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Effects of Electron-Beam Irradiation and Ultraviolet Light (365 nm) on Polylactic Acid Plastic Films
Strips of Ca-I [polylactic acid (PLA) monolayer plastic films from Cargill Dow Polymers LLC, Minnetonka, MN] cut in the machine and nonmachine directions were irradiated with an electron beam using a CIRCLE III Linear Accelerator (MeV Industries S.A., Jouy-en-Josas, Cedex, France). The effects of 33-kGy irradiation on the physical properties of the Ca-I strips were studied. In addition, the effects of ultraviolet (UV) light (365-nm) illumination on the degradation of three PLA plastic films, Ch-I (PLA monolayer plastic films from Chronopol, Golden, CO), GII (PLA trilayer plastic films from Cargill Dow Polymers LLC), MN), and Ca-I (PLA monolayer plastic films from Cargill Dow Polymers LLC) were analyzed by a modified ASTM D5208-91 method. Results showed that irradiation had decreased the weight-average molecular weight (M
w), stress at break, percentage of elongation, and strain energy of Ca-I by 35.5, 26.7, 32.3, and 44.8%, respectively (P < 0.01). The shelf life of the irradiated Ca-I strips at 5°C and <20 ± 5% RH was about 6 months. The degradation rate of Ch-I, GII, and Ca-I with no UV light treatment at 55°C and 10% RH was 2512, 5618, and 3785 M
w/week, respectively. Under the UV light illumination (365 nm), the degradation rate of Ch-I, GII, and Ca-I, was 2982, 8722, and 7467 M
w/week, respectively. Hence, the degradation rate of GII and Ca-I was increased 55 and 97% by UV light (P < 0.008), respectively. This trend was not observed in Ch-I because its starting M
w (78,000 g/mol) was close to the tensile strength lost range (50,000 to 75,000 g/mol) of PLA films. To our knowledge, this is the first study to demonstrate that UV light does further enhance the degradation of PLA films. 相似文献
124.
以渠江-嘉陵江、涪江-嘉陵江交汇处水体为研究对象,探究了河流交汇处水体磷素形态特征及紫外光照的影响.水体磷形态分析结果表明,研究的所有水体中总磷浓度均超过水体富营养化阈值(0.2 mmol·m-3),支流汇入干流前后,研究水体中总磷(TP)主要由总溶解性磷(TDP)组成,而溶解性无机磷(DIP)是TDP的主要组成部分.两支流汇入嘉陵江后,干流水体中各形态磷浓度均较干流汇合前升高,颗粒态磷(PP)增幅最大,达到129%.按水体相对分子质量(Mr)分级结果表明,溶解态高相对分子质量组分(0.5×103~10×103)中的磷为溶解性磷(DP,<0.22μm)主要成分,达到47%~61%,渠江和涪江两支流汇入干流后,嘉陵江水体不同相对分子质量组分中的磷含量并未发生较大变化.通过紫外光照后,游离态组分(<0.5×103)中的磷含量明显增加,增幅在10%~29%,其余两组分中磷含量均降低,和涪江-嘉陵江汇合处样本相比,渠江-嘉陵江汇合处水体胶体态组分(Mr10×103~0.22μm)中磷含量降幅大于前者.通过紫外光照实验,证明了紫外光照是影响水体中磷素地球化学过程的重要环境因素. 相似文献
125.
以水生植物水花生(Alternanthera philoxeroides,空心莲子草)和丙烯酸为接枝共聚原料,通过自由基反应制备高吸水性树脂,对接枝聚合物进行FTIR、SEM的结构表征,同时对影响吸水树脂性能的因素进行优化。当水花生干粉用量10 g时,优化条件如下:活化温度为35℃,丙烯酸单体与水花生干粉质量比为6:1,丙烯酸中和度为56%,引发剂过硫酸钾的用量为单体质量的1%,交联剂N,N-亚甲基双丙烯酰胺用量为单体质量的0.075%,引发温度为65℃。在此优化条件下制备的吸水性树脂吸水性能最好,对去离子水吸水倍数达到442 g/g。 相似文献
126.
Photocatalytic degradation of phenol on different phases of TiO2 particles was examined under 400-W UV irradiation. The effects of various operating parameters including TiO2 dosage, solution pH (4–10), and initial phenol concentration (0.13–1.05 mM) on phenol degradation were investigated. Three forms of TiO2 photocatalysts such as pure anatase phase, pure rutile phase, and the mixed phase were prepared by sol-gel method and followed annealing at different temperatures. The annealing temperature used were 500 °C, 700 °C and 900 °C for pure anatase phase, the mixed phase, and pure rutile phase, respectively. It was shown that pure anatase TiO2 exhibited higher photocatalytic activity than the physical mixture of pure anatase and rutile TiO2. Moreover, the TiO2 particle with a specific fraction of mixed anatase and rutile phases exhibited better performance than pure anatase TiO2. Finally, the degradation rate could be satisfactorily fitted by a pseudo-first-order kinetic model. 相似文献
127.
The graft copolymerization of the starch and acrylic were used to prepare the superabsorbent, and the high oil-absorbing resin was also studied preliminarily. In addition, following the method of the emulsion polymerization, the cerium nitrate amine was regarded as the initiator, the acrylic amide and the methyl methacrylate functioned as the monomer. There are several significant parameters taken into consideration such as the factors that influence the performance of the superabsorbent and the high oil-absorbing resin, the dosage of the initiator amount, the ratio of the starch and the monomer and the dosage of crosslinking agent. 相似文献
128.
129.
In this study, the adsorption characteristics of As(III) and As(V) from water and wastewater using polyacrylamide-grafted banana stem with quaternary ammonium functionality (PGBS-AE) were investigated. Infrared spectroscopic, and thermogravimetric analyses were performed to affirm the polymer grafting, functionality, morphology, and thermal stability. Batch experiments were carried out to understand the effect of contact time, concentration, pH, adsorbent dose, and temperature of the solution for the adsorption of As(III) and As(V) onto PGBS-AE. Equilibrium was achieved within 1 h and the optimum pH was found to be 9.0 and 3.0 for As(III) and As(V), respectively. Isotherm studies showed that the Langmuir equation fits best. Maximum adsorption capacities of 50 and 5.5?g?kg?1 were obtained for As(III) and As(V) at 30°C. The endothermic nature of adsorption was evident as the adsorption efficiency increased with temperature. The thermodynamic parameters were evaluated to explain the feasibility of adsorption and to predict the nature of adsorption. The competence of the adsorbent for practical purposes was also analyzed by treating with a fertilizer industry effluent sample. Studies pertaining to adsorbent regeneration and readsorption of As(III) and As(V) were carried out for four consecutive cycles. 相似文献
130.
Anthony A. Provatas Gary A. Epling James D. Stuart Aliaksandr Yeudakimau 《毒物与环境化学》2013,95(3):353-361
Acetonitrile is a commonly used solvent in both industry and research. The treatment of acetonitrile wastes in dilute aqueous solutions with visible light offers advantages to chemical treatment and ultraviolet (UV) irradiation. This study presents the degradation of acetonitrile via a photoinduced electron transfer reaction in the presence of a photosensitizer (dye) and a sacrificial reductant under visible light. Acetonitrile photodegradation (photoreduction) was investigated utilizing a variety of sacrificial reductants and photosensitizers. Optimal results were observed in the presence of methylene green and tri-isopropanolamine with a decrease of acetonitrile in solution to 86% in 24 hours. The only photoreaction product observed was acetaldehyde and a plausible mechanism for the photochemical degradation of acetonitrile is proposed. 相似文献