Foam rubber, also referred to as rubber sponge, is formed during the manufacturing process through the transition of liquid rubber into solid sheet material. A foaming agent is released into the raw, liquid rubber, forming pockets of gas within the material itself. This cumulates into an air-filled matrix within the physical structure of the now-solid rubber. This entrapment of gas within the rubber’s composition allows the resulting material to be more compressible, a better insulator, and permits the absorption of energy so that it can be diffused within its cellular confines. All of these reasons allow both open cell rubber and closed cell rubber to excel in applications where solid sheet rubber would be inadvisable or ineffective. In addition, foam rubber maintains the resistances and tolerances attributed to other solid rubber sheets. It is resilient against the corrosive effects of ozone and oxidation, maintains a tolerance to a wide range of temperatures, and offers moderate chemical and oil resistance, making it ideal for a variety of general-purpose applications. However, not all foam rubber material is structurally similar. There are two distinguishing categories that differentiate between the varying constitutions of the two: open cell and closed cell.
Open cell rubber
This specific form of rubber sponge is the less dense and more porous of the two. It is defined by the interconnection of the gaseous pockets within the material. Open cell foam is especially permeable, which allows energy and matter to diffuse within the composition of the material while still maintaining the structural integrity of the foam rubber. This is excellent for many applications, such as sound absorption. When sonic waves hit and are absorbed within the material, the porous nature of open cell rubber allows the energy to become trapped and rebound within the interconnected pockets, eventually allowing that energy to disperse. This absorption ability, coupled with its comparatively low density and durometer, as well as the natural resistances the material maintains as a result of its foundation, allows the open cell variant of rubber to enjoy a wide spectrum of applicable uses.
Closed cell rubber
This form of rubber sponge is defined by the relative isolation of the gaseous pockets within the material. Due to this important structural difference, closed-cell foam rubber normally has higher compressive strengths and lower absorption rates. These traits give the rubber foam rubber material a greater structural potency when compared to its more porous open cell cousin. This is excellent for applications in which absorption is necessary yet it is still important for the material to maintain dimensional stability.
These foam rubber materials have been around since the 1930s. It was in the year 1930 that scientists from the chemical giant DuPont originally manufactured neoprene. It was, however, in a rudimentary form at the time. It took them several years to refine the material, but by 1937 the material that we know today as neoprene officially came to the market. The material has been popular in the following decades since its first arrival. Today, both the open and closed cell rubber variants are used for specific applications. Rubber sponge is used in applications ranging from laptop sleeves, aquatics, medical braces, electrical insulation, and general sheets and gaskets. The important thing is to know which type of foam you need.
Anyone interested in acquiring foam rubber for their application is well served to know this important distinction between open cell rubber and closed cell rubber. It is very important to differentiate between the two categories of foam so that your application has the right material. They will not perform in the same identical way, nor will they react in the same way to environmental stresses exerted upon it. When purchasing foam rubber, always know what you want the material to accomplish and apply that to your selection of material.