Encapsulation of PV modules using ethylene vinyl acetate copolymer as a pottant: A critical review

The primary purpose of this work is to review the literature about what is and is not known about using ethylene vinyl acetate (EVA0 copolymer as the encapsulant (or pottant) material in photovoltaic (PV) modules. Secondary purposes include elucidating the complexity of the encapsulation problem, providing an overview about encapsulation of PV cells and modules, providing a historical overview of the relevant research and development on EVA, summarizing performance losses reported for PV systems deployed since ca. 1981, and summarizing the general problems of polymer stability in a solar environment. We also provide a critical review of aspects of reported work for cases that we believe are important.Failure modes resolved in the early work to establish reliability of deployed modules and the purposes and properties of pottants, are summarized. Typical performance losses in large field-deployed, large-scale systems ranging from 1% to 10% per year are given quantitatively, and qualitative reports of EVA discoloration are summarized with respect to ultraviolet (UV), world-wide location and site dependence.The general stability of polymers and their desirable bulk properties for solar utilization are given. The stabilization formulation for EVA, its effectiveness, and changes in it during degradation are discussed. The degradation mechanisms for the base resin, e.g., unstabilized Elvax 150^TM, and stabilized EVA are indicated for literature dating to the early 1950s, and the role played by unsaturated chromophores is indicated. The limited number of studies relating discoloration and PV cell efficiency are summarized.Observed degradation of EVA or the unstabilized base resin in the laboratory and examples used to measure the degradation are summarized in sections entitled: (1) thermally-induced degradation; (2) photodegradation and photothermal degradation of EVA in different temperature regimes; (3) photobleaching and photodegradation of the UV absorber and cross-linking agent; (4) acetic acid and metal and metal-oxide catalyzed oxidative degradation; and (5) discolaration and PV cell efficiency losses.Processing effects/influences on EVA stability are discussed in sections entitled: (1) EVA raw materials and extruded, uncured films; (2) thermal encapsulation processes; (3) effects of lamination, curing, and curing peroxide on gel content and chromophores formed; and (4) incomplete shielding of curing-generated chromophores. A summary is given for the limited number of accelerated lifetime testing efforts and examples of erroneous service lifetime predictions for EVA are discussed. The known factors that effect the discoloration rate of several EVA formulations are discussed in which the reduction in rate by using UV-absorbing superstrates is a prime example. A summary is given of what is and is not known about EVA degradation mechanisms, degradation from exposures in field-deployed modeules and/or laboratory testing, and factors that contribute to EVA stability or degradation. Finally, conclusions about using Elvax 150 in EVA formulations are summarized, and future prospects for developing the next-generation pottant for encapsulating PV modules are discussed.     

Photoresponsive peptide and polypeptide systems: part II. Photochromism of poly(l-ornithine) containing various azo-contents in side chains

Poly(L-ornithine)s having various azo-contents in the side chains were synthesized by the water-soluble carbodiimide procedure. The photochemical properties of the polypeptides poly[N^δ-p-(phenylazo)benzoyl-L-ornithine] (PPABLO) containing 3–77 mol% azobenzene were investigated by absorption and circular dichroism spectroscopy in hexafluoro-2-propanol (HFIP) or water, and in HFIP-water or methanol-water solvent mixtures. The photochromism of the dichroic bands of the PPABLOs containing 20–77 mol% azobenzene in the visible and ultraviolet wavelength regions was found to be mostly reversible as a function of irradiation time at different wavelengths due to the photostationary state (above 80% trans-cis photoisomerization) of the azo aromatic moieties. The PPABLO containing 3.2 mol% azobenzene in water exhibited conformational changes from random coil to helix by the addition of methanol or sodium dodecyl sulphate (SDS). The photo-induced conformational change was observed in HFIP-water-SDS solvent mixtures, while no conformational change was seen in water and HFIP-water solvent mixtures.     

The effects of bleached and unbleached rosemary oleoresins on light-sensitized oxidation of soybean oil

Bleached and unbleached forms of a rosemary oleoresin (RO) in stripped and nonstripped soybean oil behave both as antioxidant and prooxidant in a light-induced oxidative system. At 0.02 and 0.05% levels, RO had the greatest antioxidant activity, while at 0.01 and 0.5% levels it had the highest prooxidant activity in both stripped and nonstripped soybean oil. Treatment of both soybean oil systems with tertiary butylhydroquinone controlled light-induced oxidation of the oil better than did the oleoresin treatments. The prooxidant activity of the 0.5% RO level was probably due to an excess of prooxidant components being carried into the oil at that level, whereas the reduced antioxidant activity at 0.01% was probably due to the low initial level of active antioxidant components being added to the oil. Published as Journal Series No. 10072, Nebraska Agricultural Research Division, Department of Food Science and Technology, University of Nebraska, Lincoln, NE 68583-0919.     

不变黄HDI-PU/P(MMA-HEMA)互穿网络胶粘剂形态与性能的研究翁祥

制备了HDI(1,6-己二异氰酸酯)型聚酯聚氨酯/聚(甲基丙烯酸甲酯-甲基丙烯酸-β羟乙酯)(HDI-PU/P(MMA-HEMA))互穿网络胶粘剂,研究了接枝剂甲基丙烯酸-β羟乙酯(HEMA)用量对其形态、性能与分子结构的影响。结果表明,接枝剂HEMA可使分散相接枝到连续相中形成复合网络,从而改善其界面的相容性,提高其胶液粘度和初粘力,并可广泛作为制鞋工业用胶。     

Multi-Stage Phase-Segregation of Mixed Halide Perovskites under Illumination: A Quantitative Comparison of Experimental Observations and Thermodynamic Models

Photo- and charge-carrier-induced ion migration is a major challenge when utilizing metal halide perovskite semiconductors for optoelectronic applications. For mixed iodide/bromide perovskites, the compositional instability due to light- or electrical bias induced phase-segregation restricts the exploitation of the entire bandgap range. Previous experimental and theoretical work suggests that excited states or charge carriers trigger the process, but the exact mechanism is still under debate. To identify the mechanism and cause of light-induced phase-segregation phenomena, the full compositional range of methylammonium lead bromide/iodide samples are investigated, MAPb(Br_xI_1-x)₃ with x = 0…1, by simultaneous in situ X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy during illumination. The quantitative comparison of composition-dependent in situ XRD and PL shows that at excitation densities of 1 sun, only the initial stage of photo-segregation is rationalized with the previously established thermodynamic models. However, a progression of the phase segregation is observed that is rationalized by considering long-lived accumulative photo-induced material alterations. It is suggested that (additional) photo-induced defects, possibly halide vacancies and interstitials, need to be considered to fully rationalize light-induced phase segregation and anticipate the findings to provide crucial insight for the development of more sophisticated models.     

低黄变和亲水性氨基聚硅氧烷的开发

概述了氨基聚硅氧烷的发展历程、特点及发展趋势,着重介绍了氨基聚硅氧烷的黄变机理,低黄变氨基聚硅氧烷、亲水性氨基聚硅氧烷的开发,以及氨基聚硅氧烷的生态环保性。     

A new instrument for passive remote sensing: 2. Measurement of leaf and canopy reflectance changes at 531 nm and their relationship with photosynthesis and chlorophyll fluorescence

A previously described passive remote sensing fluorimeter (see companion paper) was modified to detect changes in the reflectance of vegetation. The utility of this remote sensing technique to measure the Physiological Reflectance Index (PRI) is shown at both leaf level under laboratory conditions and at the canopy level in the field. PRI, defined as the relative changes in reflectance at 531 nm with respect to those at 570 nm (PRI=R531−R570/R531+R570), is related to xanthophyll-related, dynamic changes of non-photochemical quenching of chlorophyll fluorescence. The robustness of this relationship by simultaneous remote sensing of PRI and chlorophyll fluorescence is strengthened. At the leaf level, the existence of two kinetically distinct components of PRI is shown. A fast (within seconds) component that is partly attributed to ΔpH induced chloroplast shrinkage, and a slow (within minutes), main component that is related to xanthophyll de-epoxidation, as demonstrated by its disappearance in the presence of DTT. Overall, PRI correlated better with non-photochemical quenching of chlorophyll fluorescence (NPQ) than with any other measured parameter, including the photochemical efficiency of PSII. Finally, at the canopy level and under field conditions, it is shown that PRI can be a useful tool for remote sensing of water stress in grapevines.     

季铵化改性氨基聚硅氧烷的合成及应用性能

采用氯乙酸乙酯对N,N-二甲基-γ-氨丙基-γ-氨丙基聚二甲基硅氧烷(ASO-121)进行季铵化改性,合成了一种季铵化改性氨基聚硅氧烷(QASO-121)。利用红外光谱(IR)、核磁共振氢谱(1HNMR)、扫描电镜(SEM)、纳米粒度仪等仪器对QASO-121及其乳液进行了表征和纤维表面的成膜性分析,并讨论了氨值、黏度及硅乳用量对所整理织物应用性能的影响。结果表明,QASO-121乳液平均粒径为75.3 nm,电位为+21.2mV,且其在织物纤维表面具有良好的成膜性。经氨值为0.6 mmol/g、黏度为2.600 Pa·s、硅乳用量为4 g/L的QASO-121整理的布样,织物柔软性提高,亲水性增强,白度基本不变。将QASO-121与未季铵化ASO-121进行应用性能对比,发现两者整理织物的柔软性相近,但经QASO-121所整理织物具有良好的亲水性且富有弹性,其抗黄变性能也得到了改善。     

负载TiO2陶瓷纤维与高得率浆混抄对纸张强度和返黄性能的影响

论文探讨了负载TiO_2陶瓷纤维与高得率浆混抄对纸张强度性能、光学性能和抑制返黄性能的影响。结果表明,陶瓷纤维负载不同尺寸的TiO_2(普通TiO_2和纳米TiO_2)对纸张性能的影响存在明显差异。相同的无机物加填量时,负载纳米TiO_2陶瓷纤维与高得率浆混抄纸张的抗张强度、耐破强度、撕裂度和层间结合强度等强度性能优于负载普通TiO_2的纸张,但光学性能(白度和不透明度)、抑制返黄性能均不如负载普通TiO_2的纸张。把负载普通TiO_2的陶瓷纤维与高得率浆中进行混抄,可以显著提高纸张的白度、不透明度及抑制返黄性能;当无机物加填量33.8%时,对高得率浆纸张的返黄抑制度达到81.3%(基于PC值的降低)。     

环保型抗氧化剂FK-161D6

研究了不含己二酸二酰肼(ADH)的抗氧化剂FK-161D6在锦氨纶弹性织物预定形及后定形工艺中的应用,并与传统抗氧化剂及其他非ADH类抗氧化剂进行对比.结果表明,抗氧化剂FK-161D6具有优异的抗高温黄变性能及抗酚黄变性能,而且对染色影响小,不吸附游离甲醛,可完全替代传统ADH类抗氧化剂用于锦氨纶弹性织物的预定形及后...