For many liquid systems, excess foaming can be unwanted and challenging to defeat. In aqueous systems, raw material components and contaminants such as surfactants, proteins, carbohydrates, starches, fatty acids and particulate matter can form a stable foam in water. Many applications therefore utilise foam control agents to avoid foam problems and keep manufacturing processes running efficiently.

There are several types of foam control agents on the market. Historically they are categorized into defoamers and anti-foam agents. They include many different chemistries such as mineral oils, silicones, esters, biodiesel and polyalkylene glycols among others. 

In this article we will explain the difference between defoamers and anti-foam agents and explain how Shrieve’s PROGILINE® FI foam inhibitor products work and what makes them superior to alternative foam control agents.



A defoamer or an anti-foaming agent is a chemical additive that destroys foam already present or prevents foam from forming. This may be via simple mechanical destruction of the foam bubbles or by more sophisticated chemical interactions by the added agent. The chemistries of defoamers and anti-foam agents are often similar but have different applications and also may be utilised at different stages of the process.

An antifoam will prevent the formation of foam in a process and is best used to prevent and reduce air entrainment (bubbles in the body of the liquid). Antifoams are generally slightly soluble in foaming solutions, and they function by disruption of the foam bubbles walls by causing a decrease in surface tension which causes the bubble to burst. Defoamers will break and destroy foam created in a process, so are best used to eliminate a surface foam. They reduce surface tension and kill any foam on the surface, but they do not typically prevent the formation of a new foam. Defoamers are typically hydrophobic liquids which simply float on the surface of the water. 



Successful anti foam control depends on optimizing the balance between foam causing surfactants and foam destroying surfactants. Shrieve’s PROGILINE® FI Foam Inhibitors are specifically designed to function both as anti-foaming and defoaming agents. They give an optimum performance of both preventing new foam formation and existing eliminating foam, and they reduce the requirement to use several different types of products.

The mode of action of PROGILINE® FI polyalkylene glycol based foam inhibitor products is built on their chemistry, which consists of speciality copolymers of hydrophilic Ethylene Oxide and hydrophobic Propylene Oxide. PROGILINE® FI will act across gas/liquid interfaces (the bubble wall), due to their structures containing both these hydrophilic and hydrophobic portions. They are fully water soluble below the system operating temperature but are structurally designed to be water insoluble at the operational temperature, when acting across the gas/liquid interface.

PROGILINE® FI technology works by mimicking the surfactant molecules contained in the bubbles that make up the foam. When PROGILINE® FI is introduced into the system, its molecules line enters the bubble wall (lamella) and lines up with the naturally occurring surfactant molecules present within the bubble wall. Once it has entered the lamella, a “lens” is formed by the PROGILINE® FI on the lamella and begins to spread. This will destabilise the surfactant arrangement supporting the bubble and therefore weaken the bubble and cause it to rupture.

Products within the PROGILINE® FI range are designed to work over different temperature ranges via their structural design to ensure the correct aqueous correct cloud point for each application. Aqueous cloudpoint may be defined as the temperature at which the PROGILINE® FI becomes inversely soluble in water (ie. It is water soluble below its aqueous cloudpoint but water insoluble above the aqueous cloudpoint). PROGILINE® FI products all begin to function most effectively as a foam control agent approximately 5°C above their aqueous cloudpoint.

PROGILINE® FI products are also structurally designed to ensure closest possible mimicking of the natural surfactants present in a particular water-based application, this ensures efficient uptake of the PROGILINE® FI products into the bubble walls and hence result in optimised foam destruction.


A combination of the accurate structural design and aqueous cloudpoint hence ensures the products are highly application and temperature specific, thus allowing only nominal dosages to be utilised.



The PROGILINE® FI range of foam inhibitors are highly specific, active products that minimise dosage rates in their given application. PROGILINE® FI range provide 100% active products that require no dilution before stage dosing, thus simplifying the process and being ready to use as supplied. Shrieve offers tailored products for optimum performance across specific processing temperatures with both anti-foam and defoaming capabilities.

Using PROGILINE® FI will help to lower overall foam control adjuvant inventory and lead to a more simplified and efficient supply chain.


Written by: 

Heidi Lodge, Sales Manager, Shrieve Products International Ltd.