Heat and Water Resistant Sealant
Heat resistant sealant can be used to fix cracks and joints around doors, windows and more. It bonds to almost any surface and won’t crack or peel.
The cured composition of the invention exhibited superior movement capability in combined water (absorbed) and heat conditions as compared to C1, a commercial one-component PU sealant, and C2, a commercial water-immersible PU sealant.
Sealing Cracks
A crack sealant is a type of caulk that helps prevent water leaks. It is typically used around bathtubs, basins, sinks, toilets, showers, and other surfaces where water can seep through a crack. It may also be used to seal gaps between concrete walls, joints, and other items. This type of sealant is designed to withstand heat, water, and cyclic movement.
The optimum choice of crack sealant depends on the anticipated movement in a structure. Cracks are a natural occurrence in concrete due to temperature fluctuations, which cause the concrete to expand and contract. To accommodate this movement, engineers will often place sawed or grooved control joints in the concrete. These control joints must be filled with a flexible crack sealant.
Laboratory evaluations of the adhesive strength of hot-poured sealants at low temperatures have found that the viscoelastic properties of the material play an important role in preventing adhesion failure (Li et al., 2017b). Two types of commercial water-immersible PU sealants, C1 and C2, were selected for the evaluation. Both of these sealants contain a silane adduct that reacts with the primary amino groups on the surface of the acrylate in order to enhance their ability to bind to a concrete substrate.
The test results showed that both commercial sealants were able to pass the modified ASTM C719 test, which requires a sealant to withstand six cycles of immersion in boiling and freezing water. However, the performance of MZ, a self-developed high-performance heat and water resistant sealant, was markedly superior to that of C1 with a primer applied. MZ exhibited perfect maintenance of adhesion, cohesion and elastic recovery after the first four immersion cycles, and its behavior was only slightly degraded after the sixth cycle.
Sealing Joints
When a joint is designed to accommodate movement the substrates need to be bonded together to form an effective seal. Selecting the right product is critical to the long term performance of the joint and must be based on input from the sealant manufacturer. This heat and water resistant sealant information includes the anticipated environmental strains (movement, temperature, light, water etc.) that the sealant will be exposed to.
The most important factor in determining the proper selection of a joint sealant is adhesion to the bonding surfaces. A determination of this can be made using ASTM test methods. A field test as well as a mock-up is preferred in order to ensure that the selected sealant will achieve the desired results.
Physical and chemical properties of a sealant such as modulus of elasticity, stress/strain recovery characteristics, tear strength and fatigue resistance are also important considerations. These factors must match up with the sealant’s anticipated movement capabilities and installed conditions.
The substrates to be bonded should be clean, dry and free of dew or frost. Generally, the bonding surface needs to be primed prior to applying a sealant. Choosing the correct primer is important and must be based on input from the manufacturer. Proper application of the sealant to the substrates is also critical to successful performance. Using a cartridge-operated gun makes this task easier. Immediately after application the surface should be smoothed with a BISON Multi Tool or with a finger dipped in soapy water. This prevents three-sided adhesion and allows the sealant to rehydrate in place.
Fire Protection
Fire-resistant sealants can be used in many different construction applications, including filling gaps around fire rated walls and cladding. They can also be applied to fire rated expansion joints and joints in firewalls and partitions. In addition, some can be used as fireplace sealants to prevent air leaks and smoke passage. These products are based on intumescent materials, which means that they swell up and char when exposed to heat, blocking the flow of fire and smoke through the gap.
Some fire resistant sealants are designed to also double as acoustic insulation, providing noise reduction properties as well. These are often single component water based acrylic products, with a fast expansion technology that fills voids and provides protection from fire, smoke and toxic gasses.
Regardless of the product, it is important to ensure that all surfaces are properly prepared prior to application. This includes removing any grease, dust and dirt and making sure that the area is free of moisture. Before applying the product, it is recommended to read the manual carefully and apply using a sealant gun with a blade. Care should be taken to protect the hands and eyes during application.
A range of colours are available, depending on the application. These products are generally easy to use, with simple instructions for application. It is important to check the product description for specific information, such as maximum temperature resistance and curing times.
Applications
In the construction industry, heat resistant sealant can be used to fill gaps in structures which during operation are exposed to high temperatures. These include stoves, fireplaces, chimneys and welds in masonry as well as elements of heating heat and water resistant sealant systems and pipelines supplying hot and cold water. Heat resistant sealants also can be used for sealing of joints in concrete walls and floors, doors in houses and buildings, as well as for insulating pipes.
During the development of this sealant, special attention has been paid to the movement capability of the product under combined combination of water (absorbed) and heat. In repeated ASTM tests comparing MZ with two commercial water-immersible products, C1 and C2, it was found that the invented PU sealant showed superior performance in this respect. In comparison to these products, MZ exhibited excellent overall performance and retained excellent tensile strength, hardness and elastic recovery after prolonged immersion in hot water.
This is mainly due to the fact that the carbodiimide groups in the invention consume the water molecules and prevent them from diffusing to the polyurethane chains, thus eliminating the formation of the water-swelling molecule. In addition, the –N-C-N– groups are gradually converted to the corresponding -OH functionalities during immersion in hot water, which counteracts the degradation of the sealant owing to prolonged combination of water and heat.