Rubber extrusion is the process by which natural and synthetic rubber materials are strengthened and shaped into useful products. Rubber is an elastic hydrocarbon polymer (or elastomer) and is found naturally in the Pará Rubber Tree. The origin of human cultivation of rubber trees predates history; the Mayans are believed to have sapped rubber trees of their natural latex and boiled it to make crude rubber around 1600 B.C.E. It wasn't until the 19th century that more advanced methods of processing were adopted on a substantial scale.
Since the 19th century, natural and synthetic rubber products have come to be employed in countless industrial, commercial, and consumer contexts. Although different rubber processing methods exist, extruded rubber remains a popular choice for many manufacturers because of its strength, uniformity and customizability. Rubber extruders can form extruded shapes of any size; the modularity of this manufacturing method opened the door to a long list of industrial products that are now indispensable. Weatherstripping, rubber trim and extruded rubber seals have become essential for effective climate and moisture control. Rubber sheeting enjoys an almost universal presence in the entrance to many homes and businesses as textured floor matting. Rubber bumpers, bushings, grommets and connectors all contribute to effective, efficient and safe workplaces, vehicles and homes. For every other context in which a rubber product is needed, rubber extruders can produce custom rubber profiles to meet unusual or unique needs.
Extruded rubber performs under most conceivable circumstances; from space shuttles to submarines and from cars to bicycles, rubber extrusions connect tubing, insulate electronics and erase mistakes on paper. In homes, rubber trim can be found lining baseboards, protecting paint and wallpaper from damage. Rubber mats can be placed under rugs to protect hard floor surfaces and prevent injury from slipping. Rubber grommets line the openings in sheet-metal power strips, protecting the cords from wear and the consumer from the risk of shock. Rubber sealants keep bathroom fixtures watertight and kitchens water-efficient. Weatherstripping has become increasingly important for commercial and residential builders with an interest in maintaining energy-efficiency. In industrial contexts, rubber rods, rollers and sheets absorb vibration and noise from machinery with moving parts. Rubber bushings make vehicle suspension systems effective, and rubber bumpers protect freight trucks and loading docks. A rubber extruder's production is limited only by its designer's creativity; as long as an extruder has a hopper, conveyance channel, a die and the raw material, it can make almost any shape.
During the rubber extrusion process, raw rubber material (or stock) is processed through a screw extruding machine. A rubber extruder is made up of two main parts: a heated shearing screw conveyor and a die through which the plasticized and pressurized rubber is squeezed. A shearing screw conveyor is as its name suggests: a conveyor and a screw. The screw is positioned parallel to the conveyor. As the screw turns, it pushes the plastic material while it becomes heated in the conveyor channel. A die is not at all like its ambiguous name suggests; it is the tool that will give the rubber its shape. In advance of the actual extrusion process, an engineer will design a die, either according to the specifications of his project or those of his customers (as is the case when custom extruded profiles are made), and install it in the extruder. The stock is deposited in a hopper, which is a container suspended above the conveyor. When the process begins, gravity sends the stock through the bottom of the hopper onto the conveyor (pre-heating of the stock is optional, depending on the precision of the die and the desired qualities of strength). It is softened through heating and shearing, and pressurized by the rotation of the screw. The pressure pushes the rubber through the die, which is located at the end of the extruder. The rubber then emerges from the extruder in a profile that matches the shape of die shape.
The qualities of the finished product will depend on the extrusion process and on the qualities of the raw rubber stock. Rubber exists in many forms, each with its own set of unique properties. Natural rubber, also called "gum rubber," has excellent abrasion and acid resistance, while synthetic rubbers such as silicone and viton have excellent heat resistance, chemical resistance and weathering. Silicone extrusions are particularly attractive to customers in the healthcare and food service industry because of their heat-resistance and chemical inertness. Neoprene also features good heat-resistance, nitrile rubber is resistant to oils and butyl has low air permeability and performs as an excellent sealant for that reason. Properties like tensile strength, hardness, aging, flexibility, permeability and speed of recovery from deflection will vary in different materials. Rubber extrusions often compete with plastic extrusions for some sealing and gasketing applications. Rubber extrusions are usually slightly more expensive than plastic extrusions, but rubber's qualities of resilience, flexibility and impermeability make rubber extrusions the obvious choice for most sealing applications.
Rubber Extrusions - Vicone High Performance Rubber Inc.
Rubber Extrusions - Vicone High Performance Rubber Inc.
Rubber Extrusions - Vicone High Performance Rubber Inc.
Rubber Extrusions - GSH Industries
Rubber Extrusions - Britech Industries
Rubber Extrusions - Britech Industries
Extrusions can be designed and prepared from a number of materials, such as rubber, thermoplastic rubber, and thermoplastics. The process of forming extruded rubber is different from that of molded rubber products. To put it simply, extrusions are parts that are prepared by forcing the material through a die of the desired shape, cut, or cross section, using a high-pressure extrusion machine. The size of the part depends on the type of profile or the client's application requirements.
The first stage of the extrusion process is feeding the unvulcanized rubber into the extruder machine. After that, the rubber is taken through the die with the help of a flute/base that is connected with a rotating screw. In this stage, the temperature and pressure on the material is increased, so that the material can contact well with the die. The pressure and temperature allow the rubber to the pass through the opening of die, which it swells and takes the shape. The forming of shapes depends on the compound nature and hardness of the material. This tendency encourages the extruded rubber parts manufacturers to have cross sections designed specifically according to the application.
Some of the most common extruded rubber products are extruded rubber seals, rubber bushings, gaskets, etc.
Extrusion dies are a purpose-built tool that have been designed by cutting a shape, which is exactly similar to the shape of extruded rubber demanded by the clients for their manufacturing needs.
Most of the time, extrusion dies are made from a hard metal, for example, steel, to have sharp edges. Once the mold or die has been created, the rubber is forced through it, applying high pressure in a high temperature zone. A rotating screw is used to put the pressure on the rubber to cross through the die. After the rubber is extruded and has passed through the die, it will most likely increase in size, which is further adjusted as needed.
Extrusion dies are formed according to the requirements of a business. The material, i.e. rubber, is also chosen depending on the precise specifications asked by the client or the customer.
Why Extruded Rubbers are Used?
Rubber is a versatile material, which has its own set of benefits. Extruded rubber products are an ultimate example of the resourcefulness of this material. Here in the following sections, some of the biggest reasons why extruded rubber is a preferred choice for industrial parts are described -
Effective Sealing: Rubber is a soft and flexible material. It makes an ideal choice for seals. Extruded rubber seals are used to create a strong and effective sealing in an unlimited number of industrial applications.
Customization: Rubber can be cut and shaped in any desired shape without applying much labor and effort. Whether for creating a shock resistance mechanism or a vacuum, low-pressure zone - rubber extrusion products are a suitable selection.
In addition to these, the firmness and flexibility of rubber can also be specifically designated considering the very need of the profile.
Extruded rubber products play an important role in a large number of industrial applications. Sometimes, they are used as a seal and many a times, for shock resistantance. Some of the most commonly used rubber products include rubber profiles, extruded rubber seals, rubber bushings, rubber trim, rubber channel, rubber tubes, etc. These are just the typical ones, there are many other rubber products that are demanded by manufacturing businesses and consumers and delivered by extruded rubber suppliers.
The quality of a rubber product is correlated to the renown and expertise of the supplier or manufacturer. The quality of your end products also depends on the quality of rubber supplied to you by your supplier. Here, the biggest question is, how to find the best extruded rubber supplier? The following subsections have some answers -
Locating the supplier
You can find many suppliers and companies that can meet your requirements, by performing a search on an Internet-based search engine. You will need to enter your desired keyword, which is extruded rubber, along with your city or region. However, this could be a little confusing, as you will get so many websites and links that will be irrelevant for your needs. There will be featured ads and spam links that will have nothing to do with your extruded rubber requirements. Some will have the products you are looking for, but not for your town. Following such links would result in waste of time.
However, if you really want to take help from your search results, then you can pick up four to five website links, review and compare their offerings, and speak to the ones that fit into your exact requirements. Then, if things go well, you can finalize the deal with them.
Finding a supplier via search engines is like shooting an arrow in the dark. You do not know about the reputation of the supplier. To circumvent getting into the trap of a notorious or unknown supplier, you can consider taking help from a directory.
Many high-traffic online business directories, like IQSdirectory.com, have lists of reliable and experienced companies, suppliers, and manufacturers that can provide you with the best quality extruded rubber. You can use such directory or listing services to locate a dependable supplier.
You just have to visit the site, enter your keywords, and there you will find a list of manufacturers and suppliers of extruded rubber products in your area. You can connect to a few companies and inquire about their products and prices. Compare the services and offers from three to four suppliers and finalize your deal.
Here are a couple points to have next to you when negotiating with a supplier -
Extruded rubber products, such as, rubber profiles, extruded rubber seals, rubber bushings, and rubber channels, play a major role in making equipment safe, since they are what that make our appliances weather proof. Other than this, different industries have different applications of extruded rubber, like in the automobile industry they are used in making bumpers, whereas the aerospace industry uses extruded rubber seals for connecting hoses.
Rubber extruding process
As the name implies, to give rubber a predefined shape, such as tire tread, v-rubber, hose, cable, strip, and seals, different types of rubber are extruded. The process starts with selecting a suitable rubber, including ethylene propylene diene terpolymer (EPDM), styrene-butadiene rubber (SBR), polyisoprene, neoprene, nitriles, and silicone. An external supplier provides the rubber in a form that complements the extrusion system.
The rubber then is fed into a rubber extruder, which works, more or less, like a plastic extruder. The machine has a screw assembly that compresses the rubber due to which the temperature rises; with the rising temperature and pressure, the feed breaks down, and then the rubber is forced through a die. The die, which is installed at the exit of the extruder, gives the final shape to the rubber.
The post-processing step called curing, also known as vulcanization, is what that gives rubber its physical properties, which makes it capable of withstanding challenging environments. As the shaped rubber exits the die, this process starts almost immediately. After the curing step, further post-processing steps involve splicing, taping end joining, coiling, drilling, and cutting.
Different polymers used for making extruded rubber products
EPDM (ethylene propylene diene terpolymer)
The extruded rubber products made with this polymer are resistant to outdoor environment. With the advent of this polymer, which now is most commonly used, extruded rubber products got ability to endure temperature in a range of +300 F to - 55 F. Whether is it door gaskets, weather stripping, window gaskets, roofing membrane, or tarp straps, all are made with EPDM.
SBR (styrene-butadiene rubber)
When extruded rubber products need high abrasion resistance, SBR is used. In automobile industry, SBR products, such as belt covers and motor mounts, are used extensively.
Polyisoprene, also known as synthetic natural rubber
Where flexibility is a factor, polyisoprene is used. This type of polymer also has mild resistance to abrasion.
The polymer is utilized for making extruded rubber products that will be exposed to oil. Hydraulic seals and hoses, as well as O rings are made with nitriles.
Neoprene is resistant to a number of things, including, exposure to water, oil, and ultraviolet rays. Moreover, the polymer has high-tensile strength and fire resistance. These properties make neoprene a preferred choice for many applications.
Recently, silicone products have become popular after getting certification from FDA for being non-reactive to a variety of things. It can endure high, as well as low temperature, ranging from - 100 F to + 450 F, without undergoing any change. Even biological fluids do not react with silicone, making a darling of beauty industry.
Many rubber products that we come across on the daily basis, such as rubber profiles, rubber seals, rubber bushings, rubber channels, rubber trim, rubber weather-stripping, and rubber tubing, are possible because of the advancements in the extrusion process.
The rubber extrusion process is similar to plastic extrusion, where a raw material, in the form of nuggets or kernels, is fed into a screwing column, which transforms the raw material into semi-fluid by a combined action of pressure and temperature, and then the material is passed through a die. The die gives a predefined shape to the raw material. The difference emerges after that, plastic extrusion has its own post-processing steps and rubber extrusion has its own.
When it comes to rubber extrusion, the physical properties that a finished rubber product will have are determined at the curing step.
Curing is commonly done by three methods:
Using a mold
In this method, a metal mold is used that is tooled to match the finished product shape and size. The raw feed of rubber is injected into the mold, and with the help of a press, heat and pressure is exerted on it for a predefined period. The next step is letting the mold cool down, and then the rubber product is removed from the die, which is ready for repeating the process. Evidently, the process takes time and tooling of the die plays a major role, however, the process is time tested and gives accurate results. This process is used for curing tires of various types.
Using an autoclave
The extruded rubber products are cured by this method. Once a pre-form product leaves a die, it is transferred to a metal rack holding other products, as well. Then the rack is put into an autoclave, a pressure chamber that works just like a pressure cooker but is a lot larger. The extruded products are exposed to elevated pressure and temperature. The pressure is high as 300 PSI, which removes the porous parts and adds structural strength. However, the method is slow, and at times, can be inaccurate. However, the reason of inaccuracies is not the method, but the time it takes for starting curing process. Though, the process is inexpensive and can cure a number of rubber products at once.
The other alternatives for curing work in conjunction with the extruding machine, thus, are called continuous curing. For this type of curing microwaves, hot air vulcanizes, salt bathes, oil, and glass beads are used. With the use of continuous curing method, extruded rubber products have high stress tolerance. It is a high-speed manufacturing process, which cuts cost in terms of labor, energy, and space.
However, the process has disadvantages too, including higher set up and raw material costs. Moreover, there are certain size and shapes that cannot be cured by this method. Inversely, there are some types of extruded rubber products that can only be cured by continuous process. For instance, closed cell expanded rubber.
Rubber Extrusion Types
- A substance that quickens the pace
of vulcanization and lowers the operating temperature required during
- Term for the bond between a rubber surface and a non-rubber surface.
a rubber product in the air instead of in a press or steam vulcanizer.
- Crevices that form on rubber surfaces due to exposure to environmental conditions, such as temperature extremes and precipitation.
- The amount of force the atmosphere exerts upon the earth's surface, measuring 14.7 psi at sea level.
- The development of a powdery residue on a rubber surface as a result of surface breakdown.
- Small cracks on the surface of rubber, usually from environmental damage.
- A measurement of a rubber material's return to its initial shape after deformation.
- Deformation on a rubber surface due to the application of stress.
- The incidence of swelling that occurs after the extruded profile comes out of the die. The rubber product's properties determine the amount of swelling that will occur.
- A change in a rubber material's hardness over time.
- An apparatus used for measuring the hardness of rubber.
- Applying powder to rubber to prevent adhesion to something else.
- A characteristic of rubber, describing its tendency to return to its initial shape after warping.
- A material capable of returning to its initial length after being stretched at room temperature to twice its original length.
- An increase in length after the application of stress. This occurs during stretching.
- A laboratory test that measures a rubber material's resistance to bending deformation.
- The resistance to
motion when different surfaces are in contact.
- Energy loss in the form of heat that results from the deformation of elastomeric material, caused by the application of stress.
- The softening of raw rubber by mechanical and atmospheric forces.
- The extent of a rubber material's ability to resume its original shape after deformation.
- The amount of stress required to create a certain amount of elongation.
- The point during vulcanization at which rubber material attains the intended properties.
- The degree to which rubber will retain deformation.
- Pounds per square inch. This measurement indicates pressure level.
- The comparison of the amount of energy needed to create an elastic deformation, and the amount of energy needed to recover from such a deformation.
- The maximum amount of stress that may be applied to rubber before breaking occurs.
- The process of increasing the strength and elasticity of rubber materials through the application of heat and pressure.