Xenon Arc Radiation Research Articles

Influence of Laboratory Ageing on the Preservation of Anti-graffiti Properties for Paint Systems Used in Rolling Stock

The article describes and presents the influence of selected ageing mechanisms of paint systems currently used in railways in Poland in the context of maintaining their original protective properties against graffiti. Six paint systems with different types of finish, which had anti-graffiti properties, were tested, and the characteristics of the surface of the paint system, such as gloss and colour, were determined after a series of painting and cleaning of graffiti (markers and sprays). The tested objects were subjected to artificial simulated ageing using laboratory solar radiation in a synergistic combination of temperature and humidity in accordance with PN-EN ISO 16474-2 and in accordance with the proprietary methodology described in DN 001/08/A2/16 section 4.1.8 using the UV-C radiation source (discrete spectrum). The tested samples were also subjected to a different type of ageing mechanism under strong corrosive conditions in the form of neutral salt spray according to the methodology described in PN-EN ISO 9227. Keywords: ageing tests, xenon-arc radiation, UV-C radiation, neutral salt spray, paint systems, xenotest, gloss, colour, anti-graffiti protection, rolling stock

Mold Resistance of Nano and Micronized Particles-Treated Wood After Artificial Weathering Process

Wood and wood based materials under outdoor conditions may lose their appearance and performance properties by time. Color differences, cracks, rough surface may occur within a few years in unprotected wood. These undesired formations could be avoided by technical applications such as coatings on wooden surfaces by paints and varnish since such coating materials include special additives in their formulations such as UV absorbents, pigments, etc. Novel systems with nano or micronized particles may have superior properties when compared to conventional wood preservatives. In this study, we compared nano-scale, micro-scale and common wood preservatives in treated wood in terms of their effectiveness against mold fungi before and after artificial weathering process. Accelerated weathering tests of the test specimens were performed in a Xenon arc radiation cabinet with water spraying property. Artificially weathered and treated wood specimens were evaluated for resistance to mold fungi according to the ASTM D4445. General mold score results collected before and after artificial weathering process showed that CCA and MCQ-treated specimens had the best performance properties; however, nano zinc oxide-treated wood specimens had the weakest performance against mold fungi.

Acceleration parameters for polycarbonate under blue LED photo-thermal aging conditions

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.

Photodegradation of Polypropylene/ZnO Nanocomposites Films Prepared by Cryomilling under Xenon-arc Radiation

ABSTRACTThe photodegradation of polypropylene (PP)/ZnO composites at different concentrations was evaluated under solar simulated exposure of respective nanocomposite films. Nanocomposites were prepared by solid mixing using a cryogenic mill, and then films were prepared by compression molding. All films showed a good dispersion of ZnO nanoparticles without affect considerably the optical properties of the films. The films were exposed in a solar simulation chamber under three xenon arc lamps with a 340nm filter. Degradation of PP/ZnO nanocomposite films was monitored by formation of oxidative groups and changes on surface microstructure. FTIR results showed that oxidation groups in nanocomposites films increased by using cuasi-spherical ZnO nanoparticles.

Degradation behavior of ultra-high molecular weight polyethylene fibers under artificial accelerated weathering

This work aims to study the aging behavior of ultra-high molecular weight polyethylene (UHMWPE) fibers under xenon arc radiation. The correlation between structure and properties was analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and small angle X-ray scattering (SAXS). Both physical and chemical aging were observed. Carbonyl compounds were generated from the chain scission after radiation. The carbonyl index linearly increased with aging time. Both DMTA and DSC revealed that the crystal defects emerged after aging. Synchrotron SAXS was employed to characterize such structure. A model based on the information derived from SAXS is proposed. The results indicate that tensile strength is strongly affected by defects.

Weathering Evaluation of Structural Silicone Sealants Used in Korea

Abstract Super-tall buildings of over 100 stories are coming to Korea. To prove its economic prosperity, which was developed over the last 50 years after the Korean War, Korea is willing to have super-tall buildings as a symbol of its success. Locally, structural silicone glazing has become very common to achieve aesthetically pleasing and high utilization of small land for both residential and commercial building. Because there has been no industry-wide guideline or specification for structural silicone sealants in Korea, it is worthwhile to look at the performance of locally available structural silicone sealants. In this paper, several weathering techniques were adapted from various global industry standards. Artificial weathering using filtered xenon arc radiation was applied to specimens prepared in accordance with ASTM C1135. Comparative evaluations for temperature variations and salt spraying exposure were conducted as well. Silicones in general are known to have excellent resistance to such exposure. However, since the weathering performance of a sealant can be affected by its overall composition (not just the polymer type), some silicone products showed noticeable changes in our testing when compared to their initial properties.

Effect of xenon arc irradiation on optical whitened polyester woven fabrics

In this study, the CIE whiteness (CIE WI) and whiteness tint (Tw) of optically whitened (OWA) woven (plain and twill) polyester fabrics irradiated with xenon arc light were investigated. The fabrics were whitened in four concentrations using nine different commercial optical whitening agents, and were irradiated with xenon arc light under specific conditions between 0 and 100 h at 10-h intervals. The reflectance of the OWA fabrics was measured by using spectrophotometer, whereas the CIE WI and Tw values were calculated by using computer software. The results were investigated by statistical methods using analysis of variance and regression curves in which of the CIE WI of OWA polyester fabrics was found to decrease, while the Tw was also affected depending on irradiation time from the xenon arc light. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2013

Thermal decomposition behavior and durability evaluation of thermotropic liquid crystalline polymers

The thermal decomposition behavior and degradation characteristics of four different thermotropic liquid crystalline polymers (TLCPs) were studied. The thermal decomposition behavior was determined by means of thermogravimetric analysis (TGA) at different heating rates in nitrogen and air. The order of the thermal stability was as follows: multi-aromatic polyester > hydroxybenzoic acid (HBA)/hydroxynaphthoic acid (HNA) copolyester > HNA/hydroxyl acetaniline (HAA)/terephthalic acid (TA) copolyester > HBA/Poly(ethylene terephthalate) (PET) copolyester. The activation energies of the thermal degradation were calculated by four multiple heating rate methods: Flynn-Wall, Friedman, Kissinger, and Kim-Park. The Flynn-Wall and Kim-Park methods were the most suitable methods to calculate the activation energy. Samples were exposed to an accelerated degradation test (ADT), under fixed conditions of heat (63±3 °C), humidity (30±4%) and Xenon arc radiation (1.10 W/m2), and the changes in surface morphology and color difference with time were determined. The TLCPs decomposed, discolored and cracked upon exposure to ultraviolet radiation.

Influence of photostabilizers on wood flour–HDPE composites exposed to xenon-arc radiation with and without water spray

The weathering of wood–plastic composites changes their appearance and/or mechanical properties. These changes can be slowed through the addition of ultraviolet absorbers and pigments. The first phase of this study examined the effect of incorporating different concentrations of an ultraviolet absorber and/or pigment into wood-flour-filled high-density polyethylene (WF/HDPE) composites. Lightness and flexural properties of the composites were determined periodically during exposure to UV radiation and water spray in a xenon-arc type weathering apparatus. The influence of exposure type (UV radiation, with or without water spray) on the properties of photostabilized WF/HDPE composites was determined in the second phase of the study. The results showed that both ultraviolet absorbers and pigments provide protection against weathering of wood–plastic composites. The amount of protection can be influenced by both photostabilzer concentration and exposure variables.

Effect of weathering cycle and manufacturing method on performance of wood flour and high‐density polyethylene composites

AbstractWood–plastic lumber is promoted as a low‐maintenance high‐durability product. When exposed to accelerated weathering, however, wood–plastic composites may experience a color change and loss in mechanical properties. Differences in weathering cycle and composite surface characteristics can affect the rate and amount of change caused by weathering. In this study, 50% wood flour filled high‐density polyethylene composite samples were injection molded, extruded, or extruded and then planed to remove the manufacturing surface characteristics. Composites were exposed to two accelerated weathering cycles in a xenon arc weathering apparatus. This apparatus exposed the samples to xenon arc radiation, which is a combination of UV, visible, and IR radiation that is similar to solar radiation. Composites were exposed to radiation with or without water spray. After exposure to radiation and water spray, composites with more wood component at the surface (i.e., planed samples) experienced a larger percentage of total loss in flexural modulus of elasticity and strength after weathering compared with the other composites. Composites exposed to radiation only did not experience as much change in properties as those exposed to radiation with water spray. The results of this study demonstrate that exposing wood–plastic composites to water spray in combination with radiation is more severe than exposing wood–plastic composites to radiation only. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3131–3140, 2006

Attenuated total reflection infrared spectroscopy for micro-domain analysis of polyethylene samples after accelerated ageing within weathering chambers

Elucidation of the chemical changes that take place during the ageing of polyethylene by weathering can be accomplished by infrared (IR) spectroscopy. Accelerated ageing was applied to the most representative low density polyethylene (LDPE) found in markets today. The samples were exposed to UV- and xenon-arc radiation of varying duration and temperature cycles. The structural changes in the material surface were analysed by scanning electron microscopy (SEM) and chemical composition was studied by FTIR spectroscopy. By varying the crystal material in the conventional attenuated total reflection (ATR) experiments it was possible to analyse distinct layers from the surface. Micro-domain analysis was made possible by using a novel ATR microprobe based on a silver halide fibre of circular cross-section with an outer diameter of 700 μm. Layers at larger depth were reached by cross-sectioning the LDPE-samples and measuring the concentration profiles of oxidation products down to 500 μm with a spatial resolution lesser than 15 μm. The main chemical modifications were from carbonyl formation of various kinds identifiable in the ATR–FTIR spectra of degraded polyethylene samples.

Degradation profile of polyethylene after artificial accelerated weathering

Elucidation of the chemical changes that take place during the aging of polyethylene sheared electrical cables, and the correlation of these changes with physical properties need experiments with accelerated aging assays. These were carried out using the most representative polyethylene grades found in today's market: low density (LDPE), linear low density (LLDPE) and high density (HDPE). The samples were exposed to UV- and xenon arc radiation using a varying exposure time and different temperature cycles. The changes in the material structure and properties were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), FTIR-spectroscopy, density and hardness measurements. During degradation polar groups in the polyethylene are generated, as well as chain scission and cross-linking. As net effects of these processes respective increases in crystallinity, density and hardness and surface cracking at late stages of degradation are observed. By varying the angle of incidence in attenuated total reflection (ATR) experiments using FTIR-spectroscopy it was possible to detect variations in composition of distinct layers from the surface down to a depth of 1.2 μm. Deeper layers were reached by microtoming the samples in layers down to 60 μm. The main chemical modifications were carbonyl formation of various kinds which were identified in the FTIR–ATR spectra of degraded polyethylene samples.

Testing accelerated weathering tests for appropriate weathering chemistry: Ozone filtered xenon arc

Ftir spectroscopy has been used to follow the weathering chemistry of a HALS and UVA free polyester/urethane and a HALS and UVA free acrylic/melamine clearcoat cured on silicon wafers and subjected to exposure in Florida, Arizona, and in a number of accelerated weathering tests. All accelerated tests except EMMAQUA-NTW, ozone filtered xenon arc, and 3M Proprietary exposures distort the polyester/urethane’s weathering chemistry relative to its Florida and Arizona exposure weathering chemistry. Distorted weathering chemistry was attributed primarily to spectral power distribution mismatch between artificial radiation and sunlight. Experiments were initiated with an ozone filtered xenon arc radiation source whose spectral power distribution matches sunlight with great fidelity in the 290–400 nm region.

The Properties and Light Stability of Silk Adhered to Sheer Silk and Polyester Support Fabrics with Poly(Vinyl Acetate) Copolymer Adhesives

Adhesil1e support treatments for the conservation of silk artifacts were evaluated by comparing the properlies and relative light stability of silk laminates and their components. Samples were prepared by adhering silk habutae, representing the artifact, to a silk or polyester crepeline support fabric with either Appretan MB extra or Lascaux Hot-seal Adhesive 371. both poly(vinyl acetate) copolymer adhesives. Laminates and unlaminated components were exposed to xenon arc radiation and subsequently characterized by measuring colour change. stiffness. and tensile properties. The laminates were stronger. stiffer and sometimes of a different colour than plain silk hahutae. The laminates yellowed and exhibited losses in tensile properties when exposed to light, in a manner similar to that of plain silk habutae. The loss of tensile properties and yellowing of the support materials upon exposure to light were at least retarded when covered by the habutae in the laminates. Much less flexible than their components to begin with. the laminates also stiffened more rapidly than their components when exposed to light.

Use of stable tracer studies to evaluate pesticide photolysis at elevated temperatures.

New methods were developed to determine photolysis rates of medium-weight pesticides in the gas phase using elevated air temperatures and solid-phase microextraction (SPME). A 57-L glass chamber was constructed that utilized collimated xenon arc irradiation that could heat chamber air to increase the amount of pesticide in the gas phase. Gas-phase photolysis rates were determined at various air temperatures by comparing the rate of loss of each of the tested pesticides to a photochemically stable tracer, hexachlorobenzene. Interval sampling of gas-phase constituents was performed using SPME immediately followed by GC-ECD or GC-MSD analysis. The two pesticides under examination were the dinitroaniline herbicide trifluralin and the organophosphorus insecticide chlorpyrifos. The gas-phase photolysis for trifluralin was found to be rapid with half-lives of 22-24 min corrected for sunlight. These results were comparable to photochemical lifetime estimates from other investigators under sunlight conditions. Elevating temperatures from 60 to 80 degrees C did not affect photolysis rates, and these rates could be extrapolated to environmental temperatures. From 60 to 80 degrees C, gas-phase chlorpyrifos photolysis lifetimes were observed to range from 1.4 to 2.2 h corrected for sunlight and will thus be important together with hydroxyl radical reactions for removing this substance from the atmosphere. At these elevated temperatures, pesticides and tracer compounds were found to be substantially in the gas phase, and possible effects on reaction rates from wall interactions were minimized.

Reactivity of certain organophosphorus insecticides toward hydroxyl radicals at elevated air temperatures.

Methods were developed to determine OH reaction rates for medium-weight organophosphorus pesticides in the gas phase. A 57-L chamber was constructed that utilized xenon arc irradiation (>290 nm) to photolyze the OH precursor, methyl nitrite. Experiments were performed at elevated temperatures ranging from 60 to 80 degrees C to minimize wall sorption. Solid-phase microextraction (SPME) sampling of the gas phase was employed to assess the simultaneous rate of loss of the pesticides in relation to the rate of loss of two reference substances with known OH rate constants. An internal gas-phase standard (hexachlorobenzene), relatively stable to hydroxyl radicals, was used to assess other processes, which included dilution and wall sorption. The relative reaction rates of the organophosphorus insecticides, diazinon and chlorpyrifos, when compared to reference compounds, were unaffected by various air temperatures between 60 and 80 degrees C. Although both insecticides were expected to react at similar rates on the basis of structural activity model predictions, diazinon reacted 3 times more rapidly than chlorpyrifos and gave estimated environmental OH half-lives of 0.5 and 1.4 h, respectively. The degree of sorption onto the chamber walls was minimal and similar for each of the compounds examined. Experimental gas-phase determinations at elevated temperatures may provide important information that can be used when in the assessment of the potential of airborne pesticide risks to nontarget and ecologically sensitive areas.

Evaluation of the Deterioration in Mink Hair under Xenon Arc Irradiation by Mechanical Measurement and Morphological Observation.

To evaluate the light deterioration in sapphire mink guard hair, the irradiated hair was examined by the mechanical measurement and surface observation. A deterioration of hair by irradiation indicating the mobility increase can be detected as an increase in tan δ in a temperature region from 150°C to 220°C by the dynamic viscoelasticity measurement. The observation by scanning electron microscope (SEM) revealed that light deterioration in mink hair can be evaluated as adhesion of particles, melted scale structure of tip portion, cracks running in the axial direction by inflection, or transverse cracks at tensile break.

Effect of Xenon Arc Irradiation on Mink Hair Protein Extracted with Thioglycolate

The effect of xenon arc irradiation on the extractability and properties of mink hair protein treated with sodium thioglycolate solution was investigated. Over 50% of the intact sapphire mink hair was dissolved when treated with TG 11 (0.1M sodium thioglycolate, pH 11) and TG/G-7 (0.1M sodium thioglycolate, 6M guanidine-HCI, pH 7), but hardly dissolved with TG/U-7 (0.1M sodium thioglycolate, 7M urea, pH 7). The extractability of underfur was higher than that of guard hair with TG 11 or TG/G-7. The extractability with TG 11 or TG/G-7 was remarkably decreased in intact hair than irradiated hair. This implies that the irradiation-induced deterioration of mink hair involves the formation of some additional intermolecular or interpeptide crosslinks other than the original disulfide bridges in native hair. Amino acid analysis, SDS-PAGE and size exclusion chromatography of TG/G-7 extract revealed that the irradiation of mink hair made preferentially microfibril protein insoluble, and leaves matrix protein especially high-glycine-tyrosine component soluble.

Wavelength sensitivity of photo-oxidation of polyamide 6

The wavelength sensitivity of polyamide 6 films exposed to filtered xenon arc radiation was studied by the sharp cut filter technique based on the changes in UV absorption. The spectral sensitivity curves and activation spectra were obtained. It was found that the photo-oxidation of PA6 can be caused by light in a wide wavelength range of about 260–480 nm. From the activation spectra it was shown that there exist two distinctly separate spectral regions responsible for causing PA photo-oxidation: wavelengths below 300 nm and in the range of 340–400 nm. The results are discussed from the point of view of the initiation mechanism of PA photo-oxidation..

Evaluation of the Deterioration in Mink Hair under Xenon Arc Irradiation by Fourier Transform Infrared(FTIR) Microspectroscopy.

The protein deterioration in mink hair under xenon arc irradiation was quantitatively evaluated by fourier transform infrared microspectroscopy (FTIR). Guard hairs of green skin of sapphire mink, tanned sapphire mink, green skin of dark mink and tanned dark mink were irradiated with a xenon lamp for 96 hours and subjected to FTIR analysis. Differential spectra taken in the wave number range of 1350_??_900cm-1 demonstrated that the absorption intensity at 1040cm-1 due to the -SO3- of the cysteic acid residues produced in irradiated hair was proportional to the irradiation time in the range of 12_??_96 hours. The relation between the both was expressed by a linear regression equation of y=ax (y: peak height or peak area of IR absorption, x: irradiation time, a: slope), the slope of the regression equation for dark mink was smaller than for sapphire mink, and so was for tanned skin than for green skin. The present method enables to evaluate the difference in the degree of deterioration among different and differrently processed mink hair samples.