The Barrier Effect of EVOH versus 1,4,7‐Triaxocyclotridecane‐8,13‐Dione,a Non‐intentionally Added Compound from Polyurethane Adhesives in Multilayer Food Packaging

The presence and migration of non‐intentionally added substances in food packaging materials are the big concerns nowadays in terms of food safety, and the identification and quantitation are an important analytical challenge. Among non‐intentionally added substances, 1,4,7‐trioxacyclotridecane‐8,13‐dione, a by‐product resulting from the interaction between ingredients in many polyurethane adhesives, has been identified and quantified. Migration tests were carried out with food simulant E (Tenax®) and 3% acetic acid (simulant B) stored at 40°C/10 days using different adhesives and with different film thickness in the presence and absence of EVOH layer. After the exposure, Tenax® was extracted and analysed by gas chromatography with mass spectrometry. For 3% acetic acid, the analyses were directly performed by the Acquity® ultra‐performance liquid chromatography system coupled to triple quadrupole mass spectrometer detector. A possible degradation of the lactone after migration tests with 3% acetic acid occurred, and total degradation after 8 days was confirmed. Two compounds were detected and identified, which were also found in the migration extracts. Partition experiments were carried out from laminates composed by polypropylene film, adhesive and non‐treated polyethylene film at 40°C for 10 days. After this, the polypropylene/adhesive and polyethylene layers were independently extracted and analysed by gas chromatography with mass spectrometry. Diffusion studies were carried out following the Moisan procedure. The results and conclusions are shown and discussed.     

Dual‐grid‐based tree/cotree decomposition of higher‐order interpolatory H(∇∧, Ω) basis

This work extends the zeroth‐order tree/cotree (TC) decomposition method into higher order (HO) interpolatory elements and develops the constraints operator required for the elimination of spurious solutions for general HO spectral basis. Earlier methods explicitly enforce the divergence condition that requires a mixed finite element (FE) formulation with both H¹ and H(?∧) expansions and involves repeated solutions of the Poisson equation. A recent approach, which avoids the mixed formulation and the Poisson problem, uses TC decomposition of edge DoF over the primal graph and construction of integration and gradient matrices. The approach is easily applied to HO hierarchical elements but becomes quite complex for HO spectral elements. In the presence of internal DoF, it is difficult to utilize the primal graph for an explicit decomposition of the spectral DoF. In contrast, this work utilizes the dual grid, resulting in an explicit decomposition of DoF and construction of constraint equations from a fixed element matrix. Thus, mixed formulation and the Poisson problems are avoided while eliminating the need for evaluation of integration and gradient matrices. The proposed constraints matrix is element‐geometry independent and possesses an explicit sparsity formulation reducing the need for dynamic memory allocation. Numerical examples are included for verification. Copyright © 2010 John Wiley & Sons, Ltd.     

Mikrostruktur und mechanische Eigenschaften der reibgeschweißten γ‐TiAl‐Feingusslegierung Ti‐47Al‐3.5(Mn+Cr+Nb)‐0.8(B+Si)

Microstructure and mechanical properties of friction welded γ‐TiAl based alloy Ti‐47Al‐3.5(Mn+Cr+Nb)‐0.8(B+Si) in investment cast condition. This paper describes properties of joints produced by friction welding of the intermetallic γ‐TiAl based alloy Ti‐47Al‐3.5(Mn+Cr+Nb)‐0.8(B+Si) in investment cast and hot‐isostatically pressed condition. The effect of friction welding parameters on microstructure and local properties are examined and discussed. It is found that the properties of the joint are essentially affected by properties of as‐cast Ti‐47Al‐3.5(Mn+Cr+Nb)‐0.8(B+Si) base material, both at room temperature and 700 °C.