Silica/polystyrene and silica/polystyrene‐b‐polymethacryloxypropyltrimethoxysilane hybrid nanoparticles via surface‐initiated ATRP and comparison of their wettabilities

Both silica/polystyrene (SiO₂/PS) and silica/polystyrene‐b‐polymethacryloxypropyltrimethoxysilane (SiO₂/PS‐b‐PMPTS) hybrid nanoparticles were synthesized via surface‐initiated atom transfer radical polymerization (SI‐ATRP) from SiO₂ nanoparticles. The growths of all polymers via ATRP from the SiO₂ surfaces were well controlled as demonstrated by the macromolecular characteristics of the grafted chains. Their wettabilities were measured and compared by water contact angle (WCA) and surface roughness. The results show that the nanoparticles possess hydrophobic surface properties. The static WCA of SiO₂/PS‐b‐PMPTS hybrid nanoparticles is smaller than that of SiO₂/PS hybrid nanoparticles, meanwhile, the surface roughness of SiO₂/PS‐b‐PMPTS hybrid nanoparticles is yet slightly rougher than that of SiO₂/PS hybrid nanoparticles, which shows that the combination and competition of surface chemistry and roughness of a solid material can finally determine its wettability. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Effect of nanoparticles on heat capacity of nanofluids based on molten salts as PCM for thermal energy storage

In this study, different nanofluids with phase change behavior were developed by mixing a molten salt base fluid (selected as phase change material) with nanoparticles using the direct-synthesis method. The thermal properties of the nanofluids obtained were investigated. These nanofluids can be used in concentrating solar plants with a reduction of storage material if an improvement in the specific heat is achieved. The base salt mixture was a NaNO₃-KNO₃ (60:40 ratio) binary salt. The nanoparticles used were silica (SiO₂), alumina (Al₂O₃), titania (TiO₂), and a mix of silica-alumina (SiO₂-Al₂O₃). Three weight fractions were evaluated: 0.5, 1.0, and 1.5 wt.%. Each nanofluid was prepared in water solution, sonicated, and evaporated. Measurements on thermophysical properties were performed by differential scanning calorimetry analysis and the dispersion of the nanoparticles was analyzed by scanning electron microscopy (SEM). The results obtained show that the addition of 1.0 wt.% of nanoparticles to the base salt increases the specific heat of 15% to 57% in the solid phase and of 1% to 22% in the liquid phase. In particular, this research shows that the addition of silica-alumina nanoparticles has a significant potential for enhancing the thermal storage characteristics of the NaNO₃-KNO₃ binary salt. These results deviated from the predictions of the theoretical model used. SEM suggests a greater interaction between these nanoparticles and the salt.     

Interfacial effects in polypropylene–silica nanocomposites

Grafted inorganic nanoparticles can greatly improve the mechanical performance of polymers. To examine the effects of the interfacial characteristics generated by the grafting polymer bonded to nanoparticle surfaces, we chemically grafted nano‐silica with different polymers and then melt‐mixed it with polypropylene (PP). We extracted the homopolymers produced during the graft polymerization from the grafted products before the composites were manufactured to get rid of the side effects of the nongrafting polymers. We tailored the interfacial interaction between the grafted nano‐SiO₂ and PP matrix by changing the amount of the grafting polymers on the nanoparticles, that is, the grafting percentage. Mechanical tests indicated that all the composites incorporated with grafted nano‐SiO₂ particles possessed much higher impact strength than untreated SiO₂/PP composites and neat PP. The greatest contribution of the particles was made at a low grafting percentage. Tensile measurements showed that the treated nanoparticles could provide PP with stiffening, strengthening, and toughening effects at a rather low filler content (typically 0.8 vol %) because of the enhanced interfacial adhesion resulting from molecular entanglement and interdiffusion between the grating polymers on the nanoparticles and matrix macromolecules. The presence of grafting polymers on the nanoparticles provided the composites with a tailorable interphase. The tensile performance of the composites was sensitive to the nature of the grafting polymers. Basically, a hard interface was beneficial to stress transfer, whereas a soft one hindered the development of cavities in the matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1771–1781, 2004     

Preparation of poly(methyl methacrylate)‐Silica nanoparticles via differential microemulsion polymerization and physical properties of NR/PMMA‐SiO2 hybrid membranes

Poly(methy methacrylate) (PMMA)‐SiO₂ nanoparticles were prepared via differential microemulsion polymerization. The effects of silica loading, surfactant concentration, and initiator concentration on monomer conversion, particle size, particle size distribution, grafting efficiency, and silica encapsulation efficiency were investigated. A high monomer conversion of 99.9% and PMMA‐SiO₂ nanoparticles with a size range of 30 to 50 nm were obtained at a low surfactant concentration of 5.34 wt% based on monomer. PMMA‐SiO₂ nanoparticles showed spherical particles with a core‐shell morphology by TEM micrographs. A nanocomposite membrane from natural rubber (NR) and PMMA‐SiO₂ emulsion was studied for mechanical and thermal properties and pervaporation of water‐ethanol mixtures. PMMA‐SiO₂ nanoparticles which were uniformly dispersed in NR matrix, significantly enhanced mechanical properties and showed high water selectivity in permeate flux. Thus, the NR/PMMA‐SiO₂ hybrid membranes have great potential for pervaporation process in membrane applications. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Synthesis and characterization of PMMA/SiO2 organic–inorganic hybrid materials via RAFT‐mediated miniemulsion polymerization

In this article, we first carried out the surface modification of SiO₂ using silane coupling agent KH570, and then prepared PMMA/SiO₂ organic–inorganic hybrid materials by conventional free radical polymerization and RAFT polymerization in miniemulsion, respectively. The kinetics comparisons of these two polymerizations were studied. PMMA/SiO₂ hybrid materials were characterized by gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. Experimental results indicated that the polymerization behavior of MMA in miniemulsion showed controlled/living radical polymerization characteristics under the control of RAFT agent. Incorporation of RAFT agent and SiO₂ nanoparticles improved the thermal properties of polymers, the thermal stability of polymers increased with increasing content of SiO₂ nanoparticles. The structures and morphologies of SiO₂, modified SiO₂, and PMMA/SiO₂ hybrid materials were characterized by FT‐IR and TEM. TEM results showed that the addition of modified SiO₂ nanoparticles to miniemulsion polymerization system obtained different morphology latex particles. Most of modified SiO₂ nanoparticles were wrapped by polymer matrix after polymerization. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Impedance spectroscopy of siloxane‐containing polyazomethines blended with SiO2

Two siloxane‐containing polyazomethines (PAZx) blended with SiO₂ were investigated. SiO₂ was obtained by sol‐gel method. The size of obtained SiO₂ particles was about 408 nm as was confirmed by SEM technique. For the blended with silica polymers absorption UV‐vis properties were tested and compare with unblended ones. Electrical behavior of the two kind devices indium tin oxide (ITO)/PAZx : SiO₂/Al and ITO/PEDOT : PSS/PAZx : SiO₂/Al were tested by impedance spectroscopy in dark and under illumination (halogen lamp, 100 mW/cm²) in the frequency range of 1 Hz to 1 MHz with maximum voltage value of 20 mV. For all measured devices, Nyquist plots were presented. PEDOT : PSS interlayer improved electrical properties of made prototype polymeric solar cells. Blending PAZx with silica increased conductivity from 10^–15 to 10^–8 S/cm. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and applications of novel fluoroalkyl end‐capped sulfonic acid oligomers–silica gel polymer hybrids

Fluoroalkyl end‐capped 2‐methacryloxyethanesulfonic acid homo‐oligomer [R_F–(MES)_n–R_F] and 2‐methacryloxyethanesulfonic acid–N,N‐dimethylacrylamide co‐oligomers [R_F–(MES)_x–(DMAA)_y–R_F] reacted with tetraethoxysilane (TEOS) under acidic conditions to afford R_F–(MES)_n–R_F homo‐oligomer–SiO₂ polymer hybrid and R_F–(MES)_x–(DMAA)_y–R_F co‐oligomer–SiO₂ polymer hybrid, respectively. Thermogravimetric–mass spectra showed that the thermal stability of R_F–(MES)_n–R_F homo‐oligomer–SiO₂ polymer hybrid was superior to that of traditionally well‐known perfluorinated ion exchange polymers such as Nafion 112 (TR). The sol solutions of the fluorinated co‐oligomer–SiO₂ polymer hybrid were applied to the surface modification of glass to exhibit not only a strong oleophobicity imparted by fluorine but also a good hydrophilicity on the glass surface. On the other hand, R_F–(MES)_x–(DMAA)_y–R_F co‐oligomer reacted with TEOS in the presence of a variety of silica nanoparticles (mean diameters: 11–95 nm) under alkaline conditions to afford fluoroalkyl end‐capped oligomers–silica nanoparticles (mean diameters: 32–173 nm) with a good dispersibility and stability in methanol. Similarly, a variety of fluorinated oligomers containing sulfo groups–silica nanoparticles were prepared by the homo‐ and co‐oligomerizations of fluoroalkanoyl peroxides with 2‐methacryloxyethane sulfonic acid (MES) and comonomers such as N,N‐dimethylacrylamide (DMAA) and acryloylmorpholine (ACMO) in the presence of silica nanoparticles. Interestingly, these isolated fluorinated particle powders were found to afford nanometer size‐controlled colloidal particles with a good redispersibility and stability in aqueous and organic media such as methanol. These fluorinated nanoparticles containing sulfo groups were also applied to an excellent heterogeneous catalyst for Bronsted acid‐catalyzed transformations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 110–117, 2007     

Effect of neodymium‐doped titanium dioxide nanoparticles on the structural,mechanical, and electrical properties of poly(butyl methacrylate) nanocomposites

Nanocomposites based on neodymium‐doped titanium dioxide (Nd‐TiO₂)/poly(n‐butyl methacrylate) (PBMA) have been prepared by an in situ polymerization of butyl methacrylate monomer with varying concentrations of Nd‐TiO₂ nanoparticles. The resulting nanocomposites have been analyzed by ultraviolet (UV)–Visible spectroscopy, Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis, and impedance analyzer (TGA). The results of UV and FTIR spectroscopy have indicated the interaction of nanoparticles with the PBMA matrix. Spherically shaped nanoparticles with an average size of 10–25 nm have been revealed in the TEM and their homogeneous dispersion, and interaction of polymer matrix has been confirmed by SEM and XRD studies. The thermal stability and glass transition temperature of the composites were significantly enhanced by the addition of nanoparticles. The AC conductivity and dielectric properties of nanocomposites have been found to be higher than pure PBMA, and the maximum electrical properties have been observed for 7 wt% composite. The reinforcing nature of the nanoparticles in PBMA has been reflected in the improvement in tensile strength measurements. The result indicated that the tensile strength of nanocomposites have greatly enhanced by the addition of Nd‐TiO₂ nanoparticles whereas the elongation at break decreases with the loading of nanofillers. To understand the mechanism of reinforcement, tensile strength values have been correlated with various theoretical modeling. The research has been found to be promising in the development of novel materials with enhanced tensile strength, dielectric constant, and thermal properties, which may find potential applications in energy storage and nanoelectronic devices. J. VINYL ADDIT. TECHNOL., 25:9–18, 2019. © 2018 Society of Plastics Engineers     

PES/SiO2 nanocomposite by in situ polymerization: Synthesis,structure, properties,and new applications

SiO₂ nanoparticles of a quantum size (15 nm or less) were prepared via sol–gel method using tetraethylorthosilicate as a precursor. SiO₂ nanoparticles were characterized by X‐ray diffraction (XRD) and field‐emission scanning electron microscopy (FESEM) analyses. Polyethersulfone/silica (PES/SiO₂) crystal structure nanocomposite was prepared by in situ polymerization using silica nanoparticles as reinforcement filler. The polymerization reaction was done at 160°C in paraffin bath in the presence of diphenolic monomers. XRD and FESEM analyses were used to study the morphology of the synthesized nanocomposite. The purity and thermal property of the PES/SiO₂ nanocomposite were studied by energy dispersion of X‐ray analysis and differential scanning calorimetry, respectively. The effect of silica particles on the hydrophilicity of PES/SiO₂ nanocomposite was also investigated. It was showed that the PES/SiO₂ nanocomposite had a higher swelling degree when compared with the pure PES. The synthesized PES/SiO₂ powder was used to remove Cu(II) ions from its aqueous solution. The effect of experimental conditions such as pH, shaking time, and sorbent mass on adsorption capacity of PES/SiO₂ nanocomposite were investigated. It was found that incorporation of a low amount of silica (2 wt%) into the polymer matrix caused the increase of the Cu(II) ions adsorption capacity of PES. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Utilization of silane functionalized carbon nanotubes‐silica hybrids as novel reinforcing fillers for solution styrene butadiene rubber

Carbon nanotubes‐silica (CNTs‐SiO₂) nanohybrid filler was fabricated by coating inorganic silica on multi‐wall CNTs through a sol–gel process. The CNTs‐SiO₂ nanohybrids were then functionalized by 3‐methacryloxypropyltrimethoxysilane (3‐MPTS) followed by compounding to solution styrene butadiene rubber (S‐SBR) through mechanical mixing. The Fourier‐transform infrared spectroscopy showed that the CNTs were coated by inorganic SiO₂, and grafted with 3‐MPTS successfully. The functionalized CNTs‐SiO₂ nanohybrids had a rough surface as revealed by transmission electron microscope images. After hybridization and grafting, the functionalized CNTs‐SiO₂ nanohybrids still maintained the crystal structure of CNTs, which was determined by X‐ray diffraction and Raman spectrum. The addition of nanohybrids accelerated the vulcanization process and improved the crosslinking degree of vulcanizates. With adding 10 phr (parts per hundred of rubber) functionalized CNTs‐SiO₂, the mechanical properties of S‐SBR vulcanizates were improved significantly. The tensile moduli at 100% elongation (M₁₀₀) and tensile strength had 54% and 28% increase, respectively. The incorporation of functionalized CNTs‐SiO₂ nanohybrids also largely enhanced the storage modulus, and slightly increased the thermal conductivity of vulcanizates. POLYM. COMPOS., 00:000–000, 2013. © 2013 Society of Plastics Engineers POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Novel copolymer for SiO2 nanoparticles dispersion

High performance polymers exhibiting multifunctional characteristics can be achieved by the introduction of inorganic nanoparticles like SiO₂ into the functional polymers. In the present work a copolymer epoxy poly(dimethylacrylamide) was synthesized to disperse the SiO₂ nanoparticles. The aim of the work is to develop a new method/process/material for the dispersion of nanoparticles and evaluating the performance of these composites. FT‐IR studies of the polymer adsorbed SiO₂ nanoparticles confirmed that the polymer molecules chain was anchored on the surface of the SiO₂ nanoparticles. The improved interfacial interaction between the particles and polymer enhanced the thermal properties of the composites. The results also show the newly synthesized polymer disperse the nanoparticles well as evidenced by SEM analysis, the uniformly dispersed SiO₂ nanoparticles in the polymer matrix and the particles almost remained in their original shape and size even after incorporation in to the polymer matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dissolution behavior of silica in molten CaO–SiO2–Fe2O3–MgO–MnO slag

The modification of basic oxygen furnace (BOF) slag by adding silica can improve the properties of BOF slag for applications in the cement industry. The rapid dissolution of silica is essential to hot slag modification. In this work, the dissolution behavior of silica in the molten CaO–SiO₂–Fe₂O₃–MgO–MnO system as synthetic BOF slag was investigated by using the traditional rotating cylinder technique. Effects of rotation speed, temperature, immersion time, and slag basicity on the silica dissolution were studied. Scanning electron microscopy equipped with energy dispersive spectrometer (SEM-EDS) and FactSage simulations were employed to reveal the dissolution mechanism. It was found that the dissolution of the silica rod was affected by both the thermodynamic driving force and the slag viscosity. The silica dissolution rate in molten CaO–SiO₂–Fe₂O₃–MgO–MnO slag increased with increasing the rotation speed and temperature, but first increased and then decreased when decreasing the slag basicity from 2.5 to 1.5. A linear correlation between the logarithm of the dissolution rate and the logarithm of cylinder periphery velocity with a slope of 0.44 was observed, indicating the mass transfer within the boundary layer as the dissolution rate determining step. A direct dissolution way was found during the dissolution of silica in molten CaO–SiO₂–Fe₂O₃–MgO–MnO slag.     

Mechanical properties of low nano‐silica filled high density polyethylene composites

Modification of nanoparticles through graft polymerization is able to change the chemical nature of the particles' surfaces and provides an effective means for the preparation of nano‐fillers specified for composites manufacturing. The present work focuses on the mechanical role of grafted nano‐SiO₂ particles in high density polyethylene composites prepared by melt compounding. The experimental results show that at a content of 0.75 vol%, the modified nano‐silica results in a rise in tensile stiffness, tensile strength and impact strength of the composites. The grafted nanoparticles can improve the mechanical performance of the matrix polymer more effectively than the untreated version. In addition, a further enhancement of the composites stiffness and strength can be achieved by crosslinking the concentrated masterbatches, which has not yet been revealed in the authors' previous works on grafted nano‐SiO₂ particles/polypropylene composites. It is thus revealed that the introduction of the grafting polymers onto the nanoparticles increases the tailorability of the composites.     

The effect of silica (SiO2) nanoparticles and ammonia/ethylene plasma treatment on the interfacial and mechanical properties of carbon-fiber-reinforced epoxy composites

A nanoparticle dispersion is known to enhance the mechanical properties of a variety of polymers and resins. In this work, the effects of silica (SiO₂) nanoparticle loading (0–2 wt%) and ammonia/ethylene plasma-treated fibers on the interfacial and mechanical properties of carbon fiber–epoxy composites were characterized. Single fiber composite (SFC) tests were performed to determine the fiber/resin interfacial shear strength (IFSS). Tensile tests on pure epoxy resin specimens were also performed to quantify mechanical property changes with silica content. The results indicated that up to 2% SiO₂ nanoparticle loading had only a little effect on the mechanical properties. For untreated fibers, the IFSS was comparable for all epoxy resins. With ethylene/ammonia plasma treated fibers, specimens exhibited a substantial increase in IFSS by 2 to 3 times, independent of SiO₂ loading. The highest IFSS value obtained was 146 MPa for plasma-treated fibers. Interaction between the fiber sizing and plasma treatment may be a critical factor in this IFSS increase. The results suggest that the fiber/epoxy interface is not affected by the incorporation of up to 2% SiO₂ nanoparticles. Furthermore, the fiber surface modification through plasma treatment is an effective method to improve and control adhesion between fiber and resin.     

Preparation and properties of polyimide/silica hybrid nanocomposites

In this study, a commercially available nano‐sized silica (SiO₂) was surface‐modified via esterification with oleic acid (OA), a relatively inexpensive and hydrophobic modifier. The surface‐modified silica (SiO₂‐OA) nanoparticles were used to disperse in the poly(amic acid) solutions of a commercial polyimide (PI), used for two‐layer film, and thermally imidized to form a series of PI/silica nanocomposites. The effects of the addition of SiO₂‐OA nanoparticles on the properties of the as‐prepared PI/silica nanocomposites were studied. The results indicated that the as‐prepared PI/silica nanocomposites exhibited improvements in the dynamic mechanical property, thermal stability, water resistance, and thermal expansion. POLYM. COMPOS. 28:575–581, 2007. © 2007 Society of Plastics Engineers     

A novel approach to prepare PBT nanocomposites with elastomer‐modified SiO2 particles

Poly(butylenes terephthalate) (PBT)/SiO₂ nanocomposites with uniform dispersion, strong interfacial adhesion, and improved mechanical properties have been prepared by a novel approach. Ethylene‐methyl acrylate‐glycidyl methacrylate (E‐MA‐GMA) elastomer chains were first chemically grafted onto the surface of SiO₂ nanoparticles. Fourier transform infrared spectra result shows that elastomer‐modified SiO₂ nanoparticles exhibit absorption at 2963–2862 cm⁻¹ of the stretching modes of C H, which suggests the reaction between the hydroxyl groups of SiO₂ surface and epoxy groups of E‐MA‐GMA. And the binding energy of Si2p and O1s of the elastomer‐modified SiO₂ shifts to lower binding energy, which further confirms the formation of Si O C bonds. This surface treatment allows SiO₂ nanoparticles homogeneously dispersing in PBT matrix. The morphology with loose aggregates contains networked SiO₂ particles with an interparticle distance ranging from 0 to 30 nm. As a result, the storage modulus and the tensile properties of PBT/E‐MA‐GMA‐SiO₂ nanocomposites are higher than those of pure PBT and PBT with untreated SiO₂. The incorporation of E‐MA‐GMA‐modified SiO₂ particles increases the tensile strength and modulus to 58.4MPa and 2661MPa respectively, which is 8% and 16% higher than those of pure PBT. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Preparation by melt mixing and characterization of isotactic polypropylene/SiO2 nanocomposites containing untreated and surface‐treated nanoparticles

In the present study two series of isotactic polypropylene (iPP)/SiO₂ nanocomposites containing 1, 2.5, 5, 7.5, and 10 wt % SiO₂ nanoparticles were prepared by melt‐mixing on a twin‐screw corotating extruder. In the first series untreated fumed silica nanoparticles were used, whereas in the second nanoparticles were surface‐treated with dimethyldichlorosilane. In both cases, the average size of the primary nanoparticles was 12 nm. Tensile and impact strength were found to increase and to be affected mainly by the type and content of silica nanoparticles. A maximum was observed, corresponding to samples containing 2.5 wt % SiO₂. These findings are discussed in light of the SEM and TEM observations. By increasing the amount of nanoparticles, large aggregates of fumed silica could be formed, which may explain the reduction of mechanical properties with higher concentrations of SiO₂. However, it was found that surface‐treated nanoparticles produced larger aggregates than did those derived from untreated nanoparticles, despite the increased adhesion of the iPP matrix, as was postulated from yield strength. This behavior negatively affected mechanical properties. In addition, an effort was made to determine if toughening theories, mainly the critical interparticle distance for rubber toughening or composites, also might be applicable in nanocomposites. From DSC measurements it was demonstrated that silica nanoparticles acted as effective nucleating agents, increasing the crystallization rate and the degree of crystallinity of iPP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2684–2696, 2006     

PEGylated hollow pH‐responsive polymeric nanocapsules for controlled drug delivery

Novel pH‐responsive PEGylated hollow nanocapsules (HNCaps) were fabricated through a combination of distillation–precipitation copolymerization and surface thiol–ene ‘click’ grafting reaction. For this purpose, SiO₂ nanoparticles were synthesized using the Stöber approach, and then modified using 3‐(trimethoxysilyl)propyl methacrylate (MPS). Afterward, a mixture of triethyleneglycol dimethacrylate (as crosslinker), acrylic acid (AA; as pH‐responsive monomer) and MPS‐modified SiO₂ nanoparticles (as sacrificial template) was copolymerized using the distillation–precipitation approach to afford SiO₂@PAA core–shell nanoparticles. The SiO₂ core was etched from SiO₂@PAA using HF solution, and the obtained PAA HNCaps were grafted with a thiol‐end‐capped poly(ethylene glycol) (PEG) through a thiol–ene ‘click’ reaction to produce PAA‐g‐PEG HNCaps. The fabricated HNCaps were loaded with doxorubicin hydrochloride (DOX) as a model anticancer drug, and their drug loading and encapsulation efficiencies as well as pH‐dependent drug release behavior were investigated. The anticancer activity of the drug‐loaded HNCaps was extensively evaluated using MTT assay against human breast cancer cells (MCF7). The cytotoxicity assay results as well as superior physicochemical and biological features of the fabricated HNCaps mean that the developed DOX‐loaded HNCaps have excellent potential for cancer chemotherapy. © 2020 Society of Chemical Industry     

Preparation and characterization of thermoplastic vulcanizate/silica nanocomposites

This article describes the preparation, characterization, and properties of thermoplastic vulcanizate (TPV)/silica nanocomposites. The nanocomposites were prepared by the melt blending of TPV and maleic anhydride grafted polypropylene (mPP) into organically modified SiO₂ (m‐SiO₂), treated with n‐hexadecyl trimethylammonium bromide as a grafting agent for TPV during the melt mixing. The thermal stability and storage modulus of the 1 wt % m‐SiO₂ containing TPV/mPP/m‐SiO₂ nanocomposite were higher than those of pristine TPV. The most important observation was obtained from dynamic mechanical analysis, which revealed that the glass‐transition temperature of the polypropylene phase of the nanocomposites increased (in comparison with that of virgin TPV), whereas the ethylene–propylene–diene monomer phase remained almost the same. The adhesion strength between the TPV/mPP/m‐SiO₂ nanocomposites and steel also increased with increasing m‐SiO₂ content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2058–2063, 2005     

Synthesis of Polystyrene/Hydrophobic SiO2 Composite Particles via Oil‐in‐Water Pickering Emulsion Polymerization

The aim of this work is to present a facile Pickering emulsion polymerization method for the synthesis of submicron polystyrene/SiO₂ core/shell composite particles. The commercial hydrophobic SiO₂ nanoparticles were used as stabilizing agent for creating a stable oil‐in‐water emulsion. Although the adsorption of hydrophobic SiO₂ nanoparticles in the emulsion system was unfavorable in terms of thermodynamics, by ultrasound treatment, self‐assembly of hydrophobic SiO₂ nanoparticles effectively stabilized oil‐in‐water Pickering emulsions during polymerization. Using 3 wt.% SiO₂ nanoparticles (based on styrene monomer) and 1:10 volume ratio of styrene monomer:water, the composite particles having average size of 790 nm and relatively narrow particles distribution were produced. With decreasing the volume ratio, smaller composite particles were created. Results from scanning electron microscope revealed that SiO₂ nanoparticles were located exclusively at the surface of the polystyrene latex particles. The SiO₂ content, determined by thermogravimetric analysis, was 12.6 wt.% in the composite particles. The route reported here may be used for the preparation of other composite nanostructures. POLYM. ENG. SCI., 59:E195–E199, 2019. © 2018 Society of Plastics Engineers