Poly(methyl methacrylate)‐modified epoxy/amine system for reactive rotational moulding: crosslinking kinetics and rheological properties

BACKGROUND: The rotational moulding of thermosetting resins is hampered by their low viscosity and the abrupt increase in their viscosity as they polymerize. This study investigates the use of poly(methylmethacrylate) (PMMA) as a rheological processing aid in reactive blends of an aromatic diepoxy resin (diglycidyl ether of bisphenol‐A, DGEBA) and an aromatic diamine (diethyltoluenediamine, DETDA) by studying the miscibility, curing, rheology, dynamic properties and morphology of the uncured solutions and of the resulting highly crosslinked polymer blends. RESULTS: The PMMA was miscible in the uncured resins as expected from consideration of their solubility parameters, and the effect of PMMA concentration on the glass transition temperature, measured via differential scanning calorimetry (DSC), was fitted to several models. Addition of PMMA significantly increased the viscosity of the uncured blend which obeyed the log‐additivity rule. The curing behaviour was monitored using DSC, infrared spectroscopy and dynamic rheology and it was found that addition of PMMA caused a small reduction in rate due to a dilution effect. The dynamic and steady shear rheologies were used to determine the gel point and gel relaxation index. Dynamic mechanical thermal analysis provided evidence for phase separation of the components into PMMA‐rich domains and an epoxy‐rich matrix and this was confirmed with electron microscopy studies. CONCLUSION: These results indicate that addition of small amounts of PMMA to DGEBA/DETDA enlarges the processing window with regards to the rotational moulding of thermosets. In addition, the blending of small amounts (ca 10 wt%) of PMMA with the DGEBA/DETDA resin appears to cause only a modest sacrifice in thermal resistance. Copyright © 2009 Society of Chemical Industry     

Insertion de lanthanoides dans le graphite

The intercalation of lanthanides is possible by two different ways: direct action of the metal vapor in metallic tubes sealed under vacuum or by heating compressed mixture of powders of the metal and of graphite.The first method was used only for the most volatile metals: samarium, europium, thulium and ytterbium (see Table 1). The 00 l reflexions of the corresponding first stage graphitides MC₆ (M = Sm, Eu, Tm or Yb) were obtained for samples prepared from pyrolytic graphite HOPG (Tables 2 and 3, Fig. 1).Using the second method, we determined the identity period along the c axis (I_c) for the most fusible lanthanides graphitides (Table 4).We did a study of the evolution vs temperature of a compressed mixture of initial composition Yb + 6C (Fig. 2).A structural study was carried out on single crystals of europium and ytterbium graphitides, using a special method developed in the laboratory.Figure 3 shows the three possible types of sites available to the metal atoms and the different stacking modes of the metallic layers.The hkO and hkl reflexions of the graphitide YbC₆ (see Table 5) shown in Fig. 5 allow to choose between the three possible unit cells of Fig. 4. The hexagonal unit cells of EuC₆ and YbC₆ belong to the space group P6₃/mmc with two of three sites occupied regularly by the metal atoms. The two metal atoms are in position b and the twelve carbon atoms in i. The parameters are respectively $\text{a = 4.314 ± 0.003}\text{A}\text{?}$, $\text{c = 9.745 ± 0.008}\text{A}\text{?}\text{(EuC}{}_6\text{)}$ and $\text{a = 4.320 ± 0.004}\text{A}\text{?}$, $\text{c = 9.147 ± 0.004}\text{A}\text{?}\text{(YbC}{}_6\text{)}$.     

Interference of Soil Contaminants with Laccase Activity During the Transformation of Complex Mixtures of Polycyclic Aromatic Hydrocarbons in Liquid Media

The biotransformation of 16 polycyclic aromatic hydrocarbons (PAHs) in mixture was investigated in reactors in the presence of purified laccases of the fungus Pycnoporus cinnabarinus, ABTS as a redox mediator, 25% acetonitrile, and Tween 20. Several hydrocarbons from a synthetic mixture, such as anthracene and benzo[ a ]pyrene, were converted up to 80% into quinones, whereas others also belonging to three- and five-ring chemicals were less transformed. Chrysene and benzo[ k ]fluoranthene were not oxidized by the laccase mediator system. Moreover, hydrocarbons extracted from an industrial soil were all recalcitrant to enzymatic attack. This lack of reactivity of the laccases toward the hydrocarbons could be due to the presence of interfering compounds coextracted from the soil, such as metals.     

Analysis/Synthesis of Sounds Generated by Sustained Contact Between Rigid Objects

This paper introduces an analysis/synthesis scheme for the reproduction of sounds generated by sustained contact between rigid bodies. This scheme is rooted in a Source/Filter decomposition of the sound where the filter is described as a set of poles and the source is described as a set of impulses representing the energy transfer between the interacting objects. Compared to single impacts, sustained contact interactions like rolling and sliding make the estimation of the parameters of the Source/Filter model challenging because of two issues. First, the objects are almost continuously interacting. The second is that the source is generally unknown and has therefore to be modeled in a generic way. In an attempt to tackle those issues, the proposed analysis/synthesis scheme combines advanced analysis techniques for the estimation of the filter parameters and a flexible model of the source. It allows the modeling of a wide range of sounds. Examples are presented for objects of various shapes and sizes, rolling or sliding over plates of different materials. In order to demonstrate the versatility of the approach, the system is also considered for the modeling of sounds produced by percussive musical instruments.      

干涉图生成过程中几个问题的研究

合成孔径雷达 (SAR)图像本身含有的数据量非常巨大 ,如何有效地处理这些数据 ,尽快得到期望的结果 ,非常重要 .针对干涉图生成过程中如何有效减小相关系数计算量、节省计算时间 ,去掉不良控制点两个主要问题进行了分析研究 ,并且提出了新的、有效的方法 .实验证明 ,这些方法对于提高计算效率、改善精度的有效性     

Correlation between sizing formulation and compressive behavior of concentrated glass bundle suspensions

The correlation between sizing formulation, bundle mechanical characteristics, and bundle–matrix static and dynamic interactions are investigated. Two glass‐fiber sizing formulations are considered, one containing polyvinyl acetate (PVAc) and the other polyester/PVAc, as conventionally used in sheet molding compounds (SMC). Axial compression tests are conducted on dry two‐dimensional (2D) random suspensions. The forced packing is governed by the bending of fiber bundle segments between bundle‐bundle contact points. Benchmarking of the experimental curves with a modified theoretical model provides an estimation of the fiber bundle bending rigidity under forced packing conditions. This value is found to depend on the bundle sizing as well as on the interaction with solvents present in the matrix as is the case for SMC. Free flow and molding experiments are performed on planar SMC sheets using the two different fiber bundles as reinforcements. The results confirm the dependence of the molding energy and the SMC rheology on the bundles chemical and mechanical characteristics. POLYM. COMPOS., 26:370–376, 2005. © 2005 Society of Plastics Engineers     

Enhancing the order picking process through a new storage assignment strategy in forward-reserve area

This paper reexamines the order picking process in a warehouse facing the challenges that e-commerce brings about and which are characterised by a very large number of small sized orders and returns. Implementing effective storage assignment strategies combined with efficient batching, in this context, is very fundamental to keep the warehouse’s responsiveness and order completion times up to the standards. This paper investigates a new storage assignment strategy, initially implemented by a large shoes and footwear wholesaler, to enhance the performance of the order picking process in its warehouses. The impact of this new storage assignment strategy on the performance of the order picking process is analysed via simulation. The performance of the system, measured in terms of total picking time as well as order lead time while taking congestion into account, is compared to the cases where conventional storage assignment strategies are implemented. A full factorial design is set up and the simulation output is statistically analysed. The results of this analysis are reported and thoroughly discussed. Attending to the results, the proposed strategy presents a remarkable potential to shorten total picking travel distances and order completion time and consequently customer satisfaction.