Preparation of conducting nylon‐6 electrospun fiber webs by the in situ polymerization of polyaniline

For the preparation of conducting polyaniline (PANI)/nylon composites with high electrical conductivity as well as superior mechanical properties such as flexibility and lightness, PANI/nylon‐6 composite nanofiber webs were prepared via the electrospinning process with a nylon‐6/formic acid polymer solution, and then PANI on the surface of the nylon‐6 electrospun nanofiber webs was chemically polymerized. The electrical conductivity measurements showed that the conductivity of the PANI/nylon‐6 composite electrospun fiber webs was superior to that of PANI/nylon‐6 plain‐weave fabrics because of the high surface‐area/volume ratios. On the other hand, the volume conductivities of the PANI/nylon‐6 composite electrospun fiber webs increased from 0.5 to 1.5 S/cm as the diffusion time increased from 10 min to 4 h because of the even distribution of PANI in the electrospun fiber webs. However, the surface conductivities of the PANI/nylon‐6 composite electrospun fiber webs somewhat decreased from 0.22 to 0.14 S/cm as the diffusion time increased because of PANI contaminated with aniline monomers, aniline oligomers, and some alkyl chains, which served as electrical resistants. These results were confirmed with Fourier transform infrared, electron spectroscopy for chemical analysis, and morphology analysis. It was concluded that the diffusion time for the in situ polymerization of PANI in electrospun fiber webs was optimized at approximately 3 h. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 983–991, 2005     

Effect of carbon black structure on low‐strain conductivity of polypropylene and low‐density polyethylene composites

The influences of carbon black (CB) structure on the percolation threshold, mechanical properties, and strain‐resistivity response of polymer composites are studied. Low‐density polyethylene (LDPE) and polypropylene (PP) samples were blended with five different types of CB differing in structure. Relatively low strains were studied; the maximum strain was 10%. It was found that the CB concentration for maximum strain‐sensitivity of the electrical conductivity is higher for low structure carbon blacks but is essentially independent of the CB structure for medium‐ to high‐structure carbon blacks. However, the composite containing the largest particle size carbon black clearly showed the highest strain‐sensitivity to electrical conduction. The mechanical properties and sensitivity of electrical resistivity to tensile strain of the filled composites examined in the study are also presented and discussed. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Investigation of electrically conductive acrylonitrile‐butadiene rubber

Electrically conductive acrylonitrile‐butadiene rubbers (NBRs) containing carbon black (CB) as conductive filler were prepared in order to investigate their electrical and mechanical properties. The effects of conductive CB loading, temperature, acrylonitrile content, crosslinking density of vulcanizates, and plasticizer on conductivity were studied. The change in electrical conductivity of NBRs with different amounts of CB showed that there is a certain critical point (percolation threshold) where a significant decrease in electrical resistivity (increase in conductivity) is observed. Mechanical properties such as tensile strength, elongation to break, and surface hardness of vulcanized NBRs were measured. It was found that the percolation threshold was 5 phr of CB for the NBR/CB composites. J. VINYL ADDIT. TECHNOL., 13:71–75, 2007. © 2007 Society of Plastics Engineers.     

Influence of carbon black properties on the Joule heating stimulated shape‐memory behavior of filledethylene‐1‐octene copolymer

The shape‐memory (SM) behavior of ethylene‐1‐octene copolymer (EOC) reinforced by carbon black (CB) was investigated. Two CB types, N110 and EC600, with different structure and specific surface area were used as conductive fillers. The mechanical tests showed that on addition of CB into EOC, modulus and strength increased significantly for both CB types but the elastic behavior stands on. The electrical resistivity decreases drastically with increasing CB content. The thermally stimulated SM recovery is deteriorated significantly because of the rigid CB network formed in EOC. With increasing temperature, the CB network gradually loses its rigidity, as the glassy polymer layers connecting the CB aggregates become softened. As a result, the samples with high CB content could recover nearly 100%. In this work, a sample preparation and a corresponding arrangement of experiment were introduced, which allows to quantify the Joule heating stimulated recovery behavior. EOC containing 17 wt% CB EC600 reaches a low resistivity of 8 Ω cm and shows good Joule heating stimulated SM recovery of up to 97% at a voltage of 15 V. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Flame‐retardant fabric systems based on electrospun polyamide/boric acid nanocomposite fibers

To examine the feasibility of developing flame‐retardant‐textile coated fabric systems with electrospun polyamide/boric acid nanocomposites, fiber webs coated on cotton substrates were developed to impart‐fire retardant properties. The morphology of the polyamide/boric acid nanocomposite fibers was examined with scanning electron microscopy. The flame‐retardant properties of coated fabric systems with different nanoparticle contents were assessed. The flame retardancy of the boric acid coated fabric systems was evaluated quantitatively with a flammability test apparatus fabricated on the basis of Consumer Product Safety Commission 16 Code of Federal Regulations part 1610 standard and also by thermogravimetric analysis. The 0.05 wt % boric acid nanocomposite fiber web coated on pure cotton fabric exhibited an increment in flame‐spreading time of greater than 80%, and this indicated excellent fire protection. Also, the coated fabric systems with 0.05% boric acid nanocomposite fiber webs exhibited a distinct shift in the peak value in the thermal degradation profile and a 75% increase in char formation in the thermooxidative degradation profile, as indicated by the results of thermogravimetric analysis. The results show the feasibility of successfully imparting flame‐retardant properties to cotton fabrics through the electrospinning of the polymer material with boric acid nanoparticles. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

High strength nylon micro‐ and nanofiber based nonwovens via spunbonding

In this study we explore the feasibility of using of islands‐in‐the‐sea (I/S) fibers in the spunbond process to produce relatively high strength micro‐ and nanofiber webs. The relationships between the number of islands, percent polymer composition, and the fiber and fabric properties are reported. Nylon 6 (N6) and poly (lactic) acid (PLA) were used as the islands and sea polymers, respectively. Micro‐ and nanofibers were obtained by dissolving PLA polymer from the final spunbond nonwovens. The fibers with 25% N6 showed a decrease in fiber diameter from 1.3 to 0.36 μm (micron) when the number of islands was increased from 36 to 360. The diameter of fibers with 75% N6 showed a decline from 2.3 to 0.5 μm for the same range. Hydroentangling was found to be the preferred method of bonding of the I/S structures; the bonded structures were able to withstand postprocessing steps required for dissolving of the sea from the resulting nonwovens. Hydroentanged micro‐ and nanofiber based nonwovens demonstrated high tensile and tear properties, which were insensitive to the N6 fiber size and its mechanical properties. Bonding efficiency and web uniformity were found to be dominant factors influencing the fabric performance. Overall, our study demonstrated that the I/S configuration is a promising technique for high speed and high throughput production of strong and light weight nonwovens comprised of micro‐ and nanofibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The Preparation and property of poly(lactic acid)/tourmaline blends and melt‐blown nonwoven

Poly(lactic acid) melt‐blown (MB) webs were melt‐spun by MB processing of poly(lactic acid) and poly(lactic acid)/filler blends. The effect of tourmaline particles on the structure, morphology, mechanical and filtration properties of poly(lactic acid) blends, and MB webs were reported. The blends and MB webs were characterized using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WXRD), scanning electron microscopy (SEM), and pore size meter (PSM). The degree of crystallinity of blends with tourmaline particles was more than that of poly(lactic acid) alone. SEM micrographs revealed a good dispersion of the additive in the blends and fiber webs. The tourmaline particles offered some benefits to the mechanical properties of the MB web. MB web samples with tourmaline had larger pore size, high surface charge density, and higher filtration efficiency. POLYM. COMPOS., 36:264–271, 2015. © 2014 Society of Plastics Engineers     

Recycled milk pouch and virgin LDPE‐LLDPE‐based jute fiber composites

The present investigation deals with the thermo‐mechanical recycling of post consumer milk pouches (LDPE‐LLDPE blend) and its use as jute fiber composite materials for engineering applications. The mechanical, thermal, morphological, and dynamic‐mechanical properties of recycled milk pouch‐based jute fiber composites with different fiber contents were evaluated and compared with those of the virgin LDPE‐LLDPE/jute fiber composites. Effect of artificial weathering on mechanical properties of different formulated composites was determined. The recycled polymer‐based jute fiber composites showed inferior mechanical properties as well as poor thermal stability compared to those observed for virgin polymer/jute fiber composites. However, the jute‐composites made with (50:50) recycled milk pouch‐virgin LDPE‐LLDPE blend as polymer matrix indicated significantly superior properties in comparison to the recycled milk pouch/jute composites. Overall mechanical performances of the recycled and virgin polymeric composites were correlated by scanning electron microscopy (SEM). The dynamic mechanical analysis showed that storage modulus values were lower for recycled LDPE‐LLDPE/jute composites compared to virgin LDPE‐LLDPE/jute composites throughout the entire temperature range, but an increase in the storage modulus was observed for recycled‐virgin LDPE‐LLDPE/jute composites. POLYM. COMPOS. 28:78–88, 2007. © 2007 Society of Plastics Engineers     

Melt‐blowing thermoplastic polyurethane and polyether‐block‐amide elastomers: Effect of processing conditions and crystallization on web properties

Melt‐blown webs from ester and ether thermoplastic polyurethanes and polyether‐block‐amide (PEBA) elastomers were produced at different die‐to‐collector distances (DCD) to study the correlation between the polymer type and hardness, melt‐blowing process conditions, and web properties. An experimental set up was built to measure the air temperature and velocity profiles below and across the melt‐blowing die to correlate the fiber formation process and polymer crystallization behavior to process conditions and web properties. It was shown that air temperature and velocity profiles follow similar trends with increasing distance below the melt‐blowing die: both drop rapidly until reaching a plateau region approximately 5–6 cm below the die. Thereafter, they remain relatively constant with further increasing distance. It was found that crystallization onset and peak temperatures of all block copolymers in this study fall within this region of rapid velocity and temperature drop. This suggests that the polymers have already started to crystallize and solidify before reaching the collector, the extent of which depends on the crystallization kinetics of the polymer. The strong influence of the crystallization kinetics on web strength was clearly demonstrated in the PEBA series. In particular, the hardest grade produced the lowest web strength mainly because of its high crystallization rate and crystallization onset temperature. It is concluded that the melt‐blown web strength is strongly dependent on the degree of fiber‐to‐fiber adhesion within the web, which is determined by the amount of fiber solidification that occurs prior to the collector. The crystallization kinetics of the polymer and the distances traveled between the die and collector or the exposure time of the polymer melt to process and ambient air were shown to be critical in the amount of fiber solidification attained. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Effect of the Air‐Jet and the False‐Twist texturing processes on the stress‐relaxation of polyamide 6.6 yarns

Polyamide 6.6 multifilament yarns were converted to crimped fibers by texturing to simulate the properties of natural staple fiber yarns for textile applications. Texturing is carried out by mechanical stresses (turbulences or twisting) under thermal or hydrothermal conditions which affect the fine structure of the fiber. Two polyamide yarns with the same linear density but composed of filaments of different fineness were textured by the False‐Twist (thermal) and the Air‐Jet (hydrothermal) procedures. The influence of texturing and filament fineness on the relaxation behavior of the yarns was studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Multiple percolation in a carbon‐filled polymer composites via foaming

This article describes an investigation into the effects of foaming on the electrical conductivity for a carbon‐filled cyclic olefin copolymer (COC) composite incorporating both chopped carbon fibers (cCF) and carbon black (CB). Foamed and solid samples were injection molded and then analyzed for cell size, fiber length, fiber orientation, and electrical conductivity. Foamed samples exhibited higher electrical conductivity in the through‐plane direction for materials containing only CB or composites containing both filler types, and reduced electrical conductivity in the cCF‐filled composites. The increased electrical property gained by foaming was attributed to multiple percolation with CB aggregates forming more effective conductive clusters and networks in the continuous polymer phase during growth of the gas domains. A mechanism for the phenomenon was proposed based on these experimental observations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

In vitro degradation and drug‐release behavior of electrospun,fibrous webs of poly(lactic‐co‐glycolic acid)

Ultrafine fibrous webs of poly(lactide‐co‐glycolic acid) (PLGA) containing the bactericidal antibiotic drug rifampin were prepared by electrospinning, and their properties were investigated for wound‐dressing applications. Because PLGA is a biodegradable and biocompatible polymer, it is one of the best materials for the preparation of wound‐dressing substrates. Through this investigation of PLGA/rifampin electrospun webs, we found that the in vitro degradation reached approximately 60% in 10 days, and the drug release from the webs showed a fast and constant profile suitable for wound‐dressing applications. Also, we observed that both the web‐degradation rate and the drug‐release rate increased as the drug concentration in the PLGA/rifampin electrospun webs and the content level of glycolide units in the PLGA polymer matrix increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Recycled milk pouch and virgin low‐density polyethylene/linear low‐density polyethylene based coir fiber composites

The viability of the thermomechanical recycling of postconsumer milk pouches [a 50 : 50 low‐density polyethylene/linear low‐density polyethylene (LDPE–LLDPE) blend] and their use as polymeric matrices for coir‐fiber‐reinforced composites were investigated. The mechanical, thermal, morphological, and water absorption properties of recycled milk pouch polymer/coir fiber composites with different treated and untreated fiber contents were evaluated and compared with those of virgin LDPE–LLDPE/coir fiber composites. The water absorption of the composites measured at three different temperatures (25, 45, and 75°C) was found to follow Fickian diffusion. The mechanical properties of the composites significantly deteriorated after water absorption. The recycled polymer/coir fiber composites showed inferior mechanical performances and thermooxidative stability (oxidation induction time and oxidation temperature) in comparison with those observed for virgin polymer/fiber composites. However, a small quantity of a coupling agent (2 wt %) significantly improved all the mechanical, thermal, and moisture‐resistance properties of both types of composites. The overall mechanical performances of the composites containing recycled and virgin polymer matrices were correlated by the phase morphology, as observed with scanning electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Nanoparticle effects on structure and properties of polypropylene meltblown webs

The effect of nanoclay additive on the structure, morphology, and mechanical properties of polypropylene meltblown webs is reported here for the first time. Effect of nanoclay on the meltblown processing, resultant fiber web structure, and properties are discussed. Combination of wide‐angle x‐ray diffraction, differential scanning calorimetry, and transmission electron microscopy were used to determine the nature of clay dispersion in the polypropylene fiber matrix and resultant morphology. Transmission electron microscopy micrographs revealed nanolevel dispersion of the additive in the fiber web. Clay additive did not offer any benefit as far as the mechanical properties of the meltblown web are concerned. Meltblown web samples with nanoclay had higher variability in web structure, high air permeability, high stiffness, and lower mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

HIPS/γ‐irradiated UHMWPE/carbon black blends: Structuring and enhancement of mechanical properties

CB‐containing HIPS/UHMWPE and HIPS/XL‐UHMWPE are unique systems, in which structuring takes place, affecting the electrical (to be described in a future article), rheological, mechanical, and dynamical‐mechanical properties. The XL‐UHMWPE particles have undergone structural fixation due to the crosslinking, maintaining their porosity and internal intricate structure even after high‐temperature melt processing, as opposed to the UHMWPE particles. Differences in the flow mechanisms of HIPS/UHMWPE and HIPS/XL‐UHMWPE blends have been attributed to polymer viscous flow in the former case vs. particle slippage in the latter. The mechanical properties of HIPS/UHMWPE are enhanced when utilizing XL‐UHMWPE as a dispersed phase, especially the strength, because of changes in the inherent properties of the UHMWPE following irradiation, and in particular, the nature of the HIPS/XL‐UHMWPE interface. The results for the CB‐containing 70HIPS/30XL‐UHMWPE blend are especially surprising and of practical importance, due to the fact that no degradation of the mechanical properties has occurred as a result of the CB incorporation. The dynamical mechanical properties reflect the differences between the UHMWPE and XL‐UHMWPE‐containing blends as well. The presence of either type of UHMWPE, CB content, and blend composition affect the dissipation, but have only a minor influence on the transition temperatures of the components. Of special interest is the increased damping of XL‐UHMWPE–containing compositions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1731–1744, 1999     

Conducting property of carbon black filled poly(ethylene glycol)/poly(methyl methacrylate) composites as gas‐sensing materials

To reveal the role of crystalline polymers in carbon black (CB) filled amorphous polymer composites and improve the mechanical properties of composite films, CB/poly(ethylene glycol) (PEG)/poly(methyl methacrylate) (PMMA) composites were synthesized by polymerization filling in this work. The electrical conductive property and response to organic solvent vapors of the composites were investigated. The composites, characterized by a relatively low percolation threshold (～ 2.1 wt %), had lower resistivity than CB/PMMA composites prepared with the same method because of the different dispersion status of CB particles in the matrix polymer. The concentration and molecular weight of PEG notably influenced the electrical response of the composites against organic vapors. The drastic increase in the electrical resistance of the composites in various organic vapors could be attributed mainly to the swelling of the amorphous polymer matrix in the solvent but not to that of the crystalline polymer. These findings could help us to understand the conductive mechanism and electrical response mechanism of the composites as promising gas‐sensing materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Effects of the tacticities of poly(vinyl alcohol) on the structure and morphology of poly(vinyl alcohol) nanowebs prepared by electrospinning

The effects of tacticities on the characteristics of poly(vinyl alcohol) (PVA) nanowebs prepared by an electrospinning technique were investigated. PVA webs composed of uniform nanofibers with syndiotactic dyad (s‐dyad) contents of 53.5 and 57.3% were successfully obtained with electrospinning. By changing processing parameters such as the initial polymer concentration, applied voltage, and tip‐to‐collector distance, we found suitable conditions for forming PVA webs with uniform nanofibers. PVAs of higher s‐dyad contents were prepared at a lower solution concentration and at a higher applied voltage because of the easy formation of syndiotactic PVA chain entanglements at a very low polymer concentration. The average diameter of the nanofibers in a PVA web with the higher s‐dyad content of 57.3% (ca. 240 nm) was thinner than that of the nanofibers in a PVA web with the lowers‐dyad content of 53.5% (ca. 270 nm). In addition, the crystallinity and thermal stability were greatly increased with an increase in the s‐dyad content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Three‐dimensional nonwoven flax fiber reinforced polylactic acid biocomposites

Three‐dimensional (3D) shell‐structured PLA/Flax biocomposites were fabricated using a novel method incorporating the 3D nonwoven web‐forming process. PLA and flax fibers were blended in the fiber opening stage and converted to webs on the 3D mold using the air‐laying principle. The 3D webs were then consolidated by through‐air thermal bonding. The compression molding technique was used finally to convert the 3D webs to the biocomposites. The relationship between the main process parameters and the properties of the biocomposites was investigated. The results show that with increasing flax fiber content, the crush failure load, total energy absorption, specific energy absorption, and crush efficiency increased. The crushing properties decreased with increased molding temperature, but the crushing properties are not significantly affected by the molding time. The physical properties of 3D biocomposites were also evaluated and the appropriate processing parameters for 3D biocomposites were established. POLYM. COMPOS., 35:1244–1252, 2014. © 2013 Society of Plastics Engineers     

Partially miscible poly(lactic acid)‐ blend‐poly(propylene carbonate) filled with carbon black as conductive polymer composite

BACKGROUND: Conductive polymer composites (CPCs) can be obtained by filling polymer matrices with electrically conductive particles, and have a wide variety of potential applications. In the work reported, the biodegradable polymer poly(lactic acid) (PLA) as a partially miscible blend with poly(propylene carbonate) (PPC) was used as a polymer matrix. Carbon black (CB) was used as the conducting filler. RESULTS: Fourier transform infrared spectroscopy revealed interactions between matrix and CB filler; this interaction was stronger in PPC‐blend‐CB than in PLA‐blend‐CB composites. A rheology study showed that low‐viscosity PPC could improve the fluidity of the CPCs, but decrease that of CB. With increasing CB content, the enforcement effect, storage modulus and glass transition temperature increased, but the elongation at break decreased. CPCs exhibited the lowest electrical percolation thresholds of 1.39 vol.% CB when the content of PPC in PLA‐blend‐PPC was 40 wt%. The conductivity of CPCs containing 5.33 vol.% CB and 40 wt% PPC reached 1.57 S cm^?1. Scanning electron microscopy revealed that CB exhibits a preference for dispersion in the low‐viscosity phase (PPC) of the multiphase matrix. CONCLUSION: In the presence of CB, partially miscible PLA‐blend‐PPC could form multi‐percolation CPCs. Moreover, the combination of PLA and PPC with CB broadens novel application of both renewable polymers and CPCs. Copyright © 2008 Society of Chemical Industry     

Polyaniline‐coated PET conductive yarns: Study of electrical,mechanical, and electro‐mechanical properties

Intelligent and multifunctional yarns (textiles) have attracted interest because of their high potential in applications such as flexible displays, batteries, or sensors. The main objective of our research was to obtain the flexible and electrically conducting yarn based on the conductive polymer and polyethylene terephtalate (PET) yarns. Among the conductive polymers, polyaniline (PANI) is considered as a promising material and is well adapted for modifications of textile structure because of its excellent environmental, thermal, and chemical stability. Chemical PANI coating on PET yarns was performed by absorption of yarns through PANI solution. The electrical, mechanical, and electro‐mechanical properties of PET conductive yarns prepared were investigated. The environmental effects on the electrical and mechanical properties of the obtained conductive yarns were also studied. These conductive yarns are expected to be used as fibrous sensors, connection devices in smart clothing, and for electromagnetic shielding applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1252–1256, 2006