Epoxy/acrylonitrile-butadiene-styrene copolymer/clay ternary nanocomposite as impact toughened epoxy

Epoxy resins have low impact strength and poor resistance to crack propagation, which limit their many end use applications. The main objective of this work is to incorporate both acrylonitrile-butadiene-styrene copolymer (ABS) and organically modified clay (Cloisite 30B) into epoxy matrix with the aim of obtaining improved material with the impact strength higher than neat epoxy, epoxy/clay and epoxy/ABS hybrids without compromising the other desired mechanical properties such as tensile strength and modulus. Impact and tensile properties of binary and ternary systems were investigated. Tensile strength, elongation at break and impact strength were increased significantly with incorporation of only 4 phr ABS to epoxy matrix. For epoxy/clay nanocomposite with 2.5% clay content, tensile modulus and strength, and impact strength were improved compared to neat epoxy. With incorporation of 2.5% clay and 4 phr ABS into epoxy matrix, 133% increase was observed for impact strength. Ternary nanocomposite had impact and tensile strengths greater than values of the binary systems. Morphological properties of epoxy/ABS, epoxy/clay and epoxy/ABS/clay ternary nanocomposite were studied using atomic force microscopy (AFM) phase imaging, scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). New morphologies were achieved for epoxy/ABS and epoxy/ABS/clay hybrid materials. Exfoliated clay structure was obtained for epoxy/clay and epoxy/ABS/clay nanocomposite.     

Preparation and properties of TiO2‐filled poly(acrylonitrile‐butadiene‐styrene)/epoxy hybrid composites

Poly (acrylonitrile‐butadiene‐styrene) (ABS) was used to modify diglycidyl ether of bisphenol‐A type of epoxy resin, and the modified epoxy resin was used as the matrix for making TiO₂ reinforced nanocomposites and were cured with diaminodiphenyl sulfone for superior mechanical and thermal properties. The hybrid nanocomposites were characterized by using thermogravimetric analyzer (TGA), dynamic mechanical analyzer (DMA), universal testing machine (UTM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The bulk morphology was carefully analyzed by SEM and TEM and was supported by other techniques. DMA studies revealed that the DDS‐cured epoxy/ABS/TiO₂ hybrid composites systems have two T_gs corresponding to epoxy and ABS rich phases and have better load bearing capacity with the addition of TiO₂ particles. The addition of TiO₂ induces a significant increase in tensile properties, impact strength, and fracture toughness with respect to neat blend matrix. Tensile toughness reveals a twofold increase with the addition of 0.7 wt % TiO₂ filler in the blend matrix with respect to neat blend. SEM micrographs of fractured surfaces establish a synergetic effect of both ABS and TiO₂ components in the epoxy matrix. The phenomenon such us cavitation, crack path deflection, crack pinning, ductile tearing of the thermoplastic, and local plastic deformation of the matrix with some minor agglomerates of TiO₂ are observed. However, between these agglomerates, the particles are separated well and are distributed homogeneously within the polymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of poly(oxyalkylene)amines on structure and properties of epoxide nanocomposites

A shortcoming of most polymer nanocomposites is relatively low toughness. An effective method to eliminate this is the use of a suitable combination of polymeric impact modifiers with organoclay, which may impart synergistic effects on the mechanical behavior of both thermoplastic and thermoset matrix nanocomposites. This work focuses on the effect of various combinations of amine-terminated (APOP) and hydroxyl-terminated poly(oxypropylene) (POP) and layered silicates on the structure and mechanical behavior of epoxy nanocomposites. The combination of APOP and POP with 0.5−5% wt % of organoclay leads to some compositions that produce well balanced mechanical behavior of the epoxy nanocomposite. The higher toughening effectiveness of APOP/montmorillonite (MMT) compared with that of POP/MMT is a consequence of formation of blended domains consisting of clay tactoids and fine APOP inclusions. An increase in the dispersed particle size with clay content was observed to be a consequence of more significant clay-induced nucleation of phase separation at the expense of clay-induced accelerated curing. The best mechanical behavior was observed for materials using an adduct of APOP and MMT, which was obtained using the ion exchange of sodium ions of MMT by protonated APOP. The enhanced mechanical behavior was due to the formation of nanosized planar arrays by self-pilling of elastomer-modified clay and the corresponding increase in the T_g of the epoxy. The structure/property relationships of these systems indicate that this type of clay polymer combination provides an effective way of modifying the mechanical behavior of epoxy nanocomposites. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Progress on Epoxy/Polyamide and Inorganic Nanofiller-Based Hybrids: Introduction,Application, and Future Potential

An efficient method to obtain better properties of epoxy-based nanocomposites is to introduce thermoplastic polymer such as polyamide into thermosetting resin. Combined effect of both polymers provides extra-bonding sites for nanofiller dispersion. This review mainly covers inorganic nanofiller dispersed epoxy/polyamide nanocomposite and their applications. To understand interaction between thermoset epoxy and thermoplastic polyamide, knowledge of structure, synthesis, and categorization is worth important. Addition of inorganic nanofiller such as layered silicate and metal oxide results in enhanced thermomechanical, physiochemical, and anticorrosive properties of resultant nanocomposite. These nanocomposites have applications as protective coatings, adhesives, insulators in electrical devices, and in aerospace industries.     

Synthesis and characterization of well-defined poly (4-chloromethyl styrene-g-4-vinylpyridine)/TiO2 nanocomposite via ATRP technique

Poly (4-chloromethyl styrene-g-4-vinylpyridine)/TiO₂ [(PCMSt-g-P4VP)/TiO₂] nanocomposite was synthesized by atom transfer radical polymerization (ATRP) technique. The synthesis strategy involved three steps. Firstly, the nano-TiO₂ was modified by 3-(trimethoxysilyl) propylmethacrylate (MPS). Secondly, the modified nanoparticles were dispersed in 4-chloromethyl styrene monomers and subsequently polymerized by a free-radical in situ polymerization reaction to yield PCMSt/TiO₂ nanocomposite. Finally, poly (4-vinylpyridine) was grafted from PCMSt/TiO₂ macroinitiator via ATRP technique with the catalysts of 2,2′-bipyridine (Bpy) and Cu(I)Br in toluene as the solvent. TGA results indicated that no polymers adsorbed noncovalently onto the surface of TiO₂ nanoparticles. Also FT-IR spectra and TEM images investigation provided direct and clear evidence for the presence of PCMSt and (PCMSt-g-P4VP) shell on nano-TiO₂ core particles. Ultraviolet–visible spectroscopy (UV-Vis) investigated that these nanocomposites have improved optical properties potentially acting as visually transparent UV filters.     

PANI-chitosan-TiO2 ternary nanocomposite and its effectiveness on antibacterial and antistatic behavior of epoxy coating

A straightforward approach has been developed for fabricating antibacterial and antistatic epoxy coatings by using polyaniline-chitosan modified TiO₂ ternary nanocomposite. This nanocomposite was synthesized through the following steps. First, chitosan was grafted onto the TiO₂ nanoparticles and then final nanocomposite was prepared via solution polymerization of aniline. Electrical conductivity measurement revealed that nanocomposite with 7.5 wt % of the modified TiO₂ nanoparticles has noticeably higher conductivity compared to polyaniline. Evaluating the coatings' antibacterial property indicated epoxy coatings with the content of ternary nanocomposite show significant bactericidal activity against Gram-positive bacteria and have acceptable antibacterial action against Gram-negative ones. Also, obtained results showed that the ternary nanocomposite would greatly decrease coatings' surface resistivity and when nanocomposite content is about 2 wt % surface resistivity is about 3 × 10⁷ Ω sq⁻¹. On the contrary, the coating with nanocomposite loading exhibits improved thermal and mechanical performance compared to the coating made of neat epoxy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47629.     

Effect of poly(ethylene‐co‐vinyl acetate) additive on mechanical properties of maleic anhydride‐grafted acrylonitrile butadiene styrene for coating applications

The Izod impact strength of maleic anhydride‐grafted acrylonitrile butadiene styrene (MA‐g‐ABS) copolymer has been improved by the use of rubbery poly(ethylene‐co‐vinyl acetate) (EVA). The MA‐g‐ABS is prepared by an internal mixer using dicumyl peroxide as free radical initiator, and the grafting degree was determined using back‐titration method. The amount of EVA is optimized by evaluating the Izod impact strength, tensile, and flexural properties of the samples. Addition of 6% EVA into MA‐g‐ABS system improved the Izod impact strength and tensile strength by 18% and 35%, respectively. The miscibility of EVA in ABS and MA‐g‐ABS matrices has been observed using differential scanning calorimetry and scanning electron microscopy techniques. The enhanced adhesion property exhibited by MA‐g‐ABS/EVA systems promises it as a good candidate for thermoplastic coating applications on aluminum substrates. J. VINYL ADDIT. TECHNOL., 25:287–295, 2019. © 2018 Society of Plastics Engineers     

Effect of organic modifiers and silicate type on filler dispersion,thermal, and mechanical properties of ABS‐clay nanocomposites

Acrylonitrile–butadiene–styrene (ABS)–clay composite and intercalated nanocomposites were prepared by melt processing, using Na‐montmorillonite (MMT), several chemically different organically modified MMT (OMMT) and Na‐laponite clays. The polymer–clay hybrids were characterized by WAXD, TEM, DSC, TGA, tensile, and impact tests. Intercalated nanocomposites are formed with organoclays, a composite is obtained with unmodified MMT, and the nanocomposite based on synthetic laponite is almost exfoliated. An unintercalated nanocomposite is formed by one of the organically modified clays, with similar overall stack dispersion as compared to the intercalated nanocomposites. T_g of ABS is unaffected by incorporation of the silicate filler in its matrix upto 4 wt % loading for different aspect ratios and organic modifications. A significant improvement in the onset of thermal decomposition (40–44°C at 4 wt % organoclay) is seen. The Young's modulus shows improvement, the elongation‐at‐break shows reduction, and the tensile strength shows improvement. Notched and unnotched impact strength of the intercalated MMT nanocomposites is lower as compared to that of ABS matrix. However, laponite and overexchanged organomontmorillonite clay lead to improvement in ductility. For the MMT clays, the Young's modulus (E) correlates with the intercalation change in organoclay interlayer separation (Δd₀₀₁) as influenced by the chemistry of the modifier. Although ABS‐laponite composites are exfoliated, the intercalated OMMT‐based nanocomposites show greater improvement in modulus. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of epoxy resin on the properties of maleic anhydride functionalized acrylonitrile–butadiene–styrene copolymer toughened polyamide 6 blends

Maleic anhydride functionalized acrylonitrile–butadiene–styrene copolymer (ABS‐g‐MA) was used as an impact modifier of polyamide 6 (PA6). Epoxy resin was introduced into PA6/ABS‐g‐MA blends to further improve their properties. Notched Izod impact tests showed that the impact strength of PA6/ABS‐g‐MA could be improved from 253 to 800 J/m with the addition of epoxy resin when the ABS‐g‐MA content was set at 25 wt %. Differential scanning calorimetry results showed that the addition of epoxy resin made the crystallization temperature and melting temperature shift to lower temperatures; this indicated the decrease in the PA6 crystallization ability. Dynamic mechanical analysis testing showed that the addition of epoxy resin induced the glass‐transition temperature of PA6 and the styrene‐co‐acrylonitrile copolymer phase to shift to higher temperatures due to the chemical reactions between PA6, ABS‐g‐MA, and epoxy resin. The scanning electron microscopy results indicated that the ABS‐g‐MA copolymer dispersed into the PA6 matrix uniformly and that the phase morphology of the PA6/ABS‐g‐MA blends did not change with the addition of the epoxy resin. Transmission electron microscopy showed that the epoxy resin did not change the deformation mechanisms of the PA6/ABS‐g‐MA blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Application of nanostructured titanium dioxide pigments in paper coating: a comparison between prepared and commercially available ones

Nano-TiO₂ pigments in pure crystallographic anatase and rutile phases have been successfully prepared by hydrothermal at 120°C and hydrolysis methods, respectively. The laboratory-prepared pigments were characterized parallel to two commercial pigments of the same crystal structure. All pigments were applied in paper coating mixtures, and their influence on coated paper properties was systematically investigated. X-ray diffraction investigation showed that the laboratory-prepared pigments using the hydrothermal method at 120°C were pure anatase, whereas hydrolysis method produced pure rutile phase pigment. The application of the prepared nanopigments and the corresponding commercial TiO₂ phases in paper coating revealed that clay/rutile nano-TiO₂ pigments in paper coating mixture decreased coated paper roughness more than blending clay with anatase nano-TiO₂ pigments. Commercial nano-TiO₂ pigments increased porosity of coated paper at both the 30% and 50% addition of nano-TiO₂ pigments to clay, while laboratory-prepared nano-TiO₂ pigments highly decreased it at 30% addition of nano-TiO₂ to clay, compared to clay only. Blending of clay/nano-TiO₂ pigments improved both brightness and opacity of the coated paper where commercial pigments are more effective. Burst, tensile strength, stretching, and TEA were improved in the case of all pigments. The 50% addition of the prepared and commercial nanopigments in conjunction with clay improved the mechanical coated paper properties more than 30% addition (except the cases of stretching and TEA of the commercial pigments). The coated paper samples were offset printed. It was found that blending of clay/nano-TiO₂ pigments improved print density. Commercial nano-TiO₂ pigments improved print gloss more than the laboratory-prepared ones. This result was found consistent with the results of coated paper roughness.     

Synthesis and characterization of novel type poly (4-chloromethyl styrene-grft-4-vinylpyridine)/TiO2 nanocomposite via nitroxide-mediated radical polymerization

This paper describes the synthesis and characterization of novel type poly (4-chloromethyl styrene-graft-4-vinylpyridine)/TiO₂ nanocomposite. Firstly, poly (4-chloromethyl styrene)/TiO₂ nanocomposite was synthesized by in situ free radical polymerizing of 4-chloromethyl styrene monomers in the presence of 3-(trimethoxysilyl) propylmethacrylate (MPS) modified nano-TiO₂. Thereafter, 1-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO-OH) was synthesized by the reduction of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). This functional nitroxyl compound was covalently attached to the poly (4-chloromethyl styrene)/TiO₂ with replacement of chlorine atoms in the poly (4-chloromethyl styrene) chains. The controlled graft copolymerization of 4-vinylpyridine was initiated by poly (4-chloromethyl styrene)/TiO₂ nanocomposite carrying TEMPO groups as a macroinitiators. The coupling of TEMPO with poly (4-chloromethyl styrene)/TiO₂ was verified using ¹H nuclear magnetic resonance (NMR) spectroscopy. The obtained nanocomposites were studied using transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectra, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and the optical properties of the nanocomposites were studied using ultraviolet-visible (UV-Vis) spectroscopy.     

Composite latex production with high solid content

Poly(methyl methacrylate-co-butyl acrylate) (PMMA-co-PBA) and poly(sytrene-co-butyl acrylate) (PSt-co-PBA) latexes in which solid content (SC) varied from 20% up to 40 wt % armored with laponite clay have been successfully synthesized using a simple method, which does not require modification of the clay particles prior to polymerization. Incorporation of quite high amounts of laponite nanoparticles into PMMA-co-PBA and PSt-co-PBA latexes with a certain amount of solids content was achieved. The nanocomposite latexes and polymer samples were characterized using Fourier transform infrared (FTIR) spectroscopy in attenuated total reflectance (ATR) mode, dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), contact angle, zeta potential, viscosimetry and analytical ultracentrifuge (AUC). Zeta potential values showed that stable latex was obtained and precipitation problem of the nanoparticles in the latex was not seen during the storage. Obtained nanocomposite latex showed fine particle size between 88 and 160 nm. TEM images and XRD results pointed out that the exfoliated nanocomposite structure for latexes was obtained. DSC analyzes showed that the glass-transition temperature (T _g) values of nanocomposite films decreased slightly compared with those of pure (PMMA-co-PBA) films. Mechanical properties of laponite clay armored PMMA-co-PBA were tested and compared with those of pure PMMA-co-PBA, indicating that incorporated the Young's modulus and tensile strength are also improved to a noticeable extent after the incorporation of laponite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47423.     

Synthesis and characterization of epoxy based nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of the content and type of different clays on the structure and mechanical properties of the nanocomposites. Diglycidyl ether of bisphenol‐A (epoxy) was reinforced by 0.5–11 wt % natural (Cloisite Na⁺) and organically modified (Cloisite 30B) types of montmorillonite. SEM results showed that as the clay content increased, larger agglomerates of clay were present. Nanocomposites with Cloisite 30B exhibited better dispersion and a lower degree of agglomeration than nanocomposites with Cloisite Na⁺. X‐ray results indicated that in nanocomposites with 3 wt % Cloisite 30B, d‐spacing expanded from 18.4 Å (the initial value of the pure clay) to 38.2 Å. The glass transition temperature increased from 73°C, in the unfilled epoxy resin, to 83.5°C in the nanocomposite with 9 wt % Cloisite 30B. The tensile strength exhibited a maximum at 1 wt % modified clay loading. Addition of 0.5 wt % organically modified clay improved the impact strength of the epoxy resin by 137%; in contrast, addition of 0.5 wt % unmodified clay improved the impact strength by 72%. Tensile modulus increased with increasing clay loading in both types of nanocomposites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1081–1086, 2005     

Morphologies and properties of epoxy resin/layered silicate–silica nanocomposites

A new nanofiller containing layered organo‐modified montmorillonite (oMMT) and spherical silica (SiO₂) was prepared by an in situ deposition method and coupling agent modification. Fourier transform infrared spectrometry, X‐ray diffraction and transmission electron microscopy show that there are interactions between oMMT and SiO₂, and the spherical SiO₂ particles are self‐assembled on the edge of oMMT layers, forming a novel layered–spherical nanostructure. An epoxy resin (EP)/oMMT–SiO₂ nanocomposite was obtained by adding oMMT–SiO₂ to EP matrix. Morphologies and mechanical and thermal properties of the new ternary nanocomposite were investigated. For purposes of comparison, the corresponding binary nanocomposites, i.e., EP modified with either oMMT or SiO₂, were also tested. The results for the mechanical properties show that oMMT obviously improves the strength of EP, and SiO₂ enhances the toughness of EP, but oMMT–SiO₂ exhibits a synergistic effect on toughening and reinforcing of EP. The toughening and reinforcing mechanism is explained by scanning electron microscopy. In addition, the thermal resistance of EP/oMMT–SiO₂ is better than that of EP/SiO₂, but it is worse than that of EP/oMMT. Copyright © 2006 Society of Chemical Industry     

The Effect of Surface Modification of TiO2 with Diblock Copolymers on the Properties of Epoxy Nanocomposites

The TiO₂ nanoparticles were modified by diblock copolymers, poly(methyl methacrylate)-b-polystyrene (PMMA-b-PS), via reversible addition-fragmentation chain transfer (RAFT) polymerization, and the epoxy nanocomposites containing different TiO₂ and with different contents were prepared. Subsequently, the effects of TiO₂ content on the mechanical and thermal properties of nanocomposites were investigated. The results indicated that after grafting copolymers onto TiO₂, the dispersion of TiO₂ and interaction with epoxy matrix could be significantly increased, therefore, the mechanical properties of the nanocomposites were improved greatly. When the TiO₂-PMMA-b-PS content was 1 wt%, the impact strength and flexural strength reached their the best, and increased up to 96% and 43%, respectively. Furthermore, the thermal stability of the nanocomposites was also distinctly improved.     

New epoxy/silica‐titania hybrid materials prepared by the sol–gel process

A new type of inorganic‐polymer hybrid materials of epoxy/silica‐titania had been prepared by incorporating grafted epoxy, which had been synthesized by epoxy and tetraethoxysilane (TEOS), with highly reactive TEOS and tetrabutyltitanate (TBT) by using the in situ sol–gel process. The grafted epoxy was confirmed by Fourier transform infrared spectroscopy (FT‐IR) and ¹H‐NMR spectroscopic technique. Results of FT‐IR spectroscopy and atomic force microscopy (AFM) demonstrated that epoxy chains have been covalently bonded to the surface of the SiO₂‐TiO₂ particles. The particles size of SiO₂‐TiO₂ are about 20–50 nm, as characterized by AFM. The experimental results showed that the glass‐transition temperatures and the modulus of the modified systems were higher than that of the unmodified system, and the impact strength was enhanced by two to three times compared with that of the neat epoxy. The morphological structure of impact fracture surface and the surface of the hybrid materials were observed by scanning electron microscopy and AFM, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1075–1081, 2006     

Preparation of polyethylene‐octene elastomer/clay nanocomposite and microcellular foam processed in supercritical carbon dioxide

Polyethylene‐octene elastomer (POE)/organoclay nanocomposite was prepared by melt mixing of the POE with an organoclay (Cloisite 20A) in an internal mixer, using poly[ethylene‐co‐(methyl acrylate)‐co‐(glycidyl methacrylate)] copolymer (E‐MG‐GMA) as a compatibilizer. X‐ray diffraction and transmission electron microscopy analysis revealed that an intercalated nanocomposite was formed and the silicate layers of the clay were uniformly dispersed at a nanometre scale in the POE matrix. The nanocomposite exhibited greatly enhanced tensile and dynamic mechanical properties compared with the POE/clay composite without the compatibilizer. The POE/E‐MA‐GMA/clay nanocomposite was used to produce foams by a batch process in an autoclave, with supercritical carbon dioxide as a foaming agent. The nanocomposite produced a microcellular foam with average cell size as small as 3.4 µm and cell density as high as 2 × 10¹¹ cells cm^?3. Copyright © 2005 Society of Chemical Industry     

Blended Epoxy/Polyester Polymer Nanocomposites: Effect of “Nano” on Mechanical Properties

The inter-cross-linked networks of unsaturated polyester (UP) toughened epoxy blends were developed. Montmorillonite (MMT) clay was dispersed into the same system to prepare blended epoxy/UP/clay nanocomposites in different weight ratios viz. 0%, 1%, 2%, 3% and 5%. Mechanical properties like tensile strength (TS), impact strength (IS) and interlaminar shear strength (ILSS) were characterized for the above nanocomposites. Blended nanocomposites were fabricated by high shear mechanical mixing followed by ultra-sonication process to get homogeneous mixing under the aid of in situ polymerization. Mechanical properties were studied as per ASTM standards. Data obtained from mechanical property studies indicated that the introduction of UP into epoxy resin improved the impact strength to an appreciable extent. Impact strength (IS) and tensile strength (TS) were significantly improved and optimized at 3 wt. % clay content when compared with neat blend (0 wt. % clay) composites. The homogeneous morphologies of the UP toughened epoxy and epoxy/UP/clay nanocomposite systems were ascertained using scanning electron microscope (SEM) studies.     

Preparation of a layered hexaniobate–titania nanocomposite and its photocatalytic activity on removal of phenol in water

A nanocomposite photocatalyst of two photocatalytically active semiconductor oxides was prepared by flocculation of exfoliated layered hexaniobate K₄Nb₆O₁₇ with TiO₂ fine particles in presence of acid electrolyte, and evaluated as photocatalyst by using photodegradation of phenol as a test reaction. Disappearance of (0k0) peaks which correspond to the basal spacing in the X-ray diffraction (XRD) patterns of the nanocomposite suggested that the exfoliated niobate nanosheets were randomly hybridized with TiO₂ particles without restacking to the layered structure. Scanning electron microscopy revealed that the nanocomposite was an agglomerate of closely packed niobate nanosheets and TiO₂ particles. The nanocomposite is mesoporous and has a specific surface area larger than those of the original K₄Nb₆O₁₇ and TiO₂ as indicated by N₂ adsorption–desorption isotherms. The increase in surface area is ascribed to the porous structure constructed by the exfoliated niobate nanosheets and TiO₂ particles. The photocatalytic activity of the porous nanocomposite was superior to those of K₄Nb₆O₁₇ and TiO₂ in terms of degradation of phenol.     

Fabrication and evaluation of light-curing nanocomposite resins filled with surface-modified TiO2 nanoparticles for dental application

A kind of light-curing nanocomposite resin, which consisted of reactive monomers, surface-modified TiO₂ nanoparticles and a photoinitiation system, has been developed for the application of dental restoration. It may be noted that the conjugation of glycidyl methylmethacrylate (GMA) onto the surface of TiO₂ nanoparticles (nano-TiO₂) contributed to improvement in miscibility between nano-filler and matrix, because the reactive C=C group of GMA participated in curing of the matrix, and hence resulted in the enhancement of mechanical properties. When the content of GMA-modified nano-TiO₂ was 2 wt%, the flexural strength and modulus of the nanocomposite resin reached 147.8 and 2918.3 MPa, respectively, which increased by 21.7 and 30.8 % in contrast to the resin without adding nano-filler. Furthermore, the polymerization shrinkage decreased after incorporating the nano-filler while the degree of monomer conversion and the water sorption for the nanocomposite resins was comparable with those of the resin without nano-filler. In conclusion, this study presented a new method, namely introduction of functional groups onto the nano-filler surface to participate in the reaction of resin monomer, to improve the interfacial adhesion and the resultant miscibility between nano-filler and resin matrix in light-curing dental nanocomposites by chemical linkage mediated with surface-modified specie. Moreover, the enhanced mechanical properties and decreased polymerization shrinkage of nanocomposite resins, which are considered the key to the effects of dental restoration, contributed a great potential as a dental material utilized for caries treatment and prevention.