Sealants are specialized adhesives that are used to fill gaps, joints or seams. They are typically formulated from synthetic elastomeric polymers. Typical applications for sealants include forming waterproof or weatherproof joints and seams, protecting surfaces from corrosion or staining, and providing insulation and sound dampening. As with adhesives, a variety of factors must be considered when selecting sealants for an application including substrates to be sealed, joint design, performance expectations and production requirements.
A wide range of sealants is available from leading manufacturers. Each product is formulated for a particular class of applications and/or environmental conditions. In addition, some are designed to be cured with certain types of equipment or under specific load/movement conditions. For instance, an automotive sealant must be cured at elevated temperatures or in a specific manner to maintain integrity and durability. Often, a surface-conditioning process or priming is required to make a substrate compatible with a sealant.
There are many different kinds of sealants in the market today, ranging from polyurethanes to silicones, chloroprenes and acrylics. The chemistry of a sealant formulation is based upon the type of polymer chosen for the product as well as other additives such as fillers, plasticizers, thixotropic agents and adhesion promoters. The additives in a sealant formulation are designed to provide specific properties such as movement tolerance, resistance to temperature extremes, humidity, UV radiation and abrasion. In addition, the formulations may contain other ingredients to improve properties such as bonding strength or flexibility.
The most common products manufactured by Sealant Manufacturers are polymer-based and include a broad range of polysulfides, butyls, vinyls and polyurethanes. These products are characterized by their ability to bond to a wide variety of materials including aluminium, galvanized and stainless steel, glass, concrete, natural stone, treated wood, ceramics and most plastics. Most polymer sealants are tolerant of moisture and can be cured in ambient, thermal or anaerobic curing modes.
Polymer sealants are also able to withstand movement and can be used for expansion joints, sanitary area sealing, underwater sealing and capping glazing applications. Some of these products also contain an anti-mould fungicide and are suitable for use in kitchens and bathrooms.
Some of the major sealants in the industry are offered by DowDuPont, Novagard Solutions and Sika. These products are manufactured from a variety of chemistries including RTV, heat cure and hot melt as well as foam silicones. They are used in various applications including automotive, PCB systems assembly, building & construction and industrial assembly.
Other chemistries produced by leading Sealant Manufacturers include acrylic latex, epoxy, butyl, urethane and polyurethane. These products are used for a variety of applications including door assembly, panel assembly and transportation body panel bonding as well as furniture and woodworking. Some chemistry is available in two-part systems which require the base and accelerator to be mixed before use. Equipment such as guns, mixers and spatulas are often required for the proper application of these sealants. Back up materials in the form of bond breaker tape and primers are also available to allow for cleanup and to prevent three face adhesion.