Preparation and characterization of high permittivity and low loss PTFE/CaTiO3 microwave laminates

This article discusses the preparation and characterization of CaTiO₃ filled PTFE flexible laminates for microwave substrate applications. Single phase CaTiO₃ filler composition was prepared through solid‐state ceramic route. Phase formation was confirmed by powder X‐ray diffraction studies. Morphology and filler distribution of the composites were studied using scanning electron microscopic technique. Permittivity and loss tangent of the composite substrates were measured at X‐band frequency region (8.2–12.4 GHz) using waveguide cavity perturbation technique. Effective permittivity of the composites was compared with theoretically predicted values. Temperature coefficient of permittivity (τ_εr) of the composites was also measured in the 0–100°C temperature range. PTFE/CaTiO₃ composite has an effective permittivity of 11.8 and a loss tangent of 0.0036 at optimum filler loading. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Properties of melt processable PTFE/PEEK blends: The effect of reactive compatibilization using electron beam irradiated melt processable PTFE

For the first time, blends of melt processable polytetrafluoroethylene (MP PTFE) with polyetheretherketone (PEEK) in the MP PTFE/PEEK ratio of 100/0, 80/20, 50/50, 20/80, and 0/100 w/w were prepared and characterized. MP PTFE/PEEK blends are attractive materials due to the combination of low coefficient of friction and universal chemical resistance of MP PTFE with good wear resistance and mechanical strength of PEEK while maintaining high thermal stability of both. Miscibility, phase morphology, and mechanical properties of the new MP PTFE/PEEK blends were investigated. To improve their end‐use properties, an attempt of reactive compounding with the electron beam irradiated MP PTFE (e‐beam MP PTFE) was made. The reactive compounding was done in two steps, that is, the preparation of a masterbatch (MB) consisting of e‐beam MP PTFE/PEEK (50/50 w/w) and subsequent melt blending of MP PTFE/PEEK with varying concentrations of MB. The e‐beam irradiation of MP PTFE carried out in air atmosphere and at room temperature with a dose of 50 kGy results in its chain scission associated with formation of ? COF and ? COOH functional groups. Such modified MP PTFE can be used to compatibilize MP PTFE/PEEK blends. Reactive compatibilized blends exhibit improved phase morphology and mechanical properties. Especially for MP PTFE/PEEK 50/50 blends, a great improvement of almost 250% in strain at break, 40% in stress at break, and more than 600% in toughness was achieved. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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.     

Microwave Dielectric Properties of Rutile Filled PEEK Composites

Ceramic-filled PEEK composites were prepared by sigma mixing followed by thermolamination. Rutile-grade titanium dioxide, particle size less than 5 μm, was used as the particulate filler in the PEEK matrix to tailor the dielectric properties of the composite matrix. The dispersion of the particular filler in the PEEK matrix was studied using scanning electron microscopy. The dielectric properties of the PEEK/TiO₂ composite materials were measured in the low frequency region up to 13 MHz using an impedance analyzer. Dielectric properties in the microwave region were measured using cavity perturbation technique to evaluate the use of the composites as packaging material. Experimental results were compared with theoretically predicted values using the Lichtenecker equation. The present study shows that temperature-stable packaging materials can be realized in the PEEK/TiO₂ systems by judiciously controlling the ceramic filler concentration.     

Effect of blending on the multiple melting behavior of polyphenylene sulfide

The effects of melting time (t_melt) and annealing time (t_a) at a temperature closer to the melting point of polyphenylene sulfide (PPS) on the multiple melting behavior of neat PPS, and PPS component in their blends have been investigated by differential scanning calorimetry (DSC). It is found that double endotherm peak of PPS annealed at 275°C for less than three hours is different from that annealed for twelve hours. Double endotherm peak of PPS in PEEK/PPS blends shifts to lower temperature, and the intensity of the upper melting peak decreases significantly by addition of polyether ether ketone (PEEK). An additional third melting peak could be observed. The temperature of third melting peak is above 310°C and increases as the t_a and PEEK content are increased. For PEK-C/PPS blends, the lower and upper melting temperatures of the PPS component are higher than that of neat PPS annealed at 275°C for twenty-three hours. © 1996 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1001–1008, 1997     

Mechanical and Thermal Properties of Poly(phthalazinone biphenyl ether sulfone)/PEEK Blends

A series of blends with various compositions are prepared by melt extrusion on the basis of novel copoly(phthalazinone biphenyl ether sulfone) (PPBES) and poly(ether ether ketone) (PEEK). The melt flowability, mechanical and thermal properties of the blends are studied. The results show that the incorporated PEEK has a large influence on the melt viscosity and thermal stability of blends. The tensile strength of the blends remains at about 90 MPa at room temperature; PPBES improves the mechanical properties of PEEK at 150°C. The flexural strength and modulus of the PPBES/PEEK blends also increase with the addition of PEEK.     

Crystallization kinetics of a PEEK/LCP blend

The crystallization kinetics of a polyetheretherketone (PEEK)/liquid crystalline polymer (LCP) blend was studied by using differential scanning calorimetry. Nonisothermal runnings were performed on heating and on cooling at different rates. Isothermal crystallization experiments at 315, 312, 310, and 307°C, from the melt state (380°C) were performed in order to calculate the Avrami parameters n and k and the fold surface free energy, σ_e. Polarized light optical micrographs were also obtained to confirm the Avrami predictions. It was observed that the LCP retarded the PEEK crystallization process and that the PEEK melting temperature decreased with the amount of LCP, but the LCP melting temperature increased with the amount of PEEK. Probably the PEEK improves the perfection of the LCP crystalline domains. A spherulitic morphology in pure PEEK and its blends was predicted by the Avrami analysis; however this morphology was only observed for pure PEEK and for the 80/20 composition. The other compositions presented a droplet and fibrillar-like morphology. The overall crystallization rate was observed to decrease with the crystallization temperature for all compositions. Finally, σ_e was found to decrease with the increase of LCP in the blends, having unrealistic negative values. Thus, calculations were made assuming σ_e constant at all compositions. It was observed that δ, the interfacial lateral free energy, decreased but still remained positive. It was concluded that in these blends neither σ_e nor σ could be considered constant. © 1995 John Wiley & Sons, Inc.     

Crystallization kinetics of compatibilized blends of liquid crystalline polymer with PEEK

A fully aromatic thermotropic liquid crystalline polyester (TLCP) has been blended with poly(ether ether ketone) (PEEK). Multiblock copolymer (BCP) was used as the compatibilizer in the concentration at 2 phr. The isothermal crystallization kinetics and morphology of compatibilized blends were studied using differential scanning calorimetry (DSC) and polar light micrograph (PLM). TLCP acted as a heterogenous nucleation sites to accelerate the crystallization for PEEK. However, PEEK crystallization rates decreased with increasing TLCP fraction. Isothermal crystallization exotherms showed that the addition of BCP retarded crystallization of PEEK in PEEK/TLCP blend, which was probably resulted from the constraint effect of BCP as well as the size reduction of PEEK spherulite domain. The equilibrium melting temperature of PEEK for blends was below that of pure PEEK. After adding BCP, it decreased further. Morphological analysis showed that it was difficult to discern the single PEEK spherulites when BCP was added. POLYM. COMPOS., 27:642–650, 2006. © 2006 Society of Plastics Engineers     

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

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

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     

Effect of high-performance polymers on crystallization and multiple melting behavior of poly(phenylene sulfide)

The crystallization and multiple melting behavior of poly(phenylene sulfide) (PPS) and its blends with amorphous thermoplastic bisphenol A polysulfone (PSF) and phenolphthalein poly(ether ketone) (PEK-C), crystalline thermoplastic poly(ether ether ketone) (PEEK), and thermosetting bismaleimide (BMI) resin were investigated by a differential scanning calorimeter (DSC). The addition of PSF and PEK-C was found to have no influence on the crystallization temperature (T_c) and heat of crystallization (ΔH_c) of PPS. A significant increase in the value of T_c and the intensity of the T_c peak of PPS was observed and the crystallization of PPS can be accelerated in the presence of the PEEK component. An increase in the T_c of PPS can also be accelerated in the BMI/PPS blend, but was no more significant than that in the PEEK/PPS blend. The T_c of PPS in the PEEK/PPS blends is dependent on the maximum temperature of the heating scans and can be divided into three temperature regions. The addition of a second component has no influence on the formation of a multiple melting peak. The double melting peaks can also be observed when PPS and its blends are crystallized dynamically from the molten state. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 637–644, 1998     

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。     

Growth of Al2O3–PTFE composite film at room temperature by aerosol deposition method

To fabricate a ceramic-based substrate for 3-dimensional integration modules with a thick film coating process at room temperature, aerosol deposition method was employed. Al₂O₃ was chosen as a main coating material for the requirements of low permittivity and dielectric loss. Especially to give a functionality of plasticity, composite film with polytetrafluoroethylene (PTFE) was also studied. The effects of PTFE, which was incorporated in the film, were investigated by the microstructural characterization. It was confirmed that Al₂O₃–PTFE film with the grain size of 100–200 nm were grown at room temperature using Al₂O₃–0.5 wt% PTFE mixture powders. Dielectric constant and dielectric loss of Al₂O₃–PTFE film were 4.5 and 0.005 at 1 MHz, respectively.     

Kinetic analysis of thermo‐oxidative degradation of PEEK/thermotropic liquid crystalline polymer blends

The thermal degradation behavior of blends of poly(aryl ether ether ketone), PEEK, with a thermotropic liquid crystalline polymer (TLCP), Vectra®, were investigated in an oxidative atmosphere, using thermogravimetric analysis under dynamic conditions. The theoretical weight loss curves of the blends were compared with the experimental curves in order to explain the effect of blending on the thermal stability of the pure polymers. The thermo‐oxidative degradation of PEEK/Vectra® blends of different compositions takes place in various steps and the characteristic degradation temperatures and the kinetic parameters such as activation energy are strongly influenced by blending. Polymer blends based on this TLCP polymer had not been previously studied from kinetic viewpoint. POLYM. ENG. SCI. 46:129–138, 2006. © 2005 Society of Plastics Engineers     

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     

Molecular aggregation of PEEK with PES blends and the block copolymers composed of PEEK and PES components

Polymer blends of PEEK with PES were prepared by the solution blending method. Copolymers composed of PEEK and PES components were synthesized from these oligomers. The formation conditions exerted an influence over the molecular aggregation and the crystallization behaviors of the blend films and block copolymers which were examined by X-ray diffractometry and DSC analysis. As a result, phase-separation in the blend films was found when the formation temperature was high. The blend films formed at 340°C, quenched and annealed at 180°C, exhibited the same crystallization behavior as those of PEEK. In the case of the blend films formed at 300°C, the annealing of the films at 250°C was required to crystallize the blend films. The T_g of a copolymer with a PEEK component content of more than 50% tends to shift toward a higher temperature than the T_g of PEEK itself, and the T_m of the copolymer toward a lower temperature than that of PEEK ist.     

聚四氟乙烯填充聚醚醚酮及其复合材料的研究

利用熔融共混工艺制备了ＰＥＥＫ／ＰＴＦＥ共混物及其复合材料,研究了ＰＴＦＥ对ＰＥＥＫ共混物及其复合材料力学性能和耐磨性的影响,结果表明,ＰＥＥＫ经１０％￣ＰＴＦＥ填充改性,玻纤／碳纤混杂增强后,由于磨损方式的改变,使该复合材料不仅保持了良好的物理力学性能,而且具有较低的摩擦系数,耐磨性也得到明显改善。     

Nanocellular foams—cell structure difference between immiscible and miscible PEEK/PEI polymer blends

Plastic foam with a nanoscale cell structure was prepared from poly(ether ether ketone) (PEEK)/para‐diamine poly(ether imide) (p‐PEI) as well as PEEK/meta‐diamine poly(ether imide) (m‐PEI) blends by a temperature quench foaming method with CO₂. The difference in chemical configuration between m‐ and p‐PEI gave rise to a prominent change in the higher order blend morphology and cell structure of the respective foams. The bubble nucleation site and bubble size were controlled by templating the morphology of the PEEK/p‐PEI blend, which shows an immiscible and unique strip‐patterned crystalline morphology. The properties influenced by the immiscibility of the PEEK/p‐PEI blend were investigated using SEM, thermal analysis and rheology and compared with the properties of the miscible PEEK/m‐PEI blend. The bubble size and location were highly controlled in the PEI disperse domain that was aligned between the PEEK crystalline layers in the PEEK/p‐PEI blend. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

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     

Multinuclear solid‐state NMR investigation of the moisture distribution in PEEK‐PBI and PEKK‐PBI blends

Blends of polyaryletherketones (PAEK), such as polyetheretherketones (PEEK) and polyetherketoneketones (PEKK), with polybenzimidazole (PBI) are of commercial interest due to their improved high‐temperature stability and wear properties. The changes of PBI and its PEEK‐ and PEKK‐blends (50 : 50 wt %) after immersing them in liquid H₂O and D₂O, and exposing them to D₂O steam at elevated temperatures and pressures are investigated by multinuclear solid‐state NMR and IR spectroscopy. Macroscopic morphological and chemical changes on the molecular scale, which take place upon high‐temperature steam‐treatment and the extent and reversibility of moisture uptake have been investigated. Interactions and reactions of water, steam, and aqueous solutions of LiCl and ZnBr₂ with the functional groups of the polymer components have been studied using D₂O in combination with IR, ¹H wideline, ²H, ⁷Li, and ⁷⁹Br MAS, as well as ¹³C and ¹⁵N CP/MAS NMR spectroscopy. Different locations and types of water and protons in the blends have been described and PBI has been proven to be mainly responsible for water and salt uptake into the blends. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41421.