Interpretation of long-chain structure from dilute solution properties of ultrahigh molecular weight polymers

Summary Systematic studies on solution properties of ultrahigh molecular weight polymers showed the existence of some special features as compared to usual length polymers. The paper discusses the possible appearance of branched structures in the polymerization process, structures able to influence the mentioned features. From experimental data on poly(methyl methacrylate), poly(butyl methacrylate) and polyacrylonitrile it appears that branching can be excluded, and the very high molecular weight domain considered may be responsible for the modifications observed in the molecular weight dependences on 2>, A₂ or [].     

Flow Properties of Ultrahigh-Molecular-Weight Poly(Methyl Methacrylate) in Semidilute Solutions

The article presents some Theological results obtained on a large domain of shear rates for semidilute solutions of ultrahigh-molecular-weight poly(methyl methacrylate) at different concentrations. The observed unusual behavior was explained as being due to the flow instabilities of long-chain polymers in an entangled state.     

Composite Ni/Al2O3 coatings and their corrosion resistance

Composite coatings Ni/Al₂O₃ were electrochemically deposited from a Watts bath. Al₂O₃ powder with particle diameter below 1 μm was codeposited with the metal. The obtained Ni/Al₂O₃ coatings contained 5-6% by weight of corundum. The structure of the coatings was examined by scanning electron microscopy (SEM). It has been found that the codeposition of Al₂O₃ particles with nickel disturbs the nickel coating's regular surface structure, increasing its microcrystallinity and surface roughness. DC and AC electrochemical tests were carried out on such coatings in a 0.5 M solution of Na₂SO₄ in order to evaluate their corrosion resistance. The potentiodynamic tests showed that the corrosion resistance of composite coating Ni/Al₂O₃ is better than that of the standard nickel coating. After 14 days of exposure the nickel coating corrodes three times faster than the Ni/Al₂O₃ coating. The electrochemical behaviour of the coatings in the corrosive solution was investigated by electrochemical impedance spectroscopy (EIS). An equivalent circuit diagram consisting of two RC electric circuits: one for electrode, nickel corrosion processes and the other for processes causing coating surface blockage, were adopted for the analysis of the impedance spectra. The changes in the charge transfer resistance determined from the impedance measurements are comparable with the changes in corrosion resistance determined from potentiodynamic measurements.     

Synthesis and surface properties of new dicephalic saccharide-derived surfactants

A new group of nonionic dicephalic saccharide amides, N-dodecyl-N,N-bis[(3-d-gluconylamido)propyl]-amine, N-dodecyl-N,N-bis[(3-d-glucoheptonylamido)propyl]-amine, and N-alkyl-N,N-bis[(3-lactobionylamido)propyl]amines (alkyl: n-C₁₂H_25′ n-C₁₆H_33′, n-C₁₈H₃₇) were synthesized and characterized. Their structure and purity were confirmed by means of ¹H and ¹³C nuclear magnetic resonance analysis and electrospray ionization mass spectrometry. Carbon spectra were verified using a DEPT experiment. The surface and interfacial properties such as critical micelle concentration (CMC), standard free energy of micellization, ΔG _CMC, surface excess concentration, Γ_CMC, and surface area demand per molecule, A _CMC, were determined. The tertiary nitrogen atom seems to have a surprising effect on surfactnat packing at the interface.     

Alkylation of Hydroquinone with tert-butanol over Silica-immobilized Triflate Derivatives

Friedel-Crafts alkylations of α-methylnaphthalene with various alkylating agents were first carried out in the presence of methanesulfonic acid (MeSA). The Brønsted acid catalyst MeSA exhibited outstanding catalytic performance, and was found to be excellent catalyst and solvent for alkylation reaction of aromatic hydrocarbon. It’s found that alkenes can be used as excellent alkylating agent for alkylation of α-methylnaphthalene. The effects of various reaction parameters like type of alkylating agent, dosages of catalysts, reaction temperature and reaction time were investigated in detail. Moreover, the performance of reuse for catalysts was also studied. It’s found that, under the optimal reaction conditions, more than 90% of conversion for olefins and 100% of selectivity for the desired products were obtained. Compared with traditional catalysis technology, the reaction, catalyzed by MeSA catalyst, no volatile solvents needed, good selectivity for desired products could be obtained. The catalyst can be isolated easily from the reaction mixtures by decantation, and was successfully reused. The methanesulfonic acid could be considered as environmentally friendly novel catalyst and solvent for long-chain alkylation of α-methylnaphthalene with alkenes. The catalytic reaction mechanism for alkylation in the presence of MeSA was proposed as well.     

A Michael-type reaction between acrylato ions and ethylenediamine coordinated to Ni(II). Synthesis,crystal structure and magnetic properties of [Ni2(EDDP)2(H2O)2] · 2H2O (H2EDDP = ethylenediamine-N,N-dipropionic acid)

The reaction between NiCO₃ · Ni(OH)₂, acrylic acid and ethylenediamine in a 2:4:1 molar ratio affords the binuclear complex, [Ni₂(EDDP)₂(H₂O)₂] · 2H₂O 1. The organic ligand, EDDP^2? (the dianion of the ethylenediamine-N,N-dipropionic acid ligand), results from the addition of one amine group to the carbon–carbon double bonds of two acrylato ions. The crystal structure of 1 consists of neutral centrosymmetric entities, with the nickel ions connected by two carboxylato groups, each one acting as a monoatomic bridge. The intramolecular Ni?Ni distance is 3.212 Å. The metal ions exhibit an octahedral geometry. The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the nickel(II) ions (J = ?21.8 cm^?1, H = ?JS_Ni1S_Ni2).     

Correlation Between Cutting Data Selection and Chip Form in Stainless Steel Turning

This article presents investigations related to the turning of stainless steel as a representative of difficult-to-cut materials and the effectiveness of selected chip breakers working in the local machining environment. Martensitic steel AISI 416 was used to test two commercially available types of chip breaker. The efficiency of a chip breaker working in the range of cutting conditions recommended (by the tool manufacturers) was the aim of the turning tests. As a result of the investigations an algorithm of cutting condition selection, combining both the cutting tests and the simulation procedure for the efficiency of the chip breaker was created. The vision system, equipped with a high-speed camera was used for chip form estimation. Simultaneously, the cutting force components were measured to check if the simulation calculation was correct. The FEM simulation was applied to estimate the manner in which the chip groove was filled. The article presents certain recommendations for cutting condition correction in the local machining environment for the purpose of achieving an acceptable chip form.     

An agile production network enabled by reconfigurable manufacturing systems

Emergencies, and efforts to address them, create disruptions to local and global supply chains and surges in demand of emergency resources, which substantially affect global production. Reconfigurable manufacturing systems are promising solutions to improve flexibility and to reduce the effort needed to adapt supply chains and production networks to fit a perturbed environment. This paper proposes a method for coordination of reconfigurable manufacturing resources from multiple enterprises to structure ad-hoc production networks for critical products required in emergencies. Network optimization models and interaction algorithms are integrated to evolve the production network through synchronous machine-level and network-level reconfiguration driven by data.     

Determination of forces in high speed blanking using FEM and experiments

The increasing demand for micro-formed and stamped parts such as connectors in the electronic industry is forcing manufacturers to push the speed limit of conventional press technologies to improve throughput. Designing dies/tooling for higher speeds and obtaining extended tool life requires a thorough understanding of the process. This paper discusses an experimental study of the interaction between punch, stripper plate and sheet material at various blanking velocities up to 1600 mm/s. The effect of velocity on punching force is also studied. A methodology to obtain high strain and strain rate dependent material flow stress data using blanking test and finite element modelling is presented.