Multiwalled carbon nanotubes‐reinforced isotactic polypropylene nanocomposites: Enhancement of crystallization and mechanical,thermal, and electrical properties

Multiwalled carbon nanotubes (MWCNTs)‐reinforced isotactic polypropylene (iPP) nanocomposites with low‐content of MWCNTs were fabricated using the melt‐cast techniques. The reinforced plastics were characterized by X‐ray diffraction (XRD) measurements, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical test, differential thermal analyses (DTA), and electrical tests. XRD studies exhibit the α‐crystal in the injection‐molded neat iPP with lamellar stacks having a long period of 150Å. Both the intensity of lamellar reflection and the thickness of long period increase with increasing the MWCNTs contents, indicating an enhancement of iPP crystallization by MWCNTs addition. This increase of lamellar thickness is analyzed to be consistent with that evaluated by DTA. SEM micrographs display larger MWCNTs aggregates with increasing amount of reinforcements and show a good adhesion between nanoparticles and iPP matrix. FTIR spectra reveal distinct chemical textures for the samples and confirm the existence of α‐crystal. Mechanical strengths, electrical conductivity, and dielectric constants are found to increase with increasing MWCNTs content, representing an improved performance of the nanocomposites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Influence of silanized low‐dimensional carbon nanofillers on mechanical,thermomechanical, and crystallization behaviors of poly(L‐lactic acid) composites—A comparative study

Composites were investigated regarding the comparison of multi‐walled carbon nanotubes (MWCNTs) with exfoliated graphene(EG) in poly(L‐lactic acid) (PLLA) and the effect of silane‐treated carbon nanofillers on properties of PLLA composites. Solution blending method was used to prepare PLLA composites at a filler content of 0.5 wt %. Fourier transform infrared spectroscopy and X‐ray photoelectron spectra results indicated the attachment of silane molecules on the surface of these nanofillers. It was found that the addition of these nanofillers greatly enhanced the mechanical, thermomechanical, and crystallization behaviors of PLLA due to the heterogeneous nucleation effect. Moreover, the silane‐treated fillers further enhanced the breaking elongation moderately (although the materials are still brittle), modulus and thermal property of the nanocomposites, without sacrificing the tensile strength, compared with the pristine nanocomposites. On the other hand, composites reinforced with MWCNTs and EG perform almost the same mechanical property. And EG outperformed MWCNTs in thermomechanical properties of composites when being used as the reinforcement of PLLA. Conversely, composites reinforced with MWCNTs showed better crystallization properties than those reinforced with EG. Interestingly, no significant changes were observed for the crystallization properties of PLLA composites when MWCNTs and EG had been treated by silane coupling agent. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1194‐1202, 2013     

Polypropylene‐based composites containing sorbitol‐based nucleating agent and siloxane‐silsesquioxane resin

Composites based on isotactic polypropylene (iPP) modified with a sorbitol derivative (NX8000) and siloxane‐silsesquioxane resin containing reactive phenyl groups (SiOPh) were prepared by melt extrusion. These iPP‐based formulations were investigated to evaluate the influence of such additives on the crystallization behavior and morphology, as well as on thermal and mechanical properties. The addition of sorbitol fastens crystallization kinetics of iPP and leads to higher transparency of iPP films. Upon the incorporation of siloxane‐silsesquioxane resin, no further effect on iPP crystallization kinetics is evidenced by calorimetry, optical microscopy, and X‐ray diffraction analysis. Transparency of iPP‐based composites is improved upon the addition of sorbitol, but decreased when SiOPh is added to the formulation. The composites are also stiffer, compared to neat polypropylene with a decreased elongation at break and increased Young's modulus values, with increasing amounts of fillers. The effect of the siloxane‐silsesquioxane resin on properties of iPP/NX8000/SiOPh composites was explained taking into account compatibility of the components and morphology of the composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43476.     

Preparation and characterization of nylon610/functionalized multiwalled carbon nanotubes composites

Nylon610 nanocomposites containing functionalized multiwalled carbon nanotubes (MWCNTs) were prepared using wet melt blending method, which is a novel preparation technique. In comparison with the pure nylon610, the elastic modulus, tensile strength, bending modulus, and bending strength of the composites increase significantly with the increase of MWCNTs content, and the mechanical properties of the composites are also improved significantly by adding a small amount of MWCNTs (0.1 wt %). The crystallization peak of the composites shifts to higher temperature with the addition of MWCNTs, and among the two melting peaks, the intensity of melting peak at low temperature decreases with increasing MWCNTs content. The composites are more stable than pure PA610 and decompose at higher temperature, suggesting that the accession of MWCNTs can improve the composites' thermal stability. The storage modulus of the composites decreases with the temperature increasing, but under lower temperature it increases significantly with the addition of MWCNTs–COOH except for PANT‐0.1 sample. Transmission electron microscope (TEM) images of composites exhibit that the wet melt blending technique can avoid the excess agglomeration of MWCNTs under vacuum dryness, which benefits MWCNTs to disperse uniformly in matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of multiwall carbon nanotube/waterborne polyurethane nanocomposites

The preparation of thermoplastic nanocomposites of waterborne polyurethane (WBPU) and multiwall carbon nanotubes (MWCNTs) via an in situ polymerization approach is presented. The effects of the presence and content of MWCNTs on the morphology and thermal, mechanical and electrical properties of the nanocomposites were investigated. Carbon nanotubes were modified with amide groups in order to enhance their chemical affinity towards WBPU. Thermogravimetric studies show enhanced thermal stability of the nanocomposites. Scanning and transmission electronic microscopy images prove that functionalized carbon nanotubes can be effectively dispersed in WBPU matrix. Mechanical properties reveal that Young's modulus and tensile strength tend to increase when appropriate amounts of MWCNTs are loaded due to the reinforcing effect of the functionalized carbon nanotubes. Thermal properties show an increase in the glass transition temperature and storage modulus with an increase in MWCNT content. X‐ray diffraction reveals better crystallization of the WBPU in the presence of MWCNTs. The WBPU/MWCNT nanocomposite film containing 1 wt% of MWCNTs exhibits a conductivity nearly five orders of magnitude higher than that of WBPU film. © 2017 Society of Chemical Industry     

Special morphology and its role in mechanical enhancement of linear low‐density polyethylene/multiwalled carbon nanotubes composites

In this work, multiwalled carbon nanotubes (MWCNTs), as reinforcing agent, were blended with linear low‐density polyethylene (LLDPE), then molded by hot compression molding to prepare LLDPE/MWCNTs composites. Tensile tests indicate that the strength, Young's modulus, and toughness are all improved for LLDPE/MWCNTs composites containing 1 and 3 wt % MWCNTs. Compared with LLDPE, the Young's modulus of LLDPE/MWCNTs composites rises from 144.8 to 270.8 MPa at 1 wt % MWCNTs content. At the same time, increases of 18.5% in tensile strength and 16.6% in yield strength are achieved. Additionally, its toughness is enhanced by 26.7% than that of LLDPE. Microstructure characterizations, including differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy were performed to investigate the variations of microstructure and further to establish the relationship between microstructure and mechanical properties. Homogeneous dispersion of MWCNTs, network formation, and development of an oriented nanohybrid shish‐kebab structure contribute to the enhanced strength and toughness. The increased crystallinity is beneficial to the reinforcement and increased modulus. Additionally, the thermal stability of the LLDPE/MWCNTs composites is enhanced as well. This work suggests a promising routine to optimize polymer/MWCNTs composites by tailoring the structural development. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45525.     

Thermal stability and crystallization kinetics of isotactic polypropylene/organomontmorillonite nanocomposites

The thermal stability and crystallization kinetics of isotactic polypropylene (iPP) and iPP/organomontmorillonite (organo‐MMT) nanocomposites were investigated with differential scanning calorimetry and thermogravimetry. The incorporation of organo‐MMT up to a concentration of 4 wt % did not affect the melting temperature of iPP but did increase the peak thermal degradation temperature by 60°C. The isothermal crystallization kinetics showed that the addition of organo‐MMT increased the crystallization rate of iPP but reduced the isothermal Avrami exponent. The crystallization temperature of the nanocomposites measured with nonisothermal crystallization was higher than that of plain iPP, and this indicated an enhanced crystallization rate. The nonisothermal Avrami exponent, like the isothermal exponent, decreased with the addition of organo‐MMT, and this suggested changes in the crystallite growth geometry. Subsequently, the tensile yield strength and the tensile modulus both increased, but the elongation at break and the notched Izod impact strength did not change significantly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3404–3415, 2003     

Investigation of electrical,mechanical, and thermal properties of functionalized multiwalled carbon nanotubes‐reduced graphene Oxide/PMMA hybrid nanocomposites

Electrical, mechanical, and thermal properties of the poly(methyl methacrylate) (PMMA) composites containing functionalized multiwalled carbon nanotubes (f‐MWCNTs) and reduced graphene oxide (rGO) hybrid nanofillers have been investigated. The observed electrical percolation threshold of FHC is 0.8 wt% with maximum conductivity of 1.21 × 10^?3 S/cm at 4 wt% of f‐MWCNTs. The electrical transport mechanism and magneto resistance studied of hybrid composites have also been investigated. Progressive addition of f‐MWCNTs in rGO/PMMA composite results increase in mechanical (tensile strength and Young's modulus) and thermal (thermal stability) properties of f‐MWCNTs‐rGO/PMMA hybrid nanocomposites (FHC). The increased mechanical properties are due to the efficient load transfer from PMMA matrix to f‐MWCNTs and rGO through better chemical interaction. The strong interaction between PMMA and f‐MWCNTs‐rGO in FHC is the main cause for improved thermal stability. POLYM. ENG. SCI., 59:1075–1083, 2019. © 2019 Society of Plastics Engineers     

Effect of in situ surface‐modified nano‐SiO2 on the thermal and mechanical properties and crystallization behavior of nylon 1010

Nylon 1010 composites filled with two types of surface‐modified SiO₂ nanoparticles (RNS and DNS) were prepared by melt blending. The mechanical properties of the composites were evaluated. The influences of the surface‐modified nano‐SiO₂ on the thermal stability, crystallization behavior, and microstructure of nylon 1010 were investigated by thermogravimetric analysis, differential scanning calorimetry (DSC), X‐ray diffraction, and transmission electron microscopy. And the interfacial interactions between the fillers and polymer matrix were examined using a Fourier transformation infrared spectrometer. It was found that the addition of the surface‐modified nano‐SiO₂ had distinct influences on the thermal stability, mechanical properties, and crystallization behavior of nylon 1010. RNS and DNS as the fillers had different effects on the mechanical properties of nylon 1010. The composites filled with RNS at a mass fraction of 1–5% showed increased break elongation, Young's modulus, and impact strength but almost unchanged or even slightly lowered tensile strength than the unfilled matrix. The DNS‐filled nylon 1010 composites had obviously decreased tensile strength, whereas the incorporation of DNS also contributed to the increase in the Young's modulus of nylon 1010, but less effective than RNS. Moreover, the nylon 1010 composites had better thermal stability than the neat polymer matrix, and the composites filled with RNS were more thermally stable than those filled with DNS. The difference in the crystallinity of neat nylon 1010 and its composites filled with RNS and DNS was subtle, although the surface‐modified nano‐SiO₂ could induce or/and stabilize the γ‐crystalline formation of nylon 1010. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of fly ash cenospheres on performance of coir fiber‐reinforced recycled high‐density polyethylene biocomposites

Recycled high‐density polyethylene (RHDPE)/coir fiber (CF)‐reinforced biocomposites were fabricated using melt blending technique in a twin‐screw extruder and the test specimens were prepared in an automatic injection molding machine. Variation in mechanical properties, crystallization behavior, water absorption, and thermal stability with the addition of fly ash cenospheres (FACS) in RHDPE/CF composites were investigated. It was observed that the tensile modulus, flexural strength, flexural modulus, and hardness properties of RHDPE increase with an increase in fiber loading from 10 to 30 wt %. Composites prepared using 30 wt % CF and 1 wt % MA‐g‐HDPE exhibited optimum mechanical performance with an increase in tensile modulus to 217%, flexural strength to 30%, flexural modulus to 97%, and hardness to 27% when compared with the RHDPE matrix. Addition of FACS results in a significant increase in the flexural modulus and hardness of the RHDPE/CF composites. Dynamic mechanical analysis tests of the RHDPE/CF/FACS biocomposites in presence of MA‐g‐HDPE revealed an increase in storage (E′) and loss (E″) modulus with reduction in damping factor (tan δ), confirming a strong influence between the fiber/FACS and MA‐g‐HDPE in the RHDPE matrix. Differential scanning calorimetry, thermogravimetric analysis thermograms also showed improved thermal properties in the composites when compared with RHDPE matrix. The main motivation of this study was to prepare a value added and low‐cost composite material with optimum properties from consumer and industrial wastes as matrix and filler. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42237.     

Efficient functionalization of multi‐walled carbon nanotubes with p‐aminophenol and their application in the fabrication of poly(amide‐imide)‐matrix composites

The ultrasonically assisted preparation and characterization of poly(amide‐imide) (PAI) composites containing functionalized multi‐walled carbon nanotubes (MWCNTs) are reported. To improve the dispersion in and compatibility with the polymer matrix, the MWCNTs were surface‐modified with p‐aminophenol (p‐AP) under microwave irradiation. The process is fast, one‐pot, easy and results in a high degree of functionalization as well as dispersibility in organic solvents. The p‐AP‐functionalized MWCNTs (MWCNTs‐AP) were analysed by means of field emission and transmission electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction and thermogravimetric analysis (TGA). The results consistently confirm the formation of p‐AP functionalities on MWCNTs which are able to undergo additional reactions, while the structure of the MWCNTs remains relatively intact. MWCNTs‐AP/PAI hybrid films were prepared with various MWCNTs‐AP contents (5–15 wt%) using a solution‐casting technique. Microscopic observations show that the dispersion of the MWCNTs‐AP is improved as a result of the organic groups on the MWCNT surface and functional groups in the PAI structure. The properties of the obtained composites were characterized extensively using the aforementioned techniques. TGA results show that the hybrid films exhibit a good thermal stability. Tensile mechanical testing was performed for the prepared composites, the results of which indicate an increase in the elastic modulus and tensile strength with increasing MWCNTs‐AP content. © 2013 Society of Chemical Industry     

Effect of TMB-5 on dispersion of MWCNTs in iPP and crystallization of β-nucleated iPP/MWCNTs composites

In this work, multiwall-carbon-nanotubes (MWCNTs), β nucleating agent(TMB-5) and isotactic polypropylene(iPP) were mixed to prepare MWCNTs/iPP composites, which were processed by a corotating twin screw extruder at 270 °C. MWCNTs at 0 wt%, 0.05 wt%, 0.3 wt%, 1 wt%, 2 wt% and 3 wt% were added into the composites respectively and the concentration of TMB-5 was 0.3 wt% consistently. Polarized light microscopy (POM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and Wide-angle X-ray diffraction (WAXD) were used to study the dispersion of MWCNTs in the β-Nucleated iPP and the crystallization of the composites. SEM and TEM graphs showed that MWCNTs dispersed individually in the iPP matrix when TMB-5 was added in the composites. In the contrast, there were many aggregates of MWCNTs in iPP matrix without TMB-5. DSC and WAXD results indicate that TMB-5 and individual MWCNTs have a synergistic effect on inducing the formation of β crystals. However, with the content of MWCNTs increasing in the composites, β crystal content decreased and α crystal content increased, which indicated that MWCNTs aggregating in the iPP matrix acted as α nucleating agent restricting the formation of β crystals and the effect of TMB-5 on dispersion became limited at a relatively high MWCNTs content.     

Combined effect of organic phosphate sodium and nanoclay on the mechanical properties and crystallization behavior of isotactic polypropylene

Combined effect of α‐nucleating agent (NA) sodium 2,2′‐methylene‐bis(4,6‐di‐tert‐butylphenyl) phosphate (NA11) and nanoclay (NC) on the mechanical properties and crystallization behavior of isotactic polypropylene (iPP) was investigated by mechanical testing, wide‐angle X‐ray scattering (WAXD), differential scanning calorimetry (DSC), polarized optical microscopy (POM), and scanning electron microscopy (SEM). The mechanical testing results indicated that the separate addition of NA11 and NC only increased the stiffness of iPP while the combined addition of NA11, NC, and maleic anhydride grafted polypropylene (PP‐g‐MA) simultaneously improved stiffness and toughness of iPP. Compared to pure iPP, the tensile strength, the flexural modulus, and impact strength of iPP composites increased 9.7, 38.6, and 42.9%, respectively. The result indicated good synergistic effects of NC, NA11, and PP‐g‐MA in improving iPP mechanical properties. WAXD patterns revealed NA11, and NC only induced the α‐crystals of iPP. SEM micrograph showed that the PP‐g‐MA could effectively improve the dispersing of NC in iPP. Finally, the nonisothermal crystallization kinetics of neat iPP and PP nanocomposites was described by Caze method. The result indicated that the addition of NA overcame the shortcoming of low crystallization rate of NC nanocomposites and maintained the excellent mechanical properties, which is another highlight of the combined addition of NAs and nanoclay. Meanwhile, the result showed that nuclei formation and spherulite growth of iPP were affected by the presence of NA and nanoclay. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Rapid and low temperature spark plasma sintering synthesis of novel carbon nanotube reinforced titanium matrix composites

Multi–walled carbon nanotube (MWCNT) reinforced titanium matrix composites were synthesized using a spark plasma sintering method at a low sintering temperature of 550 °C. The effects of the weight fraction of MWCNTs on the microstructures and the mechanical and thermal properties of the composites were investigated. No reaction products were detected in the composites, indicating that the MWCNTs in the composites maintained their structural integrity after sintering, and thus, because of their advantageous properties, could reinforce the titanium matrix. As a result, the compressive strength of the composite containing 0.4 wt.% MWCNTs reached 1106 MPa, which was an increase of 61.5% compared to that of pure titanium under at the same conditions. In addition, the results revealed that compressive strength of the bulk compacts increased initially and then decreased with an increase in weight fraction of MWCNTs. However, compressive strain of the sintered composites continued to fall at a slow rate. The microhardness and thermal diffusivity of the composites rose steadily with an increasing content of MWCNTs. When the weight fraction of MWCNTs in the composites exceeded 0.8%, the compressive strength of the composites declined significantly due to the increasing aggregation of the MWCNTs.     

Influence of organically modified nanoclay on the performance of pineapple leaf fiber‐reinforced polypropylene nanocomposites

Polypropylene/Pine apple leaf fiber (PP/PALF)‐reinforced nanocomposites were fabricated using melt blending technique in a twin‐screw extruder (Haake Rheocord 9000). Variation in mechanical properties, crystallization behavior, water absorption, and thermal stability with the addition of nanoclay in PP/PALF composites were investigated. It was observed that the tensile, flexural, and impact properties of PP increase with the increase in fiber loading from 10 to 30 wt %. Composites prepared using 30 wt % PALF and 5 wt % MA‐g‐PP exhibited optimum mechanical performance with an increase in tensile strength to 31%, flexural strength to 45% when compared with virgin PP. Addition of nanoclay results in a further increase in tensile and flexural strength of PP/PALF composites to 20 and 24.3%, which shows intercalated morphology. However, addition of nanoclay does not show any substantial increase in impact strength when compared with PP/PALF composites. Dynamic mechanical analysis tests revealed an increase in storage modulus (E′) and damping factor (tan δ), confirming a strong influence between the fiber/nanoclay and MA‐g‐PP. Differential scanning calorimetry, thermogravimetric analysis thermograms also showed improved thermal properties when compared with the virgin matrix. TEM micrographs also showed few layers of agglomerated clay galleries along with mixed nanomorphology in the nanocomposites. Wide angle X‐ray diffraction studies indicated an increase in d‐spacing from 22.4 Å in Cloisite 20A to 40.1 Å in PP/PALF nanocomposite because of improved intercalated morphology. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Noncovalent functionalization of carbon nanotubes using branched random copolymer for improvement of thermal conductivity and mechanical properties of epoxy thermosets

A branched random copolymer, poly[(hydroxyethyl acrylate)‐r‐(N‐vinylcarbazole)] (BPHNV), was synthesized through a facile one‐pot free radical polymerization with hydroxyethyl acrylate and N‐vinylcarbazole monomers, using 4‐vinylmethylmercaptan as the chain transfer agent. BPHNV was employed to noncovalently modify multiwall carbon nanotubes (MWCNTs) by π–π interaction. The as‐modified MWCNTs were then incorporated into epoxy resin to improve the thermal conductivity and mechanical properties of epoxy thermosets. The results suggest that, due to both the conjugation structure and the epoxy‐philic component, BPHNV could form a polymer layer on the wall of MWCNTs and inhibit entanglement, helping the uniform dispersion of MWCNTs in epoxy matrix. Owing to the unprecedented thermal conductivity of MWCNTs and the enhancement in the interfacial interaction between fillers and matrix, the thermal conductivity of epoxy/MWCNTs/BPHNV composites increases by 78% at extremely low filler loadings, while the electrical resistivity is still maintained on account of the insulating polymer layer. Meanwhile, the mechanical properties and glass transition temperature (T_g) of the thermosets are elevated effectively, with no significant decrease occurring to the modulus. The addition of as little as 0.1 wt% of MWCNTs decorated with 1.0 wt% of BPHNV to an epoxy matrix affords a great increase of 130% in impact strength for the epoxy thermosets, as well as an increase of over 13 °C in T_g. © 2018 Society of Chemical Industry     

Preparation and characterization of multi‐walled carbon nanotube/poly(ethylene terephthalate) nanoweb

Multi‐walled carbon nanotube (MWCNT)/Poly(ethylene terephthalate) (PET) nanowebs were obtained by electrospinning. For uniform dispersion of MWCNTs in PET solution, MWCNTs were functionalized by acid treatment. Introduction of carboxyl groups onto the surface of MWCNTs was examined by Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD) analysis. MWCNTs were added into 22 wt % PET solution in the ratio of 1, 2, 3 wt % to PET. The morphology of MWCNT/PET nanoweb was observed using field emission‐scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM). The nanofiber diameter decreased with increasing MWCNT concentration. The distribution of the nanofiber diameters showed a bi‐modal shape when MWCNTs were added. Thermal and tensile properties of electrospun MWCNT/PET nanowebs were examined using a differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), dynamic mechanical analyzer (DMA) and etc. Tensile strength, tensile modulus, thermal stability, and the degree of crystallinity increased with increasing MWCNT concentration. In contrast, elongation at break and cold crystallization temperature showed a contrary tendency. Electric conductivities of the MWCNT/PET nanowebs were in the electrostatic dissipation range. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigation on the use of coir fiber as alternative reinforcement in polypropylene

Polypropylene/coir fiber composites were prepared according to an experimental statistical design, in which the independent variables, coir fiber, and compatibilizer content, were varied. The compatibilizer used was maleic anhydride grafted polypropylene (PP‐g‐MA). Compatibilizer free composites were also prepared. Composites were processed in a corotating twin‐screw extruder and submitted to mechanical and morphological analyses. The effects of the independent variables on the mechanical properties were assessed through tensile strength, elongation at break, flexural modulus, and impact strength. The morphological properties were assessed by scanning electron microscopy (SEM). The results indicated the need for using compatibilizers in the composites due to the incompatibility of PP and coir fiber. The variable with the strongest effect on the properties was coir content, whose increase caused increase in tensile strength, impact strength and elastic modulus, and decrease in elongation at break. The presence of PP‐g‐MA was fundamental to achieving the aforementioned results. The effect of increasing compatibilizer content was only observed for the elastic modulus. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of polyurethane/multiwalled carbon nanotube nanocomposites by a spray drying process

A spray drying approach has been used to prepare polyurethane/multiwalled carbon nanotube (PU/MWCNT) composites. By using this method, the MWCNTs can be dispersed homogeneously in the PU matrix in an attempt to improve the mechanical properties of the nanocomposites. The morphology of the resulting PU/MWCNT composites was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM observations illustrate that the MWCNTs are dispersed finely and uniformly in the PU matrix. X‐ray diffraction results indicate that the microphase separation structure of the PU is slightly affected by the presence of the MWCNTs. The mechanical properties such as tensile strength, tensile modulus, elongation at break, and hardness of the nanocomposites were studied. The electrical and the thermal conductivity of the nanocomposites were also evaluated. The results show that both the electrical and the thermal conductivity increase with the increase of MWCNT loading. In addition, the percolation threshold value of the PU composites is significantly reduced to about 5 wt % because of the high aspect ratio of carbon nanotubes and exclusive effect of latex particles of PU emulsion in dispersion. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012