Structured polymer electrolyte blends based on sulfonated polyetherketoneketone (SPEKK) and a poly(ether imide) (PEI)

The performance and economics of proton-exchange membrane (PEM) fuel cells are highly dependent on the membranes used to separate the fuel and oxidant. While maintaining reasonable cost, the membrane must feature a number of desirable properties including high proton conductivity. Blends of polymers are one approach to tailoring PEM properties; however, blending to achieve mechanically and chemically robust membranes has generally resulted in reduced conductivity. The objective of this work was to demonstrate the use of field alignment of the proton-conducting domains to increase the conductivity in a polymer blend PEM. A blend of sulfonated poly(etherketoneketone) (SPEKK) and a polyether imide (PEI) was used to illustrate this method. Blends of SPEKK/PEI with a 3:7 mass ratio were aligned using electric field strengths varying from 0 to 30 V/mm and frequencies varying from 0 to 10 kHz. In general, the degree of alignment agreed with theoretical predictions for the alignment of drops or particles suspended in a fluid with a different dielectric constant, e.g., when the frequency of the applied ac field was increased, the threshold field for phase alignment increased and the diameter of the oriented columnar structures decreased. Alignment resulted in up to three orders of magnitude increase in conductivity at low humidity. By careful selection of temperature and residual solvent content, alignment was shown to be possible in the melt state, which is essential for an economic process for producing alignment-enhanced membranes.     

Pervaporation of alcohol-toluene mixtures through polymer blend membranes of poly(acrylic acid) and poly(vinyl alcohol)

Homogeneous membranes were prepared by blending poly(acrylic acid) with poly(vinyl alcohol). These blend membranes were evaluated for the selective separation of alcohols from toluene by pervaporation. The flux and selectivity of the membranes were determined both as a function of the blend composition and of the feed mixture composition. The results showed that a polymer blending method could be very useful to develop new membranes with improved permselectivity. The pervaporation properties could be optimized by adjusting the blend composition. All the blend membranes tested showed a decrease in flux with increasing poly(vinyl alcohol) content for both methanol—toluene and ethanol—toluene liquid mixtures. The alcohols permeated preferentially through all tested blend membranes, and the selectivity values increased with increasing poly(vinyl alcohol) content. The pervaporation characteristics of the blend membranes were also strongly influenced by the feed mixture composition. The fluxes increased exponentially with increasing alcohol concentration in the feed mixtures, whereas the selectivities decreased for both liquid mixtures.     

Thermal and crystallization characteristics of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends were miscible in the amorphous state in all of the blend compositions studied, as evidenced by a single, composition-dependent glass transition temperature (T_g) observed for each blend composition. The variation in the T_g value with the blend composition was well predicted by the Gordon-Taylor equation, with the fitting parameter being 0.57. The cold-crystallization peak temperature decreased with increasing PTT content, while the melt-crystallization peak temperature decreased with increasing amount of the minor component. The subsequent melting behavior after both cold- and melt-crystallization exhibited melting point depression, in which the observed melting temperatures decreased with increasing amount of the minor component. During melt-crystallization, both components in the blends crystallized concurrently just to form their own crystals. The blend with 60% w/w of PTT exhibited the lowest total apparent degree of crystallinity.     

The miscibility of poly(vinyl alcohol)/poly(N-vinylpyrrolidone) blends investigated in dilute solutions and solids

Poly(vinyl alcohol) (PVA) (polymer A) and poly(N-vinylpyrrolidone) (PVP) (polymer B) are known to form a thermodynamically miscible pair. In the present study the conclusion on miscibility of PVA/PVP solid blends, confirmed qualitatively (DMTA, FTIR) and quantitatively (DSC, χ_AB = − 0.69 at 503 K) is compared with the miscibility investigations of PVA/PVP solution blends by the technique of dilute solution viscometry. The miscibility of the ternary (polymer A/ polymer B/ solvent) system is estimated on the basis of experimental and ideal values of the viscosity parameters k, b and [η]. It is found that the conclusions on miscibility or nonmiscibility drawn from viscosity measurements in dilute solution blends depend: (i) on the applied extrapolation method used for the determination of the viscosity interaction parameters, (ii) on the assumed definition of the ideal values and (iii) on the thermodynamic quality of the solvent, which in the case of PVA depends on its degree of hydrolysis. Hence, viscometric investigations of dilute PVA/PVP solution blends have revealed that viscometry, widely used in the literature for estimation of polymer-polymer miscibility can not be recommended as a sole method to presume the miscibility of a polymer pair.     

Compatibility and phase structure of binary blends of poly(lactic acid) and glycidyl methacrylate grafted poly(ethylene octane)

This work study is the compatibility, phase structure, and component interaction of poly(lactic acid) (PLA) and glycidyl methacrylate grafted poly(ethylene octane) (GMA-g-POE denoted as mPOE) blend by Fourier transform infrared (FTIR) spectra, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and wide-angle X-ray diffraction (WAXD), respectively. All the binary blend compositions exhibit two distinct glass transition temperatures corresponding to the mPOE-rich and PLA-rich phases, respectively. Moreover, these two peaks approach each other with increasing mPOE content, indicating partial compatibility between the PLA and mPOE. Chemical reactions between the end carboxyl groups of the PLA and epoxy groups of the mPOE are considered as the driving force of the enhanced compatibility. They lead to an increase in viscosity of the blends and a decrease in the structural symmetry of PLA. This result brings about a decrease in the spherulite growth rate and the degree of crystallinity. Glass transition temperature (T_g) depression of mPOE is attributed to the negative pressure imposed on the dispersed rubber phase, resulting from differential contraction due to the thermal shrinkage mismatch upon cooling from the melt state. The negative pressure in the dispersed particles, in turn, would cause a dilational effect for the matrix ligament between the particles, and therefore increases the ductility and toughness of PLA.     

Miscibility and hydrolytic degradation in alkaline solution of poly(l-lactide) and poly(p-vinyl phenol) blends

Poly(l-lactide) (PLLA) was melt-blended with poly(p-vinyl phenol) (PVPh) using a two-roll mill, and the miscibility between PLLA and PVPh and degradation of the blend films were investigated. It was found that PLLA/PVPh blend has miscibility in the amorphous state because only single T_g was observed in the DSC and DMA measurements. The T_g of the PLLA/PVPh blend could be controlled in the temperature range from 55 °C to 117 °C by changing the PVPh weight fraction. In alkaline solution, degradation rate of PLLA/PVPh blends was faster than that of neat PLLA because PVPh could dissolve in alkaline solution. The surface morphology of degraded PLLA and PLLA/PVPh blend were observed by SEM. The surface morphology of degraded PLLA/PVPh blend was finer than that of PLLA. Young's modulus of PLLA/PVPh blend increased with increasing PVPh content. Yield stress of PLLA/PVPh blends whose PVPh content was less than 30 wt% kept the level of about 55 MPa and that of PLLA/PVPh blend whose PVPh content was 40 wt% is much lower than that of neat PLLA.     

X-ray investigation of polypropylene and poly(ethylene-co-vinyl acetate) blends irradiated with fast electronsWAXS investigation of irradiated i-PP/EVA blends

Blends consisting of poly(propylene-ethylene) (PP) and poly(ethylene-co-vinyl acetate) (EVA) copolymers were investigated. Specimens were irradiated with fast electrons at different doses. Some of the samples show thermo-shrinkable properties. The interplanar spacing, paracrystalline factor, degree of crystallinity and crystallite sizes were determined by WAXS measurements. Results have been reported in respect to PP content and irradiation dose. A decrease of the crystallite’s imperfections with the rise of the irradiation dose was observed. An interface built up of partially interpenetrated amorphous molecular chains of incompatible polymers and separate PP and EVA small crystallites is suggested.     

Morphology control of sulfonated poly(ether ketone ketone) poly(ether imide) blends and their use in proton-exchange membranes

Polymer blends based on sulfonated poly(ether ketone ketone) (SPEKK) as the proton-conducting component and poly(ether imide) (PEI) as the second component were considered for proton-exchange membranes (PEMs). The PEI was added to improve the mechanical stability and lower the water swelling in the fuel cell environment. Membranes were cast from solution using N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc). The ternary, polymer/polymer/solvent, phase diagram was determined to provide guidance on how to control the morphology during solvent casting of blend membranes.

For blends of SPEKK (ion-exchange capacity = 2 mequiv/g) with PEI as the minority component, the morphology consisted of dispersed particles of 0.5–6 μm. Larger particles were achieved by increasing the PEI content and/or lowering the casting temperature. High-temperature annealing after solution casting did not affect the morphology of blend membranes, due to the low mobility and compatibility of the two polymers.

The possible use of SPEKK/PEI blends in PEMs is discussed in terms of existing theories of ion transport in polymers.     

Compatibilization of polypropylene/poly (ethylene oxide) blends and crystallization behavior of the blends

The compatibilization of incompatible polypropylene (PP)/poly(ethylene oxide) (PEO) blends was studied. The experimental results showed that the graft copolymer [(PP-MA)-g-PEO] of maleated PP(PP-MA) and mono-hydroxyl PEO (PEO-OH) was a good compatibilizer for the PP/PEO blends in which PP-MA also had some compatibilization. The crystallization of the blends was affected by the compatibility between PP and PEO. The interfacial behavior of the compatibilizers had an important effect on crystallization behavior of the PP/PEO blends. PEO showed fractionated crystallization in the PP/PEO blends. This behavior was studied from the view point of the theory of fractionated crystallization. © 1994 John Wiley & Sons, Inc.     

Polyamide 11/poly(hydroxy amino ether) blends: Influence of the blend composition and morphology on the barrier and mechanical properties

A series of PA11/PHAE blends was prepared by melt mixing across the full composition range. Films were obtained for each composition by an extrusion-cast process keeping the same processing conditions. The blends exhibited a two phase morphology. PHAE-rich nodules surrounded by the PA11-rich matrix were observed for PA11 contents higher than 50 wt% in the blends. For lower PA11 weight amounts, PA11 became the dispersed phase and appeared as long fibrillar domains lying in the plane of the film. PA11/PHAE interactions were discussed from DSC and DMA analyses. The effects of the blend composition and morphology on mechanical properties in the linear range and on hydrogen barrier properties were investigated. Hydrogen permeability decreased with increasing amount of PHAE in the blends. A confrontation between the experimental permeability values and the theoretical ones calculated by taking account of the specific properties and morphology of the PA11- and PHAE-rich phases was carried out. In the films series under study, the improvement of hydrogen barrier properties was mainly related to the blend composition whereas a significant effect of the blend morphology was observed on mechanical properties in the rubbery state.     

Birefringence control for binary blends of cellulose acetate propionate and poly(vinyl acetate)

Structure and optical properties for binary blends composed of biomass-based cellulose acetate propionate (CAP) and poly(vinyl acetate) (PVAc) have been studied. It is found that the blends exhibit high level of transparency, although the dynamic mechanical analysis in the solid state suggests that phase separation occurs in the blend. Furthermore, the birefringence resulting from molecular orientation decreases with increasing the content of PVAc. In particular, the blend with approximately 50 wt% of PVAc exhibits no birefringence even after stretching.     

Influence of Reverse Pressure on the Shear Viscosity of Hydrophilic Poly（ethylene terephthalate） Melt

The effect of reverse pressure.on rheological behavior has been studied. The apparatus is a capillary rheometer with counter pressure chamber being held at a high reverse pressure by means of a cock. The results show that with the increase in temperature, the shear viscosity of hydrophilic PET is reduced. It is different that the effect of temperature on shear viscosity is varied under the condition of all shear rates or all pressures, and the effect is more prominent at 50 MPa or at 216 s-1. At the same time, the pressure coefficients decrease with increasing the shear rate and the temperature and tend to reach a constant value nearly at the temperature of 290 °C.     

Blends of poly(carbonate) with poly(styrene) and poly(methylmethacrylate): phase morphology,mechanical, and thermal properties

This paper is concerned with the dependence of mechanical and thermal properties of heterogeneous blends of poly(carbonate) (PC) with poly(methyl-methacrylate) (PMMA) and with poly(styrene) (PS) on the concentration of the components. PS displays a very weak phase coupling in blends with PC, whereas PMMA is characterized by a strong coupling to PC. Experimental results as well as predictions based on composite theories are reported. The general finding is that mechanical properties, such as the tensile modulus and the dynamic shear modulus, as well as thermal properties, such as thermal expansion, are (i) only weakly affected by the occurrence of a phase inversion and of a continuous phase morphology, (ii) vary continuously with the concentration of the components, and (iii) are rather insensitive to the strength of the phase coupling. The theoretical predictions on the concentration—property relationship for these properties, based on a self-consistent approach, agree very well with those observed experimentally. The elongation at break as well as the yield stress, on the other hand, are strongly influenced by the nature of the phase coupling: a discontinuous variation of these properties with the composition is observed for PS/PC blends but not for PMMA/PC blends. The general conclusion is that a set of mechanical and thermal properties of heterogeneous blends can satisfactorily be predicted on the basis of rather simple composite theories.     

Preparation,characterization, and permeability of novel poly (lactic acid)-based blends filled with thymol and ZnO

Novel thin sheets based on poly (lactic acid)/poly (caprolactone)/thermoplastic starch ternary blends were fabricated by incorporating thymol, zinc oxide nanoparticles (ZnO-NPs) and thymol/ZnO-NPs at different concentrations (6, 9, 12 wt% thymol and 1, 3, 5 wt% ZnO). The gas/water vapor barrier properties of the nanocomposites comprising the effects of polar and non-polar molecules and their leading mechanisms were thoroughly discussed. Moreover, the localization preference of ZnO-NPs, morphology along with mechanical, and thermal properties of the nanocomposites were investigated. A significant improvement of 58% in the water vapor impermeability by 5 wt% ZnO and 12 wt% thymol loading was achieved. Finally, the fitting of the Maxwell model on the experimental data revealed that this model cannot correctly predict the permeation behavior of ZnO-filled nanocomposites. Results suggested that these nanocomposites could be capable of being used as the packaging materials with high barrier performance.     

The gas transport properties of amine-containing polyurethane and poly(urethane-urea) membranes

A series of amine-containing polyurethanes and poly(urethane-urea)s based on 4,4′-diphenylmethane diisocyanate and either poly(ethylene glycol) of molecular weights 400 or 600 were prepared as gas separation membranes. The amine functional groups of N-methyldiethanolamine (MDEA) and/or tetraethylenepentamine (TEPA) were introduced into the hard segment as a chain extender. The gas transport data of He, H₂, O₂, N₂, CH₄ and CO₂ in these polymer membranes were determined by using the Barrer's high-vacuum technique and the time-lag method. The restriction of chain mobility has been shown by the formation of hydrogen bonding in the soft segment and hard-segment domains, resulting in the increase in the density, glass transition temperature of soft segments (T_gs). The separation mechanism of various gas pairs used in industrial processes is also discussed. Effect of pressure on permeability of the gases above and below T_gs was studied. It was found that the gas permeability increased or decreased with upstream pressure above T_gs, and should be described by a modified free-volume model. On the other hand, the condensable CO₂ exhibits a minimum permeability at a certain upstream pressure below T_gs. The permeability of He and H₂ were pressure independent above and below the T_gs.     

Molecular relaxation in the blends of polystyrene/poly(2,6-dimethyl-1,4-phenylene oxide) at low temperature

Molecular relaxation behavior in terms of the α, β, and γ transitions of miscible PS/PPO blends has been studied by means of DMTA and preliminary work has been carried out using DSC. From DSC and DMTA (by tan δ), the observed α relaxation (T_α or T_g) of PS, PPO, and the blends, which are intermediate between the constituents, are in good agreement with earlier reports by others. In addition, the β transition (T_β) of PS at 0.03 Hz and 1 Hz is observed at −30 and 20°C, respectively, while the γ relaxation (T_γ) is not observed at either frequency. The T_β of PPO is 30°C at 0.03 Hz and is not observed at 1 Hz, while the T_γ is −85°C at 0.03 Hz and −70°C at 1 Hz. On the other hand, blend composition-independent β or γ relaxation observed in the blends may be a consequence of the absence of intra- or intermolecular interaction between the constituents at low temperature. Thus it is suggested that at low temperature, the β relaxation of PS be influenced solely by the local motion of the phenylene ring, and that the β or γ relaxation of PPO be predominated by the local cooperative motions of several monomer units or the rotational motion of the methyl group in PPO. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1981–1986, 1998     

Effect of introduction of heterocyclic moieties into polymer backbone on gas transport properties of fluorinated poly(ether imide) membranes

The effects of incorporation of heterocyclic moieties into fluorinated poly(ether imide) membranes on their gas transport properties were investigated. Four novel fluorinated poly(ether imide) (PEI) membranes were prepared from four different bis(ether amine)s namely, 4,4-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]biphenyl (BAQP); 1,4-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl] benzene (BATP); 2,6-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]pyridine (BAPy) and 2,5-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]thiophene (BATh), and a fluorinated dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane (6FDA) as a common dianhydride. Gas transport properties of these membranes were measured to investigate the effect of chemical structure on gas permeation and diffusion processes over four different gases (e.g., CH₄, N₂, O₂ and CO₂) at different temperatures (e.g., 35, 45 and 55 °C) at an applied pressure of 3.5 bar. It has been found that at 35 °C the permselectivities of BAPy and BATh based polymeric membranes (6.4 and 6.6, respectively) toward O₂ relative to N₂ are higher in comparison to BAQP and BATP (5.5 and 5.3, respectively) containing PEI membranes. The permeability coefficient of CO₂ for BAPy and BATh (51.92 and 45.31, respectively at 35 °C) based PEI membranes were observed to be much higher than BAQP and BATP based membranes (36.61 and 33.51, respectively at 35 °C) with comparable selectivity values of CO₂ relative to CH₄. All these membranes exhibit higher CO₂/CH₄ selectivity than those of common glassy polymers e.g., cellulose acetate, polysulfone and polycarbonate. The order of permeability of these gases was found as CO₂ > O₂ > N₂ > CH₄. The temperature dependency of permeation and diffusion processes enables to calculate the activation energies of the permeation and diffusion processes for these four different gases through four PEI membranes.     

Crystallization of poly(N-methyldodecano-12-lactam) in blends with poly(styrene-stat-acrylic acid)

Crystallization behaviour of blends of poly(N-methyldodecano-12-lactam) (PMDL) with statistical copolymer poly(styrene-stat-acrylic acid) (PSAA) has been studied by the DSC and WAXD methods. The blend films prepared from dioxane solutions were crystallized at laboratory temperature for five days. Approximate crystallinities of as-prepared neat lower- PMDL 5 and higher-molecular weight PMDL 45 were 28% and 19%, respectively. With increasing PSAA content in the blends the crystallinities decreased sharply. The melting point of the primary crystalline structure of PMDL showed a decreasing dependence on PSAA content in the blends, confirming miscibility of the PMDL-PSAA pair. Recrystallization was strongly suppressed in the blends. The lower-melting endotherm appearing at about 10-15 °C above the crystallization temperature was attributed to melting to less perfect structures formed during secondary crystallization. In neat PMDL, the extent of secondary crystallization was approximately 5-10%. In the blends containing 20% PSAA approximate relative proportion of secondary crystallites on total crystallinity was 40% and 60% for the blends with PMDL 5 and PMDL 45, respectively. WAXD measurements did not reveal any change in crystal modification on blending. Increased T_g in blends of flexible PMDL cannot play a significant role in suppression of primary in favour of secondary crystallization. This was attributed to low mobility of PMDL chains due to dilution effect and specific interactions with the amorphous copolymer component, and, in case of the higher-molecular-weight PMDL, a greater involvement of entanglements. Higher T_g of blends was involved in retardation of non-isothermal crystallization on cooling and subsequent cold crystallization.     

Effects of sulfone/ketone in poly(phthalazinone ether sulfone ketone) on the gas permeation of their derived carbon membranes

A series of copolymer, poly(phthalazinone ether sulfone ketone)s (PPESKs) with the sulfone over ketone unit (S/K) ratio varying from 20/80, 50/50 to 80/20, were used as precursors to prepare carbon membranes. The effects of chemical structure as S/K ratio of PPESKs on the microstructure and gas separation performance of their derived carbon membranes were mainly investigated. The properties of PPESKs were detected in terms of density, fractional free volume, char yield, interlayer distance and glass transition temperature. During the formation process of carbon membranes (i.e., stabilization and pyrolysis), the changes in functional groups, microstructural parameters and gas permeation were monitored by FTIR, X-ray diffraction, TEM and single gas permeation techniques. The results have shown that the microstructure and gas permeation of obtained carbon membranes are significantly affected by the S/K ratio in precursor PPESKs. Carbon membranes exhibit higher selectivity and lower permeability when prepared at low pyrolytic temperature (i.e., 650 °C and 800 °C) and from PPESKs with S/K ratio equaling 50/50, followed with 20/80 and 80/20. As for carbon membranes prepared at high pyrolytic temperature (i.e., 950 °C), the selectivity order of them is well in accordance with S/K mole ratio in precursor PPESKs: 20/80 > 50/50 > 80/20, and vice versa for permeability.     

Effect of molecular interactions on the miscibility and structure of polymer blends

The effect of polymer-polymer interactions on the miscibility and macroscopic properties of PVC/PMMA, PVC/PS and PMMA/PS blends were studied in the entire composition range. The miscibility of the components was characterized by the Flory-Huggins interaction parameter or by quantities related to it. Thermal analysis, light transmittance measurements, and scanning electron microscopy were carried out on the blends and their mechanical properties were characterized by tensile tests. Interactions were analyzed by infrared spectroscopy and contact angle measurements. All three polymer pairs form heterogeneous blends, but the strength of molecular interactions is different in them, the highest is in PVC/PMMA system resulting in partial miscibility of the components and beneficial mechanical properties. The structure of these blends depends strongly on composition. A phase inversion can be observed between 0.5 and 0.6 PMMA content accompanied with a significant change in structure and properties. The PVC/PS and the PMMA/PS pairs are immiscible, though the results indicate the partial solubility of the components. The analysis of the surface characteristics of the components and the comparison of quantities derived from them with miscibility as well as with the macroscopic properties of blends revealed that blend properties cannot be predicted in this way, since they are affected by several factors.