The effect of introduction of carbon nanotubes on the physicomechanical properties of polyvinylacetate

The physicomechanical properties of polyvinylacetate (PVA) with small, no more than 2 wt.%, additions of carbon nanotubes (CNTs) are investigated. Data on the influence of CNT concentration on the differential scanning calorimetry thermograms, thermal destruction, electrical resistance, water vapor sorption, as well as indices of the mechanical properties of PVA/CNT (yield stress, strength, elastic modulus, ultimate elongation, and short-term creep) are reported. A variant of calculation of the elastic constants of the nanocomposite is considered with account of the effect of nanotube agglomeration.     

A single step approach to piperidines via Ni-catalyzed β-carbon elimination

An easy and expeditious route to substituted piperidines is described. A Ni-phosphine complex was used as catalyst for [4 + 2] cycloaddition of 3-azetidinone and alkynes. The reaction has broad substrate scope and affords piperidines in excellent yields and excellent regioselectivity. In the reaction of an enantiopure azetidinone, complete retention of stereochemistry was observed.     

New Intermetalloid Ge9-clusters with Copper and Gold: Filling Vacancies in the Cluster Chemistry of [Ge9(Hyp)3]− (Hyp=Si(SiMe3)3)

We present a series of new intermetalloid clusters (R₃P)CuGe₉₍(Hyp)₃, (R=Me, Et, iPr, nBu, tBu) (Hyp=Si(SiMe₃)₃) (R₃P)AuGe₉(Hyp)₃MGe₉(Hyp)₃ (R=Ph, Me; M=Au, Cu). In conjunction with already known clusters, these give new insights into the bonding situation of metal bridged Ge₉ clusters as well as a better understanding of the formation of these clusters. Additionally, the intermetalloid clusters with the smallest phosphine PMe₃ show new bonding motives.     

Simultaneous kriging-based estimation and optimization of mean response

Robust optimization is typically based on repeated calls to a deterministic simulation program that aim at both propagating uncertainties and finding optimal design variables. Often in practice, the “simulator” is a computationally intensive software which makes the computational cost one of the principal obstacles to optimization in the presence of uncertainties. This article proposes a new efficient method for minimizing the mean of the objective function. The efficiency stems from the sampling criterion which simultaneously optimizes and propagates uncertainty in the model. Without loss of generality, simulation parameters are divided into two sets, the deterministic optimization variables and the random uncertain parameters. A kriging (Gaussian process regression) model of the simulator is built and a mean process is analytically derived from it. The proposed sampling criterion that yields both optimization and uncertain parameters is the one-step ahead minimum variance of the mean process at the maximizer of the expected improvement. The method is compared with Monte Carlo and kriging-based approaches on analytical test functions in two, four and six dimensions.     

Properties of a composite prepared using a concentrate of carbon nanotubes in polyethylene

Results of an investigation into the properties of polyethylene (PE) with small, no more than 5 wt.%, additions of multiwall carbon nanotubes (CNTs) are reported. Specimens of the composite were prepared using a concentrate containing 31.6 wt.% of nanotubes in the polyethylene matrix. The concentrate was fabricated by a patent in situ polymerization method. Experimental data on the influence of CNT additions on the thermograms of differential scanning calorimetry, the crystallinity of the polyethylene matrix, and the indices of mechanical properties (yield stress, strength, elastic modulus, ultimate elongation, and long-term creep) of PE/CNT composite are obtained. A theoretical analysis of elastic properties of the PE/CNT composite was carried out by using the Mori–Tanaka theory of an equivalent medium. The calculation results are compared with experimental data.     

Mechanical Properties of High-Density Polyethylene/Chlorinated Polyethylene Blends

Results of experimental investigation of mechanical properties of high-density polyethylene (HDPE)/chlorinated polyethylene (CPE) blends in tension are reported. The specimens of pure HDPE, CPE, and nine types of HDPE/CPE blends, with different component ratios at 10 wt.% intervals, are examined. The features of the stress-strain curves obtained are discussed. Data on the influence of blend composition on the elastic modulus, yield stress, breaking stress, and ultimate elongation are obtained. The results of investigations into the creep behavior are also presented. It is found that the creep compliance obeys the power law of creep with coefficients depending on blend composition.     

Cross-linked thermoplastic blends of polyethylene with an elastomer 4. Thermorelaxation and adhesion characteristics

The results of an experimental investigation of changes in the thermorelaxation and thermoshrinkage stresses and the strength of adhesion joints with steel of binary blends of high-density polyethylene with an elastomer (ethylene-propylene-dicyclopentadiene terpolymer) in the course of γ-radiation and chemical cross-linking are reported. The interconnection/relationship between the highest values of the stresses, as well as the characteristics of formation processes of the joints, and certain structural characteristics of the blends (content of their cross-linked part, the degree of crystallinity, etc.) is discussed. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 265–278, March–April, 2006.     

The effect of silane concentration on the adsorption of poly(vinyl acetate-co-maleate) and γ -methacryloxypropyl- trimethoxysilane onto E-glass fibers

The adsorption of a poly(vinyl acetate-co-maleate) (PVAM) emulsion onto E-glass fibers was investigated along with sizing formulations prepared by mixing the PVAM with varying concentrations of -methacryloxypropyltrimethoxysilane (MPS). The sized E-glass fibers were then characterized using Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). Loss on Ignition (LOI) along with the DRIFT spectra indicated that the addition of silane to the PVAM emulsion caused a decrease in the amount of size on the fiber. The decrease in amount of size on the E-glass fibers did not coincide with a decrease in surface coverage, instead the XPS results indicated surface coverage had increased with silane addition. These results showed that small increases in the silane concentration appear to affect the amount of size adsorbed to the E-glass fibers     

Synthesis and characterization of an isocyanate functionalized polyhedral oligosilsesquioxane and the subsequent formation of an organic-inorganic hybrid polyurethane

Organic-inorganic hybrids are an important class of new materials that offer improved thermal and mechanical properties over normal polymers. They may be produced by either the sol-gel route or through the use of inorganic compounds possessing reactive functional groups. Polyhedral oligosilsesquioxanes (POSS) are completely defined molecules of nanoscale dimensions that may be functionalized with reactive groups suitable for the synthesis of new organic-inorganic hybrids. Here we report the synthesis and characterization of a novel POSS possessing eight isocyanate groups via the hydrosilylation of octakis(hydridodimethylsiloxy)octasilsesquioxane (Q8M8H) and m-isopropenyl-alpha,alpha'-dimethylbenzyl isocyanate (m-TMI). The suitability of this new macromer to the synthesis of a organic-hybrids has been explored by forming a new type of highly cross-linked polyurethane elastomer via reaction of the macromer with poly(ethylene glycol) using dibutyltin dilaurate catalyst.