Category Archives: Elastomers

Freudenberg’s Molding Process

Seals and molded rubber technical parts are mostly given their form in closed molds. The rubber mixture is heated inside them so that vulcanization and solidification can take place. After a very precisely defined heating time, the degree of cross-linking reaches its maximum level. Then the mold can be opened and the component removed.

There are many different molding processes. The most important of them – and the ones most frequently used at Freudenberg Sealing Technologies (FST) – are listed here.

Compression Molding
Compression MoldingCompression molding is one of the oldest ways to manufacture technical elastomer components. First, a blank is manufactured that is large enough to fill out the form of the component being produced. It is inserted into the component mold in the tool (tool cavity). The component is given its form by closing the tool in the press. Due to the heat of the heating plate in the press, high pressure builds up inside the tool due to thermal expansion, and the vulcanization process is initiated.

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How it’s Made… Freudenberg Elastomers

Freudenberg Sealing Technologies has more than 1,500 elastomer mixtures, each created to suit a variety of different operating parameters.  But where does the raw material for your Silicone, Fluoro, or Perfluoroelastomer seal come from, and how does it start the process of becoming a seal?

Elastomers - Mixing 2Elastomers are multi-component systems that are composed of up to 15 different raw materials. Given their very different weight proportions and an extremely wide range of textures, the individual raw materials must be mixed together homogeneously. While rubber is delivered in ball or chip form and is only capable of flowing at the processing temperature, softeners are generally present in the form of flowable oils. The goal of mixing is to distribute all the required raw materials evenly within the polymer matrix and to break up agglomerates to allow the optimal bonding of the filler particles to the polymer. For the most part, the variety of different components cannot be incorporated in a single work step. This is particularly true for mixtures that contain fine soots or natural rubber as their polymer base.

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Introduction to Perfluoroelastomers – Part 2

Perfluoroelastomers: DownloadGallagher recently released our Introduction to Perfluoroelastomers White Paper, available for download on our site.  This was written by Russell Schnell, a current contracted employee of Gallagher Fluid Seals, and more importantly, a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont.  The following is the second excerpt from the White Paper, discussing the common industries in which perfluoroelastomer seals are used, and why.


Common Industries in Which Perfluoroelastomer Seals are Used and Why
In general, perfluoroelastomers are the most expensive elastomer seals specified in the marketplace; however they also provide the highest performance sealing service. As with any product, the selection of these products should be the result of a cost-benefit analysis.

Oil Processing Industry
Perfluoroelastomers - Oil ProcessingOne of the earliest uses of perfluoroelastomer seals was in the oil industry (down-hole).  Seals used in down-hole oil applications required resistance to high temperatures and aggressive chemicals. Sour oil and gas, resulting from H2S, often caused swift degradation of fluoroelastomer seals. The ability of perfluoroelastomer seals to resist H2S was a major reason for their selection and use. Over time, as wells became deeper and deeper, the application temperatures increased. As a result, in addition to aggressive chemicals, better high temperature resistance was needed and FFKM seals provided that benefit. Finally, seals used in these applications must have an “acceptable” service life. Oil wells are expected to last for many years and a seal failure, especially during initial exploration results in lost time and great expense when down-hole equipment must be retrieved to repair a seal. So the important points for this industry are resistance to aggressive chemicals, high temperatures, and reduced chance of seal failure which can result in tremendous expense.

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The Continuous Improvement of Elastomers: Part 2

The spectrum of elastomers range from very simple forms, like the natural rubber already in use in the 19th century, to modern, high performance elastomers from the second half of the 20th century.  They are continually being improved.

This blog article is the second in a two-part series discussing the many different elastomer materials available today, as discussed in Freudenberg’s The World of Freudenberg Sealing Technologies.
The first post discussed Natural Rubber (NR), Nitrile Rubber (NBR), and Hydrogenated Nitrile Rubber (HNBR).

Polyacrylate Rubber (ACM)
Elastomers - ACMACM elastomers are made of polar acrylic acids. As polar materials, they display good resistance to high-additive lubricating oils. Due to its saturated¹ main chain, the material exhibits good resistance to ozone, weather and heated air. Petroleum-based oils and fluids (for engines, transmissions and automatic transmissions) cannot harm them. But the material offers only moderate strength and low elasticity while displaying limited cold behavior.

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Introduction to Perfluoroelastomers – Part 1

Perfluoroelastomers: DownloadGallagher recently released our Introduction to Perfluoroelastomers White Paper, available for download on our site.  This was written by Russell Schnell, a current contracted employee of Gallagher Fluid Seals, and more importantly, a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont.  The following excerpt is the first section of the White Paper, discussing the history or elastomers and perfluoroelastomers, and the chemistry that helped create these modern materials.


Introduction to the World of Perfluoroelastomers
The use of elastomers is widespread in our world. Elastomers have many uses including: sealing fluids, for tires, in chemical plants, in semiconductor manufacturing equipment, for dust and moisture seals on cell phones, and seals on aircraft engines. The function of the elastomer and technology involved can vary from something as simple as a barrier to rain water, to seals in automobile engines, to critical sealing applications on the Space Station. Selection of the correct elastomer in an application is very important for successful and long term equipment operation. Although many different elastomers exist in the marketplace, when the highest service performance is needed, in terms of chemical and high temperature resistance, the choice is perfluoroelastomers.Perfluoroelastomer - Perfluoroelastomers

A perfluoroelastomer can be represented by the letters: FFKM or FFPM (ASTM and ISO designations, respectively). The word itself has two parts, perfluoro (meaning fully fluorinated), and elastomer.   Perfluoroelastomers exhibit many properties similar to PTFE (polytetrafluoroethylene), which is also fully fluorinated and considered inert to almost all solvents.  PTFE is often referred to as Teflon®, which is a registered trademark of The Chemours Company.  PTFE is a plastic, and when compressed, will not recover to its original shape. However, elastomers contain crosslinks, which act as springs to give the material resiliency and the ability to recover after a part has been compressed.  This resistance to permanent compression (compression set) gives the material the ability to maintain a seal over time. Finally, while whereas plastics are crystalline, elastomers are amorphous at room temperature; they can be easily compressed and will mold themselves to maintain a seal.  Given the chemical structure and performance similarities of FFKMs to PTFE, perfluoroelastomers are sometimes referred to as an elastomeric form of PTFE.

Continue reading Introduction to Perfluoroelastomers – Part 1

The Continuous Improvement of Elastomers

The spectrum of elastomers range from very simple forms, like the natural rubber already in use in the 19th century, to modern, high performance elastomers from the second half of the 20th century.  They are continually being improved.

This blog article will be the first in a two-part series discussing the many different elastomer materials available today, as discussed in Freudenberg’s The World of Freudenberg Sealing Technologies.

Natural Rubber (NR)
Elastomers - Natural Rubber (NR)In its original form, latex is greasy and sticky. Natural rubber is an elastic polymer, built on isoprene as its monomer. To make it usable technically, the long polyisoprene chains of natural rubber are cross-linked with one another through vulcanization – which involves the addition of sulfur under pressure and heat.

In the process, sulfur atoms insert themselves between the double bonds of adjacent chain molecules – the majority of the double bonds are maintained. The result is a three-dimensional molecule network whose parts can only shift against one another within certain limits.

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