Influence of annealing on the permeation properties of a thermoplastic elastomer

The use of plastic films with specific diffusion or permeation properties for industrial applications has grown at a considerable rate. Some useful applications are found in medical devices, bioreactors, and combustible fuel storage where polymer films function as separation membranes that allow permeation of different gases at different rates. In this work, the permeation and diffusion properties of a polyester‐based thermoplastic polyurethane (TPU) were investigated. TPU injected and extruded specimens were subjected to thermal treatment (annealing) at 100°C for 20 h. Injected samples were exposed to certain hygrothermal conditions and films were prepared to evaluate the influence of annealing on the permeation of gases. In order to achieve a complete analysis, tests such as differential scanning calorimetry, tensile tests, and Fourier transform infrared spectroscopy were conducted to examine the morphological changes. These were then correlated to the TPU permeation behavior after annealing. Water uptake by the polymer—measured as weight gain—likely indicates an increase in the free volume in the amorphous domains. Similarly, in permeation and water immersion tests, the diffusion rate of gases and H₂O through the TPU was higher for the annealed samples when compared to those without treatment, indicating that diffusion within the polymer is dependent on the postprocessing thermal treatment. POLYM. ENG. SCI., 59:1810–1817, 2019. © 2019 Society of Plastics Engineers     

IR spectroscopy: Suitable method for determination of curing degree and crosslinking type in melamine–formaldehyde resins

Melamine–formaldehyde (MF) resins are widely used as adhesives and finishing materials in the wood industry. During resin cure, either methylene ether or methylene bridges are formed, leading to the formation of a three-dimensional resin network. Not only the curing degree, but also the chemical species present in the cured resin determine the quality of the final product. Analytical methods allowing a detailed investigation of network formation are of great benefit to manufacturers. In the present work, resin cure of an MF precondensate is studied at different temperatures (100–200 °C) without considering the initial pH as a factor. Isoconversional kinetic analysis based on exothermal curing enthalpies enables calculation of the crosslinking degree at a given time/temperature regime. A semiquantitative determination of the chemical groups present is performed based on solid-state nuclear magnetic resonance data. Fourier transform infrared spectroscopy has shown to be a fast and reliable analytical tool with high sensitivity toward functional groups and with great potential for at-line process control. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47691.     

Temporal trends, congener patterns, and sources of octa-, nona-, and decabromodiphenyl ethers (PBDE) and hexabromocyclododecanes (HBCD) in Swiss lake sediments

With the recent ban of pentabromodiphenyl ether (technical PentaBDE) and octabromodiphenyl ether (technical OctaBDE) mixtures in the European Union (EU) and in parts of the United States, decabromodiphenyl ether (technical DecaBDE) remains as the only polybrominated diphenyl ether (PBDE) based flame retardant available, today. The EU risk assessment report for DecaBDE identified a high level of uncertainty associated with the suitability of the current risk assessment approach for secondary poisoning by debromination of DecaBDE to toxic lower brominated diphenylethers. Addressing this still open question, we investigated concentrations and temporal trends of DecaBDE, NonaBDE, and OctaBDE congeners in the sediments of Greifensee, a small lake located in an urban area close to Zürich, Switzerland. PBDE appeared first in sediment layers corresponding to the mid 1970s. While total Tri-HeptaBDE (BDE-28, -47, -99, -100, -153, -154 and -183) concentrations leveled off in the mid 1990s to about 1.6 ng/g dw (dry weight), DecaBDE levels increased steadily to 7.4 ng/g dw in 2001 with a doubling time of 9 years. Hexabromocyclododecanes (HBCD) appeared in Greifensee sediments in the mid 1980s. They are an important class of flame retardants that are being used in increasing amounts, today. As was observed for DecaBDE, HBCD concentrations were continuously increasing to reach 2.5 ng/g dw in 2001. Next to DecaBDE, all 3 NonaBDE congeners (BDE-208, BDE-207, and BDE-206) and at least 7 out of the 12 possible OctaBDE congeners (BDE-202, BDE-201, BDE-197/204, BDE-198/203, BDE-196/200, BDE-205, and BDE-194) were detected in the sediments of Greifensee. Highest concentrations were found in the surface sediments with 7.2, 0.26, 0.14, and 1.6 ng/g dw for Deca-, Nona-, Octa-, and the sum of Tri-HeptaBDE, respectively. While DecaBDE and NonaBDE were found to increase rapidly, the increase of OctaBDE was slower. Congener patterns of Octa- and NonaBDE present in sediments of Greifensee did not change with time. Consequently, there was no evidence for sediment mediated long-term transformation of PBDE within the observed time span of almost 30 years. Despite the high persistence of DecaBDE, environmental debromination occurs, as shown by the detection of a shift in congener patterns of Octa- and NonaBDE in sediments, compared to the respective congener patterns in technical PBDE products. The OctaBDE congener BDE-202 was detected in sediments, representing a transformation product that is not reported in any of the technical PBDE products. Comparison of OctaBDE congener patterns in sediments with OctaBDE congener patterns from known sources reveals that (i) they were distinctively different from the congener patterns in technical PBDE products and (ii) that they were similar to the OctaBDE patterns in house dust and photodegradation products of DecaBDE, suggesting contributions from these sources.     

Determination of polycyclic aromatic hydrocarbons in smoked pork by effect-directed bioassay with confirmation by chemical analysis

Polycyclic aromatic hydrocarbons (PAHs) are generated during smoke curing and other heating treatments of food and represent a large class of chemical pollutants including a number of carcinogens. At present, PAHs are frequently detected by costly and time-consuming chemical analysis. Effect-directed in vitro cell-based bioassays of contaminants can offer a rapid, sensitive, and relatively inexpensive alternative for screening of contaminants in comparison to instrumental analysis. They enable estimation of total biological activity of all compounds acting through the same mode of binding. The aryl hydrocarbon receptor as a binding site plays an important role in PAH-induced carcinogenesis. The in vitro chemical-activated luciferase expression assay (using conditions to detect PAH) was investigated for its applicability for effect-directed analysis of PAH levels in smoked meat. There was an intra-assay variability of 0 to 15% and a mean coefficient of variation of 25% (3 to 50%) for the cleanup and bioassay analysis of the smoked pork samples. There was a correlation between the total responses of the bioassay and the individual amounts of the PAHs with a high molecular weight. The comparison of 2,3,7,8-tetrachlorodibenzo-p-dioxin and benzo[k]fluoranthene used as standard in the in vitro chemical-activated luciferase expression assay resulted in benzo[k]fluoranthene being able to be used as an alternative, nontoxic standard in the bioassay. This bioassay is an applicable effect-directed functional prescreening method for the analysis of PAHs in smoked meat and appears to have potential in being used for food control in the future.     

Four‐junction spectral beam‐splitting photovoltaic receiver with high optical efficiency

A spectral beam‐splitting architecture is shown to provide an excellent basis for a four junction photovoltaic receiver with a virtually ideal band gap combination. Spectrally selective beam‐splitters are used to create a very efficient light trap in form of a 45° parallelepiped. The light trap distributes incident radiation onto the different solar cells with an optical efficiency of more then 90%. Highly efficient solar cells including III–V semiconductors and silicon were fabricated and mounted into the light trapping assembly. An integrated characterization of such a receiver including the measurement of quantum efficiency as well as indoor and outdoor I–V measurements is shown. Moreover, the optical loss mechanisms and the optical efficiency of the spectral beam‐splitting approach are discussed. The first experimental setup of the receiver demonstrated an outdoor efficiency of more than 34% under unconcentrated sunlight. Copyright © 2010 John Wiley & Sons, Ltd.     

Smart 概念——苹果加工的全套解决方案

酶制剂在苹果汁生产中的作用 在苹果原料的成熟和储存过程中,苹果细胞壁的多糖也在逐步演变,苹果会慢慢变软,一些多糖会部分溶解.这些多糖都具备高度的持水性,能将果汁保持在果浆中,导致可榨性降低,出汁率下降.为了确保苹果出汁率达到最佳水平.必须在榨汁阶段加入果浆酶.     

Batch Tests for Optimisation of Solvent Composition and Process Flexibility of the CHALMEX FS-13 Process

ABSTRACT

Studies have been performed with the purpose of determining the optimal solvent composition of a Chalmers grouped actinide extraction (CHALMEX) solvent for the selective co-extraction of transuranic elements in a novel Grouped ActiNide EXtraction (GANEX) process. The solvent is composed of 6,6’-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo-[1,2,4]-triazin-3-yl)-[2,2’]-bipyridine (CyMe₄-BTBP) and tri-n-butyl phosphate (TBP) in phenyl trifluoromethyl sulfone (FS-13). The performance of the system has been shown to significantly depend on the ratios of the two extracting agents and the diluent to one another. Furthermore, the performance of the determined optimal solvent (10 mM CyMe₄-BTBP in 30% v/v TBP and 70% v/v FS-13) on various simulated PUREX raffinate solutions was tested. It was found that the solvent extracts all transuranic elements with high efficiency and good selectivity with regard to most other elements (fission products/activation products) present in the simulated PUREX raffinate solutions. Moreover, the solvent was found to extract a significant amount of acid. Palladium, silver, and cadmium were co-extracted along with the TRU-radionuclides, which has also been observed in other similar CHALMEX systems. The extraction of plutonium and uranium was preserved for all tested simulated PUREX raffinate solutions compared to experiments using trace amounts.     

Anisotropy Effects in the Shape-Memory Performance of Polymer Foams

Isotropic and anisotropic shape-memory polymer foams are prepared by supercritical carbon dioxide foaming from a multiblock copolymer (PDLCL) consisting of poly(ω-pentadecalactone) and poly(ε-caprolactone) segments. Analysis by micro-computed tomography reveals for the anisotropic PDLCL foam cells a high shape anisotropy ratio of R = 1.72 ± 0.62 with a corresponding Young's compression moduli ratio between longitudinal and transversal direction of 4.3. The experimental compression data in the linear elastic range can be well described by the anisotropic open foam model of Gibson and Ashby. A micro-morphological analysis for single pores using scanning electron microscopy images permits the correlation between the macroscopic stress-compression behavior and microscale structural changes.     

Curing behavior of a UV-curable inkjet ink: Distinction between surface-cure and deep-cure performance

Safety requirements and the need of low-migration UV inks have received increasing attention in the packaging industry. Crucial for the development and design of low-migration UV inkjet inks for migration-sensitive applications is the polymerization degree. In this study, curing-behavior of a black, high purity packaging ink (HPP-ink) was monitored using ATR-FTIR spectroscopy. UV irradiation of HPP-ink led to changes in specific absorption bands of the FTIR spectra due to crosslinking reaction of double bonds. Changes in absorptions bands at 1,408 and 1,321 cm⁻¹ permitted the determination of CC conversion of acrylic and vinyl double bond, independently of one another. In addition, a method was developed which allows the investigation of surface-cure and deep-cure behavior, separately.     

A concise nodal-based derivation of the floating frame of reference formulation for displacement-based solid finite elements

Multibody System Dynamics - The Floating Frame of Reference Formulation (FFRF) is one of the most widely used methods to analyze flexible multibody systems subjected to large rigid-body motion but...