Category Archives: Elastomers

elastomeric seals, Elastomers, Parker Hannifin Seals, PTFE

Sealing at Extreme Low Temperatures

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.

Original content can be found on Parker’s Website and was written by Nathan Wells, application engineer, Engineered Polymer Systems Division.

Heavy duty equipment moves industry forward in all climates, from the sunny Caribbean to icy Greenland. Effective, reliable sealing is what allows hydraulic systems in heavy duty equipment to do work, no matter the temperature. Reliable sealing solutions allow cylinders on dump trucks and excavators to move icy, frozen tundra, and allow actuators on subsea valves to operate 5,000 – 20,000 feet below the surface of the ocean. We depend on these seals for our safety and productivity, so a little chilly weather is no reason to call it quits.

What happens to seals at cold temperatures?

Most objects shrink as they get cold, with few exceptions, such as water. This applies to all matter in the universe. Materials shrink at different rates, and this is a measurable property called the Coefficient of Thermal Expansion (CoTE). Thermoset elastomers and thermoplastics shrink roughly 5 times more than metals for a given temperature change. This means at cold temperatures, seals shrink more than their housings, and thus have less “squeeze” to make a tight seal.

To make matters worse, elastomers also harden as the temperature drops. At some temperatures, known for each material as its Glass Transition Temperature (abbreviated ‘Tg’), seals become rock hard and brittle … like glass. We don’t make seals out of glass for a reason; they wouldn’t work. In order to keep seals springy and resilient, we need to specify materials with a Tg below the coldest temperature a system will see.

In very high pressure, low temperature applications, there is one additional concern. Applying pressure to seals effectively raises the Tg of the material by about +1°C per 750 PSI. This is called Pressure-Induced Glass Transition and is the reason high pressure seals fail slightly above their measured Tg. Continue reading Sealing at Extreme Low Temperatures →

Elastomers, Parker Hannifin Seals

What’s the Difference Between EPR and EPDM?

EPR vs EPDM – How do they differ?

What’s the difference between EPR and EPDM? What do the different abbreviations (EPR, EPM, EPDM, EPT, etc.) mean? These questions pop up from time to time in the seal industry, and here are basic answers to these questions.

EPDM MaterialsIn the range of ethylene-propylene (EP) rubber there are two lightly different branches: EPR (EP copolymer) and EPDM (EP terpolymer.) The differences are subtle, and a basic knowledge of polymers and rubber compounding is necessary to grasp the differences.

First of all, polymers (derived from the Greek for “many units”) are long  chemical chains that can be thought of as behaving like long pieces of cooked spaghetti. Each chain is made of one or more monomers (Greek “single unit”) linked together end-to-end. A copolymer (Greek “two units”) is composed of two monomers, while a terpolymer (Greek “three units”) is composed of three monomers. EPR (aka EPM, EP copolymer) contains only ethylene and propylene monomers. EPDM (aka EPT, EP terpolymer) is composed of ethylene, propylene, and a third monomer called a diene (three different dienes are in common use today, but discussing their differences gets extremely dry and technical.)

To make a rubber material rubbery, we essentially have to “glue” the polymer chains together. We do this through a process called vulcanization or curing. This is where the subtle difference between EPR and EPDM is found. Because of the chemistry of the polymer chain, EPR can only be vulcanized with a peroxide-based cure system. On EPDM, the additional diene monomer provides a specialized cure site that allows the polymer to be vulcanized with peroxide- or sulfur-based chemistries. Because of this added flexibility, most EP compounds in the seal industry today use EPDM terpolymer instead of EPR copolymer. In other industries (hose, roofing products, etc.) EPRs may still be the material of choice.

From a functional standpoint, there are very few performance differences between EPR and EPDM. Both swell dramatically in petroleum products, and both are excellent in water, steam, and polar solvents like MEK and acetone. There are some notable performance differences in extremely demanding applications: EPRs or very tightly cured EPDMs are suited for the nuclear industry (E0740-75 is recommend), and for applications involving concentrated acetic acid, some EPDM compounds (like E0692-75) show superior performance to most EPRs. In other applications, the performance difference is difficult (if not impossible) to identify.

The original article was written by our partners at Parker and can be found on their website here.

For more information about which material(s) might be the best fit for your specific application, contact Gallagher Fluid Seals’ engineering department.

elastomeric seals, Elastomers, Parker Hannifin Seals

What You Should Know About Electrically Conductive Elastomers

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.

Original content can be found on Parker’s Website and was written by Jarrod Cohen, marketing communications manager, Chomerics Divison.

Electrically conductive elastomers are elastomeric polymers filled with metal particles. They can be grouped by filler type and elastomer type. Then within each of these classes, there are standard materials and specialty materials.

Parker Chomerics manufacturers electrically conductive elastomers in gasket form, also known as EMI elastomer gaskets, under the CHO-SEAL brand. We won’t get so much into gasket configurations and dimensions here, we’ll just stick to classes of materials. So what is available? Let’s find out.

Conductive elastomers are metallic particle filled elastomeric polymers, the particles giving the shielding performance and the polymer making them “rubber.” There are many materials within this generic material type, but we’ll focus on the below.

Particle fillers

Setting up the grades of conductive elastomers by filler types involves six different particles:

picture of 6 essential fillers

Three types of elastomer material

  • Silicone
    A polymer that has a large temperature range especially on the low end down to -55F. It is a very soft material with a low compression set.
  • Fluorosilicone
    Close to silicone, but will not swell and degrade when exposed to solvents, fuels hydraulic fluids and other organic fluids. Although slightly harder than silicone, it is still relatively soft with low compression set properties.
  • Ethylene propylene diene monomer (EPDM)
    Does not have the temperature range nor the softness of silicone, but is resistant to highly chlorinated solvents used for compliance with NBC decontamination and is only used for applications with those needs.

All of these materials are cured or cross linked when the gasket is made. The cure either happens with heat or atmospheric moisture. Continue reading What You Should Know About Electrically Conductive Elastomers →

Elastomers, sealing technology

Coatings: Peroxide-Cured EPDM vs Sulfur-Cured EPDM

picture of EPDM sheet rubberEPDM is an M-Class synthetic rubber and is one of the most popular and versatile rubber compounds available. The main properties of EPDM are its outstanding heat, ozone, and weather resistance. EPDM rubber has excellent electrical insulating properties and it has good resistance to steam, ketones, ordinary diluted acids, and alkalies.

During the manufacturing process of EPDM sheet rubber, the compound can be cured with either peroxide or sulfur. The choice of curing method is determined by the end-uses and applications which the compound will service.

Depending upon which curing method is chosen, there will be differences in the final properties and characteristics of the cured compound. Knowing these differences can be an important factor in selecting the right EPDM gasket material for servicing your specific application.

EPDM Sheet and Gaskets: Peroxide Curing

EPDM compounds cured with peroxide possess a superior chemical and thermal resistance compared to compounds cured with sulfur. Peroxide-cured EPDM can withstand temperatures up to 300°F (150°C) whereas sulfur cured EPDM can only resist temperatures up to 250°F (120°C). The extended temperature service range of peroxide-cured EPDM makes it a preferred choice for producing gaskets to service higher temperature applications.

In addition to extending the serviceable temperature range of EPDM compound, a peroxide cure also improves the heat stability, modulus, compression set, and aging resistance of the compound. Peroxide-cured EPDM also has less tendency to bloom and better preserves its colour during the curing process. Finally, peroxide curing of EPDM promotes co-polymerization of the compound with polymerizable plasticizers or agents designed to give controlled hardness and stiffness to the final product.

EPDM Sheet and Gaskets: Sulfur Curing

Sulfur-cured EPDM generally exhibits higher tear and tensile strength. These properties may be important in applications where higher strength and resistance to tearing are desired. The following table summarizes the essential differences between peroxide-cured and sulfur-cured EPDM sheet:

Peroxide-Cured EPDM

  • Good resistance to ageing
  • Higher temperature resistance
  • Lower compression set
  • Unlikely to bloom or discolour
  • Will not stain metals or PVC
  • Improved resistance to chemicals and oils

Sulfur-Cured EPDM

  • Higher tensile strength
  • Higher tear strength
  • Permits use of a wider range of fillers

The original article was written by staff at the Canada Rubber Group and can be found here.

Gallagher Fluid Seals is a stocking distributor of EPDM sheet rubber and other EPDM sealing solutions. For more information, please contact us today.

elastomeric seals, Elastomers, PTFE

Evolving from Plastic to Teflon Seals

The term “plastics” is generic way of describing a synthetic material made from a wide range of organic polymers. Organic polymers describes a man-made substance that is formulated using polymer chains to create what we commonly refer to as…(you guessed it), plastics.

Before plastic, leather had been used to create Backup ring devices behind O-rings. Leather allows fluids to be retained, providing lubrication for the O-ring when the system was running dry.

picture of teflonThe problem with leather was that it could become dry and shrink away from the sealing service, exposing the elastomer to same pressure it was intended to protect against.

With the advent of polymers, a piece of plastic could be cut or formed into the exact shape to allow for zero extrusion gap, and for continued protection for the O-ring.

Some polymers were very brittle. Since they needed to be deformed to allow for installation into solid glands, the cut of the plastic could nibble at the O-ring, causing premature failure of the element it was supposed to be protecting.

The Revolution of PTFE

When PTFE moved out of the lab and into industrial use, it quickly found itself adjacent to the O-ring. PTFE offers extrusion resistance and, at the same time, doesn’t erode or nibble at the O-ring due to the “softness” of the polymer.(Hardness between 55 and 65 Shore D)

Given the composition of PTFE, or Teflon, it could be utilized as a sealing element to protect Backup rings and conform to the shaft. The bonus was it was generally easy on shafts (depending on the filler added to the PTFE).

There are some negative aspects to Teflon that needed to be overcome by early engineers. First, it has a fairly high rate of Thermal expansion which, by its own nature, could often times lose contact with the sealing surface. This meant some kind of loading was necessary to ensure contact.

PTFE is as tough as other polymers, so the fact that it could seal on a shaft made it vulnerable during installation for tears or nicks on sealing surface.

Second, if it were stretched during installation, the material had to be sized back to its original shape due to its poor elastic properties. Continue reading Evolving from Plastic to Teflon Seals →

Elastomers, O-rings, sealing technology, Uncategorized

Metal Detectable & X-Ray Detectable Rubber Materials

Food, Beverage, and Pharmaceutical Regulations

picture of metal detectable o-ringStringent government regulations mandate that food, beverage, and pharmaceutical manufacturers keep foreign material out of ingredients to ensure food and drug safety for consumers. Preventing foreign material from entering the processing stream is of the utmost concern but there must also be measures in place to detect contaminated product and quarantine it before distribution.

Component parts that are used in food and drug processing equipment can become damaged by improper installation and/or excessive shear experienced during operation that causes fragments of rubber, plastic, and metal to contaminate ingredients. Chemicals used for cleaning and sterilization of equipment can cause rubber seals to degrade, increasing the probability of particles breaking off and entering the consumable products. Part failures causing product contamination can lead to machine down time, scrap product, product recalls and result in legal problems and negative media attention. All of which have a significant financial impact and can compromise brand loyalty within the market.

Hazard Analysis Critical Control Point (HACCP)

picture of precision metal detectable o-ringsMany processing operations now employ HACCP (Hazard Analysis Critical Control Point) programs which stipulate that all parts have to be metal detectable and X-ray detectable. This made it necessary to develop special rubber materials that would allow food processors to conduct routine inspections for this type of contamination utilizing in-line metal detectors and X-ray machines. Rubber must be compounded with special additives to make detection possible. However, certain foods have phase angles similar to metal detectable rubber so a complete understanding of the rubber product’s application is necessary for proper compound selection.

Metal Detectable O-Rings | X-Ray Detectable O-Rings

Precision Associates has developed four Metal and X-Ray detectable materials made with ingredients sanctioned under FDA Title 21 CFR 177.2600.

All four materials are 3A Sanitary 18-03 approved and are available in Silicone, Nitrile, EPDM, and FKM. Each is 70 durometer and blue in color. (The industry standard color is blue but materials can be colored for specific customer requirements and any polymer can be made metal detectable).

All compounds were tested by an independent laboratory and found to have magnetic properties that exceed industry standards.

picture of compound table precision o-rings

The original article was written by Precision Associates, Inc. and can be found here.

For more information about what Gallagher can offer through Precision Associates, or to talk to a technical sales expert about these materials, contact us today.

elastomeric seals, Elastomers, Freudenberg Sealing, sealing technology

Friction Reduction in the Seal

Wettablility of the Sealing Lip

The optimum function of rotary shaft seals depends on many factors. One of them is the “wettability” of the sealing lip. This parameter plays a particularly important role with synthetic lubricants such as polyglycol. If wetting is too low, not only does wear on the sealing lip increase, but the contact with the rotating shaft can also damage the shaft itself. The engineers at Freudenberg Sealing Technologies (FST) and Freudenberg Technology Innovation (FTI) have developed a new coating that forms a flexible bond with the elastomer of the seal and significantly improves wetting with synthetic lubricants.

Thanks to different materials and shapes, radial shaft seals for sealing rotating shafts can be used in a wide variety of industrial applications. What they all have in common is the demand for the lowest possible friction, low wear, and reliable sealing effect. Optimum lubrication of the entire tribological system depends on permanent wetting of the sealing lip.

This poses a particular challenge for poorly wetting lubricants based on polyglycol, which are used in drive technology, for example in worm gears. Too little wetting increases wear on the sealing lip and can also lead to increased shaft runout due to contact with the shaft, which ultimately necessitates replacement of the machine parts.

A flexible bond over a long service life

picture of friction reductionFST has developed the new 75 FKM 585 plus coating to achieve optimum lubrication in gears and pumps with synthetic lubricants. “We have succeeded in coating the sealing lip in such a way that polar oils distribute much better,” explains Dr. Matthias Adler from FST’s global materials development department in the Simmerring Industry division. “The mechanics of the layer have been modified so that it forms a flexible bond with the elastic material of the elastomer over a long service life – even under dynamic load. In addition, the coating is applied where no wear occurs.” The current development was specially designed for customers who already use the standard Simmerring 75 FKM 585 in drives for which the use of polyglycol oils is recommended by the manufacturers.

The elastomer is coated using plasma-assisted chemical vapor deposition (PE-CVD). In this process, the elements in the process gas form a chemical bond with the surface of the base body. The decisive criterion for the optimization of the wetting behavior is the targeted modification of the interaction between the coating and the synthetic lubricant. The measurements show that by using special components in the new surface coating such as carbon, oxygen and silicon in a certain molar ratio, optimal wetting can be achieved compared to the standard material 75 FKM 585.

New technology can be transferred to other materials

The layer thickness of 75 FKM 585 plus is a few hundred nanometers and its properties meet the standards of the manufacturers of industrial gear units with regard to oil/elastomer requirements. Although it is designed for particularly low wear at high revolutions, it has been shown that the coefficient of friction is significantly lower than that of the standard material, even at low speeds such as in the breakaway forces and mixed friction ranges. The newly developed technology is not limited to applications with FKM, adds Dr. Adler, “but can also be transferred to other materials. Initial tests on NBR and EPDM have also shown positive results in optimizing the interaction between coating and poorly wetting oils.”

The original article was published by Ulrike Reich, head of media relations & internal communications at FST.

Gallagher Fluid Seals is an authorized distributor of Freudenberg Sealing Technologies. For more information about how we can help with your specific application, please contact our engineering department.

Elastomers, Fluoroelastomers, Parker Hannifin Seals

Is an ASTM Callout the Best Way to Specify Your Elastomer Needs?

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.

Original content can be found on Parker’s Website and was written by Fred Fisher, Technical Sales Manager for Parker O-Ring & Engineered Seals Division.

ASTM Elastomer Compounds

elastomer materials pictureWhen looking at drawings to define a specific application or elastomer requirement: Is there value in using an ASTM elastomer compound description versus listing an approved Parker compound number?

Specifying a compound using the ASTM callout is a good start – it clearly defines what is wanted and it sets a minimum benchmark, which makes it easy for competitive vendors to understand what the need is. The ASTM standards also set specific test parameters which makes it much more simple to do an “apples to apples” comparison between two compounds. However, over time, here is what customers have learned:

Know Your Operating Requirements

1. The ASTM standards are very general; so when a customer defines a specific FKM they need using an ASTM callout, they might receive a compliant material that just barely meets the ASTM specifications, but did not meet the actual operating requirements. Because of that, a supplier may provide a customer with the lowest cost material. Let’s say the quality of the material is on the lower-end, but it meets the ASTM criteria requested. Because of that, the customer could see a 15% increase in assemblies requiring rework, plus a rising number of warranty claims due to seal failures. The twenty cents per seal that the customer saved for their $50 application would be offset by the cost of the increased product failures. And ultimately, this would result in an unhappy customer.

Know the Fluids Your Seals Will be Exposed to

fluid exposure2.  The ASTM standard does not specifically list what actual chemicals the seal has to be compatible with as well as the operating conditions. ASTM tests compatibility based on Standardized Testing Fluids, which are: Oils, Fuels, and Service Liquids. ASTM uses standard oils, which are defined by IRM 901 and 903. Again, the ASTM standards are excellent for comparing compounds, but most people do not have their seals operating in the ASTM reference oils and many sealing applications are exposed to multiple fluids.

Know What Your ASTM is Calling Out

3.  Most engineers or folks in purchasing who review or utilize older drawings have no idea why the original engineer chose the specific compound or why they used an ASTM callout.

So what is the best way to define and specify an elastomer? Most companies go through a technical process to specify, test. and confirm that an elastomer is the correct choice for their application. All elastomers tested and approved for the application should be clearly listed on the drawing. In addition, the drawing should clearly state that  the approved materials listed were tested to confirm their suitability for the application. All substitutes or new elastomers must be tested and approved by engineering prior to use.

Gallagher Fluid Seals is an authorized distributor for Parker. For more information about their products, including o-rings or their various compounds, contact Gallagher Fluid Seals today.

Compression Packing, Elastomers, Gallagher products, Gallagher Seals news, gasket, Mechanical Seals, O-rings

Gallagher Fluid Seals Announces e-Commerce Store

Better and faster access to the seals you need to keep your production running.

King of Prussia, PA. October 29, 2019 /News and Updates/ — Gallagher Fluid Seals (GFS) is excited to announce the launch of its e-commerce store, providing a brand new experience to shop for seals.

“It’s been a complete team effort,” says Chris Gallagher, CEO. “Our team has worked diligently over the past several months to prepare and deliver a state-of-the art e-commerce store for both new and returning customers.”

As the world’s economy has evolved to an online platform, GFS felt seal buying should be easier. Gone are the days of calling in and ordering a replacement seal – or sending an RFQ. This new online experience allows greater and faster access to the seals you need to keep your facility up-and-running.

“Maximizing the ease-of-purchase and visibility of fluid sealing products is imperative to the future of seal buying, and that’s why we are well-positioned to help our customers for years to come,” says Chris.

To start, Gallagher’s e-commerce store will focus on six main product categories:

  1. O-Rings
  2. Gaskets
  3. Sheet Material
  4. Expanded PTFE
  5. Compression Packing
  6. Mechanical Seals

In the coming months, the full product array will be added to shop.gallagherseals.com, providing even more fluid sealing options. Specialty products such as expansion joints, bearings & bushings, rotary seals, and more will be added.

We’re excited about this new chapter in Gallagher Fluid Seals’ history, and we hope you will join us in this journey to make your seal shopping experience easier and more transparent.

Shop our new e-commerce website here:

>> shop.gallagherseals.com

For larger orders or custom-engineered sealing needs, it’s suggested that customers complete a form on our e-commerce website requesting to speak with an engineer or member of the customer service team.

About Gallagher Fluid Seals, Inc.

For 60+ years, Gallagher Fluid Seals has taken pride in being the industry leader for all things seals. Not only was Gallagher the first North American seal distributor to achieve ISO 9001 certification, but year-after-year, GFS takes steps to maintain its status as the leading distributor for fluid sealing products: In January 2019, Gallagher made an additional company acquisition – this time acquiring Quality Seals out of Bethel, CT. This strategic acquisition has been great for customers. It has helped to bolster capabilities and expand product lines while simultaneously opening a custom engineering channel to Quality Seals’ existing customers.

Contact:
Kevin Patton
Marketing & Communications Analyst
610-277-8200

Elastomers, Parker Hannifin Seals

What does a good seal engineering drawing look like?

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.

Original content can be found on Parker’s Website and was written by Fred Fisher, technical sales engineer of the Engineered Materials Group.

seal drawingYou just spent 6 months testing, stretching, aging and exposing your new seal design to 12 different chemicals. Finally, you are done. So what does a good technical drawing for a seal include? For most companies, the drawing is simple. For an O-ring, we draw a generic circle and show an ID and width with some sort of material call out.

But now fast forward 20 years. Someone consults the drawing – how do they know the criteria you used to select the seal specified?

Just last week I asked my customer, who was having seal failure, about the issues on their engine sensor: “Was the original seal specified to be compatible with biodiesel?” The engineer consulted their drawing, but besides the generic circle, it lacked any background on what material compatibility was considered when the seal material was selected. The ASTM description on the drawing did not include a reference to or indicate compatibility with biodiesel.

Be specific with materials

Over time, the operating parameters of a system or product can change, so it is important to know what parameters were used for the original seal selection. The goal of the drawing is to assure that the engineers and procurement team understand what performance is required from the seal and why the specific elastomer was chosen.

So how do you make your drawing more valuable to your company?

  1. Define and list on your drawing all the operating conditions you anticipate the seal will see, such as temperature, pressure, and any other application specific operating conditions.
  2. Prepare a list of fluids as well as the concentrations of each fluid that your seal will be exposed to. Add these on your drawing. In addition, make sure you consider fluids that could come into contact with the seal indirectly through failure of other systems that are part of the product or even by cleaning the product.
  3. List the selected compound and manufacturer on the drawing. Clearly define what testing the compound was put through or what testing is required for approval.
  4. If you select a compound that was resistant to compression set, high temperatures or low temperatures, as well as explosive decompression, this should be clearly stated on the drawing.
  5. List clearly the industry standards the seal is required to meet, such as UL, FDA or NSF.

List fluid compatibility requirements

fluid compatabilityTime and time again, I see seal quality and performance failures when a new supplier is selected and the real requirements for the seal were either forgotten or not clearly defined. Clearly defining these parameters and making them transparent will allow your purchasing and technical team to understand, select, and evaluate the correct compound that meets your products sealing requirements.

Once you select a compound for your specific application, it is important to test and validate that the compound chosen is compatible with the fluids you are using. Parker can typically supply small compound samples for soak testing in the fluids your seal is exposed to. If you choose to list an alternate compound on your drawing, that compound must also be tested and validated for compatibility.

Remember when developing drawings standards, assure yourself that if someone consults a drawing that is 2 years old, 5 years old or even 20 years old, they will know the intent of the original seal design.

For more information about custom sealing solutions or information about Parker seals, please contact Gallagher’s engineering department.