Phase and crystallization behavior of solution-blended poly(ether ether ketone) and poly(ether imide)

Results on solution-blended poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) blends are reported. Dichloroacetic acid was used as the cosolvent for blending. PEEK and PEI are confirmed to be miscible in the melt. The glass transition, T_g, behavior obeys the simple Fox equation or the Gordon-Taylor equation with the adjustable coefficient k = 0.86. This agrees with prior data on melt-blended PEEK/PEI blends. The T_g width of the amorphous PEEK/PEI blends was found to be broader than that of the pure components. The maximum broadening is about 10°C. The specific volume of the amorphous PEEK/PEI blends shows a slight negative deviation from linearity, indicating favorable interaction between PEEK and PEI. The spherulitic growth and resultant blend morphology at 270°C were studied by a cross-polarized optical microscope. The radial growth rate of PEEK spherulites formed from the miscible melt at 270°C decreases from 3.04 μm/min for PEEK/PEI 90/10 blend to 0.77 μm/min for PEEK/PEI 70/30 blend. The decrease in crystalization rate of PEEK from PEEK/PEI blends is attributable to the increase in blend T_g. A linear growth was observed for PEEK spherulites formed from miscible melt at 270°C in the early growth stage. The spherulitic growth deviated from linearity in the late stage of growth. PEEK spherulites formed from the miscible PEEK/PEI melt at 270°C are essentially volume-filling. The branches of the spherulites become more clear for PEEK spherulites formed from the blend than that formed from pure PEEK melt.     

Crystallization behavior and mechanical properties of poly(aryl ether ether ketone)/poly(ether imide) blends

Crystallinity and mechanical properties of blends with different amounts of semicrystalline poly(aryl/ ether ether ketone) (PEEK) and amorphous poly(ether imide) (PEI) polymers have been studied. The blends, prepared by melt mixing, have been investigated by differential scanning calorimeter (DSC) to analyze the miscibility between the components and the final crystalline content. Moreover, for the 20/80 PEEK/PEI blend, crystallization in dynamic and isothermal conditions has been carefully investigated in order to find proper conditions for maximum development of crystallinity. Mechanical tests (static and dynamic) have been performed to evaluate the properties of the as-molded and crystallized blends and to compare them with those of crystalline PEEK and amorphous PEI neat resins. Finally, a few SEM observations have been performed to compare the fractured surface of the blend with those of the pure constituents.     

Liquid-crystal polymer fiber production and reinforcing in ribbons of poly(ether imide)/vectra-B blends

Blends of poly(ether imide) (PEI) with a liquid-crystal polymer (Vectra-B950) were extruded into ribbon. Two PEI-rich compositions at three different draw ratios were obtained, and the miscibility and morphology of the blends analyzed. The tensile properties of the ribbons were determined, both in the processing and in the perpendicular direction and were compared with those of the pure PEI. Results showed that PEI/Vectra blends are immiscible and that complex structures were obtained as a consequence of extrusion. The blend composition and the draw ratio determined to a great extent the mechanical properties of the blends. The interfacial adhesion between blend components is low, but enough to break the LCP fibers when significant aspect ratios are attained.     

Intermolecular interaction and conformation in poly(ether ether ketone)/poly(ether imide) blends — An infrared spectroscopic investigation

The intermolecular interaction and the conformation in miscible blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) have been investigated by Fourier-transform infrared (FTIR) spectroscopy. The intensity of the C=O out-of-phase stretching (1725 cm^–1) of PEI shows a minimum at 70 wt% PEI, whereas that of the C=O in-phase stretching (1778 cm^–1) is not perturbed by blending. These intensity variations have been attributed to the effect of blending on the coplanarity of the two imide rings bridged by the phenylene group. Change in coplanarity of these two imide rings alters the intensity of the C=O out-of-phase stretching, but it can not affect the intensity of the C=O in-phase stretching. When the two imide rings are perpendicular to each other, the intensity of the C=O out-of-phase stretching is shown to reach the minimum, corresponding to the observation at 70 wt% PEI. The difference spectra (blend - PEEK - PEI) reveal that the bands associated with the diphenyl ether groups in PEEK are modified by blending with PEI. It is proposed that the favorable interaction takes place between the oxygen lone-pair electrons of the ether group in PEEK and the electron-deficient imide rings in PEI.     

Poly(ether ether ketone)/poly(aryl ether sulfone) blends: Relationships between morphology and mechanical properties

Mechanical properties such as the tensile modulus, yield (break) strength, and elongation to break (or yield) are measured for multiphase poly(ether ether ketone) (PEEK)/poly(aryl ether sulfone) (PES) blends. Specimens with three different levels of thermal histories (quenched, as‐molded, and annealed) are prepared in order to study their effects on the mechanical properties of PEEK/PES blends. Synergistic behavior is observed in the tensile modulus and tensile strength of the blends in almost the whole range of compositions. The ductility of quenched blends measured as the elongation to break (yield) shows an unexpected synergistic behavior in the blend containing 90 wt % PEEK, although a negative deviation from additive behavior is observed in the rest of the compositions. A ductile–brittle transition is observed between 50 and 75 wt % PEEK in the blend. The ductile–brittle transition in as‐molded blends shifts to 75–90 wt % PEEK. Annealed blends show predominantly brittle behavior in the whole composition range. The experimental data are further correlated with the theoretically predicted results based on various composite models. Although the prediction based on these equations fails to fit the experimental data in the whole composition range, the simplex equations that are normally used for blends showing synergistic behavior produced a reasonable fit to the experimental data. The mechanical properties obtained for different blend compositions are further correlated with their morphology as observed by scanning electron microscopy. Morphological observation shows a two‐phase morphology in PES‐rich blends, which is an interlocked morphology in which the disperse phase is not clearly visible in PEEK‐rich blends, and a cocontinuous type of morphology for a 50/50 composition. Considerable permanent deformation of both the disperse and matrix phase, especially in the case of quenched tensile specimens, demonstrates the remarkable adhesion present between the two phases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2887–2905, 2003     

聚醚醚酮共混改性研究进展

综述了聚醚醚酮（PEEK）、聚醚酰亚胺（PEI）、聚四氟乙烯（PTFE）、热致液晶（TLCP）和聚醚砜（PES）等高性能工程塑料的共混改性研究进展,详细探讨了各种PEEK共混物的相容性、结晶行为、微观结构、热行为和力学性能等性能特征。PEEK与PEI在熔融和无定形状态下完全相容,常用于PEEK的结晶行为和微观结构的基础研究;与PTFE、TLCP、PES共混分别是提高PEEK的摩擦磨损性能、加工性能和热稳定性的有效手段。各种共混物的相容性好坏对其结晶行为和微观结构有重要影响,从而影响了共混物的力学性能。在此基础上,对PEEK共混改性领域进一步的研究方向和内容进行了讨论。     

Solid state and mechanical properties of injection molded poly(ether ether ketone)/polyarylate blends

Blends of poly(ether ether ketone) (PEEK) and bisphenol-A polyarylate (PAr) were directly prepared during the plasticization step of an injection molding machine and their solid-state and mechanical behaviors were studied. Despite the fact that PEEK-rich blends were apparently miscible by differential scanning calorimetry (DSC), from the dynamic-mechanical analysis (DMTA) results all the blends were composed of (a) a crystalline PEEK phase, (b) a practically pure amorphous PEEK phase, and (c) a PAr-rich phase richer in PEEK as the PEEK content in the blends increased. Annealed blends showed a poor mechanical performance in the PAr-rich region, but the PEEK-rich blends showed additive modulus of elasticity and tensile strength, and ductility and impact strength values similar to those of the highest of the two pure components. All the as-molded low-crystalline blends presented a synergistic behavior in the modulus of elasticity, as well as, surprisingly, in ductility and impact strength in the intermediate and slightly majority PEEK compositions. The different mechanical response of the components in fine dispersed phases and in macroscopic tensile specimens may account for the observed results.     

Tensile behaviour and fracture toughness of poly(ether ether ketone)/poly(ether imide) blends

Summary The bulk tensile behaviour of poly(ether ether ketone) and poly(ether imide) homopolymers and their blends has been investigated, and the temperature and strain rate dependence of the yield stress discussed in terms of simple Eyring rate theory. In fracture mechanics tests, the K_IC of PEEK was found to decrease significantly with increasing test speed, whereas the K_IC of PEI showed little rate sensitivity. Therefore, although a gradual increase in K_IC with increasing PEEK content was observed in the blends at low loading rates, this effect was anticipated to be less pronounced at higher loading rates.     

Thermal properties of melt‐blended poly(ether ether ketone) and poly(ether imide)

The thermal properties of blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) prepared by screw extrusion were investigated by differential scanning calorimetry. From the thermal analysis of amorphous PEEK–PEI blends which were obtained by quenching in liquid nitrogen, a single glass transition temperature (T_g) and negative excess heat capacities of mixing were observed with the blend composition. These results indicate that there is a favorable interaction between the PEEK and PEI in the blends and that there is miscibility between the two components. From the Lu and Weiss equation and a modified equation from this work, the polymer–polymer interaction parameter (χ₁₂) of the amorphous PEEK–PEI blends was calculated and found to range from −0.058 to −0.196 for the extruded blends with the compositions. The χ₁₂ values calculated from this work appear to be lower than the χ₁₂ values calculated from the Lu and Weiss equation. The χ₁₂ values calculated from the T_g method both ways decreased with increase of the PEI weight fraction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 733–739, 1999     

Spherulitic growth kinetics in miscible blends of poly(ether ether ketone) and poly(ether imide)

Growths of poly(ether ether ketone) (PEEK) spherulites from both pure melt and its miscible blends with poly(ether imide) (PEI) have been studied by polarized optical microscopy. The nucleation density of PEEK spherulites was depressed upon blending with PEI, which can be attributed to the reduction in degree of supercooling arising from equilibrium melting point depression. A modified Lauritzen-Hoffman (L-H) theory was adopted to analyze the growth kinetics. Regime III-II transition was observed with the transition temperature decreasing with increasing PEI composition. Assuming free rotations of the virtual bonds in PEEK molecule, the side surface free energy of 12.0 erg/cm² was calculated from the characteristic ratio. The fold surface free energy of 188 erg/cm² and work of chain folding of 12.3 kcal/mol were then obtained from the modified L-H analysis.     

Blends of phenolphthalein poly(ether ether ketone) and a thermotropic liquid crystalline copolyester

Blends of phenolphthalein poly(ether ether ketone) (PEK-C) and a thermotropic liquid crystalline copolyester (LCP), poly[(1-phenylethyl-p-phenylene terephthalate)-co-(1-cumyl-p-phenylene terephthalate)], was prepared via melt mixing. The studies of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) indicate that the PEK-C/LCP blends display two glass transition temperatures which correspond to those of PEK-C- and LCP-rich phases, respectively. The PEK-C/LCP blends were judged to be partially miscible. Scanning electron microscopy (SEM) was employed to examine the morphology of the blends, and it was observed that all the PEK-C/LCP blends displayed a phase-separated structure. The interface between the PEK-C- and LCP-rich phases is poor. The Young's modulus of the PEK-C/LCP blends was found to increase with LCP content due to the high modulus of the LCP. However, the tensile strength and the elongation at break of the blends greatly decreases with increase of LCP content, owing to the poor interfacial adhesion. From the thermogravity analysis (TGA), it was observed that all the blends exhibited a two-step weight loss mechanism, and the thermal degradation onset temperature of the blends was lowered with the addition of LCP content. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1923–1931, 1998     

Miscibility and phase behavior in blends containing random copolymers of poly(ether ether ketone) and phenolphthalein poly(ether ether ketone)

The miscibility and phase behavior of polysulfone (PSF) and poly(hydroxyether of bisphenol A) (phenoxy) with a series of copoly (ether ether ketone) (COPEEK), a random copolymer of poly(ether ether ketone) (PEEK), and phenolphthalein poly(ether ether ketone) (PEK-C) was studied using differential scanning calorimetry. A COPEEK copolymer containing 6 mol % ether ether ketone (EEK) repeat units is miscible with PSF, whereas copolymers containing 12mol % EEK and more are not. COPEEK copolymers containing 6 and 12 mol % EEK are completely miscible with phenoxy, but those containing 24 mol % EEK is partially miscible with phenoxy. Moreover, a copolymer containing 17 mol % EEK is partially miscible with phenoxy; the blends show two transitions in the midcomposition region and single transitions at either extreme. Two T_gs were observed for the 50/50 blend of phenoxy with the coplymer containing 17 mol % EEK, whereas a single composition-dependent T_g appeared for all the other compositions. An FTIR study revealed that there exist hydrogen-bonding interactions between phenoxy and the copolymers. The strengths of the hydrogen-bonding interactions in the blends of the COPEEK copolymers containing 6 and 12 mol % EEK are the same as that in the phenoxy/PEK-C blend. However, for the blends of copolymers containing 17, 24, and 28 mol % EEK, the hydrogen-bonding interactions become increasingly unfavorable and the self-association of the hydroxyl groups of phenoxy is preferable as the content of EEK units in the copolymer increases. The observed miscibility was interpreted qualitatively in terms of the mean-field approach. © 1996 John Wiley & Sons, Inc.     

Compatibility studies of sulfonated poly(ether ether ketone)–poly(ether imide)–polycarbonate ternary blends

Binary blends of the sulfonated poly(ether ether ketone) (SPEEK)–poly(ether imide) (PEI) and SPEEK–polycarbonate (PC), and ternary blends of the SPEEK–PEI–PC, were investigated by differential scanning calorimetry. SPEEK was obtained by sulfonation of poly(ether ether ketone) using 95% sulfuric acid. From the thermal analysis of the SPEEK–PEI blends, single glass transition temperature (T_g) was observed at all the blend composition. For the SPEEK–PC blends, double T_gs were observed. From the results of thermal analysis, it is suggested that the SPEEK–PEI blends are miscible and the SPEEK–PC blends are immiscible. Polymer–polymer interaction parameter (χ₁₂) of the SPEEK–PEI blends was calculated from the modified Lu and Weiss equation, and found to range from −0.011 to −0.825 with the blend composition. For the SPEEK–PC blends, the χ₁₂ values were calculated from the modified Flory–Huggins equation, and found to range from 0.191 to 0.272 with the blend composition. For the SPEEK–PEI–PC ternary blends, phase separation regions that showed two T_gs were found to be consistent with the spinodal curves calculated from the χ₁₂ values of the three binary blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2488–2494, 2000     

Mechanical properties of poly(ether ether ketone)/poly(ether ketone) blends: Use of simple models relating normalized tensile parameters

In this study, mechanical properties such as tensile properties, flexural properties, and Izod impact strength of poly(ether ether ketone) (PEEK) and poly(ether ketone) (PEK) blends at PEK concentration from 0 to 0.42 volume fraction were studied. The blends of PEEK and PEK of different compositions were prepared by extrusion in a single‐screw extruder. With increase in the PEK concentrations, the tensile strength, flexural strength, and modulus increased whereas the tensile modulus and the impact strength decreased. Homogeneous dispersion and adhesion of PEK in PEEK was shown by the morphological studies. Crystallinity of blends influenced the tensile modulus and the impact strength. Using simple models to relate normalized tensile parameters where the data were divided by the crystallinity of the blends and of the PEEK matrix, respectively, supported the experimental results. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Compatibility in immiscible poly(ether ether ketone)/poly(ether sulfone) blends

Both as-molded and annealed poly(ether ether ketone) (PEEK)/poly(ether sulfone) (PES) blends have been prepared by direct injection molding. The system has been found to be immiscible at all compositions; however, as a result mainly of the produced morphology, it surprisingly maintains to a very great extent the excellent mechanical performance of both of the pure components. This mechanical response is compared with that of the compression molded blends. The ductility of these blends when quenched appears close to the linear between that of the two components. Leaving aside possible morphological and excess free volume of mixing effects, it is in part attributed to the nature of the blend itself. © 1995 John Wiley & Sons, Inc.     

Reactively formed ENPT copolymers as compatibilizers in ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide)

The compatibility of ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide) (PEN/PPT/PEI) was studied by examining the transesterification of PEN and PPT. ENPT copolymers were formed in situ as compatibilizers between PPT and PEI components in ternary blends. Differential scanning calorimetric (DSC) results for ternary blends showed the immiscibility of PEN/PPT/PEI, but ternary blends of all compositions were phase‐homogeneous after heat treatment at 300°C for more than 60 min. Annealing samples at 300°C yielded amorphous blends with a clear, single glass transition temperature (T_g), as the final state. Additionally, ENPT copolymer improved the compatibility of ENPT/PPT/PEI blends, yielding a homogeneous phase in the ENPT‐rich compositions. The morphology of the ENPT/PPT/PEI blends was altered from heterogeneous to homogeneous by controlling the concentration of PPT in the ENPT copolymers as well as the concentration of the ENPT copolymers. Moreover, a homogeneous phase with a clear T_g was observed when the concentration of PPT in the ENPT copolymer fell to 70 wt% in the ENPT/PEI = 50/50 blends. Experimental results indicate how the concentration of PPT in the ENPT copolymer affects miscibility in the ENPT/PEI blends. POLYM. ENG. SCI. 46:337–343, 2006. © 2006 Society of Plastics Engineers     

Synthesis of poly(ether ether ketone)-block-polyimide copolymer and its compatibilization for poly(ether ether ketone)/thermoplastic polyimide blends

Novel poly(ether ether ketone)-block-polyimide copolymers (PEEK-b-PI) with different block length were prepared by the polycondensation of amino-terminated poly(ether ether ketone) oligomer and anhydride-terminated polyamic acid oligomer. As the compatibility agent, PEEK-b-PI was added to the poly(ether ether ketone)/thermoplastic polyimide (PEEK/TPI) blend, and blends of PEEK/TPI/PEEK-b-PI were prepared by melt extrusion. Morphology observation showed the domain size of the dispersed phase was significantly reduced with the addition of PEEK-b-PI having optimized block length, which suggested reduced interfacial tension and enhanced interfacial adhesion. The compatibilizing effect was further proven by the change of the glass transition temperature of PEEK and TPI, which shifted closer to each other. As a result, the mechanical properties of PEEK/TPI blends were significantly improved with the addition of the PEEK-b-PI. In particular, 5 wt% content of PEEK-b-PI can increase the elongation at break of the blend by about 200%.     

Miscibility and transesterification in ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide)

Miscibility and morphology of poly(ethylene 2,6‐naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide) (PEN/PPT/PEI) blends were studied by differential scanning calorimetry (DSC), optical microscopy (OM), proton nuclear magnetic resonance imaging (¹H‐NMR), and wide‐angle X‐ray diffraction (WAXD). OM and DSC results from ternary blends revealed the immiscibility of PEN/PPT/PEI blends, but ternary blends of all compositions were phase‐homogeneous following heat treatment at 300°C for over 60 min. Annealing samples at 300°C yielded an amorphous blend with a clear and single T_g at the final state. Experimental data from ¹H‐NMR revealed that PEN/PPT copolymers (ENPT) were formed by the so‐called transesterification. The effect of transesterification on glass transition and crystallization was discussed in detail. The sequence structures of the copolyester were identified by triad analysis, which showed that the mean sequence lengths became shorter and the randomness increased with heating time. The results reveal that a random copolymer improved the miscibility of the ternary blends, in which, the length of the homo segments in the polymer chain decreased and the crystal formation was disturbed because of the irregularity of the structure, as the exchange reaction proceeded. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3840–3849, 2006     

Miscible blends of poly(aryl ether ketone)s and polyetherimides

A new class of high performance engineering resins, poly(aryl ether ketone)s, has emerged with a property balance not offered by existing polymeric materials. Blends of poly(aryl ether ketone)s with other polymers have not been described in the open literature, although several patents have revealed interesting and important properties of certain blend combinations. Ultem polyetherimide has been found to be miscible over the entire composition range and as a consequence is a very effective heat distortion temperature builder, particularly if the poly(aryl ether ketone) is allowed to crystallize. Crystallization kinetics and mechanical properties were studied as a function of blend composition and poly(aryl ether ketone) melting point. The blends exhibited a maximum in toughness at intermediate compositions along with an accompanying maximum in poly(aryl ether ketone) crystallinity. The chemical resistance of the polyetherimide is significantly improved with the addition of a poly(aryl ether ketone). In organic chemicals, the improvement was expected when tensile stress was plotted vs. log time to rupture. However, in aqueous bases, the resistance of the blends was much greater than anticipated. This property profile suggests that these blends will be useful as thermoplastic composite matrix resins.     

Miscibility and crystallization behavior of poly(ether ether ketone ketone)/poly(ether imide) blends

The miscibility and crystallization behavior of poly(ether ether ketone ketone) (PEEKK)/poly(ether imide) (PEI) blends prepared by melt‐mixing were investigated by differential scanning calorimetry. The blends showed a single glass transition temperature, which increased with increasing PEI content, indicating that PEEKK and PEI are completely miscible in the amorphous phase over the studied composition range (weight ratio: 90/10–60/40). The cold crystallization of PEEKK blended with PEI was retarded by the presence of PEI, as is apparent from the increase of the cold crystallization temperature and decrease of the normalized crystallinity for the samples anealed at 300°C with increasing PEI content. Although the depression of the apparent melting temperature of PEEKK blended with PEI was observed, there was no evidence of depression in the equilibrium melting temperature. The analysis of the isothermal crystallization at 313–321°C from the melt of PEEKK/PEI (100/0, 90/10, and 80/20) blends suggested that the retardation of crystallization of PEEKK is caused by the increase of the crystal surface free energy in addition to the decrease of the mobility by blending PEI with a high glass transition temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 769–775, 2001