Polymaths of Islam analyzes the social and intellectual power of religious leaders who created a shared culture that integrated Central Asia, Iran, and India from the mid-eighteenth century through ...the early twentieth. James Pickett demonstrates that Islamic scholars were simultaneously mystics and administrators, judges and occultists, physicians and poets. This integrated understanding of the world of Islamic scholarship unlocks a different way of thinking about transregional exchange networks. Pickett reveals a Persian-language cultural sphere that transcended state boundaries and integrated a spectacularly vibrant Eurasia that is invisible from published sources alone. Through a high cultural complex that he terms the "Persian cosmopolis" or "Persianate sphere, " Pickett argues that an intersection of diverse disciplines shaped geographical trajectories across and between political states. In Polymaths of Islam he paints a comprehensive, colorful, and often contradictory portrait of mosque and state in the age of empire.
Polymaths of Islam analyzes the social and intellectual
power of religious leaders who created a shared culture that
integrated Central Asia, Iran, and India from the mid-eighteenth
century through ...the early twentieth.
James Pickett demonstrates that Islamic scholars were
simultaneously mystics and administrators, judges and occultists,
physicians and poets. This integrated understanding of the world of
Islamic scholarship unlocks a different way of thinking about
transregional exchange networks. Pickett reveals a Persian-language
cultural sphere that transcended state boundaries and integrated a
spectacularly vibrant Eurasia that is invisible from published
sources alone.
Through a high cultural complex that he terms the "Persian
cosmopolis" or "Persianate sphere," Pickett argues that an
intersection of diverse disciplines shaped geographical
trajectories across and between political states. In Polymaths
of Islam he paints a comprehensive, colorful, and often
contradictory portrait of mosque and state in the age of
empire.
A series of 31 aromatic engineering thermoplastic formulations was exposed at outdoor sites in Florida, Arizona, and the Kingdom of Saudi Arabia (KSA) for 24 months as well as under modified ISO ...4892-2 xenon arc accelerated weathering conditions. The series included black, white, and transparent formulations. Measured properties were color, gloss, haze, transmission, tensile strength and elongation, Charpy impact, and erosion. There was surprisingly little difference in weathering among the outdoor sites except for the effects of blowing sand and slower erosion at the KSA site. Xenon arc accelerated weathering run at high irradiance and using state of the art filters provided very good predictions of color shifts, transmission, Charpy impact mode (break/no break), and tensile elongation at break. Prediction of gloss loss was only fair, especially for black samples, and haze was poorly predicted on the transparent samples. This suggests the need for better simulating the effects of rain and wind in accelerated weathering cabinets. Tensile strength and Charpy impact strength generally exhibited little change and were not useful properties to differentiate material performance.
•A series of engineering thermoplastics was subjected to xenon arc accelerated weathering and outdoors at three sites.•Accelerated conditions were ISO 4892-2 modified using Atlas Right Light™ filters and higher irradiance.•Accelerated conditions gave good predictions of color shifts, erosion rates, elongation at break, and Charpy impact mode.•The accelerated conditions gave poorer predictions of gloss loss and haze.•The results suggest the need for better reproduction of the effects of rain and wind on weathered surfaces.
Key points
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The hydrolytic stability of polycarbonate (PC), poly(ethylene terephthalate) (PET), and resorcinol polyarylate (RPA) films was studied at 65–95 °C and 23–95% relative humidity (RH) by measuring the ...time to embrittlement as measured by a bending test on films. The data show that the hydrolysis of these polymers is second order in RH with overall kinetics 1/tfail = A exp(-Ea/RT) RH2 where tfail is the embrittlement time in days, R is the gas constant, T is the temperature in kelvins, and RH is the fractional relative humidity. The activation energy, Ea, in kJ/mol and ln(A), respectively, for the polymers were PC: 92, 24.9; PET: 129, 39.3; RPA: 102, 30.0.
Samples of polycarbonate (PC), poly(butylene terephthalate) (PBT), a PC/PBT blend, and poly(styrene-co-acrylonitrile) (SAN), all containing 3% TiO2 (by mass), were exposed in the NIST (National ...Institutes of Standards and Technology) SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) to determine the effects of UV intensity (irradiance), temperature, relative humidity (RH), and UV wavelength on yellowing and gloss loss. There was no effect of irradiance, such that the samples obeyed reciprocity and doubling the irradiance doubled the rate of degradation. The activation energy for yellowing was determined to be ≈ 20 kJ/mol for PC, PC/PBT, and SAN and ≈16 kJ/mol for PBT. The activation energy for gloss loss was determined to be 9–16 kJ/mol. Thus, a 10 °C increase in temperature results in a 20%–30% increase in degradation rate. There was no consistent effect of RH on PC or PC/PBT yellowing or gloss loss. SAN degraded rapidly under dry conditions but showed little effect for RH > 10%. PBT lost gloss more slowly under dry conditions but displayed no RH effect with yellowing. Shorter wavelength UV had a greater effect on PC/PBT compared to PC or PBT.
•Weathering acceleration parameters were determined using the NIST SPHERE.•PC, PBT, a PC/PBT blend, and SAN generally exhibited reciprocity.•Activation energies determined from yellowing data were in the range of 16–21 kJ/mol.•Little effect from humidity was observed with RH > 10%.
The photodegradation of BPA polycarbonate (PC) can be described as an autoaccelerating process initiated by the formation of biphenol products arising from a formal photo-Fries reaction pathway. ...Evidence comes from spiking PC films with model compounds of photo-Fries reaction products, pre-exposure of films to generate photo-Fries products, and kinetic analysis. Published data on products formed during natural PC weathering are consistent with this pathway.
•Average annual solar spectral energy distributions (SEDs) were calculated based on multi-year spectrophotometric data.•Measured data could be fit using spectra calculated using SMARTS 2.9.5 to give ...the solar SEDs from 280 to 4000 nm.•SEDs were calculated for Miami, Florida; Phoenix, Arizona; Edgewater, Maryland; Madison, Wisconsin; and Regina, Saskatchewan.•Good agreement was found between independently-obtained datasets and between calculated and measured average broadband radiant energy for the sites.
Predicting outdoor service life of polymers and coatings requires knowledge of the spectral power distribution (SPD) of the sunlight and the amount of radiant energy they receive. Standard solar SPDs such as ASTM G173 and ASTM G177 are snapshots of the SPD at a single moment under model conditions. A better measure would be average annual spectral energy distributions (SED) for specific locations, especially benchmark outdoor weathering sites. The annual SED is the energy received at each wavelength over the course of a year. A Smithsonian/NIST collaboration placed SR-18 UV spectroradiometers in Miami, FL, Phoenix, AZ, and Madison, WI during the period 1997-2012, collecting data at ca. 2 nm intervals between 290 and 324 nm. Similar data have been collected at Edgewater, MD for many years. The data are not complete for any year, but gaps could be patched using data from other years. These data sets were compared to data available on-line from ongoing U.S Department of Agriculture (USDA)/Colorado State University outdoor spectroradiometer measurements, after similar patching. The USDA data have fewer points in the UV but extend into the visible portion of the spectrum. The data sets give consistent results and show that the SEDs can be fit by SPDs calculated using the SMARTS 2.9.5 model and satellite ozone data. The annual standard deviations are < 5% for wavelengths > 310 nm. SEDs for average annual radiant energy received by horizontal and 45° south exposures are reported for benchmark sites near Miami and Phoenix. The paper provides a general approach for determining an SED for a location based on SMARTS modeling of the autumnal equinox and subsequent scaling based on reported annual total solar radiant energy.
•Weathering acceleration parameters were determined using the NIST SPHERE.•Polycarbonate copolymers and resorcinol polyarylate (RPA) exhibited reciprocity while ABS did not.•ABS had a higher ...activation energy (Ea) for yellowing than other aromatic polymers while RPA had a small negative Ea.•ABS and RPA had higher rates of photodegradation when the relative humidity was ≤ 10%.
Understanding the responses of materials to environmental variables is essential for performing meaningful accelerated weathering and service life prediction. Samples of polycarbonate-b-resorcinol polyarylate copolymer (RPA), poly(acrylonitrile-co-butadiene-co-styrene) (ABS), and two polycarbonate copolymers with silicone or aliphatic diacids were exposed in the NIST (National Institute of Standards and Technology) SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) to determine the effects of ultraviolet intensity (UV irradiance), temperature, relative humidity (RH), and UV wavelength on yellowing and gloss loss and were compared to other aromatic polymers. All showed proportional response to irradiance (i.e., reciprocity) except ABS, which deviated notably at elevated temperatures. The activation energy for ABS yellowing was higher than other aromatic polymers (31 kJ mol−1 ± 2 kJ mol−1) while RPA had a slightly negative activation energy (-5 kJ mol−1 ± 3 kJ mol−1), reflecting differences in their photodegradation mechanisms. These two polymers also exhibited faster degradation when the RH was ≤ 10 % compared to ≥ 50 % RH. Wavelength effects varied among the polymers. The results indicate that predictive accelerated weathering should be performed with UV sources that accurately reproduce sunlight, at temperatures as close as possible to use conditions, and with RH > 10 %.
Acceleration parameters have been determined for bisphenol A polycarbonate (PC) exposed to blue light emitting diodes (LED) in a commercial apparatus for testing optical components using absorbance ...at 360 nm as a proxy for yellowing. The effect of temperature in the range of 90–120 °C gave linear Arrhenius plots with activation energies of 30–48 kJ/mol, depending on the presence of stabilizers. Experiments at irradiances of 5–75 kW/m2 showed good reciprocity with the rate of degradation extrapolating to zero at zero irradiance. Parallel experiments using xenon arc irradiation with UV filters showed that the yellowing was proportional to the sample thickness up to at least 6 mm. The activation energies and thickness dependence are much different from the findings for PC outdoor weathering. Examples are shown for making service life predictions using these acceleration parameters.
•Polycarbonate exposed to blue LED light undergoes yellowing.•The activation energy is 30–48 kJ/mol, depending on stabilization.•The yellowing obeys reciprocity and shows no thermal component to the yellowing.•The yellowing goes through the thickness of the part up to at least 6 mm.
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