From Wikipedia, the free encyclopedia The most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. It can also refer to anything that is analogous to such a phenomenon, such as quantum foam. Often people mean polyurethane foam (foam rubber), Styrofoam or some other manufactured foam when they are 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.
STRUCTURE OF FOAMS
From Wikipedia, the free encyclopedia Real-life foams are typically disordered and have a variety of bubble sizes. The study of idealized 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 do not 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.