Impact modified epoxy/montmorillonite nanocomposites: synthesis and characterization

Diglycidyl ether of bisphenol A type epoxy resin-polyether polyol-organically treated montmorillonite ternary nanocomposites were synthesized in this study. The effects of addition of polyether polyol as an impact modifier on morphological, thermal and mechanical properties of nanocomposites were investigated by X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry, impact and tensile testing. The results showed that organically treated montmorillonite is intercalated by epoxy, since the interlayer spacing expanded from 1.83 to 3.82 nm upon nanocomposite synthesis. The addition of polyether polyol impact modifier had no effect on the interlayer spacing. SEM examination showed that polyol forms an immiscible phase in the epoxy matrix. Thermal characterization of nanocomposites indicated an increase in T_g with respect to both polyether polyol and montmorillonite contents. The impact strength of the samples with no clay was improved approximately 160% upon adding 7 wt% polyether polyol. In polyether polyol modified nanocomposites, the impact and tensile strengths decreased with respect to increasing amount of montmorillonite and showed a maximum with respect to the polyether polyol content at constant clay loading. The Young's modulus of the nanocomposites exhibited an increase with respect to the montmorillonite loading and showed a maximum with respect to the polyol content at each clay loading.     

Viscoelastic properties of reactive and non‐reactive blends of ethylene‐methyl acrylate copolymers with styrene‐maleic anhydride copolymer

The effects of compatibilizing reactions on the viscoelastic properties and morphology of ethylene‐methyl acrylate copolymers were studied. Potentially reactive blends of styrene‐maleic anhydride copolymer (SMAH) and a terpolymer of ethylene/methyl acrylate/glycidyl methacrylate (E‐MA‐GMA) were compared with a non‐reactive blend of SMAH and an ethylene/methyl acrylate (E‐MA) copolymer with similar rheological properties. Melt mixing was carried out in a batch mixer and in a co‐rotating twin screw extruder. The morphology of the reactive blends showed smaller domain sizes than the non‐reactive blends, and the viscoelastic properties of the blends were very different. The storage and loss moduli and the complex viscosity of the reactive blends were greater than those of non‐reactive blends. The reactive blends had a higher zero shear viscosity, plateau modulus and mean relaxation time than their non‐reactive counterparts, indicating a higher degree of melt elasticity. The melt elasticity was maximum at 25% functionalized ethylene‐methyl acrylate concentration.     

Polystyrene–organoclay nanocomposites prepared by melt intercalation,in situ,and masterbatch methods

In this study, polystyrene (PS)/montmorillonite nanocomposites were prepared by melt intercalation, in situ polymerization, and masterbatch methods. In the masterbatch method, as the first step, a high clay content composite of PS–organoclay (masterbatch) was prepared by in situ polymerization, and then the prepared masterbatch was diluted to desired compositions with commercial PS in a twin‐screw extruder. The structure and mechanical properties of the nanocomposites were examined. X‐ray diffraction (XRD) analysis showed that the d‐spacing of the in situ formed nanocomposites increased from 32.9 Å for the organoclay powder to 36.3 and 36.8 Å respectively in nanocomposites containing 0.73 and 1.6 wt% organoclay, indicating intercalation. However, the d‐spacing of the other prepared materials remained nearly unchanged when compared with pure organoclay powder. Thus, at these low clay contents, in situ formed nanocomposites showed the best improvement in mechanical properties including tensile, impact strength, and Young's modulus. In situ polymerization method did not prove to be efficient at high clay loadings in terms of intercalation and mechanical properties. At high clay loadings, the effects of the three methods in promoting mechanical properties were not significantly different from each other. POLYM. COMPOS., 27:249–255, 2006. © 2006 Society of Plastics Engineers     

Single stage hydrogen production from cellulose through photo-fermentation by a co-culture of Cellulomonas fimi and Rhodopseudomonas palustris

Biohydrogen production from cellulose by a bacterial co-culture is a potentially promising approach for producing bioenergy from a low cost substrate. The use of a cellulolytic bacterium, Cellulomonas fimi, permits cellulose conversion and the in situ production of substrate for growth and hydrogen production by the photosynthetic bacterium Rhodopseudomonas palustris. Response surface methodology (RSM) with a Box-Behnken design (BBD) was used to examine variations in the key parameters: substrate (cellulose) concentration, yeast extract concentration and the microorganism ratio (Rps. palustris/C. fimi). For the co-culture of R. palustris and C. fimi the highest hydrogen production (44 mmol H₂/L) was achieved at the highest substrate concentration (5 g/L); however, the highest hydrogen yield (3.84 mol H₂/mol glucose equivalent) was observed at the lowest cellulose concentration and highest microorganism ratio. High COD removal efficiencies, over 70%, were achieved over a wide range of conditions and were positively affected by the concentration of yeast extract.     

Ethylene‐methyl acrylate‐glycidyl methacrylate toughened poly(lactic acid) nanocomposites

Poly (lactic acid) (PLA) was melt blended in a twin screw extruder using an ethylene‐methyl acrylate‐glycidyl methacrylate rubber as a toughener. PLA/rubber blends were immiscible as observed by scanning electron microscopy. Impact strength and ductility of PLA were improved by the addition of the rubber at the expense of strength and stiffness. An organo‐montmorillonite (OMMT) was used at 2 wt % to counteract the negative effect of the rubber on modulus, and balanced properties were observed at 10 wt % rubber content. X‐ray diffraction and transmission electron microscopy revealed the formation of intercalated/exfoliated structure in the ternary nanocomposites. Thermal behavior analysis indicated that the degree of crystallinity is slightly affected by the clay and the rubber. Both the clay and the rubber decreased the crystallization temperature of PLA and acted as nucleating agents for PLA. The viscosity of the mixtures as measured by melt flow index was highly influenced by the rubber and the OMMT. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Jacobi polynomials approximation to the one-speed neutron transport equation

Jacobi polynomials, the largest family of classical orthogonal polynomial sequence, are used to obtain eigenspectrum of one-speed neutron transport equation for strongly anisotropic scattering. Previously detailed Ultraspherical or Gegenbauer polynomials approximation including spherical harmonics, Chebyshev polynomials approximation of first and second kinds is a special case of Jacobi polynomials approximation in which the two variables of the Jacobi polynomials are equal. Eigenspectrum calculations using the so-called Jacobi polynomials approximation have demonstrated that plane symmetrical systems prefer Ultraspherical polynomials approximation since their well-known peculiarity or symmetry property meets the requirement of symmetry in angular flux with respect to spatial coordinates for every order of approximation. In the more general case when two variables of Jacobi polynomial are unequal, symmetry in eigenvalues disappear in the low-order approximations. However, it has been shown that symmetrical eigenvalue pairs are reached asymptotically as the order of approximation is increased for unequal variables too. Jacobi polynomials approximation is further applied to homogeneous slab criticality problem with strongly anisotropic scattering and reflected boundaries. Additionally, very useful analytical recursive relations for the calculation of various types of integrals involving Jacobi polynomials are derived which are needed in the eigenspectrum and criticality calculations.     

Rheological behavior of styrene‐maleic anhydride/polyol blends obtained through reactive processing

The condensation reaction of styrene‐maleic anhydride copolymer (SMAH) with polytetramethylene ether glycol (PTMEG) in the presence or absence of a hydrated zinc acetate catalyst was studied in a batch mixer. As a control, pure SMAH and an SMAH/catalyst blend were also subjected to the same processing conditions. The reaction characteristics of the blends were investigated by Fourier transform infrared spectroscopy (FTIR) and thermal and rheological analysis. FTIR analysis of the SMAH/PTMEG blend indicated ester formation. The addition of zinc acetate and/or PTMEG to SMAH decreased the glass transition temperature of pure SMAH. Oscillatory shear properties of storage modulus, G′, loss modulus, G″, and complex viscosity, η*, were measured. The SMAH/PTMEG/zinc acetate blend had higher G′, G″, and η* than the blend without the zinc acetate catalyst. The parameters of the relaxation spectra were calculated by using the experimental oscillatory data and the generalized Maxwell model. Zero shear viscosity and the mean relaxation time increased with addition of zinc acetate and/or PTMEG to SMAH as a result of chain extension/branching reactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2615–2623, 2002     

Harnessing the Power of GPUs to Speed Up Feature Selection for Outlier Detection

Acquiring a set of features that emphasize the differences between normal data points and outliers can drastically facilitate the task of identifying outliers. In our work, we present a novel non-parametric evaluation criterion for filter-based feature selection which has an eye towards the final goal of outlier detection. The proposed method seeks the subset of features that represent the inherent characteristics of the normal dataset while forcing outliers to stand out, making them more easily distinguished by outlier detection algorithms. Experimental results on real datasets show the advantage of our feature selection algorithm compared with popular and state-of-the-art methods. We also show that the proposed algorithm is able to overcome the small sample space problem and perform well on highly imbalanced datasets. Furthermore, due to the highly parallelizable nature of the feature selection, we implement the algorithm on a graphics processing unit （GPU） to gain significant speedup over the serial version. The benefits of the GPU implementation are two-fold, as its performance scales very well in terms of the number of features, as well as the number of data points.     

Reactive processing and properties of styrene–maleic anhydride and poly(tetramethylene ether glycol)

The anhydride/hydroxyl‐functionalized blends of styrene–maleic anhydride (SMAH) with poly(tetramethylene ether glycol) (PTMEG) in the presence or absence of a hydrated zinc acetate catalyst were produced in a batch mixer and in a corotating twin‐screw extruder. In batch mixing, torque values increased with time as a result of chain‐extension/branching reactions. The reaction products were studied by thermal, mechanical, morphological, and spectroscopic characterization techniques. The glass transition temperature of SMAH was lowered by the addition of PTMEG into the system. Major morphological changes were observed at the initial stages of extrusion. The changes in the screw speed influenced the mechanical properties and morphology of the blends. SMAH/PTMEG blends were brittle due to the glassy nature of SMAH. FTIR analysis of the SMAH/PTMEG system showed carboxylic acid and ester formation in the extrusion experiments. Mechanical property data and FTIR spectra indicated that at 150 rpm chain‐extension/branching reactions were maximized due to ester formation. However, at 220 rpm, a lower extent of ester formation was observed due to the lower residence time in the extruder. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2148–2156, 2002