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1.
To more accurately investigate the nucleation, crystallization and dispersion behaviors of silica particles in polymers, the composites of PET with monodisperse SiO 2-PS core-shell structured particles were prepared with SiO 2 size from 380 nm to 35 nm.For these SNPET samples, DSC results showed that the nucleation rate of silica particles increased as their size decreased, in which 35 nm SiO 2 particles produced the most obvious nucleation effect. At 2.0 wt.% load of 35 nm silica, Avrami equation proved that the isothermal crystallization rate G of SNPET was ca. 30% higher than that of pure PET and the crystallization activation energy for SNPET was −218.7 kJ mol −1 lower than −196.1 kJ mol −1 for PET. While, the non-isothermal crystallization Δ E for SNPET was −199.8 kJ mol −1 lower than −185.5 for PET.On non-isothermal crystallization, Jeziorny equation presented the primary and secondary crystallization stages in PET and SNPET, in which nano SiO 2 accelerated the crystallization rate. Their Ozawa number m was from 2.1 to 2.7, which was smaller than that of Avrami number n.The nucleation and dispersion behaviors of SiO 2 particles were directly observed. POM results demonstrated that SNPET samples crystallized more quickly from melt and their crystallization rate increased as silica load increases but accelerated at 2-3 wt.%. The spherulites grew well in PET but their size was smaller in SNPET due to the silica barrier on their growth. SEM and TEM observed the homogeneous silica dispersion morphology and the vivid ordered patterns formed in SNPET. The monodisperse particles are highly expected to give more accurate and valuable references than multi-scale ones in obtaining novel advanced PET composites. 相似文献
2.
A core–shell nanosilica (nano‐SiO 2)/fluorinated acrylic copolymer latex, where nano‐SiO 2 served as the core and a copolymer of butyl acrylate, methyl methacrylate, and 2,2,2‐trifluoroethyl methacrylate (TFEMA) served as the shell, was synthesized in this study by seed emulsion polymerization. The compatibility between the core and shell was enhanced by the introduction of vinyl trimethoxysilane on the surface of nano‐SiO 2. The morphology and particle size of the nano‐SiO 2/poly(methyl methacrylate–butyl acrylate–2,2,2‐trifluoroethyl methacrylate) [P(MMA–BA–TFEMA)] core–shell latex were characterized by transmission electron microscopy. The properties and surface energy of films formed by the nano‐SiO 2/P(MMA–BA–TFEMA) latex were analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, and static contact angle measurement. The analyzed results indicate that the nano‐SiO 2/P(MMA–BA–TFEMA) latex presented uniform spherical core–shell particles about 45 nm in diameter. Favorable characteristics in the latex film and the lowest surface energy were obtained with 30 wt % TFEMA; this was due to the optimal migration of fluorine to the surface during film formation. The mechanical properties of the films were significantly improved by 1.0–1.5 wt % modified nano‐SiO 2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
3.
Nano-silica dispersion was generated in situ through the hydrolysis and condensation of tetraethyl orthosilicate with methyl methacrylate and butyl acrylate in micelles as dispersing media, hydrochloric acid as catalyst and methacryloxypropyl trimethoxysilane as modifier. Then, the nano-silica/fluorinated polyacrylate composite latexes were prepared via emulsion polymerization directly using the in situ generated nano-silica dispersion as seeds. Dodecafluoroheptyl methacrylate (DFHMA) as functional monomer was incorporated into shell layer of the composite particles by semi-continuous starved condition at the second stage. Fourier transform infrared spectroscopy indicated that silica was generated in situ and DFHMA took part in the copolymerization. Transmission electron microscopy showed uniform composite latex particle morphology and obvious core–shell structure. Dynamic light scattering demonstrated that DNS-86 could control the composite latex particle size ranging from 90 to 180 nm. DFHMA had an important effect on the particle size. Zeta potential (ζ) revealed that the composite latex had good stability. The resulted composite films were characterized by angle-resolved X-ray photoelectron spectroscopy, contact angle measurements and thermo-gravimetric analysis. The well-tailored composite latex particle structure of nano-silica core and fluorinated polyacrylate can effectively improve the hydrophobicity of the resultant films. Water contact angle could reach 123.5° when 6 wt% DFHMA was incorporated in the film. Moreover, water contact angles remained 106° after water immersion in the range of the experimental sample films. In addition, the incorporation of fluorinated monomer and nano-silica contributed to the improvement of thermal stability of the composite film. 相似文献
4.
Nanocomposite particles of poly(chlorotrifluoroethylene‐ co‐ethylvinyl ether) [poly(CTFE‐ co‐EVE)]/poly(styrene acrylate) (PSA)/SiO 2 were prepared with poly(CTFE‐ co‐EVE)/PSA [CS(FS); core–shell (CS) fluoro surfactant (FS)] and hydrophilic SiO 2 nanoparticles by a solution mixing method. This method yielded a homogeneous dispersion of hydrophilic SiO 2 nanoparticles in the CS(FS) matrix. The nanocomposite particle composition was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis. A slight improvement in the thermal stability was observed and the glass‐transition temperature of the nanocomposite particles increased compared with the CS(FS) matrix. A remarkable enhancement was observed in the mechanical properties with an increase in the tensile strength from 1.1 to 6.2 MPa and with an increase in the elongation at break from 209.6 to 350.1% for the films with 15 wt % SiO 2. The presence of a wettable PSA shell on the fluorocore made interaction possible with SiO 2; this made it more hygroscopic with a decent water uptake capacity and an enhanced water contact angle. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012 相似文献
5.
This study is focused on the development of high‐performance composite materials based on nano silicon dioxide (nano‐SiO 2) modified by polydopamine (PDA). A facile one‐step method was developed to synthesize core–shell structured SiO 2@polydopamine (PDA) nanospheres. During the synthesis, a PDA shell was simultaneously coated on the SiO 2 nanospheres to form the core–shell nanostructure which was blended with polypropylene (PP) and β nucleating agent (β‐NA) to enhance both mechanical and hydrophilic properties. Nano‐SiO 2 particles modified by PDA (SiO 2@polydopamine) influence the crystallization of PP seriously. The results indicated that when 1%wt SiO 2@polydopamine was added, the impact strength of composite reached the maximum value 12.60k J/m 2 increasing 137% compared with PP, the bending strength and bending modulus decreased slightly reaching 41.85 MPa, and 2192 MPa, respectively, the composite possessed hydrophilic performance with the water contact angle of 88.32°. β nucleating agent was used in all formulations, the synergistic effect toward mechanical properties with SiO 2@polydopamine was studied. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45004. 相似文献
6.
In this study, PVA‐SiO 2 was synthesized by modifying silica (SiO 2) with polyvinyl alcohol (PVA), then a novel polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane was prepared by incorporating the prepared PVA‐SiO 2 into membrane matrix using the non‐solvent induced phase separation (NIPS) method. The effects of PVA‐SiO 2 particle on the properties of the PVDF membrane were systematically studied by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT‐IR), surface pore size, porosity, and water contact angle. The results indicated that with the addition of PVA‐SiO 2 particles in the PVDF UF membranes, membrane mean pore size increased from 80.06 to 126.00 nm, porosity improved from 77.4% to 89.1%, and water contact angle decreased from 75.61° to 63.10°. Furthermore, ultrafiltration experiments were conducted in terms of pure water flux, bovine serum albumin (BSA) rejection, and anti‐fouling performance. It indicated that with the addition of PVA‐SiO 2 particles, pure water flux increased from 70 to 126 L/m 2 h, BSA rejection increased from 67% to 86%, flux recovery ratio increased from 60% to 96%, total fouling ratio decreased from 50% to 18.7%, and irreversible fouling ratio decreased from 40% to 4%. Membrane anti‐fouling property was improved, and it can be expected that this work may provide some references to the improvement of the anti‐fouling performance of the PVDF ultrafiltration membrane. POLYM. ENG. SCI., 59:E412–E421, 2019. © 2018 Society of Plastics Engineers 相似文献
7.
The contact angle of ultrafine size particles has been evaluated using 1 µm monosize SiO 2 particles of various degrees of wettability. The contact angle was determined by film flotation and Zisman plots. Chlorotrimethylsilane (CTS) was used to methylate the SiO 2 particle surface and establish the level of surface wettability. Also, the vacuum floatability of the methylated ultrafine SiO 2 particles was assessed to correlate it to the contact angle. This vacuum floatability was very low below 40º and increased monotonically above this contact angle value because of favorable bubble nucleation and a greater stability of the bubbles on the hydrophobic surface. Free energy of bubble nucleation on the hydrophobic surfaces has been estimated and correlated to the vacuum floatability of the ultrafine particles. 相似文献
8.
Core–shell particles preserve the performance (e.g. magnetic, plasmonic or opacifying) of a core material, while modifying its surface with a shell that facilitates (e.g. by blocking its reactivity) their incorporation into a host liquid or polymer matrix. Here coating of titania (core) aerosol particles with thin silica shells (films or layers) is investigated at non-isothermal conditions by a trimodal aerosol dynamics model, accounting for SiO 2 generation by gas phase and surface oxidation of hexamethyldisiloxane (HMDSO) vapor, coagulation and sintering. After TiO 2 particles have reached their final primary particle size (e.g. upon completion of sintering during their flame synthesis), coating starts by uniformly mixing them with HMDSO vapor that is oxidized either in the gas phase or on the particles’ surface resulting in SiO 2 aerosols or deposits, respectively. Sintering of SiO 2 deposited onto the core TiO 2 particles takes place transforming rough into smooth coating shells depending on the process conditions. The core–shell characteristics (thickness, texture and efficiency) are calculated for two limiting cases of coating shells: perfectly smooth (e.g. hermetic) and fractal-like. At constant TiO 2 core particle production rate, the influence of coating weight fraction, surface oxidation and core particle size on coating shell characteristics is investigated and compared to pertinent experimental data through coating diagrams. With an optimal temperature profile for complete precursor conversion, the TiO 2 aerosol and SiO 2-precursor (HMDSO) vapor concentrations have the strongest influence on product coating shell characteristics. 相似文献
9.
A facile method to prepare superhydrophobic fluoropolymer/SiO 2 nanocomposites coating on polyester (PET) fabrics was presented. The vinyl nanosilica (V? SiO 2) hydrosols were prepared via one‐step water‐based sol‐gel reaction with vinyl trimethoxy silane as the precursors in the presence of the base catalyst and composite surfactant. Based on the V? SiO 2 hydrosol, a fluorinated acrylic polymer/silica (FAP/SiO 2) nanocomposite was prepared by emulsion polymerization. The FAP/SiO 2 nanocomposites were coated onto the polyester fabrics by one‐step process to achieve superhydrophobic surfaces. The results showed that silica nanoparticles were successfully incorporated into the FAP/SiO 2 nanocomposites, and a specific surface topography and a low surface free energy were simultaneously introduced onto PET fibers. The prepared PET fabric showed excellent superhydrophobicity with a water contact angle of 151.5° for a 5 μL water droplet and a water shedding angle of 12° for a 15 μL. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40340. 相似文献
10.
Structured latex particles with a slightly crosslinked poly(styrene‐ n‐butyl acrylate) (PSB) core and a poly(styrene–methacrylate–vinyl triethoxide silane) (PSMV) shell were prepared by seed emulsion polymerization, and the latex particle structures were investigated with Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, transmission electron microscopy, and dynamic light scattering. The films that were formed from the structured core (PSB)–shell (PSMV) particles under ambient conditions had good water repellency and good tensile strength in comparison with films from structured core (PSB)–shell [poly(styrene–methyl methyacrylate)] latex particles; this was attributed to the self‐crosslinking of CH 2?CH? Si(OCH 2CH 3) 3 in the outer shell structure. The relationship between the particle structure and the film properties was also investigated in this work. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1824–1830, 2006 相似文献
11.
High-resolution scanning transmission electron microscopy is used to examine the structures of 20- to 200-Å-diameter Pt-Rh alloy particles on planar amorphous SiO 2 substrates following treatment in N 2 and air at one atmosphere and temperatures up to 1000 °C. Heating in N 2 produces only alloy particles at all temperatures, while heating particles in air above 400 °C produces a rhodium oxide layer around each particle. As temperature is increased above ~600 °C the oxide appears to migrate onto the SiO 2 substrate to form a thin oxide layer surrounding the metal core. The oxide is identified as Rh 2O 3 by electron diffraction, and dark field imaging confirms the morphology postulated. Pure Rh particles are completely oxidized by 600 °C and remain stable to at least 1000 °C. Continuous 10-Å-thick films of Rh or Pt-Rh cannot be broken up into particles below ~700 °C by heating in air because the oxide film is stable and adheres strongly to the SiO 2. This alloy system is quite different than Pt-Pd in that the oxide forms as a thin Rh 2O 3 layer around each particle for Rh, while for Pd, a PdO crystallite nucleates at the side of the metal crystallites. Both oxides adhere strongly to SiO 2, but the nucleation and growth of Rh 2O 3 is evidently much different than PdO. 相似文献
12.
A facile and novel strategy was reported on the fabrication of raspberry‐like SiO 2/polystyrene (SiO 2/PS) composite particles by emulsion polymerization in the presence of vinyl‐functionalized silica (vinyl‐SiO 2) particles, which were prepared via a one‐step sol–gel process using vinyltriethoxysilane as the precursor. The submicron vinyl‐SiO 2 particles were used as the core, and nanosized PS particles were then adsorbed onto the vinyl‐SiO 2 particles to form raspberry‐like composite particles during the polymerization process. The composition, morphology, and structure of the vinyl‐SiO 2 particles and the SiO 2/PS hybrid particles were characterized by thermogravimetric analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy. Superhydrophobic surface can be constructed by directly depositing the raspberry‐like SiO 2/PS composite particles on glass substrate, and the water contact angle can be adjusted by the styrene/SiO 2 weight ratio. In addition, the superhydrophobic film possessed a strong adhesive force to pin water droplet on the surface even when the film was turned upside down. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers 相似文献
13.
Biodegradable films are used in a variety of applications, including packaging. However, their use is limited due to their high moisture and water sensitivity. In this work, cassava starch (CS) was blended with poly(vinyl alcohol) (PVA). Silica particles (SiO2) were incorporated to increase the hydrophobicity of the blend by intermolecular interaction through hydrogen bonding between the three components. Instead of a plasticizer or crosslinker, a small amount of triethylamine was added to eliminate residual acetate groups in PVA. The miscibility of CS and PVA phases was confirmed by smooth fracture surfaces and a single glass transition temperature. When SiO2 content was below 5% (wt), the particles were well dispersed in a continuous phase of polymer matrix. At this loading of SiO2, the increase in tensile strength was as high as 170% and in elongation-at-break, 250%. All loadings of SiO2 increased thermal stability of the blend films because silanol groups on the surface of SiO2 particles formed effective interfacial interactions with hydroxyl groups of the polymers. These interactions also prevented the ingress of water molecules, significantly increasing the hydrophobicity of the films. The water contact angle increased as high as 113° and moisture absorbency and water solubility were low. These highly hydrophobic, photodegradable, biodegradable CS/PVA/SiO2 films show great potential as a low-cost, eco-friendly material. 相似文献
14.
Polysilsesquioxanes (PSQ)-based core–shell fluorinated polyacrylate/silica hybrid latex coatings were synthesized with PSQ latex particles as the seeds, and methyl methacrylate, butyl acrylate, 3-(trimethoxysilyl) propyl methacrylate (MPS)-modified SiO 2 nanoparticles (NPs), 1H,1H,2H,2H-perfluorooctyl methacrylate (PFOMA) as the shell monomers by emulsifier-free miniemulsion polymerization. The results of Fourier transform IR spectroscopy, transmission electron microscopy, and dynamic light scattering suggested the obtained hybrid particles emerged with trilayer core–shell pattern. Contact angle analysis, x-ray photoelectron spectroscopy, and atom force microscopy results indicated that the hybrid film containing SiO 2 NPs showed higher hydrophobicity, lower surface free energy and water absorption, in comparison with the control system (without SiO 2 NPs). Compared with the control system, the hybrid latex film containing SiO 2 NPs in the fluorinated polyacrylate shell layer showed the higher content of fluorine atoms and a rougher morphology on the film surface. Additionally, thermogravimetric analysis demonstrated the enhanced thermostability of PSQ-based nanosilica composite fluorinated polyacrylate latex film. 相似文献
15.
Poly(methy methacrylate) (PMMA)‐SiO 2 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‐SiO 2 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‐SiO 2 nanoparticles showed spherical particles with a core‐shell morphology by TEM micrographs. A nanocomposite membrane from natural rubber (NR) and PMMA‐SiO 2 emulsion was studied for mechanical and thermal properties and pervaporation of water‐ethanol mixtures. PMMA‐SiO 2 nanoparticles which were uniformly dispersed in NR matrix, significantly enhanced mechanical properties and showed high water selectivity in permeate flux. Thus, the NR/PMMA‐SiO 2 hybrid membranes have great potential for pervaporation process in membrane applications. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers 相似文献
16.
A novel polyurethane (PU)‐SiO 2 core–shell particle dispersion was prepared by an acid‐catalyzed sol–gel process using cationic–nonionic PU particle as template. Results of average sizes, polydispersity index, and transmission electron microscope indicated that tetramethylorthosilicate were first diffused to the surface of PU particles, then occurring hydrolysis–condensation reaction to form core–shell particles. Antireflection coating formulation was prepared by as‐prepared core–shell particle dispersion and SiO 2 sol binder. After dip‐coating in the formulation, antireflection coating was formed on glass surface by calcination. Scanning electron microscopy images showed that pores had been formed inside coating after removing PU template particles, and the coating surface could be almost fully closed. In addition, ultraviolet–visible spectrophotometer analysis showed that the maximum transmittance of antireflection glasses can be as high as 98.6% at 548 nm. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45762. 相似文献
17.
In order to compare the various precursors of silica aerogels, three different precursors namely TMOS, TEOS and Na 2SiO 3 were studied in this paper. The property differences of the aerogels caused by the three precursors were discussed in terms of reaction process, gelation time, pore size distributions, thermal conductivity, SEM, hydrophobicity and thermal stability. It has been found that the gelation time of the silica gel is strongly dependent on the type of precursor used. During the surface modification process, organic groups were attached to the wet gel skeletons transforming the hydrophilic to the hydrophobic which were characterized by Fourier Transform Infrared spectroscopy (FTIR). It has been found that the contact angle of the Na 2SiO 3 and TMOS precursor based aerogels with water have the higher contact angle of 149° and whereas Na 2SiO 3 precursor based aerogel has the lower contact angle of 130°. The thermal conductivities of the Na 2SiO 3 and TMOS based aerogels have been found to be lower (0.025 and 0.030 W m ?1 K ?1, respectively) compared to the TEOS based (0.050 W m ?1 K ?1) aerogels. The pore sizes obtained from the N 2 adsorption measurements varied from 40 to 180, 70 to 190, and 90 to 200 nm for the TEOS, TMOS and Na 2SiO 3 precursor based aerogels, respectively. The scanning electron microscopy studies of the aerogels indicated that the Na 2SiO 3 and TMOS based aerogels show narrow and uniform pores while the particles of SiO 2 network are very small. On the other hand, TEOS aerogel show non-uniform pores such that the numbers of smaller size pores are less compared to the pores of larger size while the SiO 2 particles of the network are larger as compared to both Na 2SiO 3 and TMOS aerogels. Hence, the surface are of the aerogels prepared using TEOS precursor has been found to be the lowest (~620 m 2 g ?1) compared to the Na 2SiO 3 (~868 m 2 g ?1) and TMOS (~764 m 2 g ?1) aerogels. 相似文献
18.
The core‐shell polyacrylate latex particles containing fluorine and silicon in the shell were successfully synthesized by a seed emulsion polymerization, using methyl methacrylate (MMA) and butyl acrylate (BA) as main monomers, dodecafluoroheptyl methacrylate (DFMA), and γ‐(methacryloxy) propyltrimethoxy silane (KH‐570) as functional monomers. The influence of the amount of fluorine and silicon monomers on the emulsion polymerization process and the surface properties of the latex films were discussed, and the surface free energy of latex films were estimated using two different theoretical models. The emulsion and its films were characterized by particle size distribution (PSD) analysis, transmission electron microscopy (TEM), Fourier transform infrared spectrum (FTIR), nuclear magnetic resonance ( 1H‐NMR and 19F‐NMR) spectrometry, contact angle (CA) and X‐ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetry (TG) analysis. The results indicate that the average particle size of the latex particles is about 160 nm and the PSD is narrow, the synthesized latex particles exist with core‐shell structure, and a gradient distribution of fluorine and silicon exist in the latex films. In addition, both the hydrophobicity and thermal stability of the latex films are greatly improved because of the enrichment of fluorine and silicon at the film‐air interface, and the surface free energy is as low as 15.4 mN/m, which is comparable to that of polytetrafluoroethylene (PTFE). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
19.
Modified micro-emulsion polymerization was successfully used to synthesize a kind of ambient temperature self-crosslinking core–shell emulsion, consisting of polyacrylate core and vinyltriethoxysilane (VTES) modified polyacrylate shell, by varying the ratio of soft monomer (BA) and hard monomer (MMA) which is different in the core and shell. The emulsion and its film formed at ambient temperature were characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Core–shell structure was clearly shown in TEM micrographs, and two distinct glass transition temperatures ( T g) were confirmed by DSC analysis. Lower T g of core phase analyzed by DSC and self-crosslinking properties of VTES characterized by crosslinking degree cause latex particles form continuous film at ambient temperature. Thermal and mechanical properties and the surface properties of the latex films were also investigated. Results showed that the core–shell latex films containing 5 and 7.5 % VTES exhibited higher thermal stability, better mechanical properties, higher contact angle, and water resistance compared with pure polyacrylate film. 相似文献
20.
In this paper, a multilayer barrier thin film, based on polyvinylidene difluoride (PVDF)–silicon dioxide (SiO 2), has been fabricated on a PET substrate through a novel method of joint fabrication techniques. The inorganic SiO 2 thin film was deposited using a roll-to-roll atmospheric atomic layer deposition system (R2R-AALD), while the organic PVDF layer was deposited on the surface of SiO 2 through the electrohydrodynamic atomization (EHDA) technique. The multilayer barrier thin films exhibited very good surface morphology, chemical composition, and optical properties. The obtained values for arithmetic surface roughness and water contact angle of the as-developed multilayer barrier thin film were 3.88 nm and 125°, respectively. The total thickness of the multilayer barrier thin film was 520 nm with a high optical transmittance value (85–90%). The water vapor transmission rate (WVTR) of the barrier thin film was ~?0.9?×?10 ?2 g m ?2 day ?1. This combination of dual fabrication techniques (R2R-AALD and EHDA) for the development of multilayer barrier thin films is promising for gas barrier applications. 相似文献
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