Aliphatic–aromatic polyester–polyaniline composites: preparation,characterization, antibacterial activity and conducting properties

Poly(butylene adipate‐co‐terephthalate) (PBAT) composites containing polyaniline (PANI) were prepared using a melt blending process. Acrylic‐acid‐grafted PBAT (PBAT‐g‐AA) and PANI were used to improve the compatibility and dispersibility of PANI within the PBAT matrix. The composites were characterised morphologically using scanning electron microscopy, chemically using Fourier transform IR spectrometry and ¹³C solid‐state nuclear magnetic resonance, and optically using UV‐visible spectroscopy. The electrical conductivity of the composites was also evaluated with a resistance tester and a cyclic voltameter. Escherichia coli (BCRC 10239) was chosen as the standard bacterium for determining the antibacterial properties of the composite materials. The anti‐static properties of the composites were also evaluated. The PBAT‐g‐AA/PANI composite showed markedly enhanced antibacterial and anti‐static properties due to the formation of amide bonds by the condensation of the carboxylic acid groups of PBAT‐g‐AA with the amino groups of PANI. The optimal level of PANI was 9 wt%, as excess PANI led to separation of the two organic phases, lowering their compatibility. Copyright © 2012 Society of Chemical Industry     

The effect of carbon nanotube on the physical properties of poly(butylene terephthalate) nanocomposite by simple melt blending

Polyester nanocomposites based on poly(butylene terephthalate) (PBT) and carbon nanotube (CNT) were prepared by simple melt blending using a twin‐screw extruder. There is significant dependence of the thermal, rheological, and mechanical properties of the PBT nanocomposites on the concentration and dispersion state of CNT. The storage and loss moduli of the PBT nanocomposites increased with increasing frequency, and this enhancing effect was more pronounced at lower frequency region. The nonterminal behavior for the PBT nanocomposites was attributed to the nanotube–nanotube or polymer–nanotube interactions, and the dominant nanotube–nanotube interactions at high CNT content resulted in the formation of the interconnected network‐like structures of CNT in the PBT nanocomposites. The incorporation of a small quantity of CNT into the PBT matrix can substantially improve the mechanical properties, the heat distortion temperature, and the thermal stability of the PBT nanocomposites. The unique character of CNT dispersed in the PBT matrix resulted in the physical barrier effect against the thermal decomposition, leading to the improvement in the thermal stability of the PBT nanocomposites. This study also provides a design guide of CNT‐reinforced PBT nanocomposites with a great potential for industrial uses. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A comparative study of fracture behavior between carbon black/poly(ethylene terephthalate) and multiwalled carbon nanotube/poly(ethylene terephthalate) composite films

Fracture behavior of amorphous poly(ethylene terephthalate) (PET) films added multiwalled carbon nanotube (MWCNT) has been compared with that of the PET films added with carbon black (CB) to elucidate the effects of the large aspect ratio of MWCNT. Fracture toughness has been evaluated using the essential work of fracture tests. Evolution of the crazes has been analyzed by conducting time‐resolved small‐angle X‐ray scattering measurements during tensile deformation of the films at room temperature using synchrotron radiation. CB and MWCNT increased the fracture toughness of the PET film by increasing the plastic work of fracture. This resulted from the effects of the fillers to prevent the localization of deformation upon the crazes formed at earlier stages of tensile deformation and to retard the growth of the fibrils in the crazes to a critical length. The CB particles provided a number of sites where the crazes were preferably formed due to stress concentration. In the case of MWCNT, on the other hand, the widening of the crazes formed at earlier stages was suppressed due to the bridging effect arising from the large aspect ratio of MWCNT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of the viscosity and processing parameters on the surface resistivity of polypropylene/multiwalled carbon nanotube and ethylene–propylene–diene/multiwalled carbon nanotube nanocomposites

In this study, relatively large amounts of polypropylene (PP) and ethylene–propylene–diene (EPDM) were melt‐mixed with multiwalled carbon nanotubes (MWCNTs). Although the melt‐compounding method has many advantages, the uniform dispersion of carbon nanotubes in the polymer matrix is still the most challenging task. Because the electrical conductivity of composites is strongly influenced by the filler's state of dispersion and the extent of filler breakage during processing, the effects of the viscosity and processing conditions, such as the mixing time, rotor speed, and cooling rate, on the surface resistivity were studied. The PP/MWCNT nanocomposites displayed a high dependence of surface resistivity on the cooling rate, and the EPDM/MWCNT nanocomposites displayed a higher surface resistivity at the same content of MWCNTs and less dependence of surface resistivity on the cooling rate compared with PP/MWCNT nanocomposites. The increased surface resistivity of the EPDM/MWCNT nanocomposites was observed when EPDM with higher viscosity was used to prepare the EPDM/MWCNT nanocomposites. By increasing the rotor speed, lower surface resistivity was obtained in the PP/MWCNT nanocomposites. However, by increasing the rotor speed, a higher surface resistivity was obtained in the EPDM/MWCNT nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effect of multiwalled carbon nanotube dimensions on the morphology,mechanical, and electrical properties of melt mixed polypropylene‐based composites

The effect of multiwalled carbon nanotube (MWCNT) dimensions and surface modification on the morphology, mechanical reinforcement, and electrical properties of PP‐based composites, prepared by melt mixing, has been studied. The MWCNTs of small (d < 10 nm) and large (d = 40–60 nm) diameters with various intrinsic aspect ratios (L/d) have been used as filler. Transmission electron microscopy and very cold neutrons (VCN) scattering showed that both as‐received and surface modified small diameter MWCNT(1)s exhibit a strong tendency to bundle or cluster together in melt compared to both long MWCNT(3)s and short MWCNT(2)s large diameter nanotubes. The fractions of isolated nanotubes are higher and the mass‐fractal dimensions are lower for thick MWCNT‐based nanocomposites. The nanotubes of all types are heterogeneous nucleation sites for PP crystallization. The tensile and DMA testing results revealed that both long thick MWCNT(3)s with L/d ≈ 300 and thin MWCNT(1)s with highest intrinsic L/d > 1000 exhibit similar reinforcing effects, because drastically decreasing the effective aspect ratio (L/d)_eff of the thin flexibly nanotubes within polymer matrix. The nanocomposites based on the long large diameter MWCNT(3)s demonstrated the lowest percolation threshold equal to 1.5 vol % loading, highest dielectric and electromagnetic waves shielding properties. It was concluded that the choice of optimal diameter and length of MWCNTs is right approach to the improvement in the dispersion state and straightness of multiwelled carbon nanotubes in polymer melt as well as to enhancement of their efficiency as reinforcing and conductive nanosized filler. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rheology,crystallization behaviors,and thermal stabilities of poly(butylene succinate)/pristine multiwalled carbon nanotube composites obtained by melt compounding

Poly(butylene succinate) (PBS)/pristine raw multiwalled carbon nanotube (MWCNT) composites were prepared in this work via simple melt compounding. Morphological observations indicated that the MWCNTs were well dispersed in the PBS matrix. Moreover, the incorporation of MWCNTs did not affect the crystal form of PBS as measured by wide‐angle X‐ray diffraction. The rheology, crystallization behaviors, and thermal stabilities of PBS/MWCNT composites were studied in detail. Compared with neat PBS, the incorporation of MWCNTs into the matrix led to higher complex viscosities (|η*|), storage modulus (G′), loss modulus (G″), shear thinning behaviors, and lower damping factor (tan δ) at low frequency range, and shifted the PBS/MWCNT composites from liquid‐like to solid‐like, which affected the crystallization behaviors and thermal stabilities of PBS. The presence of a very small quantity of MWCNTs had a significant heterogeneous‐nucleation effect on the crystallization of PBS, resulting in the enhancement of crystallization temperature, i.e., with the addition of 0.5 wt % MWCNTs, the values of T_c of PBS/MWCNT composites could attain to 90°C, about 6°C higher than that of neat PBS, whereas the values of T_c increased slightly with further increasing the MWCNTs content. The thermogravimetric analysis illustrated that the thermal stability of PBS was improved with the addition of MWCNTs compared with that of neat PBS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization and preparation of new multiwall carbon nanotube/conducting polymer composites by in situ polymerization

Composites based on poly(diphenyl amine) (PDPA) and multiwall carbon nanotubes (MWNTs) were prepared by chemical oxidative polymerization through two different approaches: in situ polymerization and intimate mixing. In in situ polymerization, DPA was polymerized in the presence of dispersed MWNTs in sulfuric acid medium for different molar composition ratios of MWNT and DPA. Intimate mixing of synthesized PDPA with MWNT was also used for the preparation of PDPA/MWNT composites. Transmission electron microscopy revealed that the diameter of the tubular structure for the composite was 10–20 nm higher than the diameter of pure MWNT. Scanning electron microscopy provided evidence for the differences in the morphology between the MWNTs and the composites. Raman and Fourier transform IR (FTIR) spectroscopy, thermogravimetric analysis, X‐ray diffraction, and UV–visible spectroscopy were used to characterize the composites and reveal the differences in the molecular level interactions between the components in the composites. The Raman and FTIR spectral results revealed doping‐type molecular interactions and coordinate covalent‐type interactions between MWNT and PDPA in the composite prepared by in situ polymerization and intimate mixing, respectively. The backbone structure of PDPA in the composite decomposed at a higher temperature (>340°C) than the pristine PDPA (～300°C). This behavior also favored the molecular level interactions between MWNT and PDPA in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3721–3729, 2006     

Partially Bio-Based Polyester Bead Foams via Extrusion Foaming of Poly(butylene terephthalate)/Poly(butylene furanoate) Blends

The interest in bio-based alternatives to classical polyesters such as poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) is steadily growing to achieve a more sustainable approach to polymer materials. In this study, PBT/poly(butylene furanoate) (PBF) blends are prepared, characterized and extrusion foamed. PBF as a bio-based polyester offers two advantages. The ecological footprint of the material is reduced, and additionally, it can be used in Diels-Alder reactions at the blend surface to support fusion of the foamed beads. The blending behavior of the polyesters is investigated using samples prepared in a microcompounder, particularly focused on the miscibility of the blends and transesterification reactions. The blends are thermodynamically immiscible but show a certain degree of transesterification according to nuclear magnetic resonance (NMR) spectroscopy. The morphology of blend beads produced by an extrusion foaming process is analyzed regarding their cell density, cell size distribution, and open-cell content. It is shown that PBF has a positive effect on the bead foam morphology. The use of a bifunctional linker designed for chemical fusion of the bead surfaces allows to obtaining of molded parts, in contrast to beads containing pure PBT.     

Rheological and electrical properties of polycarbonate/multi-walled carbon nanotube composites

Rheological and electrical properties of the polycarbonate (PC)/multi-walled carbon nanotube (MWNT) were studied. The MWNT was funtoinalized by treating with the hydrogen peroxide (H₂O₂). The H₂O₂ treated MWNT was dried by thermal and freeze drying methods. From the morphological studies, the degree of entanglement of the MWNT was decreased after treating with the H₂O₂. For the H₂O₂ treated MWNT (thermal drying), the length of the MWNT was shortened compared that of the H₂O₂ treated MWNT (freeze drying). The rheological and electrical properties of the PC/MWNT (H₂O₂ treated) composites increased compared that of the PC/MWNT (untreated) composites. Also, the electrical conductivity showed higher value for the PC/MWNT (H₂O₂ treated, freeze drying) composites compared that of the PC/MWNT (H₂O₂ treated, thermal drying) composites. From the results of the morphological, rheological, and electrical properties of the PC/MWNT composites, it is suggested that the electrical and rheological properties of the PC/MWNT composites are affected by the MWNT-MWNT network structure, which is related with the MWNT morphologies such as the degree of aggregation and aspect ratio of the MWNT.     

Mechanical and thermal properties of polyphenylene sulfide/multiwalled carbon nanotube composites

Polyphenylene sulfide (PPS)/multiwalled carbon nanotube (MWCNT) composites were prepared using a melt‐blending procedure combining twin‐screw extrusion with centrifugal premixing. A homogeneous dispersion of MWCNTs throughout the matrix was revealed by scanning electron microscopy for the nanocomposites with MWCNT contents ranging from 0.5 to 8.0 wt %. The mechanical properties of PPS were markedly enhanced by the incorporation of MWCNTs. Halpin‐Tsai equations, modified with an efficiency factor, were used to model the elastic properties of the nanocomposites. The calculated modulus showed good agreement with the experimental data. The presence of the MWCNTs exhibited both promotion and retardation effects on the crystallization of PPS. The competition between these two effects results in an unusual change of the degree of crystallinity with increasing MWCNT content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology,crystallization, and mechanical properties of poly(ethylene terephthalate)/multiwalled carbon nanotubes composites

Poly(ethylene terephthalate)/multiwalled carbon nanotubes (PET/MWCNTs) with different MWCNTs loadings have been prepared by in situ polymerization of ethylene glycol (EG) containing dispersed MWCNTs and terephthalic acid (TPA). From scanning electronic microscopy images of nanocomposites, it can be clearly seen that the PET/MWCNTs composites with low‐MWCNTs contents (0.2 and 0.4 wt %) get better MWCNTs dispersion than analogous with high‐tube loadings (0.6 and 0.8 wt %). The nonisothermal crystallization kinetics was analyzed by differential scanning calorimetry using Mo kinetics equation, and the results showed that the incorporation of MWCNTs accelerates the crystallization process obviously. Mechanical testing shows that, in comparison with neat PET, the Young's modulus and the yield strength of the PET nanocomposites with incorporating 0.4 wt % MWCNTs are effectively improved by about 25% and 15%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Comparative study of the rheological behavior of multiwalled carbon nanotubes and nanofiber composites prepared by the dilution of a masterbatch of polypropylene

In this investigation, the characteristics and the rheological properties of two different nanocomposite systems were investigated. These systems consisted of a dispersion of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) in a polypropylene (PP) matrix. The mixing process was carried out by melt compounding with a twin‐screw corotating extruder with different reinforcement amounts (0.2–20 wt %) from concentrated masterbatches (20 wt %) of PP/CNT and PP/CNF. The results show a remarkable increase in the viscosity for both blends as the reinforcement amount was increased. It was important to evaluate the rheological behavior to understand the effect of the nanocarbon particles on the internal structures and their processing properties of the obtained composites. CNFs were a more viable reinforcement from a processability point of view because the obtained viscosities of the PP/CNF blends were more manageable. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical and thermo-mechanical properties of carbon nanotube reinforced composites

A study on the mechanical and thermo-mechanical properties of carbon nanotube (CNT) reinforced nanocomposites is presented in this article. Mori–Tanaka method is used for modeling the effective stiffness and coefficient of thermal expansion. Regression formulas were developed to describe the effects of CNT orientation, aspect ratio, and CNT volume fraction. Given the statistical distributions of CNT orientations and aspect ratios, the effective properties can be conveniently derived by numerical integration using these formulas.     

Conductive network formation and electrical properties of poly(vinylidene fluoride)/multiwalled carbon nanotube composites: Percolation and dynamic percolation

Conductive network formation and its dynamic process for multiwalled carbon nanotubes (MWNTs) and carboxyl‐tethered MWNT (MWNT‐COOH) filled poly(vinylidene fluoride)(PVDF) systems were investigated. Based on real‐time tracing the variation of electrical resistivity of systems with isothermal treatment time, the conductive network formation was evaluated. It was found that the conductive network formation was temperature and time dependent. The percolation time, characterized at a certain annealing time where the electrical resistivity started to decrease drastically, decreased with the increase of the filler concentration or the annealing temperature. However, the values of the percolation time and the activation energy of conductive network formation for the PVDF/MWNT‐COOH system were higher than those of the PVDF/MWNT system, indicating that the interaction between MWNTs and PVDF molecules played an important role in the conductive network formation of the composites. Furthermore, a modified thermodynamic percolation model was proposed to predict the percolation time of PVDF/MWNT composites. It was found that the calculated results fit the experimental data very well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characterization and electrical conductivity of poly(ethylene glycol)/polyacrylonitrile/multiwalled carbon nanotube composites

Poly(Lactic acid) (PLA)‐layered silicate nanocomposite films were prepared by solvent casting method. The films were irradiated with Co⁶⁰ radiation facility at dose of 30 kGy. The effect of γ irradiation on mechanical properties of the neat PLA and nanocomposites was evaluated by data obtained from tensile testing measurements. The tensile strength of the irradiated PLA films increased with addition of 1 wt % triallyl cyanurate indicating crosslink formation. Significant ductile behavior was observed in the PLA nanocomposites containing 4 pph of nanoclay. Incorporation of nanoclay particles in the PLA matrix stimulated crystal growth as it was studied by differential scanning calorimetry. The morphology of the nanocomposites characterized by transmission electron microscopy and X‐ray diffraction revealed an exfoliated morphology in the PLA nanocomposite films containing 4 pph of nanoclay. Only very small changes were observed in the chemical structure of the irradiated samples as it was investigated by Fourier transform infrared spectroscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphology and electrical properties of carbon black/poly(ethylene terephthalate)/polypropylene composite

This work attempts to develop a carbon black (CB) filled conductive polymer composite based on poly(ethylene terephthalate) (PET) and polypropylene (PP). The process follows by localizing the CB particles in the minor phase (PET), and then the conductive masterbatch was elongated to form conductive microfibrils in PP matrix during melt extrusion process. After compression molding, a fine conductive three‐dimensional microfibrillar network is constructed. For comparison purpose, CB, PET, and PP are mixed using different pattern. The morphology and the volume resistivity of the obtained composites are evaluated. Electrical conductivity investigation shows that the percolation threshold and resistivity values are dependent on the CB concentration. The best morphological observation shows that the PET phases forms well‐defined microfibrils, and CB particles overwhelmingly localize in the surfaces of the PET microfibrils, which led to a very low percolation threshold, i.e., 4.5 phr, and a reasonable conductivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrical conductivity of single walled and multiwalled carbon nanotube containing wool fibers

The main purpose of this study was producing conductive wool fabric applying carbon nanotubes. Raw and oxidized wool samples were treated with carbon nanotubes in the impregnating bath in the presence of citric acid as a crosslinking agent and sodium hypophosphite as a catalyst while sonicating them in the ultrasonic bath. Electrical resistance, washing durability, and color variation of treated samples were assessed. Through SEM images, the surface morphology of treated samples was studied confirming the surface coating through carbon nanotubes. According to the results, the electrical resistance of treated wool with carbon nanotubes reduced substantially. However, the single‐walled carbon nanotubes are more useful to increase the conductivity. In addition, the wool color changed into gray after the treatment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polyurethane/conducting carbon black composites: Structure,electric conductivity,strain recovery behavior,and their relationships

The polyurethane composites with conducting carbon black (CB) were prepared by a solution‐precipitation process, which was followed by melt compression molding. The polyurethane used has good shape memory effect. The morphology of CB fillers in polyurethane matrix and the resulting conductivity of the composites were investigated. It has been found that CB fillers exist in the forms of aggregates. The percolation threshold is achieved at the CB concentration of 20 wt %. The presence of CB fillers decreases the degree of crystallinity of polycaprolactone (PCL) soft segments of the polyurethane. However, the composites still have enough soft‐segment crystals of polyurethane to fulfil the necessary condition for the shape memory properties. Dynamic mechanical data show that CB is an effective filler for the reinforcement of the polyurethane matrix, but does not deteriorate the stable physical cross‐link structure of the polyurethane, which is necessary to store the elastic energy in the service process of the shape memory materials. Addition of CB reinforcement in the polyurethane has influenced the strain recovery properties, especially for those samples with CB concentrations above the percolation threshold. The response temperature of the shape memory effect T_r has not been affected too much. Strain fixation S_f, which expresses the ability of the specimens to fix their strain, has been improved in the presence of the CB fillers. The final recovery rates R_f and strain recovery speeds V_r of the shape memory measurements, however, have decreased evidently. It is expectedly ascribed to the increased bulk viscosity as well as the impeding effect of the inter‐connective structure of CB fillers in the polymer matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 68–77, 2000     

Morphology,thermal expansion,and electrical conductivity of multiwalled carbon nanotube/epoxy composites

Multiwalled carbon nanotube/epoxy composites loaded with up to 0.5 wt % multiwalled carbon nanotubes were prepared and characterized. Infrared microscopy, scanning electron microscopy, thermogravimetry, differential scanning calorimetry, thermomechanical analysis, and electrical conductivity measurements of the composites were performed. Infrared microscopy and scanning electron microscopy images showed that the debundled nanotubes were well dispersed. The thermal expansion coefficients, before and after the glass transition, remained approximately constant with the addition of nanotubes, whereas the electrical conductivity at room temperature increased approximately 5 orders of magnitude. This result was attributed to the thermal expansion coefficients of the intertube gap on the carbon nanotube bundles, which were in the same range as that of the epoxy resin. Therefore, nanocomposites capable of electrostatic dissipation can be processed as neat epoxy materials with respect to the volume changes with temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photoisomerization of electroactive polyimide/multiwalled carbon nanotube composites on the effect of electrochemical sensing for ascorbic acid

We present the first investigation of photoisomerization of the azo‐based electroactive polyimide (PI)/amino‐functionalized multiwalled carbon nanotube (MWCNT) composite electrode on the effect of electrochemical sensing for ascorbic acid (AA). First, MWCNTs were grafted with 4‐aminobenzoic acid in a medium of polyphosphoric acid/phosphorous pentoxide to obtain MWCNTs functionalized with 4‐aminobenzoyl groups (AF‐MWCNTs). Subsequently, photoactive and electroactive PI/AF‐MWCNT composites (PEPACCs) were prepared by introducing pendant conjugated oligoaniline (amino‐capped aniline trimer) in the main chain and azobenzene chromophores in the side chain, in the presence of AF‐MWCNTs. Photoactive and electroactive PI (PEPI) and PEPACCs were characterized by ¹H NMR spectra, UV?visible absorption spectra, cyclic voltammetry (CV) and transmission electron microscopy. The CV study shows that the PEPACCs have higher electroactivity than PEPI. The redox and reversible photoisomerization (i.e. cis ? trans) behavior of PEPACCs was analyzed by in situ monitoring through systematic studies of CV and UV?visible spectroscopy. The light of the UV lamp was 365 nm. It should be noted that the sensor constructed from a trans‐PEPACC‐modified carbon‐paste electrode (CPE) demonstrated a higher electrocatalytic activity by 2.75‐fold and 1.12‐fold towards the oxidation of AA compared with those constructed using a PEPI‐ and cis‐PEPACC‐modified CPE, respectively. The detection limit of the trans‐PEPACC‐modified electrode was 1.73‐fold and 1.70‐fold lower than that of PEPI‐ and cis‐PEPACC‐modified CPE. Moreover, the differential pulse voltammetry data showed that the trans‐PEPACC‐modified electrode had high electrochemical sensing ability for the determination of AA, dopamine and uric acid. © 2014 Society of Chemical Industry