Foam Rubber Properties and Custom Gaskets
Foam rubber properties include compression set and stress relaxation. Learn what these properties are and why they matter for custom gaskets.
Foam rubber properties include compression set and stress relaxation. Learn what these properties are and why they matter for custom gaskets.
Learn how adhesive taping attaches rubber parts to plastic, metal, and glass surfaces – and why taped gaskets provide a strong, reliable alternative to mechanical fasteners such as bolts and screws. Then, download the Make It or Buy It? E-Book.
Rubber parts such as door seals, edge trim, and weather stripping can be attached to plastic, metal, or glass surfaces. Mechanical fasteners like screws and bolts are strong and reliable, but installation is time-consuming. The use of adhesive tapes can speed assembly, but taping also offers other important advantages. By understanding these benefits, and how high-strength adhesive tapes compare to mechanical fasteners, you can choose the best attachment method for your rubber parts. If taping is right for your sealing or insulation application, you can then decide which type of taping you need. (more…)
EPDM gasket fabrication supports environmental sealing and electrical insulation. Learn how Elasto Proxy custom fabricates EPDM profiles into finished EPDM rubber gaskets. Then, download the Sealing Essentials E-Book. EPDM gaskets…
Rubber extrusion is a manufacturing process that creates stock materials or profiles with a fixed cross-section such as a U-shaped channel. First, uncured elastomers are pushed or drawn through a specialized metal tool called a die. Later, the rubber compound is cured through vulcanization, a chemical conversion process that uses heat and sulfur to impart durability and improve mechanical properties.
Rubber extrusion is used with many different types of elastomers, and this rubber manufacturing method supports complex cross-sectional profiles with an excellent surface finish. Because extrusion mixes and blends the raw materials, the cured rubber offers consistent strength and a uniform appearance along the length of the profile. Standards from the Rubber Manufacturers Association (RMA) define part tolerances based on physical dimensions and an RMA class of high precision, precision, or commercial. (more…)
Hot splicing or vulcanization is a cost-effective joining technique for creating continuous seals or endless gaskets from cut lengths of rubber products. First, a heat-activated adhesive is applied to the ends of sponge or solid profiles. In addition to rectangular profiles, rubber products such as round cords, industrial tubing, and irregularly-shaped rubber profiles can be hot spliced, too.
Next, the ends of the profiles are pressed together and placed in a hot mold or vulcanizing press. The heat activates the rubber-based glue, and pressure from the mold or press creates a reliable, attractive joint for continuous sealing. Proper dwell time is important, and hot spliced gaskets should be stored under controlled conditions in warehouse environments according to standards such as DIN 776 or ISO 2230.
Military specifications for rubber gaskets are designed to ensure that elastomeric materials support the mission by meeting published performance requirements. Standards and specifications for the U.S. military are authorized by the Department of Defense (DOD), and used by defense contractors throughout North America. Tier 1 and Tier 2 suppliers are familiar with these standards, but may not fully understand how the details of a particular specification can affect purchasing and manufacturing decisions.
Official DOD definitions specify many different document types, but the format of each military standard generally begins with the letters “MIL”. For the defense supply chain, however, complying with what’s inside the standard is what matters. With rubber gaskets, buyers need to choose materials that meet or are tested to published requirements for properties such as hardness and oil-resistance. In addition, elastomeric gaskets for defense-related applications must be custom fabricated to exacting tolerances.
Let’s take a look at two military standards for rubber gaskets: MIL-R-900F and MIL-G-1149C. First, however, we’ll examine a related standard for non-metallic gasket materials.
Clyde Sharpe
General Manager of Elasto Proxy
Have you ever wondered why the military uses so many acronyms? Soldiers, sailors, airmen, and marines need to convey information quickly, accurately, and efficiently. Suppliers to the defense industry are also more likely to hear a term such as “MRAP” than the phrase “mine-resistant ambush-protected vehicle”. For defense contractors who want to do business with military buyers, mastering these acronyms can be learning a new language. The process may be challenging at times, but the rewards are worth it.
Like any specialized discipline, gasket design has its own language, too. For example, many rubber gaskets are made of synthetic elastomers with names such as Buna-N and EPDM. Published specifications such as ASTM D2000 use letters and numbers to “call out” the properties of vulcanized rubber in a highly-structured way. Units of measure such as durometer (hardness) are sometimes unfamiliar, so buyers and designers may need assistance in order to translate the language of rubber into project specifications.
Clyde Sharpe
General Manager at Elasto Proxy
Military machines like the MRAP are designed to project power while protecting personnel. With their V-shaped hulls and add-on armor, the mine resistant ambush protected (MRAP) vehicle can withstand IEDs, mines, RPG rounds, and small arms fire. Ballistic protection alone won’t keep armored vehicles on patrol, however. The MRAP is powered by a big diesel engine that runs hot and loud. Without engine bay insulation, heat and noise could put both the powerplant and military personnel at risk.
Clyde Sharpe
General Manager at Elasto Proxy
EMI gaskets made of particle-filled silicones are used with joints and seams in metal-to-metal interfaces. This EMI shielding conducts electricity and ensures conductivity even when there are discontinuities along metal surfaces. As we learned in Part 1 of this series, elastomeric shielding gaskets are filled with either metal- or metal-coated particles. These shielding materials combine the useful physical and chemical properties of silicone rubbers with reliable electrical conductivity and specific levels of resistance to electromagnetic interference (EMI).
In Part 2 of this series, we’ll examine how the custom fabrication of EMI gaskets supports shielding for military and defense applications. Accordingly, it’s important to note that product designers need these EMI gaskets in many different shapes and sizes. In addition to square gaskets and knife-edge profiles, examples include C, D, L, and M-shaped profiles. There are various ways to convert particle-filled silicones from sheets or rolls into specialized shapes, but water jet cutting offers advantages over methods such as die cutting.
Silicone rubber is a synthetic elastomer with useful physical and chemical properties over a wide range of temperatures. Silicones resist weathering, ultraviolet light, oxidation, moisture, and many chemicals. Polydimethylsiloxane (PDMS) compounds are also flexible, permeable, and non-irritating to human skin. With applications ranging from medical gaskets and oven seals to building expansion joints and lubricants, silicone rubbers are versatile materials.