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AODD Pumps

Conquering the Challenges of Latex Emulsion–Handling

| Author / Editor: Ravi Prasad / Dominik Stephan

Wilden 1.5-inch bolted stainless steel AODD pump
Gallery: 3 Pictures
Wilden 1.5-inch bolted stainless steel AODD pump (Picture: Wilden and Pump Solutions Group)

Though latexes are very versatile and can be used to enhance a product’s performance characteristics, this article will identify and explain why one type of pumping technology— air-operated double -diaphragm, also known as AODD—is ideal for the demands of latex-handling.

Handling emulsions can be very challenging. Even their basic definition, “a mixture of two or more liquids that are normally unblendable”, hints at the difficulties that may be lying in wait when creating and handling it. Still, examples where emulsions have been successfully created, ranging from common milk to cutting fluids used in metal working, can be found everywhere.

Latex is a complex, but stable, emulsion consisting of polymer microparticles contained in an aqueous medium. Like emulsions in general, latex— the most recurring images of which is the latex glove—is present in all types of common products, from paints and balloons to floor polishes. Most latexes start out as simple emulsions in which droplets of the substance are added to water. This initiates a process known as ‘emulsion polymerization’ in which the final product can be called latex.

The Challenge of Pumping Latex

There are two basic challenges in pumping latexes: Latex emulsions are extremely shear-sensitive, meaning they require pumps that can reliably deliver a low shear rate and any contact with air will further polymerize the latex, making it imperative that the pump features a sealless design; pumps with mechanical seals also usually require flushing, which can create a possible leak path or dilution of the latex solution.

Other pump characteristics that are desirable when handling latex emulsions include: Dry-run capability; the ability to handle liquids with varying viscosities, from thin to high-grade viscosities; self-priming operation; portability and easy cleaning and maintenance.

Important Considerations When Looking for A Pump

A lesser consideration, but still an important one, is the climactic conditions in which the latex emulsion will be created and handled. Since most types of latexes are incapable of withstanding repeated freezing or thawing they need to be stored in temperatures above 40ºF (5ºC). They should also not be kept in temperatures above 100ºF (30ºC) for extended periods lest they become susceptible to surface drying that will compromise their performance.

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