Degradation of photovoltaic backsheets: Comparison of the aging induced changes on module and component level

In reliability testing of components for PV modules an always remaining question is about material (in)compatibilities and synergistic effects and thus, how results of singly tested materials correlate with materials aged within PV modules. Testing of single materials would simplify sample preparation, reduce costs and offer more testing options. Therefore the main objective of this study was to compare the aging behavior of single backsheets with that of backsheets incorporated within PV modules. Four different types of backsheets were chosen, all of them comprising of polyethylene terephthalate (PET) core layers, but differing outer protection layers. Test modules using identical components, varying only in the type of backsheet used were produced and damp heat aged (85°C/85% RH ≤2000 h). The results revealed no influence of the PV module lamination on the thermal characteristics of the polymeric backsheets. Even after DH aging, differences between single and module laminated backsheets were negligible. Degradation effects of PET could be detected for all aged sheets by thermal analysis and were confirmed by tensile tests and rheological measurements. Thus, it can be stated that testing of single PET based backsheets under DH aging conditions is a practicable way to investigate the applicability of a new backsheet. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42093.     

Insensitive high explosives: VI. experimental determination of the chemical compatibility of nitroguanidine with seven high explosives**

Two compatibility test types based on gas generation obtained by vacuum stability test (VST) procedure and on heat generation obtained by heat flow microcalorimetry (HFMC) show that nitroguanidine (NGu), CAS-No. [556-88-7], is compatible with ammonium nitrate (AN), CAS-No. [6484-52-2], ammonium dinitramide (ADN), CAS-No. [140456-78-6], 1,1-diamino-dinitroethylene (FOX-7, DADNE), CAS-No. [145250-81-3], N-guanylurea dinitramide (FOX-12, GUDN, carbamoylguanidinium dinitramide), CAS-No. [217464-38-5], hexogen (RDX), CAS-No. [121-82-4], octogen (HMX), CAS-No. [2691-41-0], and trinitrotoluene (TNT), CAS-No. [118-96-7]. The evaluations with gas generation and heat generation were done using the so-called corresponding reactivity quantities R_V and R_Q, but the assessment criteria are in accordance with the present NATO standards. NGu and ADN show the rare case of reactivity with a negative assessment quantity, that is their inter-component reactivity quantities show negative values in R_V and R_Q. The evolved gas volume and the produced heat generation of the 1 : 1 mixture have lower values than the formally calculated values of the mixture. The root cause of this cannot be deduced with mere compatibility testing. A negative assessment quantity R_Q is also observed with NGu and TNT at 80 °C, but not at 70 °C.     

Development and evaluation of methods for determining the pattern of functionalization in sodium carboxymethylcelluloses

Sodium carboxymethylcellulose (NaCMC) with varying degrees of substitution (DS) was investigated with different analytical methods in order to characterize the functional group distribution. The following methods were tested and adapted: high-resolution ¹³C NMR spectroscopy in the solid state (¹³C CP/MAS NMR) and ¹³C NMR spectroscopy on solutions of NaCMC samples with a reduced molar mass. Partial degradation was accomplished by ultrasonic means and with the enzyme endoglucanase. Combining the two techniques resulted in the greatest reduction in molar mass and hence in the best spectral resolution. Analysis of the NaCMC fragments following ultrasonic and/or endoglucanase degradation also reveals another interesting experimental finding. It appears that ultrasonic degradation is favored at unsubstituted areas near the center of the chain. These methods were compared with the following already familiar techniques of analysis: titrimetric techniques; ¹³C and ¹H NMR spectroscopy as well as HPLC on completely hydrolysed solutions (hydrolysis with perchloric acid, trifluoroacetic acid and sulfuric acid). All of the methods characterize the samples as a series with increasing DS, the values of which range from 0.9 to 2.4. Methods that permit analysis of the partial degree of substitution produced the distribution x₂ > x₆ > x₃. Therefore, they are in principle suited for determining the functionalization pattern of the NaCMC samples relative to one another. The most suitable method can therefore be selected according to the objectives and the apparatus available. However, the measured values do exhibit considerable spread, variances of approx. 20%, thus, place restrictions on using the values of DS or x_i in absolute comparisons beyond these methods.     

居德布兰河谷旅游项目—河边桑拿

河边桑拿位于一条美丽的河边,可以全景观赏远山的景色。它建在菲多斯景观酒店附近,供酒店的客人使用。桑拿房有一面玻璃墙,朝向景区。建筑物建在地形中,除玻璃墙外,四周用青草覆盖。