Sealing Technologies

Sealing Technologies Sealing solutions, also known as sealants (mastiks), have three fundamental functions: filling gaps between substrates, creating a barrier, and maintaining substrate adhesion and sealing properties. Sealing materials are formulated with an elastomer containing inert filler materials that provide elongation and flexibility characteristics, giving them a putty-like consistency. Adhesives and filler compounds used in construction, transportation, industrial, electronic, consumer and many other applications are based on state-of-the-art synthetic polymer technologies. However, long before this technology existed, similar materials were used for the same purpose, such as bitumen, to hold materials together and provide sealing. Now let us examine the most commonly used sealant technologies today.

1. Polymer-Based Sealants

These products generally contain polyester, polysulfide, polyamide, polyurethane and vinyl sealants that cure at ambient temperature, in anaerobic or thermal curing. Polymer filler compounds are ideal for moving or expansion joints that create permanent flexible seals. End users of sealing technologies use materials such as two-part epoxies and urethanes for general composite bonding, flexible urethanes and epoxies, hardened epoxies for durability and high strength, acrylics for bonding metals and plastics, and surface energy acrylics for bonding low polyolefins. The secret to excellent composite bonding is selecting the correct adhesive. It is recommended that end users or manufacturers requiring sealing technologies seek support from professionals for their desired specific applications. Fiber-reinforced polymer matrix composites use adhesive and sealing technologies in the manufacturing of parts or components for the automotive or automobile manufacturing, aerospace, military, marine and sports and entertainment industries.

2. Epoxy Sealants

For manufactured products requiring extreme toughness and durability, epoxy filler compounds are the best solution. Similar to epoxy adhesives, epoxy filler compounds consist of two-component systems containing a hardener and resin that are mixed before application. They cure at room temperature. Thermoset epoxies typically require additional heat to harden. Epoxies are among the few sealing materials with extraordinary adhesive properties. For this reason, they are used in different sectors such as aerospace, marine and automotive. Additionally, epoxies provide excellent electrical insulation, making them suitable for electronics. Today, specialty epoxies are available for high-performance coatings, encapsulants, adhesives and composites. Specialty epoxy resins offer significantly better performance properties than standard liquid epoxy resins, such as chemical resistance, cure rate, modulus, UV resistance and thermal performance. One example of such a specialty epoxy formulation includes low viscosity bisphenol a/f modified phenol epoxy resins with non-crystallizing modified BPA resin. In filament winding applications, they create an excellent substitute for high-purity BPA resins. Another specialty epoxy type is cycloaliphatic epoxy resin. With lower viscosity than standard BPA resin, it is resistant to UV rays. It is used as an excellent sealing technology for metal components. Modified BPA epoxy provides faster curing at all temperatures. It eliminates yellowing in slowly curing epoxies. For high-temperature applications, low melt viscosity and high functionality resin is available. Phenol epoxy resins have the lowest viscosity and formulations to prevent crystallization near the monomeric product. They are used in industrial floor coatings, secondary coatings of storage tanks and highly abrasive applications.

3. Silicone-Based Sealants

Manufacturers frequently prefer silicone-based filler compounds because of the strength, versatility and cost-effectiveness of this material. Generally having a lifespan of 10 to 20 years, these materials provide solutions for innovative manufacturing processes. They are generally found as acetoxy and neutral-cure silicone-based filler compounds. Acetoxy cure silicones derive their name from the release of acetic acid during hardening, which produces a strong vinegar-like odor. These silicones cure in the presence of atmospheric moisture, generally have very fast cure times and adhere better to many surfaces. However, due to the released acid, acetoxy cured silicones have a stronger odor than neutral cured silicones and the acid can have negative effects on certain sensitive electronic components. The acid can be corrosive even to certain substrates and metals. Applications include window and door frames, kitchens, countertop sealing applications, bathrooms and tubs. Neutral curing silicones are unique because some release a substance known as methyl ethyl ketoxime during curing while others release acetone. These substances are not corrosive, are thixotropic and make neutral curing silicones ideal for electronic applications. These silicones also emit a much fainter odor and although the cure time is longer than acetoxy cure silicones, they become excellent candidates for interior applications such as kitchen installations. Applications include roof coatings, industrial seals, HVAC, compressor pumps, cooling.

4. Acrylic Sealants

Acrylic sealant solutions are produced by catalytic reaction and can be cured by different methods. The shortest cure time is when acrylic sealants are cured thermally. Acrylic sealants are odorless, flexible and paintable with excellent adhesion properties, perfect for sealing window frames and doors.

5. Phenolic Sealants

A combination of formaldehyde and phenol that seals joints and provides effective bonding with resistance to heat and temperature fluctuations. Phenolic filler compounds are available in liquid, film and powder form and are used in the sealing and bonding of plywood, in the appliance industry and in building construction. References • https://roboticsandautomationnews.com/2020/05/22/5-sealing-technologies-commonly-used-by-manufacturerstoday/32395/ • https://www.chemical-concepts.com/blog/2018/12/whats-difference-acetoxy-vs-neutral-cure-silicones/ • Images: shutterstock.com / pixabay.com Translation and Compilation: B. Serhat Cengiz