Preparation and Characterization of Linear Low Density Polyethylene/Carbon Nanotube Nanocomposites

Linear low‐density polyethylene (LLDPE)/multiwalled carbon nanotube (MWNT) nanocomposites were prepared via melt blending. The morphology and degree of dispersion of nanotubes in the polyethylene matrix were investigated using scanning electron microscopy (SEM). Both individual and agglomerates of MWNTs were evident. The rheological behavior and mechanical and electrical properties of the nanocomposites were studied using a capillary rheometer, tensile tester, and Tera ohm‐meter, respectively. Both polyethylene and its nanocomposites showed non‐Newtonian behavior in almost the whole range of shear rate. Addition of carbon nanotubes increased shear stress and shear viscosity. It was also found that the materials experience a fluid‐solid transition below 1 wt% MWNT. Flow activation energy for the nanocomposites was calculated using an Arrhenius type equation. With increasing nanotube content, the activation energy of flow increases. A decrease of about 7 orders of magnitude was obtained in surface and volume resistivity upon addition of 5 wt% MWNT. In addition, a difference between electrical and rheological percolation thresholds was observed. The results confirm the expected nucleant effect of nanotubes on the crystallization process of polyethylene. A slight increase in Young's modulus was also observed with increasing MWNT content.     

Preparation and Characterization of Poly(ethylene oxide)/Graphene Nanocomposites from an Aqueous Medium

The nanocomposite films of a functionalized graphene sheet (FGS) and poly(ethylene oxide) (PEO) were cast from the physical blend of an aqueous FGS dispersion assisted by sodium dodecyl sulfate and an aqueous PEO solution. The thermal properties observed by differential scanning calorimetry suggested that FGS had a nucleating effect on the PEO crystallization. However, we found FGS actually hindered the growth of PEO crystals. The dynamic mechanical properties indicated that FGS effectively reinforced the matrix PEO. The FGS also efficiently improved the electric conductivity of PEO. With the addition of 2 parts of FGS per 100 parts of PEO, the conductivity was increased by more than 10³-fold from that of pristine PEO.     

Preparation and Characterization of the Polyaniline Nanocomposites with Electricity/Magnetic Properties

Three kinds of magnetic particle (water-based NiZn ferrite fluid, water-based Fe₃O₄ magnetic fluid, and silicon-oil-based Fe₃O₄ magnetic fluid)/polyaniline nanocomposites were prepared in this study. The samples, after drying and grinding, were characterized by infrared spectrometry (IR), X-ray diffraction (XRD), and UV-vis, scanning electron microscope (SEM); their electromagnetic properties were also measured. The conductivitiy of the resulting water-based NiZn ferrite/polyaniline nanocomposites (WBNiZnFe/PA) was the greatest, reaching 0.094 s/cm, while the conductivitiy for water-based Fe₃O₄ magnetic particle/polyaniline nanocomposites (WBFe₃O₄/PA) was the lowest, reaching only 0.068 s/cm. The saturation magnetization for WBFe₃O₄/PA was the greatest, being 1.5 emu/g, while the saturation magnetization for WBNiZnFe/PA was the lowest, being only 0.8 emu/g. The coercivity of all magnetic particle/polyaniline nanocomposites was about He = 200 Oe.     

Structure and Mechanical Properties of 50/50 NR/SBR Blend/Pristine Clay Nanocomposites

A blend/clay nanocomposites of 50/50 (wt%) NR/SBR was prepared via mixing the latex of a 50/50 NR/SBR blend with an aqueous clay dispersion and co‐coagulating the mixture. The structure of the nanocomposite was characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Nanocomposites containing less than 10 phr clay showed a fully exfoliated structure. After increasing the clay content to 10 phr, both nonexfoliated (stacked layers) and exfoliated structures were observed in the nanocomposites. The results of mechanical tests showed that the nanocomposites presented better mechanical properties than clay‐free NR/SBR blend vulcanizate. Furthermore, tensile strength, tensile strain at break, and hardness (shore A) increased with increasing clay content, up to 6 phr, and then remained almost constant.     

Structure and Properties of Polypropylene/Polyolefin Elastomer/Organic Montmorillonite Nanocomposites

The crystallinity, mechanical properties, and thermal stability of polypropylene (PP)/organic montmorillonite (OMMT) and PP/polyolefin elastomer (POE)/OMMT composites, with polypropylene-g-maleic anhydride/styrene (PPMS) as a compatibilizer for both, were compared. The results showed that the strong interaction between the clay platelets and compatibilizer, which were generated by the maleic anhydride (MAH), improved the compatibility of the polymer matrices with the OMMT. A unique lamellar, flocculated structure of OMMT was formed after introduction of the POE. The highly dispersed clay layers could act as nucleating agents, resulting in smaller spherulites and higher crystallization temperatures. Compared with pure PP, the PP/OMMT nanocomposite showed enhanced mechanical properties and thermal stability; however, the PP/POE/OMMT had the best impact toughness.     

Preparation and Characterization of Montmorillonite/Polypyrrole Nanocomposites by In-Situ Chemical Polymerization

After prior ultrasonic treatment of montmorillorite (MMT), montmorillonite/polypyrrole (MMT/PPy) nanocomposites containing 10–80% PPy were prepared by in-situ chemical polymerization of pyrrole at 0°C in the presence of MMT in aqueous solution with FeCl₃ as oxidant and dopant. X-ray diffraction showed an increase in the interlayer spacing from 1.26 nm for MMT to 1.55 nm for MMT/PPy-10% and 1.96 nm for MMT/PPy-80%, signifying PPy was intercalated into the MMT galleries. Infrared spectra revealed the shifts of C-N stretching vibration and in-plane deformation bands, as well as the N-H vibration peaks of PPy, suggesting the presence of interfacial interactions between MMT and PPy. Scanning electron microscopy micrographs showed a flake-like morphology for the MMT/PPy nanocomposites and the obtained PPy retained this kind of morphology after removal of MMT from the composites by Hydrofluoric acid etching, while the pristine PPy prepared under the same condition exhibited globular particles. It was found for the first time that the conductivity of MMT/PPy with more than 50% PPy was higher than that of pristine PPy, i.e. 2.72 S/cm, 3.68 S/cm, and 4.81 S/cm for MMT/PPy containing 50%, 60%, and 80% PPy, while the pristine PPy conductivity was 2.71 S/cm. Thermal gravimetric analysis suggested that the introduction of MMT clay resulted in improvement of thermal stability for the obtained nanocomposites.     

Rheological and Mechanical Characterization of Multi-Walled Carbon Nanotubes/Polypropylene Nanocomposites

The rheology and morphology of multi-walled carbon nanotube (MWNT)/polypropylene (PP) nanocomposites prepared via melt blending was investigated. The minor phase content of MWNT varied between 0.25 and 8 wt%. From morphological studies using a scanning electron microscopy technique a good dispersion of carbon nanotubes in the PP matrix was observed. The rheological studies were performed by a capillary rheometer, and mechanical properties of the nanocomposites were studied using a tensile and flexural tester. Both PP and its nanocomposites showed non-Newtonian behavior. At low shear rates the addition of MWNT content causes an increase in viscosity; however, viscosity is less sensitive to addition of MWNT content at higher shear rates. Flow activation energy for the nanocomposites was calculated using an Arrhenius type equation. From this calculation it was concluded that the temperature sensitivity of nanocomposites was increased by increasing of nanotube content. An increase in tensile and flexural moduli and Izod impact strength was also observed by increasing the MWNT content. From rheological and mechanical tests it was concluded that the mechanical and rheological percolation threshold is at 1.5 wt%.     

Nonisothermal Crystallization Behaviors of Flame-Retardant Copolyester/Montmorillonite Nanocomposites

In order to obtain poly(ethylene terephthalate) (PET) engineering plastics with good flame retardancy, heat resistance, and mechanical properties, a novel phosphorus-containing copolyester (PET-co-DDP)/organo-montmorillonite (OMMT 1%) nanocomposite (PET-co-DDP/OMMT) was prepared by in situ intercalating polymerization. Nonisothermal crystallization kinetics and nanoscale morphology of this composite have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). Based on the results of the nonisothermal crystallization kinetics, the flame-retardant copolyester PET-co-DDP has a lower crystallization rate than pure PET, while PET-co-DDP/OMMT nanocomposite has a higher crystallization rate than pure PET. Based on the Augis and Bennett method, the activation energies for nonisothermal crystallization of pure PET, PET-co-DDP, and PET-co-DDP/OMMT nanocomposite were evaluated as 101, 138, and 76 kJ mol^?1, respectively. All the evidence shows that PET-co-DDP strongly influences the crystallization behavior because of its irregular chain structure, while the addition of nanoscale OMMT to this copolymer can significantly enhance the crystallization rate owing to its remarkable nucleating effect. An understanding of the above crystalline behaviors will be beneficial in preparing PET engineering plastics with good overall comprehensive performance.     

Preparation and Characterization of Polypyrrole/Ferrospinel Nanocomposite by W/O Microemulsion Pathway

A polypyrrole/ferrospinel(NiFe₂O₄) nanocomposite was prepared by the in situ chemical oxidizing of pyrrole in the presence of NiFe₂O₄ nanoparticles in water-in-oil (w/o) microemulsion. The structural, morphological, and magnetic properties of the as-prepared polypyrrole/NiFe₂O₄ nanocomposite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and magnetic measurements. XRD and FTIR revealed the presence of NiFe₂O₄ in the nanocomposite. SEM and TEM images illustrated that polypyrrole was coated on the NiFe₂O₄ surface. The electromagnetic parameters, such as conductivity, saturation magnetization, and coercivity of NiFe₂O₄ nanoparticles varied after coating with polypyrrole.     

Preparation and Characterization of Chemically Crosslinked Polyvinyl Alcohol/Carboxylated Nanocrystalline Cellulose Nanocomposite Hydrogel Films with High Mechanical Strength

Chemically crosslinked polyvinyl alcohol (PVA)/carboxylated nanocry-stalline cellulose (PVA/CNCC) nanocomposite hydrogel films were fabricated by film-casting of PVA/CNCC mixture solutions and subsequent thermal-curing of the PVA with the CNCC. Gel fractions of the hydrogel films were measured to confirm the occurrence of crosslinking. Morphologies of the hydrogel films were characterized by polarized light microscopy and scanning electron microscopy (SEM). Thermal properties, swelling behavior and mechanical properties of the hydrogel films were investigated to evaluate the influence of CNCC content (10～30% of PVA mass). Equilibrium water content of the hydrogel films was in the range of 40～49%. At swelling equilibrium, the hydrogel films could be stretched to 3～3.4 times their original length, and their tensile strength was in the range of 7.9～11.6 MPa. The results show that the PVA/CNCC nanocomposite hydrogel films were both extensible and highly tough.     

Preparation and Characterization of Grafted Natural Rubber/Graphene Oxide Nanocomposites

Vinyltriethoxysilane (VTES) was grafted onto natural rubber (NR) in latex form, using potassium persulfate (KPS) as initiator. The VTES grafted NR (NR-g-VTES) was then further reinforced with graphene oxide (GO) by a mechanical mixing method with different GO loadings to get the rubber composite (GO/NR-g-VTES). The NR-g-VTES was characterized and confirmed by attenuated total teflectance-Fourier transforms infrared spectroscopy (ATR-FTIR). The effect of GO content on the curing characteristics and resulting mechanical properties of the GO/NR-g-VTES were studied and compared with neat NR filled with GO (NR/GO). The maximum and minimum torque and the tensile and tear strength of the NR-g-VTES/GO composites were higher than that of NR/GO. The samples containing low GO concentration showed maximum torque and tensile and tear strength. Dynamic mechanical analysis showed that the interaction between GO and NR-g-VTES was better than that of the GO-reinforced NR.     

Nanocomposites Based on Aromatic Polyamide-Imide and Magnesium Hydrosilicate Nanotubes

Structure, morphology, and thermal properties of nanocomposites based on thermally stable poly(diphenyloxydamide-N-phenylphtalimide) (PAI) and layered magnesium hydrosilicate nanotubes (NTs) were studied using thermogravimetric analysis, dynamic mechanical analysis, atomic force microscopy, and differential scanning calorimetry. Thermal stability and glass transition temperature of the composites were shown to exceed those of the PAI matrix. Introduction of NT into the polymer matrix appreciably increased the elasticity and deformability of the composite material. The content of NT was also shown to greatly influence the surface morphology of the PAI-NT composites.     

Microstructure and Properties of Polypropylene/Clay Nanocomposites

Nanocomposites of polypropylene (PP) containing various contents of Cloisite 15A nanoclay particles were prepared by one-step melt compounding in a twin screw extruder. Tensile and impact properties of the nanocomposite systems were investigated and correlated with their microstructures. The tensile modulus increased with an increase in Cloisite 15A content but the tensile strength, elongation at break, and impact strength were decreased. WAXS and TEM studies showed almost exfoliated structures. There was a decrease in permeability values with an increase in nanoclay content up to 5 wt. %. Exceeding this content of nanoclay had no significant effect on permeation due to the aggregation phenomenon at high concentrations of the nanoparticles. Most of the examined micromechanical models for prediction of the tensile modulus of the nanocomposite were successful despite being based on fiber-shaped fillers. An exfoliated structure of clay within the nanocomposite was assumed for the modeling using a molecular dynamics simulations approach, employing Dreiding, Forcite, and COMPASS force fields, in order to investigate the best one for a successful estimation of elastic modulus. Relative to the experimental modulus values of the nanocomposites, which were around 1100–1200 MPa, the COMPASS force field had the best correlation with the values with a slight departure of about 10%.     

Preparation of Silicon Carbide Nanoparticle/Butadiene Rubber/Silane Nanocomposites; Structural,Mechanical, Tribological and Thermal Properties

Silicon carbide nanoparticles (nano-SiC), in the amounts of 0, 3, and 5 parts per hundred of rubber (phr), were employed in a butadiene rubber (BR) based compound as a potential commercial rubber and the structure, mechanical, tribological and thermal properties of the samples were investigated. The use of 3 phr of nano-SiC, especially in the presence of silane, increased the crosslink density and improved the tensile strength (35%) and elongation at break (64%) of the BR. In addition; the abrasion resistance of the BR was improved about 120% and the coefficient of friction increased. Scanning electron microscopy (SEM) images revealed the use of silane resulted in an appropriate dispersion of the nano-SiC and improvement of its interaction with the matrix. The use of nano-SiC, especially with silane, increased the initial thermal decomposition temperature of the BR and decreased its rate of degradation.     

Characteristics of Rubber/Sodium Montmorillonite Nanocomposites Prepared by a Novel Method

In order to enhance the fine dispersion of hydrophilic sodium montmorillonite (Na‐MMT) in the matrix of hydrophobic rubber, the hydrophobic modification of Na‐MMT was carried out via an in situ method in the melt compounding process using the modifiers poly(ethylene glycol) monooleate or poly(ethylene glycol) diacrylate, both of which have a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic hydrocarbon segment. The X‐ray diffraction patterns showed that the interlayer distance of Na‐MMT was expanded by the intercalation of these modifiers. The morphology observed by scanning electron microscopy as well as the cure characteristics and tensile modulus showed that this organic modification effectively enhanced the fine dispersion of Na‐MMT in the rubber matrix.     

Thermal,Mechanical, and Rheological Characterization of Polylactic Acid/Halloysite Nanotube Nanocomposites

Halloysite nanotube (HNT) clay and biodegradable polylactic acid (PLA) nanocomposites were fabricated by a melt-blending method with five different clay levels (1, 3, 5, 7, and 9 wt%). The effect of HNT loading on the thermal and mechanical properties of the PLA/HNT nanocomposites was examined by thermogravimetric analysis and universal tensile testing, respectively. Morphological characteristics were investigated by transmission electron microscopy. The composites' melt rheological characteristic analyses were conducted using a rotational rheometer in both steady-shear and oscillatory dynamic testing modes. The data were found to be well-analyzed using the Carreau model, Cox–Merz rule, modified Cole–Cole plot, and van Gurp–Palmen plot.     

Preparation and Properties of FeNi-Mg/MgO Nanocomposite

The FeNi-Mg/MgO nanocomposite synthesized by spark erosion of pure Mg and Fe₇₀Ni₃₀ electrodes was investigated by X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. From the X-ray diffraction measurements Mg, MgO, and -FeNi were recognized. According to the Mössbauer spectra analysis, iron atoms were identified in -FeNi, Fe_1-x O, and FeNi in Mg/MgO phases. The FeNi in Mg/MgO phase consists of fcc -FeNi phase which is antiferromagnetic below T _N 40 K and weakly ferromagnetic bcc -FeNi clusters. The magnetic measurements confirmed the presence of the -FeNi phase and the composite model in the form of isolated magnetic particles in Mg/MgO matrix.     

Preparation and Properties of Polypropylene/Organo-Vermiculite Nanocomposites

Polypropylene/organo-vermiculite (OVMT) nanocomposites with different clay loadings were prepared via melt-mixing using a twin-screw extruder. The vermiculite was premodified with maleic anhydride by ball milling. The resultant polypropylene/OVMT nanocomposites possess an intercalated structure as confirmed by both wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The mechanical property tests show that the tensile and flexural strength of these nanocomposites increase dramatically with the OVMT loading; the fracture toughness remains almost unchanged and the Charpy impact strength decreases slightly. Finally, differential scanning calorimetry (DSC) and WAXD results show that the addition of vermiculite can induce the β crystal structure of polypropylene.     

Preparation and Thermal Characterization of Three Different Series of Novel Polyhedral Oligomeric Silsesquioxanes/Polystyrene Nanocomposites

The resistance to the thermal degradation of some polystyrene (PS)-based nanocomposites, loaded with 5% w/w of one of nine novel polyhedral oligomeric silsesquioxanes (POSSs) of general formula R₇R’(SiO_1.5)₈, where R = isobutyl, cyclopentyl, or phenyl and R’ = -(CH₂)₅-CH₃, -(CH₂)₇-CH₃, or -(CH₂)₉-CH₃, was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Nanocomposites were prepared by in situ polymerization of styrene in the presence of the appropriate POSS and were characterized by differential scanning calorimetry, to determine the glass transition temperature (T_g), and by nuclear magnetic resonance spectroscopy, to determine the actual filler content which, in all cases, was slightly higher than in the starting mixtures. Nanocomposites were degraded in a thermobalance, in both selected atmospheres, in the 25–700°C temperature range with the formation of small quantities of solid residue at 700°C. The temperatures of 5% mass loss (T_5%) were determined to evaluate the resistance to the thermal degradation; the results were higher than for PS. The data obtained were then compared with each other in order to verify if and how much the nature of R and R’ can influence the thermal stability of the corresponding nanocomposites.     

Size-Dependent HCl Generation of PVC/SiO2 Micro- and Nanocomposites

In this study HCl generation of polyvinyl (chloride) (PVC)/SiO₂ composites during its combustion was investigated. SiO₂ with different particle sizes were used as HCl absorbers and their HCl uptake ability results were compared to that of CaCO₃. It was found that the amount of released HCl gas during PVC combustion decreased in the presence of SiO₂. The HCl uptake ability of SiO₂ improved with decreasing of its particle size. Although thermogravimetric analysis (TGA) results showed that SiO₂ particles decreased the first thermal degradation temperature (T _onset) of PVC by initiating dehydrochlorination of PVC at lower temperatures, SiO₂ particles had more effective HCl uptaking ability than that of CaCO₃. Scanning electron microscopy (SEM) micrographs showed that some aggregates whose size was less than 100 nm were formed when Si-25 nm was used as filler. When SiO₂ with micron size was added to PVC as filler, more uniform and better distribution of the SiO₂ on the surface was observed.