Scale-up in emulsion polymerisation

The procedure for successful scale-up of batchwise emulsion polymerisation has been studied. The relevant literature on liquid-liquid dispersion on scale-up and on emulsion polymerisation has been crit1cally reviewed. Batchwise emulsion polymerisation of styrene in a specially built 3 litre, unbaffled, reactor confirmed that impeller speed had a direct effect on the latex particle size and on the reaction rate. This was noted to be more significant at low soap concentrations and the phenomenon was related to the depletion of micelle forming soap by soap adsorption onto the monomer emulsion surface. The scale-up procedure necessary to maintain constant monomer emulsion surface area in an unbaffled batch reactor was therefore investigated. Three geometrically similar 'vessels of 152, 229 and 305mm internal diameter, and a range of impeller speeds (190 to 960 r.p.m.) were employed. The droplet sizes were measured either through photomicroscopy or via a Coulter Counter. The power input to the impeller was also measured. A scale-up procedure was proposed based on the governing relationship between droplet diameter, impeller speed and impeller diameter. The relationships between impeller speed soap concentration, latex particle size and reaction rate were investigated in a series of polymerisations employing an amended commercial recipe for polystyrene. The particle size was determined via a light transmission technique. Two computer models, based on the Smith and Ewart approach but taking into account the adsorption/desorption of soap at the monomer surface, were successful 1n predicting the particle size and the progress of the reaction up to the end of stage II, i.e. to the end of the period of constant reaction rate.

Mathematical modelling in batch emulsion polymerization

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Exceptional function of nanoporous metal organic framework particles in emulsion stabilisation

A new concept of nanoporous metal organic framework particles stabilising emulsions was investigated. The copper benzenetricarboxylate MOF particles adsorbed at the oil/water interface play an exceptional role in stabilising both oil-in-water and water-in-oil emulsions. © 2013 The Royal Society of Chemistry.

An investigation into the formation of wax emulsion

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Nanostructured Cu/Nb multilayers subjected to helium ion-irradiation

Helium ion-irradiation experiments have been performed in single layer Cu films, Nb films and Cu/Nb multilayer films with layer thickness varying from 2.5 nm to 100 nm each layer. Peak helium concentration approaches a few atomic percent with 6-9 displacement-per-atom in Cu and Nb. He bubbles were observed in single layer Cu and Nb films, as well as in Cu 100 nm/Nb 100 nm multilayers with helium bubbles aligned along layer interfaces. Helium bubbles are not resolved via transmission electron microscopy in Cu 2.5 nm/Nb 2.5 nm multilayers. These studies indicate that layer interface may play an important role in annihilating ion-irradiation induced defects such as vacancies and interstitials and have implications in improving the radiation tolerance of metallic materials using nanostructured multilayers. © 2007 Elsevier B.V. All rights reserved.

Strengthening mechanisms in nanostructured copper/304 stainless steel multilayers

Nanostructured Cu/304 stainless steel (SS) multilayers were prepared by magnetron sputtering. 304SS has a face-centered-cubic (fcc) structure in bulk. However, in the Cu/304SS multilayers, the 304SS layers exhibit the fcc structure for layer thickness of =5 nm in epitaxy with the neighboring fcc Cu. For 304SS layer thickness larger than 5 nm, body-centered-cubic (bcc) 304SS grains grow on top of the initial 5 nm fcc SS with the Kurdjumov-Sachs orientation relationship between bcc and fcc SS grains. The maximum hardness of Cu/304SS multilayers is about 5.5 GPa (factor of two enhancement compared to rule-of-mixtures hardness) at a layer thickness of 5 nm. Below 5 nm, hardness decreases with decreasing layer thickness. The peak hardness of fcc/fcc Cu/304SS multilayer is greater than that of Cu/Ni, even though the lattice-parameter mismatch between Cu and Ni is five times greater than that between Cu and 304SS. This result may primarily be attributed to the higher interface barrier stress for single-dislocation transmission across the {111} twinned interfaces in Cu/304SS as compared to the {100} interfaces in Cu/Ni.

Synthetic strategies to nanostructured photocatalysts for CO2 reduction to solar fuels and chemicals

Artificial photosynthesis represents one of the great scientific challenges of the 21st century, offering the possibility of clean energy through water photolysis and renewable chemicals through CO2 utilisation as a sustainable feedstock. Catalysis will undoubtedly play a key role in delivering technologies able to meet these goals, mediating solar energy via excited generate charge carriers to selectively activate molecular bonds under ambient conditions. This review describes recent synthetic approaches adopted to engineer nanostructured photocatalytic materials for efficient light harnessing, charge separation and the photoreduction of CO2 to higher hydrocarbons such as methane, methanol and even olefins.