Effect Of Addition Mode Research Articles

Effects of addition mode on Zn–Co double metal cyanide catalyst for synthesis of oligo(propylene‐carbonate) diols

Zn–Co double metal cyanide (DMC) complexes are promising catalytic systems for copolymerization of epoxide and CO2. In the work reported, Zn–Co DMC catalysts were prepared by parallel‐flow dropping, forward dropping and reverse dropping methods, aiming to provide an insight into the effect of addition mode on catalyst structure and catalytic performance. Catalytic properties were evaluated using the copolymerization reaction of propylene oxide (PO) and CO2 in the presence of chain transfer agent. The results indicated that the factors that affect crystalline state are different for different modes. And excess zinc chloride is the prerequisite for organic ligands to be retained in the catalyst and affect the structure. In addition, a catalyst with flower‐like morphology was obtained with the parallel‐flow dropping method which provided larger surface area. An appropriate O/Zn value ensured abundant active PO which would suppress the backbiting process by forming consecutive PO units adjacent to CO2 units. Oligo(propylene‐carbonate) diols with average molecular weight of 1020 g mol−1, CO2 incorporation of 24.92% and WPC of 5.14 wt% were obtained at 80 °C and 2 MPa.

Effects of the addition mode and amount of organic montmorillonite in soft-core/hard-shell emulsion on fire protection, water resistance and stability of fire retardant coating

Abstract In order to meet the basic demands for everyday use and construction requirements, the organic montmorillonite/poly-(Methyl methacrylate-butyl acrylate)/poly-(Methyl methacrylate-butyl acrylate −methacrylic acid) soft-core/hard-shell emulsion was synthesized and used as the film former of the waterborne intumescent fire retardant coating. The effects of addition mode and amount of organic montmorillonite in emulsion on coating properties were studied. Emulsion stability analysis, water resistance tests of films and fire resistance tests all showed the optimum addition mode of OMMT was in the core layer of soft-core/hard-shell emulsion. The reason could be that the addition of OMMT in core layer could not destroy core-shell structure and cross-linked structure, and parallel-arranged OMMT was distributed well. The result of differential scanning calorimetry (DSC) showed that soft-core/hard-shell emulsion containing OMMT in core layer had lower glass transition temperature (Tg) of core layer and higher glass transition temperature (Tg) of shell layer, which play an important role in lowering film-forming temperature and enhancing resistance to water. The results of fire protection test indicated the fire resistance of coatings were significantly improved by adding OMMT in the range of 1.0 wt.% to 1.5 wt.% in core layer and scanning electron microscopy (SEM) demonstrated that the well-dispersed OMMT could improve the foam structure of char layer by limiting the escape of inert gases and filling carbon layer’s tiny cracks generated at high temperature.

Nonlinear dynamic response of rotating circular cylindrical shells with precession of vibrating shape—Part I: Numerical solution

Abstract The nonlinear dynamic response of a cantilever rotating circular cylindrical shell subjected to a harmonic excitation about one of the lowest natural frequency, corresponding to mode ( m =1, n =6),where m indicates the number of axial half-waves and n indicates the number of circumferential waves, is investigated by using numerical method in this paper. The factor of precession of vibrating shape ς is obtained, with damping accounted for. The equation of motion is derived by using the Donnell’s nonlinear shallow-shell theory, and is general in the sense that it includes damping, Coriolis force and large-amplitude shell motion effects. The problem is reduced to a system of ordinary differential equations by means of the Galerkin method. Three different mode expansions are studied for finding the proper one which is more contracted and accurate to investigate the principal mode (i.e., m= 1, n= 6) response. From the present investigation, it can be found that for principal mode resonant response, there are two traveling waves with different linear frequencies due to the effect of precession of vibrating shape of rotating circular cylindrical shells; the effects of additional modes n and k (multiples of frequency) on the principal mode resonant response are insignificant compared with an additional mode m , showing that it is better to adopt two neighboring axial modes to study the principal resonant response of the system.

Barium Sulphate Precipitation in a Double-Feed Semi-Batch Stirred Reactor

A study of barium sulphate precipitation in a double-feed, semi-batch mode was conducted. Experiments were carried out in a 10 l reactor stirred by a Rushton turbine. The effects of addition mode (feed together or apart), feed location (near the impeller or the surface), feed molar ratio [1:1, 15/1 (Ba in excess) or 1/15 (SO 4 in excess)] and stirrer speed on the precipitate characteristics were investigated. It was found that stirrer speed had only a limited effect. The most important parameter was the local, initial molar ratio of reactants, hence the local supersaturation, which also particularly depended on the overall feeding strategy. These initial conditions then had a controlling effect for the rest of the feeding period. The change in morphology, mean size and size distribution as a function of time in relation to feed strategy was also clearly observed. In general, small sizes were obtained when feeding the two streams close together with either component in stoichiometric excess.

Cycloaliphatic diepoxide crosslinkable core-shell latexes: the effect of addition mode

Cycloaliphatic diepoxide crosslinkable core-shell latexes: the effect of addition mode

Anionic synthesis of ω-dimethylamino-functionalized polymers by functionalization of polymeric organolithiums with 3-dimethylaminopropyl chloride

The functionalization reactions of polystyryllithium, polyisoprenyllithium and polybutadienyllithium in benzene with 3-dimethylaminopropyl chloride have been investigated in detail. The effects of addition mode (normal and inverse addition), added Lewis bases (THF and TMEDA), temperature and concentration have been investigated. The polymer products were analysed by SEC, 1 H and 13 C NMR spectroscopy and end-group titration. The pure ω-dimethylamino-functionalized polymers were quantitatively isolated by silica gel column chromatography. The functionalizations of polystyryllithium, polyisoprenyllithium and polybutadienyllithium by normal addition in benzene produce the corresponding w-dimethylamino-functionalized polymers in isolated yields of 67%, 85% and 90%, respectively. Functionalization efficiencies were improved by using the inverse addition procedure and by post-polymerization addition of Lewis bases before functionalization.