How Are Elastomers Manufactured?

Elastomers are used in a variety of industries due to their elasticity, durability and high-resistance properties. At TRP Polymer Solutions, we use elastomers in the production of many of our custom rubber mouldings. In this guide, you can find out how our rubber products are made from start to finish. We include in-depth information about all stages of elastomer production, including manufacturing, mixing, preparing and moulding. So, read on to find out more.

How elastomers are manufactured

The elastomer manufacturing process involves combining the raw ingredients of the elastomer and processing it in a variety of methods to achieve the final polymer. Step by step, this is how elastomers are manufactured:

To produce elastomers, the raw materials are first boiled to remove residual water and purify them.
The purified materials are then combined and mixed with a catalyst. This triggers a reaction that alters the chemistry to produce a polymer. The addition of another catalyst then stops the reaction at the right moment.
The polymer is now in liquid form.
Specific chemicals are then added to tailor the polymer for use, depending on what it is needed for.
A mechanised whisk then stirs additives into the mixture.
The polymer is then pumped into insulated storage tanks, where the ingredients are mixed further.
From this point, the mixture is then processed to be coagulated into crumbs.
The liquid elastomer, a solvent mixture and water are then pumped into a coagulation unit.
As the solvent is boiled off, the rubber coagulates into crumbs. The mix of water and rubber crumbs is then continually revolved while awaiting further processing.
This mix is pumped into a rotary sieve, which drains off the water as it spins. Afterwards, some water is added to cool the crumbs.
The elastomer and water mix is transferred onto a conveyor and dried, functioning as a vibrating sieve.
Infrared light (FTIR) is then used to analyse the microstructure of a sample. If it’s acceptable, production continues.
A screw-like mechanism presses the wet rubber crumbs against a metal plate to squeeze out more moisture.
Another vibrating conveyor further drains off water. A vibrating spiral conveyor and the addition of hot air then help to further dry the polymer.
With a small amount of moisture, the crumbs are processed through a baler machine, which makes the polymer into large bales through pressure.
After inspection, they are then packaged to be shipped and processed into many different types of products.

Mixing

A base polymer can be combined with other ingredients to create stronger and more resistant materials through the process of mixing:

First, the polymer is placed in an open mixing mill.
So the batch doesn’t get too hot, cooling water is used within the machine’s rollers.
Process aids can be added early to eliminate the potential for sticking.
A few in-cuts are made throughout the process to ensure the ingredients are evenly distributed.
Once all the added ingredients are combined, the batch is picked off and processed through the mill again on the tightest setting to ensure the mix is homogenous and well-dispersed.
The mix is finally sheeted off for cooling.

Preparing

Before being moulded, elastomers are usually altered so that the moulding process is free of potential flaws. Firstly, the elastomer is forced through a die to form it into the necessary dimensions, known as preform extrusion. This can then be followed by several additional methods of preparation, such as blanking. At TRP blanks can be cut by hand for high specification products, or can be automatically cut by machine. For specific applications a preform tool can be used or the rubber can be punched to size.
After the elastomer undergoes the preparation stage, the elastomer can then be moulded.

Moulding

There are three common ways that elastomers can be moulded to be finalised into a final product. Each method presents different benefits and is selected on the basis of what the end product is needed for. The types of moulding for elastomers include:

Compression

Compression moulding is a highly efficient method of moulding. It is done by first placing the uncured elastomer material into a preheated mould. Through pressure, the elastomer then conforms to the shape of the mould. This method is suitable for simple and relatively complex parts alike. Compression moulding offers the advantage of low tooling cost and low manual labour requirement. Because the tools have shorter set up times TRP are able to change compression moulds multiple times in a shift, making orders of below 10 O-Rings convenient and cost effective.

Transfer

Transfer moulding is a similar process to compression moulding. The elastomer is placed into a pot, when the tool closes the rubber is pushed through gates and transfer holes to fill the cavity. Transfer moulding is typically used for rubber to substrate bonded components or moulds that have multiple cavities. Whilst in some cases it can offer the advantage of increased production it’s usually a more expensive option than compression moulding. For certain components witness lines can also be generated which may be undesirable in dynamic applications or may provide initiation points for tearing.

Injection

Injection moulding is a very common method of moulding due to its precision and speed. The elastomer is first heated in a prewarming chamber. The elastomer is then forced into a mould by screw or piston at a high shear rate into a mould to be shaped into the desired format. Whilst injection moulds are highly productive, they are expensive and can use a complicated system of runners. For valuable materials such as FKM and FFKM the scrap generated by the runner system can make this process uncompetitive. Unlike plastic injection moulding, runners cannot simply be reprocessed back into the material.

Elastomer products at TRP Polymer

We hope this guide has provided you with valuable insight into how elastomers are manufactured. Through the above processes, we at TRP Polymer Solutions are able to make custom-moulded rubber seals, FFKM ‘O’-rings and seals, and a wide variety of custom-moulded rubber solutions specifically for your business’ unique requirements.

For more information on our products and how TRP can assist your business, please contact us. Our technical team is ready to provide expert advice and solutions tailored to your needs.

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