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Houston, TX, United States

Laux K.A.,Texas A&M University | Sue H.J.,Texas A&M University | Bremner T.,Hoerbiger Corporation of America
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2014

Fretting is said to occur when mutually loaded contacts move relative to one another with nominally small displacements. The resulting stick slip between asperities causes cracks to nucleate at the surface and may eventually lead to catastrophic part failure. Furthermore, prediction of how a material might respond to such a scenario is challenging due the overall complexity of the process. The polyaryletherketone (PAEK) family of thermoplastics has been increasingly used in such fretting environments, but few studies exist regarding their fretting behavior. In this study, a custom built multi-axis tribometer has been shown to replicate fretting of PAEK in a pin on flat configuration. The experimentation and analysis has provided new insights into this phenomenon. Copyright © (2014) by the Society of Plastics Engineers All rights reserved. Source

White K.L.,Texas A&M University | Jin L.,Texas A&M University | Ferrer N.,University of Massachusetts Amherst | Wong M.,Texas A&M University | And 2 more authors.
Polymer Engineering and Science | Year: 2013

The mechanical properties and thermal stability of several grades of poly(aryletherketone)s (PAEKs) were investigated using thermal, rheological, and dynamic mechanical characterization. Detailed rheological characterization revealed that several grades of poly(etheretherketone) (PEEK) exhibit relaxation behavior characteristic of a long-chain branched structure. The potentially branched PEEKs showed greater mechanical damping behavior than the linear-chain PEEKs. The molecular weight dependence on zero-shear viscosity for several linear-chain polymers indicates that the PEEKs behave as rigid chains in the melt. Differences in chain structure do not significantly influence dynamic mechanical behavior in the solid state but affect stability at elevated temperatures. The potentially branched PEEKs are most susceptible to oxidation in air, but exhibit much greater stability in nitrogen. Poly(etherketone) is highly susceptible to degradation in both air and nitrogen environments. Implications of this study for development of high-performance PAEKs are discussed. © 2012 Society of Plastics Engineers. Source

Jin L.,Texas A&M University | Ball J.,Texas A&M University | Bremner T.,Hoerbiger Corporation of America | Sue H.-J.,Texas A&M University
Polymer (United Kingdom) | Year: 2014

The crystal structure and morphology of poly(ether ether ketone) (PEEK) was investigated using standard differential scanning calorimetry (DSC), flash DSC, optical microscopy, atomic force microscopy, and small angle X-ray scattering tools. The flash DSC results suggested that the double melting peaks phenomenon observed in conventional DSC work originated from the reorganization of PEEK crystals, which was due to the much faster recrystallization rate of PEEK than the DSC heating and cooling rate. A refined crystallization model to describe PEEK crystal structure formation was proposed. The refined crystallization model could help reconcile the discrepancy found between the bulk crystallinity measured by DSC and the linear crystallinity obtained from SAXS experiments by taking into account possible variation in crystal perfection within the lamellar structure. Simplified molecular dynamic modeling was carried out to support this model. Implications of the above findings to the fundamental understanding of structure-property relationships in PEEK were discussed. © 2014 Elsevier Ltd. All rights reserved. Source

Pope J.C.,Texas A&M University | Sue H.-J.,Texas A&M University | Bremner T.,Texas A&M University | Bremner T.,Hoerbiger Corporation of America | Blumel J.,Texas A&M University
Journal of Applied Polymer Science | Year: 2015

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. © 2014 Wiley Periodicals, Inc. Source

Guenther J.,Texas A&M University | Wong M.,Texas A&M University | Sue H.-J.,Texas A&M University | Bremner T.,Texas A&M University | And 2 more authors.
Journal of Applied Polymer Science | Year: 2013

Blends of polyaryletherketones (PAEK) with polybenzimidazole (PBI) are of commercial interest due to their improved upper service temperatures and wear properties when compared with the PAEK analogs examined to date. The retention of properties of the PBI component generally thought to be disadvantageous in more thermally or chemically aggressive environments is not well understood, nor are the specifics of interactions between the PBI and PAEK components in a melt or dry blend systems. In this initial investigation, focus is placed on the behavior and mechanism of polyetherketoneketone (PEKK)/PBI systems in contact with steam or condensed phase water. The goal is to understand the chemistry of the reaction, if any, upon exposure to steam as well as to examine the reversibility of moisture uptake of this material when exposed to liquid water or saturated steam. In this contribution, the pure polymer components and the PEKK-PBI (60: 40 wt %) blend are steam-treated at 149°C (300°F) and 316°C (600°F). IR and solid-state NMR spectroscopy are used to study chemical or morphological transformations of the polymers. All changes detectable by 13C cross-polarization with magic angle spinning (CP/MAS) upon steam-treatment are reversible, and not of a chemical nature, indicating that under the conditions of exposure used here no detectable chemical degradation occurs during steam exposure and with moisture uptake. The temporary water uptake of the samples, as studied by 1H wideline NMR and 13C T1 time measurements, leads to a change in the ratio of rigid versus mobile domains of the materials. © 2012 Wiley Periodicals, Inc. Source

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