Rubber is a naturally occurring elastomer, cultivated from the Pará Rubber Tree. Researchers believe that the cultivation of rubber has been taking place since prehistory; they estimate that Mayans were sapping rubber trees and boiling natural latex to make crude oil as early as 1600 B.C.E. The process of rubber extrusion as we know it today, by which natural and synthetic rubber materials are modified and shaped into products, did not begin to develop until the 19th century. In the modern world, extruded rubber occupies a position of importance, serving innumerable consumer, commercial and industrial applications.
The properties of an individual finished product depend on the raw rubber stock used to make it, the extrusion process it underwent and any secondary processes. Since rubber exists in many unique forms, manufacturers are able further develop their products through raw material selection. For example, natural rubber, which is also called gum rubber, is sought after for its qualities of excellent acid and abrasion resistance.
Synthetic rubbers like silicone and viton, on the other hand, are frequently selected for applications in the healthcare and foodservice industries for their qualities of superior heat, chemical and weathering resistance. Another synthetic rubber, nitrile, is resistant to oils, while neoprene resists heat and butyl has low air flow permeability. In general, rubber extrusions are valued as sealants and gaskets because they offer such excellent flexibility, impermeability and resilience. Read More…
A standard rubber extruder, also called a screw extruding machine, consists of two main parts: 1) a heated shearing screw conveyor and 2) a die. A shearing screw conveyor is made up of a conveyor and a screw. The screw, which sits parallel to the conveyor, pushes rubber material onto the conveyor channel, where it is heated, pressurized and plasticized. A die is pre-designed chamber that serves as a shaping tool. Newly pressurized and plasticized rubber material is squeezed through it to created a shape. The material is pressured by the conveyor screw to squeeze through the die, located at the end of the conveyor, from which the new shape will emerge. Only once a rubber shape has cooled is it considered “extruded.” Note that a die can be made into nearly shape and so, rubber can be extruded into nearly anything, no matter the shape or size requirements.
Variations on standard rubber extrusion are often related to the type of rubber being extruded. For example, to process silicone, manufacturers must modify their rubber extruder temperature output to compensate for silicone’s heat-resistant characteristics. Also, in order to undergo extrusion, natural rubber stock must first be divided into pellets. Some types of extrusion are not based specifically on a rubber material. Another type of rubber extrusion, cold feed extrusion, for instance, involves extruding rubber without pre-heating it. While not designed for one specific material, cold feed extrusion is well-suited to the production of hoses, cable, sheaths and profiles. Hot feed extrusion is the opposite process, in which rubber material is heated prior to extrusion.
Co-extrusion is a variation on basic extrusion that allows for the creation of extruded rubber parts that contain the properties of more than one rubber material. Co-extrusion works when two separate extruders and two or more separate batches of mixing rubber material are connected to a single die. They separate batches of rubber are fed into the die at the same time, allowing for their convergence. While extruded rubbers can be used as in after they have cooled, they may also undergo secondary treatments to improve them in some way. Vulcanization is a popular method of strengthening extruded rubber; it is the process of curing extruded rubber with sulphur or other curative compounds. Another treatment extruded rubber may receive is dusting, when powder is applied to rubber to prevent it from adhering to something else.
Because rubber extrusion allows for high levels of customizability and yields products with superior uniformity and strength, it is the preferred rubber processing method of most manufacturers. Rubber extruders make shapes and products that are invaluable in everyday home life, such as rubber trim, weatherstripping, extruded rubber seals, rubber floor matting, rubber grommets, connectors, bumpers and more. They even make up the eraser on the end of a pencil. Outside of the home, extruded rubber is used in cars, on bicycles, on space shuttles and on submarines. In warehouses and manufacturing facilities, rubber rollers, sheets and rods absorb the noise and vibration caused by moving machinery.