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Elasto Proxy's Sealing Solutions Blog

Elasto Proxy's Sealing Solutions Blog is the place for conversation and discussion about the design and custom fabrication of rubber and plastic components. For nearly 25 years, our family-owned company has provided high-quality, low-volume seals to a variety of industries. Doug Sharpe, Elasto Proxy's co-founder, is a former president of the International Sealing Distribution Association (ISD), a not-for-profit trade association that enhances member success through information, education, and interaction. By blogging for CR4 in this same supportive and collaborative spirit, Doug and other members of the Elasto Proxy team will share our experiences with you.

Bulb Trim Seals: Three Things Engineers Need to Know

Posted October 30, 2017 5:46 PM by Doug Sharpe

Bulb trim seals are used with doors, hatches, and enclosures. They have two sections: the bulb and the retainer. The bulb section provides sealing and insulation under compressive force. The trim or retainer section presses onto a flange or substrate.

Elasto Proxy supplies many different types of industrial rubber products, but there are three things about bulb trim seals that engineers need to know.


The sections of a bulb trim seal are made from different materials. For outdoor applications, resistance to wind, weather, ozone, sunlight, and a range of service temperatures is especially important.

The bulb portion of the seal is usually made of EPDM sponge rubber or a thermoplastic elastomer (TPE).

  • EPDM provides excellent resistance to weather, ozone, aging, water, and steam. This synthetic rubber also remains flexible at low temperatures and is color stable.
  • TPEs are also weather-resistant, but are reusable and typically recyclable. They cost more, but are often available in custom colors and smaller lot sizes.

The retainer section of a bulb trim seal is usually made of PVC, a popular plastic that resists impact, abrasion, low temperatures, and kinking.

Note that each section of the seal isn’t just made of a different material. Each material has a durometer or hardness that the engineer needs to specify.

  • If the material is too hard, the seal is difficult to compress.
  • If the material is too soft, compression set may occur.

By working with Elasto Proxy, you can avoid these sealing problems.


Engineers also need to know that bulb trim seals have three measurements:

  • Bulb size
  • Gap or edge thickness
  • Minimum bend radius

Getting these measurements correct involves following these tips:

  • To determine the required bulb size, measure the distance between the door and the jam when the door is closed. Add between 25% and 50% to this measurement to account for compression.
  • To determine the gap or edge thickness for the retainer, measure the distance between the two “legs” or straight sections. Choose a bulb trim seal where the gap equals the flange or substrate.
  • To specify the minimum bend radius, don’t choose an angle that’s too great. Otherwise, kinking can cause valleys to form that allow the passage of water.


Most industrial rubber products are black, but engineers need to know that bulb trim seals can come in colors such as:

  • white
  • off-white
  • beige
  • tan

Many industrial rubber products are also flat and smooth; however, bulb trim seals can come with coarse, pebbly, or ribbed finishes.

Finally, remember these two optional features:

  • The retainer section seal can include an internal clip made of aluminum or steel. This clip promotes permanent gripping under conditions such as the opening and closing of doors.
  • The retainer portion of the seal may support the use of a hot-melt adhesive for fastening, and may have an outer coating made of vinyl to impart a textured finish.

To talk to Elasto Proxy about bulb trim seals for your application, please contact us.

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Rubber Gate Seal for Water Filtration System Lasts Longer, Resists Disinfection, Adds Business Value

Posted October 23, 2017 7:20 PM by Doug Sharpe

When a manufacturer of water filtration systems needed a rubber gate seal that would last longer and resist ultraviolet (UV) light, Elasto Proxy provided a value-added solution. This custom gasket doesn’t just resist exposure to water, contact with metal and concrete, and disinfection with UV light. The gate seal also supports ease-of-installation and is ready to ship from Elasto Proxy’s warehouse in Newmarket, Ontario.

The 60-durometer EPDM lip seal (J-seal) that Elasto Proxy provides attaches to the bottom of a metal gate used in water treatment facilities. This rubber seal is also compressed against hard concrete floors and exposed to a range of temperatures. UV disinfection kills waterborne microbes that can make people sick, but ultraviolet light can also degrade rubber materials. Without reliable sealing and strong bonding, gaskets like this can’t meet business or technical requirements.

To provide a complete sealing solution, Elasto Proxy leveraged its expertise in seal design, material selection, custom fabrication, warehousing, and logistics.

Design Assistance and Material Selection

Elasto Proxy’s first task was to analyze the design of the customer’s current seal, a large P-shaped profile made of natural rubber. At nearly 2-inches high and 4-inches wide, this gate seal was especially thick. To promote compression, the gasket had a hollow center yet still required a significant amount of force. The profile’s corners were probably joined with cold-bonding, a splicing method that’s better suited for gaskets that won’t be exposed to high temperatures or outdoor environments.

Next, Elasto Proxy’s technical team analyzed requirements from the U.S. Food and Drug Administration (FDA) and determined that natural rubber wasn’t required for this application. This was an important discovery since EPDM rubber offers greater resistance to UV light. The J-seal that Elasto Proxy recommended also provided the right hardness and shape to support compression resistance.

Custom Fabrication, Warehousing, and Logistics

After replacing the P-shaped profile with a lip seal and recommending EPDM instead of natural rubber, Elasto Proxy applied its custom fabrication expertise. To produce a pattern of bolt holes for attaching the rubber seal to a metal gate, Elasto Proxy used water jet cutting to make fine, fast, precise cuts. To produce strong bonds and support the lip seal’s large size, infrared (IR) splicing was used. Among its many advantages, IR splicing is faster than cold bonding and less expensive than molding.

Next, the custom rubber seals that Elasto Proxy crafted were subjected to rigorous in-house testing by the manufacturer of water filtration systems. Today, Elasto Proxy holds the customer’s seals in stock and ships them according to annual usage. Quick turnaround time meet the customer’s needs, and there are now over 50 other sizes that incorporate our custom-fabricated profile.

Find Your Sealing Solution

Do you have questions about rubber gate seals for water filtration systems? Would you like to learn how Elasto Proxy can solve your sealing challenges through better design, material selection, custom fabrication, and logistics? To get starts, contact us.

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Cold Bonding for Rubber Gaskets

Posted October 16, 2017 5:03 PM by Doug Sharpe

Cold bonding for rubber gaskets joins lengths of material without the use of heat. This bonding technique doesn’t require low-temperature conditions, but is called “cold” because no heat is applied to the gasket. By contrast, hot splicing requires either a conventional heat source or infrared (IR) light. Vulcanization and molded corners for rubber gaskets also involve heating gasket materials.

With cold bonding, an adhesive is applied to the ends of the lengths that will be joined together. Different types of bonding systems are available, including compounds that vary in terms of viscosity, chemistry, and material properties. Cold bonding for rubber gaskets can save time and eliminate tooling costs, but engineers need a complete understanding of this joining method before choosing glued gaskets.

How Cold Bonding Works

Cold bonding is a manual process that’s performed with a brush and adhesive or glue. First, production personnel prepare the surfaces of the rubber materials that will be joined. To promote optimum adhesion, some elastomers may need to be abraded. Degreasers, solvents, or other cleaning agents are sometimes used to remove dirt, oils, and other surface contaminants.

After the surfaces are wiped clean and dried carefully, the glue or adhesive is applied. Rubber bonding systems include low, medium, and high viscosity adhesives that come in cyanoacrylate, silicone, epoxy, and other formulas. Specific bonding products may be designed for elastomers such as nitrile, silicone, neoprene, or EPDM. Some glues crystallize when they contact water. All glues dry out over time.

Advantages and Disadvantages of Cold Bonding

Cold bonding is more expensive than film splicing, but this manual process combines speed with scalability. If you need a higher volume of glued gaskets, Elasto Proxy can allocate additional labor resources to your project. Our skilled production personnel understand how to create strong bonds and take pride in their craftsmanship.

At any manufacturing facility, capacity is inherently limited by the amount of equipment that’s available. Manual processes generally take longer, but adding enough labor to a project can yield higher throughputs during a unit of time such as a shift. Cold bonded gaskets won’t last as long, but choosing the right joining method means balancing requirements such as strong corners against production speed and cost.

Is Cold Bonding Right for Your Application?

Unlike molded corners for rubber gaskets, cold bonding doesn’t require dies. That’s an important consideration if you need low-volume quantities, especially for one-time production runs. Metal tooling can add significant costs to gasket fabrication – sometimes as much as tens of thousands of dollars. Unless your quantities are large enough, molded corners may be too expensive compared to cold bonding.

Determining whether cold bonding is right for your application isn’t just about understanding how the process works or how much it costs. Engineers need to analyze all the tradeoffs that are involved, especially compared to other available joining methods. By working closely with Elasto Proxy’s solutions providers, you can choose the bonding method that’s best for your gasketing application.

Gasket Bonding and Custom Fabrication

We hope you’ve enjoyed this three-part series about gasket bonding. If you’ve missed our other recent articles, we invite you to read about Hot Splicing and Vulcanizing for Rubber Gaskets and Molded Corners for Rubber Gaskets. Elasto Proxy is an experienced custom fabricator of industrial rubber products with capabilities that include design assistance, help with material selection, warehousing, and logistics.

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Molded Corners for Rubber Gaskets

Posted October 10, 2017 9:09 AM by Doug Sharpe

Molded corners for rubber gaskets are recommended for applications that require rounded joints, the ability to withstand stretching, or high cycle times. Molding is more expensive than hot splicing or vulcanization, but it’s the only way to create radisued corners. C-press injection molding, a bonding method for rubber gaskets, is ideal for low-to-medium volume quantities but suitable only for solid profiles.

By understanding how C-press injection molding works and the advantages that molded corners provide, engineers can make strong decisions about gasket fabrication. In this article, the second in a series from Elasto Proxy, we’ll continue our coverage of joining methods. Next week’s content, the last in our series, will examine cold bonding.

How C-Press Injection Molding Works

C-press injection molding refers to a joining technique that uses a machine with a heated barrel, two metal plates (i.e., the top and bottom halves of the mold), and tons of pressure. First, uncured rubber is heated and pushed through a barrel by a screw. This molten rubber flows into channels on the bottom plate or mold half. There, cut lengths of a solid profile are positioned so that they are parallel to each other.

After the molten rubber flows into this part of the mold, a moveable plate with additional cut lengths of rubber presses down on the bottom plate. In the top half of the mold, these cut lengths are positioned so that they’re perpendicular to the bottom halves. By assembling the two halves of the mold together, a bezel or picture-frame style gasket can be formed.

Next, hydraulic pressure is applied. The corners are formed, the top plate or mold half is removed, and cooling occurs. To speed gasket production, Elasto Proxy has three C-press molding machines at its headquarters near Montreal, Canada. Elasto Proxy’s Simpsonville, South Carolina (USA) facility also has bonding or joining capabilities for gasket fabrication.

For engineers, it’s important to understand that molded corners require tools made of machined metal. Depending on the finished gasket, the cost of a metal mold can be significant. Once a mold is made, however, Elasto Proxy can store it for you and use it repeatedly. With large jobs that require the use all of our C-press molding machines, your tooling costs are limited to the cost of the first mold.

Advantages of Molded Corners

Molding is the only way to achieve rounded corners for rubber gaskets. This bonding method is also recommended for gaskets with corners that will be subjected to pulling or stretching. Compared to corners that are hot spliced, rubber molding produces stronger joints for increased resistance to leaking. Molding is also recommended for bulbs with difficult shapes.

Custom gaskets with molded corners also provide advantages such as:

  • Reduced cycle times
  • Cost-effective processing
  • Support for a range of sizes

In addition, molded corners can enhance the appearance of custom rubber gaskets. Importantly, this joining method works with a variety of elastomers. At Elasto Proxy, these compounds include neoprene, EPDM, PVC, and Viton gaskets.

  • Molded neoprene gaskets provide good resistance to oil, petroleum, water, and weather.
  • Molded EPDM gaskets have excellent resistance to ozone, sunlight, oxygen, and severe weather.
  • Molded PVC gaskets are strong, lightweight, and inherently fire resistant.
  • Molded Viton gaskets provide fuel-resistance at extreme temperatures.

Elasto Proxy does not mold the corners for silicone gaskets and has not worked with thermoplastic elastomers (TPEs). Sponge profiles do not support C-press injection molding.

Are Molded Corners Right for Your Rubber Gaskets?

Would you like to learn more about molded corners for rubber gaskets? Elasto Proxy is ready to help. For more information about gasket fabrication, please contact us.

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Hot Splicing and Vulcanizing for Rubber Gaskets

Posted October 02, 2017 3:49 PM by Doug Sharpe

Hot splicing and vulcanizing for rubber gaskets are bonding techniques that use heat, pressure, and a film splice or uncured rubber to join the ends of profiles. Hot splicing uses thin polyethylene (PE) film and either a conventional heating source or infrared (IR) light. Vulcanization uses an uncured rubber compound, along with heat and pressure. Both hot splicing and vulcanization create chemical bonds at the molecular level.

For engineers, choosing a splicing method for rubber gaskets is an important manufacturing decision. By balancing costs against capabilities, you can get the sealing and insulation solutions that you really need. Traditional hot splicing, infrared or IR splicing, and vulcanization all have their advantages, but they also have their differences. In this article, the first in a series from Elasto Proxy, we’ll examine each of these bonding techniques in detail. Future articles will cover molded corners and cold bonding.

Hot Spliced Gaskets

Hot splicing generally provides better results than vulcanization. Traditional splicing takes longer than IR splicing, but both methods create strong, reliable bonds. The type of profile – sponge or solid – usually determines whether conventional splicing or IR splicing is recommended. The shape and size of the profile are important considerations, too. Some materials, such as silicone, support traditional hot splicing but not IR splicing.

Infrared splicing is a good choice for sponge rubber profiles because infrared light won’t burn the elastomer. Elasto Proxy’s IR splicer can also accommodate very large profiles and requires significantly less post-production manipulation such as trimming. Most film splices are 90°, but Elasto Proxy can also splice 45° miter cuts and endless gaskets. With rubber gaskets, the types of splices include butt, bevel, step, and corner.

  • Butt splices bond two ends of a seal with only limited stress at the splice.
  • Bevel splices are used in cross-sectional areas that don’t allow for butt splicing.
  • Step splices provide maximum bond strength and allow nominal deformation in a static seal.
  • Corner splices are also used in static applications, but when the joint is not under strain.

As a rule, film splicing requires clean, straight cuts. Elasto Proxy’s water jet cutting machine highlights our capabilities in this area. Unlike saw or guillotine cuts, water jet cutting doesn’t put pressure on the profile. By contrast, guillotine cutting creates an edge that’s difficult to bond. In addition to smooth cuts and clean edges, water jet cutting supports gasket features such as small-diameter holes.

Vulcanized Gaskets

Vulcanizing is a reliable, cost-effective process for joining sponge or solid profiles in many different shapes and materials. Applications include O-rings, tubing, and other products with a space for the free-flowing passage of air to the gasket. Vulcanized gaskets can be used in various applications, but this bonding or joining technique is best-suited for low volume quantities rather than higher volume production.

Compared to hot splicing, vulcanizing is more forgiving since the cuts don’t have to be as smooth and precise. With vulcanization, an uncured rubber compound flows into and fills any gaps while forming a strong bond between profile surfaces. This uncured compound is the same type of elastomer as the profile itself. First, the uncured rubber compound is applied to the length of profile. The ends are then pressed together and the joint is placed into a hot mold. As with hot splicing, cooling is required.

Hot Splicing and Vulcanizing for Rubber Gaskets

Elasto Proxy offer traditional hot splicing, infrared splicing, and vulcanizing for custom-fabricated gaskets that meet all of your sealing and insulation requirements. Next week, we’ll take a look at another joining or bonding technique – molded corners for finished gaskets. To learn more about how custom rubber gaskets are made and how we can help you, please contact us.

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