Rubber extrusion is a process through which rubber, a natural elastomer, is shaped into products that can be used for a myriad of applications. Since the 19th century, many industries have been using rubber in the manufacture of different products. Rubber Extrusion has remained to be one of the most preferred methods of processing rubber. Different processing methods have since been developed but have slowly disappeared due to inefficiencies like high cost.
How It Happens
Among the two most prominent parts of a rubber extruder machine is the heated shearing screw conveyor and shaping die in which pressurization is squeezed. For the process to occur, raw rubber is fed into the screw, and it gets pushed and heated in the conveyor simultaneously. The stock is then sent to the conveyor from the hopper, where it is softened through shearing and heating. The screw’s rotation also acts as a pressurizer for the stock rubber. When the rubber gets softened enough, it is pushed through an opening in the die where it obtains its shape. After getting shaped, the new profile shape emerges on the other side of the extruder.
After rubber profile processing, the rubber gets passed through other post-processing procedures known as secondary processing. Such processes include dusting, which is applying powder to prevent the rubber from adhering to other materials and the compulsory vulcanization. During vulcanization, the rubber is cured with curative compounds like Sulphur to strengthen the extruded rubber. Other optional secondary processes may include drilling, cutting, splicing, and coiling.
Choice of Stock Rubber Used
The type of raw rubber used plays an important role in determining the properties of individual finished rubber products. Through raw material selection, manufacturers can further develop their product and take advantage of the many natural rubber forms available. Some of the commonly used raw rubber forms include;
- Silicone Rubber— is a chemically inert and FDA certified elastomer. It is non-reactive owing to its inert properties. It is a popular choice in healthcare and foodservice because of its superior qualities.
- Gum Rubber— commonly known as natural rubber. It is also a popular choice owing to its abrasion and acid resistance.
- Nitrile— is an oil-resistant form of rubber that is popularly used in making rubber surfaces that will contact oil.
- EPDM— ethylene propylene diene terpolymer is used in many applications such as door gaskets and tarp strips due to its resistance to many potential damages. This form of rubber is resistant to oxidation, heat, and aging.
- Viton— is also applicable in food services due to its superior qualities of resistance.
Advantages of Rubber Extrusion
Benefits accrued from processing rubber through extrusion are numerous. A wide variety of products can be derived from the process. Through this process, the extruded rubber is not limited in shape or length and can be cut to fit any application. The process is highly efficient and repeatable. By comparison, rubber moldings are highly limited in applications due to the size of the manufacturing press used. Rubber sheets are, on the other hand, unlimited in size or length but harbor major compromises on tolerance.
Unlike molding tools, extruding machinery is relatively cheaper and is hence ideal for cost-effective productions. An extruder is also proficient in maintaining greater accuracy, unlike the stripped products. Color matching materials such as silicone can be used in cases where an aesthetic finish is required. The extrusion process is also more advantageous in that a wider range of materials can be used in production.
Common Extruded Rubber Products
Unlike the many other rubber processing methods used, there is a wide variety of products that can be developed from extruded rubber. Some of the commonly used products include;
- Windows, cabinets and door seals
- Mandrel formed hoses
- Vibration reducers
- Pressure switch square tubing
- Mass transit window seals
Despite having some minor disadvantages like limitations in the level of product hardness that can be achieved, the rubber extrusion process remains to be the most superior rubber processing method.