Showing papers in "Polymers for Advanced Technologies in 2008"
TL;DR: This work has built upon pioneering work in this field as well as in responsive IPN systems to develop an IPN system based on end-linked poly-(ethylene glycol) (PEG) and loosely crosslinked poly(acrylic acid) with hydrogen bond-reinforced strain-hardening behavior in water and high initial Young's moduli under physiologic buffer conditions through osmotically induced pre-stress.
Abstract: Interpenetrating polymer networks (IPNs) have been the subject of extensive study since their advent in the 1960s Hydrogel IPN systems have garnered significant attention in the last two decades due to their usefulness in biomedical applications Of particular interest are the mechanical enhancements observed in "double network" IPN systems which exhibit nonlinear increases in fracture properties despite being composed of otherwise weak polymers We have built upon pioneering work in this field as well as in responsive IPN systems to develop an IPN system based on end-linked poly-(ethylene glycol) (PEG) and loosely crosslinked poly(acrylic acid) (PAA) with hydrogen bond-reinforced strain-hardening behavior in water and high initial Young's moduli under physiologic buffer conditions through osmotically induced pre-stress Uniaxial tensile tests and equilibrium swelling measurements were used to study PEG/PAA IPN hydrogels having second networks prepared with varying crosslinking and photoinitiator content, pH, solids content, and comonomers Studies involving the addition of non-ionic comonomers and neutralization of the second network showed that template polymerization appears to be important in the formation of mechanically enhanced IPNs
341 citations
TL;DR: In this article, the efficiency of different intumescent formulations to flame retard polylactic acid (PLA) was evaluated by limiting oxygen index (LOI), UL-94, and cone calorimetry.
Abstract: The aim of this study is to evaluate the efficiency of different intumescent formulations to flame retard polylactic acid (PLA). First, the ammonium polyphosphate (APP)/pentaerythritol (PER) system is chosen because it previously demonstrated a good behavior for polyethylenic matrices. The PER is then substituted by bioresources such as lignin and starch. The flame retardant properties of the various formulations are evaluated by limiting oxygen index (LOI), UL-94, and cone calorimetry. Compared to the PLA/APP/PER composite, the materials containing lignin and starch show lower LOI values but still commercially acceptable (superior to 32%). In contrast, the UL ratings obtained for these formulations are superior to that containing PER (V0 against V2 rating).
The cone calorimeter analysis confirms the formation of an intumescent structure for the “green” composites, with a final residue corresponding to 50% of the initial sample mass and also a decrease in the peak of heat release of 50%. Finally, the composition of the formulation is optimized following a mixture design methodology to maximize the quantity of bioresources. A 32% LOI value is obtained for a composite containing 60% PLA, 12% APP, and 28% starch. Copyright © 2008 John Wiley & Sons, Ltd.
297 citations
TL;DR: In this paper, the technology of nano-and micro-scale particle reinforcement concerning various polymeric fiber-reinforced systems including polyamides (PAs), polyesters, polyurethanes (PUs), polypropylenes (pps), and high-performance/temperature engineering polymers such as polyimide (PI), poly(ether ether ketone) (PEEK), polyarylacetylene (PAA), and poly p-phenylene benzobisoxazole (PBO) is reviewed.
Abstract: In this work, the technology of nano- and micro-scale particle reinforcement concerning various polymeric fiber-reinforced systems including polyamides (PAs), polyesters, polyurethanes (PUs), polypropylenes (pps), and high-performance/temperature engineering polymers such as polyimide (PI), poly(ether ether ketone) (PEEK), polyarylacetylene (PAA), and poly p-phenylene benzobisoxazole (PBO) is reviewed. When the diameters of polymer fiber materials are shrunk from micrometers to submicrons or nanometers, there appear several unique characteristics such as very large surface area to volume ratio (this ratio for a nanofiber can be as large as 103 times of that of a microfiber), flexibility in surface functionalities and superior mechanical performance (such as stiffness and tensile strength) compared to any other known form of the material. While nanoparticle reinforcement of fiber-reinforced composites has been shown to be a possibility, much work remains to be performed in order to understand how nanoreinforcement results in dramatic changes in material properties. The understanding of these phenomena will facilitate their extension to the reinforcement of more complicated anisotropic structures and advanced polymeric composite systems. Copyright © 2008 John Wiley & Sons, Ltd.
281 citations
TL;DR: In this paper, fire performance data for several types of composites reinforced by lignocellulosic fibers is presented. But, little information is available on their fire performance.
Abstract: Natural fiber-reinforced composites are more and more frequently applied to building industry and transportation. Therefore, the knowledge of their behavior during fire is of high importance. Flammability is one of very important parameters that often limits the application of composites to a given area. It is well-known that addition of lignocellulosic fibers to polymer changes mechanical properties of the product obtained. However, little information is available on their fire performance. The purpose of this review was to obtain fire performance data for several types of composites reinforced by lignocellulosic fibers. Copyright © 2008 John Wiley & Sons, Ltd.
269 citations
TL;DR: In this article, a poly(RTIL)-based composite gas separation membrane was proposed for room-temperature ionic liquids (RTILs) to provide a stable composite material with a CO2 permeability increase of ∼400% with a 33% improvement to CO2/N2 selectivity relative to the analogous poly( RTIL) membrane lacking any free ion pairs.
Abstract: Room-temperature ionic liquids (RTILs) present a number of unique opportunities for the processing and tailoring of polymer materials for applications including ion conduction polymers, catalysis, and gas separations. Perhaps most importantly, RTILs can be synthesized as monomers and polymerized in the presence of non-polymerizable RTILs to provide solid composites with enhanced properties. These features allow for the formation of poly(RTIL)–RTIL composite gas separation membranes, exhibiting hybrid properties of both RTILs and polymers. Incorporation of just 20 mol% free RTIL in the polymer membrane yields a stable composite material with a CO2 permeability increase of ∼400% with a 33% improvement to CO2/N2 selectivity relative to the analogous poly(RTIL) membrane lacking any free ion pairs. The composite membrane also showed a significant improvement in CO2/CH4 separation compared to other poly(RTILs) when analyzed via “Robeson Plots.” This new approach to polymer gas separation membranes provides a powerful method to improve the performance of current materials without intensive organic synthesis. Copyright © 2008 John Wiley & Sons, Ltd.
237 citations
TL;DR: In this article, a novel type hydrogel-clay nanocomposites based on the acrylamide (AAm)- 2-acrylamido- 2-methylpropane sulfonic acid (AMPS) sodium salt and clay were synthesized via in situ copolymerization in aqueous solution.
Abstract: Novel type hydrogel-clay nanocomposites based on the acrylamide (AAm)- 2-acrylamido- 2-methylpropane sulfonic acid (AMPS) sodium salt and clay were synthesized via in situ copolymerization in aqueous solution. Samples were characterized by determining total basic group (TGB) content and swelling degree, XRD analysis, and FTIR spectroscopy. Effects of monomer ratio and clay amount on the swelling properties of the samples were investigated. It was found that the hydrogel/clay nanocomposites exhibited improved swelling capacity compared with the hydrogels. Samples were used to remove heavy metal ions (Cu (II), Cd (II), and Pb (II)) from aqueous solution in competitive and non-competitive conditions for the first time. The effects of time and pH of the initial metal ion solution on the adsorption capacity were investigated and selectivity properties of the samples were evaluated. It was found that incorporation of a low amount of clay (10% (wt)) into the polymer structure increased the heavy metal ion adsorption capacity of the sample. It was concluded that the AAm-AMPS/clay nanocomposites could be used as novel type, fast-responsive, and high capacity sorbent materials in heavy metal removing processes. Copyright © 2007 John Wiley & Sons, Ltd.
206 citations
TL;DR: In this paper, the AAm-AMPSNa/clay hydrogel nanocomposite exhibits improved swelling capacity compared with the traditional AMPSNa hydrogels, and the diffusion mechanisms show non-Fickian character.
Abstract: Acrylamide (AAm)-2-acrylamide-2-methylpropanesulfonic acid sodium salt (AMPSNa) hydrogel and AAm-AMPSNa/clay hydrogel nanocomposite having 10 w% clay was prepared by in situ copolymerization in aqueous solution in the presence of a crosslinking agent (N,N′-methylenebisacrylamide (NMBA)). Swelling properties and kinetics of the hydrogel samples were investigated in water and aqueous solutions of the Safranine-T (ST) and Brilliant Cresyl Blue (BCB) dyes. The swelling and diffusion parameters were also calculated in water and dye solutions. It was observed that the AAm-AMPSNa/clay hydrogel nanocomposite exhibits improved swelling capacity compared with the AAm-AMPSNa hydrogel. It was also found that the diffusion mechanisms show non-Fickian character. Adsorption properties of the hydrogel samples in the aqueous solution of ST and BCB dyes were also investigated. Clay incorporation into the hydrogel structure increased not only the adsorption capacity but also the adsorption rate. Adsorption capacity values of the hydrogel nanocomposite were found to be 484.2 and 494.2 mg g−1 for the ST and BCB dyes, respectively. It was seen that the adsorption of dyes by the hydrogel nanocomposite completed in 10 min while the AAm-AMPSNa hydrogel adsorbed dyes approximately in 90 min. Adsorption data of the samples were modelled by the pseudo-first-order and pseudo-second-order kinetic equations in order to investigate dye adsorption mechanism. It was found that the adsorption kinetics of hydrogel nanocomposite followed a pseudo-second-order model. Equilibrium isotherms were analyzed using the Langmuir and Freundlich isotherms. It was seen that the Langmuir model fits the adsorption data better than the Freundlich model. Copyright © 2008 John Wiley & Sons, Ltd.
191 citations
TL;DR: In this article, the synergistic effect between a char forming agent (CFA) and microencapsulated ammonium polyphosphate (MAPP) on the thermal and flame retardancy of polypropylene (PP) is investigated by limiting oxygen index (LOI), UL-94 test, cone calorimetry, thermogravimetric analysis (TGA), scanning electron micrograph (SEM), and water resistance test.
Abstract: The synergistic effect between a char forming agent (CFA) and microencapsulated ammonium polyphosphate (MAPP) on the thermal and flame retardancy of polypropylene (PP) are investigated by limiting oxygen index (LOI), UL-94 test, cone calorimetry, thermogravimetric analysis (TGA), scanning electron micrograph (SEM), and water resistance test. The results of cone calorimetry show that heat release rate peak (PHRR), total heat release (THR), and the mass loss of PP with 30 wt% intumescent flame retardant (IFR, CFA/MAPP = 1:2) decreases remarkably compared with that of pure PP. The HRR, THR, and mass loss decrease, respectively from 1140 to 100 kW/m2, from 96 to 16.8 MJ/m2, and from 100 to 40%. The PP composite with CFA/MAPP = 1:2 has the best water resistance, and it can still obtain a UL-94 V-0 rating after 168 hr soaking in water. Copyright © 2008 John Wiley & Sons, Ltd.
189 citations
TL;DR: In this article, the pyrolysis and fire behavior of glass-fiber reinforced poly(butylene terephthalate) (PBT/GF) with two different metal phosphinates as flame retardants in combination with and without melamine cyanurate (MC) were analyzed by means of thermogravimetry, thermograimetry coupled with infrared spectroscopy, flammability, and cone calorimeter tests as well as scanning electron microscopy/energy dispersive X-ray spectrographs.
Abstract: The pyrolysis and fire behavior of glass-fiber reinforced poly(butylene terephthalate) (PBT/GF) with two different metal phosphinates as flame retardants in combination with and without melamine cyanurate (MC) were analyzed by means of thermogravimetry, thermogravimetry coupled with infrared spectroscopy, flammability, and cone calorimeter tests as well as scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray fluorescence spectroscopy. In PBT/GF, dosages of 13–20% of the halogen-free flame retardant aluminum phosphinate or aluminum phosphinate in combination with MC fulfill the requirements for electrical engineering and electronics applications (UL 94 = V-0; LOI > 42%), whereas the use of the same amount of zinc phosphinate or zinc phosphinate in combination with MC does not improve the fire behavior satisfactorily (UL 94 = HB; LOI = 27–28%). The performance under forced flaming conditions (cone calorimeter) is quite similar for both of the metal phosphinates. The use of aluminum and zinc salts results in similar flame inhibition predominantly due to the release of the phosphinate compounds in the gas phase. Both metal phosphinates and MC interact with the polymer changing the decomposition characteristics. However, part of the zinc phosphinate vaporizes as a complete molecule. Because of the different decomposition behavior of the metal salts, only the aluminum phosphinate results in a small amount of thermally stable carbonaceous char. In particular, the aluminum phosphinate-terephthalate formed is more stable than the zinc phosphinate-terephthalate. The small amount of char has a crucial effect on the thermal properties and mechanical stability of the residue and thus the flammability. Copyright © 2008 John Wiley & Sons, Ltd.
169 citations
TL;DR: In this article, the possibility of using a corona treatment for fiber surface activation, which can facilitate the loading of silver nanoparticles (NPs) from colloids onto the polyester and polyamide fabrics and thus improve their antibacterial properties, was studied.
Abstract: The possibility of using a corona treatment (electrical discharge at atmospheric pressure) for fiber surface activation, which can facilitate the loading of silver nanoparticles (NPs) from colloids onto the polyester (PES) and polyamide (PA) fabrics and thus improve their antibacterial properties, was studied. Bactericidal efficiency and its laundering durability on silver-loaded fabrics for Grampositive bacterium Staphylococcus aureus and Gram-negative bacterium Escherichia coli were evaluated. The fiber morphology after corona treatment and subsequent loading of silver NPs was followed by SEM. Corona-treated fabrics loaded with silver NPs exhibited better antibacterial properties in comparison with untreated fabrics. In order to obtain acceptable laundering durability, it is necessary to use highly concentrated silver colloids. Copyright # 2008 John Wiley & Sons, Ltd.
159 citations
TL;DR: In this paper, a specific PLA grade (L/D isomer ratio of 96:4, high molecular weight) was melt-mixed with selected plasticizers: bis(2-ethylhexyl) adipate (DOA), glyceryl triacetate (GTA), and tributyl O-acetylcitrate (TBAC).
Abstract: Polylactide (PLA) is an attractive candidate for replacing petrochemical polymers because it is biodegradable and produced from annually renewable resources. Characterized by high tensile strength, unfortunately the brittleness and rigidity of PLA limit its applicability. For a great number of applications such as packaging,fibers,films, etc., it is of high interest to formulate new grades with improved flexibility and better impact properties. In this objective, a specific PLA grade (L/D isomer ratio of 96:4, high molecular weight) was melt-mixed with selected plasticizers: bis(2-ethylhexyl) adipate (DOA), glyceryl triacetate (GTA), and tributyl O-acetylcitrate (TBAC). Their effect on the molecular, thermal, and mechanical properties of PLA was investigated for content up to 20wt% plasticizer and the results were correlated with a particular attention to the relationship between property and application. Using the solubility and interaction parameters, a tentative evaluation of the product that could act as the most effective plasticizer for PLA has been performed and the obtained results have been corroborated with the materials physical properties. Excellent mechanical performances were obtained using the plasticizer having the lowest molecular mass (GTA) and the best interaction parameter. In relation to plasticizer amount/nature, the glass transition temperature of PLA (62-C) is decreased by plasticizing by more than 30-C, whereas better impact properties and lower stiffness are measured. The optimal formulations targeted to the final applications are clearly characterized by specific end-use properties: improved crystallization rates (PLA-DOA); high elongation at break and tensile strength (PLA-GTA, PLA-TBAC), medium to high impact properties (PLA-DOA, PLA-GTA) compositions. Copyright # 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, the preparation of poly (3,4-ethylenedioxythiophene) (PEDOT) ferrimagnetic conducting polymer composite by incorporation of ferrite particles in the polymer matrix by emulsion polymerization was reported.
Abstract: The present paper reports the preparation of poly (3,4-ethylenedioxythiophene) (PEDOT) ferrimagnetic conducting polymer composite by incorporation of ferrite particles in the polymer matrix by emulsion polymerization. Synthesis of PEDOT–γ-Fe2O3 composite was carried out by chemical oxidative polymerization of EDOT with ferrite particles in the presence of dodecylbenzenesulfonic acid (DBSA) that works as dopant as well as surfactant in aqueous medium. The resulting conducting composite possesses saturation magnetization (Ms) value of 20.56 emu/g with a conductivity of 0.4 Scm−1, which was determined by VSM and four probe technique, respectively. B-H curve reveals that ferrimagnetic particles of γ-Fe2O3 show super-paramagnetic behavior at room temperature which was also observed in PEDOT–γ-Fe2O3 composite. The resulting conducting ferrimagnetic composite shows microwave absorption loss of 18.7–22.8 dB in the frequency range of 12.4–18 GHz. Thermogravimetric analysis of the composite revealed that the composite is thermally stable up to 230°C. The characterization of the PEDOT–γ-Fe2O3 composite was carried out using XRD and FTIR spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.
TL;DR: In this article, a microencapsulated ammonium polyphosphate (APP) with urea-melamine-formaldehyde (UMF) resin is prepared by in situ polymerization, and is characterized by FTIR and XPS.
Abstract: Microencapsulated ammonium polyphosphate (MCU-APP) with urea–melamine–formaldehyde (UMF) resin is prepared by in situ polymerization, and is characterized by FTIR and XPS. The microencapsulation of APP with the UMF resin leads to a decrease in the particle's water solubility. The flame retardant actions of MCU-APP and APP in PP are studied using limiting oxygen index (LOI) and UL-94 test, and their thermal stability is evaluated by thermogravimetric analysis. It is found that the LOI value of the PP/MCU-APP composite is higher than the value of the PP/APP composite. In comparison with the PP/MCU-APP composites, the LOI values of the PP/MCU-APP/DPER ternary composites at the same additive loading increase, and UL-94 ratings of most ternary composites are raised to V-0. The water-resistant properties of the PP composites containing APP and MCU-APP are studied. Moreover, the combustion behavior of the PP composites is investigated by the cone calorimeter. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: Using diethylene glycol (DegOH) as non-solvent additive (NSA) and N, N-dimethylacetamide (DMAc) as solvent (S), polyethersulfone (PES) flat sheet membranes were prepared via immersion precipitation combined with the vapor induced phase separation (VIPS) process.
Abstract: Using diethylene glycol (DegOH) as non-solvent additive (NSA) and N, N-dimethylacetamide (DMAc) as solvent (S), polyethersulfone (PES) flat sheet membranes were prepared via immersion precipitation combined with the vapor induced phase separation (VIPS) process. Light transmittance was used to follow the precipitation rate during the immersion process as well as during the VIPS stage. As the addition of the NSA, the viscosity of casting solutions increased, which led to a slow precipitation rate. Though the precipitation rate decreased, the instantaneous demixing type was maintained. High flux membranes were obtained only at a high mass ratio of NSA/S; producing membranes had cellular pores on the top surface and sponge-like structure on cross section. The VIPS process prior to immersion precipitation was important for the formation of cellular pore on the surface. With the increase in exposure time, the liquid–liquid phase separation took place on the surface of casting solution; nucleation and growth induced the formation of cellular pore on the top surface. Coagulation bath temperature also had large effect on the precipitation rate; high temperature on coagulation bath mainly accelerated the transfer of solvent and non-solvent. Higher flux membrane with a porous skin layer could be obtained at a high coagulation bath temperature, but at the same time the mechanism properties were weakened. Copyright © 2007 John Wiley & Sons, Ltd.
TL;DR: In this article, the thermal and fire-retardant properties of DICY-cured DEN 438 epoxy samples containing the novel DOPO-based additives were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the UL 94 test.
Abstract: Novel derivatives of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were obtained by a simple synthetic route and incorporated in epoxy resins, consisting of epoxy novolac (DEN 438), dicyandiamide (DICY), and fenuron. The thermal and fire-retardant properties of DICY-cured DEN 438 epoxy samples containing the novel DOPO-based additives were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the UL 94 test. The obtained results were compared to those of specimens containing commercially available phosphates as flame-retardants. UL 94 tests showed that nitrogen-containing substituents at the phosphorus atom increase the fire-retardant efficiency of DOPO-based additives. Two nitrogen-substituted DOPO derivatives 4,4′-Diaminodiphenylmethane (DDM)-(DOP)2 and DDM-(DOP)2-S were found to be very powerful fire-retardants in DICY-cured DEN 438 epoxy resins. The V0 rating was achieved at approximately 1% phosphorus in the resin and the glass transition temperature (Tg) was maintained at the high level of the pure DEN 438/DICY epoxy material (Tg = 180–185°C). These novel DOPO derivatives are the first non-reactive additives having no influence on the Tg of the epoxy material. They not only surpass the capabilities of the other additives used in this work, but also those of all commercially available flame-retardants for epoxy resins. Therefore, DDM-(DOP)2 and DDM-(DOP)2-S are expected to be qualified for high-Tg resins commonly used in printed wiring boards (PWB) for high-performance applications. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, a carbon nanotube (CNT)-reinforced rubber composites was attempted to achieve dramatic improvements in the performance of rubber materials, in order to achieve a significant increase in the storage modulus and dynamic compression properties.
Abstract: In order to achieve dramatic improvements in the performance of rubber materials, the development of carbon nanotube (CNT)-reinforced rubber composites was attempted. The CNT/natural rubber (NR) nanocomposite was prepared through solvent mixing on the basis of pretreatment of CNTs. Thermal properties, vulcanization characteristics, and physical and mechanical properties of the CNT/NR nanocomposites were characterized in contrast to the carbon black (CB)/NR composite. Through the addition of the CNTs treated using acid bath followed by ball milling with HRH (hydrated silica, resorcinol, and hexamethylene tetramine) bonding systems, the crystallization melting peak in differential scanning calorimetry (DSC) curves of NR weakened and the curing rate of NR slightly decreased. Meanwhile, the over-curing reversion of CNT/NR nanocomposites was alleviated. The dispersion of the treated CNTs in the rubber matrix and interfacial bonding between them were rather good. The mechanical properties of the CNT-reinforced NR showed a considerable increase compared to the neat NR and traditional CB/NR composite. At the same time, the CNT/NR nanocomposites exhibited better rebound resilience and dynamic compression properties. The storage modulus of the CNT/NR nanocomposites greatly exceeds that of neat NR and CB/NR composites under all temperature regions. The thermal stability of NR was also obviously improved with the addition of the treated CNTs. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: Zinc borates function as flame retardant, smoke suppressant, afterglow suppressant and anti-tracking agent in both halogen-containing and halogen free polymers as discussed by the authors.
Abstract: Zinc borates function as flame retardant, smoke suppressant, afterglow suppressant, and anti-tracking agent in both halogen-containing and halogen-free polymers. This paper will review 35 years of historical development and recent advances in the use of these multifunctional fire retardants in electrical/electronic, transportation, and building product applications. In addition, the use of zinc borates as polymer additives for non-flame retardant applications will also be briefly reviewed. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, the effect of nanoparticles, i.e., clays and carbon nanofibers (CNFs), on the HRR was investigated with special attention given to melt dripping.
Abstract: Untreated polyurethane flexible foams (PUFs) are prone to rapid fire growth due to their low density and low thermal conductivity. Furthermore, the low viscosity of the decomposition products generates severe dripping that increases the fire hazard related to the combustion of PUFs. In fact, this downwardflow offlaming liquid often results in a pool-fire that promotesflame propagation and boosts the rate of heat release (HRR) due to a significant increase in the burning area and to feed-back between the flame on the pool-fire and the residual foam. In this work the effect of nanoparticles, i.e., clays and carbon nanofibers (CNFs), on the HRR is investigated with special attention given to melt dripping. A modified cone calorimeter test has been developed for this purpose. It is shown that CNFs form an entangled fiber network which eliminates melt dripping and decreases the HRR. Published in 2008 by John Wiley & Sons, Ltd.
TL;DR: In this paper, a new hyperbranched poly(trimellitic anhydride-triethylene glycol ester epoxy (HTTE) is synthesized and used to toughen diglycidyl ether of bisphenol A (DGEBA) 4,4′-diaminodiphenylmethane (DDM) resin system.
Abstract: New hyperbranched poly(trimellitic anhydride-triethylene glycol) ester epoxy (HTTE) is synthesized and used to toughen diglycidyl ether of bisphenol A (DGEBA) 4,4′-diaminodiphenylmethane (DDM) resin system. The effects of content and generation number of HTTE on the performance of the cured systems are studied in detail. The impact strength is improved 2–7 times for HTTE/DGEBA blends compared with that of the unmodified system. Scanning electron microscopy (SEM) of fracture surface shows cavitations at center and fibrous yielding phenomenon at edge which indicated that the particle cavitations, shear yield deformation, and in situ toughness mechanism are the main toughening mechanisms. The dynamic mechanical thermal analyzer (DMA) analyses suggest that phase separation occurred as interpenetrating polymer networks (IPNs) for the HTTE/DGEBA amine systems. The IPN maintains transparency and shows higher modulus than the neat epoxy. The glass transition temperature (Tg) decreases to some extent compared with the neat epoxy. The Tg increases with increase in the generation number from first to third of HTTE and the concentrations of hard segment. The HTTE leads to a small decrease in thermal stability with the increasing content from TGA analysis. The thermal stability increases with increase in the generation number from first to third. Moreover, HTTE promotes char formation in the HTTE/DGEBA blends. The increase in thermal properties from first to third generation number is attributed to the increase in the molar mass and intramolecular hydrogen bridges, the increasing interaction of the HTTE/DGEBA IPNs, and the increasing crosslinking density due to the availability of a greater number of end hydroxyl and end epoxide functions. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this paper, a shell of PVA-melamine-formaldehyde resin, microencapsulated ammonium polyphosphate (VMFAPP) is prepared by in situ polymerization and characterized by FTIR and XPS.
Abstract: With a shell of PVA–melamine–formaldehyde resin, microencapsulated ammonium polyphosphate (VMFAPP) is prepared by in situ polymerization and characterized by FTIR and XPS. Microencapsulation gives VMFAPP better water resistance and flame retardance compared with APP in PP. Thermal stability and fire resistance behavior have been analyzed and compared. The LOI value of the PP/VMFAPP composite is higher than that of the PP/APP composite. The UL 94 ratings of most of the PP/VMFAPP composites are V-0, whereas PP/APP gives no rating at the 30% additive level. The water resistant properties of the PP composites are studied. Results of the cone calorimeter experiment show that VMFAPP is an effective flame retardant in PP compared with APP. The thermal degradation behaviors of APP and VMFAPP have been studied using TG and dynamic FTIR. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this paper, the nanofibers have been characterized by scanning electron microscopy (SEM), confirming the presence of bead free and fiber-bead free morphologies.
Abstract: Poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC), Nylon 6, and Nylon 6,6 have been electrospun successfully. The nanofibers have been characterized by scanning electron microscopy (SEM), confirming the presence of bead free and fiber-bead free morphologies. Thermogravimetric analysis (TGA) indicated differences between the thermal stability of PMMA nanofibers and PMMA powder. However, no significant differences were observed between the starting physical form (powder or pellet) of PVC, Nylon 6 and Nylon 6,6, and their corresponding electrospun nanofibers. Differential scanning calorimetry (DSC) demonstrated a lower glass transition temperature (Tg) and water absorption for PMMA electrospun nanofibers. Furthermore, electrospun Nylon 6 and Nylon 6,6 had a slight decrease in crystallinity. Tensile testing was performed on the electrospun nanofibers to obtain the Young modulus, peak stress, strain at break, and energy to break, revealing that the non-woven mats obtained had modest mechanical properties that need to be enhanced. Copyright © 2007 John Wiley & Sons, Ltd.
TL;DR: In this article, a flame-retarded polypropylene (PP)-polyethylene (PP-MTP) was analyzed by using LOI, UL-94 test, cone calorimetry, and TGA.
Abstract: Melamine salt of tripentaerythriol phosphate (MTP), as a new intumescent flame-retardant, was prepared from tripentaerythritol (TPE), polyphosphoric acid, phosphoric pentoxide, and melamine, and then incorporated into polypropylene (PP) to obtain flame-retarded PP-MTP. FT-IR analysis showed that MTP was in the form of cage structure. The flammability, combustion behavior, and thermal degradation and stability of flame-retarded PP were characterized by using LOI, UL-94 test, cone calorimetry, and TGA, respectively. By SEM, the char structure of PP-MTP was analyzed. XRD diffraction tests showed that PP-matrix of PP-MTP presented better crystallized phases, when MTP was modified by methyl hydrogen siloxane. The relations of the dispersion of MTP in PP matrix to the compatibility between PP and MTP, and to the flame retardancy were discussed. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, the feasibility of electrospinning oil-in-water type emulsions was evaluated, and it was shown that the Taylor cones and electrified liquid jets were stable even when the emulsion drops were as large as a few-ten microns in diameter.
Abstract: We evaluate the feasibility of electrospinning oil-in-water type emulsions. The emulsions had an aqueous solution of polyethylene oxide (PEO) as the continuous phase, and either mineral oil or a polystyrene (PS) in toluene solution as the drop phase. The Taylor cones and electrified liquid jets were stable even when the emulsion drops were as large as a few-ten microns in diameter. The resulting electrospun PEO fibers incorporated the dispersed phase of the emulsion in the form of drops (in case of mineral oil), or in the form of solid particles (in case of PS). Mineral oil drops appear to be completely encapsulated in the PEO fibers, whereas the PS particles are either incompletely encapsulated, or covered by only a very thin layer of PEO. Calculations show that in both cases, the initially large emulsion drops are broken during the electrospinning process. Copyright © 2007 John Wiley & Sons, Ltd.
TL;DR: In this paper, the results from the microcombustion calorimeter screening suggested that the system with the best flammability performance was a combination of organophosphonate and zinc borate and not one of the polymer nanocomposite systems.
Abstract: Through the use of microcombustion calorimetry several polymer nanocomposite, flame retardant (FR), and polymer nanocomposite + FR systems were screened for flammability performance. The use of this technique allowed for the creation of small batch (less than 50 g) epoxy formulations as compared to 400–500 g needed for cone calorimeter testing of epoxy + fiberglass panels. The results from the microcombustion calorimeter screening suggested that the system with the best flammability performance was a combination of organophosphonate and zinc borate, and not one of the polymer nanocomposite systems. This best candidate was then scaled up and fabricated into a fiberglass-reinforced composite which was further tested by a cone calorimeter. This paper shows some of the correlations between the microcombustion and cone calorimeter results for this single sample, provides some reasons for why the polymer nanocomposite samples did not provide the best results in flammability reduction, and suggests some caveats when using microcombustion calorimetry as the only screening tool for flammability. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, polyaniline-carboxylic acid functionalized multi-walled carbon nanotube (PAni/c-MWNT) nanocomposites were prepared in sodium dodecyl sulfate (SDS) emulsion.
Abstract: Polyaniline-carboxylic acid functionalized multi-walled carbon nanotube (PAni/c-MWNT) nanocomposites were prepared in sodium dodecyl sulfate (SDS) emulsion. First, the c-MWNTs were dispersed in SDS emulsion then the aniline was polymerized by the addition of ammonium persulfate in the absence of any added acid. SDS forms the functionalized counterion in the resulting nanocomposites. The content of c-MWNTs in the nanocomposites varied from 0 to 20 wt%. A uniform coating of PAni was observed on the c-MWNTs by field-emission scanning electron microscopy (FESEM). The PAni/c-MWNT nanocomposites have been characterized by different spectroscopic methods such as UV-Visible, FT-Raman, and FT-IR. The UV-Visible spectra of the PAni/c-MWNT nanocomposites exhibited an additional band at around 460 nm, which implies the induced doping of the MWNTs by the carboxyl group. The FT-IR spectra of the PAni/c-MWNT nanocomposites showed an inverse intensity ratio of the bands at 1562 and 1480 cm−1 as compared to that of pure PAni, which reveals that the PAni in the nanocomposites is richer in quinoid units than the pure PAni. The increase in the thermal stability of conductivity of the nanocomposites was due to the network structure of nanotubes and the charge transfer between the quinoid rings of the PAni and the c-MWNTs. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, the absorption characteristics of alginate wound dressings were analyzed and it was found that alginates absorb a large quantity of liquid into the fiber structure, in addition to those held between the fibers in the textile structure.
Abstract: Calcium alginate fibers have a novel gel-forming capability in that, upon the ion exchange between sodium ions in the contact solution and calcium ions in the fiber, the fiber slowly transforms into a fibrous gel. This paper reviews the principles of the gel-forming process for alginate fibers and analyzed the gelling behavior of various types of alginate fibers. The absorption characteristics of alginate wound dressings were analyzed and it was found that alginate wound dressings absorb a large quantity of liquid into the fiber structure, in addition to those held between the fibers in the textile structure. This gives rise to the unique gel blocking properties of alginate wound dressings. In addition, alginate wound dressings also have novel hemostatic and antimicrobial properties as well as the ability to promote wound healing. They are now widely used in the management of highly exuding wounds such as leg ulcers, pressure sores, and surgical wounds. Copyright © 2007 John Wiley & Sons, Ltd.
TL;DR: In this article, the performance of polypropylene-magnesium hydroxide-clay composites of different morphologies was compared and the results confirmed that fibrous and layered clay nanofillers act synergistically and can be combined with MH microfillers advantageously for improving the flame retardancy of PP composites.
Abstract: Fire retardancy behavior of polypropylene–magnesium hydroxide–clay composites of different morphologies is presented. Layer- and needle-like clay nanoparticles in natural and organically surface modified form have been compared. Fire retardant performance of the composites was evaluated by conical combustor and by horizontal burning test, while the structure was characterized by SEM. Rheological analysis of varied temperature provided further information about the strength of the formed combustion residue. The results confirm that fibrous and layered clay nanofillers act synergistically and can be combined with MH microfillers advantageously for improving the flame retardancy of PP composites. Significant improvements were observed in combustion parameters, as well as in flammability classifications. Combination of montmorillonite and sepiolite type of clays resulted in the increased time to ignition, and markedly decreased heat release rate. These advancements are ascribed to the char stabilizer effect of nanofillers leading to increased strength of the residue. It is also concluded that not only the interaction between micro- and nanofillers, but also the nanofillers–nanofillers interaction plays a key role in fire retardant mechanism. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, superparamagnetic magnetite nanoparticles were synthesized induced by chitosan hydrogel under ambient conditions via iron ions assembly, and the inducing effect of chitosa hydrogels was discussed.
Abstract: Superparamagnetic magnetite nanoparticles were synthesized induced by chitosan hydrogel under ambient conditions via iron ions assembly, and the inducing effect of chitosan hydrogel was discussed. Results of X-ray diffraction and transmission electron microscopy indicate that the nanoparticles were inverse cubic spinel structure magnetite with diameter about 16 nm, and the superparamagnetic nanoparticles with narrow size distribution dispersed uniformly in chitosan. The magnetization measurements indicated that the nanoparticles showed the typical superparamagnetic behavior. The crystallinity, morphology, and magnetic properties of magnetite nanoparticles were remarkably influenced by the pH values of iron ion solutions. The interaction between magnetite and chitosan was illustrated by FT-IR and thermogravimetric analysis, which concluded that the magnetite nanoparticles were coated by a chitosan layer via the amino groups of chitosan. The chitosan hydrogel assisted in the synthesis of superparamagnetic magnetite nanoparticles through chelation by amino groups. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, a cross-linked polybenzimidazole (PBI) membrane with dichloromethyl phosphinic acid (DCMP) is presented.
Abstract: Phosphoric acid doped polybenzimidazole (PBI) membranes have been covalently cross-linked with dichloromethyl phosphinic acid (DCMP). FT-IR measurements showed new bands originating from bonds between the hydrogen bearing nitrogen in the imidazole group of PBI and the CH2 group in DCMP. The produced cross-linked membranes show increased mechanical strength, making it possible to achieve higher phosphoric acid doping levels and therefore higher proton conductivity. Oxidative stability is significantly improved and thermal stability is sufficient in a temperature range of up to 250°C, i.e. within the temperature range of operation of PBI-based fuel cells. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this article, poly(methyl methacrylate) (PMMA) nanocomposites containing an organoclay and triphenyl phosphate (TPP) were prepared by solution blending using a PMMA solution in a MMA solvent.
Abstract: Poly(methyl methacrylate) (PMMA) nanocomposites containing an organoclay and triphenyl phosphate (TPP) were prepared by solution blending using a PMMA solution in methyl methacrylate (MMA) solvent. Exfoliated nanostructures were shown by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optical transmittance of the PMMA nanocomposites decreased with an increase in the clay content. The improvement in the thermal stability of the PMMA nanocomposites was greater in air than in nitrogen. Nanocomposite formation brought about reductions of the peak heat release rate (PHRR), as measured by cone calorimetry. The combination of the nanoclay and TPP brought about a further decrease in the PHRR and an increase in the average specific extinction area (ASEA, related to smoke production). Copyright © 2008 John Wiley & Sons, Ltd.