Rubber is used in the production of lots of products. These products are produced with a bunch of production methods that we will describe here. Rubber products that you are seeing around you are probably produced by one of these processes.
There are a bunch of rubber shaping processes available in the industry. Let’s explain these types of rubber shaping processes.
Calendering is a process that gives required thicknesses to rubber materials by passing them through a set of rolls. The distance between rolls defines the thickness of rubber to be calendered. This method is also applied to thermoplastics, but the application temperatures of much lower than thermoplastics, for rubbers.
Lower application temperatures are used because of the cross-linking occurrence after a specific temperature. This premature cross-linking is not desired in the shaping process.
Like thermoplastics, swelling occurs after the rolls. So, swelling effects must be considered in the calendering process design for rubbers.
Extruded rubber profiles(Image Source: therubbercompany.com).
The extrusion of rubbers is nearly the same as the extrusion of thermoplastics. The main difference between rubber extrusion and thermoplastic extrusion processes is the barrel length.
Barrel lengths for rubber extrusion machines are much lower than thermoplastic extrusion. This is because of preventing the premature cross-linking occurrence in rubber molecules which is not desired thing.
Swelling is also a problem after exiting from extrusion machine die. This must be considered in the design stage.
Rubber molding application is slightly the same as thermoplastic injection molding processes. There are a barrel and screw mechanism that pushes the rubber material inside molds. Like the other processes, there is a risk of premature cross-linking occurrence in molds.
There is another kind of rubber molding process which is called compression molding. The importance and difference of this process is the cross-linking formation inside the mold. Transfer molding is also used.
Mold expenses are one of the biggest downsides of rubber molding processes. But if the serial production manner of high-quality parts is adopted, it can be profitable.
Gaskets, seals, shoe insoles, bottle stops, and parts like that from rubber are produced with rubber molding processes generally.
Rubber coating processes comprise several methods to impregnate or coat the other materials or parts with rubbers to produce composite parts or products.
Calendering operations are used also in rubber coating and impregnating operations.
Skimming is a type of rubber coating process that fabrics made from other materials are fed from spool to rubber solution. And this rubber and fabric coating passed through heat chambers to take the solvent from rubber, then obtain cross-linkings. The excessive rubber coating is skimmed with special doctor blades.
Spraying is another process that materials are coated with rubber spray. This is simple like that.
In the dip casting or dipping method, a type of negative mold is dipped inside a rubber bath. And it’s dried with cross-linking on that mold. This sequence can be repeated to obtain the desired thickness. With this method, hand gloves can be produced.
As you understand that, cross-linking formation is a very important parameter for each rubber shaping process. Process parameters change according to this cross-linking phenomenon of rubber material.
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