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     

Mechanical properties and morphology of polymer blends of poly(ethylene terephthalate) and semiflexible thermotropic liquid crystalline polyesters

Two thermotropic liquid crystalline polyesters (TLCPs) with long flexible spacer groups in the main chain were prepared by melt polymerization: one was a homopolymer with only decane groups (LCPHO) and the other was a copolymer with hexane or decane groups (LCPCO) between mesogen units. These polyesters were blended with a matrix polymer of poly(ethylene terephthalate) (PET). Scanning electron microscopy (SEM) revealed the excellent interfacial adhesion between polyester and PET, and the large aspect ratio of polyester microfibrils in the blend fiber made by extruding and drawing the blend through a die. The aspect ratio was estimated by using the modified Halpin-Tsai equation. The fiber with LCPHO showed more extensive fibril formation than that with LCPCO.     

Crystallization kinetics of poly(ethylene terephthalate) with thermotropic liquid crystalline polymer blends

The isothermal and dynamic crystallization behaviors of polyethylene terephthalate (PET) blended with three types of liquid crystal polymers, i.e., PHB60–PET40, HBA73–HNA27, [(PHB60–PET40)–(HBA73–HNA27) 50 : 50], have been studied using differential scanning calorimetry (DSC). The kinetics were calculated using the slope of the crystallization versus time plot, the time for 50% reduced crystallinity, the time to attain maximum rate of crystallization, and the Avrami equation. All the liquid crystalline polymer reinforcements with 10 wt % added accelerated the rate of crystallization of PET; however, the order of the acceleration effect among the liquid crystalline polymers could not be defined from the isothermal crystallization kinetics. The order of the effect for liquid crystalline polymer on the crystallization of PET is as follows: (PHB60–PET40)–(HBA73–HNA27) (50 : 50); HBA73–HNA27; PHB60–PET40: This order forms the dynamic scan of the DSC measurements. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1383–1392, 1998     

Study on phenolphthalein poly(ether sulfone)‐modified cyanate ester resin and epoxy resin blends

In this work, the phenolphthalein poly(ether sulfone) (PES‐C)‐modified cyanate ester (CE) and epoxy (EP) blends were prepared. This work mainly discusses the curing behaviors, fracture toughness, dynamic mechanical properties, and thermal and mechanical properties of the blends. The Fourier transform infrared and differential scanning calorimetric analyses are used to confirm the curing behaviors, demonstrating that the main reaction pathways are not varied with the addition of PES‐C, but the reaction rate could be evidently accelerated. The fracture morphologies of the blends are observed by Scanning electron microscope (SEM) and the fracture causes of the failed surface are also analyzed. With the addition of PES‐C, the modified blends display higher fracture toughness (K_Ic) and impact strength when compared with neat CE. Domain sizes of the blends first increase then decrease with the addition of PES‐C. The results of dynamic mechanical analysis and thermogravimetric analysis show that the T_g, storage modulus, and thermal stability of the crosslink network slightly decreases with the addition of PES‐C. The mechanical strength of blends with the addition of PES‐C is far better than that of the blends without PES‐C both at ambient temperature and elevated temperature. POLYM. ENG. SCI., 55:2591–2602, 2015. © 2015 Society of Plastics Engineers     

Synthesis of multi‐block copolymer and its compatibilization to the blends of poly(ether ether ketone) with thermotropic liquid crystalline polymer

A multiblock copolymer (BCP) containing amorphous poly(aryl ether ketone) (PAEK) and thermotropic liquid crystalline polymer (TLCP) segments was synthesized. The chemical structure and properties of BCP were characterized by fourier‐transform infrared spectrometer (FTIR), differential scanning calorimeter (DSC), gel permeation chromatograms (GPC), thermogravimetry analysis, polar light microscope (PLM), and solubility test respectively. BCP can dissolve in chloroform because of soluble PAEK block bonded with TLCP block, which was insoluble. The peak of the original PAEK oligomer was no more present in the GPC traces of the block copolymer. These facts indicated that polymer synthesized should be copolymers of the two components rather than blends. A single T_g at 138.1°C and broad melting endotherm at 315.7°C can be observed. The liquid crystalline texture of BCP showed uniformity in the view after heat treated for 10 min above its T_m under PLM. Ternary blends of poly(ether ether ketone) (PEEK)/TLCP/BCP were prepared by extrusion and characterized by DSC. DSC results showed that the crystallization temperature of PEEK phase in the blends shifted higher with the addition of TLCP. Wide angle X‐ray diffraction investigations indicated that the crystalline structure of PEEK was not disturbed by blending or compatibilizing. Scanning electron microscope and mechanical tests confirmed the compatibilizing effect of BCP. Reduction in dispersed phase TLCP size was observed when 2 phr by weight of compatibilizer was added to the blend. Measurement of the tensile properties showed increased elongation as well as improved modulus and strength to some extent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Miscibility and phase behavior in blends of phenolphthalein poly(ether sulfone) and poly(hydroxyether of bisphenol A)

Miscibility and phase behavior in the blends of phenolphthalein poly(ether sulfone) (PES-C) with poly(hydroxyether of bisphenol A) (PH) were investigated by means of differential scanning calorimetry (DSC), high resolution solid state nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR). It was found that the homogeneity of the as-prepared blends depended on the solvents used; N,N-dimethylformamide (DMF) provided the segmental mixing for PH and PES-C, which is confirmed by the behavior of single, composition-dependent glass transition temperatures (T_g's). To examine the homogeneity of the blends at the molecular level, the proton spin-lattice relaxation times in the rotating frame T_1ρ(H) were measured via ¹³C CP/MAS NMR spectroscopy as a function of blend composition. In view of the T_1ρ(H) values, it is concluded that the PH and PES-C chains are intimately mixed on the scale of 20-30 Å. FTIR studies indicate that there were the intermolecular specific interactions in this blends, involved with the hydrogen-bonding between the hydroxyls of PH and the carbonyls of PES-C, and the strength of the intermolecular hydrogen bonding is weaker than that of PH self-association. At higher temperature, the PH/PES-C blends underwent phase separation. By means of thermal analysis, the phase boundaries of the blends were determined, and the system displayed the lower critical solution temperature behavior. Thermogravity analysis (TGA) showed that the blends exhibited the improved thermal stability, which increases with increasing PES-C content.     

Impact behavior of phenolphthalein poly(ether sulfone)/ultrahigh molecular weight polyethylene blends

This work presents the structure and impact properties of phenolphthalein poly(ether sulfone) blended with ultrahigh molecular weight polyethylene (PES-C/UHMWPE) at different compositions. The addition of UHMWPE can considerably improve the Charpy and Izod impact strength of the blends. The fracture surface is examined to demonstrate the toughening mechanics related to the modified PES-C resin. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 113–118, 1998     

Synthesis and characterization of thermotropic liquid crystalline poly(azomethine ether)s

Two series of monomers, namely 4,4′-diformyl-α,ω-diphenoxydecane and 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane, were prepared from 1,10-dibromodecane with p-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde (vanillin), respectively. The poly(azomethine ether)s were prepared by solution polycondensation using 4,4′-diformyl-α,ω-diphenoxydecane, 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane with various diamines. The monomers and polymers were characterized by intrinsic viscosity, FT-IR, ¹H, and ¹³C NMR spectroscopy. The thermogravimetric analysis reveals that the polymers are stable up to 320-500 °C and decomposed with good char yield. The thermotropic liquid crystalline properties of the polymers were examined by differential scanning calorimetry (DSC) and their textures observed under hot stage optical polarized microscopy (HOPM). All the polymers were exhibited thermotropic liquid crystalline properties except tetramethylene diamines-based polymers.     

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     

Miscibility and mechanical properties of poly(ether imide)/poly(ether ether ketone)/liquid crystalline polymer ternary blends

This paper is concerned with a novel ternary blend composed of poly(ether imide) (PEI), poly(ether ether ketone) (PEEK) and a liquid crystalline polymer (LCP; HX4000, Du Pont). Different compositions were prepared by extrusion and injection moulding. Dynamic mechanical thermal analysis and the observation of the fracture surfaces, before and after annealing, allowed determination of the cold crystallization temperatures and miscibility behaviour of these systems. PEEK/PEI blends are known from previous studies to be miscible at all compositions. In this case it was observed that the PEEK/HX4000 blend was miscible up to 50 wt% HX4000 but partially miscible above this value. The PEI/HX4000 blends were found to be partially miscible in the whole concentration range. As a result, some ternary blend compositions exhibited only one phase, while others exhibited two phases. The measurement of the tensile properties showed that ternary blends with high modulus can be obtained at high LCP loadings, while compositions with high ultimate tensile strength can be obtained with high loadings of PEI or PEEK.     

Synthesis and properties of poly(ether ether ketone ketone)–poly(ether sulfone) block copolymers

Poly(ether ether ketone ketone)-poly(ether sulfone) (PEEKK/PES) block copolymers were prepared from the corresponding oligomers via a nucleophilic aromatic substitution reaction, and the M _n of the PEEKK segment was fixed at 12,000, while the M _n's of the PES segment ranged from 250 to 12,680. The different properties of the copolymers were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The results showed that the relationship between T_g and compositions of copolymers approximately followed the formula 1/T_g = W₂/T_g2. The PES content and the segment length of the copolymers had a significant influence on their melting points and crystallization behavior. The thermal properties and dynamic mechanical behavior of the copolymers were also studied. In the study of isothermal crystallization, the copolymers have the same nucleation mechanism and crystal growth as that of pure PEEKK. Owing to the introduction of the PES segment into the PEEKK main chain, it increases the free energy which forms the critical crystal nucleus and produces a resistant action to the whole crystallization process of the PEEKK segment. © 1996 John Wiley & Sons, Inc.     

Thermal properties,structure and morphology of PEEK/thermotropic liquid crystalline polymer blends

The dynamic crystallization and subsequent melting behaviour of poly(aryl ether ether ketone), PEEK, and its blends with a thermotropic liquid crystalline polymer, Vectra^®, have been studied using differential scanning calorimetry, optical microscopy and wide‐angle and small‐angle X‐ray diffraction (WAXS and SAXS) techniques in a wide compositional range. Differences in crystallization rates and crystallinities were related to the structural and morphological characteristics of the blends measured by simultaneous real‐time WAXS and SAXS experiments using synchrotron radiation and optical microscopy. The crystallization process of PEEK in the blends takes place in the presence of the nematic phase of Vectra and leads to the formation of two different crystalline families. The addition of Vectra reduces the crystallization rate of PEEK, depending on composition, and more perfect crystals are formed. An increase in the long period of PEEK during heating was generally observed in the blends at all cooling rates. Copyright © 2003 Society of Chemical Industry     

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.     

Fibers from blends of PET and thermotropic liquid crystalline polymer

Blends of poly(ethylene terephthalate-Co-p-oxybenzoate), PET/PHB, with poly(ethylene terephthalate), PET, have been studied in the form of as-spun and drawn fibers. DSC melting and crystallization results show that the PET is compatible with LCP and the crystallization of PET decreases by the addition of LCP in the matrix. Upon heating above the crystal melting temperature of PET, the blend shows good dispersion of LCP in the PET matrix. Wide angle X-ray diffraction of drawn blended fibers show the possible formation of LCP oriented domains. The mechanical properties of drawn fiber up to 10 wt% LCP composition exhibit significant improvement in tensile modulus and tensile strength with values of 17.7 GPa and 1.0 GPa, respectively. Values of modulus are compared with prediction from composite theory, assuming the blend system as nematic domains of LCP. dispersed in PET matrix.     

Friction and wear behavior of proton‐implanted phenolphthalein poly(ether sulfone)

Blocks of phenolphthalein poly(ether sulfone) (PES‐C) were implanted with 110 keV protons in four doses: 1 × 10¹⁴, 5 × 10¹⁴, 2.5 × 10¹⁵, and 1.25 × 10¹⁶ ions/cm². The structures of the pristine and implanted PES‐C blocks were characterized by FTIR–ATR and X‐ray photoelectron spectroscopy (XPS), whereas their friction and wear behavior were investigated with an M‐2000 friction and wear tester at room temperature in an ambient atmosphere. The results revealed that with an increased implantation dose, it took more time for the friction coefficient to become smaller and level off when the dose did not exceed 10¹⁶ ions/cm². At the highest dose, 1.25 × 10¹⁶ ions/cm², the friction coefficient started smaller but increased quickly and leveled off at a higher number. In addition, the wear rate first increased and then decreased. When the dose exceeded 10¹⁶ ions/cm², the wear rate of the sample showed an obvious decrease. The FTIR–ATR spectra showed that partial degradation took place on the surface of PES‐C after proton implantation, and when the dose reached or exceeded 2.5 × 10¹⁵ ions/cm², a new broad peak between 1600 and 1800 cm^?1 appeared, showing that a carbon‐rich structure had formed on the sample surface. XPS analyses justified the FTIR–ATR results, including the formation of amorphous carbon and the partial degradation, which was responsible for the variety of friction and wear behaviors of PES‐C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3116–3119, 2006     

Rheological properties in blends of poly(aryl ether ether ketone) and liquid crystalline poly(aryl ether ketone)

Rheological properties of the blends of poly(aryl ether ether ketone) (PEEK) with liquid crystalline poly(aryl ether ketone) containing substituted 3‐trifluoromethylbenzene side group (F‐PAEK), prepared by solution precipitation, have been investigated by rheometer. Dynamic rheological behaviors of the blends under the oscillatory shear mode are strongly dependent on blend composition. For PEEK‐rich blends, the systems show flow curves similar to those of the pure PEEK, i.e., dynamic storage modulus G′ is larger than dynamic loss modulus G″, showing the feature of elastic fluid. For F‐PAEK‐rich systems, the rheological behavior of the blends has a resemblance to pure F‐PAEK, i.e., G″ is greater than G′, showing the characteristic of viscous fluid. When the PEEK content is in the range of 50–70%, the blends exhibit an unusual rheological behavior, which is the result of phase inversion between the two components. Moreover, as a whole, the complex viscosity values of the blends are between those of two pure polymers and decrease with increasing F‐PAEK content. However, at 50% weight fraction of PEEK, the viscosity‐composition curves exhibit a local maximum, which may be mainly attributed to the phase separation of two components at such a composition. The changes of G′ and G″ with composition show a trend similar to that of complex viscosity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4040–4044, 2006     

Preliminary investigation of poly(ether sulfone)/poly(aryl ether ketone) containing 1,4‐naphthalene blends

The blends of poly(ether sulfone) and poly(aryl ether ketone) containing 1,4‐naphthalene were prepared by melt mixing in a Brabender‐like apparatus. The specimens for measurements were made by compression molding under pressure and then were water‐quenched at room temperature. The tensile strength, tensile modulus, elongation at break, thermal analysis, and scanning electron microscopy were each measured. The dependence of tensile strength, tensile modulus, and elongation at break on blend systems was obtained. The effects of composition and miscibility on the mechanical properties are discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 472–476, 2006     

Processability and mechanical performance of hybrid composites based on poly(ether sulfone) modified with a glass fiber–reinforced liquid crystalline polymer

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     

Enhanced fracture toughness of epoxy resins with novel amine‐terminated poly(arylene ether sulfone)–carboxylic‐terminated butadiene‐acrylonitrile–poly(arylene ether sulfone) triblock copolymers

Amine‐terminated poly(arylene ether sulfone)–carboxylic‐terminated butadiene‐acrylonitrile–poly(arylene ether sulfone) (PES‐CTBN‐PES) triblock copolymers with controlled molecular weights of 15,000 (15K) or 20,000 (20K) g/mol were synthesized from amine‐terminated PES oligomer and commercial CTBN rubber (CTBN 1300x13). The copolymers were utilized to modify a diglycidyl ether of bisphenol A epoxy resin by varying the loading from 5 to 40 wt %. The epoxy resins were cured with 4,4′‐diaminodiphenylsulfone and subjected to tests for thermal properties, plane strain fracture toughness (K_IC), flexural properties, and solvent resistance measurements. The fracture surfaces were analyzed with SEM to elucidate the toughening mechanism. The properties of copolymer‐toughened epoxy resins were compared to those of samples modified by PES/CTBN blends, PES oligomer, or CTBN. The PES‐CTBN‐PES copolymer (20K) showed a K_IC of 2.33 MPa m^0.5 at 40 wt % loading while maintaining good flexural properties and chemical resistance. However, the epoxy resin modified with a CTBN/8K PES blend (2:1) exhibited lower K_IC (1.82 MPa m^0.5), lower flexural properties, and poorer thermal properties and solvent resistance compared to the 20K PES‐CTBN‐PES copolymer‐toughened samples. The high fracture toughness with the PES‐CTBN‐PES copolymer is believed to be due to the ductile fracture of the continuous PES‐rich phases, as well as the cavitation of the rubber‐rich phases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1556–1565, 2002; DOI 10.1002/app.10390     

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