聚四氟乙烯改性的丙烯酸酯复合乳液

用甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸等原料合成丙烯酸酯乳液。然后采用乳液聚合在丙烯酸酯中引入聚四氟乙烯(PTFE),得到聚四氟乙烯改性丙烯酸酯复合乳液。研究了不同乳化剂、引发剂和聚合工艺等对产品性能的影响,得到优化的反应条件。实验结果表明聚该复合乳液具有核壳结构且性能优异。     

PTFE–PMMA core–shell colloidal particles as building blocks for self‐assembled opals: synthesis,properties and optical response

A seeded surfactant‐free methyl methacrylate emulsion polymerization is employed to prepare core–shell particles with predetermined size and narrow size distribution. The particle size is determined by the ratio between methyl methacrylate (MMA, shell) and polytetrafluoroethylene (PTFE, core). Monodisperse particles in the 100–350 nm range are obtained. These particles are used to grow colloidal photonic crystals (opals) of very high optical quality, thus indirectly demonstrating the excellent control of microbead size distribution achieved by this preparation technique. The optical properties of the opals are investigated by means of reflectance and polarized‐angle‐resolved transmittance spectroscopies. These data provide a rough determination of the effective refractive index of the system, which is favorably compared with values obtained by simple effective medium models. Copyright © 2012 Society of Chemical Industry     

Synthesis of well‐defined,functionalized polymer latex particles through semicontinuous emulsion polymerization processes

The design of a semicontinuous emulsion polymerization process, primarily based on theoretical calculations, has been carried out with the objective of achieving overall independent control over the latex particle size, the monodispersity in the particle size distribution, the homogeneous copolymer composition, the concentration of functional groups (e.g., carboxyl groups), and the glass‐transition temperature with n‐butyl methacrylate/n‐butyl acrylate/methacrylic acid as a model system. The surfactant coverage on the latex particles is very important for maintaining a constant particle number throughout the feed process, and this results in the formation of monodisperse latex particles. A model has been set up to calculate the surfactant coverage from the monomer feed rate, surfactant feed rate, desired solid content, and particle size. This model also leads to an equation correlating the polymerization rate to the instantaneous conversion of the monomer or comonomer mixture. This equation can be used to determine the maximum polymerization rate, only below or at which monomer‐starved conditions can be achieved. The maximum polymerization rate provides guidance for selecting the monomer feed rate in the semicontinuous emulsion polymerization process. The glass‐transition temperature of the resulting carboxylated poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) copolymer can be adjusted through variations in the compositions of the copolymers with the linear Pochan equation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 30–41, 2003     

Microwave dielectric properties of polytetrafluoroethylene‐polyacrylate composite films made via aerosol deposition

Few studies have examined the deposition of polytetrafluoroethylene (PTFE) using additive manufacturing and their subsequent properties in microwave devices. The present study examines polytetrafluoroethylene‐polyacrylate (PTFE‐PA) composite films made via aerosol deposition to assess the potential use of PTFE in additive manufacturing processes. The composites are composed of PTFE‐PA core ? shell nanoparticles, synthesized using a seeded emulsion polymerization, containing various PTFE weight fractions up to 50%. The synthesized nanoparticles were sprayed onto a heated glass substrate and subsequently annealed at a temperature above the glass transition temperature of PA and below that of PTFE, rendering a solid film approximately 40 µm thick. A cavity perturbation resonance technique was employed to determine the complex permittivity of the films. As the volume fraction of PTFE increased, the real part of the permittivity ?′ decreased while the imaginary part of the permittivity ?″ showed little variation. The results demonstrate a promising approach for incorporating PTFE into additive manufacturing processes, particularly for microwave devices. © 2016 Society of Chemical Industry     

Synthesis and properties of fluorine–silicon modified polyacrylate hybrid latex particles with core–shell structure obtained via emulsifier‐free emulsion polymerization

A core–shell fluorine–silicon modified polyacrylate hybrid latex was successfully prepared via emulsifier‐free emulsion polymerization. The chemical composition and core–shell morphology of the resultant hybrid particles were investigated using ¹H NMR and Fourier transform infrared spectroscopies and transmission electron microscopy (TEM), respectively. TEM analysis indicated that the core–shell hybrid particles were uniform with narrow size distributions. The particle size and zeta potential decreased with an increase of alkylvinylsulfonate surfactant from 2.5 to 6.0 wt%. X‐ray photoelectron spectroscopy revealed that fluorine concentrated preferentially at the film surface during a film‐formation process. The film formed from the fluorine–silicon modified polyacrylate showed much higher thermal stability than a film formed from polyacrylate and fluorine‐modified polyacrylate. Contact angle results showed that a finished fabric had remarkable water repellency. © 2015 Society of Chemical Industry     

Preparation and surface properties of core‐shell polyacrylate latex containing fluorine and silicon in the shell

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     

甲基含氢硅油对喷雾干燥磷铵灭火粉性能的影响

采用喷雾干燥法制备了球形空心超细NH4H2PO4灭火粉,并添加甲基含氢硅油乳液、氟碳表面活性剂FK-510对粉体进行原位改性,研究了表面活性剂甲基含氢硅油对NH4H2PO4灭火粉的疏水性、表面元素、表面形貌、分散性及粒度分布的影响. 结果表明,干燥过程中甲基含氢硅油及FK-510迁移聚集于颗粒表面,且FK-510位于最外层而甲基含氢硅油位于次外层,明显提高灭火粉疏水性;添加甲基含氢硅油明显改善了粉体分散性,当硅油添加量为NH4H2PO4质量的3%时,所得产品疏水性、分散性和球形度良好,活化指数提高到93.7%.     

Melt processability of polytetrafluoroethylene: Effect of melt treatment on tensile deformation mechanism

It is widely accepted that the melt processibility of polytetrafluoroethylene (PTFE) is poor. In this article, a high‐molecular‐weight PTFE was extruded smoothly with a modified die; and critical shear rate could be raised to 4 s^?1, using a die with L/D (length to diameter) ratio of 200. Meanwhile, we compared the current PTFE fiber spinning method with melt spinning to investigate the effects of high‐temperature treatment on the drawability of PTFE and found that the processing sequence could play a key role. The deformation imposed before or after the high‐temperature treatment could determine whether the fibrillation can be achieved continuously and effectively. Based on the experiment phenomenon, together with the results of differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy characterization, we proposed a model to describe the submicron structural change of PTFE during extension. From this model, the fundamental mechanism for the poor melt processibility of PTFE was elucidated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Low‐molecular‐weight polytetrafluoroethylene bearing thermally stable perfluoroalkyl end‐groups prepared in supercritical carbon dioxide

Low‐molecular‐weight (M_n) polytetrafluoroethylene (PTFE) homopolymers were successfully prepared using a perfluorodiacyl initiator, bis(perfluoro‐2‐n‐propoxypropionyl) peroxide, in supercritical carbon dioxide. Solid‐state ¹⁹F NMR and Fourier transform infrared spectral analyses show that perfluoroalkyl end‐groups are present in the resultant PTFEs. Thermogravimetric analysis suggests all polymers with various M_n have outstanding thermal stability. Differential scanning calorimetry measurements indicate that both melting and crystallization transitions of PTFE shift to lower temperatures when M_n decreases, because shorter polymer chains can move more easily at lower temperatures. Investigation of polymerization kinetics suggests that the rate law for the polymerization has kinetic orders of 0.5 and 1.0 with respect to initiator and monomer concentrations, indicating that termination occurs through coupling of propagating chains. Melt fusion crystallinity of as‐polymerized PTFE can be as high as 86%, and the polymerization rate does not seem to be obviously affected by the total interphase area of the polymer phase, implying polymerization mainly occurs in the carbon dioxide‐rich fluid phase; meanwhile, the low viscosity and high diffusivity of supercritical carbon dioxide mean that propagating chains have more opportunities to meet, thus yielding low‐M_n PTFEs. Copyright © 2012 Society of Chemical Industry     

Effect of acrylic acid and hydroxyethyl methacrylate modified nano-SiO2 particles on poly(methyl methacrylate-hydroxyethyl methacrylate) soap-free emulsion polymerization

Nano-SiO₂ powder was modified with acrylic acid (AA) and hydroxyethyl methacrylate (HEMA), respectively. The kinetics of the soap-free emulsion polymerization of methyl methacrylate (MMA) and HEMA in the presence of unmodified or modified nano-SiO₂ particles was investigated. The structure of the nano-SiO₂ particles and the Poly(MMA-HEMA) composite emulsion was characterized by Fourier transform infrared spectroscope (FT-IR). The particle size and size distribution of the emulsion, the morphology of emulsion particle, the surface tension, and ionic conductivity of these systems before and after polymerization were determined. The IR spectra showed that the organic modifiers were incorporated onto the surface of the nano-particles. In addition, the solid content and monomer conversion of the Poly(MMA-HEMA) composite emulsion with modified nano-SiO₂ are higher than that with original inorganic particles. The particle size became smaller and the particle distribution narrowed after applying the modified nano-SiO₂ particles. The SEM observation demonstrated that the shapes of these emulsion particles were uniform sphere. The surface tension and ionic conductivity increased significantly after polymerization.     

Coating of polytetrafluoroethylene/polyacrylate: Core-shelled structure and tribological behaviors

In order to improve the tribological properties of polytetrafluoroethylene (PTFE), the core-shelled PTFE/polyacrylate nanoparticles were prepared by seed emulsion polymerization and its tribological behaviors were investigated. The core–shell structure was determined by a Fourier transform infrared spectrometer and transmission electron microscopy. The results of thermoanalysis showed that polyacrylate had lost more weight than PTFE/polyacrylate composite above 300 °C, which indicated an improvement in the thermal stability. Moreover, the friction and wear results indicated that friction coefficient of PTFE/polyacrylate coating keeps at a relatively lower level, which is between that of PTFE and polyacrylate, and the wear volume is the smallest, so that an excellent performance of low friction and wear resistance was demonstrated. Besides, the tribological properties of the core-shelled coating are maintained to be stable under high load or high speed. Therefore, the core-shelled nanoparticles would be potential to polymer coating as high-performance solid lubricants. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47774.     

The Impact of In‐situ Fabric Surface Energy on Dehydration of Fabrics

Reducing liquid surface tension is widely used to increase the efficiency of the centrifugal dehydration in textile wet processing. However, increasing the dehydration efficiency by decreasing fabric surface energy is seldom studied. In this work, the impact of in situ fabric surface energy on residual moisture content (RMC) of fabrics in the dehydration processes was investigated. Different types of fluorocarbon surfactants including cationic, anionic, nonionic and amphoteric were adopted as additives in this study. The liquid surface tension and RMC were efficiently decreased when fluorocarbon surfactants were used. Notably, a cationic fluorocarbon surfactant displays similar surface tension but distinct dehydration efficiency. The in situ fabric surface energy was evaluated by measuring the n‐octane contact angle on the cotton fabric surface under the surfactant solution using the captive bubble method. It was found that the cationic fluorocarbon surfactant system gave the lowest fabric surface energy, which was probably because cationic fluorocarbon surfactants are easier to adsorb onto the surface of cotton fabric to form a fluorocarbon layer. The chemical composition (¹⁹F, ¹²C and ¹⁶O) analysis of the cotton fabric surface by X‐ray photoelectron spectroscopy confirms the hypothesis.     

Soap‐free emulsion copolymerization of perfluoroalkyl acrylates in the presence of a reactive surfactant

Soap‐free emulsion copolymerization of perfluoroalkyl acrylate (FA)/methyl methacrylate (MMA)/n‐butyl acrylate (n‐BA) was carried out in the presence of sodium 2‐acrylamide‐2‐methyl propanesulfonate (AMPSNa) as a reactive surfactant and potassium persulfate (KPS) as an initiator. An analysis of the effects of concentration of AMPSNa, KPS, FA as well as polymerization temperature on the kinetic features (rate of polymerization) and colloidal characteristics (mean particle diameter, particle disperse index, particle numbers, and surface charge density) was followed. NMR, FTIR, AFM, and fluorine‐selective electrode analysis were used to characterize the composition and morphology of the FA copolymers. Both AFM analysis and contact angle measurements strongly implied that the fluorinated segments migrated to the outmost surface and created films with lower surface energy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2438–2444, 2007     

Morphology,dynamic rheology,and cohesive properties of epoxy‐modified polyurethane–acrylate microemulsions prepared by in situ surfactant‐free polymerization

A series of organic, solvent‐free, epoxy‐modified polyurethane–acryalte (EPUA) adhesives were prepared through in situ surfactant‐free polymerization. Stable EPUA microemulsions with average particle diameters of less than 100 nm and a unimodal distribution were obtained through control of the epoxy content. Transitions from irregular shapes with a heterogeneous size distribution to a regular spherical particle morphology with an apparent core–shell morphology were obtained for EPUA with an increasing epoxy content to 8 wt %. With epoxy addition, EPUA displayed pseudoplastic behavior instead of Newtonian behavior, and increases in the viscosity and pseudoplastic behavior were detected. In addition, the EPUA emulsion transferred from a viscous liquid to a solidlike liquid. The addition of epoxy was beneficial for phase mixing, interaction, and entanglements between polyurethane and polyacrylate, and the interactions between the EPUA colloidal particles were also enhanced. The thermal stability, mechanical properties, and water and solvent resistance were thereby improved, as was the cohesive properties. However, the corresponding properties were weakened with excessive epoxy, and this was ascribed to the greatly increased particle size, viscosity, and phase separation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39886.     

Preparation of grafted polytetrafluoroethylene fibers and adsorption of bilirubin

BACKGROUND: A successful hemoperfusion technique requires that the adsorbent for bilirubin should have a high specificity, adsorption capacity and adsorption rate, blood compatibility and no toxicity. Compared with polymer microbeads, polytetrafluoroethylene (PTFE) fibers have many advantages. The aim of the work reported here was to prepare a new polytetrafluoroethylene‐graft‐poly(glycidyl methacrylate)‐block‐polyethyleneimine (PTFE‐g‐PGMA‐b‐PEI) adsorbent for bilirubin based on PTFE fibers by the ⁶⁰Co radiation‐induced graft polymerization of GMA followed by the chemical modification of the epoxy groups on the PTFE‐g‐PGMA fibers with PEI. In addition, the adsorption properties of this novel adsorbent for bilirubin were examined. RESULTS: The highest content of amino groups obtained on the PTFE‐g‐PGMA‐b‐PEI fibers was 1.87 mmol g^?1. The maximum adsorption capacity of the grafted fibers was 9.6 mg g^?1 at pH = 6.5. Bilirubin adsorption on these fibers obeyed the Langmuir model. Also, these fibers possessed the ability to selectively adsorb bilirubin in the presence of bovine serum albumin. CONCLUSION: The PTFE‐g‐PGMA‐b‐PEI fibers have a high adsorption capacity for bilirubin and excellent adsorption properties. In addition, this new adsorbent is inexpensive, easy to prepare and has no toxicity. So the PTFE‐g‐PGMA‐b‐PEI fibers as a biomedical adsorbent are promising for the removal of bilirubin through the hemoperfusion technique. Copyright © 2009 Society of Chemical Industry     

Preparation and characterization of a proton‐exchange membrane by the radiation grafting of styrene onto polytetrafluoroethylene films

Radiation‐induced simultaneous grafting of styrene onto polytetrafluoroethylene (PTFE) films and the subsequent sulfonation in the chlorosulfonic acid/dichloroethane were investigated. The effects of the main radiation grafting conditions, such as the type of solvents, irradiation dose, dose rate, the styrene concentrations, etc., on the degree of grafting (DOG) were studied. To elucidate the influence of both the grafting and sulfonation conditions on the properties of the PTFE‐g‐polystyrene‐sulfonic acid (PSSA) membranes, the sulfonation conditions, including the sulfonation temperature and the concentration of the ClSO₃H with respect to the DOG, were systematically evaluated. The grafted and sulfonated membranes were characterized by FTIR–ATR spectra, ion‐exchange capacity (IEC), water uptake, thickness measurement, etc. The as‐prepared PTFE‐g‐PSSA membranes in this work showed a good combination of a high IEC (0.85–2.75 meq g^?1), acceptable water uptake (8.86–56.9 wt %), low thickness, and volume expansion and/or contraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1415–1428, 2006     

Synthesis and characterization of fluoropolymer modified polyacrylate in emulsion polymerization

A novel method to produce fluorine‐containing polyacrylate emulsion is presented. It is prepared by the copolymerization of n‐methyl methacrylate, n‐styrene, n‐butyl acrylate, and α‐methacrylic acid in the presence of swollen particles of PTFE. The structure and properties of the polymers are characterized by GPC, PSD, SEM, and XPS. The number‐average molar mass (Mn) 51,332, and the polydispersity 5.8688 are obtained. The mean diameter of latex particles is 300nm. Scanning electron microscopy reveals that particles of the emulsion are well dispersed. Meanwhile, the F_1S content of the surface on the latex membrane is 8.99%. It is shown that the method of mixing micron and nanometer‐sized particles should be made the next step of research. It is also proved that inertia polymers can be used in emulsion property modification. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 558–562, 2006     

Preparation and properties of nano‐montmorillonite paper–plastic laminating adhesive

Emulsion paper–plastic nanometer laminating adhesive of 1.5% organic montmorillonite (OMMT) was prepared by OMMT intercalating polyacrylate‐system materials. In this article, it was discovered that nanometer‐laminating adhesive has better adhesion, smaller latex particles size, lower surface tension, and higher drying speed than general laminating adhesive. The rheologic behavior of the emulsion was discussed and it was shown that the value of n (the flow index of emulsion) was reduced and viscous flow activation energy (E_a) was increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 872–877, 2005     

PTFE改性玻纤增强MPPO材料力学性能及耐摩擦磨损性能的研究

采用直径为3.0μm的短玻纤(GF)(GF质量分数为20％)增强改性聚苯醚(MPPO),将其与粒径为5～7 μm的聚四氟乙烯(PTFE)微粉和甲基苯基硅油构成摩擦因数较低的耐磨体系.通过熔融共混法制备PTFE改性GF增强MPPO材料(简称MPPO/20％GF复合材料).对MPPO/20％GF复合材料的力学性能、热变形温...     

Narrow size‐distribution poly(methyl methacrylate) nanoparticles made by semicontinuous heterophase polymerization

The effect of surfactant (sodium dodecyl sulfate) concentration on particle size, molar masses, glass transition, and tacticity of poly(methyl methacrylate) (PMMA) nanoparticles synthesized by semicontinuous heterophase polymerization under monomer‐starved condition at constant monomer feeding rate is reported. Starved conditions are confirmed by the low amount of residual monomer throughout the reaction and by the fact that the instantaneous polymerization rate is similar to the feeding rate of monomer. Under these conditions, polymer particles in the nanometer range (20–30 nm) were obtained with narrow size distribution (1.07 < D_w/D_n < 1.18), depending of surfactant concentration. Final particle size diminishes as the surfactant concentration is increased. Glass transition temperatures and syndiotactic content (54%–59%) of the produced polymers are substantially higher than those reported for commercial and bulk‐made PMMA. Molar masses are much lower than those expected from termination by chain transfer to monomer, which is the typical termination mechanism in 0–1 emulsion and microemulsion polymerization of this monomer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011