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Biocolloids

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Foam Generation and Stability

Foam Generation and Stability

A foam is a colloidal dispersion in which a gas is dispersed in a continuous liquid phase. Many examples of foams in industry and everyday life can be found easily such as shampoo, bubble bath, dishwater detergent, cleaner, laundry, coffee, beer, beverages, soda, mining process, oil recovery, environment remedy, and so on. Solid foams, dispersions of gas in a solid, are not covered in this statement.

Do you like or hate foams?  For some refiners, in which the through-flow of gas at high temperature, pressure is required to crack hydrocarbons, the gas-liquid mixtures will foam strongly. The foam traps gas with gas fractions of 80% or higher.  Clearly in such situations, in which it is desired that solid catalysts contact liquids, the production of foam is not wanted. On the other hand, there are applications where foams are useful.  For example foams can have a high stress yield  and can be used in a fluid for carrying particles in applications ranging from the transport of cuttings in drilling, to the placement of sands in cracks in oil producing reservoirs, to increasing the conductivity of reservoirs for secondary oil recovery. Obviously, bubble bath and shampoo companies should like to produce appropriate foams for dish and hair washing.  Therefore, technologies which are impacted by foams and foaming are widespread.  And you have to deal with them.

Realistically, foams are not well understood and they are very hard to control.  A foam cannot be created without the vigorous introduction of gas from a bubbly mixture. To understand foaming it is necessary to try to be precise about the critical values of bubble release required to make and maintain a foam.  All liquid/gas foams are unstable, and some are more unstable than others.  The stability of foams is another subject in which our understanding is far from complete. Foams collapse by draining and film rupture. To keep a foam from collapsing it is necessary to oppose the draining by surface tension gradients induced by surfactants.  Therefore, the selection of surfactant through an effective foam testing to design an appealing formulation for the market is critical.

SITA R2000 and its versatile functional modules can help you understand all these important topics with a foam Its fully automated features enable you to measure the foam’s ease of generation, stability, drainage, density, and many other foam properties.  An interfacial rheology device, OCA25+ODG25 and bubble tensiometer SITA T100 will help you identify key factors which play important roles in determining the effectiveness of your formulations.  Speak to our experienced scientists to start making changes for your business.

Coatings and Adhesives

Coatings and Adhesives

In coating and adhesion/bonding operations, it is vital that the adhesive and paint are applied in the correct locations and spread over properly treated surfaces to achieve needed coverage and bond. Poor formulations and incorrectly applied adhesive/paint can weaken the bond and undermine the coating effect.  Hardening of the adhesive( the so called shark skin of the coating) can be done through cooling, drying or curing reactions, prior to bonding and surface formation; overspreading or over-absorption into permeable materials can weaken the subsequent joint and adhesion. The techniques for characterizing the properties of surfaces and formulations that influence the interactions between the substrate and adhesive/coating during the bonding and surface finishing processes are critical. These methods include  substrate wettability and surface energy, surface absorbency, surface receptivity and modification, application and spreading monitoring.  Good wettability of a surface is a prerequisite for ensuring good adhesive bonding and surface finishing. In the meantime, some important issues need to be focused on developing a better formulation for a liquid adhesives and coating include: enhancing dispersion – maximizing pigment coverage; increasing solubility – increasing component loading; and reducing viscosity –  reducing mixing requirements, enhancing flow-ability and wetting.

The team of FDS/SITA/Dataphysics can help you with our years of application experiences not only in surface treatment and verification, but also the dynamic processes of applying your adhesives and coatings to any surface.  

Our devices which can help you are: OCAs, DCATs, DCAT-LBE, ODG, RN4.2, LK2.2, T100, T15Plus, etc.