Preparation and thermal properties of resole‐type phenol resin–clay nanocomposites

Resole‐type phenol resin–clay nanocomposites have been prepared successfully by melt compounding phenol resin with organophilic clay. In the resulting phenol resin–clay nanocomposite, the silicate layers of the clay were exfoliated and dispersed as monolayers. The nanocomposite exhibited higher long‐term heat resistance when compared with unmodified phenol resin. It was surmised that the silicate layers of the clay acted as barriers to oxygen penetration into the resin, as the degree of heat degradation of the nanocomposite was much lower than that of the straight phenol resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3236–3240, 2006     

Enhanced wear performance of nylon 6/organoclay nanocomposite by blending with a thermotropic liquid crystalline polymer

A new approach for improving the wear performances of nylon 6 (PA6)/clay nanocomposites was examined in this study. Two hybrid nanocomposites were prepared by melt blending a thermotropic liquid crystalline polymer (TLCP) and a well‐dispersed PA6/clay nanocomposite, but with and without the incorporation of maleic‐anhydride grafted polypropylene (MAPP) as compatibilizer. The addition of MAPP improved the compatibility between TLCP and matrix and thus enhanced the fibrillation of dispersed TLCP phase. Wear‐testing results revealed that the wear resistance of the compatibilized hybrid nanocomposite could be improved effectively, as indicated by the low values of specific wear rate and frictional coefficient, especially under high‐normal load (i.e., 80 N). Based on the characterization on the worn damage and the debris, it was suggested that abrasive wear was the main‐damage mechanism for all the materials under investigation, except for the compatibilized hybrid nanocomposite. For this system, the wear damage was caused by a combination of abrasive and adhesive wearing because of the formation of transfer film on the counter pin surface from the wear debris. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

The performances of BMI nanocomposites filled with nanometer SiC

Nanocomposites of bismaleimide (BMI) with different proportions of nanometer SiC were prepared by a high shear dispersion process and casting method at elevated temperature. The mechanical and tribological properties of the nanocomposites were investigated. The bending strength and impact strength of the nanocomposite specimens were determined, and the sliding wear performance of the nanocomposites was investigated on an M‐200 friction and wear tester. The dispersion of nanometre SiC was observed with a transmission electron microscope (TEM), while those of the worn surfaces and transfer films on the counterpart steel ring were observed with a scanning electron microscope (SEM). The experimental results indicate that the nanocomposites exhibited lower friction coefficient and wear loss as well as higher bending and impact strength than BMI resin under the same testing conditions. The lowest wear rate was obtained with the nanocomposite containing 6.0 wt % SiC, while the highest mechanical properties were obtained with the nanocomposite containing 2.0 wt % SiC. The wear mechanism of the nanocomposite is mainly adhesion wear, while that of pure BMI resin is mainly fatigue cracking with plastic deformation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1246–1250, 2005     

Preparation and properties of poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)]/silica nanocomposite latex prepared using an acidic silica sol

BACKGROUND: Polyacrylate/silica nanocomposite latexes have been fabricated using blending methods with silica nanopowder, in situ polymerization with surface‐functionalized silica nanoparticles or sol–gel processes with silica precursors. But these approaches have the disadvantages of limited silica load, poor emulsion stability or poor film‐forming ability. RESULTS: In this work, poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)] [P(St‐BA‐AA)]/silica nanocomposite latexes and their dried films were prepared by adding an acidic silica sol to the emulsion polymerization stage. Morphological and rheological characterization shows that the silica nanoparticles are not encapsulated within polymer latex particles, but interact partially with polymer latex particles via hydrogen bonds between the silanol groups and the ? COOH groups at the surface of the polymer particles. The dried nanocomposite films have a better UV‐blocking ability than the pure polymer film, and retain their transparency even with a silica content up to 9.1 wt%. More interestingly, the hardness of the nanocomposite films increases markedly with increasing silica content, and the toughness of the films is not reduced at silica contents up to 33.3 wt%. An unexpected improvement of the solvent resistance of the nanocomposite films is also observed. CONCLUSION: Highly stable P(St‐BA‐AA)/silica nanocomposite latexes can be prepared with a wide range of silica content using an acidic silica sol. The dried nanocomposite films of these latexes exhibit simultaneous improvement of hardness and toughness even at high silica load, and enhanced solvent resistance, presumably resulting from hydrogen bond interactions between polymer chains and silica particles as well as silica aggregate/particle networks. Copyright © 2009 Society of Chemical Industry     

Structure and dielectric properties of polyimide/silica nanocomposite nanofoam prepared by solid‐state foaming

In this article, polyimide (PI)/silica nanocomposite nanofoams were prepared by solid‐state foaming using supercritical CO₂ as foaming agent. To control the cell size and morphology of the PI/silica foam, the silica nanoparticles as nucleating agent were in situ formation from TEOS via sol‐gel process, which make the silica nanoparticles homogeneously dispersed in PI matrix. The resulting PI/silica nanocomposite nanofoams were characterized by scanning electron microscopy (SEM), the image analysis system attached to the SEM and dielectric properties measurements. In PI/silica nanocomposite nanofoams, one type of novel morphology was shown that each cell contained one silica nanoparticle and many smaller holes about 20–50 nm uniformly located in the cell wall. This special structure could visually prove that the nucleation sites during foaming were formed on the surface of nucleating agents. Compared with those of neat PI foam, the cell size of PI/silica nanocomposite nanofoams was smaller and its distribution was narrower. The dielectric constant of PI/silica nanocomposite nanofoams was decreased because of the incorporation of the air voids into the PI/silica nanofoams. While the porosity of PI/silica nanocomposite nanofoam film was 0.45, the dielectric constant of the film (at 1 MHz) was reduced from 3.8 to about 2.6. Furthermore, the dielectric constant of PI/silica nanofoam films remained stable across the frequency range of 1×10²～1×10⁷ H_Z. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42355.     

Improvement of Hardness and Wear Resistance of Glass Fiber-Reinforced Epoxy Composites by the Incorporation of Silica/Carbon Hybrid Nanofillers

The tribological performance of hybrid composite (epoxy reinforced with woven, nonwoven tissue glass fibers, silica and carbon black nanoparticles) was investigated. Two methods were used to ensure good dispersion of nanoparticles in epoxy resin which were ultrasonic processor and magnetic stirrer. The effect of silica and/or carbon black nanoparticle content on microindentation hardness and wear properties of the neat glass fiber-reinforced epoxy composites was investigated. The results from the wear test indicated that, under all applied loads, incorporation of silica and carbon black nanoparticles either single or combined significantly improved the wear resistance of neat glass fiber reinforced epoxy. A significant increase in hardness of the hybrid nanocomposite laminates was achieved. Analysis of variance was developed to study the optimal wear testing parameters on composite samples. The most significant parameter is the time, followed by nanoparticle (silica and carbon black) content.     

Effect of silica nanoparticles on structure and properties of waterborne UV-curable polyurethane nanocomposites

UV-curable waterborne polyurethane (WUPU)/silica nanocomposites were prepared using various silica by phase-inversion emulsification method. TEM examinations of nanostructured films indicated that the organic modified nanosilica was well dispersed in the WUPU matrix, while the acid and alkaline silica formed much less compact, or densely aggregated structure. DMA analysis demonstrated that the WUPU/silica nanocomposite films had a broadening of the tanδ peak and shifted to higher temperature. The WUPU/silica nanocomposite films displayed enhanced storage modulus, Shore A hardness, tensile strength without sacrificing high elongation at break compared to that of the pure WUPU film. The resulting nanocomposite films are possibly interesting for the generation of waterborne UV-curable transparent coatings with scratch-resistance.     

Curing of epoxy resin by ultrafine silica modified by grafting of hyperbranched polyamidoamine using dendrimer synthesis methodology

Hyperbranched polyamidoamine–grafted silica was prepared according to dendrimer synthesis methodology. The modified silica was dispersed uniformly in epoxy resin, and the curing of epoxy resin proceeded successfully by heating in the presence of the modified silica; the gel fraction of the epoxy resin cured by the hyperbranched polyamidoamine–grafted silica (grafting = 80.2%) reached 77% at 170°C after 48 h. The gel fraction increased with increasing terminal amino group content of the hyperbranched polyamidoamine–grafted silica. In addition, the curing ability of the silica increased by complexation of the terminal amino groups of the grafted polyamidoamine with boron trifluoride. The modulus of elasticity of the curing materials obtained using the modified silica as a curing agent was lower than that using conventional a curing agent such as ethylenediamine in the presence of untreated silica. On the other hand, the heat resistance of the curing product using the modified silica was superior to that using ethylenediamine, but no difference in glass‐transition temperature was observed. It is expected that hyperbranched polyamidoamine grafted‐silica is incorporated uniformly with chemical bonds in the matrix of the epoxy resin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 573–579, 2001     

Thermal properties and morphology of a poly(vinyl alcohol)/silica nanocomposite prepared with a self‐assembled monolayer technique

A poly(vinyl alcohol) (PVA)/silica (SiO₂) nanocomposite was prepared with a novel self‐assembled monolayer technique, and its morphology and thermal properties were studied with different material characterization instruments. The treated SiO₂ nanoparticles were dispersed in the PVA matrix homogeneously, and the thermal properties of the nanocomposite were markedly improved in comparison with those of pure PVA. Under the same isothermal heating conditions, the decomposition of the nanocomposite was delayed significantly in comparison with that of PVA. The thermal degradation of the nanocomposite was a two‐step reaction, including the degradation of the side chain and main chain. The products of side‐chain degradation were mainly carboxylic acid, whereas main‐chain degradation primarily produced carbon dioxide and low‐molecular‐weight conjugated polyene. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1436–1442, 2005     

Carbon nanofibre‐reinforced ultrahigh molecular weight polyethylene for tribological applications

Carbon nanofibre (CNF)‐reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites containing up to 10 wt % of nanofibres were prepared by a novel solvent‐assisted extrusion process using short chain oligomers to tailor the melt viscosity of the UHMWPE matrix. A detailed investigation of the resulting nanocomposite microstructure and of the static mechanical properties revealed that the carbon nanofibres lead to improved mechanical properties of the UHMWPE related to the wear performance of such systems. Unidirectional sliding tests against a 100Cr6 steel under dry conditions verified the significant potential of dispersed carbon nanofibres to reduce the wear rate of this polymer. In light of the promising results, a further optimization of the processing conditions of such UHMWPE nanocomposites is expected to yield interesting future nanocomposite materials even for demanding applications such as artificial knee implants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4173–4181, 2007     

Effect of drawing on the molecular orientation,polymorphism, and properties of melt‐spun nanocomposite fibers based on nylon 6 with polyhedral oligomeric silsesquioxane,montmorillonite, and their combination

In this work, binary and ternary nanocomposite systems based on nylon 6 with montmorillonite (MMT), polyhedral oligomeric silsesquioxane (POSS), and their combination were prepared using a melt‐compounding process. In the transmission electron microscope (TEM) images, the MMT was found to be generally well dispersed in all materials resulting in its good chemical compatibility with nylon 6, affording intercalated disordered microstructures. On the other hand, the TEM images showed that POSS formed micron‐size crystalline agglomerates possibly resulting from a lack in chemical compatibility with nylon 6. These nanocomposite systems were melt‐spun into fibers, and the relevant structure–property relationships that occur during the cold drawing process was established by correlating the tensile properties to the changes in crystallinity, polymorphic crystal forms, and molecular orientation. The properties of the resulting fibers were found to be rather skewed and significantly affected by the polymer/nanoparticles interface. The agglomeration of POSS and POSS–MMT particles coupled with the weak nylon 6/POSS interface, reflected on the tensile properties of the nylon 6/POSS and nylon 6/MMT‐POSS fibers which underperformed. Some nanocomposite fiber systems offered significant improvements in modulus without excessively compromising the extensibility of the fibers. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Preparation and characterization of acrylic polymer nanocomposite films obtained from aqueous dispersions

A functionalized fumed silica was dispersed in water using a nonionic surfactant, yielding a stable nanodispersion. This was blended with an aqueous acrylic polymer dispersion to produce hybrid nanocomposite films. The silica particles were shown to be well dispersed in the polymer matrix, with little agglomeration. Further evidence of good compatibility between the silica and acrylic polymer was given by the improved thermal stability of the nanocomposite compared with the pristine polymer. The nanocomposite films exhibited significantly lower dirt pick‐up behavior, which seems to be associated to the nanoroughness of the composite film surface observed in AFM analysis. This decreases the contact area between film and micrometric dirt particles. Surface tension and hardness do not seem to be significantly different in the composite and noncomposite materials. This approach may provide a strategy to obtain hybrid coatings with self‐cleaning properties, taking advantage of the relatively low cost, and large availability of fumed silica. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effect of silica nanoparticles and carbon nanotubes on the toughness of a thermosetting epoxy polymer

Silica nanoparticles and multiwalled carbon nanotubes (MWCNTs) have been incorporated into an anhydride‐cured epoxy resin to form “hybrid” nanocomposites. A good dispersion of the silica nanoparticles was found to occur, even at relatively high concentrations of the nanoparticles. However, in contrast, the MWCNTs were not so well dispersed but relatively agglomerated. The glass transition temperature of the epoxy polymer was 145°C and was not significantly affected by the addition of the silica nanoparticles or the MWCNTs. The Young's modulus was increased by the addition of the silica nanoparticles, but the addition of up to 0.18 wt % MWCNTs had no further significant effect. The addition of both MWCNTs and silica nanoparticles led to a significant improvement in the fracture toughness of these polymeric nanocomposites. For example, the fracture toughness was increased from 0.69 MPam^1/2 for the unmodified epoxy polymer to 1.03 MPam^1/2 for the hybrid nanocomposite containing both 0.18 wt % MWCNTs and 6.0 wt % silica nanoparticles; the fracture energy was also increased from 133 to 204 J/m². The mechanisms responsible for the enhancements in the measured toughness were identified by observing the fracture surfaces using field‐emission gun scanning electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Friction and wear studies on nylon‐6/SiO2 nanocomposites

Composites of nanometer‐sized silica (SiO₂) filler incorporated in nylon‐6 polymer were prepared by compression molding. Their friction and wear properties were investigated on a pin on disk tribometer by running a flat pin of steel against a composite disc. The morphologies of the composites as well as of the wear track were observed by scanning electron microscopy (SEM). The addition of 2 wt % SiO₂ resulted in a friction reduction (μ) from 0.5 to 0.18 when compared with neat nylon‐6. This low silica loading led to a reduction in wear rate by a factor of 140, whereas the influence of higher silica loadings was less pronounced. The smooth morphology obtained after the wear test indicated the negligible contribution to friction of the pin to the nanocomposite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1855–1862, 2004     

Nylon 11/silica nanocomposite coatings applied by the HVOF process. II. Mechanical and barrier properties

Nylon 11 coatings filled with nominal 0–15 vol % of nanosized silica or carbon black were produced using the high velocity oxy‐fuel combustion spray process. The scratch and sliding wear resistance, mechanical, and barrier properties of nanocomposite coatings were measured. The effect of powder initial size, filler content, filler chemistry, coating microstructure, and morphology were evaluated. Improvements of up to 35% in scratch and 67% in wear resistance were obtained for coatings with nominal 15 vol % contents of hydrophobic silica or carbon black, respectively, relative to unfilled coatings. This increase appeared to be primarily attributable to filler addition and increased matrix crystallinity. Particle surface chemistry, distribution, and dispersion also contributed to the differences in coating scratch and wear performance. Reinforcement of the polymer matrix resulted in increases of up to 205% in the glass storage modulus of nanocomposite coatings. This increase was shown to be a function of both the surface chemistry and amount of reinforcement. The storage modulus of nanocomposite coatings at temperatures above the glass transition temperature was higher than that of unfilled coatings by up to 195%, depending primarily on the particle size of the starting polymer powder. Results also showed that the water vapor transmission rate through nanoreinforced coatings decreased by up to 50% compared with pure polymer coatings. The aqueous permeability of coatings produced from smaller particle size polymers (D‐30) was lower than the permeability of coatings produced from larger particles because of the lower porosities and higher densities achieved in D‐30 coatings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2272–2289, 2000     

Structure and properties of plasticized polyvinyl butyral‐silica nanocomposite films and test production of laminated glass using films

Plasticized polyvinyl butyral (PVB)‐silica nanocomposite films were formed by mixing PVB ethanol solution and silica sol, which was prepared from tetraethyl orthosilicate. The nanocomposite films were colorless and transparent even though the content of silica was 70 wt%. The glass transition temperature of PVB in the silica 2.5 wt% nanocomposites was higher by about 10°C than that of plasticized PVB. The PVB‐silica nanocomposite films were applied as an interlayer for laminated glass. The laminated glass made with the nanocomposite films containing less than 10 wt% silica showed good penetration resistance, not only at room temperature but also at 70°C. J. VINYL ADDIT. TECHNOL., 25:E59–E63, 2019. © 2018 Society of Plastics Engineers     

Preparation and property of raspberry‐like AS/SiO2 nanocomposite particles

Surfactant‐free poly(acrylonitrile‐co‐styrene)/silica (AS/SiO₂) nanocomposite particles was synthesized in the presence of cheap, commercially amorphous aqueous silica sol at ambient temperature. Thermogravimetric analysis (TGA) indicated silica contents ranging from 5 wt % to 29 wt %, depending on reaction conditions. Particle size distributions and morphologies were studied using dynamic light scattering (DLS) and transmission electron microscopy (TEM), which clearly showed that most of the colloidal nanocomposites comprised approximately spherical particle with raspberry‐like morphology and relatively narrow size distributions. The optical clarity of solution‐cast nanocomposite films was assessed using UV–vis spectrometer, with high transmission being obtained over the whole visible spectrum. Differential scanning calorimetry (DSC) studies showed that the glass transition temperature of AS/SiO₂ nanocomposites can be higher than the corresponding pure AS, resulting from the hydrophilicity of the nanometer silica. The robustness and simplicity of this method may make large‐scale manufacture of this nanocomposite possible. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 415–421, 2007     

Fabrication of inorganic/polymer nanocomposite membranes containing very high silica content via in situ surface grafting reaction and reactive dispersion of silica nanoparticles: Proton conduction,water uptake,and oxidative stability

In this study, we present a new fabrication process for proton exchange membranes based on inorganic/organic nanocomposite using in situ surface grafting reaction and reactive dispersion of silica nanoparticles in the presence of reactive dispersant, urethane acrylate nonionomer (UAN). Through in situ surface grafting reaction of silica nanoparticles, urethane acrylates were chemically introduced on the surface of silica nanoparticles, which were dispersed in DMSO solutions containing UAN and sodium styrene sulfonate (NaSS). After urethane linkage and copolymerization of NaSS, UAN and urethane acrylate moieties of silica nanoparticles, the solutions were converted to silica nanoparticle‐dispersed proton exchange membranes where silica particles were chemically connected with organic polymer chains. 5.89–29.45 wt % of silica nanoparticles could be dispersed and incorporated in polymer membranes, which were confirmed by transmittance electron microscopy (TEM) measurement. On varying weight % of silica nanoparticles dispersed within the membranes, water uptake and oxidative stability of nanocomposite membranes were largely changed, but membranes showed almost the same proton conductivity (greater than 10⁻² S cm⁻¹). At 5.89 wt % of silica nanoparticles, nanocomposite membranes showed the lowest water uptake and excellent oxidative stability compared to the sulfonated polyimide membranes fabricated by us. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

ZnO nanoparticles dispersed poly(aniline‐co‐o‐anthranilic acid) composites: Photocatalytic reduction of Cr(VI) and Ni(II)

In this report, poly(aniline‐co‐anthranilic acid)/zinc oxide (poly(ANI‐co‐ANA)/ZnO) nanocomposites were prepared by in‐situ chemical oxidative polymerization. Transmission electron microscopy (TEM), X‐ray diffraction, Fourier transform infrared spectroscopy, and ultraviolet–visible spectroscopy measurements were used to characterize the resulting pure copolymer and nanocomposite. TEM analysis showed that the nanoparticles with a mean diameter of 15–25 nm were dispersed in the copolymer matrix. Thermogravimetric analysis indicated that the nanocomposite had a higher decomposition temperature than the pure copolymer. The conductivity measurements showed the resulting nanocomposite possessed higher conductivity as compared to the pure copolymer. Photocatalytic removal of Cr(VI) and Ni(II) from aqueous solution using as‐synthesized nanocomposite under UV‐light irradiation was studied. The reduction patterns of Cr(VI) and Ni(II) were better fitted to first‐order kinetic model. The nanocomposite was also applied as a photocatalyst for the degradation of methylene blue dye. The result revealed substantial degradation of the dye (∼82%) under UV‐light illumination. POLYM. COMPOS., 35:839–846, 2014. © 2013 Society of Plastics Engineers     

Rheological characterization of UV‐curable epoxy systems: Effects of o‐Boehmite nanofillers and a hyperbranched polymeric modifier

An organo‐modified Boehmite (o‐Boehmite) was used to prepare nanocomposite UV‐curing coatings, based on a cycloaliphatic epoxy resin (3,4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexane carboxylate). A hyperbranched polymer (HBP) based on highly branched polyester, was also added to the resin, with the aim to modify its reactivity, such as a possible route to increase the toughness of the resin. Different amounts of the nanofiller and the HBP, ranging from 5 up to 20 wt % of resin, were dispersed into the resin in the presence of triarylsulfonium hexafluoroantimonate, as a photoinitiator for the UV curing of the resin. The rheological behavior of the formulations produced was studied as function of the shear rate and of the content of each filler using a cone and plate rheometer. A general increase in viscosity was observed with increasing the volume fraction of each filler and a moderate pseudoplastic behavior was observed when o‐Boehmite filler was added. A non‐Newtonian behavior was observed with the incorporation of the HBP. The viscosity of the epoxy/boehmite resin mixtures was analyzed as function of the nanofiller volume fraction. In the case of epoxy/hyperbranched resin mixtures, the Cross equation was used to predict the viscosity of each formulation as a function of the shear rate and an appropriate relationship to predict the viscosity of each formulation as a function of the filler volume fraction, was determined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009