Showing papers in "Polymer Engineering and Science in 2009"
TL;DR: In this article, the use of pretreated natural fibers in polymer matrix-based composites has been reviewed and the effect of surface modification of natural fibers on the properties of fibers and fiber reinforced polymer composites is also discussed.
Abstract: In recent years, natural fibers reinforced composites have received much attention because of their lightweight, nonabrasive, combustible, nontoxic, low cost and biodegradable properties. Among the various natural fibers; flax, bamboo, sisal, hemp, ramie, jute, and wood fibers are of particular interest. A lot of research work has been performed all over the world on the use of natural fibers as a reinforcing material for the preparation of various types of composites. However, lack of good interfacial adhesion, low melting point, and poor resistance towards moisture make the use of natural fiber reinforced composites less attractive. Pretreatments of the natural fiber can clean the fiber surface, chemically modify the surface, stop the moisture absorption process, and increase the surface roughness. Among the various pretreatment techniques, graft copolymerization and plasma treatment are the best methods for surface modification of natural fibers. Graft copolymers of natural fibers with vinyl monomers provide better adhesion between matrix and fiber. In the present article, the use of pretreated natural fibers in polymer matrix-based composites has been reviewed. Effect of surface modification of natural fibers on the properties of fibers and fiber reinforced polymer composites has also been discussed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
1,201 citations
TL;DR: In this article, the authors show that the field of joining polymers, polymeric composites, and polymer-metal hybrid structures for industrial applications is still a growing research and development area.
Abstract: The development of new materials and fabrication techniques has become a matter of success for industrial sectors such as transportation. Polymers, polymeric composites, and polymer–metal structures are being increasingly employed in several products mainly due to the associated weight savings. The main joining methods for polymer and polymeric composites are mechanical fastening, adhesive bonding, and welding. On the other hand, polymer–metal structures are more difficult to join by traditional joining methods, mostly due to their strong dissimilar physical–chemical features. Constant efforts on developing improved alternative joining techniques for these hybrid structures, such as the FricRiveting and injection over molding, have contributed to the dissemination of such structures in industrial applications. This work shows that the field of joining of polymers, polymeric composites, and polymer–metal hybrid structures for industrial applications is still a growing research and development area. This is due to the increasing aspirations for more environmental-friendly technologies and lightweight materials. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
327 citations
TL;DR: In this article, the effects of DCP content on the mechanical properties, thermal and rheological behavior, phase morphology as well as the toughening mechanism of the blends were investigated.
Abstract: Biodegradable polymer blends consisting of poly(L-lactic acid) (PLLA) and poly(butylene succinate) (PBS) were prepared in the presence of dicumyl peroxide (DCP). The effects of DCP content on the mechanical properties, thermal and rheological behavior, phase morphology as well as the toughening mechanism of the blends were investigated. The notched Izod impact strength of PLLA/PBS (80/20) blend significantly increased after the addition of 0.05–0.2 phr DCP, but the strength and modulus monotonically decreased with increasing DCP content. PBS acted as a nucleating agent at the environmental temperature below its melting temperature and accelerated the crystallization rate of PLLA but had little effect on its final degree of crystallinity. The degree of crystallinity of PBS and the cold crystallization ability of PLLA gradually reduced with increasing DCP content. The addition of DCP induced an increase in viscosity of the blends at low frequencies as well as finer dispersion of PBS particles and better interfacial adhesion between PLLA and PBS, indicating the in situ compatibilization occurred between the two components. The optical clarity of PLLA/PBS blends was significantly improved after the addition of DCP, which was in accordance with the crystallization behavior and phase structure of the blends. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
238 citations
TL;DR: In this paper, a conical metal wire-coil was used as spinneret for needleless electrospinning of PVA nanofibers, and multiple polymer jets were observed to generate on the coil surface.
Abstract: In this article, we have demonstrated a novel needleless electrospinning of PVA nanofibers by using a conical metal wire-coil as spinneret. Multiple polymer jets were observed to generate on the coil surface. Up to 70kV electric voltage can be applied to this needleless electrospinning nozzle without causing 'corona discharge.' Compared with conventional needle electrospinning, this needleless electrospinning system produced finer nanofibers on a much larger scale, and the fiber processing ability showed a much greater dependence on the applied voltage. Finite element calculation indicates that the electric field intensity profiles for the two systems are also quite different. This novel concept of using wire coil as the electrospinning nozzle will contribute to the further development of new large-scale needleless electrospinning system for nanofiber production.
213 citations
TL;DR: In this article, single-walled carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) composites were prepared using coagulation method and the electrical conductivity and the electromagnetic interference (EMI) shielding of SWNT/PMMA composites over the X-band (8-12 GHz) and the microwave (200-2000 MHz) frequency range were investigated.
Abstract: Single-walled carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) composites were prepared using coagulation method. The electrical conductivity and the electromagnetic interference (EMI) shielding of SWNT/PMMA composites over the X-band (8–12 GHz) and the microwave (200–2000 MHz) frequency range have been investigated. The electrical conductivity of composites increases with SWNT loading by 13 orders of magnitude, from 10−15 to 10−2 Ω−1 cm−1 with a percolation threshold of about 3 wt% SWNTs. The effect of the sample thickness on the shielding effectiveness has been studied, and correlated to the electrical conductivity of composites. The data suggest that SWNT/PMMA composites containing higher SWNT loading (above 10 wt%) be useful for EMI shielding and those with lower SWNT loading be useful for electrostatic charge dissipation. The dominant shielding mechanism of SWNT/PMMA composites was also discussed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
185 citations
TL;DR: In this article, the antimicrobial properties of carvacrol containing nanocomposite were tested, showing a significant activity against several bacterial strains, which was preserved in presence of the clay.
Abstract: Nanocomposite films based on low-density polyethylene (LDPE) containing carvacrol were prepared and characterized with the aim to get antimicrobial active packaging. Organo-modified montmorillonite (MMT) was used as filler. The weak interaction between LDPE and clay led to the formation of intercalated systems. On the other hand, strong interaction between carvacrol and organosilicate allowed a good dispersion of the oil into the clay galleries, promoting the swelling of MMT stacks and a higher polymer/clay interface. As a result, carvacrol was protected against thermal degradation and its release from the films was efficiently delayed. Moreover, outstanding thermal oxidative stability as well as improved oxygen barrier properties were detected in the nanocomposite containing carvacrol. The presence of clay and carvacrol also increased LDPE crystallinity, due to an enhanced nucleation activity, while the mechanical properties of the films were slightly affected. The antimicrobial properties of carvacrol containing films were tested, showing a significant activity against several bacterial strains, which is preserved in presence of the clay. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
149 citations
TL;DR: In this paper, the effects of adding epoxy-functionalized chainextender (CE) and processing conditions such as die temperature on the cell morphology, volume expansion ratio (VER), open cell content (OCC), and crystallization of microcellular extruded polylactide (PLA) were investigated.
Abstract: The effects of adding epoxy-functionalized chain-extender (CE) and processing conditions such as die temperature on the cell morphology, volume expansion ratio (VER), open cell content (OCC), and crystallization of microcellular extruded polylactide (PLA) were investigated. When compared with pure PLA, the addition of talc decreased the average cell size and increased the cell density. Moreover, the simultaneous addition of talc and CE led to denser and more uniform cell structure up until 1.0% CE content. In general, the volume expansion ratio and open cell content of all the formulations decreased with the die temperature. The addition of talc decreased both VER and OCC, whereas the addition of CE increased both. The die temperature did not affect the degree of crystallinity significantly. The addition of talc increased the crystallinity, but the addition of CE decreased it. Finally, the molecular weight of PLA increased significantly with the addition of CE. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
149 citations
TL;DR: In this article, the thermal conductivity and mechanical properties of aluminum nitride (AIN) and linear low-density polyethylene (LLDPE) composites were investigated using hot disk thermal analyzer and differential scanning calorimeter.
Abstract: To acquire polymer composites with high thermal conductivity and mechanical properties, the aluminum nitride (AIN) microparticles modified with titanate coupling reagent of isopropyltrioleictitanate (NDZ-105) were employed to blend linear low-density polyethylene (LLDPE) via powder mixing method. Thermal conductive coefficient of the AIN/LLDPE composites was measured using hot disk thermal analyzer, and the thermal stability characteristics of AIN/LLDPE composites were mainly investigated via thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC). The results indicated that the use of AIN particles modified by NDZ-105 significantly enhanced thermal conductivity and mechanical properties of AIN/LLDPE composites. The thermal conductivity coefficient λ was 1.0842 W/mk with 30% volume fraction of AIN, about three times higher than that of native LLDPE. The tensile strength of composites was maximum (17.42 MPa) with 20% mass fraction of AIN. DSC analyses results indicated that AIN had an influence on the melting temperature and the crystallinity of LLDPE. Additionally, TGA analyses showed that the thermal stability of LLDPE was significantly increased with addition of AIN.
118 citations
TL;DR: In this article, the nonionic surfactant sorbitan monostearate was used to improve the dispersion properties of the hydrophilic cellulose in hydrophobic matrix and to prevent the formation of aggregates.
Abstract: Cellulose nanoparticles obtained by acid hydrolysis of cellulose paper were used to reinforce polystyrene composite films. The nonionic surfactant sorbitan monostearate was utilized to improve the dispersion properties of the hydrophilic cellulose in hydrophobic matrix and to prevent the formation of aggregates. Turbidity tests were used to measure dispersion stability of the cellulose crystallites in the hydrophobic solvent used in the composite manufacture. A correlation was found between the dispersion stability in solvent and the formation of aggregates in the polymeric composites. Nanocomposite films were processed using a casting/evaporation technique. Thermal and mechanical properties of processed composites were studied by differential scanning calorimetry (DSC) and dynamical mechanical analyses (DMA), respectively. The results showed that the optimum addition of surfactant produced better dispersion of the cellulose particles in the polystyrene matrix and improved the mechanical properties of the resulting composite due to an enhanced compatibility. POLYM. ENG. SCI., 49:2054–2061, 2009. a 2009 Society of Plastics Engineers
109 citations
TL;DR: In this article, a natural polyol was obtained from tung oil (TO) to further be used in the formulation of rigid polyurethane polymers, which was carried out in two steps: first hydroxylation of the double bonds in the fatty acid chains of the unsaturated oil and then, alcoholysis of the hydroxyated oil with triethanolamine.
Abstract: A natural polyol was obtained from tung oil (TO) to be further used in the formulation of rigid polyurethane polymers. The synthesis of the polyol was carried out in two steps: first hydroxylation of the double bonds in the fatty acid chains of the unsaturated oil and then, alcoholysis of the hydroxylated oil with triethanolamine. The chemical analysis (titration, FTIR, 1H NMR) of the unmodified TO, the hydroxylated tung oil, and the alcoholized hydroxylated tung oil-based polyol indicates that the hydroxyl content increased significantly after the hydroxylation and alcoholysis reactions. The modified TO was subsequently used as the polyol component in the formulation of reinforced rigid polyurethanes. Wood flour (WF) and microcrystalline cellulose were the reinforcements chosen to be incorporated in these materials. Physical, thermal, and mechanical properties of the neat and reinforced polyurethanes were measured and analyzed. An excellent dispersion of the WF in the matrix, confirmed by scanning electron microscopy, was observed in the polyurethane reinforced with WF. This system also presented the highest modulus and strength. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
105 citations
TL;DR: In this article, the preparation, characterization, and physical properties of nanoparticies-filled composites consisting of multiwall carbon nanotubes (MWCNT) and styrene-butadiene rubber and nitrile-butane rubber were described.
Abstract: The present article describes preparation, characterization, and physical properties of nanoparticies-filled composites consisting of multiwall carbon nanotubes (MWCNT) and styrene-butadiene rubber and nitrile-butadiene rubber. The reinforcing MWCNT fillers were synthesized by chemical vapor deposition on iron and cobalt catalysts supported by calcium carbonate substrates. These MWCNT were further treated with nitric acid to produce hydroxyl and carbonyl functional groups on the carbon nanotubes (CNT) surfaces. Of particular importance is that these functionalized CNTs were found to exert profound influence on the elastomeric matrices, particularly the vulcanization activation energy, resistance to solvent swelling, enhanced glass transition temperature, and improved storage and loss moduli.
TL;DR: In this article, the viscosity and mechanical properties of bio-based crosslinkers with two reactive diluents: a styrene and an acrylated fatty acid methyl ester-based (AFAME) monomer were measured and analyzed.
Abstract: Resins containing plant oil-based cross-linkers were studied with two reactive diluents: a styrene and an acrylated fatty acid methyl ester-based (AFAME) monomer. Acrylated epoxidized soybean oil and maleinated castor oil monoglyceride were bio-based cross-linkers used. The viscosity and mechanical properties of the resulting polymers were measured and analyzed. Both bio-based cross-linkers prepared using the modified AFAME as diluent had a fairly high viscosity, so blends of AFAME and styrene were needed to meet the viscosity requirements established by the composite industry (<1000 cP at room temperature). In addition, the glass transition temperature (Tg) and stiffness of bio-based cross-linker/AFAME polymers were significantly lower than the resin/styrene polymers. Ternary blends of maleinated castor oil monoglyceride with AFAME and styrene improved the mechanical properties to acceptable comparable values (storage modulus at 30°C ∼ 1200 MPa and Tg ∼ 100°C). The addition of 5 wt% of chemically modified lignin led to an improvement in the mechanical properties of the polymeric matrix but caused an increase in the viscosity. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this article, particle tracking the local residence time distributions (RTDs) of a co-rotating twin-screw extruder using computational fluid dynamics is used to analyze the distributive mixing performance and overall efficiency of different types of kneading discs.
Abstract: This work aims at simulation by particle tracking the local residence time distributions (RTDs) of a co-rotating twin-screw extruder using computational fluid dynamics Simulated results follow reasonably well the trend of experimental results obtained by an in-line measuring instrument for different screw configurations and feed rates To analyze the distributive mixing performance and overall efficiency of different types of kneading discs (KDs), mixing parameters such as area stretch ratio, instantaneous efficiency, and time-average efficiency are calculated Among KDs with stagger angles 45°, 60°, and 90°, the 90/10/64 with disc gaps is most efficient in terms of distributive mixing The effects of the disc width and disc gap on the local RTD and distributive mixing are also discussed This provides a numerical tool for assessing point-by-point information on the local RTD, flow, and mixing along the screw extruder POLYM ENG SCI, 2009 © 2009 Society of Plastics Engineers
TL;DR: In this paper, a biodegradable polyester, poly(butylene adipate-co-terephthalate) (PBAT) was blended with PLA to improve melt properties of PLA.
Abstract: In resent years, poly(lactic acid) (PLA) foams have been studied to replace traditional polymer foams in packaging field. Unfortunately, the foaming rate of PLA is low due to its low viscosity and elasticity. To overcome these shortcomings, a biodegradable polyester, poly(butylene adipate-co-terephthalate) (PBAT) was blended with PLA to improve melt properties of PLA. Additionally, maleic anhydride (MAH) and 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (L101) were added to improve the compatibility of PLA with PBAT. The blends were extruded into foams using a twin-screw extruder. The properties of extrudates were characterized by FTIR, DSC, ARES Rheometer, and SEM. The results show that complex viscosity of PLA/PBAT blend increases by nearly 100% compared with pure PLA. Meanwhile, cell structure of foamed PLA/PBAT blend is much larger and the distribution of cells is more homogenous. The foaming rate of PLA/PBAT blend foams is raised by nearly 50% than that of pure PLA foams. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this article, organic-inorganic nanocomposite hybrids of styrene butadiene rubber were prepared with various nanofillers like modified and unmodified montmorillonite, sepiolite (SP), hectorite, carbon nanofiber (F), and expanded graphite.
Abstract: Organic–inorganic nanocomposite hybrids of styrene butadiene rubber were prepared with various nanofillers like modified and unmodified montmorillonite, sepiolite (SP), hectorite, carbon nanofiber (F), and expanded graphite. Comparison of the nanocomposites against the gum on the basis of mechanical properties illustrates that Cloisite15A (15A) produced an increment of 230% in the tensile strength (TS), at 8 phr loading. At 6 phr loading, F increased the modulus by 101%, while tear strength increased by 79%. Once optimized for loading, these nanocomposites were subjected to various compatibilization and dispersion techniques to achieve enhanced dispersion of the nanofillers. On modification, 15A registered 146% increase in modulus and 303% in TS, while F illustrated 150% increment in modulus and 113% in TS of the nanocomposite, over the gum control. Thorough dynamic mechanical and swelling studies were also performed. X-ray diffraction, atomic force microscopy and transmission electron microscopy were used to study the morphology. The London dispersive forces explained the enhanced properties on using carbon nanofiber, while the wider gallery gap and increased compatibility because of high organo-modifier content explicated the efficacy of 15A. Adsorption followed by shearing as well as intercalation of the rubber into clay layers were suggested as the probable mechanisms. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
TL;DR: In this article, a mechanistic scheme involving all the elementary steps of PE autooxidation plus one initiation and one termination step involving DOC has been elaborated, and the results of simulations have been compared with experimental results.
Abstract: Aging of unfilled polyethylene (PE) films in concentrated (80–100 ppm) chlorine dioxide (DOC) solutions at 20°C and 40 has been studied by IR spectrophotometry, melt rheometry, chlorine titration, and tensile testing to establish the mechanisms of PE degradation induced by DOC, to determine some important kinetic parameters, to identify the embrittlement mechanism, and to examine the possibility to predict nonempirically embrittlement from a kinetic model. Experimental results reveal that DOC initiates PE oxidation. This latter is responsible for hydroperoxide build-up, and chain scissions occur when hydroperoxides reach a critical concentration above which they decompose bimolecularly. The weight average molar mass Mw decreases and embrittlement occurs when Mw approaches a value of 70 kg mol−1 as previously found in thermooxidation studies. A mechanistic scheme involving all the elementary steps of PE autooxidation plus one initiation and one termination step involving DOC has been elaborated. The kinetic scheme derived from this mechanistic scheme has been solved numerically and the results of simulations have been compared with experimental results. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this paper, a novel oligomeric phosphorous-nitrogen containing intumescent flame retardant, poly (4,4-diamino diphenyl methane-O-bicycli pentaerythritol phosphate-phosphate) (PDBPP), was synthesized and characterized.
Abstract: A novel oligomeric phosphorous-nitrogen containing intumescent flame retardant, poly (4,4-diamino diphenyl methane-O-bicycli pentaerythritol phosphate-phosphate) (PDBPP), was synthesized and characterized. Thermal stability and flammability properties of polypropylene (PP)/PDBPP composites with various PDBPP loading were investigated by thermogravimetric analysis (TGA), limited oxygen index (LOI), and cone calorimeter, respectively. The results showed that the incorporation of PDBPP could improve both the thermal stability and flame retardancy of PP considerably. PP/30%PDBPP system had a LOI value of 28 and its peak heat release rate was reduced by 60% relative to pure PP. Infrared spectrum and field emission scanning electron microscope measurements revealed that PDBPP and PP/PDBPP composites would form a continuous multicellular char layer containing phosphoric acid when exposed to elevated temperature. It was suggested that the very char layer was responsible for the enhanced thermal stability and improved flame retardancy.
TL;DR: In this paper, the authors showed that the incorporation of MWNTs into the matrix resulted in higher complex viscosities (|η*|), storage modulus (G′), loss modulus, and lower loss factor (tanδ).
Abstract: Nylon 11 (PA11) nanocomposites with different loadings of multi-walled carbon nanotubes (MWNTs) were prepared by melt compounding. Scanning electron microscopy images on the fracture surfaces of the composites showed a uniform dispersion of MWNTs throughout the matrix. The presence of the MWNTs significantly improved the thermal stability and enhanced the storage modulus (G′) of the polymer matrix. Melt rheology studies showed that, compared with neat PA11, the incorporation of MWNT into the matrix resulted in higher complex viscosities (|η*|), storage modulus (G′), loss modulus (G″), and lower loss factor (tanδ). PA11 and its nanocomposites containing less than 1 wt% MWNTs showed similar frequency dependencies and reached a Newtonian plateau at low frequencies. For the nanocomposite with 2 wt% MWNTs, the regional network was destroyed and the orientation of the MWNTs during shearing exhibited a very strong shear thinning effect. The complex viscosities (|η*|) of the nanocomposites are larger than that of neat PA11 and decreased with increasing the temperature. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this article, the effects of PHF and PHFNW as filler on the structure and properties of the composite films were comparatively investigated by observation of morphology and analysis of thermal, optical, and mechanical properties.
Abstract: New applications of both pea hull fiber (PHF) and PHF-derived nanowhiskers (PHFNW), isolated from PHF by acid-hydrolysis, as fillers in starch-based biocomposite films were explored in this work. Two series of films were prepared by blending pea starch (PS), respectively, with PHF and PHFNW. The effects of PHF and PHFNW as filler on the structure and properties of the composite films were comparatively investigated by observation of morphology and analysis of thermal, optical, and mechanical properties. The results revealed that the PS/PHFNW nanocomposite films exhibited improved physical properties over both the neat PS film and PS/PHF microcomposite films. The light transmittance at 800 nm, tensile strength, elongation at break, and Young's modulus were 56.0%, 4.1 MPa (Megapascal), 30.1%, 40.3 MPa, respectively, for the PS film without filler; 58.0%, 7.6 MPa, 41.8%, and 415.2 MPa for the PS/PHFNW film containing 10 wt% filler; and 37.2%, 2.8 MPa, 17.0%, and 29.8 MPa for the PS/PHF film containing 10 wt% filler. The improvement to the properties of PS/PHFNW nanocomposite films may be attributed to the nanometer size effect of PHFNW, which resulted in the homogeneous dispersion of PHFNW within the PS, and the strong interactions between the matrix and the nanoscale filler. POLYM. ENG. SCI., 2009. Published by the Society of Plastics Engineers
TL;DR: Casado et al. as discussed by the authors presented the work of Casado and Martin at the Centro Cientifico Tecnologico Conicet -Mar del Plata.
Abstract: Fil: Casado, Ulises Martin. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingenieria. Instituto de Investigaciones en Ciencia y Tecnologia de Materiales; Argentina
TL;DR: In this article, the foaming behavior of high-melt strength polypropylene (HMS-PP) and HMS-PP/Cloisite 20A nanocomposites (PPNCs) was studied in a batch process.
Abstract: The foaming behavior of high-melt strength polypropylene (HMS-PP) and HMS-PP/Cloisite 20A nanocomposites (PPNC) was studied in a batch process. PPNCs with 2, 4, 8, and 10 wt% clay were prepared in a twin screw extruder. The morphology of the nanocomposites was studied using XRD and TEM. Subsequently, foaming experiments were conducted using supercritical CO2 as the blowing agent in a batch process, and foams with cell sizes varying from the sub micrometer to the micro meter range were prepared. The effect of variation in saturation pressure and temperature, foaming temperature, foaming time, and quench temperature was determined experimentally. Dynamic rheological measurements were conducted to relate the influence of nanocomposites morphology with foam cell growth and nucleation. Extensional rheological measurements were also conducted to detect the presence of strain hardening effect at the foaming temperatures used in the experiment. It was found that the nucleation efficiency of clay reduces with increase in clay loading. Also, the optimum amount of filler for generation of fine celled foams was found to be around the percolation threshold of the polymer. The extended strain hardening effect shown by the polymer in presence of clay plays an important role in stabilizing foam cell sizes.
TL;DR: In this article, the possibility of using the stems of milkweed plant as a source for natural cellulose fibers was explored in this research and the results showed that milkweed stem fibers have low % crystallinity when compared with cotton and linen but the strength of the fibers is similar to cotton and elongation is higher than that of linen fibers.
Abstract: Natural cellulose fibers with cellulose content, strength, and elongation higher than that of milkweed floss and between that of cotton and linen have been obtained from the stems of common milkweed plants. Although milkweed floss is a unique natural cellulose fiber with low density, the short length and low elongation make milkweed floss unsuitable as a textile fiber. The possibility of using the stems of milkweed plant as a source for natural cellulose fibers was explored in this research. Natural cellulose fibers extracted from milkweed stems have been characterized for their composition, structure, and properties. Fibers obtained from milkweed stems have about 75% cellulose, higher than the cellulose in milkweed floss but lower than that in cotton and linen. Milkweed stem fibers have low % crystallinity when compared with cotton and linen but the strength of the fibers is similar to cotton and elongation is higher than that of linen fibers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this paper, the conductivity and surface tension of solutions of sodium alginate and PEO were investigated by standard methods, including field emission scanning electron microscopy (FE-SEM), fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray (EDX), differential scanning calorimetry (DSC) and tensile testing.
Abstract: The electrospinning of sodium alginate, a natural biopolymer, was performed from aqueous solutions by blending with PEO, a biodegradable polymer. The conductivity and surface tension of solutions of sodium alginate and PEO were investigated by standard methods. The morphology, thermal, and mechanical properties of the electrospun nanofibers were studied using field emission scanning electron microscopy (FE-SEM), fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray (EDX), differential scanning calorimetry (DSC) and tensile testing. Uniform, smooth, and ultra-fine nanofibers with diameters of ∼140-190 nm were obtained with solution concentrations of 6-7.2% and sodium alginate/PEO volume ratios of 30:70-50:50. The mechanical strength of the electrospun sodium alginate/PEO mats with good morphology was 21 MPa compared to PEO mats which had a strength of only 10 MPa.
TL;DR: In this paper, the failure of polyethylene pipes transporting chlorine dioxide (DOC) disinfected water under pressures of few bars was investigated and a kinetic model was elaborated to predict the time to failure, based on a chemical unit which models the radical processes induced by DOC, and a mechanical unit based on an empirical creep law and a failure criterion depending of the molar mass calculated by the chemical unit.
Abstract: This article deals with the failure of polyethylene pipes transporting chlorine dioxide (DOC) disinfected water under pressures of few bars. Accelerated aging tries made at 20 or 40°C show that the antioxidant is rapidly consumed in a superficial layer until a depth of about 1.2 mm. Carbonyl groups appear in a sharper layer of few hundreds micrometers. Natural aging results at various places, for various times up to about 30 years, reveal also a superficial attack with a depth of the order of 1.2 mm. An antioxidant loss by migration, in the whole sample thickness, is also observable. The shape of antioxidant concentration profiles indicates that the crossing of interfaces controls partially the whole migration kinetics. Failures, with brittle cracking, were observed in natural aging, after exposure times of the order of 5–15 years, i.e., far before the expected lifetime (50 years). A kinetic model has been elaborated to predict the time to failure. It is based on a chemical unit, which models the radical processes induced by DOC, and a mechanical unit based on an empirical creep law and a failure criterion depending of the molar mass calculated by the chemical unit. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this article, the deformation characteristics of PEIT and other polyesters have been evaluated to define stretching parameters and necessary composition for making oriented bottles for hot fill applications, and a methodology to achieve molecular orientation comparable with films and articles made by conventional processing of poly(ethylene terephthalate), PET.
Abstract: Polyethylene terephthalate containing Isosorbide (PEIT) polymers made from renewable corn-derived Isosorbide monomer exhibit a wide range of glass transition temperatures (80–180°C) and are therefore able to be used in many applications. Stress–strain curves for high Isosorbide content copolymers show strain softening, which impairs the molecular orientation during orientation of films and bottles. It is therefore necessary to find ways to modify deformation behavior of PEIT copolymers. Deformation characteristics of PEIT and other polyesters have been evaluated to define stretching parameters and necessary composition for making oriented bottles for hot fill applications. In the presence of polymeric nucleating agents, (polymeric ionomers or polyesters containing sodium ions), strain-hardening parameters become almost temperature- independent below solid state deformation temperature of 125°C. We developed a methodology to achieve molecular orientation comparable with films and articles made by conventional processing of poly(ethylene terephthalate), PET. Polyesters containing sodium ions are efficient nucleating agents for PEIT, and their required concentration is dependent on deformation temperature. Both strain hardening and stress at 250% strain depend on the concentration of nucleating agents and deformation temperatures. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this article, the effect of prolonged exposure to heat and shear stresses on ABS structural and performance properties was investigated by attenuated total reflectance Fourier transform infrared spectroscopy, the thermal response was recorded on differential scanning calorimetry thermographs, whereas the thermal stability of reprocessed samples was detected with thermogravimetric analysis.
Abstract: In this work, poly(acrylonitrile-butadiene-styrene) (ABS) was subjected to five subsequent extrusion cycles and the effect of prolonged exposure to heat and shear stresses on its structural and performance properties was investigated. More specifically, the resulting chemical changes were studied by attenuated total reflectance Fourier transform infrared spectroscopy, the thermal response was recorded on differential scanning calorimetry thermographs, whereas the thermal stability of reprocessed samples was detected with thermogravimetric analysis. Also, the rheological properties of the aforementioned compounds were investigated via melt flow index tests, to assess their processability during melt mixing and molding processes. Furthermore, the mechanical properties of the obtained composites were investigated and the observed interactions were interpreted in terms of the influence of each component on the functional properties of the final mixture. This attempt might be a contribution to recycling of ABS by means of techniques that include multiple reprocessing. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this article, a coupling between the Nelder-Mead optimization algorithm and finite element (FE) simulations of the forming process developed using ABAQUS 1.F E simulations were validated using in situ tests and measurements performed on 18.5 g-50 cl polyethylene terephthalate bottles.
Abstract: This study presents an optimization strategy developed for the stretch-blow molding process. The method is based on a coupling between the Nelder-Mead optimization algorithm and finite element (FE) simulations of the forming process developed using ABAQUS 1 .F E simulations were validated using in situ tests and measurements performed on 18.5 g—50 cl polyethylene terephthalate bottles. To achieve that, the boundary conditions were carefully measured for both the infrared heating and the blowing stages. The temperature distribution of the perform was predicted using a 3D finite-volume software, and then applied as an initial condition into FE simulations. In addition, a thermodynamic model was used to predict the air pressure applied inside the preform, taking into account the relationship between the internal air pressure and the enclosed volume of the preform, i.e., the fluid-structure interaction. It was shown that the model adequately predicts both the blowing kinematics and the thickness distributions of the bottle. In the second step, this model was combined to an optimization loop to automatically compute the best preform temperature distribution, providing a uniform thickness for the bottle. POLYM. ENG. SCI., 49:783–793, 2009. a 2008 Society of Plastics Engineers
TL;DR: In this article, the formation of chitosan chains is influenced by the addition of solvent and cross-linking agent, and it was shown that the ability of the chitin to chelate metals directly relates to the chemical stability of non-woven mat.
Abstract: Electrospinning is a complex process that requires numerous interacting physical instabilities. Assuming that a chosen polymer and solvent system can be spun, the chosen polymer exists in various states, which have variable crystallinities starting with the highest degree of crystallinity (when in bulk form) and ultimately being transformed into a non-woven mat. In an effort to better understand the effects that the electrospinning process has on the biopolymers chitin [practical grade (PG)] and chitosan [PG and medium molecular weight (MMW)], including post-production neutralization and cross-linking steps, field emission scanning electron microscopy (FESEM) and solubility studies were performed. An evaluation of diffraction peaks of the bulk, solution, and fibrous forms of chitin and chitosan were evaluated by X-ray diffraction (XRD) and determined that the formation of chitosan chains is influenced by the addition of solvent and cross-linking agent. This study is of importance since the crystallinity of chitin and chitosan directly relate to the ability of the biopolymers to chelate metals, and the chemical stability of non-woven mats aid in the creation of functional filtration membranes. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this article, a method for incorporating barium titanate (BT) nanoparticles into polymethylmethacrylate (PMMA) is proposed to prepare composite films with a high dielectric constant and high transparency.
Abstract: A method for incorporating barium titanate (BT) nanoparticles into polymethylmethacrylate (PMMA) is proposed to prepare composite films with a high dielectric constant and high transparency. BT particles with particle sizes of 7.8–24.0 nm and crystal sizes of 8.60–17.7 nm were synthesized with a complex alkoxide method. Surface of the BT particles was modified with 3-methacryloxypropyltrimethoxysilane to introduce double bonds that was grafted with PMMA. The PMMA-grafted BT particles were suspended in PMMA/N-methyl-2-pyrrodinone solution and spin-coated onto glass substrates to prepare the PMMA/BT composite films. The surface modification gave composite films having smooth surfaces and high transparency. An increase in BT particle size and BT volume fraction in the film tended to increase the dielectric constant while keeping the dissipation factor around 5%. The dielectric constant of the film prepared for a particle size of 24.0 nm at 39 vol% attained a value of 19.8 that was around four times higher than that of the pure PMMA film. The dielectric constants of the BT particles estimated by the application of Lichtenecker's mixing model to the composite films were 75.3, 105.1, and 166.3 for particle sizes of 7.8, 11.0, and 24.0 nm, respectively. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
TL;DR: In this paper, the optical properties of MPDMAPP composite films were studied using UV-visible, refractive, and steady state fluorescence microscopy techniques, and the fluorescence microscopic image showed that the composite films are photochromatic in nature.
Abstract: Polymer blends along with 1-(4-methylphenyl)-3-(4-N,N,
dimethyl amino phenyl)-2-propen-1-one (MPDMAPP)
NLO-chromophore-doped composite films were prepared
by solvent casting method using DMF. The optical
properties were studied using UV–visible, refractive
index, steady state fluorescence, and fluorescence microscopic imaging techniques. The UV–vis absorption
spectra showed three absorption bands and were assigned to localized n?p*, n?p* inter band, and p?p* transition of charge transfer groups. The observed changes in the absorption peak, edges, and intensity with dopant concentration are understood based on charge transfer complex (CTC) formation. The refractive indices of the composite films varied from 1.4937–1.5398 for red and 1.5165–1.5516 for green light respectively. The steady state fluorescence data showed both emission peak wavelengths and intensity changes with MPDMAPP doping level in blend. The fluorescence anisotropy (r) variations in the composite films indicate the suppressed molecular motion of
MPDMAPP in the solid composite film. The fluorescence microscopic image of these composite films showed that the films are photochromatic in nature. These modified properties are thought to be due to the charge transfer upon excitation from the donor to the acceptor connected through benzene ring and CTC formation. POLYM. ENG. SCI., 49:903–909, 2009. a2009 Society of Plastics Engineers