scholarly journals Inhibition of Polyimide Photodegradation by Incorporation of Titanate Nanotubes into a Composite

2020 ◽  
Author(s):  
Christian Harito ◽  
Dmitry V Bavykin ◽  
Brian Yuliarto ◽  
Hermawan K Dipojono ◽  
Frank C Walsh
Keyword(s):  
Methylene Blue ◽  
Raman Spectroscopy ◽  
Brittle Material ◽  
Uv Light ◽  
Light Exposure ◽  
Polymer Chains ◽  
Plasticity Index ◽  
Uv Exposure ◽  
Spectroscopy Optical ◽  
Positively Charged

The effect of UV light exposure on the properties of hexafluoroisopropylidene-diphthalic anhydride–oxydianiline (6FDA–ODA) polyimide (PI) and polyimide–titanate nanotube (TiNT/PI) composites has been studied using Raman spectroscopy, optical microscopy, nanoidentation and TEM. The degree of polymer photodegradation was estimated by measuring the change in affinity to a positively charged dye (methylene blue, MB). The mechanism of photoassisted transformations in polyimides usually involves scission of polymer chains accompanied by appearance of active radicals, which undergo further rapid transformations to more stable phenol, amine, and carboxylic functional groups. The accumulation of these groups can increase the degree of adsorption of charged dyes in the photodegraded polymer. It was found that neat PI showed a significantly increased capacity to adsorb MB after irradiation with UV, reaching a plateau after 1 h. In contrast, TiNT/PI composite demonstrated a much slower rise in concentration of adsorbed MB even after 4 h of UV exposure. Raman spectra indicated cleavage of C=O and C–F bonds in PI while only the C–F bond was damaged in TiNT/PI. Shorter cracks (≈ 40 µm long) appeared in TiNT/PI composites whereas macro cracks (> 100 µm) were visible in neat PI after 3 h of UV exposure. Brittleness was studied by comparing plasticity index which varied from 0 to 1 (0 corresponding to the most brittle material and 1 the most ductile one). Plasticity index reduced by 51% and 2% for PI and TiNT/PI, respectively after 3 h UV irradiation, indicating that TiNT can protect underlying PI from further damage. The hardness of neat PI decreased whereas, for TiNT/PI, it increased under UV, suggesting crosslinking of broken polymer chains with nanotubes.

Strength Properties of Flexible Geogrids Under Indoor and Outdoor Ultraviolet Exposure

2003 ◽  
Vol 1849 (1) ◽  
pp. 221-230 ◽  
Author(s):  
Chiwan Wayne Hsieh ◽  
Chien Kuei Lin
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Carbon Black ◽  
Uv Light ◽  
Light Exposure ◽  
Outdoor Exposure ◽  
Uv Exposure ◽  
Fluorescent Light ◽  
Exposure Condition ◽  
Coating Materials

The outdoor ultraviolet (UV) light exposure program according to ASTM D5970 and the indoor UV fluorescent lamp device according to ASTM G154 were used to evaluate the UV degradation in test polyester geogrids. Eighteen months’ worth of data were obtained from the outdoor program. UV-A-340 lamps and exposure condition No. 7 were used for the indoor program. The outdoor exposure program was conducted at Pingtung, in southern Taiwan. The annual sunlight exposure energy was 4,263.50 MJ/m2. The accumulated annual UV-A and UV-B energies were 256.56 and 0.83 MJ/m2, respectively. The tensile strength of the test geogrids decreased as the outdoor exposure increased, but the decrease in the rate of tensile strength also lessened as UV exposure increased. Carbon black and antioxidants contained in the coating materials have a significant influence on the rate of degradation for the test geogrids; 2% carbon black and 1% antioxidant by weight are recommended. The proportions of average retained ultimate tensile strength for 1 month, 12 months, and 18 months of outdoor exposure were 88%, 71%, and 66%, respectively. The tensile strength half-life cycle due to UV exposure was greater than 18 months. Similar behavior was also observed for the elongation at break. However, no clear trend was found for strength at 5% strain due to UV exposure. The reduction factors due to 18 months of outdoor exposure varied from 1.27 to 1.99. The average reduction factor was about 1.60. The reduction in ultimate tensile strength under 180 h of UV exposure in the indoor UV exposure test program was very significant. However, the rate of lost tensile strength for the second and third 180-h UV exposure was very small. The average retained tensile strengths for the geogrids under 180-h and 540-h exposures were 81% and 77%, respectively. The effect of 540-h fluorescent light exposure on the tensile strength of polyester geogrids coated with polyvinyl chloride was equivalent to 151 days of outdoor exposure at Pingtung.

scholarly journals Sodium Tungsten Oxide Bronze Nanowires Bundles in Adsorption of Methylene Blue Dye under UV and Visible Light Exposure

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1322
Author(s):  
Kunyapat Thummavichai ◽  
Le Anh Thi ◽  
Swee-Yong Pung ◽  
Oluwafunmilola Ola ◽  
Mian Zahid Hussain ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Visible Light ◽  
Uv Light ◽  
Light Exposure ◽  
Blue Dye ◽  
Methylene Blue Dye ◽  
Adsorption Effect ◽  
Sodium Tungsten ◽  
Oxide Bronze ◽  
Enhanced Adsorption

This paper describes the analysis and characterization of NayWOx bronze nanowires bundles and evaluation of their effective adsorption of methylene blue dye (MB). The Na-doped WOx bronze nanowires bundles were first synthesized via a simple solvothermal method, which were then fully characterized by using different techniques including TEM, XRD, XPS and UV-Vis, to validate the successful Na+ insertion into the WOx framework. The adsorption activities of the resulting NayWOx bronze nanowires bundles, compared with the undoped WOx form, were investigated by evaluating the adsorption effect on methylene blue under both UV and visible light irradiations. An enhanced adsorption performance of the Na-doped WOx bronze samples was recorded, which demonstrated a 90% of removal efficiency of the MB under different conditions (dark, visible and UV light). Moreover, the NayWOx bronze samples also offered a 4 times better kinetic rate of MB removal than the plain WOx nanowires.

scholarly journals Association among pterygium, cataracts, and cumulative ocular ultraviolet exposure: A cross-sectional study in Han people in China and Taiwan

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0253093
Author(s):  
Natsuko Hatsusaka ◽  
Naoki Yamamoto ◽  
Hisanori Miyashita ◽  
Eri Shibuya ◽  
Norihiro Mita ◽  
...  
Keyword(s):  
Uv Light ◽  
Light Exposure ◽  
Cross Sectional Study ◽  
Classification Systems ◽  
Uv Exposure ◽  
Cross Sectional ◽  
High Prevalence ◽  
Surface Disorder ◽  
Progress Rate ◽  
Ocular Surface Disorder

Purpose Pterygium is an ocular surface disorder mainly caused by ultraviolet (UV) light exposure. This study explored the relationships between six cataract types with pterygium and UV exposure. Methods We have previously studied cataracts in residents of three regions in China and Taiwan with different UV intensities. From that study, we identified 1,547 subjects with information on the presence or absence of pterygium. Pterygium severity was graded by corneal progress rate. Cataracts were graded by classification systems as three main types (cortical, nuclear, posterior subcapsular) and three subtypes (retrodots, waterclefts, fiber folds) with high prevalence in middle-aged and elderly people. We calculated the cumulative ocular UV exposure (COUV) based on subject data and National Aeronautics and Space Administration data on UV intensities and used logistic regression to calculate odds ratios for the associations of COUV, cataract, and pterygium. Results We found an overall pterygium prevalence of 23.3%, with significant variation among the three regions. Four cataract types (cortical, nuclear, posterior subcapsular, and retrodots) were significantly associated with the presence of pterygium. Conclusions There was a significant association between COUV and pterygium, indicating that COUV is associated with the risk of pterygium development and that pterygium is useful as an index of UV exposure. Furthermore, the type of cataract in eyes with pterygium may indicate the level of UV exposure.

scholarly journals Reaction of Apple Skin following UV Exposure

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 536B-536 ◽  
Author(s):  
Harold N. Fonda ◽  
John K. Fellman ◽  
X. Fan ◽  
J.P. Mattheis
Keyword(s):  
Room Temperature ◽  
Uv Light ◽  
Light Exposure ◽  
Short Wave ◽  
Apple Fruit ◽  
Uv Exposure ◽  
Temperature Dependent ◽  
C Storage ◽  
Fuji Apple ◽  
Atmosphere Storage

In order to investigate biochemical events occurring at the surface of apple skin, UV light exposure was used to generate a skin-browning reaction in apples. `Fuji' apple fruit that had been kept for 2 months in regular atmosphere storage at 0°C were exposed to short-wave UV light for 24 or 48 hr at 0°C or 23°C. After treatment, skin browning was monitored on fruit returned to 0°C storage or kept at room temperature under laboratory conditions. Fruit exposed to short-wave UV light at 0°C developed skin browning after 2 to 3 days at room temperature, whereas fruit held at 0°C did not show signs of skin browning until 7 days later. Short-wave UV exposure for 24 or 48 hr at 23°C resulted in skin browning that continued to develop on fruit kept at both room temperature and 0°C. When fruit were exposed to short-wave UV light for 72 hr at 0°C, a small amount of skin browning was already apparent. Long-wave UV light exposure for 48 hr had no observable effect on fruit treated at 0°C and then placed at room temperature. Our observations suggest that events that lead to browning are related to dispersion of energy absorbed by the hydrophobic molecules in the skin, a temperature dependent phenomenon.

Sorbitol enhances the physicochemical stability of B12 vitamers

2020 ◽  
Vol 90 (5-6) ◽  
pp. 439-447 ◽  
Author(s):  
Andrew Hadinata Lie ◽  
Maria V Chandra-Hioe ◽  
Jayashree Arcot
Keyword(s):  
Ascorbic Acid ◽  
Uv Light ◽  
Heat Exposure ◽  
Water Soluble ◽  
Uv Exposure ◽  
Physicochemical Stability ◽  
Before And After ◽  
The Stability

Abstract. The stability of B12 vitamers is affected by interaction with other water-soluble vitamins, UV light, heat, and pH. This study compared the degradation losses in cyanocobalamin, hydroxocobalamin and methylcobalamin due to the physicochemical exposure before and after the addition of sorbitol. The degradation losses of cyanocobalamin in the presence of increasing concentrations of thiamin and niacin ranged between 6%-13% and added sorbitol significantly prevented the loss of cyanocobalamin (p<0.05). Hydroxocobalamin and methylcobalamin exhibited degradation losses ranging from 24%–26% and 48%–76%, respectively; added sorbitol significantly minimised the loss to 10% and 20%, respectively (p < 0.05). Methylcobalamin was the most susceptible to degradation when co-existing with ascorbic acid, followed by hydroxocobalamin and cyanocobalamin. The presence of ascorbic acid caused the greatest degradation loss in methylcobalamin (70%-76%), which was minimised to 16% with added sorbitol (p < 0.05). Heat exposure (100 °C, 60 minutes) caused a greater loss of cyanocobalamin (38%) than UV exposure (4%). However, degradation losses in hydroxocobalamin and methylcobalamin due to UV and heat exposures were comparable (>30%). At pH 3, methylcobalamin was the most unstable showing 79% degradation loss, which was down to 12% after sorbitol was added (p < 0.05). The losses of cyanocobalamin at pH 3 and pH 9 (~15%) were prevented by adding sorbitol. Addition of sorbitol to hydroxocobalamin at pH 3 and pH 9 reduced the loss by only 6%. The results showed that cyanocobalamin was the most stable, followed by hydroxocobalamin and methylcobalamin. Added sorbitol was sufficient to significantly enhance the stability of cobalamins against degradative agents and conditions.

Tuning of Electronic Properties in Conducting Polymers

2001 ◽  
Vol 66 (8) ◽  
pp. 1208-1218 ◽  
Author(s):  
Guofeng Li ◽  
Mira Josowicz ◽  
Jiří Janata
Keyword(s):  
Hydrogen Bonding ◽  
Binding Site ◽  
Binding Sites ◽  
Polymer Chains ◽  
Electronic Transitions ◽  
Weakly Bound ◽  
Ordered Structures ◽  
Doped Polymer ◽  
Positively Charged ◽  
Repeated Cycling

Structural and electronic transitions in poly(thiophenyleneiminophenylene), usually referred to as poly(phenylenesulfidephenyleneamine) (PPSA) upon electrochemical doping with LiClO4 have been investigated. The unusual electrochemical behavior of PPSA indicates that the dopant anions are bound in two energetically different sites. In the so-called "binding site", the ClO4- anion is Coulombically attracted to the positively charged S or N sites on one chain and simultaneously hydrogen-bonded with the N-H group on a neighboring polymer chain. This strong interaction causes a re-organization of the polymer chains, resulting in the formation of a networked structure linked together by these ClO4- Coulombic/hydrogen bonding "bridges". However, in the "non-binding site", the ClO4- anion is very weakly bound, involves only the electrostatic interaction and can be reversibly exchanged when the doped polymer is reduced. In the repeated cycling, the continuous and alternating influx and expulsion of ClO4- ions serves as a self-organizing process for such networked structures, giving rise to a diminishing number of available "non-binding" sites. The occurrence of these ordered structures has a major impact on the electrochemical activity and the morphology of the doped polymer. Also due to stabilization of the dopant ions, the doped polymer can be kept in a stable and desirable oxidation state, thus both work function and conductivity of the polymer can be electrochemically controlled.

UV Irradiation of Shell Eggs: Effect on Populations of Aerobes, Molds, and Inoculated Salmonella typhimurium

1997 ◽  
Vol 60 (6) ◽  
pp. 639-643 ◽  
Author(s):  
FUENG-LIN KUO ◽  
JOHN B. CAREY ◽  
STEVEN C. RICKE
Keyword(s):  
Salmonella Typhimurium ◽  
Uv Radiation ◽  
Uv Light ◽  
The Other ◽  
Uv Exposure ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Fluorescent Light ◽  
Uv Treatment ◽  
Shell Eggs

The effects were investigated of 254-nm UV radiation on populations of Salmonella typhimurium, aerobes, and molds on the shells of eggs. In the first experiment, the CFU of attached S. typhimurium cells on unwashed clean shell eggs were determined after 0, 1, 3, 5, and 7 min of UV treatment (620 μW/cm2) on both ends of the egg. All UV treatments significantly reduced S. typhimurium CFU (P &lt; .01). UVtreatment (620 μW/cm2) in 1-min alternating light and dark cycles for 5 min (three light and two dark) was compared to 0, 3, and 5 min of UV treatment. No significant differences in microbial populations were observed among light and dark cycles and the other UV treatments. In a subsequent experiment, the same UV treatments were utilized to evaluate photoreactivation. After UV exposure, eggs were exposed to 1 h of fluorescent light or I h of darkness or cultured immediately. S. typhimurium CFU were significantly (P &lt; .01) reduced by the UV treatments. However, no significant differences between microbial populations exposed to UV treatment and UV radiation plus photoreactivation were detected. For studies of aerobic bacteria and molds, different UV treatment times (0, 15, and 30 min) at the intensity of 620 μW/cm2 and different intensities (620, 1350, and 1720 μW/cm2) for 15 min were evaluated. Mold CFU per egg were either 0 or 1 for all UV treatments and a 99% reduction of CFU of aerobic bacteria per egg were observed for all UV treatments. It appears from these studies that UV light can significantly reduce populations of S. typhimurium, aerobes, and molds on shell eggs.

scholarly journals Stability and ocular biodistribution of topically administered PLGA nanoparticles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sean Swetledge ◽  
Renee Carter ◽  
Rhett Stout ◽  
Carlos E. Astete ◽  
Jangwook P. Jung ◽  
...  
Keyword(s):  
Uv Light ◽  
Light Exposure ◽  
Polymeric Nanoparticles ◽  
Plga Nanoparticles ◽  
Eye Disease ◽  
Control Group ◽  
Eye Tissues ◽  
Nanoparticle Morphology ◽  
The Stability

AbstractPolymeric nanoparticles have been investigated as potential delivery systems for therapeutic compounds to address many ailments including eye disease. The stability and spatiotemporal distribution of polymeric nanoparticles in the eye are important regarding the practical applicability and efficacy of the delivery system in treating eye disease. We selected poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with lutein, a carotenoid antioxidant associated with eye health, as our model ophthalmic nanodelivery system and evaluated its stability when suspended in various conditions involving temperature and light exposure. We also assessed the ocular biodistribution of the fluorescently labeled nanoparticle vehicle when administered topically. Lutein-loaded nanoparticles were stable in suspension when stored at 4 °C with only 26% lutein release and no significant lutein decay or changes in nanoparticle morphology. When stored at 25 °C and 37 °C, these NPs showed signs of bulk degradation, had significant lutein decay compared to 4 °C, and released over 40% lutein after 5 weeks in suspension. Lutein-loaded nanoparticles were also more resistant to photodegradation compared to free lutein when exposed to ultraviolet (UV) light, decaying approximately 5 times slower. When applied topically in vivo, Cy5-labled nanoparticles showed high uptake in exterior eye tissues including the cornea, episcleral tissue, and sclera. The choroid was the only inner eye tissue that was significantly higher than the control group. Decreased fluorescence in all exterior eye tissues and the choroid at 1 h compared to 30 min indicated rapid elimination of nanoparticles from the eye.

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