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Photo‐oxidation of poly(ethylene terephthalate) films intended for photovoltaic backsheet
摘要： The photodegradation of 36 μm thick poly(ethylene terephthalate) ?lm under arti?cial weathering conditions has been investigated. A weatherometer was used to expose samples to a broad wavelength range of light in an oxidative environment, replicating outdoor exposure. Irradiations were also performed using UV lamps of wavelengths 302 and 365 nm light, in an oxidative environment. After exposure, the extent of degradation was determined using attenuated total re?ectance Fourier transform infrared spectroscopy, diffuse re?ectance infrared Fourier transform spectroscopy, UV–visible spectroscopy, ?uorescence spectroscopy, differential scanning calorimetry, contact angle measurements, and scanning electron microscopy. Results show the production of a series of degradation products, including carboxylic acid end groups, anhydrides, aldehydes, quinones, and monohydroxy terephthalate groups.
关键词： poly(ethylene terephthalate),photodegradation,UV lamps,weatherometer,oxidative environment,degradation products
更新于2025-09-12 10:27:22
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Kinetics, mechanism, and identification of photodegradation products of phenazine-1-carboxylic acid
摘要： Phenazine-1-carboxylic acid (PCA) is a broad-spectrum antibiotic against many plant pathogens, produced by Pseudomonas and other species. The biosynthesis and regulation of PCA has been well documented, but there is no report about its photochemical properties. Herein, the photodegradation of PCA was carried out in an aqueous solution under the irradiation of visible light to investigate the kinetics, mechanism, and identification of photodegradation products of PCA. Results revealed that photodegradation of PCA accorded well with first-order reaction kinetics. The measured half-life of PCA was 2.2 days at pH 5.0 and increased to 37.6 days at pH 6.8 when exposed to visible light. When oxygen was removed from its solution, the half-life of PCA was doubled. Different units of superoxide dismutase (SOD) enzyme (i.e. 0 units, 300 units, and 3000 units) and varying concentrations of sodium azide (i.e. 0 mg, 5 mg, 10 mg, and 20 mg) were used to decipher the mechanism for PCA photodegradation. Hydroxyl PCA and hydroxy phenazine were tentatively identified as the degradation products of PCA photodegradation process by high-performance liquid chromatography (HPLC). The obtained degradation products were further characterized and confirmed by HPLC-mass spectrometry and LC-MS/MS-based analytical approaches. In conclusion, the degradation of PCA was found to be light dependent, which could be accelerated by hydrogen ion and oxidant in the solution. The results suggest that PCA was more stable when stored in a neutral or alkaline environment or in the dark. Therefore, it is important to modify the PCA structure or use a suitable dosage for its broad-spectrum applications.
关键词： First-order kinetics,Biological pesticide,Photodegradation,Phenazine-1-carboxylic acid,LC-MS,Degradation products
更新于2025-09-09 09:28:46