INTERFACIAL ADHESION AND MECHANICAL PROPERTIES OF PMMA-COATED CaCO3 NANOPARTICLE REINFORCED PVC COMPOSITES

Polymethyl methacrylate （PMMA）-coated nano-CaCO3 particles were prepared by in-situ emulsion polymerization. The mechanical properties of nano-CaCO3 particles-reinforced PVC were investigated using an AG-2000A universal testing machine and an XJU-2.75 izod impact tester; interracial adhesion between CaCO3 nanoparticles and PVC matrix by SEM, and structure of PMMA coated on the surface of CaCO3 by FTIR and ^1H-NMR. The results indicate that the PMMA coated on the nano CaCO3 particles consists mainly of syndiotactic structure, and their three tacticity contents were rr 52.8%, mm 7.3% and mr 39.9%, respectively. The interfacial adhesion between CaCO3 nanoparticles and PVC matrix was significantly improved when the CaCO3 nanoparticles were coated with PMMA, which led to increased Young＇s moduli and tensile strengths of the PMMA-coated CaCO3/PVC composites. The izod impact strengths of the composites were strongly affected by the PMMA coating thickness and increased significantly with increasing the volume fraction of CaCO3 filler in the composites.     

Modification of silica with PMMA via ultrasonic irradiation and its application for reinforcement of polyacrylates

Polymethyl methacrylate （PMMA） encapsulated silica nanocomposite particles were prepared by ultra- sonically induced in situ polymerization of methyl methacrylate （MMA） on the surface of silica sol. The nanoparticles were characterized by Fourier transform infrared spectroscopy （FFIR）, transmission electron microscopy （TEM）, thermogravimetry （TG）, scanning electron microscopy （SEM）. The results showed that core-shell structure nanocomposite particles with an average size of 36 nm were obtained, and the thickness of polymer encapsulating layer was about 8 nm. The pretreatment of silica sol with tert-butyl hydroperoxide （TBHP） and the addition of ~-methacryloxypropyl trimethoxysilane （MAPTS） significantly enhanced the encapsulation effect. Modified by the polymer layer, the silica particles could be well dispersed in matrices and utilized to improve the mechanical performance of polyacrylates.     

Key synthesis of magnetic Janus nanoparticles using a modified facile method

Inorganic/organic poly（methylmethacrylate-acrylic acid-divinylbenzene） iron oxide Janus magnetic nanoparticles（P（MMA-AA-DVB）/Fe3O4） with strong magnetic domains and unique surface functionalities were prepared using a solvothermal process.The P（MMA-AA-DVB） nanoparticles were prepared via soapfree emulsion polymerization and used as a precursor for preparing Janus nanoparticles.The morphology and magnetic properties of the magnetic Janus nanoparticles formed were characterized using a laser particle size analyzer,transmission electron microscopy,Fourier transform infrared spectroscopy,vibrating sample magnetometry,and thermogravimetric analysis.The synthesized P（MMA-AA-DVB）/Fe3O4 magnetic Janus nanoparticles were characterized by a Janus structure and possessed a stable asymmetric morphology after being dually functionalized.The particle size,magnetic content,and magnetic domain of the P（MMA-AA-DVB）/Fe3O4 magnetic Janus nanoparticles were 200 nm,40%,and 25 emu/g,respectively.The formation mechanism of the Janus nanoparticles was also investigated,and the results revealed that the reduction of Fe3＋ ions and growth of Fe3O4 took place on the surface of the P（MMA-AA-DVB） polymeric precursor particles.The size of the Janus particles could be controlled by narrowing the size distribution of the P（MMA-AA-DVB） precursor nanoparticles.     

Embedding copper nanoparticle-anchored conductive nano-blocks in polyelectrolyte

Conductive carbon nanotubes （CNTs） or alternatively polyaniline （PANI） nano-blocks was introduced into aqueous solutions of polyvinyl alcohol （PVA） and copper （II） salt, to assist the reduction of copper （II） ions and the anchoring of the resulting copper nanoparticles onto the conductive blocks. The mixture solutions of nano-blocks, copper （lI） salts and PVA were spin-coated onto the cathode surface, forming swollen cathode films （SCFs）. The copper （II） ions in the film assembled onto the surfaces of the conductive blocks and were then reduced under an appropriate voltage. It is important that the copper nanoparticles grew only on the surfaces of the conductive blocks. PVA which acted as the matrix of the composites played a role in stabilizing the resulting copper nanoparticles. Morphologies of these polymeric composite films were studied by various characterization methods. Moreover, the mechanism of migration of copper （II） ions, the formation of these polymeric composites, and the overall procedure were investigated in detail.     

Characterization of gold]PMMA hybrid nanomaterials synthesized by hard X-ray synchrotron radiation

In this study, new types of hybrid gold poly（methyl methacrylate） （PMMA） nanomaterials are synthesized. Both PMMA spheres coated with gold nanoparticles and gold nanoparticles coated with PMMA can be synthesized using different ratios of HAuCl4 and MMA precursors, by exposing the mixtures to hard X-ray synchrotron radiation without the use of a reducing agent. According to the photochemical mechanism, gold nanoparticles will precipitate from a solution of HAuCl4 on exposure to synchrotron radiation, followed by the synthesis of PMMA by the polymerization of MMA monomers. These reactions can result in the formation of two different types of new hybrid nanomaterials. When a 1：1 volume ratio of HAuCI4 to MMA is used, we obtain PMMA spheres coated with gold nanoparticles. When a 10：1 ratio of HAuCl4 and MMA is used, we obtain gold nanoparticles coated with PMMA. The hybrid gold/PMMA nanostructures are characterized by transmission electron microscopy, elemental analysis, dynamic-light scattering analysis, gel permeation chromatography and Raman spectroscopy. The hybrid nanomaterials have potential application in the fields of biosensors and drug delivery.     

SYNTHESIS OF HIGH PURITY TiO2 NANOPARTICLES FROM Ti（SO4）2 IN PRESENCE OF EDTA AS COMPLEXING AGENT

TiO2 nanoparticles were synthesized by a homogeneous controlled precipitation method using industrial titanium sulfate （Ti（SO4）2）. The obtained powders were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM）, Fourier transform infrared spectroscopy （FTIR） and ICP plasma spectrometer. EDTA was used as complexing agent to improve the purity and the formation of TiO2 nanoparticles. Experimental results indicated that the high-purity TiO2 nanoparticles were 20 nm in mean size and nearly monodispersed.     

SYNTHESIS AND APPLICATION OF NANOPARTICLES BY A HIGH GRAVITY METHOD

Fast chemical reactions involved in nanomaterials synthesis, polymerization, special chemicals production, reactive absorption, etc., are often difficult to control in terms of product quality, process efficiency and production consistency.After a theoretical analysis on such processes based on chemical reaction engineering fundamentals, an idea to intensify micromixing (mixing on the molecular scale) and mass transfer and therefore to control the process ideally was proposed.By experimental investigations of mass transfer and micromixing characteristics in the Rotating Packed Bed (RPB, or “HIGEE“ device), we achieved unique intense micromixing. This led us to the invention of using RPB as a reactor for the fabrication of nanoparticles (Chen et al., 2000).RPB consists mainly of a rotating packed rotator inside a stationary casing. The high gravity environment created by the RPB, which could be orders of magnitude larger than gravity, causes aqueous reactants going through the packing to spread or split into micro or nano droplets, threads or thin films, thus markedly intensifying mass transfer and micromixing to the extent of 1 to 3 orders of magnitude larger than that in a conventional packed bed.In 1994, the first RPB reactor was designed to synthesize nanoparticles of CaCO3 through multiphase reaction between Ca(OH)2 slurry and CO2 gas, and nanoparticles of 15～30nm in mean size and with very uniform particle size distribution was obtained. In 1997, a pilot-scale RPB reactor was successfully set up for operation, and in 2000, the first commercial-scale RPB reactor for synthesis of such nanoparticles came into operation in China, establishing a milestone in the use of RPB as a reactor for the fabrication of nanomaterials (Chen et al., 2002).Since then, the high gravity method has been employed for the synthesis of inorganic and organic nanoparticles via gas-liquid, liquid-liquid, and gas-liquid-solid multiphase reactions, e.g. inorganic nanoparticles like nanosized CaCO3, TiO2,SiO2, ZnO, Al2O3, ZnS, BaTiO3, BaCO3, SrCO3, Al(OH)3 and Mg(OH)2 flame retardants, and organic nano-pharmaceuticals including benzoic acid, salbutamol sulfate and cephradine. This technology received extensive attention in the field of nanomaterials fabrication and application. Dudukovic et al. commented, “The first large-scale application of RPB as a reactor occurred in China in production of nano CaCO3 by HGRP (high gravity reactive precipitation)of carbon dioxide and lime. Uniformly small particles were made in the RPB due to achievement of a sharp supersaturation interface and very short liquid residence times in the device.“ (Dudukovic et al., 2002). Date et al. said, “HGRP represents a second generation of strategies for nanosizing of hydrophobic drugs. In our opinion, among various methodologies described eariier, supercritical anti-solvent enhanced mass transfer method and HGRP method has potential to become technologies of the future owing to their simplicity, ease of scale-up and nanosizing efficiency“ (Date et al., 2004).As-synthesized nano CaCO3 was employed as a template to synthesize silica hollow spheres (SHS) with mesostructured walls. Characterizations indicated that the obtained SHS had an average diameter of about 40 nm with a surface haviors of Brilliant Blue F (BB), which was used as a model drug. Loaded inside the inner core and on the surfaces of SHS,BB was released slowly into a bulk solution for as long as 1 140min as compared to only 10min for the normal SiO2nanoparticles, thus exhibiting a typical sustained release pattern without any burst effect. In addition, higher BET value of the carrier, lower pH value and lower temperature prolonged BB release from SHS, while stirring speed indicated little influence on the release behavior, showing the promising future of SHS in controlled drug delivery (Li et al., 2004).Nano-CaCO3 synthesized by the high gravity method was also employed as a filler to improve the performance of organic materials. By adding CaCO3 nanoparticles into polypropylene-ethylene copolymer (PPE) matrix, the toughness of the matrix was substantially increased. At a nanosized CaCO3 content of 12 phr (parts per hundred PPE resin by weight),matrix. In the nanosized CaCO3/PPE/SBS (styrene-butadiene-styrene) system, the rubbery phase and filler phase were independently dispersed in the PPE matrix. As a result of the addition of nanosized CaCO3, the viscosity of PPE matrix significantly increased. The increased shear force during compounding continuously broke down SBS particles, resulting in the reduction of the SBS particle size and improving the dispersion of SBS in the polymer matrix. Thus the toughening effect of SBS on matrix was improved. Simultaneously, the existence of SBS provided the matrix with good intrinsic toughness, satisfying the condition that nanosized inorganic particles of CaCO3 efficiently toughened the polymer matrix,thus fully exhibiting the synergistic toughening function of nanosized CaCO3 and SBS on PPE matrix (Chen et al., 2004).As-prepared nano-CaCO3 was blended with TiO2 and other additives to prepare complex master batches for use in the coloring of polypropylene. It was found that the obtained nano-CaCO3 is an excellent pigment dispersant, which can partially replace TiO2 pigments for polypropylene resin coloring. Nano-CaCO3 can prompt the dispersion of TiO2 in polymer matrix, boosting the whiteness of the materials without a negative effect on the UV absorbency of the materials (Guo et al.,2004). Studies on the mechanical properties of nano-CaCO3 toughened epoxy resin composite indicated that impact strength and flexural modulus of the composite improved remarkably when 6wt.% of nano-CaCO3 was added. Surface treatment of nano-CaCO3 by titanate coupling agents significantly improved the dispersibility of nano-CaCO3 in such a high viscous matrix (Li et al, 2005).     

Roles of polyacrylate dispersant in the synthesis of well-dispersed BaSO4 nanoparticles by simple precipitation

Well-dispersed BaSO4 nanoparticles were synthesized in the presence of sodium polyacrylate （PAAS） by a simple precipitation method, with BaCl2 and （NH4）2SO4 as reactants. The different roles performed by PAAS in the synthesis of BaSO4 nanoparticles were investigated using X-ray diffractometry, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicate that the assynthesized BaSO4 nanoparticles were spheres with an average diameter of 30 nm and that their surfaces were affected by the PAAS. Under a typical procedure employed, PAAS reacted with BaCl2 to yield an intermediate, serving as a control releasing agent and separating the nucleation and crystal growth processes of the BaSO4 nuclei. During formation of the BaSO4 nanospheres, the intermediate slowly dissolved and released barium and polyacrylate ions, inhibiting the growth and aggregation of newly formed BaSO4 seeds and resulting in particles of narrow diameter distribution and improved dispersibility. Moreover, these polyacrylate ions further modified the surfaces of the BaSO4 nanoparticles.     

Preparation of polyacrylamide/silica composite capsules by inverse Picketing emulsion polymerization

Polyacrylamide/silica （PAM/SiO2） composite capsules were synthesized by inverse Pickering emulsion polymerization. Silica nanoparticles modified with methacryloxypropyltrimethoxysilane （MPS） were used as a stabilizer. Transmission electron microscopy （TEM）, scanning electron microscopy （SEM）. Fourier transform infrared （FTIR） spectroscopy, and thermal gravimetric analysis （TGA） were used to characterize the morphology and composition of the composite capsules. SEM and TEM images showed that capsules consisted of a particle shell and a polymer inner layer. The capsule size depends on the nanoparticle concentration in the continuous phase. The composite rigidity largely depends on the acrylamide concentration. FTIR and TGA results indicated the existence of polyacrylamide and SiO2 in the composite particles. Aqueous Hg（ll） removal testing by the PAM/SiO2 composite capsules indicated promising potential for removing heavy metal ions from wastewater.     

MECHANICAL PERFORMANCE OF NANO-CaCO_3 FILLED POLYSTYRENE COMPOSITES

Nano-CaCO3 incorporated polystyrene composites are compounded by twin-screw extrusion. Tensile and compact tensile tests show that the strength and toughness of polystyrene are decreased after the addition of nano-CaCO3 particles. Fracture surface analysis suggests that the defects induced by interfacial debonding and nano-filler agglomerations would be the key factors responsible for the declined strength and toughness. Nevertheless, it has to be stated, if the applied stress is lower than the ultimate strength, the rigid nanoparticles would still stiffen the polymer molecules, and resist polymer chain mobility. Hence, the improved tensile modulus and creep resistance can be obtained with the increasing contents of nanoparticles.     

Synthesis and characterization of PMMA/Al2O3 composite particles by in situ emulsion polymerization

In order to improve its dispersibility, superfine alumina （A1203） was encapsulated with poly（methyl methacrylate） （PMMA） by in situ emulsion polymerization. It was found that only when the concentration of sodium dodecyl sulfate （SDS） was much higher than its critical micelle concentration, could PMMA/Al2O3 composite particles with high percentage of grafting （PG） be prepared. The same results were obtained between the experimental and stoichiometric amounts of tris（dodecylbenzenesulfonate） isopropoxide （NDZ）, indicating that single-molecule-layer adsorption had taken place between NDZ and Al2O3. Analysis using FTIR, TEM and XPS showed that PMMA/Al2O3 composite particles with core-shell structure had been successfully synthesized by in situ emulsion polymerization. Compared to Al2O3, thermal stability and dispersibility of the composite particles showed marked improvement.     

Synthesis and photoluminescence properties of zinc sulfide nanoparticles doped with copper using effective surfactants

Zinc sulfide（ZnS）,various concentrations of Cu²⁺（0.25%-1.25%）-doped ZnS and ZnS:Cu²⁺ nanoparticles capped with various surfactants have been successfully synthesized by a chemical precipitation method in ambient air at 80℃.The synthesized particles were characterized by UV-visible absorption（UV-vis）,X-ray diffraction（XRD）,transmission electron microscopy（TEM）,and Fourier transform infrared（FT-IR）and photoluminescence（PL） spectroscopy.The absorption peaks of the synthesized nanoparticles were noticeably blue-shifted from the bulk material.The XRD analysis confirmed the formation of a cubic phase for all samples.The average size of the particles ranged from 3.2 to 5.3 nm.The TEM analysis showed that the particles were highly monodispersed and spherical in shape.Particles with increased Cu²⁺ concentrations had a red shift in their PL emission spectra.Enhanced PL emissions were observed for surfactant-capped particles.The experimental results indicate that,as expected,the PL spectrum confirms the presence of Cu²⁺ ions in the ZnS nanoparticles.     

Influence of suspension stability on wet grinding for production of mineral nanoparticles

Grinding behavior of nanoparticles in an attritor mill and the minimum achievable particle size are strongly influenced by the suspension stability. In the present work, suspension stability （i.e. ξ-potential） of nanoparticles was studied by measuring pH as a function of grinding time in the wet milling process. It was found that after a certain time in an attritor mill, there is no further size reduction and the average product particle size increases monotonically. One of the reasons is that the production of submicron particles leads to more particle-particle interactions and consequently pH of the suspension decreases with grinding time. Usually pH value is related to suspension stability and it can be enhanced by addition of NaOH solution. The maximum negative ξ-potential of -51.2 mV was obtained at pH of 12 for silica. The higher the ξ-potential with the same polarity, higher will be the electrostatic repulsion between the particles. Hence, the maximum electrostatic repulsion force was maintained by the adjustment ofpH value in wet milling. The experiments were conducted at different pH conditions which were maintained constant throughout the experiments and nanosized particles were obtained consequently.     

Synthesis of PS/Ag asymmetric hybrid particles via phase separation and self-assembly

This article presents a facile approach to preparation of polystyrene/silver （PS/Ag） asymmetric hybrid par- ticles. In this method, polystyrene/polyglycidyl methacrylate （PS/PGMA） Janus particles were synthesized via internal phase separation triggered by evaporation of dichloromethane （DCM） from PS/PGMA/DCM- in water emulsion droplets. Then, the Janus particles were aminated and sequentially carboxylated to obtain PS/PGMA-NH2 and PS/PGMA-COOH particles. Ag＋ self-assembled on the surface of PGMA hemi- sphere of the functionalized PS/PGMA particles by coordinating with amine/carboxyl. PS/Ag asymmetric hybrid particles with 7.29 wt% of Ag were obtained by reduction of Ag＋, Scanning electron microscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy results confirmed that Ag was asymmetrically distributed on the surface of polymer particles.     

Intensified photocatalytic degradation of nitrobenzene by Picketing emulsion of ZnO nanoparticles

In this paper, zinc oxide nanoparticles were first prepared and surface-modified. A Pickering emulsion was then prepared, consisting of nitrobenzene （oil phase）, water （water phase） and the modified zinc oxide nanoparticles located on the water-oil interface. The effects of different emulsions on the removal rate of nitrobenzene by photocatalytic degradation were studied. The results proved that use of a Pickering emulsion stabilized by surface-modified ZnO nanoparticles provides an effective and novel way to intensify the photocatalytic degradation of the organic contaminant.     

Functionalized TiO2@ZrO2@Y2O3 ：Eu3＋ core-multishell microspheres and their photoluminescence properties

TiO2@ZrO2@Y2O3 ：Eu3＋ composite particles with a core-multishell structure were synthesized through the combination of a layer-by-layer （LBL） self-assembly method and a sol-gel process. The obtained sam- ples were characterized with scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, and fluorescence spectropho- tometry. The results showed that the composite particles had a core-multishell structure, spherical morphology, and a narrow size distribution. The presence of a ZrO2 layer on the TiO2 core can effec- tively prevent the reaction between the TiO2 core and a Y203 shell; the temperature for the reaction between the TiO2 core and the Y203 shell in the TiO2@ZrO2@Y2O3 ：Eu core-multishell phosphor can be elevated by 300 ℃ compared to that for TiO2@ZrO2：Eu. Upon excitation of the core-multishell particles in the ultraviolet （254 nm）, the Eu3＋ ion in the Y2O3 ：Eu3＋ shell shows its characteristic red emission （611 nm, 5D0→7F2）, and the photoluminescence （PL） intensity of the phosphor with the core-multishell structure was obviously greater than that of the core-shell TiO2@Y2O3 ：Eu phosphor.     

Controlled preparation and characterization of nano-sized hexagonal Mg（OH）2 flame retardant

Nano-sized hexagonal magnesium hydroxide （Mg（OH）2） with good dispersibility was synthesized by a double injection-hydrothermal method, utilizing polyvinylpyrrolidone （PVP） as an additive and with optimized processing parameters. SEM and BET analysis showed that the mean particle size and specific surface area of the Mg（OH）2 particles were 174 nm and 50.77 m^2/g, respectively. The FT-IR spectra and the XRD patterns showed that PVP was adsorbed on the surface of the Mg（OH）2 crystal, thus effectively limiting particle agglomeration and hindering crystal growth along the （1 01 ） plane. TGA showed a decrease in the decomposition temperature and an increase in the weight loss of the Mg（OH）2 particles due to addition of PV/.     

PHASE STRUCTURE OF W-DOPED NANO-TiO2 PRODUCED BY SOL-GEL METHOD

With Ti（OBu）4 as precursor, and HAc as complexing agent, pure and W-doped TiO2 gelatins were prepared by a sol-gel method. During the process of gel formation, metal ions were dispersed in the porous TiO2 matrix. Then, powders of nano-TiO2 and W-doped nano-TiO2 were prepared by drying, grinding and heat treatment at different temperatures. The grain size and structure of the samples, pure TiO2 and W-doped, and treated at different temperatures were studied by X-ray diffraction （XRD）, Beckman Coulter Sorption Analysis and TEM. Results showed that, with increasing temperature, the TiO2 transformed from anatase to rutile and the grain size increased. This transformation and grain growth of TiO2 could be retarded by doping with W.     

Controlled growth of silver nanoparticles in a hydrothermal process

A two-step synthesis was used to control the shape of silver nanoparticles prepared via reduction of Ag^＋ ions in aqueous Ag（NH3）2NO3 by poly（N-vinyl-2 First, a few spherical silver nanoparticles,-10 nm in size, were pyrrolidone） （PVP）. Then, in a subsequent hydrothermal treatment, the remaining Ag^＋ ions were reduced by PVP into polyhedral nanoparticles, or larger spherical nanoparticles formed from the small spherical seed silver nanoparticles in the first step. The morphology and size of the resultant particles depend on the hydrothermal temperature, PVP/Ag molar ratio and concentration of Ag^＋ ions. By using UV-visible spectroscopy （UV-vis）, transmission electron microscopy （TEM） and powder X-ray diffraction （XRD）, the possible growth mechanism of the silver nanoparticles was discussed. 2007 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.     

Effect of mixing structure on the hygroscopic behavior of ultrafine ammonium sulfate particles mixed with succinic acid and levoglucosan

Understanding the interactions between water and atmospheric aerosols is critical for estimating their impact on the radiation budget and cloud formation. The hygroscopic behavior of ultrafine(100 nm)ammonium sulfate particles internally mixed with either succinic acid〔slightly soluble) or levoglucosan(soluble) in different mixing structures(core-shell vs. well-mixed) were measured using a hygroscopicity tandem differential mobility analyzer(HTDMA). During the hydration process(6-92% relative humidity(RH)), the size of core-shell particles(ammonium sulfate and succinic acid) remained unchanged until a s|ow increase in particle size occurred at 79% RH; however, an abrupt increase in size(i.e., a clear deliquescence) was observed at ~72% RH for well-mixed particles with a similar volume fraction to the core-shell particles(80:20 by volume). This increase might occur because the shell hindered the complete dissolution of the core-shell particles below 92% RH. The onset RH value was lower for the ammonium sulfate/levoglucosan core-shell particles than the ammonium sulfate/succinic acid core-shell particles due to levoglucosan's higher solubility relative to succinic acid. The growth factor(GF) of the core-shell particles was lower than that of the well-mixed particles, while the GF of the ammonium sulfate/levoglucosan particles was higher than that of ammonium sulfate/succinic acid particles with the same volume fractions. As the volume fraction of the organic species increased, the GF decreased. The data suggest that the mixing structure is also important when determining hygroscopic behavior of the mixed particles.