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1.
    
One type of negatively charged alkoxysilane, that is, sulfonated 3‐(mercaptopropyl)trimethoxysilane (SMPTS), has been developed from 3‐(mercaptopropyl)trimethoxysilane (MPTS) and hydrogen peroxide. SMPTS is used to modify sulfonated poly(ether sulfone) (SPES) through in situ sol–gel process. The membranes with proper SMPTS dosage show enhanced ion exchange capacity (IEC), hydrophilicity, mechanical strength, chemical stability, and proton conductivity, which prove that SMPTS is an effective modifier for preparing proton‐exchange hybrid membranes. With MPTS of 5–20%, the hybrid membranes exhibit IEC 1.34–1.50 mmol g?1, thermal stability 264–316°C, and proton conductivity 0.0015–0.0102 S cm?1 and thus recommended for potential application in fuel cells. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

2.
    
Sulfonated poly(ether ether ketone) (SPEEK) is currently considered to be one of the most potential candidates of commercial perfluorinated sulfonic acid proton exchange membranes. To balance the proton conductivity and mechanical properties of SPEEK, nano TiO2 coated carbon nanotubes (TiO2@CNTs) were prepared using a benzyl alcohol-assisted sol-gel method and then used as a new nanofiller to modify SPEEK to prepare SPEEK/TiO2@CNTs composite membranes. The thick insulated TiO2 coating layer can effectively avoid the risk of electronic short-circuiting formed by CNTs, while the hydrophilicity of TiO2 can also reduce the polar difference between CNTs and SPEEK matrix, thus promoting the homogeneous dispersion of CNTs in the composites. As a result, the composite membranes demonstrated simultaneously improved strength and proton conductivity. Incorporating 5 wt% of TiO2@CNTs exhibited 31% growth in mechanical strength when compared with pure SPEEK. Moreover, the maximum conductivity was 0.104 S cm−1 (80°C) for the composite membrane with 5 wt% of TiO2@CNTs, which was nearly twice as high as that of SPEEK membrane (0.052 S cm−1).  相似文献   

3.
    
To regulate the polymer–diluent interaction and control the viscosity of the casting solution, diphenyl ketone (DPK) and a N,N‐dimethylacetamide/N,N‐dimethylformamide mixture were selected as a combined diluent. Poly(vinyl chloride) (PVC) utlrafiltration membranes, which had sufficient mechanical properties for their practical applications because of their bicontinuous spongy structure, were prepared by a combined process of thermally induced phase separation and non‐solvent‐induced phase separation. The phase‐separation mechanism was analyzed. In an air bath, the cast nascent solution immediately transformed into a transparent gel, and liquid–liquid phase separation was induced by a sudden drop in the temperature before crystallization. An ice–water bath was used to coagulate the membrane. The effects of the DPK and PVC concentrations on the membrane structures and performances were mainly investigated. The results show that an increase in the DPK content made the membrane pores change from fingerlike to spongy. Fully spongy pores formed, and the pores size decreased with increasing PVC concentration. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42953.  相似文献   

4.
    
The behavior of sulfonated poly(ether ether ketone) (sPEEK) membranes in ethanol–water systems was studied for possible application in direct ethanol fuel cells (DEFCs). Polymer membranes with different degrees of sulfonation were tested by means of uptake, swelling, and ethanol transport with dynamic measurements (liquid–liquid and liquid–gas systems). Ethanol permeability was determined in an liquid–liquid diffusion cell. For membranes with an ion‐exchange capacity (IEC) between 1.15 and 1.75 mmol/g, the ethanol permeability varied between 5 × 10?8 and 1 × 10?6 cm2/s, being dependent on the measuring temperature. Ethanol and water transport in liquid–gas systems was tested with pervaporation as a function of IEC and temperature. Higher IEC accounted for higher fluxes and lower water/ethanol selectivity. The temperature had a large effect on the fluxes, but the selectivity remained constant. Furthermore, the membranes were characterized with proton conductivity measurements. The proton diffusion coefficient was calculated, and a transition in the proton transfer mechanism was found at a water number of 12. Membranes with high IEC (>1.6 mmol/g) exhibited larger proton diffusion coefficients in ethanol–water systems than in water systems. The membrane with the lowest IEC exhibited the best proton transport to ethanol permeability selectivity. The use of sPEEK membranes in DEFC systems depends on possible modifications to stabilize the membranes in the higher conductive region rather than on modifications to increase the proton conductivity in the stable region. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

5.
    
Blends based on poly(ether sulfone) (PES) and a semiaromatic liquid crystalline copolyester (R5) were obtained by injection molding across the entire composition range. The blends showed two pure amorphous phases. The fibrillar structure of the skin led to enhancements in the stiffness. The break properties, however, decreased at low LCP contents, due to the expected lack of adhesion between the phases. The increase in the modulus at increasing LCP content led to improvements in tensile strength. The notch sensitivity of PES decreased after the addition of low LCP levels, giving rise to enhancements of almost 600% in the notched impact strength. The unusually enhanced performance of the 20/80 blend, which has been seen previously in another thermoplastic/LCP blend, suggests that the dispersed PES phase in this blend may act as rubber particles do in rubber toughened thermoplastics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 52–59, 2004  相似文献   

6.
    
The synthetic procedure and the characterization of the new amino derivatives of poly(oxa‐p‐phenylene‐3,3‐phtalido‐p‐phenylene‐oxa‐p‐phenilene‐oxy‐phenylene) (PEEK‐WC) with various average degrees of substitution, is reported. The amino PEEK‐WC was extensively characterised by using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, differential scanning calorimeter, scanning electron microscopy, Elemental analyses, NMR, and viscosity measurements. The amino PEEK‐WC shows different solubility in some solvents in comparison with the parent polymer, good thermal stability and is able to form membrane by means of the phase inversion technique. Amino PEEK‐WC results to be quite reactive and can lead to further modification. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

7.
    
Stoichiometry and cure temperature were evaluated for epoxy systems based on the diglycidyl ethers of bisphenol‐A and bisphenol‐F and cured with 3,3′‐ or 4,4′‐diaminodiphenylsulfone. The materials were formulated as stoichiometric benchmarks and with an excess of epoxide and cured in two steps (125°C/200°C) or one step (180°C). Dynamic mechanical analysis and free volume testing indicated decreased crosslink density and increased chain packing in the excess‐epoxy materials, as well as a narrowing gap in properties between 33‐ and 44‐cured networks with excess epoxy. The narrowing gap was less pronounced in materials cured at 180°C. The excess‐epoxy materials were more resistant to water ingress, exhibiting reduced equilibrium water uptake. The excess‐epoxy materials were also more resistant to methyl ethyl ketone ingress, which occurred at a slower rate in most excess‐epoxy materials. The improvement in fluid resistance was attributed to enhanced chain packing in the materials with lower crosslink densities. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

8.
    
A series of uniaxial tensile loading–unloading tests is performed on isotactic polypropylene at room temperature. Prior to mechanical testing, injection‐molded specimens are annealed for 24 h at temperatures T = 145, 150, 155, 158, 160, 163, and 165°C, which cover the entire region of high‐temperature annealing temperatures. A constitutive model is developed for the elastoplastic behavior of a semicrystalline polymer at small strains. The stress–strain relations are determined by six adjustable parameters that are found by matching observations in cyclic tests. Fair agreement is demonstrated between the experimental data and the results of numerical simulation. It is shown that all material constants are affected by the annealing temperature, which is explained by changes in the crystalline morphology driven by thermal treatment. Some of the adjustable parameters experience finite jumps in the vicinity of the critical temperature Tc = 159°C. These jumps are attributed to the α2 → α2′ phase transformation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 186–196, 2003  相似文献   

9.
    
A series of bromomethylated poly(arylene ether ketone)s (PAEKs) with different contents of bromine tethered to the benzyl groups were successfully synthesized and characterized in this work. For this purpose, poly(arylene ether ketone) with 3,3′,5,5′‐tetramethyl‐4,4′‐dihydroxybipheny moiety (PAEK‐TM) was prepared by the aromatic nucleophilic polycondensation, and then the PAEK‐TM has benzylic methyl groups that were converted to bromomethyl groups by a radical reaction using N‐bromosuccinimide. Then, the bromomethylbenzyl groups in the membrane was converted to quaternary ammonium moieties in TMPAEK‐NOH. 1H‐NMR measurements were used to characterize and confirm the structures of the resulting PAEK‐x‐BrTM and TMPAEK‐NBr derivatives (x refers to the molar percentage of bromine introduced per repeating units). TGA analysis showed that PAEK‐x‐BrTM exhibited a very low‐decomposition temperature at about 200°C corresponding to the C Br bond cleavage. The hydroxide conductivity of TMPAEK‐NOH membrane was 8 mS cm−1 at room temperature, while the water uptake of TMPAEK‐NOH membrane was 22.3% at 20°C and 32.6% at 60°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

10.
    
Hybrid composites, based on poly(ether sulfone) (PES) and glass fiber–reinforced copolyester liquid crystalline polymer (gLCP) up to 40% gLCP, were obtained by injection molding: these polymers were immiscible. Despite its higher viscosity, the gLCP acted as a processing aid for PES. The Young's modulus of the composites increased linearly with gLCP content, attributed to the opposing effects of increasing skin thickness and decreasing orientation of the fibrillated LCP in the skin. The break properties decreased with increasing gLCP content, mainly because of the lack of adhesion between the phases. The notched impact strength increased substantially on addition of 10% gLCP, suggesting that the dispersed rigid particles changed the fracture behavior of PES. The composite with 10% gLCP appeared to be the most attractive because it showed an increase in stiffness of 18%, 6.5‐fold impact strength, and a tensile strength similar to that of PES. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 854–860, 2004  相似文献   

11.
    
Polypropylene containing terminal unsaturation was modified with a hydride‐terminated polydimethylsiloxane (PDMS) at three different temperatures through a catalytic hydrosilylation reaction in the melt phase. A comprehensive study on the surface characteristics of hydrosilylated polypropylene (SiPP) was conducted by combining macroscopic thermodynamics, microstructure, and chemical composition measurements. Axisymmetric drop shape analysis–profile (ADSA‐P) was used to characterize the surface wettability. The morphology, roughness, and heterogeneity of the surfaces were investigated by the lateral‐force mode of atomic force microscopy (LFM). X‐ray photoelectron spectroscopy (XPS) was used to quantify the surface chemical composition. LFM images showed that all sample surfaces were rough and heterogeneous on a micrometer scale. XPS analysis showed that the surfaces investigated were complicated in composition and that various oxides existed on the surfaces. The surface wettability was well correlated to the surface microstructure and composition. The surfaces investigated were modeled based on the microstructure observed, and a new scheme was developed to calculate surface free energy and adhesion work. For SiPPs, the lower the reaction temperature, the more PDMS incorporation was observed, the smaller the surface free energy and the work of adhesion, the more hydrophobic the surface, and the lower the permeability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3117–3131, 2003  相似文献   

12.
    
The effect of nanoclay additive on the structure, morphology, and mechanical properties of polypropylene meltblown webs is reported here for the first time. Effect of nanoclay on the meltblown processing, resultant fiber web structure, and properties are discussed. Combination of wide‐angle x‐ray diffraction, differential scanning calorimetry, and transmission electron microscopy were used to determine the nature of clay dispersion in the polypropylene fiber matrix and resultant morphology. Transmission electron microscopy micrographs revealed nanolevel dispersion of the additive in the fiber web. Clay additive did not offer any benefit as far as the mechanical properties of the meltblown web are concerned. Meltblown web samples with nanoclay had higher variability in web structure, high air permeability, high stiffness, and lower mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

13.
    
In recent years, water swellable rubber composites have been the subject of many scientific and research investigations as well as many industrial programs. Here, we present an updated overview of the developments in the area of water swellable rubber composites with different kinds of fillers, compatibilizers, and cross‐linked agents, in terms of their manufacturing methods, synthesis, chemical, physical, and mechanical properties. Several critical issues and suggestions for future work are detailed, underscoring the roles of material scientists and manufacturing engineers in the bright future of this new material through value addition to enhance its usage and fields of application. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42786.  相似文献   

14.
    
The effects of heat treatment on the properties of membranes prepared from blends of poly(ether sulfone)/sulfonated poly(phenylene sulfide) (SPPS) and phenolphthalein poly(ether ether ketone)/SPPS were studied in detail. The membranes' fundamental properties, including water content, transport number, diffusion coefficient of electrolytes, flux, and so on, changed with both treated temperature and time, whereas the ion‐exchange capacity and electrical resistance remained approximately unchanged. The trends may have been due to the possible structural change resulted from the shrinking of the polymers forming the membranes. Furthermore, the membranes also retained a good physical appearance at temperatures below 220°C. Therefore, a series of heterogeneous membranes with desired conductivities and selectivities as well as proper water contents, which could satisfy different industrial purposes, such as electrodialysis, diffusional dialysis, and proton exchange, were achieved by simple heat treatment for a proper time and at a proper temperature. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 494–499, 2005  相似文献   

15.
    
Poly(arylene ether benzonitrile) (PAEBN) was synthesized with 2,6‐dichlorobenzonitrile and biphenol. PAEBNs with various molecular weights (MWs), 1,640,000 and 185,000 g/mol, were synthesized by control of the stoichiometry of the monomers and were blended with sulfonated poly(ether ether ketone) (SPEEK). The effects of MW on the water uptake, swelling, methanol permeability, and proton conductivity of the SPEEK/PAEBN blend membranes were investigated. The molecular mobility of the SPEEK/PAEBN blends was also examined in this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

16.
    
The effects of ethylene oxide (EO), vaporized hydrogen peroxide (VHP), gamma (γ) radiation, and electron‐beam (E‐beam) on the physiochemical and morphological properties of medical device polymers are investigated. Polymers with ether, carbonate, carboxylic acid, amide and ester functionalities are selected from a family of poly(ethylene glycol) (PEG) containing tyrosine‐derived polycarbonates (TyrPCs) to include slow, medium, fast, and ultra‐fast degrading polymers. Poly(lactic acid) (PLA) is used for comparison. Molecular weight (Mw) of all tested polymers decreases upon gamma and E‐beam, and this effect becomes more pronounced at higher PEG content. Gamma sterilization increases the glass transition temperature of polymers with high PEG content. EO esterifies the carboxylic acid groups in desaminotyrosol‐tyrosine (DT) and causes significant degradation. VHP causes hydroxylation of the phenyl ring, and hydrolytic degradation. This study signifies the importance of the chemical composition when selecting a sterilization method, and provides suggested conditions for each of the sterilization methods.

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17.
    
To improve the pervaporation performance of PDMS membrane, alkyl groups with different chain length were grafted into PDMS matrix. The prepared membranes were characterized by ATR‐IR, DSC, TGA, PALS, and tensile testing. The effects of alkyl grafting on pervaporation performance of PDMS membrane were investigated in separation of ethyl acetate/water mixture. Experimental results show that the separation factor of PDMS membrane is largely improved by alkyl grafting because of the enhanced preferential sorption of ethyl acetate, and this improvement depends on alkyl grafting ratio and alkyl chain length. The total flux of PDMS membrane reduces after alkyl grafting owing to the decreased free volume. When grafting ratio is above 6.9%, membrane grafted with shorter alkyl groups is preferred for pervaporation. The best pervaporation performance is achieved by 9% octyl grafted PDMS membranes with a separation factor of 592 and a total flux of 188 gm?2 h?1 in separation of 1% ethyl acetate/water mixture at 40 °C. Moreover, this octyl grafted PDMS membrane also exhibits excellent separation performance in removal of butyl acetate, methyl‐tert‐butyl ether, and n‐butanol from water. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43700.  相似文献   

18.
    
The effect of the casting solvent on the structure of poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) membranes was investigated experimentally. The PTMSP membranes were cast from solutions of cyclohexane, toluene, and tetrahydrofuran; the membranes were characterized by the positron annihilation lifetime spectroscopy (PALS) technique and by gas‐permeation measurements of O2, N2, and CO2. The decay curves from the positron annihilation lifetime spectroscopy gave the best fit when two long‐life components (τ3 and τ4, τ3 < τ4) were employed. This suggests that two types of free volume existed in the PTMSP membranes. The size and number density of τ4, which was characteristic for PTMSP, decreased in the following order of the casting solvents: cyclohexane > toluene > tetrahydrofuran. The order was consistent with the order of gas permeability. A good correlation was observed between the permeability and the structural parameter that denoted the free‐volume size and the number density of τ4. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 497–501, 2003  相似文献   

19.
    
In this work, some films of poly(ε‐caprolactone) (PCL) containing lysozyme at 5% by weight are obtained. Lysozyme is a natural antimicrobial molecule. The films are submitted to cold drawing process at three different draw ratios, λ = 3, 4, and 5, where λ is the ratio between final and initial length. Morphology, physical and barrier properties of the drawn samples are studied and correlated to the release of lysozyme. Tests against Bacillus sp are performed and correlated to the material texture. The molecular orientation of uniaxially drawn lysozyme doped PCL films is demonstrated to be a significant parameter for controlled release monitoring of the active molecule and the antimicrobial activity.  相似文献   

20.
    
Gelatin‐based hydrogels were synthesized and characterized for use as Cu2+‐ion sorbents. Gelatin was crosslinked in the presence of two different monomers, that is, acrylamide (AAm) and/or 2‐hydroxypropyl methacrylate, with N,N‐methylenebisacrylamide, ammonium persulfate, and sodium bicarbonate. The as‐prepared hydrogels were further characterized by scanning electron microscopy, Fourier transform spectroscopy, and the study of their swelling behavior as a function of temperature, time, and pH to evaluate their structure–property relationships. The hydrogels were observed to be good sorbents of Cu2+, and a maximum uptake of 84.8% was observed within 2 h at 37°C and with 10 ppm of the Cu2+‐ion solution for the gelatin and polyacrylamide hydrogel, which also exhibited the maximum retention capacity at 14.9 mg/g after four feeds. All of the experimental data exhibited good matches with the Langmuir isotherm and followed pseudo‐second‐order kinetics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

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