus making it possible to incorporate the lignin molecule in the resin through free-radical polymerization. Modified lignin was introduced in several resins by a reaction with maleic anhydride and epoxidized soybean oil and was tested for its effect on the solubility, glass-transition temperature, and modulus. This modification improved the solubility of lignin in styrene-containing resins, as well as the chemical incorporation of lignin in the resin. Moreover, lignin was used to treat the surfaces of natural hemp fibers to utilize lignin's natural affinity for cellulosic fibers. The idea was to cure the surface defects on the natural fibers and increase the bonding strength between the resin and fiber. An optimum improvement was noticed that depended on the amount of lignin covering the fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 323–331, 2002

219 citations


Journal ArticleDOI
TL;DR: In this article, the phase behavior, miscibility, and morphology of poly(L-lactic acid) and poly(butylene succinate) blends were investigated using differential scanning calorimetry, wide-angle X-ray diffraction, small-angle x-ray scattering techniques, and polarized optical microscopy.
Abstract: Blends of poly(L-lactic acid) (PLA) and poly(butylene succinate) (PBS) were prepared with various compositions by a melt-mixing method and the phase behavior, miscibility, and morphology were investigated using differential scanning calorimetry, wide-angle X-ray diffraction, small-angle X-ray scattering techniques, and polarized optical microscopy. The blend system exhibited a single glass transition over the entire composition range and its temperature decreased with an increasing weight fraction of the PBS component, but this depression was not significantly large. The DSC thermograms showed two distinct melting peaks over the entire composition range, indicating that these materials was classified as semicrystalline/semicrystalline blends. A depression of the equilibrium melting point of the PLA component was observed and the interaction parameter between PLA and PBS showed a negative value of −0.15, which was derived using the Flory–Huggins equation. Small-angle X-ray scattering revealed that, in the blend system, the PBS component was expelled out of the interlamellar regions of PLA, which led to a significant decrease of a long-period, amorphous layer thickness of PLA. For more than a 40% PBS content, significant crystallization-induced phase separation was observed by polarized optical microscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 647–655, 2002

Journal ArticleDOI
Jisheng Ma1, Shimin Zhang1, Zongneng Qi1, Ge Li1, Youliang Hu1 
TL;DR: In this article, the isothermal crystallization kinetics of polypropylene/montmorillonite (PP/MMT) nanocomposites synthesized via intercalation polymerization were investigated by using differential scanning calorimeter and polarizing optical microscope (POM).
Abstract: The isothermal crystallization kinetics of polypropylene/montmorillonite (PP/MMT) nanocomposites synthesized via intercalation polymerization were investigated by using differential scanning calorimeter and polarizing optical microscope (POM). The crystallinity of the nanocomposites decreased with the increase of the montmorillonite content, indicating that the MMT layers dispersed in the PP matrices confined the PP chains and hindered the crystallization of the PP chains. The POM photographs showed that the spherulites of the PP/MMT nanocomposites were greatly decreased in size as MMT was introduced. On the other hand, the crystallization rate increased dramatically with the increasing of MMT content. The interfacial free-energy per unit area perpendicular to PP chains in PP/MMT nanocomposites decreased with increasing MMT content, suggesting that the MMT layers acted as heterogeneous nuclei in the nucleation of crystallization. The nucleus density increased with the increasing of MMT content, leading to a positive effect on the crystallization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1978–1985, 2002

Journal ArticleDOI
TL;DR: In this paper, simple esterification and etherification reactions were applied to steam-exploded flax (Linum usitatissimum) with the aim of changing the surface properties through modification of fiber surface chemistry.
Abstract: Simple esterification and etherification reactions were applied to steam-exploded Flax (Linum usitatissimum) with the aim of changing the surface properties through modification of fiber surface chemistry. Native and chemically modified cellulose fibers were characterized in terms of thermal stability, surface chemistry, morphology, and crystal structure. Independent of the substituent nature, chemically modified fibers exhibited a thermal stability comparable to that of native cellulose. Introduction of the desired chemical groups at the fiber surface was demonstrated by TOF-SIMS analysis, whereas FTIR showed that the substitution reaction involved only a small fraction of the cellulose hydroxyls. No change of the native crystalline structure of cellulose fibers was caused by chemical modification, except in the case where ether substitution was carried out in water-isopropanol medium. Cellulose fibers with unchanged structure and morphology and carrying at the surface the desired chemical groups were obtained for reinforcing applications in polymer composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 38–45, 2002

Journal ArticleDOI
TL;DR: Amino semitelechelic poly(N-isopropylacrylamide) (PNIPAAm) was prepared by radical polymerization with aminoethanethiol hydrochloride as a chain-transfer agent as discussed by the authors.
Abstract: Amino semitelechelic poly(N-isopropylacrylamide) (PNIPAAm) was prepared by radical polymerization with aminoethanethiol hydrochloride as a chain-transfer agent. Semi-interpenetrating polymer network (semi-IPN) hydrogels, composed of alginate and amine-terminated PNIPAAm, were prepared by crosslinking with calcium chloride. From the swelling behaviors of semi-IPNs at various pH's and Fourier transform infrared spectra at high temperatures, the formation of a polyelectrolyte complex was confirmed from the reaction between carboxyl groups in alginate and amino groups in modified PNIPAAm. Semi-IPN hydrogels reached an equilibrium swelling state within 24 h. The water state in hydrogels, investigated by differential scanning calorimetry, showed that sample CAN55 [alginate/PNIPAAm (w/w) = 50/50] exhibited the lowest equilibrium water content and free water content among the hydrogels tested, which was attributed to its more compact structure compared to other samples and the high content of interchain bonding within the hydrogels. Alginate/PNIPAAm semi-IPN hydrogels exhibited a reasonable sensitivity to the temperature, pH, and ionic strength of swelling medium. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1128–1139, 2002

Journal ArticleDOI
TL;DR: In this paper, modified soy-based vegetable oil polyols were successfully incorporated as a replacement for conventional polyols to produce flexible slabstock polyurethane foams, and the effects of water levels and isocyanate content on the kinetics of the foaming reaction was investigated.
Abstract: Modified soy-based vegetable oil polyols were successfully incorporated as a replacement for conventional polyols to produce flexible slabstock polyurethane foams. The oil was characterized for its hydroxyl value and fatty acid composition. The modified oils had higher hydroxyl values and lower unsaturated acids than regular unmodified oils. Three different modified polyols were used to investigate the reactivity with isocyanates. The effects on the foaming reaction of two different isocyanates, namely TDI and MDI, were investigated. The reactions were also carried out with a mixture of polyols containing synthetic polyols and vegetable oil-based polyols to delineate the effect of each component. FTIR technique was used to identify the sequence of chemical reactions during the foaming process. The effect of water levels and isocyanate content on the kinetics of the foaming reaction was investigated. Information regarding the formation of hard and soft segments with the varying compositions was obtained. As the water content increased, the amount of the hard segment and urea formation increased in both soy oil polyols and synthetic polyols. Increased synthetic polyols in the mixture increased the rate of reaction and phase mixing due to the availability of primary hydroxyl groups. Scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS) were used to probe the morphology. As the water content increased, the cell size increased. At lower water content a more uniform cell structure was evident and at higher water levels hard domain size increased. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3097–3107, 2002

Journal ArticleDOI
TL;DR: In this article, major changes which have occured to satisfy the consumer's demand in terms of comfort, easy care, health, and hygiene are reviewed, with increasing awareness of environmental concerns, various chemical finishes for processing of textiles have been discussed.
Abstract: With increasing awareness of environmental concerns, various chemical finishes for processing of textiles have been discussed. In this paper major changes which have occured to satisfy the consumer's demand in terms of comfort, easy care, health, and hygiene are reviewed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 631–659, 2002

Journal ArticleDOI
TL;DR: In this paper, the mechanical properties of poly(3-hydroxybutyrate- co-3hydroxyvarelate) (PHBV) composites, reinforced with short abaca fibers prepared by melt mixing and subsequent injection molding, were investigated and compared with PHBV composites reinforced with glass fiber (GF).
Abstract: The mechanical properties of poly(3-hydroxybutyrate- co-3-hydroxyvarelate) (PHBV) composites, reinforced with short abaca fibers prepared by melt mixing and subsequent injection molding, were investigated and compared with PHBV composites reinforced with glass fiber (GF). The influences of fiber length, fiber content, and surface treatment of the natural fiber on the mechanical properties were evaluated. Regarding fiber length, the tensile properties had a maximum at a fiber length of about 5 mm. The flexural properties of the PHBV/abaca composite were improved by the surface treatment of abaca with butyric anhydride and pyridine for 5 h because of the increase of interfacial adhesiveness between the matrix polyester and the surface-esterified fiber, as is obvious from the SEM micrographs. The flexural and tensile properties of PHBV/treated abaca composite were comparable to those of PHBV/GF composite, except for tensile modulus, compared with the same weight fraction of fiber. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 129–138, 2002

Journal ArticleDOI
TL;DR: In this paper, a new kind of polyol based on rape seed oil for use in rigid polyurethane foam was synthesized and characterized, and the reaction process was monitored by means of a novel on-line infrared spectrometer.
Abstract: A new kind of polyol based on rape seed oil for use in rigid polyurethane foam was synthesized and characterized. The synthesis of such a polyol was divided into two steps. The first step was the hydroxylation of the double bonds existing in the long chains of the unsaturated aliphatic hydrocarbon of rape seed oil with peroxy acid. The second step was use of the alcoholysis of the hydroxylated rape seed oil with triethanolamine to increase the hydroxyl value of the product. The reaction process was monitored by means of a novel on-line infrared spectrometer. Rigid polyurethane foam was produced with this rape seed oil based polyol and some physical properties of the foam were examined and compared with a reference foam. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 591–597, 2002; DOI 10.1002/app.10311

Journal ArticleDOI
TL;DR: In this paper, the electrical conductivity of carbon-filled polymers was studied by adding four single fillers to nylon 6,6 and polycarbonate in increasing concentrations, and the results showed that the model proposed by Mamunya, which takes into account the filler aspect ratio and the surface energy of the filler and polymer, most closely matched the conductivity data.
Abstract: The electrical conductivity of polymeric materials can be increased by the addition of carbon fillers, such as carbon fibers and graphite. The resulting composites could be used in applications such as interference shielding and electrostatic dissipation. Electrical conductivity models are often proposed to predict the conductivity behavior of these materials in order to achieve more efficient material design that could reduce costly experimental work. The electrical conductivity of carbon-filled polymers was studied by adding four single fillers to nylon 6,6 and polycarbonate in increasing concentrations. The fillers used in this project include chopped and milled forms of polyacrylonitrile (PAN) carbon fiber, ThermocarbTM Specialty Graphite, and Ni-coated PAN carbon fiber. Material was extruded and injection-molded into test specimens, and then the electrical conductivity was measured. Data analysis included a comparison of the results to existing conductivity models. The results show that the model proposed by Mamunya, which takes into account the filler aspect ratio and the surface energy of the filler and polymer, most closely matched the conductivity data. This information will then be used in the development of improved conductivity models. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1341–1356, 2002

Journal ArticleDOI
TL;DR: In this paper, the commercial grade of isotactic polypropylene was modified by a specific β-nucleating agent in a broad concentration range and the supermolecular structure was characterized by X-ray scattering and correlated with mechanical behavior.
Abstract: The commercial grade of isotactic polypropylene was modified by a specific β-nucleating agent in a broad concentration range. The supermolecular structure of the specimens prepared by injection molding was characterized by X-ray scattering and correlated with mechanical behavior. It was found that at a critical nucleant concentration of 0.03 wt % the content of the β-modification virtually reaches a saturation level. With further addition of the nucleant, the β-phase content increases only slightly. The long period passes through a distinct maximum at the same nucleant concentration. This singularity in structure remarkably correlates with a minimum of the yield stress and maxima of strain at break and fracture toughness. Such general behavior is also reflected in the correlation between the β-phase concentration and fracture toughness profiles along the injection-molded bars. It is suggested that in the critically nucleated material an optimum thickness of the amorphous interlayer with connecting chains between the β-crystallites is established, rendering the material the highest possible ductility and toughness. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1174–1184, 2002

Journal ArticleDOI
TL;DR: In this article, a thermally blending of starch and PLA in the presence of methylenediphenyl diisocyanate (MDI) enhanced the mechanical properties of the blends.
Abstract: Poly(lactic acid) (PLA) and wheat starch are biodegradable polymers derived from renewable sources. A previous study showed that thermally blending starch and PLA in the presence of methylenediphenyl diisocyanate (MDI) enhanced the mechanical properties of the blends. In this work, blends of PLA with various levels of wheat starch and MDI were hot mixed at 180°C then hot-pressure molded at 175°C to form test specimens. The blends were characterized for mechanical properties, fracture microstructure, and water absorption. Pure PLA had a tensile strength of 62.7 MPa and elongation of 6.5%. The blend with 45% wheat starch and 0.5 wt % MDI gave the highest tensile strength of about 68 MPa with about 5.1% elongation. The blend with 20% starch and 0.5 wt % MDI had the lowest tensile strength of about 58 MPa with about 5.6% elongation. Dynamic mechanical analysis showed that storage modulus increased and tan δ decreased as starch level increased, but almost leveled off when starch level reached 45% or higher. Water absorption of the blends increased significantly with starch content. Yet the blend, if water proofed on its surface, has potential for short-term disposable applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1257–1262, 2002; DOI 10.1002/app.10457

Journal ArticleDOI
TL;DR: In this article, the performance of the fibers as a reinforcing material in the composites was analyzed using DTG and DSC technique. But the results showed that the reduction in percentage moisture loss for the fibers treated with alkali for 6 and 8 h could be the result of the increased crystallinity of the fiber.
Abstract: Jute fibers were treated with 5% NaOH solution for 2, 4, 6, and 8 h to study the performance of the fibers as a reinforcing material in the composites. Thermal analysis of the fibers was done by the DTG and DSC technique. The moisture desorption was observed at a lower temperature in the case of all the treated fibers, which might be a result of the increased fineness of the fibers, which provides more surface area for moisture evaporation. The decrease in percentage moisture loss for the fibers treated with alkali for 6 and 8 h could be the result of the increased crystallinity of the fibers. The percentage degradation of the hemicellulose decreased considerably in all the treated fibers, conforming to the fact that the hemicellulose content was lowered on alkali treatment. The decomposition temperature for α-cellulose was lowered to 348°C from 362.2°C for all the treated fibers, and the residual char formation increased to a significant extent. The enthalpy for the thermal degradation of α-cellulose showed a decreasing trend for the fibers treated for 2 and 4 h, which could be caused by the initial loosening of the structure, followed by an increase in the enthalpy value in the case of the 6- and 8-h-alkali-treated fibers resulting from increased crystallinity, as evident from the X-ray diffraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2594–2599, 2002

Journal ArticleDOI
TL;DR: In this article, the degree of moisture absorption was found to be dependent on the modification of matrix, the weight percentage, mesh size, and surface treatment of wood flours, and the extent of such increment decreased with increasing the immersion temperature.
Abstract: The moisture absorption and mechanical properties of wood flour–filled polypropylene composites in a hydrothermal environment have been studied by immersing the composites in water at 23, 60, and 100°C. The degree of moisture absorption was found to be dependent on the modification of matrix, the weight percentage, mesh size, and surface treatment of wood flours. It increased with increasing the immersion temperature. The tensile strength of all composites with wood flours of different contents, mesh sizes, and surface treatments increased after immersion in water baths of various temperatures, to either greater or lesser extents. The flexural strength and modulus followed a similar trend when immersed in water at ambient temperature. However, the contrary was true for composites when immersed in 60 and 100°C water baths. The impact strength increased after immersion in water at each immersion temperature, and the extent of such increment decreased with increasing the immersion temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2824–2832, 2002

Journal ArticleDOI
TL;DR: Wile et al. as discussed by the authors investigated the TO-LDP Ebiodegradation process and found that polyethylen-polyethylen can be used to improve the performance of the mining process.
Abstract: Differentia lscannin gcalorimetr y(DSC) ,X-ra ydiffractio n(XRD) ,Fourier transfor minfrare dspectroscop y(FTIR )an dscannin gelectro nmicroscop y(SEM )were use dt odetermin emorphological ,structura lan dsurfac echange s(biodegradation )on thermo-oxidize d(80°C ,1 5days )low-densit ypolyethylen e(TO-LDPE )incubate dwith Aspergillu snige ran dPenicilliu mpinophilu mfungi ,wit han dwithou tethano las cosubstrat efo r3 1months .TO-LDP Emineralizatio nb yfung iwa sals oevaluated. Significantl ymorphologica lan dstructura lfina lchange so nbiologicall ytreate dTO- LDP Esample swer eobserved .Decrease st othre eunit so ncrystallinit yan dcrystalline lamella rthicknes s(0. 4-1. 8A) ,an dincrease si nsmall-crystal sconten t(u pt o3.2% )and mea ncrystallit esiz e(8. 4-1 4A )wer eregistered .A noxidatio ndecreas e(almos ttwice) o nsample swithou tethano lwit hrespec tt oth econtro lwa sobserved ,whil ei nthose wit hethano li twa sincrease d(u pt o2. 5times) .Doubl ebon dinde xincrease dmore tha ntwic efro m2 1t o3 1months .Th ehighe rTO-LDP Echange san dfungi-LDPE interactio nwa sobserve di nsample swit hethanol ,suggestin gtha tethano lfavor sthe TO-LDP Ebiodegradation ,a tleas ti ncas eo fP .pinophilum ,probabl yb ymean so fa cometaboli cprocess .Mineralizatio no f0.5 0% an d0.5 7% fo rA .niger ,an do f0.6 4% and 0.3 7% fo rP .pinophilu mwer eobtained ,fo rsample swit han dwithou tethanol ,respec- tively .A mode lt oexplai nmorphologica lan dstructura lchange so nbiologicall ytreated TO-LDP Ei sals oproposed . ©200 2Joh nWile y& Sons ,Inc .J App lPoly mSc i83 :305-314 ,2002 Ke ywords :polyethylen ebiodegradation ;cometabolism ;Aspergillu sniger ;Penicil- liu mpinophilum

Journal ArticleDOI
TL;DR: In this article, a new method for the grafting of cyclodextrins (CDs) onto cotton or wool fabrics was described, which was carried out in the presence of polycarboxylic acids, such as 1,2,3,4-butanetetetracarboxyl acid, citric acid, or polyacrylic acid.
Abstract: In this paper we describe a new method for the grafting of cyclodextrins (CDs)onto cotton or wool fabrics. The novelty principally concerns the chemical approach of the grafting reaction that was carried out in the presence of polycarboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid, citric acid, or polyacrylic acid. All types of native or CD derivatives could be used successfully as long as they carried enough remaining hydroxyl groups. For example, the amount of native β-CD fixed onto the fabrics increased up to 12% in weight, whereas this value decreased to only 3% for the randomly methylated derivative of β-CD (RAMEB). We observed that phosphorous salts, such as sodium mono- and dihydrogen phosphate or sodium dihydrogen hypophosphite, catalyzed the reaction. On the other hand, the conventional and convenient pad–dry–cure technique that is currently used at the industrial scale in textile processing was applied. We report that the polycarboxylic acids play the role of linking agent through an esterification (or amidification) reaction with the OH (or NH2) groups of both CD and cotton (or wool) fibers. In addition, this reaction could lead to the graft of a copolymer formed between CD and the polycarboxylic acid. The reaction yield depends on the concentration and nature of the aforementioned reactants and catalysts and on the curing conditions (time and temperature). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1449–1456, 2002

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TL;DR: An overview of fiber applications in cementitious composites is presented in this article, where the socioeconomic considerations surrounding materials development in civil engineering in general, and fiber reinforced cementitious materials in particular, are described.
Abstract: This article presents an overview of fiber applications in cementitious composites. The socio-economic considerations surrounding materials development in civil engineering in general, and fiber reinforced cementitious materials in particular, are described. Current FRC appliations are summarized, and the where, how, and why fibers are used in these applications, are documented. An attempt is made to extract common denominators among the widely varied applications. The R&D and industrial trends of applying fibers in enhancing structural performance are depicted. An actual case study involving a tunnel lining constructed in Japan is given to illustrate how a newly proposed structural design guideline takes into account the load carrying contribution of fibers. Composite properties related to structural performance are described for a number of FRCs targeted for use in load carrying structural members. Structural applications of FRCs are currently under rapid development. In coming years, it is envisioned that the ultra-high performance FRC, with ductility matching that of metals, will be commercially exploited in various applications. Highlights of such a material are presented in this article. Finally, conclusions on market trends are drawn, and favorable fiber characteristics for structural applications are provided.

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TL;DR: In this article, two grades of rice husk ash (low and high carbon contents) were used as filler in natural rubber and the effect of silane coupling agent, bis(3-triethoxysilylpropyl)tetrasulfane (Si-69), on the properties of ash-filled vulcanizates was investigated.
Abstract: Rice husk ash is mainly composed of silica and carbon black remaining from incomplete combustion. Both silica and carbon black have long been recognized as the main reinforcing fillers used in the rubber industry to enhance certain properties of rubber vulcanizates, such as modulus and tensile strength. In this study, two grades of rice husk ash (low- and high-carbon contents) were used as filler in natural rubber. Comparison was made of the reinforcing effect between rice husk ashes and other commercial fillers such as talcum, china clay, calcium carbonate, silica, and carbon black. Fourier transform infrared spectroscopy (FTIR) analysis was employed to study the presence of functional groups on the ash surface. The effect of silane coupling agent, bis(3-triethoxysilylpropyl)tetrasulfane (Si-69), on the properties of ash-filled vulcanizates was also investigated. It was found that both grades of rice husk ash provide inferior mechanical properties (tensile strength, modulus, hardness, abrasion resistance, and tear strength) in comparison with reinforcing fillers such as silica and carbon black. However, the mechanical properties of the vulcanizates filled with rice husk ash are comparable to those filled with inert fillers. The addition of silane-coupling agent has little effect on the properties of the ash-filled vulcanizates. This is simply due to the lack of silanol groups on the ash surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2485–2493, 2002

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TL;DR: In this paper, Silk fibroin and microcrystalline cellulose (cellulose whisker) composite films with varied compositions were prepared by casting mixed aqueous solution/suspensions of the two components.
Abstract: Silk fibroin–microcrystalline cellulose (cellulose whisker) composite films with varied compositions were prepared by casting mixed aqueous solution/suspensions of the two components. Silk fibroin was dissolved in 10M LiSCN followed by dialysis; a cellulose whisker suspension was prepared by sulfuric acid hydrolysis of tunicate cellulose. Macroscopically homogeneous films were obtained at all mixing ratios. While the Young's modulus of the composite films showed a linear, additive dependence on the mixing ratio, the tensile strength and ultimate strain showed a maximum at a 70–80% cellulose content, reaching five times those of fibroin-alone or cellulose-alone films. At the same mixing ratio, infrared spectra of the composite films showed a shift of the amide I peak from 1654 to 1625 cm−1, indicating the conformational change of fibroin from a random coil to a β structure (silk II) at the whisker–matrix interface. This change seems to be induced by contact of fibroin molecules with a highly ordered surface of cellulose whisker. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3425–3429, 2002

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TL;DR: The glass transition temperature of the hard-segment phase and the storage modulus of segmented polyurethane increased substantially in the presence of tethered nano-sized layered silicates from montmorillonite compared with their pristine state.
Abstract: The glass transition temperature of the hard-segment phase and the storage modulus of segmented polyurethane increased substantially in the presence of a small amount of tethered nano-sized layered silicates from montmorillonite compared with their pristine state (by 44°C and by 2.8-fold, respectively). Furthermore, the heat resistance and degradation kinetics of these montmorillonite/polyurethane nanocomposites were enhanced, as shown by thermogravimetric analysis. In particular, a 40°C increase in the degradation temperature and a 14% increase in the degradation activation energy occurred in polyurethane containing 1 wt % trihydroxyl swelling agent-modified montmorillonite compared to that of the pristine polyurethane. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1741–1748, 2002

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TL;DR: In this paper, the authors discuss the methods of interface modification of composites based on raw wood flakes and high-density polyethylene (HDPE) and the effects of these modifications on composite properties.
Abstract: This article discusses the methods of interface modification of composites based on raw wood flakes and high-density polyethylene (HDPE) and the effects of these modifications on composite properties. An HDPE matrix was modified by a reaction with maleic anhydride (MA) in a twin-screw extruder and then compounded with wood flakes to produce wood–polyethylene composites. Wood flakes were modified by a reaction with a silane coupling agent in an aqueous medium before being compounded with HDPE to produce silane-modified WPCs. Differential scanning calorimetry and Fourier transform infrared spectroscopy data provide evidence for the existence of a polyethylene (PE)–silane-grafted wood structure, which acts as a compatibilizer for wood flakes and PE. The results of MA-modified composites indicate that some maleated HDPE is reacting with wood through esterification to form a compatibilizer for wood flakes and HDPE. Significant improvements in tensile strength, ductility, and Izod impact strength were obtained. Scanning electron micrographs provide evidence for strong interactions between the wood flakes and the matrix agent. The results indicate that 1–2 wt % MA modification on HDPE and 1–3 wt % silane treatment on wood flakes provide WPCs with the optimum properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2505–2521, 2002