Natural rubber is derived from natural latex and synthetic rubber comes from processed petrochemicals; the term gum rubber refers the naturally derived version. Gum rubber tubing can range in outer diameter, inner diameter and wall thickness. It is usually tan or white in color; colorants may be added, though this interferes with the purity of the rubber.
Gum rubber tubing has excellent tensile strength as well as being tear resistant and resilient. It retains its flexibility at low temperatures, making it weather and ozone resistant, and it has superior shape memory. Gum rubber tubing is used in many industries for a variety of applications including dry bulk food processing in addition to pharmaceutical, chemical, hydraulic, pneumatic and specialty applications.
It is also widely used in laboratories and medical environments because it permits unrestricted flow of water, gases, chemicals and acids at low pressure. It has a tight seal when connected correctly to push-on fittings, hose barbs and glass tubing. Gum rubber tubing may also be used in vacuum assemblies when the wall thickness is at least half the internal diameter.
Gum rubber is made from natural latex. The collected natural latex is taken to a processing plant and mixed with chemicals so it thickens. In synthetic rubber, certain additives can influence the attributes of the final product. For example, some rubber tubing is conductive while other tubing is sterile and inert. Neoprene, silicone and Viton are a few examples of materials that have different characteristics while still being classified as rubber tubing. For instance, neoprene is buoyant, silicone is very smooth and elastic and Viton tubing is highly resilient. After mixing, the rubber must be given its shape.
There are three main ways this is done: molding, extrusion and dipping. Liquid rubber can be poured into molds and pressed into place; the two halves will later be attached and smoothed together. Rubber tube extrusion involves taking raw rubber materials and forcing them through an extrusion die. Dipping rubber tubes involves long cylinders called mandrels whose thickness is the width of the desired internal diameter. They are dipped into vats of rubber and then dried and steam cured. For a textured non-slip exterior, gum rubber tubing may be wrapped in cloth.