Everything about Foam totally explained
The most general definition of
foam is a substance that's formed by trapping many gas
bubbles in a
liquid or
solid. It can also refer to anything that's analogous to such a phenomenon, such as
quantum foam. Often people mean
polyurethane foam (foam rubber),
Styrofoam or some other manufactured foam when they're using the term. It can be considered a type of
colloid.
From the early 20th century, various types of specially manufactured solid foams came into use. The low
density of these foams made them excellent as thermal
insulators and flotation devices, and their lightness and compressibility made them ideal as packing materials and stuffings. Some liquid foams, called
fire retardant foams, found use in extinguishing fires, especially
oil fires.
Foam, in this case meaning "bubbly liquid", is also produced as an often unwanted
by-product in the manufacture of various substances. For example, foam is a serious problem in the
chemical industry, especially for
biochemical processes. Many biological substances, for example
proteins, easily create foam on
agitation and/or
aeration. Foam is a problem because it alters the liquid flow and blocks oxygen transfer from air (therefore preventing microbial respiration in
fermentation processes). For this reason,
anti-foaming agent compounds, like
silicone oils, are added to prevent these problems.
If foaming is desired, a
foaming agent may help.
Foaming around the mouth can be a symptom of
rabies in animals. The term sea foam is used to describe the foam that forms on top of seawater from the action of waves. In some ways, leavened
bread is a foam, as the
yeast causes the bread to rise by producing tiny bubbles of gas in the dough.
Structure of foams
Real-life foams are typically disordered and have a variety of bubble sizes. The study of idealised foams is closely linked to the mathematical problems of
space-filling and
minimal surfaces. The
Weaire-Phelan structure is believed to be the best possible (optimal)
unit cell of a perfectly ordered foam, while
Plateau's laws describe how the soap-films form structures in foams.
Solid foams form an important class of lightweight cellular engineering materials. These foams can be classified into two types based on their pore structure. The first type of foams are called open cell structured foams. These foams contain pores that are connected to each other and form an interconnected network. The second type of foams don't have interconnected pores and are called closed cell foams. Normally the closed cell foams have higher compressive strength due to their structures. A special class of closed cell foams is known as
syntactic foam, which contains hollow particles embedded in a matrix material.
The closed cell structure foams have higher dimensional stability, low moisture absorption coefficient and higher strength compared to open cell structured foams. All types of foams are widely used as core material in
sandwich structured composite materials.
Also, in the case of alcoholic beverages; foam is beer.
Further Information
Get more info on 'Foam'.
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