How to Choose a Sealant?

2.2 Movement and Flexibility:

• Joint movement: Consider the expected movement in the joint (static, dynamic, or cyclic).
• Sealant elasticity: The sealant’s flexibility should match the joint movement to prevent cracking or failure.
• Basically, if the joints are anticipated to have great movements, due to whatever reasons like thermal or structural movements of the buildings, less flexible options like acrylic latex sealants or awning caulk should be avoided.

2.3. Environmental Conditions:

• Weather exposure: Sealants for exterior use must withstand UV rays, rain, wind, and temperature extremes. Budget-friendly acrylic latex sealants should always be avoided because they are mostly intended for indoor use only. If the exterior applications of sealants are applied in such a way that the sealant thickness is less than 6mm, or in a non-joint setting like sealing fasteners on roofing, avoid the use of organic sealants like Polyurethane sealants or even MS Polymer sealants. Neutral silicone sealants are always the best bet in terms of weathering.
• Chemical resistance: If the sealant will be exposed to chemicals, choose one with appropriate resistance. The problem is, there are too many types of chemicals available out there, and each sealant has different formulations that would react to a particular chemical differently. Therefore, a compatibility test is recommended if the sealing is mission critical.
• Temperature range: Consider the sealant’s performance at both high and low temperatures. Generally, Acrylic latex sealants withstand temperatures up to 80°C, MS Polymer sealants – up to 90°C, and silicone sealants – up to 150°C. Refer to TDS of the particular product to confirm.
• Water immersion: Most common sealants available on the market are not permanently water immersible (intermittent wet and dry is OK). Among them, silicone sealants stand the best chance of withstanding water immersion. However, it still depends on the type of adjacent substrates being bonded as the bonding line always fails on wet porous substrates.
• Wet environments with bad ventilations: where fungal growth is common, antifungal sealants are preferred, although they only withstand longer if there is always organic residue like soap foam left on the surface, with bad ventilation and wet conditions, which are perfect recipe of fungal growth.
• Traffic Abrasion: Is the joint located at pedestrian walkways that are subject to human traffic? Or at driveway, airport runway, or factory areas subject to vehicular traffic abrasion?  In short, sealants for traffic joints should have high hardness properties and great adhesion to the joint flanks, so it can live up to the challenge. However, no matter how good a sealant is, protecting the sealant with a cover is always recommended.
• Vibrations: Is the sealant joint subject to constant vibrations during its service life? For example, sealing joints in commercial vehicles (industrial manufacturing) requires a sealant with higher tensile strength.
• Low Emission: While it is a common requirement to use sealants with low VOC (volatile organic compounds) in green buildings, it is even more stringent these days that sealants need to exhibit low emissions characteristic in new green building standards, like LEED v4.1. Likewise, sealants used in semiconductor cleanrooms need to have extremely low emissions so as not to affect the manufacturing process, in compliance with the specific ISO Clean Room Classifications.
• Contact with Food / Drinking Water: Sealing a confectionery showcase, glass refrigerator, water dispenser, or even a steel water tank? There are specific tests and standards that can confirm the sealants are safe for use in such conditions – that they will not leach harmful materials into food or water when in contact.