How are elastomers 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:
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 Linde Polymer 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 based on 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 costs and low manual labour requirements. Because the tools have shorter set-up times Linde Polymer can 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 a 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 Linde Polymer
We hope this guide has provided you with valuable insight into how elastomers are manufactured. Through the above processes, we at Linde Polymer can make custom-moulded rubber seals, FFKM O-rings and seals, and a wide variety of custom-moulded rubber solutions specifically for your business's unique requirements.
For more information on our products and how Linde Polymer can assist your business, please contact us. Our technical team is ready to provide expert advice and solutions tailored to your needs.
