Glass transition and melting behavior of poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene) (PEEK)

Cheng, Stephen Z. D.; Cao, Min; Wunderlich, Bernhard

doi:10.1021/ma00161a015

Cited by 428 publications

(279 citation statements)

References 7 publications

(14 reference statements)

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“…This postulated model was primarily based on the observation that the magnitude and position of the low endotherm is heating rate dependent. The suitability of the model was questioned by the experimental findings that the occurrence of the high-melting endotherm precedes that of the lowtemperature endotherm, 36,38,47 which clearly contradicts the assignment of the low endotherm to the partial melting of the primary lamellae as postulated in this model.…”

Section: Introductionmentioning

confidence: 78%

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Supaphol

2001

J of Applied Polymer Sci

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ABSTRACT:The melting behavior of syndiotactic polypropylene (s-PP) after isothermal crystallization from the melt state was studied using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) techniques. Three melting endotherms were observed for isothermal crystallization at high degrees of undercooling. The minor endotherm, located closed to the corresponding crystallization temperature, was postulated to be the melting of the secondary crystallites formed at the crystallization temperature. The low-temperature melting peak was found to be the melting of the primary crystallites formed, and the high-temperature melting peak was a result of the melting of the crystallites recrystallized during a heating scan. The triple-melting behavior observed in subsequent melting endotherms of s-PP was therefore described as contributions from melting of the secondary crystallites and their recrystallization, partial melting of the less stable fraction of the primary crystallites and their recrystallization, melting of the primary crystallites, and remelting of the recrystallized crystallites formed during the heating scan. In addition, determination of the equilibrium melting temperature for this s-PP resin according to the linear and nonlinear Hoffman-Weeks extrapolations provided values of 143.1 and 185.6°C, respectively.

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Section: Introductionmentioning

confidence: 78%

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Supaphol

2001

J of Applied Polymer Sci

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“…The relatively narrow range of mechanical properties with respect to temperature and humidity is due to the PEEK reinforcement of the FAA-PEEK film that resists swelling and has no thermal transitions in this range. 38 The ATMPP film has a small response to temperature between 30…”

Section: Etfe-g-pvbtmamentioning

confidence: 99%

Mechanical Characterization of Anion Exchange Membranes by Extensional Rheology under Controlled Hydration

Vandiver

Caire

Carver

et al. 2014

J. Electrochem. Soc.

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Alkali anion exchange membrane (AEM) based devices have the potential for electrochemical energy conversion using inexpensive catalysts and a variety of fuel types. Membrane stability and anion transport must be improved in AEMs before these devices can be fully realized. Mechanical failure of the membrane can contribute to failure of the device, thus membrane durability is critical to overall system design. Here, a study of the mechanical properties of three well-established AEMs uses a modified extensional rheometer platform to simulate tensile testing using small membrane samples. Mechanical properties were tested at 30 and 60 • C under dry or water saturated gas conditions. Water in the membrane has a plasticizing effect, softening the membrane and reducing strength. PEEK membrane reinforcement limits swelling producing negligible softening and only a 9% decrease in strength from dry to hydrated conditions at 30 • C. Higher cation concentration increases water uptake resulting in significant softening, a 57% reduction in Young's modulus, and a 67% reduction in strength when hydrated at 30 • C. In a working electrochemical device, AEMs must maintain integrity over a range of temperatures and hydrations, making it critical to considering mechanical properties when designing new membranes. Polymer electrolyte membrane fuel cells and electrolyzers are potentially disruptive technologies that will replace traditional heat engines such as internal combustion engines for transportation applications, portable electronics, and are scalable to larger energy storage facilities. Polymer electrolyte membrane fuel cells are suitable for transportation applications due to their low temperature start-up and operation, high power density, and quick refueling.1-3 Proton exchange membranes (PEMs) have dominated polymer electrolyte membrane fuel cell development in the last several decades, resulting in the development of relatively stable, well performing membranes.1-4 Current PEM fuel cells remain cost prohibitive due to high catalysts costs, as well as long-term durability issues. 3,5,6 Anion exchange membranes (AEMs) can also be utilized in polymer electrolyte membrane devices and have several potential benefits over PEMs. AEM fuel cells benefit from increased kinetics in an alkali media allowing more complex fuels then hydrogen and have the potential to utilize non-platinum catalysts to reduce costs. 7-11However, a number of challenges must be overcome before AEMs reach the performance and durability necessary for fuel cells and other electrochemical energy conversion devices. Hydroxide present in the AEM degrades many of the proposed cationic groups and some polymer backbones, making development of chemically stable AEMs difficult. 9,11,12 Additionally, transport of hydroxide in AEMs is inherently slower than protons in PEMs, 13 to compensate, the concentration of ionic groups is often increased in AEMs.8 Increasing ion concentration in AEMs increases water sorption in the polymer and can result in significant dimensional...

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“…1(b), the low endotherm T m,1 obtained at~10 K above T c is usually attributed to an annealing effect (Cheng et al, 1986;Velikov & Marand, 1993). We also found that the low endotherm T m,1 not only shifts to a higher temperature with increase of the crystallization temperature, but also increases in magnitude with the annealing time.…”

Section: Identification Of Multiple Melting Peaksmentioning

confidence: 99%

“…The multiple melting behavior is usually explained by polydisperse lamellar thickness (dual lamellar thickness) (Cheng et al, 1986;Hsiao et al, 1993a, b), melting-recrystallization-remelting (Blundell & Osborn, 1983;Blundell, 1987) and polymorphic crystals (Sun & Woo, 1999;Ho et al, 2000;Gan et al, 2004;Ghosh et al, 2005). Both the dual lamellar thickness and melting-recrystallization-remelting can easily be confirmed by DSC measurements at different scan rates and different annealing treatments (time and/or temperature).…”

Section: Introductionmentioning

confidence: 98%

Melting behavior of polymorphic crystals of poly(trimethylene 2,6-naphthalate) studied by simultaneous synchrotron X-ray scattering and thermal analysis

et al. 2007

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The polymorphic crystallization and melting behavior of poly(trimethylene 2,6‐naphthalate) (PTN) have been investigated using small‐angle X‐ray scattering and simultaneous wide‐angle X‐ray scattering (WAXS) and differential scanning calorimetry (DSC). The α‐crystal, the β‐crystal and the coexistence of both crystal forms of PTN develop at an isothermal temperature below 393 K, above 453 K and between these two temperatures, respectively. The simultaneous WAXS/DSC measurement provides a good way to identify the origin of multiple melting peaks and to get equilibrium melting temperatures. During the PTN melting process, the thermal evolutions of crystallinities, Bragg diffraction intensities and DSC thermograms reveal that the phase transformation and primary and secondary crystallizations arise to generate the multiple melting peaks. The β‐crystal with high equilibrium melting temperature ( = 510 K) is a structurally stable phase while the α‐crystal with low equilibrium melting temperature ( = 488 K) is a metastable phase. The temperature‐dependent structural parameters such as the long period, lamellar thickness and amorphous thickness were extracted from the interface distribution function. Two‐step changes in the lamellar thickness and the invariant during the subsequent melting of PTN crystallized at 383 K are consistent with the transformation obtained by WAXS/DSC. The transformation, a typical melting–recrystallization, proceeds firstly via surface melting of α‐lamellae, and then the PTN chains near the boundaries of surviving α‐lamellae modify their conformation to form the β‐crystal resulting in thickening lamellae.

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Glass transition and melting behavior of poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene) (PEEK)

Cited by 428 publications

References 7 publications

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Mechanical Characterization of Anion Exchange Membranes by Extensional Rheology under Controlled Hydration

Melting behavior of polymorphic crystals of poly(trimethylene 2,6-naphthalate) studied by simultaneous synchrotron X-ray scattering and thermal analysis

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